I used (3) 4-40 on my Intimidator 5. With a 4 inch airframe you could probably use 2-56 if you wanted. According to Missileworks it takes 35 lbs of force to shear a 4-40 and 25 lbs to shear a 2-56 nylon screw.

What are the weights of the components you are restraining? On my 2.5" diameter L3 rocket I had to step it up to 6-32 shear pins to keep the nose from deploying when I separated the rocket. I'd start with 3 4-40's and then do some ground testing.

I considered my successful when I could shear the pins and get the shock cord to deploy 85%-90% length.

Edward

thanks

Mike,

I listed my shear pins on my Intimidator on an earlier response. Two on the fore and aft, 4-40's, worked flawlessly.

My Raven data demonstrated separation at apogee and main deployment went as planned.

The Intimidator has big fins and drag. I worried more about premature separation of the aft at speed. I plan on using the same set up again for my next launch that will hit mach on my Intimidator (KMAG).

We'll see how it works...

I ordered some from Missile Works. Will be here in a few
days.

Thanks.

My rule of thumb - 29mm, little pieces of plastic; 38mm and 54mm 2-56 screws. 3", 4" 4-40 screws. Anything about that, break out the 6-32 screws. Bigger than 6", 10-24... always nylon of course.

Miek, For what it is worth, you should be able to get 4-40 nylon screws at a good Ace hardware store. If you need smaller, I can get 2-56 at the screw supply here in Fort Collins. Let me know and I can get some for you, we can meet up and exchange them. I know it is not cost effective, but it does save time.