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General control line discussion => Open Forum => Topic started by: Sean McEntee on July 11, 2014, 07:13:48 AM
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Not directly control-line related, but sort of.
Trying a built-up wing for a discus HLG in the never-ending effort to build lighter.
Which would provide more rigidity: Silkspan or Polyspan?
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for that plane use JAP tissue. Tinsel strength is higher and it takes less dope.
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I would agree with Sparky. Jap tissue is extremely rigid when doped.
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However, Jap tissue is easily punctured, regardless of the thickness of dope. I have found Polyspan to be the toughest. I like it better than silk because you can control the shrinkage with Poly, whereas, silk often shrinks enough to bend the structure!
Another consideration is availability. Heavy silkspan is hard to find. Tight-weave "China" silk is also hard to find.
I just ordered a large roll of Polyspan (not very expensive, either)
Floyd
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Unless your goal is to win the FF Nats with this model, I would use polyspan. I use it on all my FF models large and small. Japanese tissue is indeed light and strong and is available in lots of colors but is fragile. My primary FAI gas model has 35 patches on the bottom of the wing from straw grass punctures, and that's using Polyspan! I do use tissue for color accents over the polyspan.
Post this question on the NFFS website and you will get some truly expert responses.
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This wing is for a discus or tip launched glider. There is a definate line wnere weight has a negaitive or positive effect. Too light and it's hard to get max altitude, a mldestly higher weight transfers into momentum and speed at launch, and hopefully higher launch. If you have never seen or launched a glider this way, it's amazing the altitude you can get for the least amount of energy spent. My answer to the question would be polyspan on the bottom, and tissue on the top. Best of both worlds with punture resistance on the bottom when it DTs and lighter weight on the top of the wing. For for extra torsional stiffness if needed, you can dope on "X"s or diagonals of carbon fibre tow on the bottom and/or top of the wing. Or add internal diagonal bracing.
I WILL get around to building those kits you gave me, as this is an interesting way to get a glider in the air, even if you have an older, worn out arm!
Type at you later,
Dan McEntee