LOC Precision Bruiser EXP Build

Onebadhawk
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This afternoon I started testing the main charges. I started with 3 grams and it got the nose off and the deployment bag out, but, not very far. Next I tried 3.5 grams and it got the entire main shock cord out, but, not stretched very far. Either of these would probably work as they both got the pilot chute and the deployment bag out. That being said, I think I'd like a bit more separation, so, I'll probably try again later with 4 grams.

The main side makes much less noise that the drogue did. I think it's partially because I'm using less powder and partially that the tube is not as empty.

Below is a video of 3.5 grams. Note that the brighter yellow chute is the pilot and the neon pink harness is just there temporarily to prevent the nose from flying too far during testing.

View attachment VID_20230220_140803998.mp4
 
I ran another test of the main with 4 grams and I think it will work. The nose covered a good distance and pulled the deployment bag off of the main chute. This time I skipped the neon pink test harness. The narrow yellow line between the deployment bag and the main is the 100 feet (Z-folded and taped) of 250lb Kevlar I'm using to keep it all together during descent.

I messed up and didn't get video this time, but, I took the still picture below of the end result.IMG_20230220_160123969.jpg
 
sounds like 4 grams it is. or 4.25...

I always add a bit to my actual flight charges. Things changes during flight. Not as "nice" as a fully controlled ground test where everything is "just so."
 
cwbullet said:
How many bulkheads did you have for your AV bay?
Click to expand...
Just two.

The plan they provided for it had you put one bulkhead in the middle of the av-bay, between the two stiffy couplers, and the other on one end. I modified it to be more traditional and pushed the stiffy couplers together and put the bulkheads on the ends.
 
cwbullet said:
I did not receive a plan.
Click to expand...
I think mine came with a short set of instructions. Tonight I'll see if I can find them and post them. Here's another thread that may be helpful:
https://www.rocketryforum.com/threads/questions-on-the-new-loc-7-5-av-bay.176485/
For my rocket, I didn't need the extra space so I got some longer all-thread and just built it as a traditional electronics bay. The stiffy couplers' combined length is about 1/2" shorter than the outer coupler so the bulkheads rest against the ends of the stiffy couplers.
 
kswing said:
I think mine came with a short set of instructions. Tonight I'll see if I can find them and post them. Here's another thread that may be helpful:
https://www.rocketryforum.com/threads/questions-on-the-new-loc-7-5-av-bay.176485/
For my rocket, I didn't need the extra space so I got some longer all-thread and just built it as a traditional electronics bay. The stiffy couplers' combined length is about 1/2" shorter than the outer coupler so the bulkheads rest against the ends of the stiffy couplers.
Click to expand...
How thick were the bulkheads? I have two 1/4 inch.
 
I would consider Kevlar with a greater break strength. Design your recovery system to handle 50X the total rocket weight at a minimum. You can generate that many Gs if you have a late deployment.
 
ep29030 said:
I would consider Kevlar with a greater break strength. Design your recovery system to handle 50X the total rocket weight at a minimum. You can generate that many Gs if you have a late deployment.
Click to expand...
He is using the heavy Kevlar (don't remember the rating), and 2200lb Nylon for the actual harnesses. I think what you saw above is he is using 250lb Kevlar to "tether" the Pilot Chute Deployment Bag and Nosecone to the main harness. If the tether breaks the parts just come down a ways apart from each other safely under their own chutes.

[ Edit: Rmoved comment about the tether maybe being too long. I looked again, and the Pilot chute is staing with the nosecone so the 100ft length makes sense. ]
 
Last edited:
Tractionengines said:
He is using the heavy Kevlar (don't remember the rating), and 2200lb Nylon for the actual harnesses. I think what you saw above is he is using 250lb Kevlar to "tether" the Pilot Chute Deployment Bag and Nosecone to the main harness. If the tether breaks the parts just come down a ways apart from each other safely under their own chutes.

[ Edit: Rmoved comment about the tether maybe being too long. I looked again, and the Pilot chute is staing with the nosecone so the 100ft length makes sense. ]
Click to expand...
Yes, that is where you want to be for a big kit.
 
Ken, Any idea when you are going to fly it?

I think Bob wants to fly his L3 cert this coming launch, but I think Saturday is going to be rained out. Of course that will make the field pretty sloppy on Sunday too.
25 & 26 might turn out to be better.
 
Handeman said:
Ken, Any idea when you are going to fly it?

I think Bob wants to fly his L3 cert this coming launch, but I think Saturday is going to be rained out. Of course that will make the field pretty sloppy on Sunday too.
25 & 26 might turn out to be better.
Click to expand...

I was hoping to do a test flight on a K1103X this weekend, but, as you said it looks like lots of rain Friday and Saturday, so, Sunday might be a muddy mess. If this weekend doesn't work then I'll try the test on the 25th or 26th and then hopefully the cert flight in April.

I'd like to get this done, but, I'm also not in a rush. If needed I can wait until the fall or possibly look at doing it at MDRA.
 
Today at Battlepark I finally got to test this on a K1103X and everything went pretty well. Apogee was at about 2100' which was within 100' of the simulation. All of the charges fired and recovery went mostly as planned.

The NC fell just a little bit faster than the fin can, but, not enough to cause a major issue. If it had been much too quick I'd be concerned that it might cause a partial collapse of the main. I've looked at the telemetry and the simulation and I think with the extra weight of the M motor (both the empty case and the heavier MMAS adapter) the fin can should fall faster for the cert flight so hopefully it won't be an issue. If the weather cooperates I'm hoping to do a certification flight in a few weeks.

Also, thanks to all of the folks who helped out with it today at Battlepark. It isn't so heavy that I can't move it around alone, but, it is much easier with assistance.
 
On Friday at Battlepark I successfully launched (and recovered) this on an AT M1350W (SU/DMS). Apogee was about 6665' and it drifted about 1/2 mile into an open field. The tracker worked, but, I didn't really need it as it was visible from launch.

I'd like to say thanks to Ben and Elaine who acted as my TAPs and thanks to all of the other folks at Battlepark who provided support and assistance. Also, thanks to those on this forum who provided advice and encouragement.

For those interested, I've attached the OpenRocket file with adjustments to match the rocket as-built.

Here are some pictures (thanks Mitch):

DSC_9339.JPGIMG_20230414_105308511_HDR.jpg
 

Attachments

  • bruiser_exp_75mm.ork
    4.1 KB · Views: 0
Congratulations and thanks for posting the adjusted .ork file, which I'll study later. Looks like it was a great flight. IMHO that low key paint job has just the right kind of 'missile' feel for a Bruiser.
 

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