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Parachute attachment

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Spurkey

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In MPR & HPR kits, why is the parachute attached to the shock cord up to 12" back from the nose cone instead of at the end of the cord? I can understand not attaching the chute directly to the nose cone itself since the nose cone can break off or otherwise come loose from the cord (proven with several of my Estes kits :mad:), but wouldn't you want the chute at the end of the cord to allow the rocket to slow down as much as possible before the chute opens? Wouldn't it increase the chance of tangling as well since when the chute opens the nose cone would then swing down on the longer leash potentially hitting the chute? Inquiring minds and all that... :)

For example of what I'm talking about see page 5 of these instructions:
http://www.cosmodromerocketry.com/Instructions/NikeSmoke/instructions_NS.pdf
 

Handeman

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I can't say why you should do that, but I only make sure the distance from the BT to the parachute attachment point is longer then the length of the parachute and shroud lines.

An alternative to attaching the chute 12" down, is to attach the nose cone 12" down the shock cord and put the parachute on the end.
 

novikov

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...

An alternative to attaching the chute 12" down, is to attach the nose cone 12" down the shock cord and put the parachute on the end.
This is what trie and have stuck with after getting some harder than anticipated landings due to chutes opening correctly but being further and further restricted because the rocket was spinning in circles underneath the chute. Since i started this way on my model level stuff I haven't had any issues with that. My one hp bird isn't done that way but it has significantly less potential to do that as well (though I would like to put a swivel in place on the chute just as a preventative measure).
 

Spurkey

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An alternative to attaching the chute 12" down, is to attach the nose cone 12" down the shock cord and put the parachute on the end.
*hm* I like that idea, keeps the nose cone a bit further away from the chute but still keeps a good length for the chute to deploy.

As for the swivel, how do you go about picking one with the right load? I've seen ones from LOC with a 1000lb. limit, that seems a bit much for a 3lb. rocket launched on an H/I motor.
 

Handeman

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The difference in weight between the lightest and heaviest swivels isn't that much. I look for the ball bearing swivels. They cost a lot more, but the will swivel when the other get hung up.
 

MarkII

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These are great swivels:

http://www.cabelas.com/cabelas/en/t...&parentType=index&indexId=cat20293&hasJS=true

When you need an extra strong swivel, one of these will do the job nicely:

http://www.cabelas.com/cabelas/en/t...&rid=&parentType=&indexId=cat20293&hasJS=true

For all of their strength, they are quite compact and light in weight. See the attached photos. The SPRO ball bearing swivels in the first photo are rated for 300 lbs., and the heavy swivels in the second photo are rated for up to 860 lbs. Neither one is the strongest SPRO swivel of its type. You can get the kinds of swivels that the high power folks use, which will be much stronger, but they will also be much bulkier and weigh considerably more. For really big rockets that have dual deploy recovery systems, you do need the the big heavy duty HPR-type, but for MPR, you really won't need a swivel that is rated to 2500 lbs.

MarkII
 

Spurkey

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ONAWHIM

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It would be nice if advertisements gave the I.D. of the eye opening of the swivels along with the specified rating. But then again these are designed for fishing line and leader.

I went to a sporting goods store and looked at ball bearing swivels but I don't believe I would be able to get my shock cord through.

I recall one online rocketry site that did specify the ID.

For the mid to high folks I would think knowing the ID would be a factor to help them decide when placing an order.

Wm.
 
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