Lessons learned building L1 rockets

David Erbas-White · 2005-03-14T07:20:08+00:00

Well, I've just finished the construction phase for my level 1 rocket(s). I still have to do the final sanding/painting, but the 'construction' part is done. And I've learned a few valuable lessons that I thought I'd share. BTW, I'm planning on using my PML 1/4 Scale Patriot for my L1, and maybe even eventually for a L2. I built it a bit stronger in order to (hopefully) assure it will survive an L2 attempt. I've got a Black Brant Vb as my 'backup', in case preliminary flights (G-level) with the Patriot don't work out, or something similar. Here are the things I've learned:1. The 50-pack of epoxy mixing cups is not enough. Get two.2. When using a clothespin to hold a shock cord in place while drying with epoxy, you will either remove it too early and the shock cord will come loose, or you will wait to long and the clothes will be glued as well. There is no middle ground.3. When using JB Weld to glue an engine retainer to the back of the motor tube, you should smear the JB Weld around the outside of the tube, using very little on the inside of the retainer. Otherwise, you will get little drops of JB Weld on the inside of the motor mount tube, and you will not discover them until after the JB Weld has fully cured.4. It's very difficult to file JB Weld from the inside of a motor mount tube.5. Not removing all the JB Weld from the inside of a motor mount tube can score your brand new Dr. Rocket casing.6. When trying to get that last little bit of epoxy out of the container, bear in mind that the first part that you poured in has been 'mixing' for a while with the first part that was already in the measuring cup.7. Trying to find out where you put the mixing stick after you've already added the two parts of epoxy together is not the best way of doing things.8. Expanding foam REALLY DOES expand about 25 times. Really.9. Placing the rocket being worked on on top of two expensive oak CD cases is a sure fire invitation to spilling epoxy on them.10. Placing a rocket...

Mar 14, 2005 27 Replies

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Kevin Trojanowski 21 years ago

50, so far, has been over a 5 year supply for me. Leave the mixing stick in as the leftover cures, then use the stick to help pop out the leftover.

Your Dremel is your friend.

Keep 'em handy!

Not always... Depends on temp and other factors. But NEVER contain it such that when it pressurizes whatever it's in the container (which may be your fin can!) distends. In tight areas, mix several small batches.

Yep. And if it doesn't knock it over, you will, by accident.

-Kevin

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Niall Oswald 21 years ago

Quote from Mike Roberts on UTR:

"Check out the Drake "Doc" Damerau's Rocket Materials site at

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.org version dosent seem to work currently. Sspecifically the recovery harness testing section. This is a very useful resource and has some data that also shows quite graphically why epoxying tubular or plain single layer nylon webbing in to an airframe is a seriously bad idea!"

Should 'redesign your kit for zipperless recovery' be on the list perhaps?

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Jerry Irvine 21 years ago

Perfection of laziness :)

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Bob Kaplow 21 years ago

I would basically agree with this.

My rule of thumb for competition models is that if a model designed for class X can be flown on a class X+1 motor and not shread, it's overbuilt. THat would require unique models for each class. In reality I often use a model for the next class down, and someties for the next class up. I ahve also thermalled away a D RG on a B6-2 that I needed for NARAM a month later.

Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD!

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Cliff Sojourner 21 years ago

our level 1 machine was a blue Ralphco crayon with 1/8" plywood fins,

1/8" CRs, Kaplow-style baffle and clips, all glued together with yellow glue. (and 10' elastic shock cord!) it's survived many many flights on everything from F40s to H220s.

I built another similar crayon but used epoxy instead of yellow glue. it's heavier enough that it doesn't fly well on F motors.

yellow glue works great!

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Bob Kaplow 21 years ago

The problem with the late Ralphco crayon banks and similar is that neither yellow glue nor epoxy sticks to the plastic. I've had to use hot-melt, silicone caulk, and even pop-rivets.

Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD!

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Cliff Sojourner 21 years ago

Gorilla glue (urethane) works great!!

I don't use the bottom cap because of the gluing problem, also I don't like the looks of it on the rocket.

for the nose cone I cut a plywood disk that just fits inside the lip; Gorilla glue works fine there. Used to use silicone caulk which would last a few flights.

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