This is a 159% upscale of the popular Estes kit Der Red Max. This is a simple to build rocket that performs very well on the 24mm reloads available today. All the parts are readily available as well including the decals.
High quality balsa nose cone, plywood ring, and eye bolt were supplied by Sandman. Estes BT-80, 24mm heavy duty motor tube, two lite-ply centering rings, fins are 3/16" balsawood, Kevlar® shock card, and motor retainer hardware. Excelsior provided the awesome decals.
I constructed the motor mount by using a BT-50H motor tube that was 4" in length. On the bottom centering ring, I installed two #4-40 blind nuts for the motor retention bracket. The light-ply centering rings were mounted a 1/4" from the top and bottom of the motor tube. I created a nice epoxy micro balloon fillet on both sides of each centering ring for strength. I drilled a 3/16" hole in the top centering for my 1/8" Kevlar® shock cord to go through. The Kevlar® shock cord ties around the motor tube between the upper and lower centering ring. I cut a BT-80 to the length of 13.5". I hardened each end of the BT with thin CA for strength. The next step was to I fill the spirals. After sanding the BT, the tube was marked for the fin locations and the launch lugs. The bottom launch lug is flush with the bottom of the BT. The upper lug is 4-3/8" from the top of the BT. Each launch lug was 3/16" diameter and 9/16" long. The motor mount was glued into the BT using wood glue that created a nice fillet around the top centering ring. A wood glue fillet was also created around the bottom centering ring. The fins were cut from hard 3/16" balsa and shaped. The fin and launch lugs were glued on with epoxy. Once dry, epoxy micro balloon fillets were created around the fins and launch lugs.
The fins and nose cone were sealed and hardened using two coats of Minwax Polyurethane. Once dry they were sanded smooth and coated using thinned spackle that was brushed on to fill the wood grain. The filler was sanded off and the rocket was primed with two coats of Duplicote High Fill primer sanding between coats. The nose cone was painted black using two coats of old formula Krylon spray. The body was painted metallic red using two coats of Rustoleum spray. Once dry the body was smoothed using super fine steel wool. Once clean and dust free the body was shot with two coats of Rustoleum clear. It was really cold during the painting process for this rocket, but the results were still acceptable. To finish the model, the decals were installed. Overall it looks fantastic.
I designed this model to fly on the 24mm reloads such as the E18, E28, F24, or F39. The first flights I used a E28-4 and it worked perfectly. The first boost was nice and straight with no stability issues. The E28 produced a very respectable altitude. The 24" parachute worked good but a little too slow to bring it down. A smaller chute or a spill hole would be required for windy or high thermal activity days.
Since the fins on this upscale start to get large, I would use the through the wall method next go around. Although I feel very good with my method to attach fins and strengthen them with fillets, TTW is king.
This is a very easy rocket to upscale but is a rewarding project. The Der Red Max is a classic that flies great up or downscaled. In addition you can't find a cooler set of decals on a rocket anywhere.