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-   -   Leading edge (http://www.Wattflyer.com/forums/showthread.php?t=73154)

TalleyHo 02-07-2014 04:23 PM

Leading edge
 
Hello

I'm new to the electric world. My dad recently introduce my son to the joy of electric flight. I've gotten the itch to dig out my old nitros, but the radios and such are so old (circa 90's) that I'd rather just start into electric.

I've been looking at plans for building a foam wing. The thing I can't seem to figure out from the pics is how the leading edge is formed. I get how the airfoil is being formed, but surely there has to be more than just tape for the leading edge. Do you cut a 45-deg angle across the front edge and then tape it so you have some sort of bevel?

And how do you stiffen up the foam? I got some depron 6mm from HobbyTown, but it still feels super flimsy. I couldn't find any FFF at HomeDepot/Lowes. Is a balsa spar across the CG really all that is needed? Or do I need to cover it in paper/monocote?

I'm anxious to get back into it. The trainer cub my son is flying just doesn't cut it for me :)

solentlife 02-07-2014 05:17 PM

Everyone has their way of doing it ...

So my suggestion is you look through the scratchbuild listings here and note the various ways of completing structures. Build up your own ways to solve it.

Get on free plan listings ... outerzone ... hippocket builders etc. - to check out plans and schemes.

You will find many ways to do it and once you find what works for YOU --- away you go.

Nigel

Larry3215 02-07-2014 05:24 PM

It all depends :)

Look through a few of the build threads here in this forum. You will see many many different building techniques - and they all work :D

For the most part, foamies have a flat wing with just a square, straight cut on the foam for the leading edge. Based on some tests Ive seen, that square edge actually works better for foamies with a flat wing airfoil than a rounded or beveled leading edge.

As far as spars - it depends on the wing span and the weight of the foamy and how you plan to fly it. For most foamies, a simple wood (spruce or other hardwood) spar is fine. Most guys tend to use carbon tubes or rods to save weight though.

Your best bet is to find a design you like in here and just do what they did. After you have built a few you will get a feel for what works best for you.

You can also tell us what your plans are and ask for recommendations - you will get lots of them and they will be mostly different AND most of them will still work just fine.

Building foamies is a pretty forgiving thing and most of the details are not all that critical.

The most important thing is to try to keep the weight down as much as possible.

Good luck and keep us posted on your ideas and progress! :)

Larry3215 02-07-2014 05:35 PM

10 Attachment(s)
A few of the foamies Ive built over the years. Some small, some giant scale. Most have simple flat wings with square leading edges and some have full airfoil wings :)

quorneng 02-07-2014 06:09 PM

1 Attachment(s)
TallyHo
I does rather depend on what you mean by a "foamie".
A single plank of Depron as a wing will almost certainly need reinforcing for bending but may be stiff enough to resist the twisting forces hence the single spar type design.

If you 'build up' a wing out of Depron sheet (top and bottom skins over ribs) then the wing is thicker so is stronger and stiffer to start with and the reinforcing required (conventional top and bottom spar?) is less.

If the plane has a very low aspect ratio (i.e. a delta) you may get away with a built up Depron wing with no reinforcing at all providing it is below below a certain size and weight.

A rather extreme example but the complete airframe for this 35" (890mm) span Fairey Delta 2 EDF is built entirely from 2mm Depron sheet with no reinforcing anywhere!
Attachment 173327
Not exactly crash resistant but it flies well.

TalleyHo 02-07-2014 06:14 PM

I've been looking to imitate the CrashTestHobby Assasin and/or the MS Composit II planes - a flying delta wing. I wasn't planning on going 'full-spar foam covered' like in the old days.

Aside from not having an idea on the LE, I was just going to sandwich rod in-between 2 layers of foam to give it a little bit of symmetry. I didn't have any delusions of trying to build a bunch of spars and cover them with foam. I don't have that kind of attention span (my dad was the builder back in the day - I was the pilot:) )

I guess I just need to jump in and give it a whirl. From everything I read, it sounds like anything will fly with enough power. I just don't want to make the first one that doesn't fly :)

fhhuber 02-07-2014 07:30 PM

Too late to make the first one that doesn't fly.
That trick has been accomplished many times already:rolleyes:

kyleservicetech 02-07-2014 09:16 PM

Quote:

Originally Posted by TalleyHo (Post 939396)
Hello

I'm new to the electric world. My dad recently introduce my son to the joy of electric flight. I've gotten the itch to dig out my old nitros, but the radios and such are so old (circa 90's) that I'd rather just start into electric.

I've been looking at plans for building a foam wing. The thing I can't seem to figure out from the pics is how the leading edge is formed. I get how the airfoil is being formed, but surely there has to be more than just tape for the leading edge. Do you cut a 45-deg angle across the front edge and then tape it so you have some sort of bevel?

And how do you stiffen up the foam? I got some depron 6mm from HobbyTown, but it still feels super flimsy. I couldn't find any FFF at HomeDepot/Lowes. Is a balsa spar across the CG really all that is needed? Or do I need to cover it in paper/monocote?

I'm anxious to get back into it. The trainer cub my son is flying just doesn't cut it for me :)

There are a LOT of foamies available that are anything but "Trainers". Case in point, those 100 MPH foamie jets that a lot of my club members have. Some of those models are ready to fly right out of the box.

Check the listings for these bind and fly type models in your local hobby shop, or www.towerhobbies.com.
http://www3.towerhobbies.com/cgi-bin...tric&search=Go

CHELLIE 02-08-2014 08:20 AM

simple foam wing
 
Hi, Here is a nice foam wing that can be built with blue foam or depron, I would use a balsa spar rather than the foam spar, and you can cover it with coloured packing tape.

http://www.rcgroups.com/forums/showthread.php?t=497083

http://www.fast-pack.com/colored_tape.html

http://www.headsuphobby.com/Emax-CF2...otor-H-445.htm

use a 7x6 apc prop and a 30 amp esc.

http://static.rcgroups.net/forums/at...N1241LOWER.jpg

CHELLIE 02-08-2014 11:44 AM

To form a leading edge, if its one piece of foam, lay some packing tape where the edge will be at, score the back side with a pen, about 1" Wide where the bend will be at, and use a wood dowel for a guide and bend the foam around the wood dowel, heat the foam a little with a hair drier to get it soft to bend.
Here are a few of my scratch built foamies, you can get some ideas on how to work with Depron foam.



http://www.youtube.com/watch?v=dpzGJ7387qA

http://www.youtube.com/watch?v=vYM-T4XPM-o

http://www.youtube.com/watch?v=WKN3vIMWYnI

http://www.youtube.com/watch?v=osBLqE3uFVE

http://www.youtube.com/watch?v=yV4UHMPVsYo

http://www.youtube.com/watch?v=BKzpykeO3kg

scratch built foamies

http://www.wattflyer.com/forums/showthread.php?t=55444

TalleyHo 02-09-2014 02:27 AM

Wow - that first vid from Clint Judd was awesome. That's how I thought it might work, but he made it look stupid easy.

What kind of tape is that? Just standard colored packing tape? It looks really thin.

Amazing the straight lines he can cut free hand :)

CHELLIE 02-09-2014 03:34 AM

Quote:

Originally Posted by TalleyHo (Post 939491)
Wow - that first vid from Clint Judd was awesome. That's how I thought it might work, but he made it look stupid easy.

What kind of tape is that? Just standard colored packing tape? It looks really thin.

Amazing the straight lines he can cut free hand :)

Some of these scratch foam builders are Samurais with a Razor Knife :D look around to find some lite weight vinyl tape in one piece or you can use coloured packing tape. the thin tape is fine, its strong and lite. all of the Videos will give you an idea or 2 to help you with your build, I have learned a lot watching some of these You tube videos, Take care, Chellie


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