I realize I am jumping in late here, but my un-brother Kevin is right. Weight is your enemy. My typical glider finishing consists of the following:
- Work up the wing and tail surfaces to the desired shape, dressing them down to smoothness with finer sandpaper, down to at least 400 grit. If the airfoil is hand-formed, get all the lumps and bumps out at this stage.
- Apply two coats of clear dope, cut 50% with dope thinner, to both sides of each surface. On raw balsa, it dries really quickly and you will be able to do both coats in a matter of minutes. You want to do both sides at the same time, and prop the pieces up on edge, because doing one side at a time can cause warpage. Often I don't even use a brush - a soft cloth or even Kleenex tissues works quite well.
- Let these parts dry overnight or thereabouts.
- Lightly sand with 400, then 600 grit sandpaper, to reach a high degree of general smoothness. Don't worry about the grain, you'll take care of it with the next step.
- Now here comes the tricky part. Cut out pieces of Japanese tissue and apply them to each surface, shiny side out. Make the tissue pieces with a margin about 1/4 to 1/2 inch on all sides. The tissue can be obtained at many hobby shops that cater to free-flight model aircraft folks, or online at peck-polymers.com. You'll use the same 50-50 cut dope both as an adhesive and a cover coat. Typically, I will start at the leading edge of a surface, applying dope in bands a half inch to one inch all the way across the span, then apply the tissue, stretch out the wrinkles and work out the air bubbles, and then move on to the next section, holding the tissue folded back until the next area has been doped.
- After you have finished an entire surface and have the wrinkles and bubbles out - I work them with kleenex - apply a light coat of dope to the whole side and wipe most of it off, sort of like applying stain to fine woodwork. Then apply the tissue to the other side of the same part immediately, in the same manner. As with applying the base coat, this is needed to keep the part from warping.
- When the flat surfaces are dry, trim back the edges and seal them down in a reasonably-aerodynamic fashion, again using the 50-50 clear dope.
- Let all the wing and tail pieces dry thoroughly (overnight should be enough), then lightly sand with 600 grit sandpaper and proceed to assemble the glider.
Many folks may differ with me, but on 3 and 4-panel dihedral wings, I generally cover an entire wing half as a single piece, then cut and bevel for the wing dihedral. I will admit that it takes time to learn how to do tissue well, but it adds a lot of strength and darn little weight. There is a distinction between "Japanese" and "American" tissue - the Japanese imported stuff is a little bit lighter - but both are available in several colors. Being red-green color blind, I use a two-tone scheme on my B/G wings a lot of the time - red or orange on the bottom, for contrast against the sky, and blue for the top, since it contrasts well against brown weeds or dirt, as well as most hues of green grass.
MJ
- Work up the wing and tail surfaces to the desired shape, dressing them down to smoothness with finer sandpaper, down to at least 400 grit. If the airfoil is hand-formed, get all the lumps and bumps out at this stage.
- Apply two coats of clear dope, cut 50% with dope thinner, to both sides of each surface. On raw balsa, it dries really quickly and you will be able to do both coats in a matter of minutes. You want to do both sides at the same time, and prop the pieces up on edge, because doing one side at a time can cause warpage. Often I don't even use a brush - a soft cloth or even Kleenex tissues works quite well.
- Let these parts dry overnight or thereabouts.
- Lightly sand with 400, then 600 grit sandpaper, to reach a high degree of general smoothness. Don't worry about the grain, you'll take care of it with the next step.
- Now here comes the tricky part. Cut out pieces of Japanese tissue and apply them to each surface, shiny side out. Make the tissue pieces with a margin about 1/4 to 1/2 inch on all sides. The tissue can be obtained at many hobby shops that cater to free-flight model aircraft folks, or online at peck-polymers.com. You'll use the same 50-50 cut dope both as an adhesive and a cover coat. Typically, I will start at the leading edge of a surface, applying dope in bands a half inch to one inch all the way across the span, then apply the tissue, stretch out the wrinkles and work out the air bubbles, and then move on to the next section, holding the tissue folded back until the next area has been doped.
- After you have finished an entire surface and have the wrinkles and bubbles out - I work them with kleenex - apply a light coat of dope to the whole side and wipe most of it off, sort of like applying stain to fine woodwork. Then apply the tissue to the other side of the same part immediately, in the same manner. As with applying the base coat, this is needed to keep the part from warping.
- When the flat surfaces are dry, trim back the edges and seal them down in a reasonably-aerodynamic fashion, again using the 50-50 clear dope.
- Let all the wing and tail pieces dry thoroughly (overnight should be enough), then lightly sand with 600 grit sandpaper and proceed to assemble the glider.
Many folks may differ with me, but on 3 and 4-panel dihedral wings, I generally cover an entire wing half as a single piece, then cut and bevel for the wing dihedral. I will admit that it takes time to learn how to do tissue well, but it adds a lot of strength and darn little weight. There is a distinction between "Japanese" and "American" tissue - the Japanese imported stuff is a little bit lighter - but both are available in several colors. Being red-green color blind, I use a two-tone scheme on my B/G wings a lot of the time - red or orange on the bottom, for contrast against the sky, and blue for the top, since it contrasts well against brown weeds or dirt, as well as most hues of green grass.
MJ
