Semroc Sat 1B 8 eng. cluster

Hello all,

I saw somewhere someone did a 8 engine cluster on a Semroc sat 1B but can't remember where. Any help?

matt38 said:

I saw somewhere someone did a 8 engine cluster on a Semroc sat 1B but can't remember where. Any help?

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Check Sport Rocketry magazine's coverage of NARAM-50. The Contest Director, Jim Filler flew one.

I'm even on this forum :clap:

Did you have a question ?

Thanks! Do you have the details on the build? I am new to this and any guidance would be great!

I did not document an actual build thread. When I originally did the model I did a "boilerplate" first to work out the bugs along the way. I installed a staging timer for the scale flight as well.

As you mentioned the first stage took off on a cluster of (4) C6-3 motors and (4) A10-PT around the perimeter. When the C6 motors burned out, the timer ignited the upper stage single C6-3.

If you only want to add the (4) 13mm motors and fly a single stage flight, you can do that fairly simple. Just cut 4 holes for the 13mm motor tube in line with four of the tank tubes. Add your tubes to the ring when building the 4 motor cluster mount.

Be sure what ever you do, check your CP / CG relationship with the motors installed and the model full up ready to fly.

The second picture shows that only 7 motors lit on the first test flight.

The third picture shows the details of the upperstage mechanism.

zog139 said:

I'm even on this forum :clap:

Did you have a question ?

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OH MY GOD!!! IT'S JIM FILLER!!! *Swoon*... *faint*.

zog139 said:

The third picture shows the details of the upperstage mechanism.

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Jim, is that fin on the right hand side of the picture deliberately warped to induce a roll, or is it a picture artifact?

Thank you. I assume that the outboard motors have no delay? I am just going to find centering rings for a 18mm tube to fit the BT 51 tubes on the rocket.

I tried to look up Estes plugged motors and only could find the A10-PT's. Any other outboard motor options?

matt38 said:

Thank you. I assume that the outboard motors have no delay? I am just going to find centering rings for a 18mm tube to fit the BT 51 tubes on the rocket.

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Yes I selected the 13 mm tubes to use the A10-PT ( plugged motors ) If you want to step up to 18mm motors there are no plugged versions. What you could do is use the B6-0 and stuff the front end with wadding.

Again I remind you to be sensitive to the CG & CP. If you go to 18mm outboards you will be adding even more weight to the rear of your model.

Estes had stated sometime back they were going to reintroduce the 13mm
A10-0 and the 18mm A8-0 ................ we'll see !!!!!!!!!!!

Thanks for all your help. I think I will follow your lead and go with the A10's

GuyNoir said:

Jim, is that fin on the right hand side of the picture deliberately warped to induce a roll, or is it a picture artifact?

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Judging from the first and third pictures I am guessing that the fins fold in for launch and are deployed on staging in flight.

I would like to know more on how you built the upper stage fins.

What timer/ignitor combination did you use?

Shade said:

Judging from the first and third pictures I am guessing that the fins fold in for launch and are deployed on staging in flight.

I would like to know more on how you built the upper stage fins.

What timer/ignitor combination did you use?

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That is correct, when the fins are folded over they slide down into the added body tube coupler that extends up from the S4-B interstage coupler. The fins were made from balsa because they would not be seen for static judging. They are very simple to make. After determining the proper size and hinge cut location, I used a piece of nomex cloth about 1/2" wide across the back of the seam. On the opposite side I used strips of rubber bands CA'ed in place.


When I flew the model I used the Perfectflite mini timer ( you can see it in the picture ). I did some testing ahead of time and decided on using easy and went with a 9 volt battery and a standard Estes solar ignitor with extensions made from 30 guage wire. All three times I flew it ( 1st flight with the boilerplate flights 2 & 3 were the scale model itself ) it staged just fine. The 2nd and 3rd flights had all 8 motors light at liftoff. :shock: