The son wants to comparative study of airfoil designs as a science fair
project and he (and I) need a little help.
His plan is to make blades out of balsa, put them on a small remote
controlled helo he got a few years ago, place helo on a scale (small enough
so the majority of the thrust doesn't fall on the scale) then see which
design gives the best lift.
He has found some plans for different designs but I think he could use
others. Any websites out there for this?
Also I have NO experience in working with wood models or caving and he has
even less. How would you suggest he goes about carving the foils? I was
thinking a dremal type tool would work but what kind of blade/head would be
needed?
My biggest question is how in the world do you make sure that the shape in
the wood is the shape you want?
Any and all help would be great and quickly because I'm sure he's going to
be asking me and I'd like to impress him on my vast knowledge of woodworking
and airfoil construction. ;)
In article <[email protected]>, no spam
<[email protected]> wrote:
> I was
> thinking a dremal type tool would work but what kind of blade/head would be
> needed?
A dremel on balsa wood? Save your time and just toss the balsa into a
wood chipper.
Try an X-acto knife.
> My biggest question is how in the world do you make sure that the shape
> in the wood is the shape you want?
<http://www.google.com/search?rls=en-us&q=carving+a+balsa+wood+propeller>
--
Help improve usenet. Kill-file Google Groups.
http://improve-usenet.org/
"Bob F" <[email protected]> wrote in message
news:[email protected]...
>
> "no spam" <[email protected]> wrote in message
> news:[email protected]...
>> The son wants to comparative study of airfoil designs as a science fair
>> project and he (and I) need a little help.
>>
>> His plan is to make blades out of balsa, put them on a small remote
>> controlled helo he got a few years ago, place helo on a scale (small
>> enough so the majority of the thrust doesn't fall on the scale) then see
>> which design gives the best lift.
>>
>> He has found some plans for different designs but I think he could use
>> others. Any websites out there for this?
>>
>> Also I have NO experience in working with wood models or caving and he
>> has even less. How would you suggest he goes about carving the foils? I
>> was thinking a dremal type tool would work but what kind of blade/head
>> would be needed?
>>
>> My biggest question is how in the world do you make sure that the shape
>> in the wood is the shape you want?
>>
>> Any and all help would be great and quickly because I'm sure he's going
>> to be asking me and I'd like to impress him on my vast knowledge of
>> woodworking and airfoil construction. ;)
>
> Hard foam could be a substitute for balsa. A nichrome wire cutter powered
> by a transformer of some sort would cut it nicely, and a guide could be
> cut from cardboard at each end for the shape. Extruded styrene from the
> building materials area of the hardware store would probably work well for
> this.
>
> Bob
Amen to that ....most of us aircraft mechanics learned that way on airfoils.
You will note that since you are using a helicopter that the stall line will
be different on
a synmetrical airfoil like actually used on most helicopters and supersonic
airplanes than on a asynmetrical like used on autogyros and subsonic
airplanes.The stall line actually walking off the airfoil more at large
attack angles.
Should be able to get airfoil profiles for you to use by googling that.
I would use the blue form with one coat of fiberglass(lightest cloth like in
an model shop) over that.
with feather lite to smooth it up.For hard points to bolt blades on you can
use hardwood dowels glassed in
the form,then drilled for the bolt.
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"Lew Hodgett" <[email protected]> wrote in message
news:[email protected]...
>
> "no spam" wrote:
>
>> The son wants to comparative study of airfoil designs as a science
> fair
>> project and he (and I) need a little help.
>
> <snip>
>
>> My biggest question is how in the world do you make sure that the
> shape in the
> > wood is the shape you want?
>
> You take me back to the days of my misspent youth where a lot of time
> was spent building stick balsa and tissue paper model airplanes.
>
> The same technology works for air foils.
>
> Use 1/8" sheet balsa to make profiles along the air foil.
>
> Lay out and cut to size with an Xacto knife.
>
> These profiles are glued to a spar, say 1/8 x 1/2 located in the
> middle of the profile on equal spaces.
>
> Form leading and trailing edges from balsa as required, then glue in
> place.
>
> Cover with tissue paper that has been glued in place, then stretched
> by sprinkling with water and allowing to shrink while drying.
>
> Finally, paint with model airplane dope and you have an airfoil.
>
> Tools needed:
>
> Xacto knife, model airplane glue, straight pins, sand paper and some
> paint brushes for models.
>
> Try to find an old time hobby shop and kibitz with some old farts, if
> you can.
>
> Have fun, both of you.
>
> Lew
On wood blades for a helo he is close with airplane spar idea.
But it is going to have to be tougher because of blade spin.
Some like like your old Hillers were solid wood with a spar.
Other like some of your first Bells were a spar with the spacers he
mentioned and sheet of thin
plywood (balsa sheets with grain in the direction of blade length in your
case) with fiberglass or urethene coat.
Hell..... Bell in the early days built a frame on the lines of his 47 in
model format with a plugin electric motor to
test his ideas.And various blades out of wood for his prototype
helicopter......used to have some old movies of that
in his driveway testing it out.Guess he was one of the original 60/90 series
model helicopter guys.
Wood blade like wood props are fragile compared to other materials........
Have done them for a Whistler autogyro out of solid balsa (basswood is best
for beginners more stable but less reponsive)
You need a razor plane and a long sanding block.....
You also need to add reenforcing plys on the top and bottom of the root
attached with medium cyanoarcrylate.
CA is used around the mounting holes for reenforcement as well.
Mount blades and sand ...heavy blade to balance.
After you got them balanced cover with MonoKote
Then final balance ...cover... light blade tip with a different color
covering.
On these 90series blades the travel adjustment was 5" max.vertical.
AT 4 degrees negative incident .
I take it outside to check it.... holding up the rotor mast in a 5 to 7mph
wind with a quick hand spin .
It should spool on up to about 700rpms and give you a 5 pound tug for lift
on 39" disk.
This is with asymetric blades.....roughly a 8-h-12 profile
A lot of helicopters use NACA0012 profiles(If your son has that one, he has
the most popular used on helicopters)
That outer 1/3 of the blade is giving the lift.
some modelers add a 10-15 degree twist just like you see on props to extend
the lift along the leading edge.
That would have the outer half of the blade giving lift.
Since the root is moving a lot slower than the tip at a given rpm.
You would need a jig and copying dremel to carve that one......
Beyond anything I have done,so far on wood model blades.........
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"Edwin Pawlowski" <[email protected]> wrote in message
news:jw4Yi.5805$Cc.2681@trndny09...
>
> "Kerry Montgomery" <[email protected]> wrote in message
>>> All the rigid board is extruded polystyrene.
>>> http://www.dow.com/styrofoam/na/res-us/products/
>>>
>>
>> Edwin,
>> Actually, Bayer makes rigid board polyurethane insulation:
>> http://tinyurl.com/2rytbj
>> but it's not going to be marked Styrofoam.
>> Kerry
>
>
> Correct, I was referring to the Dow products. Thee are plenty of other
> materials available.
And the toxic from polyurethane is cyanide......like you used to see used in
the spy movies.
I was refering to Dow blue polystyrene because of the extra density needed
for the blades
and the ability to hot wire.
Pvc and nylon does pretty well on the hardpoints if he doesn't like
hardwood.For the added compression strength
needed for bolts to attach the blades.Full size helicopters.... you also
have different metals used for hardpoints.
At the same time, I have used polyurethane,nylon , wood, and pvc in building
composite structures.
On models I have even used cotton/linen rags instead of fiberglass.
As well as honeycombs made out cardboard,tinfoil, fiberglass,and kelvar.
Each have advantages and disadvantages.
Both models and full size aircraft.....though most of my experience is
limited to rotorcraft and hovercraft.
>
>
>
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On Nov 5, 4:42 pm, "no spam" <[email protected]> wrote:
> The son wants to comparative study of airfoil designs as a science fair
> project and he (and I) need a little help.
>
> His plan is to make blades out of balsa, put them on a small remote
> controlled helo he got a few years ago, place helo on a scale (small enough
> so the majority of the thrust doesn't fall on the scale) then see which
> design gives the best lift.
>
> He has found some plans for different designs but I think he could use
> others. Any websites out there for this?
>
> Also I have NO experience in working with wood models or caving and he has
> even less. How would you suggest he goes about carving the foils? I was
> thinking a dremal type tool would work but what kind of blade/head would be
> needed?
Draw the airfoils on the ends of the wing blank, then connect them
with
an oversized sanding block, say, a 9 x 12" piece of flat plywood with
a
whole sheet of sandpaper spray glued on top. Lay the sanding block
on the bench grit side up and have at it. Make a couple of test
pieces
before carving the actual wings, just to get the hang of it.
As for a Dremel tool, 60 grit sandpaper will cut balsa faster and
more
accurately. Save the Dremel for what it's best at, cutting small
bolts or
reslotting gnarled screw heads.
This was basically the same trick I used to carve ribs for balsa
airplanes
30 years ago. Clamp or bolt a stack together and sand them all to
profile at the same time. This worked equally fine for straight or
tapered
wings or fuselages.
> My biggest question is how in the world do you make sure that the shape in
> the wood is the shape you want?
You can freehand draw the cambers close. Eccentric curves are among
the easiest to sketch. Sanding will get them fair.
> Any and all help would be great and quickly because I'm sure he's going to
> be asking me and I'd like to impress him on my vast knowledge of woodworking
> and airfoil construction. ;)
no spam wrote:
> The son wants to comparative study of airfoil designs as a science fair
> project and he (and I) need a little help.
I did something similar back in high school.
> His plan is to make blades out of balsa, put them on a small remote
> controlled helo he got a few years ago, place helo on a scale (small enough
> so the majority of the thrust doesn't fall on the scale) then see which
> design gives the best lift.
My technique was to build a wind tunnel using a standard house fan and
simply put the wing on a post stuck through a hole in the bottom,
resting on a digital scale. You can then graph angle of attack vs lift
for each airfoil type.
A better technique would be to hang the wing from some thread front and
back. This would allow you to graph angle of attack vs both lift and
drag for each airfoil type.
If you want to use the scale, you could flip it around so that the force
is downwards. This would solve the problem of the helicopter flying
away, and would also mean that the wind produced by the blades would be
going up, and thus not affecting the scale nearly as much.
> He has found some plans for different designs but I think he could use
> others. Any websites out there for this?
There are some at:
http://www.gliders.dk/airfoils.htm
The Kline-Fogleman airfoil is kind of interesting. It almost looks like
it has a chunk taken out of it.
> Also I have NO experience in working with wood models or caving and he has
> even less. How would you suggest he goes about carving the foils?
A knife works fine, with sandpaper to finish. If you know someone with
a tablesaw you could kerf it at intervals to give you a baseline. A
bandsaw would allow you to hog off most of the excess.
> My biggest question is how in the world do you make sure that the shape in
> the wood is the shape you want?
Kerfing as mentioned above helps. Otherwise draw the shape on the ends,
cut away everything that isn't the shape.
Chris
"no spam" wrote:
> The son wants to comparative study of airfoil designs as a science
fair
> project and he (and I) need a little help.
<snip>
> My biggest question is how in the world do you make sure that the
shape in the
> wood is the shape you want?
You take me back to the days of my misspent youth where a lot of time
was spent building stick balsa and tissue paper model airplanes.
The same technology works for air foils.
Use 1/8" sheet balsa to make profiles along the air foil.
Lay out and cut to size with an Xacto knife.
These profiles are glued to a spar, say 1/8 x 1/2 located in the
middle of the profile on equal spaces.
Form leading and trailing edges from balsa as required, then glue in
place.
Cover with tissue paper that has been glued in place, then stretched
by sprinkling with water and allowing to shrink while drying.
Finally, paint with model airplane dope and you have an airfoil.
Tools needed:
Xacto knife, model airplane glue, straight pins, sand paper and some
paint brushes for models.
Try to find an old time hobby shop and kibitz with some old farts, if
you can.
Have fun, both of you.
Lew
"J. Clarke" <[email protected]> wrote in message
news:[email protected]...
> no spam wrote:
>> The son wants to comparative study of airfoil designs as a science
>> fair project and he (and I) need a little help.
>>
>> His plan is to make blades out of balsa, put them on a small remote
>> controlled helo he got a few years ago, place helo on a scale (small
>> enough so the majority of the thrust doesn't fall on the scale) then
>> see which design gives the best lift.
>>
>> He has found some plans for different designs but I think he could
>> use
>> others. Any websites out there for this?
>
> The Bible on wing sections is "Theory of Wing Sections" by Abbot & von
> Doenhoff. 15 bucks from Amazon.
>
>> Also I have NO experience in working with wood models or caving and
>> he has even less. How would you suggest he goes about carving the
>> foils? I was thinking a dremal type tool would work but what kind
>> of
>> blade/head would be needed?
>
> Knife, maybe a cabinet scraper. I'm not going to try to describe a
> sanding spline but if you google that term you should get some good
> descriptions.
>
>> My biggest question is how in the world do you make sure that the
>> shape in the wood is the shape you want?
>
> Make a template or set of templates out of cardboard or brass or
> aluminum or thin plywood or whatever else floats your boat--when the
> wing matches the templates you've got it right,.
>
>> Any and all help would be great and quickly because I'm sure he's
>> going to be asking me and I'd like to impress him on my vast
>> knowledge of woodworking and airfoil construction. ;)
>
> --
> --
Styrofoam (house insulation) and a hot knife might work well. For the hot
knife, you can use a couple of feet of steel wire (guitar string; can't
remember which one, but just a single wire) and an auto battery charger. If
he makes a couple of templates (cardboard works fine) in the shape of the
airfoil he wants, then sticks them to each end of a block of Styrofoam, then
hold the wire against both templates at the same time as he moves it around
the templates, he can make smooth, light weight airfoil sections.
Kerry
{snip}
> My technique was to build a wind tunnel using a standard house fan and
> simply put the wing on a post stuck through a hole in the bottom, resting
> on a digital scale. You can then graph angle of attack vs lift for each
> airfoil type.
>
>
> If you want to use the scale, you could flip it around so that the force
> is downwards. This would solve the problem of the helicopter flying away,
> and would also mean that the wind produced by the blades would be going
> up, and thus not affecting the scale nearly as much.
> {snip}
OT reply:
Just remember watching an old cable TV show about wind-tunnel and aircraft
design---AKA late 1930's
The engineers mounted the model wing airfoil design upside down. Attached
thin wires to a weight scale above (zeroed out for gravity and mass of
model). As wind tunnel air moved across inverted airfoil, the forces would
want to move the wing down, thus registering a greater weight of the wing on
the large dial of the scale.
For the 'suits' in management, they had to turn the camera upside down when
they filmed the wind tunnel results because any movement of the model would
then see on the film as the wing moving "UP". Mustn't upset the thinking
of the 'suits' you know.
Phil
"J. Clarke" <[email protected]> wrote in message
news:[email protected]...
> Kerry Montgomery wrote:
>> "J. Clarke" <[email protected]> wrote in message
>> news:[email protected]...
>>> no spam wrote:
>>>> The son wants to comparative study of airfoil designs as a science
>>>> fair project and he (and I) need a little help.
>>>>
>>>> His plan is to make blades out of balsa, put them on a small
>>>> remote
>>>> controlled helo he got a few years ago, place helo on a scale
>>>> (small
>>>> enough so the majority of the thrust doesn't fall on the scale)
>>>> then
>>>> see which design gives the best lift.
>>>>
>>>> He has found some plans for different designs but I think he could
>>>> use
>>>> others. Any websites out there for this?
>>>
>>> The Bible on wing sections is "Theory of Wing Sections" by Abbot &
>>> von Doenhoff. 15 bucks from Amazon.
>>>
>>>> Also I have NO experience in working with wood models or caving
>>>> and
>>>> he has even less. How would you suggest he goes about carving the
>>>> foils? I was thinking a dremal type tool would work but what kind
>>>> of
>>>> blade/head would be needed?
>>>
>>> Knife, maybe a cabinet scraper. I'm not going to try to describe a
>>> sanding spline but if you google that term you should get some good
>>> descriptions.
>>>
>>>> My biggest question is how in the world do you make sure that the
>>>> shape in the wood is the shape you want?
>>>
>>> Make a template or set of templates out of cardboard or brass or
>>> aluminum or thin plywood or whatever else floats your boat--when
>>> the
>>> wing matches the templates you've got it right,.
>>>
>>>> Any and all help would be great and quickly because I'm sure he's
>>>> going to be asking me and I'd like to impress him on my vast
>>>> knowledge of woodworking and airfoil construction. ;)
>>>
>>> --
>>> --
>>
>> Styrofoam (house insulation) and a hot knife might work well. For
>> the
>> hot knife, you can use a couple of feet of steel wire (guitar
>> string;
>> can't remember which one, but just a single wire) and an auto
>> battery
>> charger. If he makes a couple of templates (cardboard works fine) in
>> the shape of the airfoil he wants, then sticks them to each end of a
>> block of Styrofoam, then hold the wire against both templates at the
>> same time as he moves it around the templates, he can make smooth,
>> light weight airfoil sections.
>
> Careful with the selection of foam though--the beaded stuff won't cut
> smoothly that way and polyurethane gives off toxic vapors when
> hot-wired. If you're got non-beade polystyrene though the technique
> works a treat--that's basically the procedure that Burt Rutan
> specified for cutting the wing cores for the VariEze and LongEze.
>
> --
John,
Yep, that's why I suggested Styrofoam (house insulation).
Kerry
"J. Clarke" <[email protected]> wrote in message
news:[email protected]...
> Kerry Montgomery wrote:
>> "J. Clarke" <[email protected]> wrote in message
>> news:[email protected]...
>>> Kerry Montgomery wrote:
>>>> "J. Clarke" <[email protected]> wrote in message
>>>> news:[email protected]...
>>>>> no spam wrote:
>>>>>> The son wants to comparative study of airfoil designs as a
>>>>>> science
>>>>>> fair project and he (and I) need a little help.
>>>>>>
>>>>>> His plan is to make blades out of balsa, put them on a small
>>>>>> remote
>>>>>> controlled helo he got a few years ago, place helo on a scale
>>>>>> (small
>>>>>> enough so the majority of the thrust doesn't fall on the scale)
>>>>>> then
>>>>>> see which design gives the best lift.
>>>>>>
>>>>>> He has found some plans for different designs but I think he
>>>>>> could
>>>>>> use
>>>>>> others. Any websites out there for this?
>>>>>
>>>>> The Bible on wing sections is "Theory of Wing Sections" by Abbot
>>>>> &
>>>>> von Doenhoff. 15 bucks from Amazon.
>>>>>
>>>>>> Also I have NO experience in working with wood models or caving
>>>>>> and
>>>>>> he has even less. How would you suggest he goes about carving
>>>>>> the
>>>>>> foils? I was thinking a dremal type tool would work but what
>>>>>> kind
>>>>>> of
>>>>>> blade/head would be needed?
>>>>>
>>>>> Knife, maybe a cabinet scraper. I'm not going to try to describe
>>>>> a
>>>>> sanding spline but if you google that term you should get some
>>>>> good
>>>>> descriptions.
>>>>>
>>>>>> My biggest question is how in the world do you make sure that
>>>>>> the
>>>>>> shape in the wood is the shape you want?
>>>>>
>>>>> Make a template or set of templates out of cardboard or brass or
>>>>> aluminum or thin plywood or whatever else floats your boat--when
>>>>> the
>>>>> wing matches the templates you've got it right,.
>>>>>
>>>>>> Any and all help would be great and quickly because I'm sure
>>>>>> he's
>>>>>> going to be asking me and I'd like to impress him on my vast
>>>>>> knowledge of woodworking and airfoil construction. ;)
>>>>>
>>>>> --
>>>>> --
>>>>
>>>> Styrofoam (house insulation) and a hot knife might work well. For
>>>> the
>>>> hot knife, you can use a couple of feet of steel wire (guitar
>>>> string;
>>>> can't remember which one, but just a single wire) and an auto
>>>> battery
>>>> charger. If he makes a couple of templates (cardboard works fine)
>>>> in
>>>> the shape of the airfoil he wants, then sticks them to each end of
>>>> a
>>>> block of Styrofoam, then hold the wire against both templates at
>>>> the
>>>> same time as he moves it around the templates, he can make smooth,
>>>> light weight airfoil sections.
>>>
>>> Careful with the selection of foam though--the beaded stuff won't
>>> cut
>>> smoothly that way and polyurethane gives off toxic vapors when
>>> hot-wired. If you're got non-beade polystyrene though the
>>> technique
>>> works a treat--that's basically the procedure that Burt Rutan
>>> specified for cutting the wing cores for the VariEze and LongEze.
>>>
>>> --
>>
>> John,
>> Yep, that's why I suggested Styrofoam (house insulation).
>
> Styrofoam is a brand name for a variety of products, some of which can
> be hot-wired safely and others that can't. The blue Styrofoam at the
> local Home Depot is polyurethane, not styrene.
>
> Read the label, know what it's made out of, don't just assume because
> it's "house insulation" that it's safe to hot-wire.
>
> --
> --
John,
I agree that reading the label is very important - polyurethane does give
off toxic fumes. But, from Dow's website, when they refer to Styrofoam they
say "Styrofoam rigid foam insulation" or "Styrofoam extruded polystyrene
insulation". And the sheet of blue Styrofoam I'm looking at is marked
"Extruded polystyrene insulation" as have been all other sheets of blue
rigid Styrofoam I've ever seen, including at Home Depot. Can't remember if
this particular sheet came from Home Depot. There might be blue rigid foam
insulation at Home Depot that is polyurethane, but I doubt that it's also
Styrofoam.
Kerry
"Edwin Pawlowski" <[email protected]> wrote in message
news:id4Yi.7447$%n.1981@trndny07...
>
> "J. Clarke" <[email protected]> wrote in message
>>
>> Styrofoam is a brand name for a variety of products, some of which can
>> be hot-wired safely and others that can't. The blue Styrofoam at the
>> local Home Depot is polyurethane, not styrene.
>>
>> Read the label, know what it's made out of, don't just assume because
>> it's "house insulation" that it's safe to hot-wire.
>>
>
> All the rigid board is extruded polystyrene.
> http://www.dow.com/styrofoam/na/res-us/products/
>
Edwin,
Actually, Bayer makes rigid board polyurethane insulation:
http://tinyurl.com/2rytbj
but it's not going to be marked Styrofoam.
Kerry
"J. Clarke" <[email protected]> wrote in message
news:[email protected]...
> Kerry Montgomery wrote:
>> "J. Clarke" <[email protected]> wrote in message
>> news:[email protected]...
>>> Kerry Montgomery wrote:
>>>> "J. Clarke" <[email protected]> wrote in message
>>>> news:[email protected]...
>>>>> Kerry Montgomery wrote:
>>>>>> "J. Clarke" <[email protected]> wrote in message
>>>>>> news:[email protected]...
>>>>>>> no spam wrote:
>>>>>>>> The son wants to comparative study of airfoil designs as a
>>>>>>>> science
>>>>>>>> fair project and he (and I) need a little help.
>>>>>>>>
>>>>>>>> His plan is to make blades out of balsa, put them on a small
>>>>>>>> remote
>>>>>>>> controlled helo he got a few years ago, place helo on a scale
>>>>>>>> (small
>>>>>>>> enough so the majority of the thrust doesn't fall on the
>>>>>>>> scale)
>>>>>>>> then
>>>>>>>> see which design gives the best lift.
>>>>>>>>
>>>>>>>> He has found some plans for different designs but I think he
>>>>>>>> could
>>>>>>>> use
>>>>>>>> others. Any websites out there for this?
>>>>>>>
>>>>>>> The Bible on wing sections is "Theory of Wing Sections" by
>>>>>>> Abbot
>>>>>>> &
>>>>>>> von Doenhoff. 15 bucks from Amazon.
>>>>>>>
>>>>>>>> Also I have NO experience in working with wood models or
>>>>>>>> caving
>>>>>>>> and
>>>>>>>> he has even less. How would you suggest he goes about carving
>>>>>>>> the
>>>>>>>> foils? I was thinking a dremal type tool would work but what
>>>>>>>> kind
>>>>>>>> of
>>>>>>>> blade/head would be needed?
>>>>>>>
>>>>>>> Knife, maybe a cabinet scraper. I'm not going to try to
>>>>>>> describe
>>>>>>> a
>>>>>>> sanding spline but if you google that term you should get some
>>>>>>> good
>>>>>>> descriptions.
>>>>>>>
>>>>>>>> My biggest question is how in the world do you make sure that
>>>>>>>> the
>>>>>>>> shape in the wood is the shape you want?
>>>>>>>
>>>>>>> Make a template or set of templates out of cardboard or brass
>>>>>>> or
>>>>>>> aluminum or thin plywood or whatever else floats your
>>>>>>> boat--when
>>>>>>> the
>>>>>>> wing matches the templates you've got it right,.
>>>>>>>
>>>>>>>> Any and all help would be great and quickly because I'm sure
>>>>>>>> he's
>>>>>>>> going to be asking me and I'd like to impress him on my vast
>>>>>>>> knowledge of woodworking and airfoil construction. ;)
>>>>>>>
>>>>>>> --
>>>>>>> --
>>>>>>
>>>>>> Styrofoam (house insulation) and a hot knife might work well.
>>>>>> For
>>>>>> the
>>>>>> hot knife, you can use a couple of feet of steel wire (guitar
>>>>>> string;
>>>>>> can't remember which one, but just a single wire) and an auto
>>>>>> battery
>>>>>> charger. If he makes a couple of templates (cardboard works
>>>>>> fine)
>>>>>> in
>>>>>> the shape of the airfoil he wants, then sticks them to each end
>>>>>> of
>>>>>> a
>>>>>> block of Styrofoam, then hold the wire against both templates at
>>>>>> the
>>>>>> same time as he moves it around the templates, he can make
>>>>>> smooth,
>>>>>> light weight airfoil sections.
>>>>>
>>>>> Careful with the selection of foam though--the beaded stuff won't
>>>>> cut
>>>>> smoothly that way and polyurethane gives off toxic vapors when
>>>>> hot-wired. If you're got non-beade polystyrene though the
>>>>> technique
>>>>> works a treat--that's basically the procedure that Burt Rutan
>>>>> specified for cutting the wing cores for the VariEze and LongEze.
>>>>>
>>>>> --
>>>>
>>>> John,
>>>> Yep, that's why I suggested Styrofoam (house insulation).
>>>
>>> Styrofoam is a brand name for a variety of products, some of which
>>> can be hot-wired safely and others that can't. The blue Styrofoam
>>> at the local Home Depot is polyurethane, not styrene.
>>>
>>> Read the label, know what it's made out of, don't just assume
>>> because
>>> it's "house insulation" that it's safe to hot-wire.
>>>
>>> --
>>> --
>> John,
>> I agree that reading the label is very important - polyurethane does
>> give off toxic fumes. But, from Dow's website, when they refer to
>> Styrofoam they say "Styrofoam rigid foam insulation" or "Styrofoam
>> extruded polystyrene insulation". And the sheet of blue Styrofoam
>> I'm
>> looking at is marked "Extruded polystyrene insulation" as have been
>> all other sheets of blue rigid Styrofoam I've ever seen, including
>> at
>> Home Depot. Can't remember if this particular sheet came from Home
>> Depot. There might be blue rigid foam insulation at Home Depot that
>> is polyurethane, but I doubt that it's also Styrofoam.
>
> Dow Corning TUFF-R.
>
> I don't understand why you're so resistant to the notion of specifying
> the foam by chemistry, which is on the label on any foam sold
> commercially, instead of by the intended use "house insulation" or the
> brand "Styrofoam".
>
> --
John,
Not resistant at all to specifying foam by chemistry, but the brand
Styrofoam is a perfectly adequate way to specify Dow brand rigid Styrofoam,
which is what I suggested to the OP as a material to investigate.
The only TUFF-R that I know of is insulation clad on both sides; don't
remember what color the core is, but it's not labeled Styrofoam. And wanted
to correct any misconception that you may have caused by saying that there
was "...blue Styrofoam at the local Home Depot is polyurethane, not
styrene.", as there isn't any such thing.
Kerry
"Arnold Walker" <[email protected]> wrote in message
news:[email protected]...
> I would use the blue form with one coat of fiberglass(lightest cloth like in
> an model shop) over that.
> with feather lite to smooth it up.
But don't use polystyrene resin - it will dissolve the styrene foam - us epoxy.
Bob
Chris Friesen wrote:
> no spam wrote:
>> The son wants to comparative study of airfoil designs as a science
>> fair project and he (and I) need a little help.
>
> I did something similar back in high school.
>
>> His plan is to make blades out of balsa, put them on a small remote
>> controlled helo he got a few years ago, place helo on a scale (small
>> enough so the majority of the thrust doesn't fall on the scale) then
>> see which design gives the best lift.
>
> My technique was to build a wind tunnel using a standard house fan and
> simply put the wing on a post stuck through a hole in the bottom,
> resting on a digital scale. You can then graph angle of attack vs lift
> for each airfoil type.
>
> A better technique would be to hang the wing from some thread front and
> back. This would allow you to graph angle of attack vs both lift and
> drag for each airfoil type.
>
> If you want to use the scale, you could flip it around so that the force
> is downwards. This would solve the problem of the helicopter flying
> away, and would also mean that the wind produced by the blades would be
> going up, and thus not affecting the scale nearly as much.
>
>> He has found some plans for different designs but I think he could use
>> others. Any websites out there for this?
>
> There are some at:
> http://www.gliders.dk/airfoils.htm
>
> The Kline-Fogleman airfoil is kind of interesting. It almost looks like
> it has a chunk taken out of it.
>
>> Also I have NO experience in working with wood models or caving and he
>> has even less. How would you suggest he goes about carving the foils?
>
> A knife works fine, with sandpaper to finish. If you know someone with
> a tablesaw you could kerf it at intervals to give you a baseline. A
> bandsaw would allow you to hog off most of the excess.
>
>> My biggest question is how in the world do you make sure that the
>> shape in the wood is the shape you want?
>
> Kerfing as mentioned above helps. Otherwise draw the shape on the ends,
> cut away everything that isn't the shape.
>
> Chris
Go with the wind tunnel. Mounting new blades on a model helicopter
isn't a repeatable process. Changing blades will change the load on the
engine, causing it to run faster or slower, createing more or less lift.
Just changing the size or angle of attack of the rotor blades, while
keeping the airfoil the same will change the performance of the
helicopter.
Wind tunnel doesn't have to be very long. A square or rectangular
cross section works fine and is easier to make than a circular cross
section. Have the fan suck air out of the wind tunnel rather than blow
into it. The fan blades make the air turbulent which reduces lift and
adds vibration to make your instrument readings jiggle.
Make one side of the wind tunnel clear plastic so you can watch the
action. Arrange a protractor some how to let you measure (and set)
angle of attack. Angle of attack is very important, a change of a few
degrees will change the measured lift greatly.
One way of measuring lift might be to make a beam balance scale, the
airfoil under test (pointed down) goes onto one arm of the balance, and
you add weights to the other arm until the airfoil balances.
I'd go with balsa wood 'cause it's light and easy to carve to shape.
If the kid is new to carving, make sure he cuts AWAY from the
fingers holding the wood. You can get more consistant results by making
templates of the desired air foil out of file folder stock and using
them to check the shape as carving progresses. Surface finish affects
performance. Couple of coats of shellac, sand between coats, will
increase performance.
A really sophisticated tunnel would measure drag as well as lift, the
true measure of airfoil performance is the lift/drag ratio. The ideal
airfoil would create pure lift, no drag. Practical airfoils don't do
that well.
You might check with the boy and make sure that he really wants to do
a wind tunnel as opposed to flying the helicopter. He could do a
science project by measuring the performance of the helicopter, best
altitude, speed, range, payload, fuel consumption. Make the
measurements on a hot day, a cold day, a high pressure day, and a low
pressure day. See if temperature or barometric pressure makes a
measureable change in performance.
David Starr
Hi MB;
MB <[email protected]> wrote:
> Here's a wind tunnel made from some planks of wood, a fan, a hacksaw
> blade and some bicycle spokes. If it was good enuff for these guys...
>
> http://www.wrightflyer.org/WindTunnel/testing1.html
Very cool picture.
This is a replica of the original lost to history.
Some say the true invention of the Wright Bros. was
their wind tunnel which allowed them to make very
accurate measurements. They corrected the lift tables
of Lilienthal.
http://www.first-to-fly.com/History/Wright%20Story/tunnel.htm
The measurements were so accurate because they used a
kind of force balance that compared each reading with
standard unit flat drag surfaces in the same air flow.
This balance scheme did not require difficult to
calibrate force scales. Calibration was mostly done
by accurately cutting and measuring the standard flat
drag surfaces.
Air velocity in the wind tunnel was hard to measure
accurately. The drag balance devices were insensitive
to small errors in air velocity.
These guys were geniuses.
Duane
--
Home of the $35 Solar Tracker Receiver
http://www.redrok.com/led3xassm.htm [*]
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"no spam" <[email protected]> wrote in message
news:[email protected]...
> The son wants to comparative study of airfoil designs as a science fair
> project and he (and I) need a little help.
>
> His plan is to make blades out of balsa, put them on a small remote
> controlled helo he got a few years ago, place helo on a scale (small
> enough so the majority of the thrust doesn't fall on the scale) then see
> which design gives the best lift.
>
> He has found some plans for different designs but I think he could use
> others. Any websites out there for this?
How big are the blades? I'm not sure that the helo is the best way to
demonstrate the lift compared to a fixed wing in a makeshift wind tunnel.
There are a few ways to build wings. Spar and ribs are the traditional
method, but you can also hot wire foam board, add a spar and cover it with
Monokote, an iron on covering. http://www.monokote.com/
I'd do a comparison of at least three styles of airfoil, you can see some
profiles here
http://www.allstar.fiu.edu/aerojava/Wing31.htm
"J. Clarke" <[email protected]> wrote in message
news:[email protected]...
> If you had said "Styrofoam _brand_ blue insulating foam but make sure
> that it's really Styrofoam brand and that it's really polystyrene" I
> wouldn't have had any problem with what you said, but walking into a
> store and asking for "styrofoam house insulation" is just too likely
> to get the wrong stuff.
Doesn't the word "Styrofoam" imply polystyrene?
All the urethane foam I'm used has been brown or tan in color.
Bob
"J. Clarke" <[email protected]> wrote in message
>> All the rigid board is extruded polystyrene.
>> http://www.dow.com/styrofoam/na/res-us/products/
>
> I give up. I tried. If the kid ends up gassing himself on your head
> be it.
>
In 1970 I started working for a company that molded foam and the sister
company made model airplane wings from foam. I've been in the industry for
the past 37 years. I've built many model airplanes that included foam. I've
built hot wire cutters. I insulated my house with eps foam. I'd not
suggest anything that is harmful.
I can't help you with the design as I'm clueless when it comes to much other
than drilling holes...
But I can tell you that asking the same question in a model airplane group
may get you better results than anywhere else. Those folks are sometimes
beyond fanatical about their knowledge of such things.
Regards,
Joe Agro, Jr.
(800) 871-5022
01.908.542.0244
Automatic / Pneumatic Drills: http://www.AutoDrill.com
Multiple Spindle Drills: http://www.Multi-Drill.com
V8013-R
"no spam" <[email protected]> wrote in message
news:[email protected]...
> The son wants to comparative study of airfoil designs as a science fair
> project and he (and I) need a little help.
>
> His plan is to make blades out of balsa, put them on a small remote
> controlled helo he got a few years ago, place helo on a scale (small
> enough so the majority of the thrust doesn't fall on the scale) then see
> which design gives the best lift.
>
> He has found some plans for different designs but I think he could use
> others. Any websites out there for this?
>
> Also I have NO experience in working with wood models or caving and he has
> even less. How would you suggest he goes about carving the foils? I was
> thinking a dremal type tool would work but what kind of blade/head would
> be needed?
>
> My biggest question is how in the world do you make sure that the shape in
> the wood is the shape you want?
>
> Any and all help would be great and quickly because I'm sure he's going to
> be asking me and I'd like to impress him on my vast knowledge of
> woodworking and airfoil construction. ;)
>
Kerry Montgomery wrote:
>
> John,
> Yep, that's why I suggested Styrofoam (house insulation).
> Kerry
FWIW, both beaded and non-beaded foam cuts well with a hot wire, but
possibly at different temperatures.
I've formed lots of radio control aircraft using white (beaded), as well
as pink and blue foam. I often used the cheaper beaded stuff on combat
aircraft, as they were so frequently destroyed.
The OP should ask on rec.models.rc.air. Those folks literally do this
stuff every day.
"no spam" <[email protected]> wrote in message
news:[email protected]...
> The son wants to comparative study of airfoil designs as a science fair
> project and he (and I) need a little help.
>
> His plan is to make blades out of balsa, put them on a small remote controlled
> helo he got a few years ago, place helo on a scale (small enough so the
> majority of the thrust doesn't fall on the scale) then see which design gives
> the best lift.
>
> He has found some plans for different designs but I think he could use others.
> Any websites out there for this?
>
> Also I have NO experience in working with wood models or caving and he has
> even less. How would you suggest he goes about carving the foils? I was
> thinking a dremal type tool would work but what kind of blade/head would be
> needed?
>
> My biggest question is how in the world do you make sure that the shape in the
> wood is the shape you want?
>
> Any and all help would be great and quickly because I'm sure he's going to be
> asking me and I'd like to impress him on my vast knowledge of woodworking and
> airfoil construction. ;)
Hard foam could be a substitute for balsa. A nichrome wire cutter powered by a
transformer of some sort would cut it nicely, and a guide could be cut from
cardboard at each end for the shape. Extruded styrene from the building
materials area of the hardware store would probably work well for this.
Bob
no spam wrote:
> The son wants to comparative study of airfoil designs as a science
> fair project and he (and I) need a little help.
>
> His plan is to make blades out of balsa, put them on a small remote
> controlled helo he got a few years ago, place helo on a scale (small
> enough so the majority of the thrust doesn't fall on the scale) then
> see which design gives the best lift.
>
> He has found some plans for different designs but I think he could
> use
> others. Any websites out there for this?
The Bible on wing sections is "Theory of Wing Sections" by Abbot & von
Doenhoff. 15 bucks from Amazon.
> Also I have NO experience in working with wood models or caving and
> he has even less. How would you suggest he goes about carving the
> foils? I was thinking a dremal type tool would work but what kind
> of
> blade/head would be needed?
Knife, maybe a cabinet scraper. I'm not going to try to describe a
sanding spline but if you google that term you should get some good
descriptions.
> My biggest question is how in the world do you make sure that the
> shape in the wood is the shape you want?
Make a template or set of templates out of cardboard or brass or
aluminum or thin plywood or whatever else floats your boat--when the
wing matches the templates you've got it right,.
> Any and all help would be great and quickly because I'm sure he's
> going to be asking me and I'd like to impress him on my vast
> knowledge of woodworking and airfoil construction. ;)
--
--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)
Kerry Montgomery wrote:
> "J. Clarke" <[email protected]> wrote in message
> news:[email protected]...
>> no spam wrote:
>>> The son wants to comparative study of airfoil designs as a science
>>> fair project and he (and I) need a little help.
>>>
>>> His plan is to make blades out of balsa, put them on a small
>>> remote
>>> controlled helo he got a few years ago, place helo on a scale
>>> (small
>>> enough so the majority of the thrust doesn't fall on the scale)
>>> then
>>> see which design gives the best lift.
>>>
>>> He has found some plans for different designs but I think he could
>>> use
>>> others. Any websites out there for this?
>>
>> The Bible on wing sections is "Theory of Wing Sections" by Abbot &
>> von Doenhoff. 15 bucks from Amazon.
>>
>>> Also I have NO experience in working with wood models or caving
>>> and
>>> he has even less. How would you suggest he goes about carving the
>>> foils? I was thinking a dremal type tool would work but what kind
>>> of
>>> blade/head would be needed?
>>
>> Knife, maybe a cabinet scraper. I'm not going to try to describe a
>> sanding spline but if you google that term you should get some good
>> descriptions.
>>
>>> My biggest question is how in the world do you make sure that the
>>> shape in the wood is the shape you want?
>>
>> Make a template or set of templates out of cardboard or brass or
>> aluminum or thin plywood or whatever else floats your boat--when
>> the
>> wing matches the templates you've got it right,.
>>
>>> Any and all help would be great and quickly because I'm sure he's
>>> going to be asking me and I'd like to impress him on my vast
>>> knowledge of woodworking and airfoil construction. ;)
>>
>> --
>> --
>
> Styrofoam (house insulation) and a hot knife might work well. For
> the
> hot knife, you can use a couple of feet of steel wire (guitar
> string;
> can't remember which one, but just a single wire) and an auto
> battery
> charger. If he makes a couple of templates (cardboard works fine) in
> the shape of the airfoil he wants, then sticks them to each end of a
> block of Styrofoam, then hold the wire against both templates at the
> same time as he moves it around the templates, he can make smooth,
> light weight airfoil sections.
Careful with the selection of foam though--the beaded stuff won't cut
smoothly that way and polyurethane gives off toxic vapors when
hot-wired. If you're got non-beade polystyrene though the technique
works a treat--that's basically the procedure that Burt Rutan
specified for cutting the wing cores for the VariEze and LongEze.
--
--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)
David Starr wrote:
> Chris Friesen wrote:
>> no spam wrote:
>>> The son wants to comparative study of airfoil designs as a science
>>> fair project and he (and I) need a little help.
>>
>> I did something similar back in high school.
>>
>>> His plan is to make blades out of balsa, put them on a small
>>> remote
>>> controlled helo he got a few years ago, place helo on a scale
>>> (small
>>> enough so the majority of the thrust doesn't fall on the scale)
>>> then
>>> see which design gives the best lift.
>>
>> My technique was to build a wind tunnel using a standard house fan
>> and simply put the wing on a post stuck through a hole in the
>> bottom,
>> resting on a digital scale. You can then graph angle of attack vs
>> lift for each airfoil type.
>>
>> A better technique would be to hang the wing from some thread front
>> and back. This would allow you to graph angle of attack vs both
>> lift and drag for each airfoil type.
>>
>> If you want to use the scale, you could flip it around so that the
>> force is downwards. This would solve the problem of the helicopter
>> flying away, and would also mean that the wind produced by the
>> blades would be going up, and thus not affecting the scale nearly
>> as
>> much.
>>
>>> He has found some plans for different designs but I think he could
>>> use others. Any websites out there for this?
>>
>> There are some at:
>> http://www.gliders.dk/airfoils.htm
>>
>> The Kline-Fogleman airfoil is kind of interesting. It almost looks
>> like it has a chunk taken out of it.
>>
>>> Also I have NO experience in working with wood models or caving
>>> and
>>> he has even less. How would you suggest he goes about carving the
>>> foils?
>>
>> A knife works fine, with sandpaper to finish. If you know someone
>> with a tablesaw you could kerf it at intervals to give you a
>> baseline. A bandsaw would allow you to hog off most of the excess.
>>
>>> My biggest question is how in the world do you make sure that the
>>> shape in the wood is the shape you want?
>>
>> Kerfing as mentioned above helps. Otherwise draw the shape on the
>> ends, cut away everything that isn't the shape.
>>
>> Chris
>
> Go with the wind tunnel. Mounting new blades on a model
> helicopter
> isn't a repeatable process. Changing blades will change the load on
> the engine, causing it to run faster or slower, createing more or
> less lift. Just changing the size or angle of attack of the rotor
> blades, while keeping the airfoil the same will change the
> performance of the helicopter.
> Wind tunnel doesn't have to be very long. A square or
> rectangular
> cross section works fine and is easier to make than a circular cross
> section. Have the fan suck air out of the wind tunnel rather than
> blow into it. The fan blades make the air turbulent which reduces
> lift and adds vibration to make your instrument readings jiggle.
> Make one side of the wind tunnel clear plastic so you can watch
> the
> action. Arrange a protractor some how to let you measure (and set)
> angle of attack. Angle of attack is very important, a change of a
> few
> degrees will change the measured lift greatly.
> One way of measuring lift might be to make a beam balance scale,
> the airfoil under test (pointed down) goes onto one arm of the
> balance, and you add weights to the other arm until the airfoil
> balances. I'd go with balsa wood 'cause it's light and easy to
> carve to shape. If the kid is new to carving, make sure he cuts
> AWAY from the
> fingers holding the wood. You can get more consistant results by
> making templates of the desired air foil out of file folder stock
> and
> using them to check the shape as carving progresses. Surface finish
> affects performance. Couple of coats of shellac, sand between
> coats,
> will increase performance.
>
> A really sophisticated tunnel would measure drag as well as lift,
> the
> true measure of airfoil performance is the lift/drag ratio. The
> ideal
> airfoil would create pure lift, no drag. Practical airfoils don't
> do
> that well.
>
> You might check with the boy and make sure that he really wants
> to
> do a wind tunnel as opposed to flying the helicopter. He could do a
> science project by measuring the performance of the helicopter, best
> altitude, speed, range, payload, fuel consumption. Make the
> measurements on a hot day, a cold day, a high pressure day, and a
> low
> pressure day. See if temperature or barometric pressure makes a
> measureable change in performance.
"Best altitude" could be an interesting project in itself depending on
how much the helicopter can lift and how high it can really fly.
--
--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)
Kerry Montgomery wrote:
> "J. Clarke" <[email protected]> wrote in message
> news:[email protected]...
>> Kerry Montgomery wrote:
>>> "J. Clarke" <[email protected]> wrote in message
>>> news:[email protected]...
>>>> no spam wrote:
>>>>> The son wants to comparative study of airfoil designs as a
>>>>> science
>>>>> fair project and he (and I) need a little help.
>>>>>
>>>>> His plan is to make blades out of balsa, put them on a small
>>>>> remote
>>>>> controlled helo he got a few years ago, place helo on a scale
>>>>> (small
>>>>> enough so the majority of the thrust doesn't fall on the scale)
>>>>> then
>>>>> see which design gives the best lift.
>>>>>
>>>>> He has found some plans for different designs but I think he
>>>>> could
>>>>> use
>>>>> others. Any websites out there for this?
>>>>
>>>> The Bible on wing sections is "Theory of Wing Sections" by Abbot
>>>> &
>>>> von Doenhoff. 15 bucks from Amazon.
>>>>
>>>>> Also I have NO experience in working with wood models or caving
>>>>> and
>>>>> he has even less. How would you suggest he goes about carving
>>>>> the
>>>>> foils? I was thinking a dremal type tool would work but what
>>>>> kind
>>>>> of
>>>>> blade/head would be needed?
>>>>
>>>> Knife, maybe a cabinet scraper. I'm not going to try to describe
>>>> a
>>>> sanding spline but if you google that term you should get some
>>>> good
>>>> descriptions.
>>>>
>>>>> My biggest question is how in the world do you make sure that
>>>>> the
>>>>> shape in the wood is the shape you want?
>>>>
>>>> Make a template or set of templates out of cardboard or brass or
>>>> aluminum or thin plywood or whatever else floats your boat--when
>>>> the
>>>> wing matches the templates you've got it right,.
>>>>
>>>>> Any and all help would be great and quickly because I'm sure
>>>>> he's
>>>>> going to be asking me and I'd like to impress him on my vast
>>>>> knowledge of woodworking and airfoil construction. ;)
>>>>
>>>> --
>>>> --
>>>
>>> Styrofoam (house insulation) and a hot knife might work well. For
>>> the
>>> hot knife, you can use a couple of feet of steel wire (guitar
>>> string;
>>> can't remember which one, but just a single wire) and an auto
>>> battery
>>> charger. If he makes a couple of templates (cardboard works fine)
>>> in
>>> the shape of the airfoil he wants, then sticks them to each end of
>>> a
>>> block of Styrofoam, then hold the wire against both templates at
>>> the
>>> same time as he moves it around the templates, he can make smooth,
>>> light weight airfoil sections.
>>
>> Careful with the selection of foam though--the beaded stuff won't
>> cut
>> smoothly that way and polyurethane gives off toxic vapors when
>> hot-wired. If you're got non-beade polystyrene though the
>> technique
>> works a treat--that's basically the procedure that Burt Rutan
>> specified for cutting the wing cores for the VariEze and LongEze.
>>
>> --
>
> John,
> Yep, that's why I suggested Styrofoam (house insulation).
Styrofoam is a brand name for a variety of products, some of which can
be hot-wired safely and others that can't. The blue Styrofoam at the
local Home Depot is polyurethane, not styrene.
Read the label, know what it's made out of, don't just assume because
it's "house insulation" that it's safe to hot-wire.
--
--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)
Kerry Montgomery wrote:
> "J. Clarke" <[email protected]> wrote in message
> news:[email protected]...
>> Kerry Montgomery wrote:
>>> "J. Clarke" <[email protected]> wrote in message
>>> news:[email protected]...
>>>> Kerry Montgomery wrote:
>>>>> "J. Clarke" <[email protected]> wrote in message
>>>>> news:[email protected]...
>>>>>> no spam wrote:
>>>>>>> The son wants to comparative study of airfoil designs as a
>>>>>>> science
>>>>>>> fair project and he (and I) need a little help.
>>>>>>>
>>>>>>> His plan is to make blades out of balsa, put them on a small
>>>>>>> remote
>>>>>>> controlled helo he got a few years ago, place helo on a scale
>>>>>>> (small
>>>>>>> enough so the majority of the thrust doesn't fall on the
>>>>>>> scale)
>>>>>>> then
>>>>>>> see which design gives the best lift.
>>>>>>>
>>>>>>> He has found some plans for different designs but I think he
>>>>>>> could
>>>>>>> use
>>>>>>> others. Any websites out there for this?
>>>>>>
>>>>>> The Bible on wing sections is "Theory of Wing Sections" by
>>>>>> Abbot
>>>>>> &
>>>>>> von Doenhoff. 15 bucks from Amazon.
>>>>>>
>>>>>>> Also I have NO experience in working with wood models or
>>>>>>> caving
>>>>>>> and
>>>>>>> he has even less. How would you suggest he goes about carving
>>>>>>> the
>>>>>>> foils? I was thinking a dremal type tool would work but what
>>>>>>> kind
>>>>>>> of
>>>>>>> blade/head would be needed?
>>>>>>
>>>>>> Knife, maybe a cabinet scraper. I'm not going to try to
>>>>>> describe
>>>>>> a
>>>>>> sanding spline but if you google that term you should get some
>>>>>> good
>>>>>> descriptions.
>>>>>>
>>>>>>> My biggest question is how in the world do you make sure that
>>>>>>> the
>>>>>>> shape in the wood is the shape you want?
>>>>>>
>>>>>> Make a template or set of templates out of cardboard or brass
>>>>>> or
>>>>>> aluminum or thin plywood or whatever else floats your
>>>>>> boat--when
>>>>>> the
>>>>>> wing matches the templates you've got it right,.
>>>>>>
>>>>>>> Any and all help would be great and quickly because I'm sure
>>>>>>> he's
>>>>>>> going to be asking me and I'd like to impress him on my vast
>>>>>>> knowledge of woodworking and airfoil construction. ;)
>>>>>>
>>>>>> --
>>>>>> --
>>>>>
>>>>> Styrofoam (house insulation) and a hot knife might work well.
>>>>> For
>>>>> the
>>>>> hot knife, you can use a couple of feet of steel wire (guitar
>>>>> string;
>>>>> can't remember which one, but just a single wire) and an auto
>>>>> battery
>>>>> charger. If he makes a couple of templates (cardboard works
>>>>> fine)
>>>>> in
>>>>> the shape of the airfoil he wants, then sticks them to each end
>>>>> of
>>>>> a
>>>>> block of Styrofoam, then hold the wire against both templates at
>>>>> the
>>>>> same time as he moves it around the templates, he can make
>>>>> smooth,
>>>>> light weight airfoil sections.
>>>>
>>>> Careful with the selection of foam though--the beaded stuff won't
>>>> cut
>>>> smoothly that way and polyurethane gives off toxic vapors when
>>>> hot-wired. If you're got non-beade polystyrene though the
>>>> technique
>>>> works a treat--that's basically the procedure that Burt Rutan
>>>> specified for cutting the wing cores for the VariEze and LongEze.
>>>>
>>>> --
>>>
>>> John,
>>> Yep, that's why I suggested Styrofoam (house insulation).
>>
>> Styrofoam is a brand name for a variety of products, some of which
>> can be hot-wired safely and others that can't. The blue Styrofoam
>> at the local Home Depot is polyurethane, not styrene.
>>
>> Read the label, know what it's made out of, don't just assume
>> because
>> it's "house insulation" that it's safe to hot-wire.
>>
>> --
>> --
> John,
> I agree that reading the label is very important - polyurethane does
> give off toxic fumes. But, from Dow's website, when they refer to
> Styrofoam they say "Styrofoam rigid foam insulation" or "Styrofoam
> extruded polystyrene insulation". And the sheet of blue Styrofoam
> I'm
> looking at is marked "Extruded polystyrene insulation" as have been
> all other sheets of blue rigid Styrofoam I've ever seen, including
> at
> Home Depot. Can't remember if this particular sheet came from Home
> Depot. There might be blue rigid foam insulation at Home Depot that
> is polyurethane, but I doubt that it's also Styrofoam.
Dow Corning TUFF-R.
I don't understand why you're so resistant to the notion of specifying
the foam by chemistry, which is on the label on any foam sold
commercially, instead of by the intended use "house insulation" or the
brand "Styrofoam".
--
--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)
Edwin Pawlowski wrote:
> "J. Clarke" <[email protected]> wrote in message
>>
>> Styrofoam is a brand name for a variety of products, some of which
>> can be hot-wired safely and others that can't. The blue Styrofoam
>> at the local Home Depot is polyurethane, not styrene.
>>
>> Read the label, know what it's made out of, don't just assume
>> because
>> it's "house insulation" that it's safe to hot-wire.
>>
>
> All the rigid board is extruded polystyrene.
> http://www.dow.com/styrofoam/na/res-us/products/
I give up. I tried. If the kid ends up gassing himself on your head
be it.
--
--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)
Kerry Montgomery wrote:
> "J. Clarke" <[email protected]> wrote in message
> news:[email protected]...
>> Kerry Montgomery wrote:
>>> "J. Clarke" <[email protected]> wrote in message
>>> news:[email protected]...
>>>> Kerry Montgomery wrote:
>>>>> "J. Clarke" <[email protected]> wrote in message
>>>>> news:[email protected]...
>>>>>> Kerry Montgomery wrote:
>>>>>>> "J. Clarke" <[email protected]> wrote in message
>>>>>>> news:[email protected]...
>>>>>>>> no spam wrote:
>>>>>>>>> The son wants to comparative study of airfoil designs as a
>>>>>>>>> science
>>>>>>>>> fair project and he (and I) need a little help.
>>>>>>>>>
>>>>>>>>> His plan is to make blades out of balsa, put them on a small
>>>>>>>>> remote
>>>>>>>>> controlled helo he got a few years ago, place helo on a
>>>>>>>>> scale
>>>>>>>>> (small
>>>>>>>>> enough so the majority of the thrust doesn't fall on the
>>>>>>>>> scale)
>>>>>>>>> then
>>>>>>>>> see which design gives the best lift.
>>>>>>>>>
>>>>>>>>> He has found some plans for different designs but I think he
>>>>>>>>> could
>>>>>>>>> use
>>>>>>>>> others. Any websites out there for this?
>>>>>>>>
>>>>>>>> The Bible on wing sections is "Theory of Wing Sections" by
>>>>>>>> Abbot
>>>>>>>> &
>>>>>>>> von Doenhoff. 15 bucks from Amazon.
>>>>>>>>
>>>>>>>>> Also I have NO experience in working with wood models or
>>>>>>>>> caving
>>>>>>>>> and
>>>>>>>>> he has even less. How would you suggest he goes about
>>>>>>>>> carving
>>>>>>>>> the
>>>>>>>>> foils? I was thinking a dremal type tool would work but
>>>>>>>>> what
>>>>>>>>> kind
>>>>>>>>> of
>>>>>>>>> blade/head would be needed?
>>>>>>>>
>>>>>>>> Knife, maybe a cabinet scraper. I'm not going to try to
>>>>>>>> describe
>>>>>>>> a
>>>>>>>> sanding spline but if you google that term you should get
>>>>>>>> some
>>>>>>>> good
>>>>>>>> descriptions.
>>>>>>>>
>>>>>>>>> My biggest question is how in the world do you make sure
>>>>>>>>> that
>>>>>>>>> the
>>>>>>>>> shape in the wood is the shape you want?
>>>>>>>>
>>>>>>>> Make a template or set of templates out of cardboard or brass
>>>>>>>> or
>>>>>>>> aluminum or thin plywood or whatever else floats your
>>>>>>>> boat--when
>>>>>>>> the
>>>>>>>> wing matches the templates you've got it right,.
>>>>>>>>
>>>>>>>>> Any and all help would be great and quickly because I'm sure
>>>>>>>>> he's
>>>>>>>>> going to be asking me and I'd like to impress him on my vast
>>>>>>>>> knowledge of woodworking and airfoil construction. ;)
>>>>>>>>
>>>>>>>> --
>>>>>>>> --
>>>>>>>
>>>>>>> Styrofoam (house insulation) and a hot knife might work well.
>>>>>>> For
>>>>>>> the
>>>>>>> hot knife, you can use a couple of feet of steel wire (guitar
>>>>>>> string;
>>>>>>> can't remember which one, but just a single wire) and an auto
>>>>>>> battery
>>>>>>> charger. If he makes a couple of templates (cardboard works
>>>>>>> fine)
>>>>>>> in
>>>>>>> the shape of the airfoil he wants, then sticks them to each
>>>>>>> end
>>>>>>> of
>>>>>>> a
>>>>>>> block of Styrofoam, then hold the wire against both templates
>>>>>>> at
>>>>>>> the
>>>>>>> same time as he moves it around the templates, he can make
>>>>>>> smooth,
>>>>>>> light weight airfoil sections.
>>>>>>
>>>>>> Careful with the selection of foam though--the beaded stuff
>>>>>> won't
>>>>>> cut
>>>>>> smoothly that way and polyurethane gives off toxic vapors when
>>>>>> hot-wired. If you're got non-beade polystyrene though the
>>>>>> technique
>>>>>> works a treat--that's basically the procedure that Burt Rutan
>>>>>> specified for cutting the wing cores for the VariEze and
>>>>>> LongEze.
>>>>>>
>>>>>> --
>>>>>
>>>>> John,
>>>>> Yep, that's why I suggested Styrofoam (house insulation).
>>>>
>>>> Styrofoam is a brand name for a variety of products, some of
>>>> which
>>>> can be hot-wired safely and others that can't. The blue
>>>> Styrofoam
>>>> at the local Home Depot is polyurethane, not styrene.
>>>>
>>>> Read the label, know what it's made out of, don't just assume
>>>> because
>>>> it's "house insulation" that it's safe to hot-wire.
>>>>
>>>> --
>>>> --
>>> John,
>>> I agree that reading the label is very important - polyurethane
>>> does
>>> give off toxic fumes. But, from Dow's website, when they refer to
>>> Styrofoam they say "Styrofoam rigid foam insulation" or "Styrofoam
>>> extruded polystyrene insulation". And the sheet of blue Styrofoam
>>> I'm
>>> looking at is marked "Extruded polystyrene insulation" as have
>>> been
>>> all other sheets of blue rigid Styrofoam I've ever seen, including
>>> at
>>> Home Depot. Can't remember if this particular sheet came from Home
>>> Depot. There might be blue rigid foam insulation at Home Depot
>>> that
>>> is polyurethane, but I doubt that it's also Styrofoam.
>>
>> Dow Corning TUFF-R.
>>
>> I don't understand why you're so resistant to the notion of
>> specifying the foam by chemistry, which is on the label on any foam
>> sold commercially, instead of by the intended use "house
>> insulation"
>> or the brand "Styrofoam".
>>
>> --
>
> John,
> Not resistant at all to specifying foam by chemistry, but the brand
> Styrofoam is a perfectly adequate way to specify Dow brand rigid
> Styrofoam, which is what I suggested to the OP as a material to
> investigate.
> The only TUFF-R that I know of is insulation clad on both sides;
> don't
> remember what color the core is, but it's not labeled Styrofoam. And
> wanted to correct any misconception that you may have caused by
> saying that there was "...blue Styrofoam at the local Home Depot is
> polyurethane, not styrene.", as there isn't any such thing.
If you had said "Styrofoam _brand_ blue insulating foam but make sure
that it's really Styrofoam brand and that it's really polystyrene" I
wouldn't have had any problem with what you said, but walking into a
store and asking for "styrofoam house insulation" is just too likely
to get the wrong stuff.
--
--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)
"J. Clarke" <[email protected]> wrote in message
>
> Styrofoam is a brand name for a variety of products, some of which can
> be hot-wired safely and others that can't. The blue Styrofoam at the
> local Home Depot is polyurethane, not styrene.
>
> Read the label, know what it's made out of, don't just assume because
> it's "house insulation" that it's safe to hot-wire.
>
All the rigid board is extruded polystyrene.
http://www.dow.com/styrofoam/na/res-us/products/
"Kerry Montgomery" <[email protected]> wrote in message
>> All the rigid board is extruded polystyrene.
>> http://www.dow.com/styrofoam/na/res-us/products/
>>
>
> Edwin,
> Actually, Bayer makes rigid board polyurethane insulation:
> http://tinyurl.com/2rytbj
> but it's not going to be marked Styrofoam.
> Kerry
Correct, I was referring to the Dow products. Thee are plenty of other
materials available.
The problem with using a propeller is that not only is it curved it's
twisted as well with the angle of attack changing as you move from the
center of the blade out to the tip.
I agree that testing a wing rather than a propellar would be easier to
deal with and display.
Setting up a fan with a thin foam baffle in front of it might simplify
the project, but if I remember the Wright brother's tunnel was
actually an elongated circle like a race track with the fan on the
back side away from the testing area. The curves also served to
stablize the air flow somewhat.
Then he can set up the wing to be tested on a stand on the scale in
the tunnel. Using threads on the wings he can show the airflow over
and under the wing.
By changing the angle of attack he can show how the lift and airflow
change that way.
Graphing the data for comparison would show a lot too. I would look
for wings with known flight characteristics
I'm wandering though. Using a wing rather than a propeller he only
has to have one pattern for each wing, where the only way I can think
to carve a propeller correctly would be with a CNC machine. There are
a LOT of balance issues to look at with propellers.
On Mon, 05 Nov 2007 21:42:52 GMT, "no spam" <[email protected]> wrote:
>The son wants to comparative study of airfoil designs as a science fair
>project and he (and I) need a little help.
>
>His plan is to make blades out of balsa, put them on a small remote
>controlled helo he got a few years ago, place helo on a scale (small enough
>so the majority of the thrust doesn't fall on the scale) then see which
>design gives the best lift.
>
>He has found some plans for different designs but I think he could use
>others. Any websites out there for this?
>
>Also I have NO experience in working with wood models or caving and he has
>even less. How would you suggest he goes about carving the foils? I was
>thinking a dremal type tool would work but what kind of blade/head would be
>needed?
>
>My biggest question is how in the world do you make sure that the shape in
>the wood is the shape you want?
>
>Any and all help would be great and quickly because I'm sure he's going to
>be asking me and I'd like to impress him on my vast knowledge of woodworking
>and airfoil construction. ;)
>
My daughter did the same thing to me several years ago. My solution to
get the project done, was to show her how to build the fuselages from
the expanding foam in a can, (Great Stuff).
We made the basic shape using toilet paper rolls and card board cones.
Once the basic foam shape was created the foam carved easily into the
proper shape for the fuselage, and surprisingly the foam pores were
quite small so it looked good when finished.
While we used balsa wood for the wings and stabilizer, you could build
the airfoil shape of the wing the same foam.
no spam wrote:
> The son wants to comparative study of airfoil designs as a science fair
> project and he (and I) need a little help.
>
> His plan is to make blades out of balsa, put them on a small remote
> controlled helo he got a few years ago, place helo on a scale (small enough
> so the majority of the thrust doesn't fall on the scale) then see which
> design gives the best lift.
>
> He has found some plans for different designs but I think he could use
> others. Any websites out there for this?
>
> Also I have NO experience in working with wood models or caving and he has
> even less. How would you suggest he goes about carving the foils? I was
> thinking a dremal type tool would work but what kind of blade/head would be
> needed?
>
> My biggest question is how in the world do you make sure that the shape in
> the wood is the shape you want?
>
> Any and all help would be great and quickly because I'm sure he's going to
> be asking me and I'd like to impress him on my vast knowledge of woodworking
> and airfoil construction. ;)
>
>
--
Keith Nuttle
3110 Marquette Court
Indianapolis, IN 46268
317-802-0699
IMHO your best bet is to grind or cut a custom scraper for each
profile you want, and use that to cut the balsa to the right profile.
That way, the results are predictable and consistent - just scrape
until the scraper hits the table (holding it vertically) and you know
the profile is the same all down each blade.
Note that balsa is a porous wood; you should use a wood filler at
least, and paint perhaps, to get a smooth surface. Otherwise you have
to account for turbulence too. Hey! Something else to measure.
You could use the dremel tool to grind the scrapers.