LOC Precision Bruiser EXP Build

kswing

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I'm starting to work on the largest rocket that I will have built to date. It is a LOC Precision Bruiser EXP with the addition of the LOC Removable Nose Weight System (RNWS). Once completed, it should be about 112" long ( 9' 4"), 7.6" in diameter and weigh about 22 pounds without a motor.

It has the LOC Modular Motor Adapter System (MMAS) with a 75mm motor mount. For motor retention I'm going to use a flanged AeroPack retainer. I'm also planning to add some extra reinforcement in a few places so that I can fly it on an M1350 for my L3 certification.

So far I've named it "Prometheus" who was the Titan (Ancient Greek) god who stole fire from the other gods and gave it to the humans. I've also considered a few other names for it such as "Ursa Major" (Big Bear) and "The Beast".

I placed the order last week and the folks at LOC Precision were very helpful in switching out the standard NC for the RNWS. I just received the kit today. I've done a preliminary inventory and I think everything is there except the main parachute which, according to the note in the box, will be shipped separately in the near future. My next step will be to weigh each of the pieces to see how they match up with my OpenRocket simulation. Here are some pictures:

IMG_20221013_171900569_HDR.jpg IMG_20221013_190215657.jpg
 

mtnmanak

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That's a nice looking rocket and I like your build thread on it. Did you use the stock centering rings or did you upgrade?

For that build thread, I used the stock CR's. In fact, for that build thread, I built the rocket as stock as I could to see how it all went together and to explore what mods I could do later. I used the knowledge from that build to design my own MMAS and RNWS for other builds and also built some later Bruisers with glassed tubes, different fins, etc. The Bruiser EXP is an excellent platform to play around with and experiment. Super fun rocket and a really great flyer - have fun!
 

Tractionengines

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I'm also planning to add some extra reinforcement in a few places so that I can fly it on an M1350 for my L3 certification.
Don't start building until get project approval from your TAP or L3CC for your L3. You can't build a rocket then decide to use it for L3. You need them involved BEFORE the rocket for L3 is built.

IT IS A COOL ROCKET, Looking forward to your build.
 

kswing

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Don't start building until get project approval from your TAP or L3CC for your L3. You can't build a rocket then decide to use it for L3. You need them involved BEFORE the rocket for L3 is built.

IT IS A COOL ROCKET, Looking forward to your build.
Thanks for the warning. I'd already run it by my TAPs and they gave approval for the build.

Now I just need to find some time to work on it.....
 

kswing

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Today I made a bit of progress on this. I removed the glassine from the 5.5" MMAS "host" tube by peeling it off and then used one of the notched centering rings (CRs) to transfer marks over to it where the fins will attach. I'm going to use the marks and an aluminum angle iron to draw lines on the host tube to ensure that the notches on my CRs line up. Here's a picture:IMG_20221107_192145323.jpg

I also used my belt sander to round off the leading and trailing edges of the fins. I'm not going for a super-aerodynamic shape on them, but, I also didn't want them to be simply square edges.
 

kswing

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I made a bit more progress today. The tee nuts that came with the kit were just a bit long, so, I ordered some that fit better and installed them in the lower CR using my bench vice. I also sanded the fin slots in the lower and middle CRs so that the fins would fit. They were just a tiny bit narrow, which, in my opinion is better than being too loose. Once I'd done that I did a dry fit of the fins and the CRs with the MMT. The upper CR with the U-Bolts is 3/8" and the lower two are 1/4". Here are some pictures:

IMG_20221109_192747147.jpg IMG_20221109_194303777.jpg
 

kswing

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Yesterday and today I worked on the Removable Nose Weight System (RNWS). I glued the forward bulkhead into the RNWS host tube and put a few holes in the host tube so that air could escape as weight cartridges are installed. Next I installed the tee nuts into the RNWS centering ring and then installed the CR into the nose cone with some T-88 epoxy. The ring braces against the NC shoulder, so, the epoxy is just there as a backup. Here are some pictures...

Host tube forward bulkhead:IMG_20221111_153820438.jpg


RNWS CR with tee nuts:
IMG_20221111_155149325.jpg

Dry-fit of RNWS CR into the nose cone:
IMG_20221112_131556467.jpg
 

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kswing

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I'm planning to have a loop of 3/8" Kevlar attached to the top CR of the fin can. I'll have a swivel between the Kevlar loop and the tubular nylon harness going to the electronics bay. Last night I sewed a loop in the Kevlar to connect it to one of the U-Bolts on the CR. I used 100 pound Kevlar thread in a sewing awl and followed the procedure I found on John Coker's web site. Here's a picture of the sewn loop and the awl.....I'll cover the end of the Kevlar with heat-shrink to keep the fraying under control:
IMG_20221112_203159433.jpg
 
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kswing

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Today I glued the RNWS 3" host tube into the nose cone. As per the instructions, I mixed up a batch of epoxy and drizzled it around the inside middle of the NC and then inserted the 3" host tube and put the NC upside down to let the epoxy run down to the top of the host tube. I also glued the host tube to the CR at the base of the NC. I've been using T-88 epoxy for this rocket, but, since I wanted the epoxy to run a bit this time, I used Zapp Z-Poxy, a thinner finishing epoxy, thickened a bit with silica. It doesn't show much, but, here's a picture:

IMG_20221113_105643717.jpg
 

kswing

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Yesterday I glued the forward CR to the MMAS host tube using some T-88 epoxy. It is on there pretty well, but, I'll probably still go back and add more of a fillet. I also put some epoxy on the nuts used to secure the U-Bolts so that they won't get loose over time. Here's a picture of the CR:
IMG_20221115_181210406_HDR.jpg


Also, I don't have a picture, but, a few days ago I used thin CA glue to reinforce the ends of the body tubes. It adds very little weight and and makes them much more resistant to minor bumps and bruises.
 

kswing

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Yesterday, I glued the thrust plate/bottom ring onto the 75mm motor adapter tube. I've replaced the ring that came with the kit, a 1/4" ply ring, with a 1/2" ply ring that I fabricated myself. I cut the outer circle of the ring with a jigsaw and the inner circle with my drill press and a hole cutter. I'm not that great at cutting circles with a jigsaw, so, I used my belt sander to even out the outer diameter. Using 1/2" ply might be a bit unnecessary here, but, I'll be using an AeroPack flanged retainer with this, so, this bottom ring will act somewhat as a thrust plate that transfers the force of the motor to the fins and the bottom ring of the MMAS. Here's a picture:

IMG_20221116_163259112.jpg


I'm not sure how much more I'm going to get done on it in the next few days since I'll be getting other rockets ready to launch at BattlePark this weekend.
 

kswing

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Last night I glued the two centering rings onto the 75MM motor adapter using a batch of T-88 epoxy. I used some extra from the batch to add more of a fillet between the top CR and the MMAS mother tube. Here's a picture of the motor adapter with all of the rings on it:
IMG_20221121_184354462.jpg

Tonight I started looking at where the fin meets the bottom CR of the LOC-N-Ring system. The bottom of the fin tab stick out just about 1/16" below the ring, so, I'm thinking I'll add some 1/16" ply to the bottom of the ring so that the adapter thrust plate contacts most of the ring and not just the bottom of the fins and the MMAS mother tube: Here's a picture of one of the fin tabs sticking out (it isn't glued yet):
IMG_20221121_193712712_HDR.jpg
 

kswing

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I had to look up T-88 epoxy as I'd never heard of it before.

I hadn't heard of it until last year, but, since then I've built a few things with it and so far I like it. It does take a long time to set and cure.

Before switching, I used Aeropoxy ES6209 which worked well, but, was very thick. T-88 is quite a bit thinner than the Aeropoxy, so, that makes it a bit easier to use. It is also a bit less expensive and easier to find than the Aeropoxy.
 

Handeman

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Tonight I started looking at where the fin meets the bottom CR of the LOC-N-Ring system. The bottom of the fin tab stick out just about 1/16" below the ring, so, I'm thinking I'll add some 1/16" ply to the bottom of the ring so that the adapter thrust plate contacts most of the ring and not just the bottom of the fins and the MMAS mother tube:
Why not just take 1/16" off the tab? Should be easier than doing a 1/16" thick CR.
 

kswing

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Why not just take 1/16" off the tab? Should be easier than doing a 1/16" thick CR.

Thank you for the suggestion. I will have to look at that again. I'd considered it, but, I was trying to leave the fins mostly as-is. It might be an easier adjustment.

If I leave them sticking out I wasn't going to do a full 1/16" CR. I was just going to put a few strips of 1/16" ply around the CR to spread out the load.
 

kswing

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Yesterday I made a bit more progress on this. I glued the middle CR to the MMAS mother tube. I put epoxy around the tube and then slid the ring up into it. I'll go back later and give it a good fillet. I put the fins in place without glue to ensure that it was lined up properly. Here's a picture:IMG_20221130_185023725.jpg

Since I had a bit of extra epoxy mixed, I also glued the all-thread mount pieces onto the electronics sled. Here's a picture of that: IMG_20221130_185043121.jpg
Also, (based on previous discussions here) I decided that the easiest way to handle the extra 1/16" (or maybe even 3/32") on the bottom of the fin tab was to remove it. So, I took a square file and adjusted them so they will be flush with the bottom CR. Tomorrow I'll probably start gluing the fins in place. Normally I'd use a template made from some foam board to keep the fins aligned, but, I think the notches in the CRs will take care of it. Also, before I glued the CRs I added lines on the mother tube for the fins, so, I'll be sure they line up there.
 

Handeman

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Since I had a bit of extra epoxy mixed, I also glued the all-thread mount pieces onto the electronics sled. Here's a picture of that: View attachment 548509
I was wondering, with the LOC kit, would it have been possible to put two of the guides on one side and two on the other?

I like doing mine that way, especially if I'm using dual altimeters and pull pin switches. With the threaded rods on opposite sides, each side of the sled is the same and there is room on both side edges for the pull pin switch while the holes are equidistance around the switch band. Just my OCD way of doing things.
Primary side.jpg
Secondary side.jpg
 

kswing

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I was wondering, with the LOC kit, would it have been possible to put two of the guides on one side and two on the other?

I like doing mine that way, especially if I'm using dual altimeters and pull pin switches. With the threaded rods on opposite sides, each side of the sled is the same and there is room on both side edges for the pull pin switch while the holes are equidistance around the switch band. Just my OCD way of doing things.
I looked at this tonight and I think you could do the guides on alternate sides of the sled. You might have to widen one set of the holes just a bit or adjust the guide placement slightly since the diagonal distance would be very slightly longer.

I like this idea, but, it's too late to easily adjust this sled as the guides are already glued in place. Also, with the new LOC 7.5" eBays, the eBay only takes up about 1/2 of the coupler, so, the switch band will be all the way at one end of the eBay. Because of this I'm planning to mount the screw switches to the bulkhead that lines up with the switch band and have the vent holes aligned so I can use them to reach the switches. I'm still planning it, but, I'll probably mount both altimeters on one side of the sled since there's plenty of room. Event though it probably won't matter for this, I might mount the batteries on the opposite side to keep the weight a bit more centered.

For those that aren't familiar, the new LOC 7.5" eBays consist of one 15" long normal tube coupler and 2 sections of "stiffy" coupler reinforcements that are each about 7 1/4" long. One of the eBay bulkheads is glued between the stiffy couplers and the stack is then glued into the normal tube coupler. You end up with an e-bay that is 7" long by 7.5" diameter and only occupies one end of the long tube coupler. The sled they provide is 6" by 7.5", so, it has plenty of room. They also provide a 1" switch band. According to their web site, they made this change so that you have more room either for motors or recovery gear.
 

kswing

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Last night I took the 75mm motor adapter and painted the bottom of the thrust plate with finishing epoxy so that it will be easier to clean. This morning I spray painted the thrust plate black so it looks better and then tonight I started mounting the Aero Pack flange retainer that will transfer the motor forces to the thrust plate and keep the motor from coming out when the apogee charges fire. I don't have the motor yet, so, I used a 3" tube coupler to ensure that it was all lined up properly. The Aero Pack came with threaded inserts, but, I've found it's easier to just use self-threading screws. I drill 1/16" tap holes for them so the wood doesn't split. So far I only have 6 out of the 12 screws installed. Here's a picture:

IMG_20221201_183415511.jpg
 

Handeman

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I looked at this tonight and I think you could do the guides on alternate sides of the sled. You might have to widen one set of the holes just a bit or adjust the guide placement slightly since the diagonal distance would be very slightly longer.

I like this idea, but, it's too late to easily adjust this sled as the guides are already glued in place. Also, with the new LOC 7.5" eBays, the eBay only takes up about 1/2 of the coupler, so, the switch band will be all the way at one end of the eBay. Because of this I'm planning to mount the screw switches to the bulkhead that lines up with the switch band and have the vent holes aligned so I can use them to reach the switches. I'm still planning it, but, I'll probably mount both altimeters on one side of the sled since there's plenty of room. Event though it probably won't matter for this, I might mount the batteries on the opposite side to keep the weight a bit more centered.

For those that aren't familiar, the new LOC 7.5" eBays consist of one 15" long normal tube coupler and 2 sections of "stiffy" coupler reinforcements that are each about 7 1/4" long. One of the eBay bulkheads is glued between the stiffy couplers and the stack is then glued into the normal tube coupler. You end up with an e-bay that is 7" long by 7.5" diameter and only occupies one end of the long tube coupler. The sled they provide is 6" by 7.5", so, it has plenty of room. They also provide a 1" switch band. According to their web site, they made this change so that you have more room either for motors or recovery gear.
Makes sense.
Kind of what I did with my Big Bird, but on that had a 14" long coupler for 6" tubes. No switch band. I adjusted the bay upward in the rocket so a CTI Pro98 6XL motor would fit with 6" in the booster and 8" in the payload. Maybe I should add a 2" switch band for the extra 2" I'll get for recovery in the payload.
 
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