Best Way to Down-size a 4" Nosecone Shoulder

I mentor a Tribal College Team. Every year the Wisconsin Space Grant Consortium sponsers the First Nations Launch Competition. And every year the goals are different. This year we need to launch two eggs to 2389' and get them back unscrambled & video the eggs during the entire ride.

To provide light for video we want to create a upper payload bay made out of 4" clear acrylic. McMaster-Carr carries it. It has a 4" OD and a 3.75" ID. The nosecone would be on top of the acrylic with a bulkhead on the bottom.

I'm looking for a way to modify a standard 4" plastic LOC nosecone to fit into the acrylic. LOC 4" body tube is 4" OD and 3.9" ID. So the shoulder of the nosecone is ~3.9". I don't think there is enough material on the shoulder to bring it down to 3.75".

I thought about a 4" balsa NC but I can't find any company that makes them. And finding a 4x4 block of balsa is difficult. So I thoight about injecting foam into a plastic nosecone and once it has set up start to sand down the shoulder until I get to 3.75". If I go through the plastic I can san a little further and then use fiberglass cloth & epoxy to build it up.

Any other ideas? We need to place our order for components next week.

Cut off the shoulder completely, jam a coupler (home-made if necessary) into the nose that fits the acrylic? Then fill the gap between the shoulder and the nose.

neil_w said:

Cut off the shoulder completely, jam a coupler (home-made if necessary) into the nose that fits the acrylic? Then fill the gap between the shoulder and the nose.

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+1

Or cut the bottom of the shoulder off to see how much thickness you have to work with. If you can sand it down to fit without blowing though a thin spot, you could laminate something to the inner circumference to stiffen it. If the cone is going to be mechanically secured to the top of the payload bay you might not need the shoulder to be very rigid.

Cut the shoulder off... Insert a suitably large body tube segment (say 2" or 3" OD) inside, use two different diameter CRS to center it (dont' forget to pin it and epoxy it). Then use two more CRS to center a tube coupler that fits the clear segment.

Can you open up the clear acrylic on a lathe to fit the NC??

David Schwantz said:

Can you open up the clear acrylic on a lathe to fit the NC??

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+1 to this method, open up the ID to accept the shoulder if possible.

If you thin it down to much, you're really going to compromise the strength though.

Best of both worlds. Turn the inside diameter down and build up the inside of the nosecone shoulder with glass or plastic so you have enough diameter to turn the nosecone shoulder down.