Magnum Hornet Payload Bay Question

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Well-Known Member
Jul 2, 2017
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Hopefully an easy question for the hive-mind:

I am about to pull the trigger on a Magum Hornet and I plan on modding it ever so slightly by adding a payload bay for a micropeak altimeter. (Yes, I know I could just grab a Jolly Logic and make my life easy, but where's the fun in that?) I also plan to put an ejection baffle in it.

The rocket itself is 19.5", the nosecone is about 5.5", meaning the rocket body should be 14" long. The motor mount is 3.25" and the ejection baffle is 2.75", with about a 1" gap between the two, that's 7" of space used up, leaving me 7" to play with.

I'm roughly estimating the payload bay to be about 3-4", mainly due to tube coupler and nose cone shoulder length. I'm assuming (and we all know what happens when you do that) that the MicroPeak can lay flat and will not require a lot of length in the body tube) This means I also have 3-4" of space for the shock cord and 'chute inside the body tube, making it awfully crowded, awfully quick, especially if I'm using a 4" streamer (yes, the Apogee website got me on that one!)

Sooo, the question is: If I cut the main body tube and use the upper portion for the payload bay, will I have enough space for the parachute/streamer? Or should I just bite the bullet and and buy another body tube, cut that, and lengthen the rocket a bit? My gut is telling me to play it safe and just add a bit of body tube but that's another $10+ to a build that's already getting out of hand because I can only find tubes in bulk....not that I wouldn't eventually use them for something.

Another option I thought of is chucking the balsa nosecone it comes with and replacing it with a hollow plastic nosecone (will probably do this regardless of payload bay solution), cutting off the base, adding a bulkhead, and turning the nosecone shoulder into the payload bay. I'm not 100% sure how I would accomplish this yet, though.

Thanks for any input. Also, feel free to tell me this whole plan is stupid if it sounds like it is haha.
May have to go back to the drawing board on the MicroPeak since everyone seems to be sold out. I preferred that over the firefly for it's logging capability but either way I go, it'll be a fairly cheap one since this will be my first time messing with electronics.
Your post brings back bad recent memories for me. I made a BT-55 home made rocket with a Estes Booster 55 as a fin can and the dimensions were about the same as this rocket. It flew with my Jollylogic 3 in a cargo bay. On a D12-7 it almost left my sight, and then there seemed to be a chute deployment issue and I lost track of it. (Huge field) I went out and looked but never found it. Ruined the whole day. So I can appreciate your concern for losing the electronics, and it is valid.

I basically grounded the high flying little rockets until I get my HAM license and can buy a cheap $35 RF tracker or a Altus Metrum Telemini V3. On it's replacement that I built (which does have a baffle) I am putting this reflective stuff I got at a hobby store that is a mirror finish on the fins.

Oh, and I may be wrong, but you may need a coupler and bulkhead that will fit in the coupler for the cargo bay.

Yeah, there's a couple of couplers and bulkheads in the mix.

Definitely concerned about losing the thing but I think the plan with this one would be to fly it at club launches in big fields only so, hopefully, that minimizes the chances of losing it. HAM license isn't a terrible idea but probably not on this build...maybe...