Vacuum gluing question

[ColeyS1]

Few quick questions if I may.

I bought a bagpress 8x4 kit that just plugs into the compressor. The venturi valve obviously works but I was a bit surprised how often the compressor was having to kick in/recharge- every 6 minutes :-? Is that normal? If its been going for a few hours the motor feels rather warm. The noise gets on my nerves, and my workmates also :lol:

Flat stuff I can kind of understand only needing a few hours. Curvy stuff would be good to leave going for much longer. Is there a standard rule for how long something should be left under vacuum ?
If it makes any difference I could look up the compressor specs. Its a upright Clarkes one . From memory it was loads big enough for spraying 18cfm and 150 litre. Ive got the regulator set at 6 bar.

Thanks

Coley

 

[Myfordman]

I presume as you talk of using a compressor, then you have bought a venturi adaptor to create the vacuum.
This type will require a continuous flow of air and so the compressor will run a lot.

For minimal running time/noise you will need to buy a vacuum pump to go with your bag.

 

[Allubo]

Hi, if you use a glue such as titebond iii you may get the curing time down to an hour at 21oC, but it won't be as cheap as PVA or extramite.

Also for a quicker curing time using extramite, you can cover to layup in an electric blanket

 

[GCR]

I also use a Venturi setup from Bagpress. Recently I have used their "non creep" white glue which sets quite quickly -in the summer/warm workshop you should be able to turn off the compressor after an hour.

Initially the constant noise from the compressor got on my nerves but I managed to reduce run time by adopting the following:

Use a large flow venturi to draw as much air out of the bag as quickly as possible. Swap for the smallest venturi (turn off bag via the valve supplied). Run for a few minutes then reduce the air pressure to the venturi which dramatically reduces the amount of air required. The push fit fittings are very easy to change so this does not take long to do. My small compressor now runs for between 25 -30% of the time.

The notes with the Bagpress indicate evacuating the bag then turning the valve off and thats it. I have never managed that happy state, there is always a little leakage from somewhere in my setup.

Bob

 

[ColeyS1]

Some really really useful info there chaps. Many thanks :wink:

I'll keep my eyes peeled for a cheap vacuum pump. The thought of buying that might make me put up with the noise a little more.
That electric blanket idea is superb !!! In the winter its hard enough just getting it warm for gluing , so for vacuuming it will be a huge huge benefit to speed things along.
I'll try turning the regulator down and see if it alters the effectiveness.

Thanks again

Coley

 

[JonnyD]

We had some problems with electric blankets heating up one side of the panel more than the other and causing it to warp. It's best to preheat the inside of the bag with the blanket so you don't get one hot side and one cooler.

Cheers

Jon

 

[ColeyS1]

Jon, thanks for the headsup ;-) what kind of setup do you use for pulling a vacuum ? My only concern ive got is that one time the compressors getting on my nerves and I ruin something by turning it off early. Why does decent stuff always have to cost so ruddy much :-o is it a fairly common thing to be using electric blankets for gluing then ? Cant say ive ever heard it before

 

[JonnyD]

I use a air press vacumm pump which gets left on but its more of a dull drone in the background than the racket fom a compressor. I used to use electric blankets but I have insulated the assembly shop recently and its easy to get up to 20 degrees now so no longer use them.

Cheers

Jon

 

[ColeyS1]

Thanks for the further info jon :wink: best start saving my pennies

Edit: just been looking on the bagpress website and a 0.5 venturi definitely looks like it will help. From what I can see it'll just mean I wont be able to use the full 8×4 bag- at the moment I only unroll what I need anyway so hopefully this might dramatically reduce the compressor noise. I'll give em a ring tomorrow to see how much just the valve would cost

 

[Allubo]

Hi, yeah I agree with the blanket only heating one side of the work, I only use it over curved veneering work so I'm only ever glueing one side of a substrate.

That's a good idea to put the blanket in the bag first.

Alex