jw637362

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I actually posted this in the Scratch Build forum and no replies so I will try it here:

:I am redesigning a glider from the seventies / 12 foot wing span.

This is my first design of wing of this size, I have cut (and cut and cut) the ribs for the one side so far.
Looking for a good source or what style of wood to use for the spars.
Is it Basswood that is most commonly used?
I need to get it in 48" lengths. - 3/8" x 1/8"

My plan is to also utilize carbon fiber strips on the underside of the spars as well for extra strength and then wrap the spar area at the root of the wing for extra support with Kevlar string, I have seen this done before and would like some pointers.

Sources for Kevlar string and what size to use?
Spar material source?
How to do it all - Priceless?

I found the answer already to the Carbon fiber and Kevlar wrap Source questions but if someone has links to sources or pictures of a wing being Kevlar wrapped, or how to do it, that would be great.

Thanks, Appreciate the help.

Jeff

vortex00

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Check out Wick's Aircraft for their Spruce products for homebuilt aircraft. You can get just about any size you need.

http://www.wicksaircraft.com

I've used 1/4" Spruce spars for the plug-in wing box up to 2" depth in this U-2:

Jack

KJohn

Here are some web pages to visit:

http://www.badger.rchomepage.com/bot.html
http://www.badger.rchomepage.com/spar.html

I suspect that 3/8x1/8 inch spar material might be rather light material. I use spruce of that dimension on 100'' sailplane wings.

Note that sometimes the carbon material is placed on spruce which is then placed on the shear web material (I suspect this would be true of the shear web material was not as wide as the carbon spar material)... and ... sometimes the carbon material is placed directly on the shear web material (probably in those cases where the shear web matrial was the same width as the carbon material).

I believe spruce spars are preferred over bass in most cases.

Also, placing carbon material on the bottom spar of the wing (or as the bottom spar) is good but placing carbon material on the upper spar (or as the upper spar) is very good. Apparently the top spar has far more dangerous compressive forces with which to deal than the bottom has tension forces with which to deal. But proper construction would call for both these materials to be properly chosen to work together as you could introduce a 'weak link' in the design of a functional I-beam if care is not taken in proper selection and placing of complementing material.

Some of the nostalgia class planes had large wings and many appear to have been updated to utilize new material. Maybe someone will contribute such information.

Maybe it would help to mention how the sailplane would be launched and if it will have flaps, ailerons, etc. so that more specific suggestions could be posted.

jw637362

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Thanks for the replies -

KJOHN, that is exactly what I was looking for, I knew it had been done before, Carbon and Kevlar wrapped nostalgia wing.

I am building a wing for a Soarcraft Magnum 12 - the 12 stands for you guessed it, 12 foot wingspan. It has spoilers.

I will be hi start launching it. Looking at 100 foot Aeroform mandrel dipped tubing with 400 foot of nycord. Should get quite the elevation.
I will be purchasing a winch, or parts of a winch and building it in the future, which is why I am going for the extra support in the wing. I do not want it too stiff, needs a little flex but want it very secure at the fuse.
My hobby shop only sells 36" lengths of spruce?? Where do I get the high quality 48" stock and carbon strips for the caps, Kevlar string.
The original kit does utilize the 3/8 x 1/8 size spars and utilizes the "I" beam spar configuration for the webs. It seems a little thin but that is what it has. I have made the ribs for the left wing so far.

Thanks, Jeff

KJohn

Carbon and Kevlar, etc. can be found here:

http://www.acp-composites.com/acp-cat.htm
http://www.cstsales.com/HTBuildCarbonSpar.htm

Balsa and maybe spruce can be found here:

http://www.lonestar-models.com/

Use WWW.GOOGLE.COM for finding other such suppliers. Also, there are ways to search old threads on most message boards and you might find similar interests have been addressed in the past.

I find that the wings are the most demanding in terms of accuracy and strength so I tend to concentrate on the wings the most. Once I have a set of well constructed wings the fuselage and other elements are rather less of a demanding challenge.

I have always liked the looks of the larger sailplanes ... 130'' or so but I have never built one that large to date. I am sure one day I will. Here is a beauty:

http://home.earthlink.net/~eddumas/rcmodels.htm

And the Dodgson Design sailplanes such as the Lovesong/Windsong, Anthem, Saber, Camano and such always caught my attention but I never had the opportunity to build and fly one. The ones that 'got away' I guess. I am finding that the flying is less of an interest than the construction/engineering. If that effort is successful the flying is sort of a 'given' !!