First HPR Build

[Jeff Curtis]

I've built a few mid-power rockets with no issues, but have a couple of questions concerning high power.

1. Epoxy - I've ready 5-minute epoxy is not the strongest. I bought some T88. Is that the way to go, or should I get some 30-minute epoxy?
2. I bought some PC-7 epoxy putty to try on the fillets for my Loc Onyx. Should I avoid this for HPR?
3. Is it a good idea to mix microballons with epoxy for fillets?
4. This will be my first go with rail buttons. I've read some threads on the forum and one person mentioned using Well nuts with no issues. I like the idea of being able to place the nut any where you want. I bought som rail buttons from Apogee and they have flange nuts which have to be placed internally to the tube. Or is screwing into the motor mount rings the way to go?

I'm planning to build the North Coast Laser Lance to try internal fin fillets and rail buttons for the first time. Then I will start my LOC Semper Fi.

 

[mhanna]

I've used 5 min. epoxy on Level 1 & 2 rockets. No issues.

 

[bjphoenix]

Epoxy putty should be OK for your fin fillets. If you are using normal epoxy for fin fillets you have to mix something in there to make the epoxy thicker or you have to take steps to keep the epoxy from running everywhere.

 

[KenECoyote]

I've used 5 min. epoxy on Level 1 & 2 rockets. No issues.

Same. However, I have a variety of epoxies... 5, 15, 30, West Systems, etc.

5 min is good for smaller quick jobs, but not for anything you want time to put in proper position and want to have time to spread because it'll likely start to harden and set before you're ready, which can be disastrous.

Edit Add: I only use quality hobby 5/6 minute epoxy (ex. BSI, tower Hobbies) and for less critical build areas YMMV.

 

[JackC]

5 minute epoxy will become brittle in a few years. 30 minute will hold up longer. Epoxy putty should be fine for fillets. Save the more expensive epoxy for high speed L2 or L3 builds.

 

[Jeff Curtis]

Epoxy putty should be OK for your fin fillets. If you are using normal epoxy for fin fillets you have to mix something in there to make the epoxy thicker or you have to take steps to keep the epoxy from running everywhere.

I went with System 3 15 minute epoxy, and mixed in micro balloons for fillets. Seemed to work pretty well.

 

[mtnmanak]

https://www.mountainmanrockets.com/index.php/hpr-primer/

 

[KenECoyote]

I went with System 3 15 minute epoxy, and mixed in micro balloons for fillets. Seemed to work pretty well.

I've been using it and I like it!

 

[boatgeek]

T88 is great, though it will take a while to set. In the meantime, it will want to dribble. You’ll want some micro balloons or wood flour to thicken the epoxy for fillets, or just do 2 at a time with gravity as your friend. I’d use 5-minute to tack stuff in place and then follow up with the T88.

I’ve never used epoxy putty so I can’t say one way or the other.

I really like the flanged rail buttons. If you want flexibility in where to place them, you can glue some plywood in behind where the button goes and then screw it into that.

 

[bad_idea]

4. This will be my first go with rail buttons. I've read some threads on the forum and one person mentioned using Well nuts with no issues. I like the idea of being able to place the nut any where you want. I bought som rail buttons from Apogee and they have flange nuts which have to be placed internally to the tube. Or is screwing into the motor mount rings the way to go?

I've used rubber well nuts on a few rockets, including two HPR rockets that have flown on Is and Js. Each of these used fiberglassed cardboard tubes. Not sure how well bare cardboard would hold up to them repeatedly.

LOC tubes are pretty thick though. If you were to have problems, I doubt they'd be on the first few flights. Still, you might consider laying a fiberglass patch over the immediate area where you'll be placing the well nut, or at least soaking the cardboard around the holes in epoxy (or maybe CA).

 

[MarsLander]

If you are using WELL nuts, be aware that there are minimum and maximum grip ranges. Make sure you know the thickness of the wall, and match to the grip range of the well nut.

 

[FlyBy01]

I've built a few mid-power rockets with no issues, but have a couple of questions concerning high power.

1. Epoxy - I've ready 5-minute epoxy is not the strongest. I bought some T88. Is that the way to go, or should I get some 30-minute epoxy?
2. I bought some PC-7 epoxy putty to try on the fillets for my Loc Onyx. Should I avoid this for HPR?
3. Is it a good idea to mix microballons with epoxy for fillets?
4. This will be my first go with rail buttons. I've read some threads on the forum and one person mentioned using Well nuts with no issues. I like the idea of being able to place the nut any where you want. I bought som rail buttons from Apogee and they have flange nuts which have to be placed internally to the tube. Or is screwing into the motor mount rings the way to go?

I'm planning to build the North Coast Laser Lance to try internal fin fillets and rail buttons for the first time. Then I will start my LOC Semper Fi.

Use the T-88 and take your time building. Never used epoxy putty because of reading on TRF about it cracking off, never used it myself. T-88 makes good fillets but JB weld can also be used for fillets. Micro ballons are really a preference and just used as weight reduction. 2 methods for rail buttons I recommend:
1. Blind nut epoxied into wood, sanded to contour the body and epoxied into the rocket.
2. 3D printed mount with nut epoxied inside for insurance.

Remember to plan the bottom rail button mount as it is the har of the two.