29mm Tres!

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Well-Known Member
Jan 25, 2009
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Hi all,

I've got it really bad...BEFORE I was even outta bed this morning, I was thinking about what I was going to do with this chunk of LOC 2.56" tube I just got from Hobbylinc...

Looking at my half-finished Tres, (literally! the booster is PAINTED and the top part has no fins, no nuthin!), I got a wonderful idear...

And as you can guess by the title of this thread, I said to myself, "Why the heck not...go fer it!"

Basing the scale factor around the MMT size, it will be 1.61x scale. The booster will be about 29" long, based around the LOC 2.56" tube, and the sustainer will be based around LOC 2.14" tubing, with the tube being, again, 29" long. That will put the finished length of the entire rocket at approximately 70"!!!


I have already obtained a pattern sheet for all the fins and will have to figure out how to cut the centering ring on my drill press. I might have Eugene teach me the best way to do it, or possibly even get it custom cut. Lotsa possibilities. I will keep ya'll updated.

Originally posted by jetra2
I have already obtained a pattern sheet for all the fins and will have to figure out how to cut the centering ring on my drill press. I might have Eugene teach me the best way to do it, or possibly even get it custom cut. Lotsa possibilities. I will keep ya'll updated.


I am long overdue for a visit. Let me see if I can make some time to head over there this week and we can cut some rings. Your place works better since you have that workbench. Plus you have that way nifty Craftsman drill press. :)
Hi all,

Quick update.

I'm still in the designing stages for the 29mm Tres. Mainly, I am trying to figure out how to design the 3x 29mm cluster with the angled motor mounts...eek! My plan, so far, is to have a 8-10" long 38mm motor mount tube running up the middle of the 2.6" booster, with 1/4" birch ply CR's. The lowermost centering ring will be a direct upscale of the ring used in the kit Tres, but the problem I am have with that is figuring out the alignment. The problem is that I do not know how to mark the ring, once I cut the basic disk, for the motor tubes to be perfectly aligned. As I'm sure most of you have noticed on most any kit Tres', if you mis-align one of the MMT tubes, you'll get a bit of wobble on the way up. So, I don't want to screw this up with 4-15 times the power of the B's and C's used on the kit Tres - it MUST be PERFECT!

The sustainer will be based around a length of 2.1" tubing, likely PML or Giant Leap phenolic. The nice thing about this size is that I can use a stock plastic/fiberglass nosecone! It'll have a 29mm motor mount, with a copper or brass conduit running down one side of it for an e-match for staging. I am not decided as of yet if I want to use a XAVIEN or Perfectflite timer for staging, or if I want to go all out and buy a G-Wiz or similar unit. I'll likely go with a timer at first, simply because it'll be cheaper, but I am definately getting an altimeter at some point, and I might as well go for it all! Staging, deployment, altitude, the works!

Any help is MUCH appreciated and needed!!!

I love using the G-Wiz for staging and deployment in small(er) two-stage rockets. As long as you have a reasonable ignition on the booster and T/W is enough for a safe flight, the G-Wiz should detect launch. Whether the sustainer lights or not, you'll still get recovery... that saved our TARC rocket a few times :p

There was also an article by Roger Lipke in an HPR a while back about cutting your motor mount for intersecting tubes, as with canted motors. I'll see if I can get it dug up and scanned in.

Just tryin to get my ideas together for next year, but how did you dual deploy? I know you could not use bp, so did you use pyrodex? just wondering...
Pyrodex, Pratt canisters, and electrical tape worked out well. It's nice to have insurance on two-stage flights in case the sustainer doesn't light.

I have vivid memories from two or three years ago of a two-stager that Dave Flynn (I think) flew at our club often, usually I357T to H123W. One time, the sustainer didn't light. I remeber watching the booster pop out the chute, the sustainer keep going up, arc over, and smash into itty bitty pieces on the ground. From then on, I swore I would fly all electronically staged rockets with deployment backup. I think it's more common for the igniter to burn and the motor to not light than for the unit itself to fail, so as long as you have a charge backup, even if it's on the same unit as the staging timer, it'll at least get a chute out.
'nother update

This evening, I spent a good hour cutting out 2.6" rings for the booster. I still need to cut the center holes, but these rings are PERFECT! They're a "Pop-Fit" in the tubing, to the point where I'll likely need to sand them down a bit to be a good fit. Just going to have to do a bunch of marking and geometry on the rings for a nice fit, but I'm not TOO concerned about that. It's just gonna take some time.

I'm probably going with Sandman for the cone and transition sections. I'm going with XAVIEN for the timer, which will be a XDSRT-1 model. At $46, it's a good deal, I think. You get two separate pyro channels, and it seems to be very easy to set up for flight.

I have yet to acquire the 2.1" LOC tubing for the sustainer, so if anyone can point me to a source that will sell me one single tube for the retail price and cheap shipping, I'll be most grateful. Most places want to charge $6+ for shipping, and for this one item that lists on most places at $6.30, that's a bit extreme.

Fins will likely be 1/4" birch ply, at least for the booster, and I might actually go with G-10 for the sustainer fins, now that I think about it. The sustainer will be getting a 29mm mount.

First flight will likely be 3 F25's in the booster to an F25 in the sustainer. Drooling is completely acceptable, and if you are at the launch, completely required. Guidance will be with rail buttons on standoffs, if it will be necessary. We'll see.

I'm going to try and get a professional automotive paintjob. :D :D

Thanks for the interest, and please offer your input!

Thanks for the reply Jim. I'm trying to be as serious about this one as possible. Many of my other projects, like the Flea and Deuce up-upscales, are those that I've just lost interest in, simply because I can't get one part. It should be easy enough for me to get all these parts for this one together before I start assembly.

Friday, I bought a length of brass tubing for the igniter conduit on the upper stage, along with some 12min epoxy, CyA and fiberglass "tape". I am going to be using the fiberglass tape for reinforcement on the fin area instead of fully glassing it, which will just add a LOT of weight.