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tstone

tstone

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I am working on my Lev 3 design & have hit another snag. Simulations show ground hit speed of
over 100 FPS which is way high. With a 96" chute CD of 2.2 on a 40 LB rocket it should be more like
22 FPS or so. Changing chute diameter to 168" in Open rocket has little effect on descent speed.
Anyone got a clue? Open Roc file attached.

View attachment 200% Level 3 EZI 65.ork
 
Double click your 96" chute and set open to "specified altitude"...

14fps then ;-)

Edit: BTW, this may just be your "rough" design...but some of the dimensions seem wonky. The motor tube isn't 2.95" ID and thus you have to filter "all motors" to pick one. And .25" thick G10? I haven't built an 8" diameter yet, but that sounds really thick to me. Not sure about .500" ply fins...tough for sure, but seems like .375" would fit scale better.

Please forgive...not trying to nit pick...just a design geek who really enjoys examining and understanding :grin:
 
Last edited:
jpummil said:
Double click your 96" chute and set open to "specified altitude"...

14fps then ;-)

Edit: BTW, this may just be your "rough" design...but some of the dimensions seem wonky. The motor tube isn't 2.95" ID and thus you have to filter "all motors" to pick one. And .25" thick G10? I haven't built an 8" diameter yet, but that sounds really thick to me. Not sure about .500" ply fins...tough for sure, but seems like .375" would fit scale better.

Please forgive...not trying to nit pick...just a design geek who really enjoys examining and understanding :grin:
Click to expand...

Well that worked just fine thanks for the tip. Yes it is rough I just started it yesterday, got a ways to go. As for your advice
on the fins, thanks thats' why I post here I respect peoples' advice. I like to go overkill on the fins because I have busted
so many of them. I'm going to glass with 6-8 OZ cloth so I might go thinner. WHOOPS yes motor tube I.D. set now to 75MM.

View attachment 200% Level 3 EZI 65.ork
 
Always glad to help where I can. I find it really fun to look at all the cool ideas people have in their designs...almost like building without the actual parts :-D

Lookin' GOOD! Keep us posted. Will you be at AIRFest BTW?
 

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