Fin Painting 21 May 2021
Plan for fin painting is 4 coats of Rustoleum 2000-degree high temp paint as a base followed by 2 coats of standard black paint and then the blood splatter. This is all really just a cool looking ablative and I don’t expect it too look good after the flight but it should serve its purpose. At least one hour was allowed to pass between all the coats and the last coat of the standard black paint was allowed to dry overnight to reduce the peeling risk when taping for the splatter. To create the splatter look I used some water based hobby paint from Hobby Lobby and a cheap art brush. I got some paint on the tip of the brush and swung/flicked the brush toward the rocket. You can find good videos on how to do this on YouTube and with a little practice it is very easy. To create some smaller droplets I ran my thumb along the brush like a toothbrush. Here is the final result pre clear coat. I plan to use a 2-part epoxy spray clear coat to make it as durable as possible. The clear coat will be applied after the NC is complete and pained as well.
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While I am waiting for the hardware to get here (Next week hopefully) I am prepping as much as I can. Today I secured the eyebolt in the FWD end of the Aeropack MD retainer that I previously skeletonized. I did this in 2 steps. First, I sanded the contact point between the bolt and the retainer and then wiped it down before applying superglue to the contact surface and threads. I then used a metal rod to tighten the bolt very tightly into the retainer. After the bolt was secured I used a small engine tube I had laying around to made a “mold” around the bolt. I surface prepped the area and then poured in RocketPoxy to act as further “Don’t have a bolt back out and ruin my L3” insurance.
After receiving the motor hardware and checking the fit/marking the location in the airframe the retainer installation began. The skeletonized retainer was prepped with acetone and alcohol. The airframe interior surface was prepped using 60 grit and 220 grit sandpaper and then wiped down with acetone and alcohol. The retainer was threaded onto the FWD closure of the motor hardware using an old avbay lid as a spacer. This spacer insures that the motor thrust ring will seat against the aft end of the airframe (won’t run out of threads). Rocketpoxy G5000 epoxy was used for the bonding and the assembly was set at a 5 degree decline (aft end high) to ensure no excess epoxy moved onto the motor case. The excess epoxy on the FWD end of the retainer was removed with a squared off stir stick and gloved finger. The spacer was removed after the epoxy cured and the final length of coupler that will sit in the airframe is 5.75”.
After the Avbay prototyping discussed above the final aluminum mount ring was ordered and after final fitting was epoxied into the NC using JB weld based on possible high temperatures due to Mach heating. The aft surface of the mount ring is approximately 4.25” from the aft end of the NC.
AvBay Sled Assembly 27 June 2021
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The final versions of the Avbay sled base and mount ring were ordered from SendCutSend and are made of titanium and 7075 aluminum respectively. The Single all thread sled was 3D printed by Additive Aerospace and is a prototype of a product they are developing. After some final adjustments to the fit the CO2 systems, wire retainers and connectors were attached to the sled base. The connecters and wire retainers are epoxied in place with JB Weld 5 min epoxy. The CO2 systems are screwed in place and use electrical tape as a “gasket” on the upper edge of the bottom flange. The taped hole just above and to the right of the right wire connector shown in the right picture above uses an 8-32 hex head screw to help attached the base to the mount ring. The forged eyebolt and cotter pin are the primary load bearing components but the 8-32 screws help to seal the AvBay and aid in resisting rotation.
