We occasionally talk about papering fins- I took a few more photos during a current build. There are lots of ways to paper fins, with different pros and cons, this is just the way I've developed to do it.
I've usually got a rocket design from Open Rocket or from something I've drawn in CAD. I transferred my dimensions to a piece of graph paper and drew out the shape. I cut these out and trace around them onto a sheet of balsa and cut out the fins. My cutting is not perfectly accurate so I cut them a bit oversize.
After the balsa is cut out I trace around the balsa onto some scrap printer paper and cut those out, again the are cut out a bit oversize.
Working by myself I can't take good photos of the gluing step because I have to work fast. I lay one piece of balsa on a paper towel, put some Titebond II wood glue on the top surface and spread it around. Then I use my finger to wipe off most of the glue leaving a very thin layer on the balsa. I want to limit the amount of moisture on the fin because it will soak into the paper and cause it to expand and wrinkle. I work fast to try to prevent this but it doesn't always work. As soon as the glue is wiped off I put the paper on it and squeegee it down by rubbing over it with the edge of an old credit card. I immediately put the fin between 2 pieces of thin plastic, 2 pieces of smooth plywood, and clamp it all. Note that I clamp a medium tightness and this isn't a problem with most balsa but with small fins and relatively soft balsa it will squeeze down the thickness a little bit. From the time I put the paper on I try to get the clamps on as soon as possible to reduce the chance of the paper wrinkling. You can see the completed fins that have a good amount of paper hanging off the edges. These fins came out almost perfect. I will leave the first side clamped for at least 10 minutes then take it out and glue/paper the other side. Then I'll leave it clamped for half a day or so.
I use a sanding block to sand the edges and remove some of the excess paper. Angle the sandpaper at 45 degrees to the surface of the fin and take a couple of strokes with the sanding block to cut through the paper then the edges can be peeled off. I'll mark the edge of the pattern with felt marker then stack the fins with the pattern on top, pin them together with a couple of sewing pins, and use a disk sander to sand the edges down to the edge of the pattern.
I round the edges with the sanding block. Rough balsa is exposed so I paint a layer of thinned Elmers Carpenter Wood Filler on them. I'll also put some filler on the pin holes and on any other imperfection that I want to fill. Then I'll sand everything smooth with 220 sandpaper. The wood filler sands a lot easier than the paper but you can still damage the paper if you aren't careful. The edges of the paper will get some fuzzies. When I'm ready to start painting I'll spray a coat of primer on the fins and sand it lightly. This usually takes care of the fuzzies. If I see any imprefections I could do another round of filler and sanding but for rockets I'm going to fly I usually don't require them to be perfect.
I've usually got a rocket design from Open Rocket or from something I've drawn in CAD. I transferred my dimensions to a piece of graph paper and drew out the shape. I cut these out and trace around them onto a sheet of balsa and cut out the fins. My cutting is not perfectly accurate so I cut them a bit oversize.
After the balsa is cut out I trace around the balsa onto some scrap printer paper and cut those out, again the are cut out a bit oversize.
Working by myself I can't take good photos of the gluing step because I have to work fast. I lay one piece of balsa on a paper towel, put some Titebond II wood glue on the top surface and spread it around. Then I use my finger to wipe off most of the glue leaving a very thin layer on the balsa. I want to limit the amount of moisture on the fin because it will soak into the paper and cause it to expand and wrinkle. I work fast to try to prevent this but it doesn't always work. As soon as the glue is wiped off I put the paper on it and squeegee it down by rubbing over it with the edge of an old credit card. I immediately put the fin between 2 pieces of thin plastic, 2 pieces of smooth plywood, and clamp it all. Note that I clamp a medium tightness and this isn't a problem with most balsa but with small fins and relatively soft balsa it will squeeze down the thickness a little bit. From the time I put the paper on I try to get the clamps on as soon as possible to reduce the chance of the paper wrinkling. You can see the completed fins that have a good amount of paper hanging off the edges. These fins came out almost perfect. I will leave the first side clamped for at least 10 minutes then take it out and glue/paper the other side. Then I'll leave it clamped for half a day or so.
I use a sanding block to sand the edges and remove some of the excess paper. Angle the sandpaper at 45 degrees to the surface of the fin and take a couple of strokes with the sanding block to cut through the paper then the edges can be peeled off. I'll mark the edge of the pattern with felt marker then stack the fins with the pattern on top, pin them together with a couple of sewing pins, and use a disk sander to sand the edges down to the edge of the pattern.
I round the edges with the sanding block. Rough balsa is exposed so I paint a layer of thinned Elmers Carpenter Wood Filler on them. I'll also put some filler on the pin holes and on any other imperfection that I want to fill. Then I'll sand everything smooth with 220 sandpaper. The wood filler sands a lot easier than the paper but you can still damage the paper if you aren't careful. The edges of the paper will get some fuzzies. When I'm ready to start painting I'll spray a coat of primer on the fins and sand it lightly. This usually takes care of the fuzzies. If I see any imprefections I could do another round of filler and sanding but for rockets I'm going to fly I usually don't require them to be perfect.
