Reinforcing the Pointy End

[Hospital_Rocket]

I recently took up using thin CA to beef up the ends of tubes. I tend to go back about an inch .

Ok, when I do this, Things no longer fit. So do you sand down the CA and depend on what soaked in or do you sand down the mating part. In particular, I am interested in what to do at the NC end.

For a MMT I expect sanding is the only way.

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[rstaff3]

I usually sand the swollen tube end down.

 

[DynaSoar]

Originally posted by Hospital_Rocket
I recently took up using thin CA to beef up the ends of tubes. I tend to go back about an inch .

Ok, when I do this, Things no longer fit. So do you sand down the CA and depend on what soaked in or do you sand down the mating part. In particular, I am interested in what to do at the NC end.

I did that and ended up sanding the nose. That was kindd of iffy because the tube wasn't even -- it was out of round. The nose fit differently according to how it was turned. Then I started getting urethane noses and didn't want to mess them up.

Now I only do the very edge of the tube. That's where a zip starts. For protection farther back I've taken to wrapping the tube with vinyl, and in a couple cases, a strip of styrene. If I was to get real fancy, I'd wrap the inside so the smaller diameter would be even and I could shape the nose for it reliably without ending up with poor "grip".

 

[rstaff3]

Getting to root causes, I've found the main damage to the front end is either the NC hitting the tube as it recoils or zippering. The latter can be a true zipper or a deformation in the tube. These can be addressed by improving the recovery harness. Add a long length of Kevlar twine at the airframe end and add a couple of layers of thick cloth based tape where the cord will contact the BT.

The reason I sand the swollen area is just for the reason DynoSoar stated. The opening is just so slightly out of round in its ID and often is not uniform along its length. You need to sand the cone to get it by the lip, but as it passes the lip its a skosh too small.

As for the MMT end, don't reinforce it until the MMT is in. If the MMT is flush with the rear, you don't need reinforcement.

This all applied only to wood NCs anyway, I'd never sand a resin or plastic cone, etc.