If you do that, the Firefox carbon cloth is real handy. Whatever diameter
of tube you snag, you can easily make a good liner for it.
I made a lot of small motors (thru L'ish) with fiberglass motor tubes. I
was lucky enough to find lots of high quality tubes at good prices. Of
course that was twenty years ago. For forward bulkheads I cut out circles
from fiberglass sheets. All the way to 1/8in thick stuff I used for 98mm
motors. I found a nice simple way to cut the perfect size circles. I mount
a roughly cut piece to my dremel. I then spin it against a sanding disk. I
keep checking with a piece of motor tube until it's a perfect fit. I used
Aerotech nozzles (yeah cheating, but making your own greatly complicates
things). To hold the nozzles and bulkheads I did one of two things. 1. With
the thicker tubes I cut a snap ring groove forward and aft. the bulkhead
and nozzle mounted "under" the grooves. I then put in the snap rings and
epoxied them. Yes, I know, cutting fiberglass will weaken it. But I never
had any unexpected failures from that. I did a small experiment with some
38mm motors. I kept decreasing the nozzle throat until the forward snap
ring groove failed. My rough calculations showed it was near 1,000psi
chamber pressure when it failed. But for normal motors, it worked just
fine. If the fiberglass was too thin for a snap ring groove, I put in four
small screws. The epoxy just needs something to grab onto.
Let me know if you have any questions. Good flying!
On Sat, Feb 25, 2023 at 8:42 PM James Fackert <jimfackert@xxxxxxxxx> wrote:
If you can catch a ride on a high volume product in another industry you
can save money.
Fiberglass electrical conduit in many sizes and several weights,. And
fiberglass pipe for use as underground gasoline storage tank connections
are a couple of sources.
If you can pick up unusable cutoffs from a friendly installer or
electrician, woopie!