I've been in rockets for a long time and the conventional wisdom was always for the grain direction of the balsa to be parallel to the leading edge of the fin. I never questioned this until now. I'm building a HiFlyer XL (because I found a pack of D12-7 in my gear!). The HiFlyer XL has long narrow triangular fins so the fin grain ends up almost parallel to the fin root. Well I'm not a structural engineer for real (a rocket scientist just for fun) and since the fin is trying to cantilever from the fin root, the fin grain should be more perpendicular to the fin root and not parallel to the leading edge.

Balsa is pretty weak in bending perpendicular to the grain direction, and since I couldn't re-cut the fins I came up with another idea. I papered the fins to give more strength in bending in that direction.

Papering is a whole nother subject. I've done it before and I've watched people do it on youtube. I put wood glue on the fins with a small paintbrush, then stuck on the paper. The paper sucks moisture out of the glue and wants to swell and wrinkle. I rubbed down some of the wrinkles with a putty knife and then flattened the fins with a heavy piece of tile. The few remaining wrinkles I will cover up with fill n finish. I had the idea afterwards that if I had somehow moistened the paper first I would not have had the wrinkle problem. Maybe hold the paper in front of a steam iron for a few seconds. If I do papering again I might try this.

Lots of ways to paper fins, but I use 65lb. cardstock (feels like heavy typing/printer paper). I brush fins with Mod Podge, then apply paper and press this sandwich between glass plate for 24 hours to prevent any warping. Use a few heavy books for weight on the glass to keep them flat and wrinkle-free.
If I want tapers on leading edge, I sand balsa tapers, and use a one-piece fin cover folded at the leading edge.
My covers are cut slightly oversized and I trim once they are removed from glass press.
I seal paper edges with thin CA to prevent lifting.
Then glue to body tube, fillet as usual, and prime and paint as usual.

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Lee Reep
NAR 55948

Projects: Semroc Saturn 1B, Ken Foss Designs Mini Satellite Interceptor
In the Paint Shop: Nothing! Too cold!
Launch-Ready: Farside-X, Maxi Honest John, Super Scamp

I’ve never used wood glue to paper fins - believe it or not my go to glue for papering is Elmer’s School Glue. Lay down a bead, spread with on old credit card, lay on the paper, use a clean card to smooth out the paper, layer between a couple of dollar store plastic cutting boards then weight with as big a stack of books as you can. Let things rest that way for a day or two until dry, trim/sand the edges clean, touch up any loose edge spots as needed. Sealing with thin CA is a good option but sometimes I forget until after I already primed so that doesn’t always happen. I’ve been papering my fins almost since I started my time as a BAR - going on ten years now...geez I’m old

All the papering jobs I've seen look like crap. There is no substitute for the old fashioned fill/sand method for a beautiful, long lasting finish. By the time one papers properly, one could have done it the right way in the first place. Papering doesn't like direct sunlight (heat), and it gets crappier looking with age. It adds very little strength. You want strength, wick CA into the woodgrain and sand, or use basswood. Don't give in to easy...it'll look like it!
Allen

Agree with Jetlag.
Papering fins looks like crap...ALWAYS and is a cheap/quick lousy substitute for PROPERLY finishing balsa.
If you don't want to fill balsa in the traditional way on fins, use R/C aircraft MonoKote/Ultracote.

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When in doubt, WHACK the GAS and DITCH the brake !!!

Yes, there is such a thing as NORMAL, if you have to ask what is "NORMAL" , you probably aren't !
Failure may not be an OPTION, but it is ALWAYS a POSSIBILITY.
ALL systems are GO for MAYHEM, CHAOS, TURMOIL, FIASCOS, and HAVOC !

Ok, from now on I’ll do my fins the right way...wait, no I won’t I’ll do it the way I like and not care how anyone else does theirs.

There’s an old vaudeville bit about a guy who keeps bees in a jar as a hobby. His buddy asks if he punches holes in the lid to keep the bees alive - the beekeeper answers “no, I don’t punch holes in the lid, so what that the bees die - it’s only a hobby!”.