Once again it has been a while, but I am now active on building the second of the three rockets in this project. God willing, the creek don't rise, and I don't run out of money, I want to fly it this September at LDRS in Argonia. There is a 50,000' waiver there, and this rocket sims to about 40,000'. I will be communicating with the team there to gain approval for the flight after the build is farther along.
At long last, I settled on a fin design based primarily on ease of cutting fins of equal dimensions. I do not have a CNC cutter so I have to do it the old-school way. In old school, you have to accept that perfection or near perfection is extremely difficult to achieve. However, if you strive for "uniform imperfection" you can still cut several fins to the same dimensions. The secret is to reduce cutting to a minimum and avoid making individual cuts.
In this case, the fins were "stack-sawed" using a table saw. The process is relatively simple. stack all the parts with common angles together and cut them all in one slice so that whether exact or not, all angles fins are the same dimension ... They are all equally imperfect.
Since I designed both booster and sustainer fins to have the same angle from the leading edge of the root to the trailing edge of the chord, I did not have to worry about cutting different angles. That meant I could cut the leading edge for all 8 fins with just one pass through the saw and just cut off the excess portion on the aft end of the sustainer.
I wanted a spare fin for each of sustainer and booster so i needed 8 total fins.
First thing to do was to cut four lengths of G10 that were as wide as the booster fins were "tall." Next, all four strips were carefully and tightly taped together. Then, after measuring 50-60 times, I made the one cut diagonal cut. After that cut, I taped up leading edges of the sustainer fins, marked the excess portion to be cut off, then after measuring 20-30 times, cut off the excess. In six cuts, I had 8 complete fins.
My initial goal was for the sustainer chord edge to be 4" long ant 1.75" high. The booster chord edge should be 5" long and 2.1875" high. The sustainer was almost an exact match. The booster fins were all 1/8" to short at the chord edge, however the most important dimension, the height, came in at 2.1875."
I fed these new dimensions into the sim and my simmed altitude changed by a couple feet
Here is the latest design and flight simulations according to Open Rocket. OR does not have the capability of factoring in a VK nose cone. RAS Aero does, and it suggests a 40,000' max altitude while OR suggests 38,000'. Both are well north of the current TRA Complex K record.