BMS 3" 29mm

[TheBob]

My first MPR build. BMS 3" 29mm.. I got the 34in body tube and cut it down to 27" (original BT is 17") .
Since the fins with the kit were warped and I cannot get them straight I will be cutting new ones from 1/8 5ply. Since I am going to change the shape of the fins I attached the open rocket file. Any comments or opinions?
Robert.

 

[Back_at_it]

Looks good. Stability seems fine and I like that you added a stuffer with the longer body tube.

Should be a great flier. I have their 24mm and 29mm and they are both great rockets with tons of flights on them.

 

[emckee]

One caveat for this rocket, with the additional disclosure that I haven't looked at your sim file yet:

I've seen lots of people try and use this kit (or a similar version) when trying to do a L1 cert "on the cheap". When you put a larger/heavier motor in the standard kit (e.g. H195NT seems to be a common go-to motor for L1 certs), the flyer needs to add a not-insignificant amount of nose-weight. If you add nose weight, plan on making appropriate modifications to the length of the shock cord (longer) as well as the shock cord attachment to the nose cone (stronger, don't use the plastic loop).

You indicate you're already increasing the length of the rocket, so that's in your favor (increased stability, needs less nose weight), but I can't tell you how many certs have failed when the nose (with nose weight) comes to an abrupt halt at the end of the shock cord, snapping the plastic loop and dropping a weighted NC from altitude.

The kit is a great one and is very versatile (especially with the 29mm MMT), but when you're flying larger motors, make sure you engineer appropriately.

-Erik

 

[TheBob]

I don't plan to do L1 cert on this... but I did put in the H195 on the sim and it come in at 1.13 cal, A H268r is at 1.0 cal but 703 mph and 40+g of acceleration I know it will rip it apart.

 

[waltr]

I have the long one with payload bay and it flies very nice on F's (F42,52,67). Haven't even put a G in it yet. H may be too much for the thinish BT. I'd want LOC Precision heavy wall for H and up motors.

 

[TheBob]

 

[waltr]

Looking good so far.
I did not use a screw on retainer but used the clips that came with the kit. These clips work well and are simple and cheap.

 

[teepot]

I have built several of those kits. If you contact Bill at BMS I'm sure he will send you new fins. I first saw those clips on that rocket. Now that's my go to retention method. Much less money than the other retainers I was using. BMS also so heavy weight BT's. Not quite as heavy as LOC, but thicker than Estes. In the spirit of full disclosure I live 5 minutes from BMS.

 

[dhbarr]

An h97j should do just fine, nice and gentle. An i600r is probably less of a good idea.

 

[Back_at_it]

Can't speak to flying on H motors but I have flown my stock length version on the G72 once and got it back after a rather long drive in the desert No damage done.

 

[jmasterj]

BMS also so heavy weight BT's. Not quite as heavy as LOC, but thicker than Estes.

It's interesting that BMS's T80H is thicker wall (.041") than LOC's 2.63" tube (.035"), but the former's T300 is thinner (.035") than LOCs 3" (.05"). The 3in tubes are not compatible with each other; LOC uses the standard 3" ID that almost every kit maker users while BMS has a smaller ID that I believe matches the Estes 3" tubing.

An h97j should do just fine, nice and gentle. An i600r is probably less of a good idea.

An I600R also won't fit in the motor mount

 

[teepot]

It's interesting that BMS's T80H is thicker wall (.041") than LOC's 2.63" tube (.035"), but the former's T300 is thinner (.035") than LOCs 3" (.05"). The 3in tubes are not compatible with each other; LOC uses the standard 3" ID that almost every kit maker users while BMS has a smaller ID that I believe matches the Estes 3" tubing.

An I600R also won't fit in the motor mount

I mostly use the BMS 3" because it's lighter than LOC. All the smaller sizes I get the heavy ones. The Rocket Gods sure smiled down at me when BMS moved to the neighborhood. He was here for a couple of years before I saw an ad in Sport Rocketry with an address. That was a shock.

 

[waltr]

The light (thinner) BT from BMS over LOC is why I built this rocket. I have the extended with payload bay and its about 5 feet tall but flies well on F motors.
For higher power motors and full DD I like the heaver LOC tubes.

 

[dhbarr]

It's interesting that BMS's T80H is thicker wall (.041") than LOC's 2.63" tube (.035"), but the former's T300 is thinner (.035") than LOCs 3" (.05"). The 3in tubes are not compatible with each other; LOC uses the standard 3" ID that almost every kit maker users while BMS has a smaller ID that I believe matches the Estes 3" tubing.

An I600R also won't fit in the motor mount

Not with that kind of an attitude!

 

[TheBob]

I had a few hours this morning, fixed the band saw with new tires, and a 3/8" wide 24tpi blade.
Then I cut, filed and sanded to shape a new set if fins from 1/8" 5ply. I feel they turned out well and are nice and straight.

 

[TheBob]

 

[TheBob]

Next up is using the router table. I will make a fence for it so that the lower edge of 3/4" radius can cut the trailing edge, then a 1/4" for the leading edge..

 

[TheBob]

Baffle


I glued a 1/8 spacer (two drops of ca) on the fins set back 1.1" from the trailing edge to sand a bevel

 

[TheBob]

Updated the .ork file.

 

[David_Stack]

Nice work on the fin beveling!

That aircraft ply looks really nice, care to name your supplier?

 

[TheBob]

Balsa USA https://shop.balsausa.com/category_s/1668.htm

 

[TheBob]

Fins are on

 

[TheBob]

I used a syringe to place glue then used a 1/4 dowel to smooth the internal fillets

 

[TheBob]

BSI 15 min epoxy mixed with some phenolic micro for the fillets.

 

[Back_at_it]

I used a syringe to place glue then used a 1/4 dowel to smooth the internal fillets
View attachment 540996View attachment 540997

You win the award for the cleanest and nicest internal fillets I have ever seen. Nice job!

 

[Hobie1dog]

excellent, keep the pictures coming

 

[TheBob]

Well after searching TRF. I discovered the fillet radius should be 4-7% of the fin root cord. So 5.125” fin root .25 radius. 1/2 ball bearing. After etching a spot with ospho I used thick CA to glue on a 5/16 dowel followed with some micro when the ca was still wet (that will set the ca)

 

[Neutronium95]

I don't plan to do L1 cert on this... but I did put in the H195 on the sim and it come in at 1.13 cal, A H268r is at 1.0 cal but 703 mph and 40+g of acceleration I know it will rip it apart.

I built one with all of the extras a few months ago just to have a simple rocket to fly at launches. I fly it all the time on 6XL and 6 grain 29mm motors. It goes to about 3000 feet on a H399. I also use a Stratologger CF in the payload bay along with a cable cutter to do dual deploy on mine to cut down on walking.

The only structural change that I made to the kit was to replace the provided shock cord with about 15 feet of 1/4" kevlar.

Video of a flight on a H399:

 

[TheBob]

I have been contemplating using it for a l1 cert. AeroTech DMS H115DM with OR sims to 2700ft, My projected total weight (including paint) will be between 500-515 grams with a JL chute release.

 

[TheBob]

Now the finish work will start. First to do is cleaning up the fillets with 180, then a once over with 320. This will be followed up with 2k urethane hi build primer. Then more sanding with 400. Final paint will be base/clear coat.