I find these builds by yourself, CJ, etc. inspirational!
Disclaimer, I've never built nor even seen one of these kits in the flesh but I'm curious: if you had left the fin tabs closer to full length back in post #72, would that have lessened the issue you experienced with the injected epoxy leaking out at the body tube / fin slots?
If the external fillets are going to extend up the exposed surface of the fins anyway, was it really necessary to remove some of the fin tab to bring the bevelled portion of the fins closer to flush with the body tube?
Great question and very fair point.
For the question about the impact of the fins being above the body tube, in all likelihood, the portion that was proud of the body tube probably would not have caused any issues for most flights. You are right that I could have most likely built up a bit of a "ramp" with the external fillet and been fine. There are a few reasons I chose to correct the issue:
- In theory, the 1/4" sticking above the body tube could increase turbulence along the fins. Not much of an issue at sub-sonic flight speeds, but I do plan to fly this rocket above Mach 1, so any opportunity to keep the fins streamlined is a good one. In the same category, I chose to install both 1010 and 1515 rail buttons, but they are removeable. I will make a field call as to which I will use per launch and remove the unused ones for each flight to decrease turbulence along the tube.
- I have built a lot of rockets (not as many as a LOT of people on this forum, but definitely a couple hundred over the past 40 years) and part of me just can't let a small thing like that go. Call it OCD. I figure, if I am going to pay $200 for a kit, I am going to take the time to get it right.
- At the end of the day, it was an easy fix. 10 minutes with a chop saw and belt sander and Bob's your uncle.
For the leaks, I don't think it would have changed my oversight. It wasn't the length of the tabs that caused the leak issue. If you look at posts #74 and #76, you can see that they tapered the fins all the way down into the tab, almost to the root edge. So, it would not have mattered, the taper would have still been there all the way down. It was just my oversight not to see the gap left by the tapered edge.
I should have been more clear on the leak. The ends of the fins were epoxied securely to the CRs, but the end of the fin slot is rounded and the taper of the fin makes a gap in the fin slot/fin taper, so the epoxy leaked out at the end and ran down the tube and down the fins that were below the section I had injected. When I inject the epoxy it is room temperature, but I put the rocket in a "hot room", about 100 degrees F, to cure. So, when I put the rocket in their last night, I didn't see anything leaking out, but when it got warm, the epoxy spilled out the end gaps.
Easy fix, just seal the gaps at the tapered ends with some more quick cure. I already injected the second section and watched it closely all morning, no more leaks.