A note on forming fillets. It depends on the type of glue that you using as to whether or not you should pre-form the fillet to a concave shape. If you are using a glue with a volatile (evaporating) base, such as wood glues, you should _not_ preshape it. If you are using an epoxy, you should. The reason is this. With a volatile-based adhesive, the mass is reduced as teh glue dries. With wood glues, this is often 80%. If you pre-shape the fillet, 90% of the visible fillet actually provides no strength, since when it dries, it thins down to a layer too thin to provide actual strength. It is only in the very corner that you actuall get any gain. With a non-volatile adhesive, there is no shinkage.
I learned this when I learned correct window caulking technique from an engineer with a window manufacturing company. Many of the acrylic cauling compounds reduce by 50% to 60%. When appling a caulk, it is considered _critical_ to leave a large bead. This shrinks down to a concave fillet after a week or so, and provides the required strength.
If you want a wood glue fillet that is just in the corner, consider getting a glue syringe, and applying a convex bead that will shrink down to what you want, rather than a larger bead that actually does not provide the strength that is implied by the fin root surface that is covered.
I wrote an article on this for the Canadian Rocketry Association's magazine, "Earthrise" a year ago. If there is intrest, I can send a copy of the article by private response.
Leon Kemp
CAR S561 L3, RSO L1