Semroc Centurion

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Random Part-time Hobbyist
Jan 17, 2009
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I always liked the clean appearance and simple paint scheme of Semroc's Centurion. I recently finished building mine, but did a few things differently.

I bumped up the horsepower and substituted the stock 18mm motor mount with a 24mm motor mount. Semroc sells a motor mount kit that fits perfectly in the 1.64” diameter body tube, which makes the swap even easier. I purchased this motor mount kit (Semroc part number EM-9-16P) for only $3.25 from Construction of this mount is identical to the standard 18mm mount with the kit. To handle the larger motors, I opted to use 3/16" launch lugs instead of the 1/8" lugs that came with the kit.

The Semroc Centurion’s body tube comes in two pieces, and the joint is where the ejection baffle is located. After gluing the baffle to the lower body tube as instructed in step 9, I decided to make it a zipper-less design. I glued the nose cone and eye screw to the upper body tube, so instead of having the nose cone separate from the upper body tube, the upper body tube would separate from the lower body tube. Since the nose cone was now an integral part of the upper body tube, I added a bit of Elmer’s Wood Filler (thinned with water) to the nose cone/body tube joint for a smooth seamless finish. I used a length of Kelvar shock cord for the section between the parachutes and the upper body tube.

I painted it with Rustoleum Gloss Black and Gloss White.

So, from the outside it looks totally stock, but inside it has a zipperless body and can be powered with an E motor.

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I flew this Centurion for the first time yesterday on a D12-5. It lifted off beatufully, but at ejection it suffered a minor separation. The bottom half lawndarted and took a nice core sample, and the top half floated away under twin parachutes. I eventually recovered the top half. The glue joint between the forward baffle and the coupling tube wasn't strong enough to handle ejection when the shock cord pulled on it. It was an easy fix and will be back in the air soon.


Jeff, great idea for the modifcation on Centurion. Too bad it seperated at the baffle joint. Hopefully you didn't have to chase the top half into the corn. Oh how I miss launching at the sod field with MASA.

--- Ron
From the launch area it looked like it went into the corn. Luckily it touched down about 20 yards from the corn. You used to fly at the MASA sod field now you live in Portland?
This is quite the interesting picture! Deep surface probe? :D


Caption: "Jeff always finds a way to win the Open Spot Landing event at our section meets."

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Thanks, Mark! I laid down on the ground when I took the picture to get a different perspective.

It is a bit deceiving though... it looks like the entire front end is buried, but really the end of that section ends a few inches in front of the decal.
You used to fly at the MASA sod field now you live in Portland?

Yes. I used to live in MN and was a MASA member for the last couple of years. BTW, the picture is priceless.

--- Ron
Thanks! I joined MASA in late 2005 (I think).
We saw quite a bit of Ron before we scared him into moving west. :rolleyes:

Hi Ron! Good to hear from you. I have to admit, though, that I still haven't gotten around to restoring the Black Knight pinball game that I bought from you.

I had always like the looks of the Centurian, too. A couple of years ago, while brousing through SEMROC's website, I saw the fin set....then the nose cone....and decided to clone it!! Did the "ding-ding-ding" go off in my head? Noooo.....Then of course [you know where this is going, don't you?] SEMROC releases the kit! :y: Since then, I have suspected that Carl is reading my thoughts, so he can stay one step ahead of me. OK, Carl, let's test this one...I'm thinking "Saturn V",, that's not it......;)

In any event FatBoy, great looking model and I'm sure she'll be flying again soon.
Since then, I have suspected that Carl is reading my thoughts, so he can stay one step ahead of me.
Quite a few of us have wondered the same thing. It happens because Semroc is extraordinarily well attuned to the hobby rocketry community.

Thanks, Rocketcrab. It is already repaired and ready to launch again.

Ron... Next time you are back in town, came out to a MASA launch.
I have been blessed by never have a engine cato in all my years of flying rockets. now parachute failures and ejection failures yes. I won't even talk about the "hamster" incident.

Andrew From Texas