4x upscale Custom Tristar

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cls

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the Custom Tristar is a 2-fin-with-wingtips model. this was the 4th rocket I built as a BAR... ooohh soooo long ago ... January this year.


it is a good looker and a great flyer so was a natural for upscaling. since it is 9" x BT-50 equivalent, which is nearly 1", a single tube of 4" LOC airframe was a natural. the matching LOC 4:1 ogive nose cone is nearly perfect but I suspect the Custom nosecone is more like 3.5:1 ... anyways we can fudge that with paint.

this was going to be my level 2 project but those huge fins are kinda flexible... flapping out in the breeze... versus a J350, which is somewhat unforgiving. we'll fly it on H & I motors and see what happens...

maybe it won't be so floppy after I glass the fins. anyways rocksim puts max V at Mach 0.99 on the J350 so maybe we won't try that...


this picture is the 1x model. don't laugh, yes it is missing an wing tip. the wing tip made it home from XPRS and is somewhere in the garage...
 

cls

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and here's a picture of the two, together. the MMT is glued in by the top centering ring and the forward fin ring. the fins are just tacked in (lightly glued). I spent a lot of time getting the fins and the ends absolutely straight.

after this picture I put fillets on the inside of the airframe, along the MMT, and the centering ring.

I can't say enough about LOC's high quality parts and quick service. my order came right away and everything is top quality - especially the MMT rings.


if anyone wants I will post the rocksim file for this too.


the aft fin ring has "Kaplow Klips" and corresponding 6-32 T-nuts & 6-32 x 1/2" cap screws.

tomorrow: glass the fins, glass the MMT/fin/airframe joints, glue the aft fin ring in, glue the 1/2" rod launch lugs in.

I haven't decided how to mount the recovery system. I like baffle systems so maybe I will make a plywood bulkhead and put an eye bolt in it. but there's a lot to say for LOC's system - just glue a loop of string on the side of the airframe!


I have scanned the decals and am trying to make some 4x masks for spray paint. if that fails I might try a sign shop to get some vinyl decals.
 

Rocketmaniac

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Great Looking project, why don't you use a small "J"???? Something with a little less power than a J350......
 

cls

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good idea, something like a J220?

I was stuck on J350 because this is a 38mm and I was just guessing what might be available... but I'm up for ideas!
 

Rocketmaniac

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Originally posted by cls
good idea, something like a J220?
Well, availablity is the big question...... but Aerotech lists several small "J" motors.......... J90W, J180T and J275W.........


I got my L2 on a Pro38 J285...........
 

Rocketman248

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The J285 is a great small J. Great for when you don't want to fly too high, but still be able to say you flew a J.:)
 

cls

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... j90, j180, I love modest thrust and long burn motors... a ticket to heaven!

all good suggestions but these are all 54mm motors.

unfortunately too late! the 38mm motor mount is glued in!

I picked 38mm without really looking at the motor selection, but because I had just bought a set of Dr Rocket 38/240 /360 and /720.

maybe I will have to put a hybrid motor in it <evil grin>
 

teflonrocketry1

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Did you use my Fins on Fins simulation techniques to create the outboard fins in the RockSim design for the Tristar? Let me know if you need help. Could you please post the RockSim file anyway?

Bruce S. Levison, NAR #69055
 

cls

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hi Bruce,

yes I did fool around quite a bit with your fins-on-fins method. the Jayhawk and the Tristar sure look similar!

overall though I couldn't really see a difference in the sims and the stability curves. and the big disclaimer at the end of your article gave me some pause about trusting the results. overall I think Paul Fossey should just go ahead and put support for "non-normal fins" directly in to rocksim, since those are my favorite kinds of designs:) but I am not an aeronautical engineer so I don't know really how difficult it is to accurately simulate it.

anyways here is the rocksim file and I am grateful for your suggestions and critique.
 

teflonrocketry1

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CLS,

I took a look at your RockSim file, and that's how I would simulate this upscale Tristar! Let us know how it flies.

Good Luck,

Bruce S. Levison, NAR #69055
 

cls

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sorry for the delay in posting the following pictures.

we drove 370 miles last weekend to launch at ROC. I have paint for it but it's been too cold so the Tristar flew naked. we put an H123 in it and it went maybe 1500'. nice slow take off, a little bit of roll on the way up, good coast, ejection perhaps 1/2 second late after apogee - nearly perfect! except, the parachute stayed wadded up for a little while until the Tristar was falling fast enough to pop it open.

the Tristar descended gently enough but tipped a fin plate and broke it - just like the real thing! I half expected it because I made the fins out of 1/8" birch 3x plies. I will make a new end plate and put glass over the all the fins & plates.

I expected some fin flutter but didn't see any. I'm pretty happy with the parachute, I made it at 1AM Friday morning. The roll is gentle and I don't see much to do about it anyways as the fins seem to warp just a little, 1 or 2 mm, from changes in temperature and humidity.

next flight, I161! woo hoo!!


OK, first picture is body tube, glassed and sanded fins and fillets.
 

cls

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second picture is the glassed-in aft MMT ring with the screws for the Kaplow Klips; another view of fins and fillets ...
 

cls

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third picture is the whole rocket layed out on the floor showing the parachute
 

cls

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OK, I flew the Tristar at December's ROCStock. the flight was straight up and true with a little bit of roll ... slightly late ejection (about 1/2 second) and the parachute popped nicely ... gentle landing but broke a fin-endplate anyways.

no problem, I made a new endplate. the fins and plates are 1/8" plywood. I am trying to keep the rocket light weight. but it needs to be stronger, the model one breaks fins on landing too. so this time everything is covered in a layer of E glass and WEST epoxy. it's still light enough.

this week I painted it with lacquer. don't know why the nose cone came out lighter than the body tube. everything had grey primer first, then white lacquer, then blue lacquer on top.

here's a picture of the finished rocket, all painted. it's going to fly a few times on Saturday, wish me luck!
 

cls

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and here is a picture of the regular kit, next to the upscale.

enjoy!
 

sandman

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Sweet upscale!

simple but cool!

sandman
 

eugenefl

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Originally posted by cls
and here is a picture of the regular kit, next to the upscale.

enjoy!
Very nice project! I bet it's the first upscale of a Custom Tristar yet. Custom rockets never get the nod. It's nice to see someone upscaling one of their kits. (Ok, the exception here is Mark Brown's Razor which is really cool BTW.)
 

astronboy

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There is something to be said about elegant simplicity in design.
 
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