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mtmind

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I've been designing (which is always dangerous for me) and this is one of the manifestations of said designing. I'm calling it Trinity because it flies on multiples of three motors. Three 18mm motors in the ringtail sustainer, and three 18mm motors in the three separate booster pods. Here's a rocsim screenshot of it; though not the suggested paint scheme, I just used these colors for visibility.

The front:
 

mtmind

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I will post the stability info soon, I just found some of the dimensions I needed. And another thing, would anyone be interested if this were offered as a kit?

Peace :cool:

Mike
 

teflonrocketry1

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Could you post a RockSim file of this design? If you do, I will take a look at your Trinity design using a new simulation technique I recently developed for tubular structures (incldes tube fins, ring fins and side pods) using RockSim version 7.03.

Bruce S. Levison, NAR #69055
 

cls

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hey, I like it! I love ring fins and I have learned to really like clusters.
 

cussler08

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Dunno why, but I've always liked ring fin rockets...ever since I built a Starlight as a kid :D
 

rkt2k1

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Very cool design!

Mike,

Very cool design! I like the combination of cluster and ring fin, especially with the ring fin being the upper stage. With all that weight in the back how much nose weight did you have to add? What are the overall dimensions of this model, specifically length as this will affect the CG as well. Nice work using Rocksim on a difficult design!
 

mtmind

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I finally got the thing simmed out in rocsim 5 (demo) with LOC 5.38 tubing as the ringtail, but that tubing is .08" thick so it's a little heavier than I'd like. I simulated the ringtail as six fins of the same thickness as the ring and with a semi-span equal to the radius of the ring. One question I have about rocsim: the finsets can't be rotated to a given angle so with three and six fins they overlap, does rocsim ignore this or do they cancel out? The nosecone is six inches long birch with a one inch diameter core two inches deep, and the main body tube is now eleven inches long. The fin struts are two inch chord length and swept one inch back, and the little booster fins are supposed to be two per pod. The pods are two inches long and the fins two inch root chord with one and one quarter tip chord swept half an inch back. The main motor tubes are two and a half inches long with a quarter inch engine block in front. There's no recovery in this sim so that'll add a little weight but shouldn't compromise the stability, I'm thinking 18" since the upper stage is just under eight and a half ounces with unfired motors.

Here's the upper stage stability view:
 

mtmind

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Here's the new perspective view of the rocket:
 

mtmind

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I should mention that the ring tail is only semitransparent for visibility, in actuality this will be paper tubing and opaque. Yes I know it would be cool if it were transparent but I'm not gonna go looking for clear tubing.


Peace :cool:

Mike
 

teflonrocketry1

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Your simulations look pretty good to me! I had to guess at the fin span for the booster stage (I hope its 1") and I had to fine tune the ring fin CP equivalent fins. Attached is my RockSim version 5 file of your design.

RockSim 7 allows for a much better representation of a design like this. I just re-wrote my tubular fin simulation article for version 7 of RockSim. I will take a look at this design in the new software if you fill in the missing details. What is the angle between the booster fins on the booster tubes?

Bruce S. Levison, NAR #69055
 

mtmind

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That's pretty close. The bottom fins are gonna be 60degrees with relatin to the motor pod tubes, and the fins are all eighth inch basswood. Yes the boster fin semispan is one inch. I based my stability with the ring simulating fins and without the tube ring, I'm not sure what the ring does in rocsim; I guess if it's an Inside Tube it shouldn't matter. The launch lug is .246 OD and .22 ID paper in a fin root. And I've decided to change the main engine mount to three 18mm tubes 2.25 inches long with an eighth inch basswood block in front of them, said block having three .5 inch holes and serving as a thrust ring. This should cut aft weight a little and still seal the motor mount against accidental ejection venting. The main struts also have through-the-wall tabs extending .45 inches inward.

Thanks for the ROCSIM file, by the way. It's nice to have something I can just open and tweak instead of rebuilding every time. I'd buy RocSim but it doesen't do everything I need yet, at least not directly.


Peace :cool:

Mike
 

teflonrocketry1

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The tube for the ring fin allows RockSim to calcualte an accurate CG this doesn't affect the CP or Cd. The six flat fins simulate the rings CP and Cd.

See the attached RockSim version 5 file; I fixed the booster fins so they touch the walls of the motor tubes and have a one inch span. I also put the 0.45" through the wall tabs on the sustainer fins and put the tabs between the motor tubes. I set the launch lug to the correct dimmensions an placed it at a fin root. Set the fins thicknesses to 1/8" basswood and put in the bulkhead with the shorter motor mounts.

Is this a better simualtion?

Bruce S. Levison, NAR #69055
 

mtmind

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That's it folks, that's trinity. I would like to thank Bruce for all the help with the rocsim file, it's all acounted for and accurate. Now all I have to do is put one together and do some test flights. I'll try some different combinations of motors and see what looks most promising for clean flights. the C6-0/C6-7 combination simms out to 2112ft max altitude with a top speed of 307mph. However, the optimal delay is calculated to be 7.72, which is a little longer than the estes delays which seem to be closer to 6.7.

More to come, I'll post when I can.

Peace,

Mike
 

airforce

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Mike,
It looks fantastic.
What's the altitude look like with just one stage????
Our field won't handle 2,000 plus feet.
Thanks
 

mtmind

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I have screenshots of the sim lists. The max Acceleration is in meters/second<sup>2</sup>, the velocities are in MPH, and the altitude is in feet. This list is the single stage flights.
 

mtmind

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OK So now I have this design and I want to build it but I need a part, namely the ring tail. It was based on LOC 5.38" tubing, but I could change it for Aerotech 4.546" tubing pretty easily. I need a 2 inch long piece of one of these, so if anyone could supply that I would be grateful. I don't mind paying for it and postage if necessary, but it's not worth buying the full length just for the 2" piece because I simply don't have that kind of funding right now. It doesn't have to be exactly 2" either, if it's a little long I could trim it so if you've got a little 3-5" scrap you want to send that's fine. I can send a check, MO, paypal if you like. And thanks to whoever hooks me up.


Peace :cool:

Mike
 

gerbs4me

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That is one cool design:)
sorry I have no scrap for you, if I did I'd give it to you
 

Rocketmaniac

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Originally posted by mtmind
I need a 2 inch long piece of one of these, so if anyone could supply that I would be grateful.
I only have a 7" piece of LOC 4" body tube...........
 

teflonrocketry1

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Mike,

Do you have any oat meal? Measure the carboard container diameter it should be very close to what you want.

Bruce S. Levison, NAR #69055
 

mtmind

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I can't belive I didn't think of that! :rolleyes: I don't have any outmeal, but I've got an old Hot cocoa container that measures about 5" in diameter. And it's not three feet away holing my pencils right in front of my face!

Thanks for saying something, I must be loosing it...


Peace :cool:

Mike
 

powderburner

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On another thread here on TRF we went through some similar ideas. You can try using posterboard stock (the light cardboard, about 2 ft x 3 ft, that they sell at W-mart for kids to make posters and school projects on, about 50 cents per sheet). Cut a strip and roll it to whatever diameter you need, roll it up until it is as thick (or thin) as you need it. Or if you want transparent plastic, there are lots of products that come in clear plastic jars with cylindrical sides (peanut butter, gallon pickle jars, one-liter and two-liter soft drinks, etc).
Look around the house with an eye on shapes and sizes, and start getting your excuses ready for why there is a pile of pickles dumped out in the kitchen sink.
 

mtmind

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Ok so it's been forever since this thread was active but I finally got trinity put together, well, mostly.

Here's the sustainer standing at attention.
 

mtmind

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And these are the little boosters for two stage flights. When I get some motors I'll get a picture in flight configuration.
 

Fore Check

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Wow, that 3 x C6-0 to 3 x C6-7 ought to be a wild flight!

Be sure to give us a good launch report when you get this one completed.
 
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