New project... Cluster motor mount fillings...

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Well-Known Member
Jan 26, 2009
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Got bored so i pulled out a buncha cardboard tubes, and planned on making a small 24mm rocket... Well, one thing led to another, and now i have 4 mounts drying for a cluster...

First question: when i mocked up the mounts they fit really tightly in the tube, and perfectly, but there are spaces inbetween the mounts... is it ok if i leave these like this, or should i fill it with some tissue paper and glue mixed together...

You should fill the spaces with either glue/tissue or expanding foam to ensure that your ejection pressure goes forward to deploy your recovery system instead of blowing back out the aft end, leaving the nose cone attached.
That wouldn't be good.
An alternative to glue soaked tissue or expanding foam is to use polyurethane glue like Gorilla Glue.

See my Semroc Goliath review at EMRR for a close-up of using Gorilla Glue.

A little goes a long way. It's pretty much the same thing as 2-part expanding foam except that you do not have to mix it with anything & it doesn't expand as much or as fast as foam. It is just as hard (as in bulletproof). Put a little where you want to fill a gap & leave it alone for 4-6 hours preferably in a warm, humid area.

You can pick up poly glues at any home improvement store. A small bottle isn't cheap (~$6) but it lasts a loooong time.