Is Vacuum bagging suited to GRP/ polyester resin layups ?

Hi,

I am interested to know if it is possible/ practical to vauum bag a GRP polyester resin laminate.

My problem is that my laminators are sometimes using too much resin leading to too thick/heavy a laminate. I would probably just vacuum the deck /coachroof to assist stability and performance.

The boats are 33ft sports/ fishing boats and are presently built at low cost- except for the high resin to fibre ratio of course!! The laminates are all single skinned. Perhaps if it is possible I could core the deck/coachroof- BUT then may have to charge more for the boats. They sell at present because the prices are very competitive.

Hope some one can advise.

 

Vacuum Bagging

It's definitely possible to vacuum bag polyester/glass laminates, but there are a few things that you must look into to determine if it's practical. First of all, to successfully wet bag a laminate you need to buy consumable products: perf release film, peel ply, breather, vacuum bags, mastic tape, and a vac pump just to name a few. Some consumables can be reuseable such as a silicon or urethane vacuum bag, or you can go for low cost and use a cheap poly bag (not recommended for vacuum infusion as your vacuum levels cannot be optimized with these bags).

When you wet vacuum bag, you can save on materials (resin mostly), but you may have to redesign the laminates. When you compress fiberglass under vacuum, you can loose up to 30% of your thickness, which will greatly decrease your stiffness. Coring the laminate may be the only way to go.

 

You can Bag about anything ….but in your case the resin input/cost will be about the same as before the difference being the …Finished part … Because now with the bagging the extra resin normally in the boat Parts will now be in the breather Which is going in the waste container..

Your cost will rise with the vacuum bagging equipment/materials/labor also the resin chemistry will have to be adjusted for the needed extended Gel time.

Which comes to the infusion, But beware there are a lot of ******** systems out there. What ever you do start small...

 

No

:!: NO

 

It would be interesting to know what weight/lay up you are using on these boats,i would have thought on a boat of this size you would have had to use a core material ie balsa wood etc on the decks and coach roof and any other area that will be walked on to stiffen them up rather than using solid glass this would also make them lighter and the cost would almost definetly come down or at least be the same.

 

is your crew wetting out buy hand or using a chopper gun with the wheel shut off
and best q for you is how fast is your crew???
it can be done but you better have a dam good crew to do it on a 33 with ploy your bag better be ready to go and you should bulk up your blanket
meaning your peel-ply, relese flim,and brether all need to be sprayed with 44 spray adhesive to form a blanket and should be cut to size you can use bubble wrap to cut down on cost and with ploy use only bag film ploy resin will start to break down ploy film and your best off using the green film its a little more ply-able the yellow film is better use by experince do to it will not strech at all and the bag has to be ajusted as it is goning under vac to stop bridging on inside corners when coreing i would only use close cell foam and one more question whats your lam seg. if lots of chop or mat not worth it for hull of that size this is what i recemend
gel-coat 3/4 chop,1x1oz mat,2x1808,20mm h80 close cell core 2x1808 then peel ply even if you dont bag peel ply you will find it the best friend you can get
it will keep your hull clean while building the boat i was building the hunt 33 using the lam and 4 of use colud lay up the hull in 4 days start to finish and with no bag hull and deck only for the core we baged ended up 1200 lbs liter than expected defanetly bag all bulk heads if using foam and its a great place for your crew to learn baging and get the feel for how much resin to apply if you soak your breather you will stop the flow of air to the pump and it will not de-bulk leaving puddles of resin
hope this helped

 

Why not use Resin infusion?

For a small investment, you can build repeatable quality into your product by changing your process to Resin infusion, RI.

why vac bag such a big thing as your limited by time. I would infuse it from the start. Therefore your 20% Vf could be say easily be 60% depending upon your layup.

Roughly the only cost is about £2.50/$4.00 per sq meter. Tigervac is a good supplier of such RI materials. with the saving on resin cost you make, this shall fund your added materials. However you will need to buy a good vacuum pump, but thats a small one off cost.

plus your working environment will be so much more plesent.

Hope this helps

Shaun