Hi Jowayen,I prefer to use thin epoxy.
Before I place the rocket horizontally to dry, I like to run/pour/inject the epoxy down the root where the fillets will be.
I'll do 4 at a time, let dry, rotate 90 degrees and run epoxy down 4 more fillets... until completed.
I'm not extremely concerned about a "perfect" all-matching radii. It's just not that critical.
The purpose is to widen the bonding width of the adhesion surface.
Preparation of the surface is by far the most important step of the internal fillets.
View attachment 459097
The fillet Jim is referring to is (I believe) the middle set on the inside of the body tube to fin. Those are not as necessary. And NOT in the Wildman instructions. Internal fillet to the motor mount and external fillet on the outside of the body.Hi Jim! Thanks for your comment. Based on my experience, internal fillets are the first to give way, which would seem to indicate that they are a key stress point. I've been flying rockets for more than 65 years. Wildman voids his warranty if you don't have internal fillets. I'll keep the internal fillets.
The red dots were just a quick sketch from power point showing the location of the 4 places I epoxy at a time. I do pretty much exactly what DR WOGZ describes in post #34. Get some "thin" epoxy. Apply to each of the 4 places shown. Tip the rocket back and forth a few times until the epoxy starts to level out and begins to set up. I don't go back over them at all. It's just enough to make the epoxy joint/bond joint wider. I'm really not interested in a perfect radii. I try to use the same amount in each area for peace of mind with regards to balance. Also, on mid power rockets, I'll use nothing but tight bond 3. High power gets epoxy.Hi Jowayen,
I have this question about your method, please.
Does your thin epoxy, which you illustrate by means of the red dots, replace the fillets, or do you use the thin epoxy and then apply thicker epoxy to further build up the fillets?
I inject internals, and i overbuild, that way when a coupling un does itself and my booster free falls from 800 feet i can just pick it ip and fly it again...Yeah, this is a perennial question: how much is too much overbuilding? Since we don't know the exact properties of the materials we use nor the exact stresses they will encounter, we're always using our judgement. To me, skipping fillets to save time isn't not overbuilding, just taking a shortcut.