Bagging Ultralight Tails
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Home > Articles & Tips Index > Construction > Bagging Ultralight Tails

[Courtesy of Mark Drela, drela "at" mit.edu, April 2000]

For MHLG V-tails, 3" root chord, 5-6" semispan, I've used the following construction for a weight of about 3.5-4.0 grams.

Use a solid Spyderfoam core bagged inside a mold with 0.75 oz glass skins. 

Thickness is 0.13" at root tapering to about 0.045" at tip (4.5% airfoil). 

Glass is set at an angle of +/-25 degrees on the fixed part of the tails, and at an angle of +/-45 degrees on the ruddervators. 

Compared to plain balsa with sealer, this construction is a bit softer in bending but considerably stiffer in torsion, especially the ruddervators. It's also impervious to moisture.

I've recently used 0.75 oz glass bagged over solid light balsa for a light 2-meter tail. I used heavy 4-mil polyethelene bag, with the glass laid up inside the bag itself. No release agent is necessary. 

An extra glass strip is wrapped around the LE of the core before it's slipped into the bag between the glass. The surface is not quite as shiny as with Mylar, but it's OK and is much easier to do.

It makes a durable tail, but for MHLG this would be considerably heavier than the Spyderfoam method. For a 25 sq in tail the glass skin would add about 2 grams. If only I could find some 2 lb balsa...

-- - Mark Drela

 


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