Yes, good point. For many layups, about 20” Hg (9.8 psi) of vacuum is sufficient to get a low resin fraction and to get trapped air out of the layup, and reducing pressure more could risk unwanted compression of core materials.I don’t want the point about a negative pressure chamber to be lost. The chamber will not mask a leak. Having a leak free clamp insures a uniform 14.7 across the entire part.
_IF_ the ply orientations of the tri-axial and/or quad axial stitched cloth meets your requirements, and _IF_ you're vacuum bagging everything, then these materials can be extremely useful. But if you're NOT vacuum bagging (and I don't recall your particular project plan) then these cloths will be EXTREMELY heavy, as they have a LOT of interstitial space in them due to the non-woven quality of the multiple plies. They will retain a LOT of epoxy, without bagging.
If you are bagging, then you're good to go (as long as you bag correctly, which many people don't - they think that holding a vacuum, even if it's leaky, is all that's needed. If you have a leak in the bag, then you're merely ensuring that you will draw air through your layup as it cures).
A presenter at an EAA composite workshop today kept mentioning Rock West (www.rockwestcomposites.com)
No affiliation, but I’m also looking to buy some mold making materials, strand mat fiberglass, carbon fiber fabric and epoxy for resin infusion.
Thanks for the great info and links in this thread. The timing is perfect
Side question: do you use different epoxy for engine cowlings due to thermal stresses?
FibreGlast Developments is your one stop shop for mold materials, from resins, glass, gelcoats, tools, name it. Literally the Aircraft Spruce/Pep Boys of mold stuff. If they don't got it, you don't want it!I’m also looking to buy some mold making materials, strand mat fiberglass, carbon fiber fabric and epoxy for resin infusion.