I’m own a small composite fabrication shop that manufactures parts for the radio controlled and UAV industries. I really like doing hollow structures via pressure bladders. I also do hollow structures that get done in one shot via VIM. All my work pops out of the mold with paint or clear-coat.
Here are some photos and videos of my work.
Very nice work! Good to hear we have an expert on bladder molding/hollow structures! I hope you don’t mind me asking you questions.
Thanks for the compliment. Questions are always welcome. 
I can’t see the first post of this thread…?? canyons post is the first one on my screen… 
Wyo Welcome!
It’s up now. I couldn’t see if for awhile either.
Thanks for the welcome!
Hi wyowindworks, I was hoping you might shed a little light on the construction of the moulds you use in your videos.
I have made simple moulds with graphite powder and epoxy before which have worked well but they have been of a standard open back type. Looking at yours it looks like you have built a box damn round your parting flange and plug which results in a boxed in, solid looking mould. I understand there would be considerable forces involved with the bladder method you use, what intrigues me is the lightness of your moulds are they all carbon and filled with a heat stable foam or some other media which is then glassed over? They look very well thought out and a world away from the type of moulds I normaly use.
Inflation bladder molds need to be very rigid. Stability is also a big concern for multi-piece molds that produce painted in the mold parts. Polyester and vinyl ester resins can’t be found my shop. They shrink to much to create stable molds that make pretty seams.
I use many different mold construction methods. All my production molds utilize some kind of sandwich construction to create stability and stiffness. If the mold flanges aren’t stiff enough they will bow between the clamping locations during bladder inflation. Often I will put down a surface coat, then resin/glass or resin/carbon, then epoxy mixed with playground sand, then more resin and fiber. If I need the mold to be lighter I will use a tooling compound in place of the epoxy/sand or use epoxy and Poraver. Another method that I use is surface coat, then an epoxy/sand slurry, then I press square or rectangular steel tube into the slurry around the perimeter of the mold. The sand sinks in the resin and the excess resin floats to the top. I then add some fabric to this resin, then more epoxy sand (really dry) then more fabric/resin. I will often cast epoxy sand right against the surface coat so I don’t risk getting fabric print-thru in the mold surface.