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        Discussion Glass/Kevlar/CF D-Tube

#1 schrederman Feb 23, 2012 12:46 PM

Glass/Kevlar/CF D-Tube
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I have a very nice flying RES Glider design with super strong wing spars... Only problem is flutter. I need to stiffen the wood D-Tube to prevent flutter at high speeds. I am considering using .5 oz. Kevlar on a bias wrapped around the D-Tube back ro the spar. I would most likely use surfacing resin as the adhesive. Anyone have experience with this? Will it work?


#2 wyowindworks Feb 23, 2012 01:10 PM

What is surfacing resin?

Carbon will do a better job at stiffening the structure than kevlar

#3 schrederman Feb 23, 2012 03:23 PM

Surfacing resin is epoxy that is used for applying light glass to fuselages, etc... I know cf would be best for stiffening but can I buy it in that weight? I have never seen cf cloth at 1/2 oz.

#4 wyowindworks Feb 23, 2012 03:37 PM

That kind of resin is typically called a laminating resin. I wanted to clarify your intent because there are epoxy systems that specifically designed for surfacing table tops. These type of resins are often called surfacing resins and perform poorly as a laminating resin.

Where are you getting .5 ounce woven kevlar?

#5 schrederman Feb 24, 2012 08:08 AM

After looking last night, about the lightest available right now is .7 oz. That's not enough difference to sneeze at... I believe that was on the CST website.

So, do you think it would be worth the effort in torsional stiffening? I'm also considering a bagged D-Tube with balsa ribs aft.

#6 wyowindworks Feb 24, 2012 08:12 AM

Most 9 ounce discus launch gliders are done with a 2 ounce carbon D-box or 1.7 ounce kevlar.

#7 jfrickmann Feb 24, 2012 04:30 PM

The lightest aramid weave I know is 1 oz. Do not use felt or matte, it will soak too much resin. The same is true for fabric woven from spun thread - there is some 0.8 oz stuff from spun thread. Consider 0.75 oz fiberglass.

#8 schrederman Feb 27, 2012 02:51 PM

Will .75 oz. glass make it torsionally rigid enough?

#9 Mr B.... Feb 27, 2012 04:36 PM

Jack 3/4 is to light go with 2.1 glass over the center and 1.4 glass over the LE top and bottom. If you use a white trash bag you can get must of the resin out with. If you need some give me a call.

PS What are you doing speed runs for with a woodie?


#10 schrederman Feb 27, 2012 07:33 PM

I had a Homer Simpson moment, and thought I could do a full J launch with it... DOH!!!

PM me your number, if you don't mind, along with the best time to call so I won't be a bother to your family...



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