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[poser516]

1- Are any of these pumps any good?
http://fiberglasssupply.com/Product_Catalog/Vacuum_Bagging/vacuum_bagging.html
Also found this one: http://www.robinair.com/products/detail.php?id=1039
If you recommend something else, what is it?  I don't want to make a pump, I just want to buy one ready to go that will last a long time.  I checked out that pump starter kit in the "beginners guide" and the guy didn't reccomend me buying it, and sent me to his son's website.  So I'm lost and want to get a good pump but not spend too much money.  I want something reasonable.

2- Are these pumps generally loud?  How loud compared to an air compressor?

3-  On average, if you are making a 3 inch thick board with wood rails, how thick do you make the rail strip that you epoxy on to the board.  1 inch?


Thanks a lot guys.  Tried to read through the forms to find these answers but it was hard.  Couldn't find any specific pump info on those pumps, seems like a lot of you make them.  
Thanks for taking the time to answer my questions.

[Kit Sidwell]

Those pumps look perfect. I don't know about the quality of that brand, but i'd expect them to be worth the money.
Rotary vane pumps are generally the most quiet type, a little bit of noise when sucking down, but when the bag comes up tight they quieten down nicely.
Not loud at all compared to an air compressor.

The thickness of wood on the rail depends on how much you want to wrap the skins around the rail.
Some people have made boards with totally wrapped rails (no perimeter stringers at, all), others use an overkill of wood.
Personally I would shoot for about 3/4" thick rails. This means that the sins will not have to wrap the rails too much, but you will get a fairly light board still.
How much you round the rails off before vaccing the skins on depends on how thick the skins are, how easy it will be to get them to conform round the rail. Generally I just follow the line of the deck roll out onto the rail, maybe a slight touch more curve.
As long as your rails are not super boxy you should have no probs.

Kit

[poser516]

Hey Kit,
thanks for the information.  I appreciate it.

So I just called robinair to find out what an "HG" was, because in the beginners guide somebody says that 7 or 8 HG will be enough to get everything to press together nice and tight.  I asked the guy how many HG the vacuum can pull, and he didnt know what an HG was.  Is and HG the same as a micron?

Also, is 7 or 8 the general consensus for a #2 blank? What about a #1? 

Thanks,
Bobby

[Sparrow]

Hey Bobby,
'Hg' is the chemical symbol for mercury.
So when someone refers to 7Hg they mean the vacuum is pulling 7 inches of mercury on their vac gauge.
I use about 7 or 8 Hg when using .75# core so you could get away with more with a 2# core.
Don't quote me but i think 2# can stand up to 12 -15Hg

[poser516]

thanks sparrow, I appreciate your help.

So is there a relationship between microns and HG?  If the pump I buy has a 20 micron intake and 10 CFM, will pulling 7-10 HG be a problem?

How does one tell?

[Sparrow]

sorry mate, i know nothing about microns etc.

To tell how much vac you are pulling, buy a vacuum gauge from an auto store and connect it to your vac line with a 'T' piece.
You can either use a vacuum switch that cuts off when the system gets to the pressure you want or you can use a release valve (basically a small tap) to release vacuum from the system until your gauge reads 7Hg.

[Kit Sidwell]

They both mean pressure, just different measuring units.

Microns - zero is an absolute vacuum, so those pumps pull down pretty low - they have to if they are to be adequate for resin infusion

Hg - increasing pressure up to approximately 30 Hg which is a full vacuum.

[poser516]

thanks guys.

[lemat]

On 2#, i put -0,7 bars max. My home made régul start pomp (fridge compressor) at -0,3 bars and cut at -0,7 bars.

[poser516]

good info.

[tomway]

Hi poser516

I'm pretty new to this too, but have got so much from this forum thought I'd try to throw a little back.
With a 1KW AC compressor I can pull about 20HG. It wasn't difficult to go this route with a continuous run kit from joe woodworker, but it is rather noisy and I do get overheating problems without a fan (it is about 30c here in Indo at the moment though).

I've had 2 different types of 10kg/m3 foam (which I believe is around 1#) One of them was great up to about 10Hg, the other started to collapse at about 6Hg. Really weird. It looked fine after 1/2 and hour, but when I came back a couple of hours later my vaccum table (which was also covered in melamine to strengthen it up) had deformed in to a massive bow. I guess the message is Keep and eye on it!

[lemat]

Hi poser516

I'm pretty new to this too, but have got so much from this forum thought I'd try to throw a little back.
With a 1KW AC compressor I can pull about 20HG. It wasn't difficult to go this route with a continuous run kit from joe woodworker, but it is rather noisy and I do get overheating problems without a fan (it is about 30c here in Indo at the moment though).

I've had 2 different types of 10kg/m3 foam (which I believe is around 1#) One of them was great up to about 10Hg, the other started to collapse at about 6Hg. Really weird. It looked fine after 1/2 and hour, but when I came back a couple of hours later my vaccum table (which was also covered in melamine to strengthen it up) had deformed in to a massive bow. I guess the message is Keep and eye on it!

1# is 16kg/m3
2# is 32kg/m3 but what is sell for 2 is  more 1,9#= 30kg/m3

So 10kg/m3 is 0,625#

[tomway]

Oh wow! Thanks lemat, I spent hours trying to do the math on this and by the looks of things was way out   

Well the 10kg/m3 is certainly making light boards 

[Marsh]

There's a lot of pumps on Ebay at good prices advertised for Air con and refrigeration which I think can be used?  Is a 3CFM rated one adequate and what does the solenoid do?

[poser516]

man marsh,
I wish I had some answers for you.
FUnny thing, buying a vac pump.  Nobody really knows fully what the measurements do or anything.  It's really difficutl to figure it all out.  Even to buy a pump is difficult.  It's a challenge.

Fuiny.