L3 cert project, coupler length

[LWade]

Hello,

I am designing a 7.5″ (PR G12) fiberglass rocket for my level 3 certification and had questions regarding the length of the couplers. I have read about L3 rockets failing in the coupler area and have seen recommendations of up to 2X the caliber of the rocket. How much overlap should there be? I am designing the rocket to use motors up to M3000 (75mm).

Thanks for you help!

Lwade

[Christopher Dreher]

Most people put at least 1 caliber of coupler sticking into each end the body tube, so for a 7.5″ diameter rocket that would be a coupler with a total length of 15″. The PR fiberglass tubing is very strong and 15″ would be adequate IMO. Definitely run your ideas past your L3CC/TAP though.

[LWade]

cdreher

Thanks for the information. I’m a Tripoli member so I will run my ideas past a TAP member at the next launch. Thanks again!

[James Russell]

have you contacted a TAP yet? Mark L, Art H and myself are the most active of TAPs here but there still are a couple of others in the area. feel free to shot me an email at jamesr2 at gmail and I can make sure that you have our info for questions and review.

[LWade]

James,

Thanks for responding, I just asked Joe H who the TAPs were the other day. I will send you an email soon, will you be at the December launch?

I have many other questions, but will create a separate post.

Thanks,
Lwade

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