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Author Topic: Biofoam catapult 8inch glider  (Read 678 times)
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B.karthik
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« on: July 18, 2009, 01:01:32 PM »

hi friends i have made a 8inch wingspan biofoam(4mm)catapult launch glider.
materials:
1.biofoam of 4mm thick
2.bamboo for fuselage
3.balsawood for fin
problem:
1.foam of wing bends when launched with full stretch by catapult
solution:
1.given a reinforcement in the wing with 0.2cm thick woodstick used for home-cleaning.

question:
1.shall i need to give reinforcement for tailplane?
2.what are the materials can be used for reinforcement?
3.how should i groove in wing for placing the stick for reinforcement accurately?
thanks
karthik
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Biofoam catapult 8inch glider
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Kev
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« Reply #1 on: July 21, 2009, 04:44:57 AM »

Karthik

First - I would strengthen the leading edge of the wing with balsa or spruce to give this some rigidity. If you havent got something like this, adhere a bamboo skewer. This will help massively. However, foam being as it is and its composition, unless you use something where you can shape the wing from start by sanding foam down (wear a mask) - something like Rohacell, then you really have a weak wing structure.

If you got a block of foam and were able to put a leading and trailing edge of balsa and then sand down, you may have a chance. However, the leading edge and trailing need to be shaped. Adhere the balsa flat to the block and then sand away.

I would suggest that you dont treat this as a clg and use it as a hlg for indoor. You could then camber the wing (ie Coot) and the wing will flatten in the climb, then as the speed is bled off, the camber comes in, model slows and you may get longer flight times. However, weight is critical in these things.

With regard to the tailplane, I would take a bit of 1/16th sheet and sand it down to nothing and make sure it has some form of airfoil section. The most I use is kevlar thread round this to prevent runway and hanger rash.

Reinforcement question? Use Carbon tow as that would help a lot or spruce but at 8", its too small to be really getting any benefits. It will add weight.

I designed a model some time ago called "LETS ROLL"- plan is available on line. That's an 8inch model that has an incredible record and ability to thermal and can take the strength and stresses of a catapult launch. Have a go at that.

Hope that helps.

Kev
Do you have access to decent balsa? If not, I will happily knock up a couple of kits for you for Lets Roll and post as a gift.
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