Semroc Centurion

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JAL3

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The Semroc Centurion was one of my earlier efforts. It has been a good performer even though the fin alignment is something of an embaressment. It's development and history can be followed here: https://flickr.com/photos/[email protected]/collections/72157607448670088/


Today, I decided to start work on building a booster for it. Semroc recently released a CHAD booster designed to fit rockets with the ST16 body tubes. One of these is the Centruion.

The kit consistes of a pair of paper shrouds, an engine hook, a motor mube, a body tube, a pair of centering rings and a series 16 coupler tube.

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JAL3

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Construction begins by cutting out the 2 transition shrouds from the provided piece of cardstock. The outlines are marked and its just a matter of being careful with the scissors. Once they are cut out, they are given a bit of a roll. White glue was then applied sparingly to the marked tabs and the ends were pressed together and set aside to dry.

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JAL3

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Next up, the larger of the two centering rings is carefully punched out. Contained in its center, is a smaller centering ring for use with the motor mount. This was carefully removed and set aside.

The coupling tube was set down on the centering ring and centered so that an even but very small bit of ring was exposed all the way around. White glue was then used to tack down the coupler from the inside. When the tacks were stiff, white glue was used to fillet all around the circumference.

The photo of the coupler/ring connection was abducted by UFOs.

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JAL3

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The engine hook was inserted into the precut slit in the motor tube. The two motor mount centering rings were then separated and cleaned up, leaving the oval gas ports in place for now. One ring was slid into place over the point where the engine hook pierces the tube and the other 3/4" from the aft end. The rings were then secured with gel type CA as per the recommendation of the instructions. When the CA had set, the gas ports were poked out.

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JAL3

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The motor mount was installed in the body tube by the simple expedient of pushing it in and aligning the aft ends of the tubes. The mount was installed with white glue.

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JAL3

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The centering ring with the coupler tube attached was slid onto the body tube on the end opposite the engine hook and aligned so that it was straight and flush with the end. It was sealed in place with white glue and allowed to dry. Fillets were run around both sides of the ring.

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JAL3

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After the coupler/tube joint had a day to set, it was time to start installing the transitions. The short one went on first and slid down to the coupler ring without any problem. It was seated with white glue and allowed to stiffen up some.

transition-1.jpg
 

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After a bit, the other transition was test fitted. While the first one fit just fine, the second, longer one was a tougher case. I needed to sand away some of the smaller end in order to get it to fit over the tube. WHen I did get it on, I lined its seam up with that on the other transition and both were aligned with the engine hook. White glue was again used to set it in place.

transition-2.jpg
 

JAL3

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The last remaining centering ring was puched out of its backing and slid over the motor mount inside the bell of the after transion. When it was even, white glue was again used to fasten it and the whole thing was glazed over from the inside with more white glue.

transition-3.jpg
 

JAL3

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When the glue had set a little more, I took the booster and tried to give it a trial fitting into the Base of the Centurion. It was tight and will need some more sanding, particularly to get past some of the glue rivets I had originally installed. That would have to wait for another session, though because duty called.

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JAL3

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When I got back to work, I used a combination of #100 sandpaper and a rat tail file to smooth out the aft end of the ST16 tube of the Centurion. After a few fits and starts, the booster fit in just fine.

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JAL3

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I masked off the coupler tube and then proceeded to prime the booster with Kilz.

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AKPilot

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This is a great build thread John. You've even inspired me to pick a couple of these up.
 

JAL3

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This is a great build thread John. You've even inspired me to pick a couple of these up.
I just hope Estes comes through with their end of the bargain!;)
 

JAL3

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When the Kilz was dry, I was somewhat surprised to see that it did not need much sanding. Usually its a bit blobby and speckly but that was not the case this time and after a single token swipe of #600 sandpaper, I went right to the painting. The recommended color is a gray but the only gray I had on hand was automotive primer and that's not what I wanted. I finally settled on a flaky mettalic silver that looks more in keeping with a rocket nozzle to me. It took two coats.

I do believe its ready to try. I have a few old A10-0s sitting around but they won't last long. Estes, are you listening?

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JAL3

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I removed the masking from around the stage coupler and liked what I saw of the silvered nozzle but did not care too much for the glaring white of the inside. I wanted to do something about it even though it would rarely be visible.

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JAL3

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I decided to hand paint the white with a Tamiya bronze paint. It took 2 coats and could probably have used a third for more even coverage but I'm happy with it.

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JAL3

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I had one more photo of the finished product.

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El Cheapo

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In reading your build thread, I figured I'd slap one of these boosters together that I received as a freebie from Semroc. It is as simple as described w/no hidden tricks although I did punch out the elliptical holes in the ring set prior to assembly for fear of CA'g them in place.

Once finished, I noticed that it's almost a perfect fit for any toilet paper tube rocket with minimal alterations to the TP tube to fit snug.

The Centurian instructions state to inset the motor assembly 3/4" into the main body tube which would put the buster flush against the BT. That would leave the end of the sustainer motor approximately 1/4" from the top of the 13mm booster motor tube. Is that what it appears to be in your Centurion & Booster measurements? I'd really like to adapt this to some toilet paper tube finned rockets.

Thanks
 

JAL3

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In reading your build thread, I figured I'd slap one of these boosters together that I received as a freebie from Semroc. It is as simple as described w/no hidden tricks although I did punch out the elliptical holes in the ring set prior to assembly for fear of CA'g them in place.

Once finished, I noticed that it's almost a perfect fit for any toilet paper tube rocket with minimal alterations to the TP tube to fit snug.

The Centurian instructions state to inset the motor assembly 3/4" into the main body tube which would put the buster flush against the BT. That would leave the end of the sustainer motor approximately 1/4" from the top of the 13mm booster motor tube. Is that what it appears to be in your Centurion & Booster measurements? I'd really like to adapt this to some toilet paper tube finned rockets.

Thanks
I have not measured it but that sounds just about right.

I hope to try mine soon.
 

standardrockets

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Very sharp!

I picked up a Centurion and the booster in anticipation of the new motors.

But have not gotten around to it yet. Other projects in the works are consuming my time...
 

FatBoy

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John, that is a really nice thread you shared with us. Thanks!
 

hcmbanjo

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Great build posts on the Booster 16.
I made mine last week, no problems. Considering the paper shroud construction, I found it very strong even without coatings with white glue.

I had one concern though. Did you find it strange the shroud wrap seams were opposite? Meaning, one overlapped to the right and the other to the left? If I were to build another, (on one shroud) I would make the glue tab on the opposite side.

This is a cosmetic observation, nothing to take away from the quality of the kit. Those laser cuts on the ring card were tight and clean.

Hans "Chris" Michielssen
 

El Cheapo

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I don't think the paper shroud needs any reinforcing w/CA or otherwise. However, I do think I'm going to CA the exposed portion of the lower shroud that extends passed the lower centering ring. Just some reassurance should it land there to try and keep it from getting dinged.
 

Indiana

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Did you find it strange the shroud wrap seams were opposite? Meaning, one overlapped to the right and the other to the left? If I were to build another, (on one shroud) I would make the glue tab on the opposite side.

When I built mine, I cut the overlap off and glued it inside, so there is no "bump".

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JAL3

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Great build posts on the Booster 16.
I made mine last week, no problems. Considering the paper shroud construction, I found it very strong even without coatings with white glue.

I had one concern though. Did you find it strange the shroud wrap seams were opposite? Meaning, one overlapped to the right and the other to the left? If I were to build another, (on one shroud) I would make the glue tab on the opposite side.

This is a cosmetic observation, nothing to take away from the quality of the kit. Those laser cuts on the ring card were tight and clean.

Hans "Chris" Michielssen
I noticed that after it was put together. FOr me, it doesn't matter. If I were to try and do a showpiece, I'd probably leave off the tab, but the ends and use an inside strip.

My parts were A1.
 

JAL3

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When I built mine, I cut the overlap off and glued it inside, so there is no "bump".
That's what I meant in my last post but such niceties are overkill when done on the rockets I degredate with my attention. I've gotten to the point where they pass muster from a distance and no longer get laughed at openly on the flight line but finishing is still my biggest weakness.
 

JAL3

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The Centurion with its new booster got its first outing today. It was very windy but I wanted to fly anyway.

The booster was loaded with one of my dwindling stock of A10-0s and, like a dunce, I put an A8-3 in the sustainer. It took off fine and staged at a low altitude. I like that. I can see it. I got my booster back.

The staging was flawless. The sustainer flight was not. The A8 is not on the list for this rocket and it was underpowered even with the initial speed of the A10. It arced over and hit the ground before ejection. Even so, no harm was done. I'm going to be flying this booster more often.

I hope Estes makes good on its promise!

A video of the flight can be seen here: https://flickr.com/photos/[email protected]/3279560975/

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