QUESTIONS FROM FIRST TIME HPR BUILD

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BWP

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I'm building a LOC 4 for my high power cert and had a couple of questions.

I'm using titebond 2 for most of the build, epoxy for external fillets and JB Weld for the Aeropack retainer. After I was into the project I watched a build video where they sanded the glycine off the tubes where appropriate. I hadn't done that. Any concerns there?

I bought an Aeropack motor retainer for my 38mm motor tube. In the future I would possibly like to try t nuts. My research on this forum for motor retention mentioned this but I can't find much detail. Any guidance or threads to pass along?

Thanks.
 
You didn't sand any of the glue surfaces at all? Or just not peel the "shiny" layer? If you sanded/scuffed you should be fine.
 
BWP, on all laser cut parts I like to sand the charring off and remove dust with air. Anythjing that gets glued should be sanded as this will provide "tooth" for the glue to adhere to. All glass parts need to be degreased first, then sanded. Your glue choices should be fine. Are you wanting to use "T" nuts for motor retention? if so, LOC kits come with everything needed for that.
 
probably not

I'd stay with aeropack, as you go bigger the hardware is really expensive.
 
Aeropack retainers are good and wonderfully easy to use. Good choice.
 
I didn't sand the tube surfaces at all. I did lightly sand the root edge of the fin. And both the inside and outside of the centering rings. The pieces are tied in, meaning the aft centering ring butts up to the fin and the Aeropack retainer butts up to the centering ring.

I was wanting to use t nuts on a future build for motor retention and was looking for any details on that. The Aeropack is a well done piece, just expensive. Maybe that's something I'll have to get used to as I get more into high power.

My LOC kit didn't come with any motor retention hardware. No instructions either, which a build video had. It also had only 2 centering rings, I have 3.
 
I didn't sand the tube surfaces at all. I did lightly sand the root edge of the fin. And both the inside and outside of the centering rings. The pieces are tied in, meaning the aft centering ring butts up to the fin and the Aeropack retainer butts up to the centering ring.

I was wanting to use t nuts on a future build for motor retention and was looking for any details on that. The Aeropack is a well done piece, just expensive. Maybe that's something I'll have to get used to as I get more into high power.

My LOC kit didn't come with any motor retention hardware. No instructions either, which a build video had. It also had only 2 centering rings, I have 3.

Although many of us prefer Aeropack retainers for their ease and durability, tee nuts are a great way to go to save money. Two tee nuts in the lowermost centering ring, screws to fit, and mirror clips create a very functional retention system. Make sure the vertical part of the clip fits close to the thrust ring:
IMG_0768.jpg
 
Although many of us prefer Aeropack retainers for their ease and durability, tee nuts are a great way to go to save money. Two tee nuts in the lowermost centering ring, screws to fit, and mirror clips create a very functional retention system. Make sure the vertical part of the clip fits close to the thrust ring:
View attachment 376633

+1
Aeropack retainers look nice but are expensive and you can make motor retainers that work just as well using tee nuts or mirror clips for almost nothing.

The same goes for ejection canisters. You can spend a lot on machined aluminum ejection canisters, but I make my own from copper or aluminum tubing for a few cents.
 
I use 45-70 casings, knock out the primer and bolt them to the bulkhead.
all of my LOC kits came with those little clips and the hdw to use. They do work well, never lost a case with them.
 
With cardboard and plywood, sanding before bonding is less critical. Epoxy requires some roughness or porosity to lock into, but wood and cardboard have that already (other than when coated). The most critical joints are between the motor mount tube, fins and airframe, so it's recommended to sand the outside of the MMT where the centering rings bond to it.
 
JC it was your build video on YouTube that I learned about sanding the glycine off. I watched it too late though. Well done and informative video btw.
 
377FD9E7-7D96-452E-A79F-88EE8598756E.jpeg 14AC8FD7-B1B6-45E8-AC33-C60E58C19FCA.jpeg
After losing casings in half of my flights on friction fitting I went with a $11 madcow 38mm plate retainer.

For economy in 38mm I prefer the Aerotech RMS38/240 casing and H130W-14 USPS hazmat free load but you may want to sim your rocket first to see if that motor is okay. There’s also 38/360,
I180 hazmat free options. Loki has even more hazmat free choices.
 
After I was into the project I watched a build video where they sanded the glycine off the tubes where appropriate. I hadn't done that. Any concerns there?

I think you meant "glassine", Glycine is an amino acid - LOL !

Anyway, you should be fine, provided that your fillets are adequate. Did you do internal fillets on the fins ?

Dave F.
 
One way to save a few bucks on Aeropack retainers is to buy one "set" which includes the glue on base and screw on cap. Any other rockets you build with the same size motor mount you can buy just the glue on base and swap the cap as needed. Since I don't fly 'em at the same time, I have 4 rockets with 54mm mounts and only 1 cap.
 
One way to save a few bucks on Aeropack retainers is to buy one "set" which includes the glue on base and screw on cap. Any other rockets you build with the same size motor mount you can buy just the glue on base and swap the cap as needed. Since I don't fly 'em at the same time, I have 4 rockets with 54mm mounts and only 1 cap.

The only downside is, if you lose a rocket, you lose your only retainer . . .
 
I'm using titebond 2 for most of the build, epoxy for external fillets and JB Weld for the Aeropack retainer. After I was into the project I watched a build video where they sanded the glycine off the tubes where appropriate. I hadn't done that. Any concerns there?
.

if you have a concern about the joint strength on the fins, something you could do is drill some holes in the aft CR to pour some expanding foam into the fin can. ive used the adjustable density foam from PML
https://publicmissiles.com/product/adhesives

on a few builds and it seems to lock fins in pretty good. adds some weight but im personally ok with that.
 
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