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May 13, 2019, 11:39 PM
flyin' fool
goldguy's Avatar
The 4/40 is a proven! You can bend it or Jedelsky it ……….
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May 14, 2019, 03:18 AM
IMO ( In My Opinion ) →
balsa or carbon's Avatar
Originally Posted by goldguy
The 4/40 is a proven! You can bend it or Jedelsky it ……….
I Jedelsky'd a few times .....
May 14, 2019, 05:29 PM
pmanu's Avatar
Thread OP
Originally Posted by goldguy
The 4/40 is a proven! You can bend it or Jedelsky it ……….
those foils look good also.

so I spent the time in SketchUp using the formula in Jef Raskin paper and worked out what i need,

now I need to work out how to stop it from being so flimsy

FYI ....I did build a modded over sized GenBond BluClub2 12 years ago,still got it
May 14, 2019, 08:28 PM
Build, crash...repeat
AleRRon's Avatar
“now I need to work out how to stop it from being so flimsy”

One word:

May 14, 2019, 10:36 PM
Scratch builder
Newspaper covering will give it torsional strength. Carbon fiber rods glued into grooves top and bottom work well as spars. As AleRRon suggests, ribs can be used to keep the camber correct.

I just finished a plane using a hot wired airfoil 4% camber 40% back with a thickness of 4.5 %

I used to print out a GOE 419 airfoil 280mm chord, and 14mm thick. The first 30% of the airfoil is covered in blank newspaper top and bottom. The 1mm carbon rods are just under the paper at about 28% back.

I found the best method for me was to hot wire wing sections 150mm long. Eight sections in all glued together gave me the wing span I wanted. I found the long wire needed for half a wing had intolerable lag. With an airfoil this thin, it just didn't work for me.

I too experimented with flat sheets but used poster board foam, and built my own version of Balsa and Carbon's Fogey with the faceted wing. It was easy to build but I wanted the same 4% camber you are after as well. A full airfoil seemed to be the answer.

I did some calculating with the assistance of AutoCad and found that the newspaper method combined with 1/2 lb./cu. ft. density (don't know the metric equivalent) would give me the lightest wing. The foam I used is the beaded kind I found in a local dumpster. (furniture packing)

I am interested in very slow flight so light wing loading is a must. My new plane is at 2.065 oz./sq. ft. (sorry no metric equiv. here either) 48 inch span and weighs 7.2 oz. with battery.

If your foam is more dense than mine, you will need less paper to stiffen the wing.

A flat sheet like your using has a good chance of working, keep going.

One thing I thought of but didn't try was to cut flat sheets into short sections, bend them close to the 4% camber, and use balsa ribs of the same wing section you have drawn glued between the segments. This would give a good camber with no exposed ribs.

Ken S.
May 14, 2019, 11:33 PM
flyin' fool
goldguy's Avatar
The downside of paper covering is it's very brittle. I've seen guys snap wings like a twig from an impact.

I fly slope combat and we prefer tape or laminating film as it allows for some flex to absorb the impact from hits and crashes.
May 15, 2019, 08:34 AM
Scratch builder
Which is lighter, the film or tape? I've read about both but wrote them off as too heavy when compared to newspaper.

Both would certainly stiffen the curved sheet Pmanu is talking about.
Last edited by KenSt; May 15, 2019 at 08:42 AM.
May 15, 2019, 01:22 PM
flyin' fool
goldguy's Avatar
I would think tape or film is lighter than paper and glue. I guess the weight depends on the thickness used. Film needs heat, OK on EPP, but not on most other foams.

We found the second best stickiest tape at our local post office. The most sticky of all we tested is only found in Canada.

I think there is a US distributor, so you might look around.
Last edited by goldguy; May 15, 2019 at 01:28 PM.
May 16, 2019, 02:47 AM
Registered User
PaulB's Avatar
Couple of years ago I wanted to decorate a model but my airbrush was out of action. At the time I happened to be placing an order with HK and spotted this :-

Very thin, sticks like you know what to a blanket and strong.

Also pretty good for making your pride and joy look pretty. Stick lengths down onto standard kitchen baking paper (side by side touching each other if needs be) and then just cut out the desired shape. Paper peels off real easy so it is just like a standard self-adhesive decal.

Latest blog entry: Just To Say Hello.......
May 16, 2019, 07:35 AM
pmanu's Avatar
Thread OP
thanks guys for the ideas.......
I just tried my best sticky tape to some insulation foam that I planed to use and it comes off pretty easy,
it seems to pull the little balls out that glued in that well,
Id like to try some of the thin Laminating film you put on books, Matt uses it all the time on his models(rags the nuts)
May 16, 2019, 11:49 AM
flyin' fool
goldguy's Avatar
Foam made up of little balls is not the best to work with.
May 16, 2019, 03:25 PM
I Look, Listen, and Learn
Timbo383's Avatar
Sounds like you have that really light, large cell foam that will not be stiff enough no matter what you do to it. I know you are using what you have available but I don't think you are going get what you want out of this foam. But if you are to give it a try anyways you can try using spray adhesive before applying tape, it will help stick to it better. I do believe the paper and glue method would be the better option tho with this type of foam.
May 18, 2019, 06:30 PM
Redbilly Band Member
Ron H's Avatar
One method I have used on flimsy foam is to tape a small fiberglass rod to the leading and trailing edges. It helps quite a bit, but the tape has to hold or it's useless.
May 19, 2019, 02:19 AM
pmanu's Avatar
Thread OP
I cut the test wing section yesterday and it is very flimsy. for a 1200mm ws 200mm cord wing using Jef Raskin formula it should be 4% which makes it only 8mm thick, I tried tape long ways but because its so thin the tape does next to nothing. will try a couple of spars and laminating but for the model weight i would expect to be under the wing of about 1kg I dont think wing will be strong unless it has alot of work done to it,I use to use carpet glue(laytex?) and thin cardboard on some of my older models but that made them very heavy.
May 19, 2019, 12:32 PM
flyin' fool
goldguy's Avatar
Check this idea out ................................

Combining the UC and KF airfoils, with a spar.

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