Mopzilla

I'm building a stealth sport, and as per the instructions I've glued the long block of balsa to the front as the leading edge, but how do I contour it evenly? I'm afraid that if I did it manually it would turn out uneven.. is there an easy way to do it?

Thanks!

fireman7875

My Feedback: (7)

I use a razor plane. This allows me to remove a little wood at a time and keep it pretty uniform the whole way across. Use caution though; as you approach the end of a stroke you may have a tendency to use a heavier hand (I do for some reason). That will leave you with a tapered leading edge... not a good thing. After carving just sand to a smooth finish. Piece-o-cake!

BMatthews

Close is often good enough if you have an eye for shaping. Wrapping your finger around the job creates a shadow line you can use to tell the shape. And a stick or ruler used to cast a shadow also works well. Use a small table lamp with a clear bulb and no shade for the light source so it casts a sharp shadow line.

Another method is to make up a little reverse template from 1/32 plywood and use that as a guage for shaping the leading edge. This outside template should be long enough that it follows the rib back a fair ways to the first spar or other shape so that there is no doubt that it's back far enough so you know the shape is right. Razor plane or coarse sand off the worst and switch to 120 grit for most of the rest and then 220 when you're close. Just work it all over until it's close and then work a foot or so checking often with the template and vary the sanding pressure and strokes to work the higher and fatter spots and leave the closer spots alone. Check often and vary the stroke pressure and placement as needed to work it down until the template fits well overall.

As you work with the template also use the finger shadow trick to see how you're doing. After a few wings you won't need the template for any except the most critical types of wings.

Big Al-RCU

Know what you mean, I have no freehand ability whatsoever; so have had to improvise over the years.

Try this. Before you start to round the block, using a long straightedge, draw a straight line full length down the center. It’s easier while the block still has square edges. Depending on the shape of the LE radius, draw another line (or lines) on either side of center. Now using a razor plane and a long (11 in) sanding bar cut a series of flats right up to the lines you have drawn. The final shape should be ‘boxed in’ at this point by a series of flat surfaces. It is a lot easier for me to ‘eyeball’ a flat surface than a rounded one. Then and only then do I sand off the sharp edges to the final rounded shape. It’s almost a cinch that it will come out true at this point. Minimizes the freehand skill to just knocking off the sharp corners. And by cutting to the pencil lines you will end up with a truly straight LE in spite of the usual warps and wiggles in most wood.
Hope this helps,
Al

DesignMan

One trick I use is in the final sanding stage. I get a long piece of paper and "shoeshine" sand the leading edge. The tension in the sandpaper will even out any hills while missing all the valleys.

Basically, grip the wing between your knees and lap, and, holding one end of the paper in each hand, pull it back and forth across the axis of the leading edge. The action is VERY quick, so don't get agressive on the grit you use. I usually start with 220 for the first few licks, then 320 and 400. Humming a bluegrass tune while you work seems to help.....

combatpigg

My Feedback: (3)

HI MOPZILLA, It's good to work with a bright light that can cast a high contrast shadow onto your work. The longer you make your sanding blocks, the more even will be the final product. A block that is as long as a standard piece of paper is good enough for me, use 3M 77 to attach it, and a heat gun to loosen the glue when it's time to change paper. If you use your blocks on balsa only, they will last forever. With balsa you have to watch what you are doing and check your progress every few swipes.