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cobra1336

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Building a 1/2 scale Patriot. The air frame is 8". I converted it to a DD using the 12" coupler for an E-bay. Is there a rule of thumb as to how far the E-bay should slide into the aft section that it will eject from.
 

kandsrockets

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Building a 1/2 scale Patriot. The air frame is 8". I converted it to a DD using the 12" coupler for an E-bay. Is there a rule of thumb as to how far the E-bay should slide into the aft section that it will eject from.
I was told to use whatever the diameter of the tube is that is how much you should have for the length of coupler going into the tube. So for a 8" tube you should have 8" going into the tube.
 

Gabe Osborn

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I agree. You definitely want your coupler on each side to be at least as long as your body tube diameter. Especially for high performance flights.
 

cobra1336

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The ring slid down on me when it was drying, I only have 5" on the aft side. I can not flip it around because of the cut I made on the ring. Not a perfect cut.
 

MarkM

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The ring slid down on me when it was drying, I only have 5" on the aft side. I can not flip it around because of the cut I made on the ring. Not a perfect cut.
A little short. The use of sheer pins should help with any "wobble" the coupler may make within the body tube due to the shorter length. Three or four sections of 1/16" styrene rod works well.
 

cobra1336

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That was my next thought to install shear pins. Is this acceptable ?
 

blackjack2564

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Same thing happened to me. I resolved it by cutting the band off and sanding the coupler smooth. this gave me the extra inches of coupler in the tube needed for a nice fit. A sheet of paper wrapped around the tube gave me a nice even edge to sand the tube square.

With the BP's adding another inch, I have 6 1/2in for each tube.
Just drilled my vents in between the joints, half hole on each.
4 1/4 in holes to vent the bay and 4 rivets to hold coupler in airframe.
I twist and tape the wires, but switches can be done by centering them also, like the holes.
This is my 7.5 in Bananas Rocket, flys great on everything so far up to and including N's . Apogee event right on the money!
4 shear pins 4-40 to hold NC. Both rivets and pins located 1 1/2 in from edges of tubes.
Hope this will help you.

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blackjack2564

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Many ways to use tie rods on bay.
I used 3/8 hardware through the center to keep stresses in line.
Added a 1/4 rod along side for mounting electronics. This way all my sleds are for 1/4 rods and can be used in any rocket.
If you do this always have the fixed eyebolt on the apogee side and the removable one with the coupler nut on the main side. This keeps it inside the payload tube, where it's less likely to be in harms way.

Yes a couple of pins to snug up the fit are fine. I have done this on several projects.

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blackjack2564

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Jim you coming up to Red Glare Again with Tim?

Ben
If he's there so am I. Hopefully no conflicting dates........ready to unveil my latest secret project.......
.......................................''CHERRY BOMB".........................

stay tuned for this one. Hopefully it will finally get me past that elusive 20,000 ft mark!
 

ben_ullman

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If he's there so am I. Hopefully no conflicting dates........ready to unveil my latest secret project.......
.......................................''CHERRY BOMB".........................

stay tuned for this one. Hopefully it will finally get me past that elusive 20,000 ft mark!
FYI MDRA has a 16,900' waiver.

I do have a Super Polish Rojo N3300 in the 76-8000 case I want to try. You up for it? I am going to fly it on the Test Stand first and see what it comes out to, myself and a few guys don't believe it will be an N3300 (9800Ns) in the 8000Ns 76mm case. Even though it has a 1.06" nozzle and will have mach diamonds out the @ss :p

Ben
 

blackjack2564

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Some how I missed your offer Ben. Heck yeah, if we make it I'll take you up on that! Thanks.
 

5x7

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FYI MDRA has a 16,900' waiver.

I do have a Super Polish Rojo N3300 in the 76-8000 case I want to try. You up for it? I am going to fly it on the Test Stand first and see what it comes out to, myself and a few guys don't believe it will be an N3300 (9800Ns) in the 8000Ns 76mm case. Even though it has a 1.06" nozzle and will have mach diamonds out the @ss :p

Ben
Ben, 9800ns is an M. Over 10240ns is an N.

Should be nice, that's a nice case and the red should be forgiving for that case.
 

ben_ullman

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Ben, 9800ns is an M. Over 10240ns is an N.

Should be nice, that's a nice case and the red should be forgiving for that case.
sorry I spoke wrong. I was looking at my dads 4 grain 98mm in burnsim, thats 9800Ns.

That N3882 is 11,025Ns. Thats one kicking motor!! Super Polish Rojo, 830Max Psi 180-240 initial-max KN!!!

Ben
 
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