3" nose cone with avionics bay

I needed to add 22 oz of lead shot nose weight into Der Red Mix's nosecone today but only had one ($30 spendy!) tube of 3M DP 8005 adhesive. It's the only material I know of that will stick stuff to polyethylene at room temperature. [Maybe I'll try this much cheaper stuff next time]. Once you pop the adhesive tube open it also doesn't store well so I planned to use it all today. This forced me to start another project that's been sitting in my mind recently to best use the 8005.

For some time now I've had this Public Missiles Ltd. screw-cap assembly (search the page for RETAINERCAP) for their CPR3K electronics mounting system. I've been wanting to put that on a length of 38mm tubing and place the whole thing into 3" nosecone to enable electronics in a stubby 3" rocket w/54mm motor mount. That came together quite easily today and here are the progress photos.

Here I've used my bandsaw to cut off the mounting features from the nosecone base, cut a 38mm hole, and six outer holes through which to thread the Kevlar™ mounting cord. I think this pattern should add margin to an already pretty tough structure:

Here I've test-fit the retainer cap assembly on the length of 38mm BlueTube.

This shows the relative length of the two parts. The tube seats perfectly in the narrowing region of the nosecone interior:

This is what the assembly will look like when prepped for launch:

Here I've dumped 7 oz of lead shot + 8005 adhesive into the nose tip, added more 8005 to the interior, placed the tube down in there, and more 8005 at the tube/base/cone interface to hold it all together:

Everything's curing overnight now.

Der Red Mix's attractive derriere. Oui, no?

I JB welded all the motor retainers on last night then dumped in a layer of West Systems epoxy + white pigment on the bottom plate to improve the aesthetics... at least before the first flight chars it up!:

I also finished the fin fillets and mounted the rail guides today. She's just about ready for finishing but I need to decide if I mount the hinged door before or after finishing. Decisions decisions.

Der Red Mix - fins in place

Today I coaxed the final fin into place and it's curing now:

All that's left construction-wise is to JB Weld the motor retainers in place, drill the rail guide holes, load the nosecone tip up with 22 oz of lead shot and epoxy, and tether up the recovery system. Cool! Oh but then I need to fill, prime, sand, fill, prime, sand, fill, prime, sand, fill, prime, sand, fill, prime, sand, fill, prime, sand, fill, prime, sand, fill, prime, sand, fill, prime, sand, fill, prime, sand, fill, prime, sand, fill, prime, sand, fill, prime, sand, fill, prime, sand, fill, prime, sand, fill, prime, sand, fill, prime, sand, fill, prime, sand, fill, prime, sand!!! Dammit!

All work and no play makes Jack a dull boy...

Der Red Mix - fin reinforcement time lapse video

I sped this video up roughly 50x so as not to bore you. The fins turned out pretty well. They were initially fairly warped so I took them to work and placed them in an environmental chamber at 30C/80%RH to rehydrate the over-dried plywood. As I depleted one partial roll of 6 oz. carbon fiber fabric I decided to dip into my Kevlar/CF hybrid roll for the final 2 of 6 fin swatches. I should have used three Kevlar/CF swatches but this was a last thought for durability:

Oh and, once cured, the fins were surprisingly difficult to separate despite the use of vacuum film between each fin. The resin content is quite lean so the technique worked and I'll use it in the future.

Leaps and bounds

All of a sudden this thing's really coming together. I cut all the airframe holes tonight and everything's piecing together peachily:

Despite all my Illustrator pre-work and all the iteration I still managed to aim the camera basically down a fin. It's a 16:9 aspect ratio camera and it's focus is fixed below the fin but still. Duh. The final motor tube/e-bay assembly's curing now. Tomorrow night I'll reinforce the fins and epoxy the entire booster together when that's done. I really need to complete the construction soon because I want this to be super glossy when painted and I have all those awesome Sticker Shock decals to apply before LDRS...

Now featuring even MORE progress

Yesterday I added one wrap of 6 oz. fiberglass to Der Red Mix's main airframe using Dave Triano's technique. This is mainly for aesthetics and secondarily for durability. It's very difficult to apply excess resin to this much area so there are many gaps in the otherwise glossy finish. It's also tough to apply adequate hoop stress on the 14 mil Mylar™ film so that didn't help this surface defect either. It'll finish up nicely anyway so I'm still happy with the result:

Here also are some studio shots of progress on the electronics bay and I think they better convey the final layout. This whole assembly will be epoxied into the above airframe after I cut fin, e-bay door, and video camera slots into it:

Construction progress

I continue to make progress on Der Red Mix's electronics bay and motor tubes. Right now I only have e-bay pix, however, so here they are:

The Flip MinoHD camera fits nicely through the side and I have room for both Parrot 2 and Raven altimeters + 2 9V batteries on that removable G10 board. I'm also working on the hinged door for the front and a simple plywood cowling to reduce drag on the dangle-cam.

I also finished building my Madcow Squat for the drag race at LDRS 29. Now I just need to finish and paint that puppy and it's all set:

Der Red Mix tube session and test fit

Tonight I was inspired to drill the extra holes in all four centering rings, cut the motor tubes to length, and mark them precisely according to the plan a few entries below. Everything went together nicely but before I apply any epoxy I realize I need to finalize the electronics bay mounting board first.

You'll notice that I've elected to dual-attach the shock cord on the upper plate. I think this should reduce the tendency to zipper as the load will be divided in half. I'm quite sure the Gates Brothers used to employ that trick. Also that single aluminum tube bridges the electronics bay to the motor area and will facilitate e-match wire transport. Hopefully this week I'll get this whole assembly done and the rest of the build should prove fairly trivial. I think the first flight will probably be a central CTI 1596K500 Red Lightning motor on the ground then air-starting 2 x 408I345 White Thunders. Niiiice!

Viciously Mean Machine 0.75

I'm still working on the full 48" payload for the 100% Viciously Mean Machine but, in the mean time, I bought a Performance Rocketry aluminum-tipped, carbon fiber, conical nosecone and it just looks bad ass with the shorter payload. That booster will fit a CTI 6GXL casing so I hope to fly an L935 in there soon.

[I corrected the lens distortion present in the other version of the image.]

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