Chris Rocket Supply Bomb Pop Build

Chris Rocket Supply Bomb Pop Build:

Well title says it all, I had it in my hands one week after I clicked buy, so I wasted no time getting the parts washed on the day of. Fortunately all my extra parts that I ordered all got here around the same time so now I can get to the business of building it.

I have to say it's high quality kit, really all you need is a chute, harness and a smattering of hardware. In all its a pretty good price for a 3" 38mm fiberglass rocket.

Here is the parts parts shot, and so far I have glued the harness loop to the motor tube. I plan on running a single separation cable cutter dual deploy, so the AV bay will in the nosecone. There will be some slight modifications to the body tube so I will have a larger bay attached to the nosecone.

I have already cut two inches off the tube and I will be adding it to the nose side. I like to have the extra room for altimeters and tracking electronics, but most of all I like to get my static air ports as far below the final transition of the nosecones as I possibly can.

This bad boy is going to fly the Loki 38 1200 loads so it's going to have to be tough.

TA

thobin said:

but most of all I like to get my static air ports as far below the final transition of the nosecones as I possibly can.

This bad boy is going to fly the Loki 38 1200 loads so it's going to have to be tough.

TA

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I put my vent holes right at the base of the nosecone. Works great. Thanks for doing the build thread on my kit !

You are probably right, I think I read it somewhere in a altimeter documentation, that it needs to be one body tube length from a transition, how much effect it really has I don't know. My Maggs holes are in the nosecone and it doesn't seem to effect it. Its is nice to have a little more room for different altimeter setups.

Here is the AV bay so far, my altimeter sled will extend a bit into the cone and the antenna for the tracker should have enough room in there to. I'm going to use the new Eggtimer TRS tracker/DD system and probably a second deployment altimeter for a backup.

I'm going to run some OP Rocket sims before I screw the tip back on I may add some weight at that point if need be. Although I might just leave it off till it is painted I like the raw metal look.


TA

Looking good! The only thing I would of done different is to put a 54mm instead of the 38mm motor mount. I like your altimeter bay setup.

jus_rockets said:

Looking good! The only thing I would of done different is to put a 54mm instead of the 38mm motor mount. I like your altimeter bay setup.

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I'm working on that.

thobin said:

You are probably right, I think I read it somewhere in a altimeter documentation, that it needs to be one body tube length from a transition, how much effect it really has I don't know. My Maggs holes are in the nosecone and it doesn't seem to effect it. Its is nice to have a little more room for different altimeter setups.


TA

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I think it only affects the altitude accuracy.

tbonerocketeer said:

I think it only affects the altitude accuracy.

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It would be good to be careful if your altimeter vent holes are close to the nosecone. I have a flight (in the pic) where there are three vent holes into the nose cone shoulder located perhaps an inch below the top of the airframe. The altitude data look pretty messy. Obviously, the apparent altitude drop would spoof some altimeters. I only fly this rocket using altimeters, like the MAWD or HA45, with a hardware Mach lockout, although acceleration-based apogee detection would work too.

Jim

It will be roughly 3 inches below the transition.


TA

JimJarvis50 said:

It would be good to be careful if your altimeter vent holes are close to the nosecone. I have a flight (in the pic) where there are three vent holes into the nose cone shoulder located perhaps an inch below the top of the airframe. The altitude data look pretty messy. Obviously, the apparent altitude drop would spoof some altimeters. I only fly this rocket using altimeters, like the MAWD or HA45, with a hardware Mach lockout, although acceleration-based apogee detection would work too.

Jim

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I've seen that very shape as well with a minimum-diameter 38 that had the vent hole right at the base of an elliptical nosecone.

jus_rockets said:

Looking good! The only thing I would of done different is to put a 54mm instead of the 38mm motor mount. I like your altimeter bay setup.

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Thanks, I almost went with a 54mm change but the reload cost and our waver limit would keep me around a J class anyway so I didn't see the point. Sounds like it will be an option soon.

I didn't get to work on the rocket today, didn't get home from work till late and I just had enough time to eat and then run out to our club meeting.


TA

I installed the motor mount, I just made it flush with the bottom of the air frame, it was easier that way so I could just set the rocket down on the table while it dried. It was a little tough to get the bottom centering ring out so I could get to the fins later, but a bit of poking at it through the fin slots did the trick.

After that and a quick sanding of the fin edges, I tacked them in and gave a nice fillet to the sides of each fin on the motor tube. I'm gong to use a slimline retainer so I had to notch the fins about a quarter of an inch to get the rear centering ring back a bit so it would fit.

I drilled a few random holes in the collar of the AV bay and epoxied the crap out of it and the nosecone, the holes will act like rivets let the glue through to help lock into place. I left the metal tip off till I can get it painted, going to have to find a long screw driver to get it back on when it's done. :duck:

I love single separation dual deploy so much less of a hassle in the long run, and not any harder to build it as such. Costs less too; I think I only have one rocket left that I have yet to convert to single separation DD. You do have to plan your layout of your AV bulk head a bit better but so far I have been able to get the redundant DD all on one side.


TA

thobin said:

Thanks, I almost went with a 54mm change but the reload cost and our waver limit would keep me around a J class anyway so I didn't see the point. Sounds like it will be an option soon.

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You can get some very nice 2 and 3 grain 54mm J's that shouldn't bust your waiver and cost as much as a 38mm J. Then you can always use an adapter and load a 38mm motor. Benefit of using 54mm J's is that they are a lot shorter in length and can give you some cool options. Plus you have a much wider selection of the type of burn you have. Most 38mm J's are generally high thrust, shorter burn. I like them, but sometimes a longer burn is nice. I like flying a CTI J140 because it gives me a slow launch and burns forever.

True, I was only thinking from a Loki motors stand point, so I take that comment back.


TA

Started on the external fillets should have most of it dont today. It takes about 2 hours for the epoxy to set so it wont move. Sure love the Jaw Stand you can even use the built in level to make sure your fillets stay nice and even.


TA

Well its all done but the paint. :headbang:

Newest addition to my fleet the rocket and motor she will fly on the Loki 38mm 1200. She'll make point five past the sound barrier. She may not look like much, but she's got it where it counts. I've made a lot of special modifications myself.


TA

thobin said:

Started on the external fillets should have most of it dont today. It takes about 2 hours for the epoxy to set so it wont move. Sure love the Jaw Stand you can even use the built in level to make sure your fillets stay nice and even.


TA

Click to expand...

Can your jaw stand be bought on the web?

Yup. Jaw Stand

Best launch pad / rocket holder out there.




TA

Gotcha. I was thinking it was a dedicated fin alignment jig.