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tnjeff

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Well, winter's approaching so I'm thinking about my level 1 rocket for next year. I've attached some pics and I'm hoping to get some feedback on a couple of things that might be a problem.
First, the rail buttons will need to be on standoffs. The "payload" section is a 3.9" tube and the booster is a 3" tube. I was thinking of using well nuts to attach them and hardware store nylon spacers for the standoffs. Any idea if this will be rigid enough?
Second, it is a bit overstable. Not sure how much of a problem this will be. With certain 38mm motors installed, RockSim and OpenRocket show about 3.5 caliber stability. I've made the fins a bit smaller, and that helped a little. I thought there might be something about this design that made it over stable, but it could just be the length and the weight of the nosecone and transition.
Any comments are appreciated. Thanks for looking!
Jeff

38mm_65in34inbooster.jpg
 

Pantherjon

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Well, winter's approaching so I'm thinking about my level 1 rocket for next year. I've attached some pics and I'm hoping to get some feedback on a couple of things that might be a problem.
First, the rail buttons will need to be on standoffs. The "payload" section is a 3.9" tube and the booster is a 3" tube. I was thinking of using well nuts to attach them and hardware store nylon spacers for the standoffs. Any idea if this will be rigid enough?
Should be..At most you are looking at 1/2" standoff's, so they SHOULD work fine, as long as the buttons are well aligned and there is no binding on the launch rail.

Second, it is a bit overstable. Not sure how much of a problem this will be. With certain 38mm motors installed, RockSim and OpenRocket show about 3.5 caliber stability. I've made the fins a bit smaller, and that helped a little. I thought there might be something about this design that made it over stable, but it could just be the length and the weight of the nosecone and transition.
Any comments are appreciated. Thanks for looking!
Jeff
That is preferable over under stable..Most that will tend to happen with an over stable rocket is that it will 'weather vane' into the wind..Making the walk for recovery that much longer if there is any wind above about 10mph..Your over stable issue comes down to a length issue I believe..

It is a pretty good looking design, BTW ;) If you plan on modding it for dual deploy, just keep in mind that your avionics bay will need to go above the transition so your altimeter won't get 'confused' with the turbulent airstream coming from the transition area..

Keep us posted, and keep asking questions! :)
 

tnjeff

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Thanks Pantherjon. I tried a couple of other "normal" 4 inch diameter designs of about the same length last night, and got about the same results on the stability, so I believe you're right about the length.
If you plan on modding it for dual deploy, just keep in mind that your avionics bay will need to go above the transition so your altimeter won't get 'confused' with the turbulent airstream coming from the transition area..
I did not know that. It sure pays to ask questions doesn't it? I had thought about dual deploy but figured on putting the payload bay in the "booster" section. I wonder if there is any way to put it in the transition itself? I was going to use a LOC plastic transition and its supposed to be marked for different sizes of tubes so that you can cut it and put a tube through it. That would make the vent tricky though wouldn't it?
 

tnjeff

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I spent a little time experimenting with mounting rail buttons on standoffs using well nuts as the attachment method. I don't think that's going to get it. I would expect a significant amount of down force at launch and they seemed just a little to flexible. I think standoffs might work if they were backed up with a small hardwood block that was glued/screwed to a centering ring.

But, since the idea is to get my level 1, I think I'm going to shelve this one for awhile. I'm probably going to get a Binder Excel, get my level one, then add an electronics bay and build my dual deploy chops. So many rockets, so little time.
Jeff
 

dixontj93060

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Yes, you would probably need a wood block and t-nut in the BT. Also you might try metal all-thread connectors as standoffs instead nylon and thread the screw all the way through into the t-nut. That should be stable enough.
 

tnjeff

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Also you might try metal all-thread connectors as standoffs instead nylon and thread the screw all the way through into the t-nut. That should be stable enough.
That's a great idea. Thanks.
 
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