BMS 29mm School Rocket Build Thread

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Alan R

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I've seen a lot of love here for the Balsa Machining School Rocket, but nary a build thread. (https://www.balsamachining.com) Thought I'd post this for posterity.
This has been sitting at the bottom of the build pile for almost a year now. My invoice reads 10/22/2020.
I bought the optional 34" BT for an extra $5. Total with shipping is under $50. Base price for the standard kit comes out to $41.95. Quite a bargain for a nice big rocket.

Kit contains everything needed: heavy pre-slotted 3" body tube, plywood CR's and fins, kevlar cord, elastic shock cord, 1/4" launch lug, 3-point engine retainer, 12" plastic nose cone. Instructions say a parachute also, but I don't remember one being in the box. Or maybe I pulled it out a long time ago. I have lots so I'm not worried about it.
I already had the rail buttons, so I'll build it with lugs on one side, buttons on the other.

Very nice clear instructions.

I ordered the extra-long BT because I thought the stock rocket looked a little stubby. I already have a stubby, I wanted something just a bit longer. I will cut the BT down by a foot or so. The stock BT is 17" and finished rocket is 28" with the long nose. Mine will end up around 34"

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Alan R

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The parts. Hardware bag even included a nice swivel. First time I've seen that. Loooooong tube...
I built the motor mount last night before thinking I'd do a thread on this. Details on that next.

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Alan R

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There are 2 different centering rings for the motor mount. The forward ring has 2 holes and instructions say to tie the shock cord on it with a bowline knot. I like how they even have a nice illustration in the instructions for that knot. It's easy to tie, but also easy to forget exactly how to get it right.

The aft ring comes installed with 3 t-nuts for holding the retainer clips.

I changed this all up. I 3D printed a screw-on retainer set. Then I pulled out the t-nuts so I could use the holes to tie the schock cord to the aft ring.
If I ever need to replace the kevlar cord, this makes it easy. After a couple of years of launching rockets I realize I will probably never need to do that, even with slim 100# cord. but hey, I guess I just like the idea of it. Made sure to line up the fore and aft holes, and just ran the cord through the forward CR.

Instruction say all you need for this kit is white or yellow glue. Forward ring installed with Titebond.
Yellow glue won't stick to printed plastic though. Since I had to epoxy the screw thread, might as well just use it on the aft ring as well. Remember to rough up those surfaces kids.

I did make the mistake of gluing the rear CR... that should have waited until after I mounted the fins. Ah well, nothing some qtips wont fix.

Instructions also say to set the aft ring in 1/4", thats to accommodate the screw clips. The screw threads require 5/8", so the motor is going to stick out a bit farther than the original plans.

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Alan R

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I have to fess up here, it really bugs me that I glued that aft ring in place.

Why? maybe impatience. Wanted that epoxy to get an overnight dry before continuing. dunno.

Or maybe because i've spent too much time on little Estes surface mounted fins where it's always glue the whole mount in first that I didn't even think about it.

Now I'm considering how much trouble it is to cut the mmt down by 3/4" and redo it vs the trouble of laying in fillets with a swab.
 

Scott_650

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I have to fess up here, it really bugs me that I glued that aft ring in place.

Why? maybe impatience. Wanted that epoxy to get an overnight dry before continuing. dunno.

Or maybe because i've spent too much time on little Estes surface mounted fins where it's always glue the whole mount in first that I didn't even think about it.

Now I'm considering how much trouble it is to cut the mmt down by 3/4" and redo it vs the trouble of laying in fillets with a swab.
Maybe do an insertable fin/motor mount assembly instead? Just open up the fin slots all the way aft, attach your fins to the motor mount assembly the slide the whole thing into the tube. I prefer leaving the aft centering ring free of glue until everything is glued and the interior fillets are done but IMO doing the fin can assembly separately is preferred to cutting down the motor tube. Just a suggestion - either way the 3” SR is a great kit and I doubt any slight modifications will affect how it flies.
 

Alan R

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Maybe do an insertable fin/motor mount assembly instead? Just open up the fin slots all the way aft, attach your fins to the motor mount assembly the slide the whole thing into the tube.
Oh I like that idea. Much much easier and better than what I was thinking. Thanks!
Need to make a really good alignment jig for that.
 

Alan R

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Next up cutting down the BT. Decided to whack 13" off of it. Still looks like the "school rocket" but not quite so stubby.
Measure, wrap and cut:
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teepot

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I've built a couple of those for Bill at BMS. Good kit and good directions. I'll be buying one to donate for our OctoberFest launch next month.
 

Alan R

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Today.. launch lug and fillets.
Also had this crazy idea last night... I could paint before assembly!! None of that silly masking stuff required.

Fin can fits into the slots just like it should. One fin seems to be just slightly twisted but nothing serious, the 90 degree angles are very good according to my eyeballs and the pre-cut slots.
 

Alan R

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I sliced into that not-quite-straight fin, twisted it a little and gave it a heavy fillet. It was only a couple degrees off but it bugged me. Much better now.

I pre-painted the components and it's ready for final assembly today. Yup, that's the standard school rocket color scheme. Taped out a 2" strip on the BT for fin gluing.

Ready for assembly. I just left the blue tape on the nose because it was too loose without it.

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Alan R

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Did a little read-ahead on the instruction sheet. This part was different than I expected. The kevlar goes from mmt direct to nosecone, and the chute is attached via elastic to nosecone per instructions.
Not how I've ever done it before. If I hadn't read the instructions I would have just tied the elastic at the end of the kevlar. Kevlar is twice the length of my slightly longer BT.

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waltr

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Nice build thread. I have looked at that kit for a while.
Was putting in a motor order to BMS and decided to buy this kit. Getting the extended body and the payload section.

I will be building an ebay for dual deploy.

Once I get the kit I'll do an open rocket model for simulations.
Do you have an OR file for this? If not I can post one here in a couple of weeks.
 

Alan R

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I do have an ork file on this. It's for the standard 17" body tube. Just extend that for your needs. I modified a copy to 22" to do sims on my version. No idea where I got this originally.
 

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waltr

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Looks great with those decals.

Thanks for the ORK file.
 

Sandy H.

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Thanks for the post. I never looked at the kit, assuming it was some bulk-pack thing for a quick one day build and fly due to the name. Wow, was I wrong! Looks like a super solid rocket that would fly on lots of good motors.

Also, your decals are really cool. Not sure if that was all your idea or if the kit mentions it, but you nailed it either way. I think the packing tape idea is smart for a rocket that can be used and abused. I almost wonder if adding a little packing tape over the top so it tapes to the rocket instead of just relying on the glue would be worth it, but maybe there is no need. I hope to see flight pics and to see it getting a lot of 'road rash' because you like flying it so much.

Sandy.
 

Alan R

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Thanks for the post. I never looked at the kit, assuming it was some bulk-pack thing for a quick one day build and fly due to the name. Wow, was I wrong! Looks like a super solid rocket that would fly on lots of good motors.

Also, your decals are really cool. Not sure if that was all your idea or if the kit mentions it, but you nailed it either way. I think the packing tape idea is smart for a rocket that can be used and abused. I almost wonder if adding a little packing tape over the top so it tapes to the rocket instead of just relying on the glue would be worth it, but maybe there is no need. I hope to see flight pics and to see it getting a lot of 'road rash' because you like flying it so much.

Sandy.
Thanks for the kind words. I think it's called a School Rocket because they actually do sell an 18mm version in bulk for $6 ea. Can't beat that price anywhere. You can also get this big one in a 24mm version. It's like I said up front, compare the price to anything else out there and it's a great bargain.

As for the decals, that was all just my idea when I woke up yesterday morning. I thought it would be fun. School Rocket = rocket school. Taping them on would not look good, and regular paper needs some protection. I did something similar with my Tiki rocket where I laminated the whole page as a graphic wrap.
Putting the tape down on these first, then cutting to size afterwards gives them a nice clean look and they should last quite a while.
 

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Great build. I saw the School Rocket when ordering some materials and had to have one. I picked up the small rocket along with the 3" version in 24mm and it was a fun quick build. The quality was perfect as it everything that comes from BMS.

Flew the 24mm on and E30-4 first flight and decided that I really liked it on that motor and the F44. When I placed another order for materials with them I picked up the 29mm version. Such a great rocket at a really good price. Some other manufactures could learn a few things from them.
 

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Back_at_it

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Your bench is so clean and organized. I like that blue.
Don't be fooled. I have to stop about once a week and put everything away. Monday it was so covered in stuff from my last launch that I couldn't sit anything more on it. I had to put up shelves to put all the extra junk on.
 

Alan R

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Don't be fooled. I have to stop about once a week and put everything away. Monday it was so covered in stuff from my last launch that I couldn't sit anything more on it. I had to put up shelves to put all the extra junk on.
Ah... so that was just for the photoshoot ;)
 
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