I guess, like a lot of things, it depends on what you're doing. I've laminated only one rocket's fins before, so I wanted to pick the brains of those of you who have done this more.
The one that I did was a Quest Zenith II that I flew (and lost to high wind) at NSL this year in Hearne, TX. I sanded the fins together, then rounded the leading and tip edges and tapered the trailing edge. I was trying to do as close to a true airfoil as I could, complete with thinning the fin as it went from root to tip. It worked out pretty well for a first attempt with nothing but my hands and a piece of sandpaper. Next, I applied a spray adhesive and papered the fins with 20 pound copier paper, folded over the leading edge. Finally, I glued the fins on and filleted them (all with yellow aliphatic glue). I didn't weight the with anything while laminating them, and the edges were ragged and didn't stick to the fins well, leaving gaps.
I'd like to do better next time.
How's this for a technique? Pick it apart, give pros and cons, make suggestions, hold nothing back.
1.) Sand fin edges, while holding them together, to get the starting shape and size the same.
2.) Round the leading and tip edges, taper the trailing edge, and round the edge-to-edge corners slightly.
3.) Carefully remove all sanding dust.
4.) Apply a thin (fin-wide) strip of masking tape along the root edge of each fin to try to keep spray adhesive and tissue off of it.
5.) Cut out some pieces of Japanese tissue so they can be folded over each fin's leading edge and overlap all the rest of the edges. Make a few pencil marks on the tissue, so I'll be able to see quickly where to place the fins on it later without having to think about it.
---Steps 6 and 7 for one fin at a time---
6.) Lay the tissue open again, and spray it with 3M Super 77 adhesive.
7.) Lay each fin onto the surface of the tissue, and grabbing it by the edges, fold it over the leading edge, trying to keep it tight and wrinkle free.
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8.) Place the fins between sheets of waxed paper, and press them between stacks of old catalogs, magazines, newspapers, or some other heavy but flexible items. [Could also put foam rubber sheets on each side and weigh it with books, bricks, or whatever.] Leave them overnight to bond as well as possible.
9.) Remove the masking tape.
10.) Lightly sand and/or trim away the excess tissue hanging over the non-leading edges.
11.) Glue the fins to the rocket, and fillet them. Wait for this to fully cure/dry.
12.) Apply water thin CA to all fin edges, soaking the edges of the wood and tissue alike. This is to toughen the edges and help the tissue to stay bonded. [Could CA the whole fin surface, if that would be an advantage. Have to do it outside with a fan blowing though.]
Critique? The CA would make the sanding more effective if done before the edges are shaped, but would that make the paper attach less thoroughly?
How would the technique differ if I was using plywood instead of balsa? G-10? Is tissue strong enough to help plywood at all, or is that more a job for fiberglass or carbon fiber?
What is best to reinforce fins with? Pros and Cons of each? Weights of cloth to use?
I have access to carbon fiber fabric (0.32 or 0.032, can't remember which, per square yard) at one square yard for $16. Is that a good deal? Does carbon unravel too easily to be worth the trouble of using on medium power rockets?
Etc. Educate the new BAR who's never flown anything larger than a single Estes D but has a new LOC Graduator in a box and an itch to move into medium power and possibly even build the Graduator to H-power strength for an L1 attempt.
Thanks all!
P.S. Just noticed that the previous post was by our fearless leader! Good forum when the NAR brass is here.