Vacuum Bagging Pump

[JohnC]

I have a 5 CFM vacuum pump that is the kind used by A/C mechanics. I was wondering if it is suitable for bagging my transom. I have no experience with vacuum bagging but I am considering bagging my transom. Is this pump suitable? Is there anything else that I need to look out for? Thanks!

[FLexpat]

I use a rotary vane type 5cfm pump that gets ~28" Hg vacuum - it works fine as long as I seal everything. Be sure to use a trap to prevent resin from getting sucked into it though - I almost lost a pump that way.

[specproj]

Oil sealed vacuum pumps , like those used to work on AC systems, are meant to flow very little air through them. Flow lots of air and you will lose oil from the crankcase and contaminate your shop and project. Unless you are infusing core and laminates, just the transom core, much less vacuum is appropriate.

Rotary vane vacuum pumps run without oil, and can flow lots of air through them without problems. 10"-18" Hg is usual vacuum for bagging core, and a simple air bleed valve in the vacuum line will reduce the pump's vacuum to the correct level.

Never use a 'shop vac' for bagging as the vac motor is cooled by the air the vac inhales. Reduce the airflow and the motor heats up . Run a shop vac in the dark sometime and check the motor brushes for sparks, then imagine flowing flammable resin fumes past the sparks.

WEST sells a simple/cheap vacuum pump that runs off compressed air, about 6CFM at 80 psi required

[FLexpat]

Something like this:
http://www.ebay.com/itm/GAST-1-3HP-R...3D130835272543

Edit: FWIW I have seen a few of the Gast 0523 models (5cfm) used for as low as $100 - I think a replacement vane set is $40-60 and that is easy to do - they run forever if not abused