vacuum pump size

first off ,let me say that I'm green [new] to vacuum infusion.I want to build a 19' long ,4' beam hull [actually 2 of them].I need to know if I need multiple, or just 1 vacuum pump , and what type and size.I'm not "Donald Trump" so I would like to go as inexpense as possible.Oh yeah, the hulls will be cored with core-cell.I usually do my own researh ,but for some reason I'm having a hard time finding information on line.Your input wil be appreciated
thanks JOE

 

Mentioned elsewhere, spend the money and get a PROFESSIONAL machine which costs heaps. Fusion Yachts in Townsville use that method & may help with advice. Else use another method. A half arsed vacuum will end in a total disaster as nothing will be gained if the rosin is not drawn completely throughout with NO Bubbles or voids. Done professionally the result is good.

A domestic vacuum cleaner (even a dozen of them) IS NOT worth considering If you can find a professional operation they may do your moulding & infusion processing. How good are your people skills in securing that request?

 

The capacity of the vacuum is less important than the vacuum that it will draw.

Capacity will speed the time it takes to draw and hold a full vacuum.

If you do an ebay sort on vacuum pump, there are plenty of used pumps available Gast, Thomas, etc.


Ian.

 

Good vacuum pumps last just about forever. One old Welch unit at the shop I used to work at seized this past summer and needed a bunch of seals changed; this was its first overhaul in about forty years.

For infusion, you need a high vacuum, and a virtually perfect bag. No leaks. This is NOT easy to do. Some people have talked about using air conditioner compressors as vacuum pumps; this sort-of works, but the compressor is often lubricated by the refrigerant and so its lifespan will be very limited. Real vacuum pumps generally have an internal oil bath surrounding the moving bits.

Get an old pump off eBay, anywhere from $100 to $9,000 depending on what exactly you want. Most of them are easy to fix, definitely easier than engines, and the parts are cheap (a complete set of seals, gaskets, springs, etc. for a typical shop pump might run a couple hundred bucks, tops).

Even for the smallest parts I always prefer to use two or more pumps. If one snaps a belt, this way you don't lose the entire part.

 

Good points above, by:

Masalai: Get a real vacuum pump, not just a blower. Gast, Thomas, Welch, Kinney, and others.

Ian: The reason for this is that the degree of vacuum (how close the vacuum gauge needle gets to 30" [762 mm] Hg) is the critical element. You need a "full" vacuum to get all bubbles out. As Ian said, a smaller pump will just take longer, not pulling close to full vacuum might hurt the process. I once had to perform a full vacuum test on a 50,000 gallon steel tank for a customer. Only had access to a 5 HP Kinney vacuum pump and a trailer mounted generator. Took 14 hours for full evacuation, but we met the test parameters.

Matt: Two pumps will insure that a pump failure won't affect the process.

Gast and Welch pumps, for example, are simple, reliable, reasonably priced, and used ones are readily available on Ebay and elsewhere. For the size boats you're planning, 1/4 hp to 1/2 hp (3 to 5 scfm at atmospheric pressure) should be enough. Get larger if you can afford it, although 2 - 1/2 hp would be sufficient. Be sure they are rated for 25" Hg or higher.

This article has some very good information and tips:

http://www.reichhold.com/composites/casestudy.cfm?ID=24

 

I picked up a brand new Robinair off of e-bay relatively cheap. They're a good reliable pump and draw a near perfect vacuum. 5CFM will draw down a fairly large project quickly but other than that you don't need a large volume pump. I've seen fella's draw down the big projects with a shop vac first then switch to their other pumps. Where there's a will there's a way. I've only run a few projects through with this setup but it works flawlessly. We're planning a trawler 30.5'x10' sometime in the next two yrs and will use this setup to infuse the hull. Also have a Gast vacuum generator as backup.

 

Knotty, What is the resovoir for? What is a MAC valve and what is the thing between the MAC valve and the resorvoir? Also, how many inches of vacumm is needed for infusion?

 

A near perfect vacuum is required for infusion especially for large or multi=layered fabrics. Well that's what I've been told anyways. My setup kicks out at 29" and back in at about 26" and it seems to work fine.

Here's a lil' write-up I did for another forum.

The challenge was to add some sort of on/off control over the vacuum pump so that it wouldn't have to run continiously. Now this probably doesn't seem like a problem to some of you guys who do small parts with prepregs, fast curing resins and post cures but for me I'm heading towards a full scale infusion of a boat hull that'll be 30.5' long by 10' beam by 6' deep with a full keel and that means on the outside of the hull approx. 70 sq. yrds in one shot!

http://www.fram.nl/workshop/controll...fusion/cvi.htm

The whole process isn't really all that different from what you fella's are doing with your car and motorcycle parts just on a much larger scale. When you start mixing up 10's of gallons of very expensive epoxy for a single infusion you have to be very aware of what you're doing, hence my experiments. I've learned enough from you guys here to feel confident enough to do this on our project.

The long run times for the pump are a result of the ULV epoxy resin used for the infusion of these large scale projects. The working time is over 5 hours with a 24 hr required wait till peeling the bag off. Post curing can speed up the process and that is possible but not very practical for such a large object. Some builders have been able to get upwards of 120 deg F with tents & propane heaters. As much as I enjoy watching the infusion process happen I find watching the epoxy till it kicks somewhat boring!

Ok, here's what I did. On the joewoodworker.com web site they specialize in wood veneering supplies. They also promote the use of a "vacuum press" to ensure proper adhesion of the wood veneer to the substrate. Sound familiar? My brother is a cabinet maker and was looking for better results from his veneering projects when I found that site.

The full vacuum press plans are on the Joewoodworker site: http://www.veneersupplies.com/vacuum_press.php

The veneer press's use a vacuum switch to turn on/shut off their pumps. This helps with wear and tear on the pump while allowing the layup to remain under adequate vacuum unsupervised. In order to achieve this setup there are a few considerations.

The Vacuum Switch: The vacuum switch is very sensitive. Fluctuations in the vacuum within the manifold (see pic) can cause the switch to flutter. This isn't good for the equipment so there's two things required to correct this. Firstly the switch should be as far from the main flow in the manifold as possible, preferably on your main reservoir or catch pot. The switch is adjustable from about 8" HG all the way up to about 29" HG. According to the mfgr it'll require about 4" drop in vaccum to trip the switch for a restart. Mine is about 2" right now but I expect it to loosen up a bit with use. So for example, you have the switch set to stop at 29" it'll restart when vaccum reaches 25" and pull it down again till it hits 29" again. It'll cycle this way continiously for as long as you want.

Vacuum Dampener: A vacuum dampener plumbed just ahead of the vacuum switch prevents fluctuations of vacuum in the high flow areas from causing the flutter. It is simply a fitting with a very small venturi in it that restrict high flow to the switch.

The MAC valve: The MAC valve is nothing more than a solenoid controlled Y valve. In the normally closed config (w/o power) it allows air to flow through a filter into the low pressure side of your pump. It allows air in down to about 4" of HG then shuts closed. This keeps a small vacuum against the low pressure side of the pump which is, as I'm told, ideal for rotary vane type pumps for startup. The idea is to keep high vacuums away from the pump on startup which minimizes high amp draws on startup. When in the open config (w/power) the valve allows a straight draw of vacuum from the pump to the manifold drawing down your system to whatever level you have the vacuum switch set.

The Relay: Larger pumps (over 5CFM) can have significant amperage draw at startup. Anything over 10AMPS will fry the vacuum switch (yes I learned this the hard way). In order to still use the vacuum switch (they make higher amperage switches but apparently they aren't as sensitive) on larger pumps you'll need an alternative way to start and stop the pump. This is achieved by adding a relay. (I'll post a schematic of the wiring when I get a chance). The relay is now controlling the MAC valve and the power to the pump. Wire in a wall switch and you're good to go!

The small reservoir: From what I've been told is required on larger pumps to help the pumps get started under a low vacuum. Apparently it's better for them than starting against a high vacuum or no vacuum. Hence the MAC valve as mentioned earlier. It's nothing more than a 1' length of 1-1/2" ABS with end caps and fitting.

The parts list:

1. MAC Valve $25.20
2. Vacuum switch $24.50
3. Relay $20.75
4. Dampener $10.90
5. Breather fitting (for MAC valve) $2.50
6. Pump Filter $14.95
7. Check Valve $12.95
8. Total: Approx. $115 w/shipping

All parts available from: http://www.veneersupplies.com/default.php?cPath=60_36

You'll also need a couple of rolls of 12 ga. stranded wire and crimp on fittings. Approx. another $10 unless you've got them kicking around.

All in all I felt this was a good mod to the vacuum pump for a number of reasons; no req't to run the pump constantly plus you can set it and forget it, increase longevity of the pump, reduced fire hazard etc. My old grandpa, who was a master craftsman, always told me to look after my tools and they'll look after me! Wise ole' fella he was!

 

Thanks everyone; .I guess the next step will be to get 1 pump and do a series of small projects to get a feel for the system, before I take on the bigger project [and get a second pump].US Composites Epoxy [thin] is 600 cps,can I thin this or do I need to get a special Epoxy [250 cps].Again ,I thank everyone for your help
Thanks JOE

 

I use Max ULV from Polymer Products on e-bay Item #270019321096

http://stores.ebay.ca/Polymer-Products-The-Epoxy-Experts

They show it at 770 CPS mixed and works fine.

 

Thanks Rick! Good information and excellent sites!

 

Joe,
I am infusing 40ft catamaran hulls and only using a 250W pump.
I am using a secondhand laboratory pump I got for $400, very high vacuum but only low capacity. At my lab we have a number of rotary vane oil pumps that have been going all day every day intermitantly on demand for over 20 years with out requiring an overhaul. The one I am infusing with previously ran continuosly for four years. So do not be concerned with having to run a pump for 24hrs, they are designed to do so.
As mentioned you can use a vacuum cleaner initialy to draw down the bag.
With this pump my resin content in the laminate is 30% by weight.

My resin is a standard laminating ambient temperature cure epoxy which hapens to have a reasonably low viscosity of 300cp at 25'C. Infusion resins with viscosity <200cp at 25'C will make the process simpler as you can reduce the number of inlet tubes, increase spacing of feed lines etc.
But I chose not to use the infusion epoxy resins available localy as they all required a post cure at >60'C temperature, and also cost more.

I also have to watch my penies so have chosen 30% shade cloth as the infusion medium rather than fancy infusion mesh, only use 6mm cable spiral wrap from auto shop as the distribution feed line, 8mm clear vinyl tubing (hard type that does not colapse under full vacuum) for inlets and my bag film is a 150 micron clear high density poly ethylene from a hardware store.

You can produce great quality laminates with a basic setup.
Let me know if you have further questions.
Cheers
Andrew

 

Thanks Andrew .Please forgive me but I don't know what 30% shade cloth is ,I guess we have another name for it here in the State's.Anyway I'm going to experiment on a couple of smaller projects first,just to get a feel for it.
Thanks again JOE

 

If you take a walk around the fabric store with the lil' woman you'll find plenty of nylon and synthetic fabrics that'll work as flow media/peel ply. I've tested a few samples and they work relatively well. I even use their polyester fiber fill (type used in coats/jackets/quilts etc.) as a breather material in conventional vacuum bagging. The only thing I haven't had much luck with is the poly plastic from the hardware store as a bagging material.

 

Agree with all of above, you need a high vacuum, suction rate (CFM) only affects how fast the job comes down and also how well it hides leaks!
If you can borrow a digital vac gage, shut off the vac to the job and check the drop rate, 10mb/5 min is what our guys are aiming at on a 40ft hull or deck.

With your back up vac pump don't forget a portable generator, losing vac on a hull infusion is a very bad day...

Paul