Thread: Build Log SU25K Frogfoot
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Old Apr 27, 2010, 11:38 AM
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The way to get smoothly flowing curves is to use long (lengthwise/horizontal), continuous strips of wood that run over several bulkheads. That way the natural bend in the wood will give you your curve, and the skin will be stronger because it's a continuous peice vs having a butt joint in the skin at each bulkhead. Stip planking is what it's called.

Why use strip planking? It's best used for a compound curve, a curve that curves in two directions, like often found on fighter's nose. As said before if your bulkheads are correct it will give you a natural curve from the bent wood, if you glue the strips correctly. If it's a simple cylinder, like say a roll of toilet paper, then bending big balsa sheets is easier that using multiple strips (less joints to sand).

What I would do in this case is run a straight, wide sheet starting behind your intakes (maybe to the next bulkhead behind the intake or wherever the side sheeting ends) and run it forward all the way to the nose (actually a bit longer by say 1/4 " to give you extra to work with). I would make lengthwise cuts in this sheet in the front to cut it into strips, running from the front end back to what I assume is bulkhead F3. So starts as a solid sheet in the back, and at the front the first third of it or so is cut into strips, which are STILL ATTACHED to the main sheet. Once you get the sheet glued to the bulkhead near the intake and F3 and whatever bulkheads are in between, you would wet the strips with water or ammonia and bend them inward to touch F2 and F1. You might want to clamp them down and let them dry before gluing because the balsa will shrink as it dries and the gradual bend my disappear (ask how I know this!). You may need to trim the balsa some because of the smaller radius of the nose, you might end up with very long and skinny triangle shaped sections trimmed out of the strips.
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