L2 Project: WM Drago 4 "EX-1127"

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HVArcas

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Oh absolutely, it is a freaking awesome motor. I was merely telling you what I would do with it. I have a damaged/rebuilt 4 inch rocket where downsizing the mount from 54mm to 38mm was part of the repair, and then a 2.6 inch / 38mm rocket that was specifically built for 38/1200s. it is not a "normal" case, at least not for me. Of course many folks who keep a nice bottle of wine around never think to open it up, so maybe flying a K1127 is its own special occasion and needs nothing else :)
 

Theory

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Time for some external fillets. Took the same approach that most do. Mixed a batch of rocketpoxy and added a little black pigment. As this sat (20min works for me) I cleaned everything with alcohol and masked off each fillet.
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Then to the rocketpoxy. Applied with some force as to work it into the joint
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Let that sit for another 5 min or so and pulled with a professional grade tongue depresser. Then promptly removed the tape
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Then touched up with a gloved finger dipped in alcohol. I think they came out ok. The one one the right, when viewed from the aft end is quite good. The one on the left is ok
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crossfire

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Fillets good good. I myself am always looking to do better. I want to try the cake fondant ball.
 

Theory

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Getting better. Three little air bubbles on the one side but those are easily to deal with. The lines are much better than the ones I did yesterday

One more set to go

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Theory

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Wrapped up the fillets and got the rail buttons installed (these will be removed for painting).

going to let the epoxy cure for 4-5 days before I start to finish sand and fill what needs to be filled.
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On to the electronics bay!!!!
 

crossfire

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Very nice work. What color are you thinking of?
 

Theory

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Thanks!

Something like this. The gray will be more of an aluminum silver and I will be adding some black accents and blue lettering courtesy of stickershock23

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Theory

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Switch / vent band


Marked the location WITH the bulkhead in place. Then epoxied with standard shop epoxy.
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Theory

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Lots of parts and lots of options. After a false start resulting in a complete redesign we are back at it.
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Cut the sled from 1/4 birch ply and used a hole saw for the reliefs on each side

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Dual 9volt batteries, dual switches, an RRC3 and RRC2+. The 1/4 all thread will be carried on either side of the sled via 2” pieces of 1/4 inch launch lug. Knew I kept those old LOC pieces for something!

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The charge wells are the 3oz units from rocket junkies as are the bulkhead pass through grommets. The eye bolts are 1/4 fully welded units. Should be enough but I can fit larger should I want. Even ordered them from McMaster-Carr.
 

HVArcas

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Lots of parts and lots of options. After a false start resulting in a complete redesign we are back at it.
What went wrong? Call me morbid but I love failure stories.
 

Theory

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Happy to share. In my original design I was going to have both switches mounted to the edge of the sled and the all thread more central. The idea was to “stack” the switch on top of each other so as to access them via the same vent hole. This would also “maximize” useable width (so I thought)

I was using some parts from a LOC sled.
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The issue was routing the wires for everything with the close all thread. Wasn’t laying out how I wanted. The space I thought I was gaining wasn’t realized

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So I came up with a “tent” made out of 1/4” bass wood and was going to mount one alt to each side

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No doubt this would have worked but I wasn’t really happy. As this isn’t a rush job I opted to step back and re-evaluate.

Very happy with the new direction
 

Theory

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Here we go. The launch lugs are in place. I sanded the “contact point” to flatten and promote bonding. Titebond II first then some little fillets with 5min.

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Also created the standoffs to mount the switches out of 1/4” bass wood.
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That’s all for today
 

Tim51

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Great build. One point - if using 9V batteries secured with cable ties I place them on the opposite side of the sled to the electronics. That way, if, for whatever reason, they come loose (hard landing etc) they don't crash into the altimeters. 4" Av bays and larger have a relatively large amount of space for things to move and wave around. Admittedly i's a belt and braces approach, but it happened to me once when the main failed to deploy. If your design calls for batteries and electronics on the same side, I suppose a battery box or some kind of other barrier would also help. Good luck with the cert.
 

Theory

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thanks Tim51

I am contemplating a fence behind them or simply using a quality double sided foam tape under the pair to provide enhanced friction. Along with the doubled zip ties that should be more than sufficient. I have the same set-up in my Caliber ISP and that has worked quite well.
 

crossfire

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thanks Tim51

I am contemplating a fence behind them or simply using a quality double sided foam tape under the pair to provide enhanced friction. Along with the doubled zip ties that should be more than sufficient. I have the same set-up in my Caliber ISP and that has worked quite well.
Most of time I have some kind of block to keep batteries from moving. The last thing I do is use electrical tape I go over the batteries and all the the way around the sled 2-3 times. That has never failed for me.
 

Theory

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Laid everything out and made sure the switches were accessible then shot it with a little paint. Going to let it cure for 48hrs, sand it then hit it with two more light coats

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Theory

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The paint was looking good and want sure I was going to get much better so I went ahead and put her together.

I prefer hard wiring the electric matches directly to the altimeters, so I opted for to use sealing grommets from rocket junkies for the pass-through in each bulkhead.

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mbeels

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I like that grommet idea. How does that work? Pass the ematch wire through the grommet and tighten down the screw?
 

Theory

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I like that grommet idea. How does that work? Pass the ematch wire through the grommet and tighten down the screw?
More or less. There is a metal plate with two holes that you glue in place. There is then a foam piece and a top plate. The top plate “squishes” the foam piece...

I’ll just take a picture
 

FMarvinS

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Your AV bay looks great. The gromets are interesting too; however, several of us use well nuts for the same purpose-not as neat but a lot cheaper. Good luck on the L2!

Fred, L2
ICBM, Camden, S.C.
 

Theory

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Decals arrived from stickershock!

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As soon as my bondo spot putty arrives I’ll get to work on finishing the fillets. Then off to paint
 

crossfire

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Very nice build. Where did you get the avbay eyebolts?
 

Theory

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drilled the locations for the sheer pins and also drilled a relief vent for the main air frame.

in looking at it all together I am thinking one 2-56 sheer pin to hold the electronics bay in the air frame and then two to hold the nose cone on the electronics bay.

one should be enough to prevent drag separation and the extra on the cone will prevent the main from being shaken out at apogee.

thoughts?
 

Handeman

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On the 4" I would do the same as on my 3", two 2-56 for the drogue end and three 2-56 for the nose cone.
Just my idea.
 

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