vacuum pump size

[Pjitty]

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

[masalai]

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?

[ian_upton]

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.

[marshmat]

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.

[charmc]

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

[KnottyBuoyz]

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.

http://i237.photobucket.com/albums/ff166/KnottyBuoyz/IMG_0415.jpg

[SamSam]

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.

http://i237.photobucket.com/albums/ff166/KnottyBuoyz/IMG_0415.jpg

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?

[KnottyBuoyz]

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 (http://www.fram.nl/workshop/controlled_vacuum_infusion/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! http://www.compositeforum.werksberg.com/images/smilies/wink.gif

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 (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:


MAC Valve $25.20
Vacuum switch $24.50
Relay $20.75
Dampener $10.90
Breather fitting (for MAC valve) $2.50
Pump Filter $14.95
Check Valve $12.95
Total: Approx. $115 w/shipping
All parts available from: http://www.veneersupplies.com/default.php?cPath=60_36 (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!

[Pjitty]

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

[KnottyBuoyz]

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.

[SamSam]

Thanks Rick! Good information and excellent sites!

[AndrewK]

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

[Pjitty]

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

[KnottyBuoyz]

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.

[Polarity]

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

[watergypsy]

I have vacuumed bagged hulls as large as 100' and what I can tell you is that in order to enfuse a hull of the size your talking about you need a pump that has both high volume and high vacuum. [Read Expensive] You need the high volume to draw down the bag and you need the high vacuum to cause the resin to flow. I purchased a rebuilt 24 SCFM / 29 HG pump for about $2600.00 and I don't believe that pump alone would have done what your trying to do. You might want to consider vacuum bagging a wet pre-preg lamination but then you also have the added expense of additional bagging materials which can also be considerable. Forget using visqueen or any of the other short cuts you often hear of people trying. Best of luck with whatever you decide. I think it's an excellent building method if you can pull it off.

[petereng]

Hi Pjitty,
You need to get a pump that can run continously. A chinese 25m3/hr single stage oil vane pump will cost about $1200AUD so is not expensive. This will pull down to 2 millibar. Adequate for your task. You may need to pull the bag down intially with a dust collector or vacuum cleaner but once down it will cope with the process. You will also need a large resin trap. Big enough to hold a standard 9 litre bucket. It needs to have a clear top so you can see the resin level in the bucket. This is because as a beginner you will inevitably get resin through to the pump which is a very bad day. If you can see the bucket you can turn the taps off on the trap then change the bucket, then put the vacuum back on. The pump has to run continously otherwise the bag will decompress, even if you have a "perfect" bag the dissolved gases in the resin will decompress the bag enough to get a poor result.

Peter

[Pericles]

Peter,

"The pump has to run continuously, otherwise the bag will decompress, even if you have a "perfect" bag the dissolved gases in the resin will decompress the bag enough to get a poor result."

That explains everything, because I thought I was still getting out gassing even after thoroughly warming the cold marine ply. Logic indicated I could turn off the pump on a composite test panel I was vacuum bagging with a vacuum cleaner after laying up by hand. A resin trap was not necessary for this procedure.

The cured panel was OK, but not the quality I expected. A timer for the vacuum cleaner might work to prevent overheating. I wonder if a vacuum pump powered by flowing tap water exists?

Cue http://en.wikipedia.org/wiki/Vacuum_pump

Pericles

[KnottyBuoyz]

My pump does't have to run continiously. See my previous post. I can set the vacuum switch to kick off at 29" and back in when vacuum falls to 27". It'll cycle itself off and on as required requiring no intervention from me. The resin I used has a very long curing time +8 hrs so I could just set it and forget it, come back 24 hrs later and demould.

[petereng]

Hi Rick,
For infusion it is very important for the bag to hold constant volume. If you turn the pump off and on the bag volume changes. It gets bigger as the pressure decreases, which means that something must be entering the bag to increase its volume. This means you have leaks or the resin is outgassing. 27"Hg is 90% vacuum, 29"hg is 97% vacuum. At 90% vac outgassing is unlikely so you have leaks. This means your bag volume is cycling with a 7% volume difference, I would not recommend this as a robust system. Personally I run my infusions at 99.8% vacuum or 29.9"Hg continously. This maintains a constant bag volume, evaporates any water in the job and bebulks/consolidates the laminate stack to the same thickness everytime.

If your happy with your results thats OK, but you will get variability and occassional problems with this system.
Peter

[Pat Ross]

Kelsall Catamarans has been using Resin Infusion as a standard for 7 years. He will be here in the U.S. for a workshop in Florida. If you are interested in seeing the RI system in use there is still time to enroll for the workshop. Here is the link

http://www.multihulldynamics.com/news_article.asp?articleID=139

Pat Ross

[Fram]

I have vacuumed bagged hulls as large as 100' and what I can tell you is that in order to enfuse a hull of the size your talking about you need a pump that has both high volume and high vacuum. [Read Expensive] You need the high volume to draw down the bag and you need the high vacuum to cause the resin to flow. I purchased a rebuilt 24 SCFM / 29 HG pump for about $2600.00 and I don't believe that pump alone would have done what your trying to do. You might want to consider vacuum bagging a wet pre-preg lamination but then you also have the added expense of additional bagging materials which can also be considerable. Forget using visqueen or any of the other short cuts you often hear of people trying. Best of luck with whatever you decide. I think it's an excellent building method if you can pull it off.

May I make a distinction. Vacuum is vacuum, for this you need a pump that is able to pull that vacuum. Capacity is not important, it just takes longer to get that vacuum. I consider a small pump for my big infusion jobs (40'hull) as an extra safety fuse. My small pump will not overcome leaks in the bag while a big pump can hide them, that is to say till you open the resin valve. A perfect bag does the trick, not the size of the pump.

[marshmat]

Using a shop-vac to pull the bag down initially works very well. Sealing up the hole for it once the bag is loosely sucked down is not difficult, a few strips of flash tape work fine.

If the bag is perfect, a remarkably small pump can do the job. It's amazing how few bags are perfect. A big pump shouldn't encourage you to be sloppy, but it will help to hide any inadvertent errors you might make in taping the bag up.

I don't think I'd ever want to use a single pump for anything of significant size. Most of the bagged parts I've done (largely prepreg), I used two pumps, even for stuff only a couple of square metres in area. You never knew when someone would run one of the pumps with no oil, or when one would break a belt, etc. The second pump also helped compensate for any pinholes that formed in the bag.

[terhohalme]

A small ejector pump did nicely suck over 30 kg of resin in 40 minutes. The Ejector made vacuum typically 65 -70 % with or without sagging.

[Herman]

We build vacuum pumps for the composote industry, and we use any pump of choice (6 m3/h to 150 m3/h), switched with a vacuum switch. (We use a RT121 from Danfoss for that). This vacuum switch is adjustable (by hand, no fancy electronics) for any desired vacuum level, and also an adjustable hysteresis, which can be between 3 and 100 mbar. (we normally set it at 8-10 mbar).

Big advantage is:
-reduced cost (no pump running 24/7)
-audible warning for leaks. When the pump switches on more often, it is time to take a look.
-adjustable vacuum.

----
There is nothing wrong with using a vacuum cleaner for getting the bag down. Just put the hose under the bag, suck most of the air out, then close the last part of the bag. But remember a vacuum cleaner is dependant on moving air for cooling. No moving air, no cooling...

----
About resin infusion media: I am surprised to hear about sunscreen material. I am sure it works, but at least here it is way more expensive then the infusion media we sell...

----
About bags: Be carefull with Polyethylene bags. Usually there is a fair amount of recycled material in it, which tends to make the bag porous. Chasing leaks becomes an interesting job then... This seems to vary from batch to batch.
There are multilayer bags, like the L500 from Airtech, which are made of PE film, sandwiched between nylon film (or the other way round, I forgot). However, they make for durable, leak fee bags, and quite economical.

----
Water-driven venturi style pumps: Yes, they exist, I used them in the old days at school in chemical class, however, lot of water, low air flow. (quite high vacuum however). IF you get hold of them, opt for running them in a closed loop with an electrical pump. (or try and explain the African people that you are using potable water just for generating a vacuum...)

[barrylay]

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

Andrew, Can you describe where the 30% shade cloth is situated in the layers of the laminate? Is it like a peel ply that peels off after the resin is cured? If it peels off, as I suspect, what kind of finished surface are you left with?

Thanks

Barry

[Herman]

You need some sort of separation layer between your laminate and your infusion mesh. Usually this is a perforated film. (more perforation = better)

Peelply also has the name of acting as a release layer, but unless you use a release coated peelply, removing the infusion mesh (which holds resin afterwards, and thus pretty strong and non-cooperating) and the peelply at once is a hell of a job.
Usually peelply is only used at places where it also performs another function: That of leaving a course surface, ready to accept further laminate, glue or anything else.

So basicly:

-laminate
-peelply (optional)
-perforated film
-infusion mesh
-runner system
-vacuum film

[barrylay]

Herman, thanks for your reply. So, I can eliminate the peel ply by using a perforated film? And if the perforated film and presumably also the infusion mesh contain resin when the resin has setup does that resin come off with the film and mesh or does it remain as part of the composite? If it remains it seems it would be useless added weight.

I did see some kind of demo on one of the websites or forums that showed all this, but I can no longer find it.

Regards

Barry

[KnottyBuoyz]

I'm waiting for samples of "Soric" bulker/flow media.

http://www.lantor.nl/index.php/id_structuur/10599/soric.html

Interesting concept for a flow media that remains as part of the layup as a bulker. I know a little off topic for peelply/films but still part of the equation.

You can eliminate the perf film if you want a rough surface (texture) to your finished panel. The flow media and peel ply will bring any cured resin with it when you peel it back from the panel. Some builders leave their peelply on a panel while they're working it to protect the surfaces. Makes it a little harder to get off later after resin fully cures and if you do this you should use treated peelply only or you might not get it off! Don't ask me how I know this! :rolleyes:

I've got a bunch of links to vids somewhere. Try Youtube or Google "Resin Infusion".

[IHTFP]

I've got a large 5 HP 3-phase power water cooled vacuum pump that is no use to me if you are interested. It is the TCP-50 model

http://www.anver.com/document/vacuum%20components/vacuum%20generators/pumps-tcp.htm

email me at donzi22classic@yahoo.com if interested.

[Herman]

The excess resin comes of with the infusion medium.

Try and always use perf. film. Below the perf film you optionally use peelply. This way you can always easily remove the infusion medium (and the perf film with it) and in areas where you have the peelply, you can leave it there, if desired. This will protect the surface from debris and foot traffic. Remove it just prior to further laminating, gluing or coating. Very usefull for insides of hulls, which see a lot of traffic and thus pollution during the further build.

About Soric: Great product. This product makes it possible to infuse without infusion mesh, and without the weight penalty of other "stay-in-the-laminate" distribution mediums.

2 things to watch for, though:

-1. You cannot control the infusion strategy as much as with a setup using mesh and runners. (not important for square panels and similar)
-2. You must make a resin entry into the Soric. So at your resin inlet, you should have the soric exposed, not buried under layers of glass.

Depending on the type of soric, expect to use 600-700 grams of resin per square meter, per mm thickness. (sorry, not used to imperial units that much)

One other thing which I discovered, and which is not (yet) in the datasheet:
After having pulled a vacuum, leave the Soric under vacuum for at least 30 minutes, preferably a bit longer. This will make the trapped air in the balloons of which the Soric is made to escape as well. Failing to do so will give you a laminate with air-filled soric channels, instead of resin filled...

They will include that in the datasheet, but I have no idea if they have done that yet.

[Fanie]

I finally got some vacuum guages. They draw to 75 kPa (out of 100) with the dry vein pumps I have. How good or bad is this ?

Another concern is the vein pumps gets very hot if I block the air to draw the maximum vacuum it can. Is this normal ?

Had a power out due to unexpected hail. Mental note - keep a generator handy.

[Herman]

How hot is hot? An oil lubricated vane pump gets amazingly hot. (do not hold your hand on it, it will be approx 80 degrees C). Just make sure the electric motor gets ventilation.

-0,75 is not bad. Could have been better, but is very doable.

If the hail was expected, would power have been lost as well? Indeed: keep a (working) generator at hand...

[Fanie]

Hi Herman,

I could still hold my hand on the pump area, and the motor is not hot at all. The little air that is puffed out is very hot, I can just imagine how hot the veins must be getting.

I have other vein pumps, a different make, I'll put them up and see if I get a better vacuum, maybe use them instead.

What is worst case, and what is considered good ? 100% :D

I was thinking of having a 'portable' vacuum pump for areas where air is trapped in. Stick a needle in the trapped air part and vacuum the pocket out, patch the hole with tape when done. Could this work ?

I asked for a 500kPa vacuum guage, the guy said they don't have any :D

[AndrewK]

Barrylay
Your question has already been answered nicely by Herman.
When using release film under the infusion mesh I still recommend that you use peel ply. I purchase this directly from a textile supplier at half the cost from fibreglass suppliers, here it is sold as plyester taffata. I mostly use a 60g sqm. 30% shade cloth here costs $1.70sqm where as cheapest infusion mesh is >$5sqm. Also it only wastes ~325g sqm of resin. Like any infusion mesh shade cloth will leave a very small indentation, this is not a problem and you always have one smooth side.
I use the attached file to determine the resin required for a job, it will also show you the relative costs of matterials.

[AndrewK]

Here is the file, cuold not attach it with quick reply

[Pat Ross]

Barrylay
Your question has already been answered nicely by Herman.
When using release film under the infusion mesh I still recommend that you use peel ply. I purchase this directly from a textile supplier at half the cost from fibreglass suppliers, here it is sold as plyester taffata. I mostly use a 60g sqm. 30% shade cloth here costs $1.70sqm where as cheapest infusion mesh is >$5sqm. Also it only wastes ~325g sqm of resin. Like any infusion mesh shade cloth will leave a very small indentation, this is not a problem and you always have one smooth side.
I use the attached file to determine the resin required for a job, it will also show you the relative costs of matterials.

I was able to purchase shade cloth from Lowe's hardware for 34 cents a foot, it was 6 feet wide. We infused three 30 foot panels and this worked well.

Pat

[barrylay]

Hey all you guys - many thanks. Lots of good information here. The scare factor is the major thing for me. I have always been afraid of large expensive flowing masses that set quickly and potentially could become a huge disaster - concrete, resin, etc. Got to plan well.

I am not yet sure that my application warrants the infusion process. I am considering doing an 18' (5.5m) stitch and glue boat, which only has one layer of glass on the exterior. If anyone is interested it is the i550 and can be seen at www.i550.org.

Why I was considering it is because of the lightness and the possibility of doing more than one boat, either two simultaneously or two sequentially. I am trying to come up with a plan to have a female mold and possibly avoid all the stitching. I am just not sure if a female mold could be made with tight enough tolerances to have all edges, chines and gunwales, meet nicely.

Any ideas?

Regards

Barry

[Fanie]

http://www.boatdesign.net/forums/boat-building/minicat-5-a-24096.html

[barrylay]

Andrew,

Do you have an alternative for a resin trap?

Thanks

Barry

[KnottyBuoyz]

Andrew,

Do you have an alternative for a resin trap?

Thanks

Barry
If you can't find a reasonably priced paintpot to make into a resin trap a length of 4" PVC pipe and endcaps work just as well. It's the white pipe on the right. The black one is just a reservoir I used because I had it.

http://i237.photobucket.com/albums/ff166/KnottyBuoyz/newsetup002.jpg

All you need is a 1/4" NPT tap for the fittings. Just be careful when you drill the caps you don't split the cap. Drill before gluing to the pipe. I put a screw on cap (cleanout) on the bottom. I think the total cost was $15

[barrylay]

Rick,

Thanks. So how quickly will the pipe fill with resin? It looks pretty permanently fixed, not that disposable. I can't imagine being able to remove any resin even with the cleanout at the bottom.

I tried a plastic paint bucket, but it didn't hold the vacuum.

Barry

[KnottyBuoyz]

Rick,

Thanks. So how quickly will the pipe fill with resin? It looks pretty permanently fixed, not that disposable. I can't imagine being able to remove any resin even with the cleanout at the bottom.

I tried a plastic paint bucket, but it didn't hold the vacuum.

Barry
Hey Barry

I guess it depends on what you're infusing. I've only done small parts (2' dia). Just a few drops got to the trap. Ideally you'd get none in the trap. On large parts you'll want to stop the resin inlet when the part is about 3/4 infused and the vacuum will continue to pull the resin into the part. If you have multiple vacuum lines on large parts (best strategy) you can crimp them off before the resin hits the lines. Check out some of the videos on Youtube on infusion and you'll see them crimping off the resin lines when the part is near finished and the resin will continue to flow completing the part. It seems counterintuitive to newbies but when you think about it and try it a few times it actually works and gives you the best resin/glass ratios.

I certainly hope I never fill my resin trap! It's probably a gallon or more in capacity and that's near $100 in resin & hardener going into the trash bin. I've eventually got a 31' boat hull to infuse and controlling waste on a project that size is very important.

I greased the inside of the trap with vasolene as well as the threads to the cleanout. Nothing will stick to the inside I'm sure.

[AndrewK]

Barrylay

I always calculate the amount of resin required for the job with my spreadsheet, depending on the size of the job and compexity of the resin feed lines the amount of resin going into the catch pot is 100 - 300g.
Rick is correct that you stop feeding resin well before the resin front reaches the vacuum lines, if you dont you will be waisting a lot.
I use a 10L paint pressure pot because I was given an old one for free, I place a cut down plastic bucket inside to catch the resin.
The down side with this is that you can not see inside, you have to judge by weight. I was going to cut a 50mm hole in the lid and seal with a clear perspex to act as a window but never got around to it as it has not been an issue.
An alternative is to pick up an old pressure cooker from a second hand store and use this in the same manner.
Another alternative is to use a wine bottle. Before I was given the pressure pot this is all I used in fact still do at times just so that I have an excuse for drinking the stuff.
The only qualifier I make here is that the resin being used has to have low exotherm, if not the bottle may crack due to thermall stress and you will lose all of yor vacuum. So if you are unsure about your resin then do not use glass.
The other thing to make sure is that the resin inlet tube is inserted further into the bottle than the vacuum line and you could always put a couple of bottles in series for added security.

So if you can not get a hold of an old pressure pot or pressure cooker and you do not want to risk the wine bottle then make a fiberglass container by moulding over an inverted plastic bucket or a flower pot large enough so that the standard 9L bucket will fit inside. You need to incorporate a flange on top, to which you seal with a clear perspex lid ( O ring or simply tacky tape).
Connect your resin line, vacuum line and vacuum gauge to the perspex lid.
The fiberglass would have to be approx 6mm thick to whitstand 100% vacuum.

Cheers
Andrew

[barrylay]

Rick and Andrew,

Thanks again. I am still unsure if I can even use an infusion process as I am going to be building a stitch and glue boat. The fiberglass would be over the plywood and I am told by Herman on this list that plywood is too porous to hold a vacuum. I was going to do a test, but maybe you also have opinions or techniques about doing that. Is it possible to do infusion on plywood?

Barry

[barrylay]

Upon reflection it mightn't have been Herman - sorry Herman. But someone did tell me that you cannot infuse over plywood.

I figure I could do the infusion if the panels were done before assembly by having the vacuum bag totally encase them, that is both sides with sealing tape between the two sides of plastic, ensuring a vacuum. However, that would mean some pretty bulky seams when assembling, as the glass would be several more layers thick there.

Ideally I would like to do the infusion over the hull after it is stitched up. Then I could just overlap the glass at the seams, just like a surfboard is done - just two thicknesses at the seams. But then I would be forced to seal at the edges of the plywood panels, and that's when the questions come up can you get a seal there and is the plywood too porous to maintain vacuum?

Any thoughts, suggestions, revelations?

Barry

[petereng]

Hi Barry,
It is possible but my question is why? With the stitch and glue (S&G) method you will need to ensure all the ply edges are vacuum proof as well. Usually there is only a thin layer of glass added to the ply. The ply provieds the stiffness and the glass provides the strength. If you want to infuse over ply you will need to "paint" a layer of resin over it to seal it, perhaps two coats. Then you will neeed to use a media and peel ply. By this time and effort you would have finished it by doing it wet or perhaps even a light vacuum bag. If you wanted to infuse the boat use foam for the S&G then at least you have saved a lot of weight for your efforts.

Peter S

[marshmat]

I tend to agree with Peter here. You probably could find a way to infuse over stitch-and-glue. But sealing it up would probably take as long as hand-laying the whole thing to begin with. Plywood will hold a bit of vacuum, if you can seal to it- which is not easy. And envelope bagging a hull sounds like more effort than it's worth.

I think you'd probably get similar results by spending the money that would have gone into bagging gear on some good multi-axial fabrics, instead. Even hand laid, it's possible to get some pretty good fibre/resin ratios with stitched multi-axial fabrics.

[barrylay]

OK, I think you guys have me convinced. I agree with the cost and effort being excessive. It seems like the hand layup is the easier way to go. I have never done a large area of layup, so that was what was a bit scary, and the control of the infusion process was appealing.

Thanks

Barry

[AndrewK]

Barry
For smaller S&G ply boats normall practice is to only resin seal inside and light weight glass on outside, so the benefits of infusion are only marginal.
If you want to save weight and use infusion then build in foam. You can still use S&G by premanufacturing the panels.

[barrylay]

Andrew,

I had considered premanufacturing the plywood panels (foam would add to the cost) with one side glass as you say. The problem I had with that concept was that you end up doing the layers backwards. With S&G they say to tape the seams, then cover that with a full layer of glass. With Prefabbed panels it ends up being something like 1) first layer of glass (full layer premanufactured) on the plywood, 2) second layer of tape, 3) third wider layer to taper off the tape edges. You never get the smooth effect of the full glass layer covering the taped edges, or at least I can't see how to do that. Seems like it would be better with foam because you would use more layers of glass.

Barry

BTW where are you in Oz? I used to live in Sydney, now in Arizona - miss the ocean.

[masalai]

I don't build, but I have looked at several designers of kit boats using balsa panels pre-covered with glass, precut to the patterns and joined using a female frame and taped in the inside, then before the bridge-deck are rolled over and the outsides are done with tape and then finished (including all bottom finishing to just above waterline, taped and covered with plastic apron to protect from dribbles and other splashes etc - the peel-ply stays on for the sides to protect the sides and chamfer then the return to upright for build or bridge-deck and rest of exterior remove peel-ply and bog and sand before final paint finish... I guess ply S&G would be somewhat similar - the method of finish anyway... :D:D:D

Not the best example but some idea and mistakes can be seen here http://www.thecoastalpassage.com/bblog.html - click on the lighthouse sketch to return to the website home page.... enjoy - - lots or reading from Queensland Whitsundays region

[sailfish25]

Sweet - i have a nice 6cfm vac pump I bought off of amazon. one of the robinair types for Airconditioning systems. It seems to work great.
just an FYI for those looking for a good home, low cost alternitive.

[AndrewK]

Barry,
I have lived in Brisbane now for 20 years, before that in Melbourne.

Although building in foam alows you to make rebates where the glass is overlaped I would not be too concerned about the tape overlaps in your S&G.
The thickness of the tape should be <1mm.
What type and weight of glass is your outer laminate? any on the inside?
Weight of tapes?
In small S&G ply boats the outer laminate is usualy only 200 - 400g/m2, and its there mostly for waterproofing rather than strength.
If this is same for your case then hand laminating is better than infusing as it will be more resin rich.
Light weight plain weave or DB glass wets out easily so you should have no problem in laminating the hull of your size in one hit on your own.
If you are having 2 tapes + laminate along the chines it does not matter in which order you place these you will still have two steps in the glass.
Personaly I would place the glass fabric down first then the wider followed by smaller tape on top. This way when you are sanding you can not acidently sand through your longest fibers, only the edge of the top tape.
Another thing to keep in mind when laminating over timber is to do it at stable or falling temperature. If you have rising temperature you will have some out gassing.

Best of luck
Andrew

[Fram]

Upon reflection it mightn't have been Herman - sorry Herman. But someone did tell me that you cannot infuse over plywood.


Maybe you saw it on my website, with an attempt to infuse a plywood daggerboard case.
http://www.fram.nl/workshop/mainhull/album/Daggerboardcase/photos/photo11.html

I had to know better as Herman has told me a simular story that I had forgotten about.

By the way, I came across the perfect vacuum system at
http://www.vacmobiles.com/
and now testing the vacmobile 20/2 for my Fram project. A big step forward in comparison with my humble laboratory pump.

Henny

[Herman]

Oh, yes. plywood is a very "leaky" product. I once used it (uncoated, hurry, hurry, hurry) as a flange on the transom (only 4 ft wide!) of my mould.
When pulling a vacuum, you could clearly hear the air racin through the plywood. Luckily I was only installing honeycomb, which needed not too much vacuum, and the vacuum pump was oversized.

Another example:
A company set up an infusion, and they liberally coated the flange (MDF panels) with epoxy, to make them airtight. Perfect solution. The only detail was that they cut the peelply to size with knives ON THE FLANGE cutting through the epoxy layer... Man, that was something...

The vacmobile indeed is a very nice unit, and we have been tempted to import them. However, to be honest they did not really add to the line of materials we already have...

----
To come back to the core of the thread:

Basicly, any pump can do the job, as long as the pump is larger in capacity then the air leaking into the bag. A careful applied bag will save on pump capacity.
Overcapacity is needed with a leaky bag, leaky seams or when trying plywood...
With infusion, air leaks are highly undesired, so the utmost must be done to prevent leaks. So you can conclude that a large pump is not needed then.

To pull the majority of the air from the bag, use a vacuum cleaner, put the hose in the last bit of seam that still needs to be put down, and turn it on. A vacuum cleaner has a larger capacity, but hardly pulls a vacuum. Besides, it is dependant on air passing for cooling the engine, so it is not usable for the real deal. But it is very useful for getting the first 90% of the air from the bag. (very useful with large bags, largest I have witnessed was over 30 meters (100ft). Took a while to get the bag down...

[ahender]

Sailfish25:

I too got a Robinair pump off the Internet thinking "what a deal!"

Worked great for small test projects.

My first attempt at resin infusing a 13 foot male canoe mold failed yesterday due to the pump overheating.

I had actually connected two Robinair pumps together and they bold failed after less than 2 hours. So much for having a backup.

Lesson learned, spend the bucks and get a descent pump -- a "continuous use" pump.

My e-mail to Robinair, and their response, "the pump is not recommended for non-HVAC purposes."

One would think a vacuum is a vacuum regardless of what is being vacuumed.

Apparently not.

alan

[KnottyBuoyz]

My first attempt at resin infusing a 13 foot male canoe mold failed yesterday due to the pump overheating.

I had actually connected two Robinair pumps together and they bold failed after less than 2 hours. So much for having a backup.

Lesson learned, spend the bucks and get a descent pump -- a "continuous use" pump.
Hey Alan

I've run my Robinair continuously for 8 hrs or more and it's never overheated. Were the oil reservoirs full?

I don't normally like leaving equipment running continuously for extended periods of time and you can see how I addressed that issue earlier in this thread...

http://www.boatdesign.net/forums/fiberglass-composite-boat-building/vacuum-pump-size-20419-4.html#post172840

If you've got a good bag with no leaks there's no need to have your pumps running continuously.

Rick

[ahender]

The oil was topped off in each pump.

My pump has less than 2 hours on it.

A similar pump I borrowed was an older model.

The older pump quit, then my pump quit about 30 minutes later.

Using a thermal gun, the housing on both units was in the upper 140s.

The ambient temp was 70 degrees (in my basement).

I was pulling about 21 inches.

There were some leaks I could not seal properly.

alan

[marshmat]

70 F above ambient is running kinda hot there, Alan....

I had to rebuild a 40-something year old Welch two-stage rotary vane pump a few years ago after someone (not me) ran it with no oil for eight hours or so. Welch were amazingly good about getting parts, seals, etc. for this thing even though it had been out of production for two decades. I had to have two vane guide pins custom machined though.

Think about it- that was a pump from the 1950s, it saw heavy continuous use in laboratories for 30 years, then had the s*** beaten out of it in a composites shop (running continuously for 10 hours plus, sometimes running on a generator in the back of a moving trailer) for another 20 years. And only when someone ran it dry, did a seal finally fail.

Good pumps do not spontaneously fail in a matter of hours for no apparent reason. But something not meant to pull vacuum for hours on end.... well, it might not have the cooling capability needed to survive in a shop. It's not a terribly demanding task for a decent pump (nowhere near as demanding as pulling down a cyclotron or an ion chamber), but modern cheap stuff from ebay just might be a little underbuilt.

[Herman]

I've had a Welch as well, a 1396 I believe. I swapped it for a smaller, contained pump, as the Welch was simply too large.

I do remember however the sign on the motor:

"please lubricate every 10 years"

I guess they don't make them like that anymore...

However, the Robinair pumps switching off surprises me. Are they produced for 100% workload? Or perhaps 50%? any pump used for composite work should be able to do 100% workload (or: 24/7 running). This should not harm the pump.

The trolleys I produce however have a vacuum-regulator, which switches off the pump when the desired vacuum level has been reached. This way you can trace leaks, the pump does not run all the time (energy bill!) and if the pump starts running more often, it is time to check the workpiece.

Vacuum pumps can get hot. In celcius, a temperature of 80 degrees C is normal. Although you cannot touch the pump housing anymore, the pump has no parts that are harmed at that temperature. (it is all steel, bronze and some seals and gaskets)

[ahender]

Thanks for all the great comments.

I am looking at Thomas and Gast vacuum pumps at grainger.com.

My budget is ~$800.

Gast has a 1 hp, 13 cfm, Hg 25" model for $844.

Thomas has a 1/2 hp, 4 cfm, Hg 27.9" model for $661.

These are all oil less pumps.

I'll be pulling the vacuum on a 13' canoe mold.

Since there is not a lot of air to evacuate am I better off with the Thomas pump since it has a higher vacuum rating or is horsepower always the better bet?

thanks....alan

[Herman]

How much vacuum do you want? Probably not the "full pull" from either pump. Why not invest in a smaller pump, and a vacuum switch? Makes things much more civilised and controllable.

[KnottyBuoyz]

Plenty of Gast vacuum pumps on e-Bay in the $200 range.

http://shop.ebay.ca/?_from=R40&_trksid=m38&_nkw=gast+vacuum+pump&_sacat=See-All-Categories

[AndrewK]

Alan,
I agree with Rick, if you are not a professional builder then a cheaper second hand pump makes more sense.
The type and capacity of the pump depends on your requirements.
If you only plan to vacuum bag a canoe then a small diaphragm pump would be my choice. Most diaphragm pumps will only achieve 80-90% vacuum but can be run at any level and usually have a built in bleed valve to regulate this.
Oil pumps have higher vacuum but generally are designed to run at full vacuum only, this is what you need for infusion work.

Andrew

[ahender]

What would be your definition of "small?"

1/4 hp, 1/3 hp, 1/5 hp?

thanks...alan

[AndrewK]

Alan,

I have been fortunate to have been able to borrow a number of vacuum pumps from my ex employer (lab).
I use a 200w(1/4HP) diaphragm pump for vacuum bagging, it reaches 80% vacuum and has only small volume capacity that may only be around 2L min but I have not measured it. I have made all of the bulkheads for my 12m catamaran using this, also flat panels up to 3 x 1.5m.
I have two oil pumps that I use for infusion a small 250W one that reaches 96% vacuum and once again only 2-3L min capacity, I have infused 6 x 2.5m laminates with this.
The larger oil pump is still only 1/2HP twin stage almost 100% vacuum and once again only guessing 5-10L min capacity. This easily does half a 12m hull.

I am not saying that volumetric capacity is not nice to have just that its not worth paying the extra money unless you are a professional. It is easy enough to draw down large volume bags initially with a vacuum cleaner.
The essential thing is that what ever type of pump you get it is designed to run 24hr.

From my experience most labs will have a old disused pump gathering dust in their store, do some ringing around you may end up with one for nothing.

Andrew

[sigurd]

do you put epoxy on the corecell before you infuse it?

[AndrewK]

No you assemble everything dry and only mix and introduce your resin after you have determined that there are no leaks in the bag.

[ahender]

How many layers of cloth are you infusing?

alan

[Wynand N]

How much vacuum do you want? Probably not the "full pull" from either pump. Why not invest in a smaller pump, and a vacuum switch? Makes things much more civilised and controllable.

somewhere is a thread with photos where I made an experiment with two vacuum pumps pulling two identical areas with the same layup. One panel only had a 6cfm pump connected, the other panel a pump of similar rating and connected with that pump, a cylinder with about 115lt of vacuum. When the pumps reached an identical vacuum, -87kpa at my altitude, the resin feeds were open. The cylinder with (stored) vacuum was open with the one pump, sucking the same line.
In theory the pump with the vacuum "boost" cylinder should infuse faster but the result showed such a little difference it can be ignored.

Best listen to chaps and go for a good smaller pump and that should do the job.

[sigurd]

alan are you asking me? for the hull only two light ones, for the fin it will be thick - 2-3mm or more.

[ahender]

Actually I was asking Andrew.


alan

[jim lee]

ahender

We use this one.

McMaster-carr www.mcmaster.com PN 4396K45

It pulls between 29" & 30" HG an goes for : $726.91

For a smaller boat like what your are doing, it would be my pump of choice.

-jim lee

[AndrewK]

Alan,
Its a foam sandwich so the laminates are relatively light, 450 - 1200g sm.
I have done a solid glass test block for the flange of the mast connecting beam, this was 24 x 450g UD + 4 x 450g DB. This worked out flawless; no bubbles & translucent, the only thing you can see is the stitching thread. I hope the real ones work out just as well when time comes.

[ahender]

Andrew:

When you infuse all the materials at once, do you worry that some areas may end up dry?

What do you see or not see that would indicate everything infused properly?

alan

[AndrewK]

Alan, with glass reinforcement it is very easy to see dry spots, these will stay white while the resined fibers will go translucent. If this happens and you end up with a dry island spot all you do is attach a vacuum line to the bag on top of this spot. This will draw the resin into the area, once it goes clear you can clamp this line. Of course you can only see what is happening on top of a core, you can not be sure that the bottom laminate is OK until you de-mould. But in my experience providing your core has sufficient perforations if the top laminate is OK so will be the bottom.

Also I do not infuse everything, most of my catamaran bulkheads especially if they have cutouts in them I have vacuum bagged.

Andrew

[13AL]

Wow, great info. After reading the thread, I was wondering if you Pro's have a formula for square footage or cubic footage per cfm of vacuume required. I realize this may be hard to determine due to the laminate count but a "rule of thumb" would be helpful.

[KnottyBuoyz]

Wow, great info. After reading the thread, I was wondering if you Pro's have a formula for square footage or cubic footage per cfm of vacuume required. I realize this may be hard to determine due to the laminate count but a "rule of thumb" would be helpful.
Not sure what you mean. A rule to determine vacuum pump size based on the square footage of a layed up panel?

I think the point we tried to get across is a vacuum is a vacuum and the volumetric capacity of the pump has little to do with that. A larger (volumetric) pump can remove more air from a laid up part. A smaller pump will do the same job just takes longer. If it's a really big part use a shop vac to get rid of most of the air volume in the lay up then switch to your regular vacuum pump.

I use the same pump for a 1 sq. ft. part as I plan to use on the infusion on my 31' trawler hull.

[AndrewK]

13AL
I am no pro, but basically even the small pumps out in the market can do reasonably large jobs, big capacity is nice to have but not essential.
I don't know what the pros would say but for a very small pump if you only used 1/2 the volumetric capacity to suck the resin in and the other half in reserve to chase up any minor leaks that may develop during infusion without losing pressure seems like a good starting point.
Say you had a 10x2m panel and 1mm stitched glass laminates either side of a core.
10mx2mx1mm=20L x 2 =40L and with a full vacuum your glass volume fraction for stitched reinforcement will be approx 50%. This means that out of the above 40L the void to be filled by resin is 20L. Add say 0.5Lm2 for the transfer medium and plumbing this makes 30L total resin requirement for the job.
Personally I would be happy to take 30 minutes to infuse such a panel, this makes 1L/min of resin plus 1L/min spare capacity, so the total volumetric capacity of the pump required is 2L/min.
How does this sound?
Sorry US guys you will have to do your own conversions, metric is so much easier.

[13AL]

Gentlemen, thanks for the replys. That cleared things up a bit. Our main concern was having a pump(s) too small and running the life out of it. We found a 5 hp near by that looks promising and considering installing a system like Rick built. I'm sure the 5hp will be overkill but the price is right. AndrewK, thats some good stuff right there. The more info like that we can get the less costly the mistakes will be. Dan.

[AndrewK]

13AL
Make sure the big pump is a high vacuum pump. Once you have exceeded the minimum capacity you require I would rather have a small 99.9% vacuum pump than a large one at 95%.
Automatic switching such as Rick's would be nice especially since it is 5hp. Just make sure the cycle range is small, say2%?

[13AL]

We had taken that into consideration (99.9%) and will be running it this weekend to find out just that. I am guessing here, but our goal is 29.9-30in ? The only draw back to Rick's system is cycling our large motor a bunch. Sometimes it's lighter on the power bill to let a large motor run rather than start stop. Then again, It's only money. I'll just make more. In case our big pump is'nt so big after all, we were viewing E-bay and had noticed what seemed to be some pretty good buys, however we could not find the vacuum ratings which made us a bit apprehencive. These particular pumps were Alcatels and Sargents. They look to be a vein style? Any info about these? or should we keep looking. Thanks, Dan.

[KnottyBuoyz]

The only draw back to Rick's system is cycling our large motor a bunch.
The relay that controls the pump can handle 30 amps. That should start pretty much any motor up to 3 or 4 HP. Your pump should have it's start/surge amperage draw on the mfgr's label. I know the Robinairs don't. I originally had the 10 Amp relay installed and fried it. IIRC my Robinair is 1/3 HP.

[13AL]

Rick, Thanks for the heads up. Will the Robinair produce 30" vac?

[KnottyBuoyz]

Rick, Thanks for the heads up. Will the Robinair produce 30" vac?
Damn near! Near enough anyways. I've got the regulator set to shut off at 28 and back on at 26. I have bottomed out the vac guage (30" hypothetical) w/o the regulator. These are uncalibrated readings though. I don't have the equipment to verify if they're actuals.

What I've found with my experiments is that the 26-28" range works best. I've come up with a few "dry" layups under very high vacuum where I've literally sucked the resin out of the layup or the overlying materials, peelply, flow media & bag have so compressed the layup that it couldn't absorb any resin.

So I guess, and others may confirm this, that achieving 30" of vacuum isn't really "the" most critical specification for a vacuum pump. Duty cycle is probably more critical and we've talked about that.

I think it was Wynand with his experiments showed the benefit of having a large vacuum reservoir when infusing larger panels. Mine is about 1.5 cu ft in size. I draw that down to 28" keeping clamped off from the layup until I'm ready to infuse. Bringing the layup under vacuum quickly seems to help eliminate some creases and bridging. Just an observation.

[13AL]

Update: Tested out large vac pump with poor results. 16" was all it would give. Lucky for us all we had in it was some labor. Now it's off to Graingers for a pair of 1.5 hp pumps. I kinda had a feeling we were going to end up here. Not to jack the thread but.... has anyone had any kind of luck infusing past 90deg. in a mold or will the bag, ply, cloth, resin just drop away from the mold. Thanks, Dan.

[KnottyBuoyz]

Update: Tested out large vac pump with poor results. 16" was all it would give. Lucky for us all we had in it was some labor. Now it's off to Graingers for a pair of 1.5 hp pumps. I kinda had a feeling we were going to end up here. Not to jack the thread but.... has anyone had any kind of luck infusing past 90deg. in a mold or will the bag, ply, cloth, resin just drop away from the mold. Thanks, Dan.
I've read somewhere, can't put my finger on it at the moment, but it was a guy infusing the tumblehome stern on a boat (upright) and it worked no problem, you get the same compressive force from the vacuum at any inclination. So in short, it shouldn't fall away. Laying it all up though, that's a different matter. Might want to get a can of 3M Super 77!!!!

[jim lee]

Bagging at odd angles should be fine. Spraytac the stuff together. I wonder at the 1.5 HP pumps. If you have no leaks, I can't understand why you need such a large pump. If you -do- have leaks, we've found that they cause all sorts of trouble in your laminate.

-jim lee

[13AL]

Jim, our thinking as far as the 1.5hp was the long haul. The price was not that much more. "Bigger is better" sort of? Just a thought. Rick, Thanks for the advice. we're looking forward to giving it a shot. Dan.

[sigurd]

super 77 doesnt foul epoxy? that is great.

[KnottyBuoyz]

super 77 doesnt foul epoxy? that is great.
I've used it a couple of times, only very sparingly. Doesn't seem to have any ill effects on the layup or the flow.

[brokensheer]

I was able to purchase shade cloth from Lowe's hardware for 34 cents a foot, it was 6 feet wide. We infused three 30 foot panels and this worked well.

Pat

Hi Pat, Iwas in Lowes today looking for shade cloth,, the guy had no I dea and we went to a second guy how could not help either I found some nylon mesh in the garden center dept. It was called tree something can ya give me a few more clues, Thanks

[Pat Ross]

Hi,

Here is the link for the product that we used at the Derek Kelsall workshop, it is call Sun Screen Fabric.

http://www.lowes.com/lowes/lkn?action=productList&N=4294961544&Ne=4294967294&Ntk=i_products&Ntt=sun+screen+fabric

I see now it is $.175/foot. Whenever I go to Lowe's or HomeDepot I always go by the outside garden centers. What happens is they discontinue colors or a specific manufacturer, they then put what they have on sale. I buy it then since storage is free at my home till I need it. I would expect with the weather growing cooler that it may go on sale now or soon for example. I buy them out when it does.

I hope this helps you out.

Pat

[Herman]

super 77 doesnt foul epoxy? that is great.

Use it very, very sparingly. If you can see it, you have applied too much. Take a distance of 60 cm or 2 ft from the glass to be sprayed.

And when you do not need it, do not use it. Once vacuum is on, things will not fall apart anymore.

Other options are sprayable hotmelt glue (needs shop air and power, but no VOC's) and there are plenty of other glues that can work. I have also seen plastic staples used (Raptor Composite Nails) which work if there is foam or balsa to tack into. Other proven options are Airtac 2 from Airtech, or their Fusiontack, which can be applied using a plant sprayer or paint gun. (I am worried about the amount of glue used, then)

[Herman]

Sorry about double post, lets make it a useful one:

About vacuum pumps: As long as they draw enough vacuum (between 0,8 and 0,9 bar vacuum for epoxy, or perhaps slightly less for polyester) you are OK. But keep in mind some small things:

-when the pump reaches maximum vacuum, it also reaches 0 air transport. So a bit more maximum level of vacuum helps retaining air transport.

-when buying a large pump, make sure you have a decent sized vacuum vessel (could be a large, abandoned compressor tank) and a pressure switch (Danfoss RT121). This way you can:
control the level of vacuum
have the pump stop when vacuum is reached, which saves your ears, your money, and our planet
have control over leaks. As long as you do not hear the pump running, everything is OK. When it starts running more often, check things.

Make sure the capacity of the pump and the size of the vessel match roughly. That way the pump will run for a nice number of seconds or even a minute, and then will shut up for a considerable amount of time. Too large a pump and it will switch on and off rapidly, not even generating enough RPM, or the other way round, and the pump will run too long which is not a bad thing, but is annoying.

And the last thing: Make sure your pump will always run within capacity: Most oil lubricated vane pumps have an acceptable pressure range of 0,5-0,9 bar. Running it for prolonged amount of time (10 minutes or more) at 0-0,5 bar will clog the oil separation filters, which will make the exhaust of the pump dump considerable amounts of oil, and which is irreversible. (you need to change the filters to get it back in shape again). So whenever you smell oil when a vacuum pump is running, or when things get "cloudy" inside, you know you need to call the nearest service centre for new filters. (installation is usually no big deal, 5 minute job)

[brokensheer]

Hi,

Here is the link for the product that we used at the Derek Kelsall workshop, it is call Sun Screen Fabric.

http://www.lowes.com/lowes/lkn?action=productList&N=4294961544&Ne=4294967294&Ntk=i_products&Ntt=sun+screen+fabric

I see now it is $.175/foot. Whenever I go to Lowe's or HomeDepot I always go by the outside garden centers. What happens is they discontinue colors or a specific manufacturer, they then put what they have on sale. I buy it then since storage is free at my home till I need it. I would expect with the weather growing cooler that it may go on sale now or soon for example. I buy them out when it does.

I hope this helps you out.

Pat

Thanks Pat its a great great help

[AMZ]

I seem to recall a discussion by Andre (forgot the surname, but goes by GRPguru) who said that he would pull a vacuum in the afternoon and go home. If it was still good in the morning, than he had a good bag. Otherwise it was time to identify the fault.
Why this makes sense to me is that besides having a fresh crew for the critical element of the exercise, once the air is pulled and there's no other source for new air, you should be able to leave the stack indefinitely. If there is a leak, it is probably leaving a trail of bubbles reminiscent of the perforations on a magazine subscrition card, and with similar structural characteristics.
Any thoughts on this?

[petereng]

Yes, thats a good approach but... most bags and various consumables have micro leaks and over night can still go down on a perfectly good job. Plus we have found that the longer you leave it the better chance you have of birds and small animals in the factory holing the bag. Even the fibreglass strands can hole the bag if left a long time etc. All bags should have a vacuum gauge in it and if you use a digital gauge you can detect a leak in seconds. If good practice is used all "manufactured leaks" are on the vacuum side of the job so these do not present a problem as long as the pump can cope with the built in leaks. It is impractical to track down all micro leaks although it is possible if you have a couple of days on a big job. When I run infusion trainings I get students to build perfect bags. In fact the first two days of training is just on building good bags. They will hold vacuum for about 3 days before going down. These are small say 1x1m. But try to do this on a 50ft hull job and it is not practical. We've found that the bag quality is very important. Some bag film is micro porous and fine for bagging sandwich panels but impossible to get good vacuum for infusion, similiarly with bag tape. Some are not suitable for infusion. I think the biggest problem in the infusion information is the lack of importance put on getting very good vacuum all over the part. We now use double stage pumps on most jobs. These pull 100x the vacuum a single stage pump does and definitley makes a difference. Can't have too much vacuum! Aussie Guru.

[petereng]

I see that many people "recommend" the use of a vacuum receiver. This is NOT GOOD. You can't store a vacuum like a compressed air system. All you are doing is putting more load on the pump to keep the extra volume pulled down. You need to minimise the vacuum volume not maximise it! Plus you need a pump that is rated for 100% duty cycle. It needs to run for as long as the resin takes to cure. Plus many people say 80-90% vac is OK that is untrue. This means that you have 10-20% air in the job and air is your enemy with infusion. If you let the job cycle, the job volume is changing. Its getting bigger then smaller, thicker then thinner. The laminate needs to be compressed at a constant volume otherwise that 10% of air thats in the bag will end up in your job when it expands. Most single stage oil vane pumps pull 99.0% vac or better. Cheap 2 stage refrigeration pumps pull 99.99% vacuum which is prefered. A 25m3/hr pump will do a 50ft boat if the bag is built right. I do recommend that if you are building this size boat that you use a bigger pump for various reasons but I have done it and it is technically OK. Theoretically once you pull a vacuum in the job you don't need a pump! But the micro leaks will get you so you need a pump to scavenge these as the job progresses. Plus if you are using styrenated resins you get outgassing which decreases the vacuum, so you need the pump to scavenge styrene as well. Aussie Guru

[AndrewK]

I also agree that on larger jobs it is impractical to eliminate all micro leaks and some time impossible. These days I place a tube on to the outlet of the vacuum pump and then the free end into a container with water and check to see how fast its bubbling.
No need for long pressure drop tests its instant indication.
This volume could also be simply measured and then related back to the job volume to establish if it is below an accepted value.

[marshmat]

In one of the physics labs where I used to spend a lot of time, it was frequently necessary to pull 1e-6 to 1e-8 torr vacuum. (ie, on the order of 0.000000004 inches of mercury). At this level, you're no longer worried about leaks- more like, are there any fingerprints in the chamber (fingerprint oils will offgas) or are your hoses themselves porous/offgasing (copper and stainless hoses are often necessary).

By comparison, I don't think I've ever pulled a bagged composite part down below ten torr or so (about 0.01 atmosphere). Although, most of my work with bagged composites has been heat-cured prepregs, where minor leaks are not nearly as critical as they are on an infusion job.

The latter of these two cases is by far harder on the pump. I really take issue with any suggestion of HVAC/refrig vacuum pumps being used to bag a composite part- these pumps are meant to run for 20 minutes at a time, pumping nice clean things like air, refrigerants, maybe a bit of compressor oil. A pump sucking down a bagged composite part is running almost continuously for a day or more, often dealing with styrene and other nasties in the flow.

Beefy old cast iron two-stage pumps, vane or piston, are my favourites.... the old '60s and '70s Welch, etc. that run for decades with little more than an occasional oil change.

Andrew- Bubbling the pump's outflow through oil or water is a clever little trick, I'll have to try that sometime....

[petereng]

Andrews water trick is really good. We've used 2 stage refrigeration pumps for years no problems. Just change the oil regularly and when you buy check its rated at 100% duty cycle. Its not about the absolute vac pressure its about acheiving a good vacuum over the entire part. If you put an electronic vacuum gauge around a part thats pulled down with a single stage pump you will find areas that are at reasonably high pressure. These agree with dry spots. You can let the job pump down for a while but it won't acheive the ultimate pressure of the pump due to the microleaks. Using the deeper vacuum helps in getting the job at as low a pressure as possible. Something most people don't realise is that at these pressures the water vapour in the glass fabric and other materials is flashing off at room temp. Its best to let the bag sit for a while and let the water vapour leave. If you use an electronic pressure gauge you can see this happen. A Normal dial gauge will say 101kPa so its OK? No, put the electronic one on and you can see the bag is still coming down. After say 30mins the bag comes down proper. The only explanation I have is that water is flashing off. As Marshmat says there can be a lot of outgassing from various materials in the bag. These are the invisible enemies of the infusion. By the way if you read the manuals on pulling down HVAC systems you will see that you are supposed to pull them down for a couple of hours to get rid of water vapour and oil and various things in the system. 20 mins is not long enough to produce a clean AC system so is it long enough to produce a 'clean" infusion? Most AC companies claim that most reliablity problems in AC units are from techies who do not hold the vacuum long enough when setting up the system. Like most people they are in a hurry and if the meter gets to 100micron then thats OK lets fill her up! Peter

[AndrewK]

While you can perform infusions at lower vacuum levels as Peter said there is a lot of moisture in the reinforcements ( especially in humid locations like Brisbane) that can only be removed with a very high vacuum pump.
I think this is one of the pluses with infusion, no other method will allow you to remove this moisture. But having said that even with a two stage pump on a medium sized job ( 12 x 2.5m) it can still take a very long time to dry the reinforcement completely.
The trick I have used is to periodically introduce some air from my scuba diving cylinder ( this is very dry air) into the job to aid with the flushing out of the moisture. An alternative would be to prepare a large bag, blow it up and place some desiccant in it the day before. Then use this dry air to help with flushing the water out of the job.

The only down side with very high vacuum is that even epoxy resin can start to boil, not just the initial de-gassing of dissolved and mixed in air.

[Herman]

Beefy old cast iron two-stage pumps, vane or piston, are my favourites.... the old '60s and '70s Welch, etc. that run for decades with little more than an occasional oil change.


I had a Welch for some time. A 1394 model I believe. A notice, riveted to the pump said:

"kindly oil every 10 years".

Modern pumps should have the same notice: "throw away every 10 years" :)

----
Dry materials are a good thing. Some builders over here store their materials in an oven at 70 degrees C, before using them (wet layup or infusion).
Both epoxy and polyester resins do not like moisture. I suggest doing a small test with epoxy resin: add 5% water, which you can mix in even without getting a cloudy appearance, and cure it with a slow hardener. Use a batch of 1/2 kg or so. After doing the test, let me know what you think...