Vacuum bag repair

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DavidGrieves

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West Cumbria, Cumbria
www.wsandba.co.uk
Hi All

I need to do a repair and would like to vacuum bag it to push the glass/tape into the corners and over the edges. Iv'e found a supplier for the equipment but the pump is quite expensive to buy for one job. Has anybody used an alternative pump or hand pump to create a vacuum. Would an old hoover be up to it? What about a dinghy foot pump on the deflate side?

Any sugestions welcome....

Cheers

Dave
 
When I last watched a liferaft being packed, they used an ordinary vacuum cleaner to extract the air from the vac pack bag. I guess the secret is not to run the cleaner for too long, as they usually rely on airflow to cool the motor.
 
DavidGrieves said:
Hi All

I need to do a repair and would like to vacuum bag it to push the glass/tape into the corners and over the edges. Iv'e found a supplier for the equipment but the pump is quite expensive to buy for one job. Has anybody used an alternative pump or hand pump to create a vacuum. Would an old hoover be up to it? What about a dinghy foot pump on the deflate side?

Any sugestions welcome....

Cheers

Dave
Click to expand...

The problem with manual pumps is that you need to keep the pump running until the epoxy has hardened.
For the same reason I think a hoover will burn before you are finnished.

I have read that some have used a compressor from a fridge/freezer with good results.

Another option is a ejector based on the venturi effect - You need a compressor for this to work.

You have read this http://www.westsystem.com/ss/assets/HowTo-Publications/Vacuum-Bagging-Techniques.pdf
 
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I used 4-5 similar ones at end of last season as Galicia is about 3 times wetter than Manchester in winter. All clothes and bedding were squashed to within an inch of their lives with a small hand vac. I think that the dinghy pump would have managed to get a tad more air out.

Almost 14.7 lbs on every square inch so you can work out the force squashing your piece of GRP. I imagine it would be a good way to get rid of trapped air.

I wonder about the durability of the bags with sharp edges and resin. One of our bags didn't seal well so we put it inside a 2nd one and it still got all the air out. I thought the inner one might crease and seal air inside but that didin't happen and it crushed down as well as the other bags.

The resin might "evaporate" (boil off) to some extent before it cures and you might need to keep pumping. The bags we used had decent seals and it would be possible to pump out and leave for a while before removing the outer cap and pumping out again.
 
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A vacuum cleaner is not really suitable because as said it needs airflow for cooling.I have one similar to this one and it works great.I've done some heavy vacuum bagging with it.Maybe you can buy a used one.They can be left running for days.There are quite a lot from the States on sale and very cheaply too.http://www.ebay.co.uk/itm/Vacuum-pu...quipment_Lab_Equipment_ET&hash=item2a28ecde5f
I'd lend you mine but I'm in Portugal.
 
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I've done a fair bit of vacuum bagging and I'd happily lend you mine except the pump is broken. However as someone said it depends how long it would take for the epoxy to set. Our panels were left for 24hrs before the bags were opened. the pump would be left on constantly and air bled in to change the pressure. However a lot of guys used an old fridge compressor pump. blue tac is brilliant for sealing where the vac tube enters the bag and sellotape over any little hisses also. Simply pulling one vacuum wont work. NIK
 
You might consider one of those car tyre air compressors that run on 12v battery. If you can connect to the air inlet at the pump you could use that. Need a charger on the battery of course. don't forget some sort of permeable cloth or similar to allow the vacuum to spread across the job not just seal up the exit hole. good luck olewill
 
William_H said:
You might consider one of those car tyre air compressors that run on 12v battery. If you can connect to the air inlet at the pump you could use that. Need a charger on the battery of course. don't forget some sort of permeable cloth or similar to allow the vacuum to spread across the job not just seal up the exit hole. good luck olewill
Click to expand...

If you mean the home type these pumps are generally rated for short bursts of activity, so not really an option. Check the documentation before you try with a car tyre compressor.

Regards,
David H.
 
water driven vacuum pumps

a cheap water one would be

http://www.camlab.co.uk/vacuum-pump-p14062.aspx

I have one that I use for occasional use for veneering.In combination with gentle heat to reducethe glue setting time, careful with heat as boiling points of glues can reduce under vacuum and if the glue bubbles while setting,then reduces strength.Wasteful of water but say a glue set time of 1hr means the water has to run for an hr . It can be helpful If you can afford to set up an on off low pressure switch to the water source,and a non return valve ,but for occasional use ...

there are several different types, you can get an air driven one

http://www.coleparmer.co.uk/1/1/34882-venturi-vacuum-pump-1-2-cfm-28-0.html


others diff' cfm

http://www.coleparmer.co.uk/1/3/water-driven-venturi-vacuum-pump
 
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