vacuum bagging questions

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#1

tried searching, but couldn’t find any help… here are a few questions i had:

  1. generally, how many lines do you install for a medium-sized piece (about 9"x9")? do you guys usually install one vacuum line per side, or is one line just enough (which is what i regularly do)?

  2. after pulling all the air out, how long do you guys let your pump continue to pull? do you shut off immediately? should i lessen the power of the vacuum a few inches after all the air is pulled, and THEN clamp up the line?

  3. i’ve always had problems with this in the past, but when you setup your bags, do you guys do this beforehand or afterhand? for something like a helmet or fender, is it best to line the bag so that it runs alongside the inner curve of the part w/o too much shrinkage?

thanks guys for the help in advanced.

#2

  1. 1 line. You should never need more than one vacuum line. A 9"x9" part is very small. Medium sized part would be like a motor hood and a large size part should be anything above an 8 foot boat.

  2. If you’re vacuum bagging and not infusing, then you can turn the pump off as soon as the pump has reached its max potential. This is assuming that you are able to clamp off the air line and have no leak.

  3. I’m not sure if I understand what you’re asking here. I’ll read it again later.

#3

ah ok.

well just a tip for you guys. i tried adding a light layer of mold release to the inside of the vacuum bag and i was able to reuse the bag 3 times for small parts. the piece seperated from the mold w/o problems and was sturdy and still held a good vacuum for the next few parts. the catch is you have to have enough leftover bag surface area to be able to reseal it again.