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Basics of "Zipperless" Construction?

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mjslive2fly

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Newbie here so forgive the ignorance. What makes a design "zipperless" and how is this achieved in practice?
 

Pantherjon

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Whoever maintains that site is a genius!!! :D

Ben
Oh, jeeze, now you're gonna make Kevin's head swell so much he won't make it through the doors!:roll:

I will agree though, it is a very valuable source of great information!..Oh, man, I am doing it too!:roll: :p
 

MarkII

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All hail the great rocket guru of the heartland! Or something like that... ;)

(Ben, are you discovering that you have to do a lot of back-slapping and glad-handing to get an EX section on TRF? This experience could be the inspiration for a future career on K Street! :D )

OK, back to the topic at hand...

Could rearward ejection (of the motor mount, as in the #2127 Sizzler) be regarded as a type of zipperless construction? What about a rear-ejecting parachute design, like the Gemini DC?

MarkII
 

Johnny1Eye

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The design in that link, is a bulkhead with a few holes in it, really enough to not have to use any type of wadding/chute protector?
 

troj

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Oh, jeeze, now you're gonna make Kevin's head swell so much he won't make it through the doors!:roll:
Worry not, Jon -- I'm married. No chance of an inflated ego.

Plus, you haven't seen the rocketry crowd I hang around with, both locally, and nationally. Try to get an inflated ego with that crowd, and they'll smack ya back into line in no time!

-Kevin
 

troj

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The design in that link, is a bulkhead with a few holes in it, really enough to not have to use any type of wadding/chute protector?
I'd still use a protector of some sort.

Something else to consider on the "zipperless" design, when using motor ejection... The ejection charge pushes the parachute deeper into the bay, increasing the chances of it getting wedged in there (voice of experience on this one)

So, make sure the parachute slides easily in the tube, or you'll have problems.

-Kevin
 

kelltym88

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The design in that link, is a bulkhead with a few holes in it, really enough to not have to use any type of wadding/chute protector?
I have built several rockets with bulk heads similar to that one, BUT, I always throw in some dog barf, just in case.
 

Sailorbill

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My grandson and I built his Endeavour "Zipperless" but we didn't use a bulkhead we just used a centering ring and a U-bolt. The recovery harness consisted of a short length of tubular kevlar, a chute protector, a small drogue to ensure the main came out, tubular nylon with the main attached at the mid point.
I have attached a couple of pictures showing how we did it.

Zipperproof Design 002.jpg


Steven 002f.jpg
 

n5wd

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The design in that link, is a bulkhead with a few holes in it, really enough to not have to use any type of wadding/chute protector?
Yes, and no. If you design the baffle so that there is no way for the hot particulate matter to gat out of the top end of the baffle, then no, you don't need any type of wadding / chute protector. I've done three different rockets with the method described in this thread: http://www.rocketryforum.com/showthread.php?t=1901&highlight=baffle and have not had any holes burned in my chutes - no wadding, no dog barf, no nomex. My fourth is a 4" Samurai under construction, and I have no worries it'll also protect the laundry just as well. My design uses an "S" curve for the gas, which doesn't mind going around corners twice to get out of the top. Particulate matter doesn't make U turns too well.

If, on the other hand, you have a path for the particulate matter (the hot, burning bits of BP that are expelled by the ejection charge) to escape, then yes, you need the wadding because all you did was slow the gas and burning matter down just a smidgen.

Keven's concerns are valid - if you're using motor ejection (my Samurai will have motor ejection as the backup - primary ejection will be the altimeters) then the chute does get pushed into the upper tube. But, if you don't make it too large, and don't have anything that'll hang it up after the two airframe parts become separated, you shouldn't have a problem. After about 25 flights using this design on my three rockts (all 3" in dia), haven't had one hang up.
 
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Neutron95

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I built my 2" L1 rocket with zipperless construction and a baffle. On the first attempt, the parachute stuck in the upper section and ripped out the top baffle plate. That evening, I reinforced the plate with fiberglass and clanged the location of the parachute closer to the baffle. When I packed the parachute, I wrapped more shock cord around it, and I certified the next day. I think that zipperless is fine for most applications, but not usually in a minimum diameter rocket. (My cert rocket is a 54mm minimum diameter rocket)
 

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