Vacuum bagging

[abdiver]

I would like to vacuum bag in a repair on a fiberglass boat I just received and would like some impute. I have read the article on vacuum bagging in the WB book on repairs, so have a general idea of the process. One thing that was not clear is what is used for the "header" that goes into the envelope to draw the air out.
Thanks for any suggestions,
Tom

[Bruce Hooke]

I have used a simple piece of plastic tubing run to somewhere near the center of the "bag," but I was working over a form that was inside the bag (this is typical for small woodworking projects, but not on boats) so there was less need to make sure that air was being drawn in from all areas because the form pretty much assured that. I did use mosquito netting on top of a sheet of plastic as a breather layer to allow air to flow in from different parts of the bag.

At the WoodenBoat show last weekend I went to a vacuum bagging demo and what was recommended there was a piece of 3/4" diameter or so PVC pipe with holes drilled on all sides EXCEPT the side that faces the epoxy. At the demo he said used either "proper" breather fabric OR, to save money, bubble wrap (the kind with small bubbles) with the bubbles towards the epoxy. The advantage of both breather fabric and bubble wrap versus just a sheet of plastic is that they both provide a space for the epoxy to go that is NOT in a thin layer all over your work, which can make the cleanup a lot more work.

[JimConlin]

I just run the (1/2" ID vinyl)tube from the pump into the bag, most often at the edge, where there's a seam anyway. Lots of ugly sealant tape sometimes. I leave a doubled strip of bleeder material(polyester blanket) from the hose to the big panel of breather which is over the part. I prefer not to insert the hose in top of the part because i fear that the pressure on the part might be uneven.

[JimJ]

I used a plastic 1/2 inch through the hull fitting to connect the vacuum hose to the layup.

http://www.bla.com.au/eastmarine/product_group.cfm?id=1546&s=3

To connect the 1/4 plastic hose to the through the hull fitting, I taped a 1/8 gas thread in the inside end of the fitting and screwed in a 1/8 Brass Hose Barb

http://www.conexmetals.com/brass_hose_barbs_nipples/brass_hose_barbs_nipples/brass_hose_barbs_nipples.htm

Th insert the through the hull fitting in the plastic vacuum bagging, I pit two layers of sticky tape on the plastic and cut a round hole large to take the hull fitting. I inserted it from the inside nefore fitting the sealing the plastic bag, tightned the nut and then contected the plastic vacuum hose to the brass hose barb.

I used peal ply with polyester wadding to alloe even vacuum.