LOC Terrier Booster: 2 Rings vs 3 Rings

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Funkworks

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Context:
I'm starting a Terrier Booster build. This would be my first 38mm build and first APCP staging kit. I'm also using Rocketpoxy for the first time. Whether necessary or not I don't know, but gaining experience with it seems like a good idea. So far, it looks like regular epoxy to me but I trust it has better properties than the JB Weld I've been using lately.

Where I'm at:
The first step was to glue the forward motor mount ring which I just did (after sanding).
The next step is apparently to glue the aft motor mount ring.

Problem:
The instructions mention only 2 motor mount rings, but the kit comes with 3 rings (as shown in photo).

Questions:
What would you do with the 3rd ring?
If you would choose to glue it somewhere between the 2 others, where exactly and why?

IMG_1242.JPG

(For some reason, the glued ring looks crooked in this photo but it's actually quite straight in real life, and I aligned it with a straight angle.)
 
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heada

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Ring with the hole goes at the forward end and hosts an eyebolt for recovery attachment point. Other 2 rings sandwich the fins but leave enough motor mount tube exposed so you can install whatever motor retention you want.

I normally leave extra room between the 2 lower rings for epoxy filets but you can also notch the fin tabs so that they don't interfere with the epoxy.
 

Cameron Anderson

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What he
Ring with the hole goes at the forward end and hosts an eyebolt for recovery attachment point. Other 2 rings sandwich the fins but leave enough motor mount tube exposed so you can install whatever motor retention you want.

I normally leave extra room between the 2 lower rings for epoxy filets but you can also notch the fin tabs so that they don't interfere with the epoxy.
What he said.

Make sure you rough up the outside of the airframe with some 80 grit before you do your external fillets.
 

Funkworks

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Currently looking into whether I should round out the fin edges. I'm guessing yes, but looking for confirmation. Scale info, prior builds, etc.
 

Cameron Anderson

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Currently looking into whether I should round out the fin edges. I'm guessing yes, but looking for confirmation. Scale info, prior builds, etc.
Built my Terrier booster over the last year and flew it the first time last month with my Sandhawk sustainer. Went great. I was trying to fly it this weekend but got pushed into August.
Just keep it stock - follow the instructions and you'll be fine. Definitely round the fins.
 

heada

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Currently looking into whether I should round out the fin edges. I'm guessing yes, but looking for confirmation. Scale info, prior builds, etc.
It's detailed in Rockets if the World if you have a copy. I believe that the fins are diamond foiled similar to a Nike booster.
 

kuririn

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If you want true scale accuracy then the fins should be diamond tapered.
Otherwise rounded is good enough.
 

Funkworks

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kuririn

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Ummm, diamond shaped.
ROTW:
0725201512[1].jpg

Estes Pro series Terrier Sandhawk:
0725201515[1].jpg
 

Funkworks

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Ohhhh ... that kind of diamond ... ♦♠♥♣ (said the crystal scientist who doesn’t play cards).

Well. Maybe I’ll make a jig and sand for a few hours. Or maybe I’ll just round the edges! (Because without power tools, I found out with my BB2 that it isn’t the easiest shape to sand!)
 
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kuririn

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Concur, plus if you taper it like that the edges are going to be really fragile.
 

heada

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With 60 grit on a good sanding block, it isn't that hard but it's not fun. Plus, the plys in the plywood help keep it even because they form lines as they're sanded down.

Unless you're going scale, in which case you'll have to built a custom interstate coupler, then just rounding or chamfering the edges is good enough.
 

Mike Haberer

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Context:
I'm starting a Terrier Booster build. This would be my first 38mm build and first APCP staging kit. I'm also using Rocketpoxy for the first time. Whether necessary or not I don't know, but gaining experience with it seems like a good idea. So far, it looks like regular epoxy to me but I trust it has better properties than the JB Weld I've been using lately.

Where I'm at:
The first step was to glue the forward motor mount ring which I just did (after sanding).
The next step is apparently to glue the aft motor mount ring.

Problem:
The instructions mention only 2 motor mount rings, but the kit comes with 3 rings (as shown in photo).

Questions:
What would you do with the 3rd ring?
If you would choose to glue it somewhere between the 2 others, where exactly and why?

View attachment 425881
(For some reason, the glued ring looks crooked in this photo but it's actually quite straight in real life, and I aligned it with a straight angle.)
Ideally, you should insert the MMT with the front ring in place and mark the location where the 2nd ring abuts the top of the fin slots. Dry fit the bottom CR and engine retainer at the same time to make sure you have the bottom MT positioned correctly for the engine retainer. Mark the location of the top CR in the airframe so you know where to apply epxoy for that rinig. Epoxy the 2nd ring at your marked location (only on the top edge for now). Next epoxy the MMT into position. Insert the MMT from the bottom of the airframe so the 2nd ring is just BELOW the top of the fin slots. Place epoxy above the top ring from the top of the airframe and through the slot onto the top of the 2nd ring. Turn the airframe to spread the epoxy on the top of the 2nd ring. Now slide into position and let it set. Now you can insert the fins through the fin slots and do internal fillets from the rear of the airframe. Do all of the joints (with the airframe and with the MMT). Do them in sets where the joints are at 45 degree angles so the epoxy doesn't run. When done stand upright and apply epoxy to the bottom of the second ring. Finally, you can now epoxy the bottom ring to the bottom of the fins and the airframe. Do the inside epoxy first and stand on end to set. Then flip over. Epoxy then epoxy the bottom of the 3rd ring to the airframe,, the engine retainer to the MMT first with JB Weld.
 

Funkworks

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With 60 grit on a good sanding block, it isn't that hard but it's not fun. Plus, the plys in the plywood help keep it even because they form lines as they're sanded down.

Unless you're going scale, in which case you'll have to built a custom interstate coupler, then just rounding or chamfering the edges is good enough.
I think I'm mostly afraid of cracking them as they thin. Definitely no custom coupler for this project. Air-starting APCP is the only goal.

Ideally, you should insert the MMT with the front ring in place and mark the location where the 2nd ring abuts the top of the fin slots....
Looks like great tips, I'll consider it all when I get back the work bench.
 

Funkworks

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Finally got back to this. Tentatively using Mike Haberer's post #13 as a checklist/instructions. Ordered an Aeropack retainer. Waiting for it.
IMG_2080.jpg

Don't mind the colorful "photo studio". Not to everyone's liking I suppose, but still better than the kitchen table or the mess in the actual office/workshop.
 

heada

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Aeropack on the booster is a no-brainer. Aeropack on a LOC 2.23" sustainer (Sandhawk, BBX, etc.) is more than a challenge. I went with Slimline for the sustainer.
 

Funkworks

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Ok, I'll see when I get there. Maybe the BBX instructions say something about this. I'll look up what Slimline refers to. At this point, I'm not sure if it's a company, brand, product, or a particular method lol.
 

heada

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Ok, I'll see when I get there. Maybe the BBX instructions say something about this. I'll look up what Slimline refers to. At this point, I'm not sure if it's a company, brand, product, or a particular method lol.
Aeropack retainers extend the width of the MMT by the width of the closure ring. Slimline retainers do the same but since there isn't an external closure ring, it is only the width of the retainer body. They're designed for small spaces where an Aeropack isn't an option. I think the instructions for the 38mm version of the 2.23 BBX recommend using friction-fit but you can opt for a slimline retainer instead. An Aeropack simply will not fit inside the inter-stage coupler.

 

Funkworks

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I think the instructions for the 38mm version of the 2.23 BBX recommend using friction-fit but you can opt for a slimline retainer instead.
Oh this is great! I had already settled for friction-fit but this sounds way better. Thanks!
 

Funkworks

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Both rings 1 and 2 are now in place and I just put on the 4th fin today. Next I'll be doing the fillets, 6 of them each day for 4 days.

IMG_2086.JPG

I found the head lamp (bottom left corner) to be very useful when applying epoxy deep inside the tube. I can't really seemy self do without it now. I purchased it in case of home power failure, but it's now part of of rocket building supplies.
 

Funkworks

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I finally finished this last night. I probably won't post anything else here. Next step will be the sustainer stage, which is still in the packaging. If I post build progress, I'll start another thread.

I used Rocketpoxy everywhere except for the metal Aeropack retainer (JB Weld). To apply all the fillets, I alternately used large popsicle-type sticks and my finger wearing a nitrile glove.
IMG_2124.JPG
 
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