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7.5" Patriot

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Ryan S.

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This thread will start the documentation of the 7.5" half Scale Patriot Missile that I am in the process of building. It is not really half scale at all, the tubes are slightly smaller, and the fins and overall length are much longer.

I chose this rocket because I really like the looks of the real thing. Although stability has been a problem due to the small fins, I have worked through the problem, after much conferencing with Dan Patell, and some with David Reese. After I resized the fins to ensure stability on the biggest of motors, I began construction.

The rocket has a 98mm motor mount and is capable of taking up to a 45" or longer motor. I am using zipperless deployment, however this has the possibility of being swtiched to regular deployment.

here are some of the parts;

 

Ryan S.

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here is a shot of the Centering rings and fins. The fins are 3/28" birch and the CRs are 1/2" birch

 

Ryan S.

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here are the couplers, internally glassed for strength

 

Ryan S.

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here is the aft CR drilled for T-nuts (motor retention)



and the backside

 

Ryan S.

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here are the top 3 Centering rings drilled
 

Ryan S.

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here is the MMT with CRs. The Allthread is to strenthen the recovery point, since the top CR is only glued to the body tube and the mmt does not run through it

 

Ryan S.

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here is the fincan with the fins tacked on with 5 minute epoxy

 

Ryan S.

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and the booster test fitted, it fits like a glove; PERFECTLY!

 

Ryan S.

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this kinda gives you a taste of what the rocket looks like



 

gerbs4me

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wow
you really done a great job so far, the Patroit is one cool looking rocket, keep up the good work:)
 

LaneKG

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loopy

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Wow! That looks great! Oh, now Clean Your ROOM!!!! :D


Loopy
 

Ryan S.

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cool, that looks like the PML kit. I chose not to do that since the MMT is kinda small, and I want the chance to fly bigger motors. PLus, the PMLs fins arent scale, mine are scaled to the original rocket, but are oversized for the rocket I am building.

This rocket has yet to get glassed, but it will get one layer of 10oz from Aerosleeves.
 

Ryan S.

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did a little more work. I need to put internal fillets on the fins where they meet the MMT. There are 2 reasons for this; strength, and the fillet provides and easier transition from the fin to MMT when it comes time to tip to tip glass the rocket.

here is the first picture of the fincan in the sun;



I fillet the Tnuts with Dow 111 to keep epoxy out

I made dams out of masking tape. Since the rocket is out in the sun the epoxy will thin out and could easily run and make a mess. There isnt much space under the fins, but there doesnt need to be.



Lastly, the actual fillets. I didnt use straight out epoxy for a couple reasons; first I know the adding more epoxy does not really add strength to a fillet, and doing this would take a ton of epoxy, which would just add uneeded weight, so that option was out. I would have added filler, but that weakens the epoxy and I wanted a nice strong joint.
So I went at it, and chopped up some old 6ox fiberglass until I had a big fuzzball, this should add tremendous strenth to the joint, and it also took up space, so I did not have to use as much epoxy.

 

rvanstone

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Ryan ,
That looks great can't wait to see the rocket completed !
Question , the section after the motor tube where you have thread rods up to the top center ring used for ? or needed ?

Ron
 

Ryan S.

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Originally posted by rvanstone
Ryan ,
That looks great can't wait to see the rocket completed !
Question , the section after the motor tube where you have thread rods up to the top center ring used for ? or needed ?

Ron
that is for the centering ring that sit at the top of the coupler. In this design the coupler is glued into the booster and the rest of the airframe sits on top of that. At the top of the coupler the centering ring sits. I did not feel that just the epoxy bond to the coupler would be strong enough to hold up to repeated seperations. Maybe a couple times, but if I have a hard ejection, the CR would probably rip out and then the booster would come in ballistic. So I ran allthread to the top and middle CR to try to distribute the force over through the whole booster.

I will be including more pictures later that will better describe this
 

Ryan S.

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I finished the internal chopped glass fillets today. That is 4 in one day, pretty awesome, but the sun was out so the epoxy cured in no time. So I got some more pics of the rocket.



here is another view



and lastly I bought some Ubolts and made sure they fit right in the other two bulkheads. Here are all three together

 

Ryan S.

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just a side note, please don't associate me with any certian groups of people due to the Birkenstocks, they do not carry those...implications.

Hey they are comfortable shoes! :p :p
 

Ryan S.

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I put the aerosleeves on the rocket, came up short by a couple inches, but that should be solved with the Tip to tip glassing on the end of the rocket.

Rocket with Aerosleeve



and the tube wetted out



I also did one quadrant of internal glassing over the internal fillets



and last, the glass wetted



now to work on the altimeter bay, I am tired of glassing, I will probably do more tommorow
 

Ryan S.

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one note, those arent bubbles around the tube, that is clear tape I wrapped around that as part of an experiment, more on that later
 

DPatell

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Looks great Ryan, keep up the good work.

What do you plan the first flight to be?
 

rvanstone

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Ryan,
Really like this rocket !!! Great job !!
I am looking to do my level 3 with a Patriot and haven't decide to use a kit or start from sracth.
After talking with PML what size fins did you settled on ?
What does the thread rods proovide for your Patriot

Ron Van Stone
 

Ryan S.

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Wow, I was suprised to see this thread restarted.

Anyway, the threaded rod for my patriot provides some extra support for the top centering ring. I did not put it there for any type of "stiffness" or anything, but simply to distribute the stress of recovery over a few more rings. I wouldnt have done this, but my motor tube does not reach the top centering ring, so the ring is only glued to the coupler, by passing some allthread through it, it was attatched to another centering ring which was glued to the motor tube and the body tube. A little extra insurance with not too much added weight.

My rocket used enlarged fins, that were actual scale patroit fins, only the fins were not half scale, more like 3/4. This gave me added stability, however, I still do use some noseweight for the rocket. The Dimensions for my fins were:

19" root
8" tip
6.5" semi span

My rocket does have noseweight, on a 7600 Length motor my nosecone weighed 13 lbs. This is pretty heavy, however, the loaded weight with the 7600 sized motor was only 60 lbs which is pretty reasonable. With a 5400 (4 grain 75) the rocket weighed 54lbs.

It has flown twice to 5903' on a 5400Ns load and 8500' on a 9600ns load, both were perfectly straight. This weekend it is flying on a 6000Ns load.

Here is a picture of the rocket (painted!)
 

Ryan S.

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thats my "what the heck are you doing?" when my mom took the picture.
 

DPatell

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Oh, I thought it was your "I'm a celebrity" look


:p
 

Bowhunter

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Ive had my eye on a PML 1/2 scale Patroit and looking at this it just makes it worse. Now I got to get one
 

Mag

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Real good work, let me ask you this, "Why do you have two U bolts on a bulkplate?" I use one eyebolt in the center.
Eager to know because I am working on a Magnum cluster with 54mm central and four 29mm outboards and added an extra fin instead of three fins for better stability.
Mark
 

Ryan S.

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Originally posted by Mag
Real good work, let me ask you this, "Why do you have two U bolts on a bulkplate?" I use one eyebolt in the center.
Eager to know because I am working on a Magnum cluster with 54mm central and four 29mm outboards and added an extra fin instead of three fins for better stability.
Mark

I just like the idea of dispersing the shock of deploment over the whole centering ring, rather than two small points, there are two. If I could have put 1 ubolt in the middle for any of these centering rings, I probably would have used that method, but since I couldnt, two on either side was a better idea. Also, I used threaded rod in a few places, so two u bolts put stress on all the threaded rod. Just a little extra insurance

Here are some flight pics, this is the first flight, I dont have any from the second, minus the picture of me holding it. I beleive Dennis Lappert took these pictures, however, I am not sure, they are from the NERRF website



 
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