Mega Der Red Max HPR and rharshberger style

I would like to reserve next 7-8 posts before starting thread, thanks to CJ I like doing my build this way with the majority of the build in the first few posts then the discussion afterwards.

After posting in the "What did you do rocket wise today thread" about this rocket I decided to do the build thread on it.

Photo 1: Airframe being wrapped with a single layer each of 2oz FG and 7oz FG, more for durability than any other reason, this almost double the weight of the airframe tube after priming.

Photo 2: Fins under compression, the lightening cut-outs were filled with left over balsa from the fins, then each side of the core received a single layer of 7oz FG using US Composite 635 laminating epoxy (its what I use for nearly all my rocket composite work).

Photo 3 and 4: airframe after priming and lathe sanding and filling with bondo spot and glazing putty, more still to be done after assembly.

Photo 5: Fins bevelled, using a 8" disc sander and Coker style jig ( see John Cokers great tutorials). The fins were also papered using self-adhesive label paper and the edges sealed with CA then sanded.

Photo 6 and 7: Fins, Upper Recovery mount and Chute shelf and rail button block, and assembled motor mount with T-nuts and block for rail button.

Photos 8-10: close ups of the motor mount motor retention system, I use the Kaplow style clips (screen door screen retention clips available from my local hardware stores Hillman fasteners section). The 8-32 T-nuts are inserted through 1/4" pilot holes pressed into place, they are taller than the thickness of the CR, the t-nuts are then removed, epoxy placed around holes and the t-nuts pressed back into place. Once the epoxy cures the t-nuts are sanded/ground flush with the face of the CR, then a 8-32 tap is used to chase the threads and the face of the t-nuts are re-chamfered to make inserting the screws easier. The t-nut spurs are actually bent over with a vise prior to sanding, I have yet to have a t-nut come loose. Motor mount is mostly assembled with TBII.

Photo 1: Airframe recovery anchor and chute shelf ready for installation. The eyebolt is 1/4" and the kevlar is 1/8".

Photo 2: Chute shelf dry fitted, the motor casing is a AT 38/720 and the shelf will sit flush with the top of the casing, I left myself lots of flying options everything from a G40 (no wind and 8' rail) to a I364FJ ( a J might be too much for the fins).

Photo 3: Parts for the Coker style nose cone AV-bay, I don't like to depend on motor delays for optimum apogee ejection so they get used as back-up and an RRC3+ does apogee primary duty. The sled is re-used on a number of my nose cone av-bays and is easy to move from one to the next, it was originally used on my L1 cert rocket (actually both Toys R Us Crayon Bank conversions).

Photo 4: mainly showing the location of the well nut for ejection charge e-match wire pass-through. The slot I cut in the pass-through hole is visible just on the edge of the hole on the left side of the well-nut, this keeps the well-nut from being hard to remove past the wire, and after tightening the well nut seals the hole and acts as strain relief for the wires.

Photo 5: Location of the charge well in relation to the pass-through, some of my charge holders have a hole near the bottom for the wire to pass out of the well when I use centrifuge tubes for pre-made charges. This charge well is made from .75" 6061-T? aluminum with a .625" hole.

Photo 6-8: demonstrating the pass-through set-up with wire.

Photo 9: Laminating the top of the Av-bay, eventually (tomorrow) I will pick up a 1/4-20 T-nut to make the removable weight system for the rocket, not that the sims so far show any weigh being needed.

Photo 10: assembled nose AV-bay prior to installation in the NC.




Edit: Forgot to mention that the MMT was uprated to a 38mm, originally looked at 54 but decided that that was overkill by miles and it was going to be a bit more difficult stability wise due to a short heavy motor at the tail end, the simmed nose weight seemed a bit excessive.

Photo 1 and 2: views of the AV-bay dry fitted into the NC, the brass pin is for alignment of the bulkhead plate that has the RRC3 sled attached, the brass pin is a piece of 1/8" brazing rod with the flux removed, a short piece is cut off then chucked into a drill press and groves cut in one end for CA or epoxy to form a mechanical lock on, the tip is chamfered prior to cutting off the main piece of stock.

Primed and ready for color coats, the paint of choice is Valspar Project Perfect from Lowe's, the colors are Classic Red and Gloss Black. The Valspar Perfect Project has so far been a great paint for me, it dries quick allowing me to recoat up to 3 times in an hour at 70F without orange peel or gatoring. I also installed the chute shelf/recovery anchor in it today so I could pre-drill the railbutton hole prior to painting. Nose cone was wet sanded, and the airframe was second coat primed this morning. The fillets were touched up with Bondo Spot and Glazing Putty along with any little nicks and scratches. The model should be ready for final color coats Wednesday evening, I have taken abit more time than usual with this kit just to make sure its well built and as durable as possible. Once the color coats are on I can get the final weight for sim purposes.

Post 5

Post 6

Post 7

Post 8, at this point the build is caught up, I forgot that TRF allows 10 pictures per post instead of 3 like my clubs forum host.

Very nice and detailed build thread so far. I like the layout. Can you please speak to the rationale for the av-bay tube in one of your next posts? I'm not sure what advantage that tube gives over just having the electronics in the nosecone without the tube, unless it is part of the design for the removable weight system.

Crash-n-Burn said:

Very nice and detailed build thread so far. I like the layout. Can you please speak to the rationale for the av-bay tube in one of your next posts? I'm not sure what advantage that tube gives over just having the electronics in the nosecone without the tube, unless it is part of the design for the removable weight system.

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The tube is part of the removable weight system, a 1/4-20 t-nut will be mounted in the forward bulkhead for the weights to screw in to. I could have pinned and epoxied an anchor into the nose tip but it would be harder to keep everything straight and uniform. The weights will be pretty standard across my MPR and HPR rockets.

rharshberger said:

The tube is part of the removable weight system, a 1/4-20 t-nut will be mounted in the forward bulkhead for the weights to screw in to. I could have pinned and epoxied an anchor into the nose tip but it would be harder to keep everything straight and uniform. The weights will be pretty standard across my MPR and HPR rockets.

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Thanks for the response. Makes sense to me.

Interesting build, lovely clear documentation as always. Did you cover the sled construction in another thread?

Tim51 said:

Interesting build, lovely clear documentation as always. Did you cover the sled construction in another thread?

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I'm not sure if the sled is covered in my Crayon Bank conversion thread (2015) or not. The sled is held in place by two pieces of 1/4" aluminum rod that I threaded on each end for 1/4-20 nuts, the rest is scrap baltic birch ply. I will try to get some pics of it broken down this evening.

rharshberger said:

I'm not sure if the sled is covered in my Crayon Bank conversion thread (2015) or not. The sled is held in place by two pieces of 1/4" aluminum rod that I threaded on each end for 1/4-20 nuts, the rest is scrap baltic birch ply. I will try to get some pics of it broken down this evening.

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Thanks I'd like to see that if you have the pictures to hand, especially like the look of the ply brackets the rods slip through.

Post #15 of the following thread has a better shot of the sled https://www.rocketryforum.com/attachment.php?attachmentid=260696&d=1428807559

The ply brackets are 18mm Baltic Birch with a dado cut for a piece of 3mm Baltic Birch to slot between them and everything glued together. The back of the sled has blocks for a 9 volt battery which is secured with two zip ties around the sides and a single zip tie around the ends. The zip ties are the reason the RRC3 is on 1/4" stand offs, to allow them to go between the altimeter and around the sled.

rharshberger said:

Post #15 of the following thread has a better shot of the sled https://www.rocketryforum.com/attachment.php?attachmentid=260696&d=1428807559

The ply brackets are 18mm Baltic Birch with a dado cut for a piece of 3mm Baltic Birch to slot between them and everything glued together. The back of the sled has blocks for a 9 volt battery which is secured with two zip ties around the sides and a single zip tie around the ends. The zip ties are the reason the RRC3 is on 1/4" stand offs, to allow them to go between the altimeter and around the sled.

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Thanks for posting that.

Primed and ready for color coats, the paint of choice is Valspar Project Perfect from Lowe's, the colors are Classic Red and Gloss Black. The Valspar Perfect Project has so far been a great paint for me, it dries quick allowing me to recoat up to 3 times in an hour at 70F without orange peel or gatoring. I also installed the chute shelf/recovery anchor in it today so I could pre-drill the railbutton hole prior to painting. Nose cone was wet sanded, and the airframe was second coat primed this morning. The fillets were touched up with Bondo Spot and Glazing Putty along with any little nicks and scratches. The model should be ready for final color coats Wednesday evening, I have taken abit more time than usual with this kit just to make sure its well built and as durable as possible. Once the color coats are on I can get the final weight for sim purposes.

Most excellent build!:dark:

blackjack2564 said:

Most excellent build!:dark:

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Thanks Jim, you are one of my inspirations on build techniques. Between CJ and JC (Crazy Jim and John Coker) I have learned lots on my re-entry/RE-BAR to rocketry.