Help with LOC BRUISER-EXP

[jimzcatz]

The LOC Bruiser EXP already comes with an av-bay kit so no need to make a hatch bay. The two 7.25" couplers are for the av-bay.


Attached is a rocksim file of how I would build this kit.

Also the only K motors I would feel safe flying in this rocket are the K1050W or K1999N

K1275. IMHO, there's no need to glass this. I never glass paper parts. The most I would do is paint the entire rocket with finishing epoxy and that's just to seal it for painting and regarding Glassine, I have said this ad nauseum. Glassine does not have to be sanded, peeled or otherwise torn off. A simple damp sponge will remove it.

 

[jrains]

Did you build the rocket and did you fiberglass the tubes or fins?

It is a work in progress. All the tubes have been glassed (see attached vid) using LOC’s glass packs. The MMAS and fins are installed in the fin slots and the external fillets are almost done (one left). Next up is tip to tip.

 

[mtnmanak]

I didn't glass the tubes or fins. I have flown it on a K1499 (shakeout), a K1000, a 3 x J450 cluster and 5 x I280 cluster. All flights were nominal. May try to push it harder if I head to URRG in a couple weeks.

 

[jrains]

Looks mighty pretty indeed. Great paint job. Goal here is to achieve L3, and the waiver is only so high. Plus for L3, you are not supposed to go over 90% the waiver. Cardboard does fly higher than bricks.

 

[mtnmanak]

I missed that you were planning on using this rocket for an L3 attempt. It should work out well. That 3 x J450 flight was the equivalent of a 61% L motor. I have a bunch of small M motors laying around looking for a rocket to fly in. If the weather is good at a launch in May or June, I will throw one into this bird and let you know how it goes without any glassing.

 

[cwbullet]

Looks mighty pretty indeed. Great paint job. Goal here is to achieve L3, and the waiver is only so high. Plus for L3, you are not supposed to go over 90% the waiver. Cardboard does fly higher than bricks.

That is a standard waiver practice for Research motors. I am not sure of the source for the 90% requirement. We use it for all flights as a measure of making sure we do not break the waiver, but I do not see 90% in the Unified Safety Code.

 

[jrains]

That is a standard waiver practice for Research motors. I am not sure of the source for the 90% requirement. We use it for all flights as a measure of making sure we do not break the waiver, but I do not see 90% in the Unified Safety Code.

From the NAR L3 form…

LEVEL 3 PRE-FLIGHT INSPECTION CHECKLIST (completed by certification team)
Is the rocket’s predicted altitude no greater than 90% of the FAA waiver restriction?

Note that it says predicted altitude.

If you bust the waiver, no joy.

 

[jrains]

I missed that you were planning on using this rocket for an L3 attempt. It should work out well. That 3 x J450 flight was the equivalent of a 61% L motor. I have a bunch of small M motors laying around looking for a rocket to fly in. If the weather is good at a launch in May or June, I will throw one into this bird and let you know how it goes without any glassing.

I have corresponded with another rocketeer who flies the rocket stock with no issues. Getting together the wherewithal to glass the tubes has stretched this project out.

 

[cwbullet]

From the NAR L3 form…

LEVEL 3 PRE-FLIGHT INSPECTION CHECKLIST (completed by certification team)
Is the rocket’s predicted altitude no greater than 90% of the FAA waiver restriction?

Note that it says predicted altitude.

If you bust the waiver, no joy.

That is good info. It used to say on the TRA rules 90% for EX. It is not there anymore. I did TRA cert 3 so I wonder what the source is for the requirement of 90%?

 

[jrains]

I didn't glass the tubes or fins. I have flown it on a K1499 (shakeout), a K1000, a 3 x J450 cluster and 5 x I280 cluster. All flights were nominal. May try to push it harder if I head to U

I didn't glass the tubes or fins. I have flown it on a K1499 (shakeout), a K1000, a 3 x J450 cluster and 5 x I280 cluster. All flights were nominal. May try to push it harder if I head to URRG in a couple weeks

Lots of questions if you don’t mind…

- Did you use the supplied recovery harnesses and parachutes?
- Did you add weight in the nose?
- What was the weight without motor?
- How much BP for drogue and main deploy?
- What number and type of shear pins did you use?
- And advice?

thanks!

 

[mtnmanak]

Lots of questions if you don’t mind…

- Did you use the supplied recovery harnesses and parachutes?
- Did you add weight in the nose?
- What was the weight without motor?
- How much BP for drogue and main deploy?
- What number and type of shear pins did you use?
- And advice?

thanks!

Here is the original build thread I did on this rocket, although I admit it is a bit anemic. I got busy doing other things and never updated it after I finished the ebay and flew it. I need to go back and finish out that thread, at some point.

https://www.rocketryforum.com/threads/loc-bruiser-exp-with-mmas-and-rnws.169277/
Here is the MMAS thread:
https://www.mountainmanrockets.com/index.php/tools_tech/loc-mmas/
And the RNWS thread:
https://www.mountainmanrockets.com/index.php/tools_tech/loc-rnws/
- Did you use the supplied recovery harnesses and parachutes?

I did not. I looped a length of 1500 pound Kevlar through the U-Bolts on the foreword MMAS ring and tied a 1500 pound swivel at the top of the loop. I sized the Kevlar to ensure the swivel came just up to the edge of booster tube. Should work to prevent zippers.





- Did you add weight in the nose?

I am using the LOC Removable NoseWeight System, so I can add weight when necessary. Having said that, I have not encountered a situation where noseweight was required. I posted my Rocksim files below, so you can see all the simulations I ran for each motor conifg. The lowest margin between the CP and CG I saw in all those sims was 1.3.

- What was the weight without motor?

75mm MMT: 9700g (21.3 lbs)
3 x 54mm MMT: 9723g (21.4 lbs)
5 x 38mm MMT: 9820g (21.7 lbs)

- How much BP for drogue and main deploy?

These are big, mostly empty tubes, so I am sure if you looked at the online black powder calculators, they are showing some very large amount of BP. I started ground testing relatively low (with about 4g) and worked my way up. I found that 6g of FFFFg for the drogue and 5g of FFFFg for the main reliably ejected the laundry.

- What number and type of shear pins did you use?

I am using 3 x 2-56 shear pins. This is a pretty lightweight rocket (compared to a fiberglass rocket of similar size) and the nosecone is very light. 3 x 2-56 pins easily holds the nosecone on during the drogue event. I did use brass plates in the wall of the payload bay, but that should be pretty standard practice with carboard rockets and shear pins:



- And advice?

I built this rocket as close to stock as possible, which is why I didn't glass anything. I was using this rocket as a test bed to learn how these large LOC rockets build out. I have a LOC Saturn V that has been sitting on the build pile since 2019 and I wanted to build out one of these 7.6" birds before I started that build.

Having said that, there are a few lessons I learned. I think glassing the tubes and fins is a good idea. I don't think this rocket needs it, but I think the added weight and rigidity will be a bonus. I do plan to glass the tubes on my Saturn V.

6g of FFFFg really eats up the cardboard and threatens to destroy the tube edges every time I fly this thing. At first, I coated the edges with CA, but later I went back and coated all edges and all the surfaces of the Ebay that are exposed to the BP with a solid coat of epoxy. I wish I had done that before I ground tested/flew the bird.



Another note for the ebay, as you can see from the picture above, I built out the ebay as per the instructions, with one end of the ebay "open". This design is to allow for longer motors and more room for recovery items in short, fat birds. There is no need to build the ebay like that for this rocket. The tubes are super long, so there is no need to build the ebay "short". I think it is worse, because that is just more volume you have to account for with the BP charge. I built the ebay super simple, but I am going to build an MMAS mount with 1x54mm center motor and 6x 29mm outboards and I will want that to be capable of airstarts, so I had planned to rebuild the ebay anyway. When I build the new one, it will have both stiffy couplers in the middle and the bulkheads on the outside.

As noted in the build thread, the z-clips that come with the kit work fine, but they are not easy to use if you want to fly smaller diameter motors with adaptors. I ended up rebuilding the 75mm MMT with an Aeropack retainer so I could also fly single 54mm motors in that config.

This issue may not be an issue for many people, but, as I noted in the build thread, the LOC 75mm motor tubes are just a hair too small to fit the Loki 76mm cases. I do have Loki hardware, so this is an issue for me. If I ever get around to building yet another 75mm MMT for the MMAS, I would probably use a fiberglass motor tube that I know accommodates Loki hardware.

Other than that, this is a pretty straight forward rocket build and it is a great flier - it should serve you well on that L3 attempt!

 

[jrains]

Your post was super helpful. I tried to reply thru the TRF mail fiction, but it would not work for some reason. I sent you an email using the address on your website: [email protected]

 

[jrains]

Here are pixs of Jester's ejection charge canisters installed at the end of LOC's short Ebay. Using a drill press set at low RPM and 1" Forstner bit, drilled really clean holes to recess the canisters in the top Ebay bulkhead. Looks sweet!

 

[mtnmanak]

Here are pixs of Jester's ejection charge canisters installed at the end of LOC's short Ebay. Using a drill press set at low RPM and 1" Forstner bit, drilled really clean holes to recess the canisters in the top Ebay bulkhead. Looks sweet!View attachment 519307View attachment 519308View attachment 519309

Very clean, nice!

 

[Theory]

I like the recessed charge wells