Body tube diameter to nose cone shoulder length ratio

[OC_Rocket_Man]

Is there any rule of thumb for a BT diameter to nose cone shoulder length ratio?

I have a 4" parabolic nose cone that has a 5.25" shoulder. I bought the nose cone from Madcow because I saw it there and it looked cool (and I saw Nytriders build thread the day after I saw the nose cone) don't have any real plans as of yet.

To me the shoulder seems excessively long. If anything I tend to see people chopping shoulders and attachment points and adding bulkheads into nose cones.

My PML 4" or 3.9" whatever nose cone shoulder is 2.25".

If it makes any difference the Madcow/Rocketry Warehouse NC is hand laid fiberglass.

 

[Nytrunner]

No Nytrider's here that I know of.

For couplers and interstages, it's optimal to have just a tad over one diameter of shoulder to reduce bending at the joint and prevent damage to the tubes. (in rigid airframe's like fiberglass, you can get away with a bit under I diameter)
That's for unpinned couplers. Pinned shoulders/couplers can have less length because the pins take bending load instead of relying on the tube fit. (example, my 5.5" diameter Ebay will have 6" internal length on the free sliding side, and only 4" on the pinned side)

For nosecones, the bending stress is a lot less than a mid body coupler (try snapping a match in half, then try only snapping it below the head). You could chop it to at least 4" (your body diameter) and be fine, probably lower (especially if you're going to use shear pins). The long shoulder is likely a result of the layup process.

 

[OC_Rocket_Man]

No Nytrider's here that I know of.

For couplers and interstages, it's optimal to have just a tad over one diameter of shoulder to reduce bending at the joint and prevent damage to the tubes. (in rigid airframe's like fiberglass, you can get away with a bit under I diameter)
That's for unpinned couplers. Pinned shoulders/couplers can have less length because the pins take bending load instead of relying on the tube fit. (example, my 5.5" diameter Ebay will have 6" internal length on the free sliding side, and only 4" on the pinned side)

For nosecones, the bending stress is a lot less than a mid body coupler (try snapping a match in half, then try only snapping it below the head). You could chop it to at least 4" (your body diameter) and be fine, probably lower (especially if you're going to use shear pins). The long shoulder is likely a result of the layup process.

Sorry for the name mishap

It's probably something I'm overthinking so I search and then ask questions for clarification. Since it's a parabolic nose cone it's also much shorter than a Ogive which even furthers your match head comparison. I was just noticing the plastic PML is so short in comparison. Then I thought the fiberglass is heavier so maybe that's it. But then lots of people bury lead in their plastic nose cones. So here I am.