Infusion related - will this idea work?

[Wynand N]

Got a 115 liter cylinder today and will start the modification as soon as I have time on hand and hopefully do a test this afternoon to see if the "vacuum booster" will work or not.

Andrew, the polyester resin I use is a NCS 301 PA LSE, an isopthalic NPG (new penthol glycol) low viscosity type - much thinner than GP polyester resin and has high waterproof and chemical resistance properties.

The viscosity is fine as is evident in the layups I had experimented on - the last drystack consisted of 3 x 450g CSM, 2 x 2mm Coremat and 2 x 610g WR and it went through that reasonable well but my enemy is the gel time. In my part of the woods the heat is in the high thirties/early forties C in the workshop and a less than perfect vacuum due to high altitude which I must do battle with.

However, I spoke to my fibreglass pimp this morning and was told he has a slow gel catalyst that in effect doubles the gel time. He has all the potions to thin out my resin should I need that, but if the gel time is doubled with the new catalyst he is sending, I would prefer to keep the resin "intact" for obvious reasons.

[Wynand N]

And my question has been answered.

I has set up the test bench with two identical sized drystacks consisting of 2 x 450g CSM, 2 x 610g WR, 1 x 2mm CoreMat and surface tissue.

The drystack with pump only was hooked up to the 6cfm JB Ellimanator and pulled a vacuum of 87kpa.

The cylinder driven unit was hooked to the old Edwards pump and due to the age of the pump, only got an 82kpa vacuum in the cylinder.

Each stack had its own vacuum pipe to its own unit and individual resin feed lines. The resin was catalyst in a single container and then split in two smaller containers to keep things even. At this stage I must confess that I had a leak on the cylinder assisted stack we could not get closed that may have a slight influence on the result.

The photos tell the story. The feed lines were opened at exactly the same time and at the end it was a close call with the cylinder ahead by a very small margin. Cigars to some and well, it was worth a try to myself and others. As the saying goes; nothing ventured, nothing gained

Was all this a waste of time and greenbacks?
In short, no. This experiment showed me that the cylinder in a full state of vacuum, can be a valuable backup unit in the event of losing a pump, or electricity break - just switch a valve and one is safe for quite a while to get another pump started, or the generator going.
I am going to build a compact vacuum station on a steel platform with caster wheels so it is movable - will have the JB and the Edward pumps fitted permanently to a manifold system that is hooked to the "storage cylinder" and the resin trap fitted as well. From the system just one pipe going out that pulls the vacuum.
In this setup I can change to any pump at any moment, or just suck with the cylinder (excellent idea for smaller parts - no noise) or all units and cylinder together.
Will post photo of the setup when sorted out and build. The little Gast pump will be kept as a backup to the main system.

[MarboMan]

"Each stack had its own vacuum pipe to its own unit and individual resin feed lines."

You can get a "bag" fitting from Air Tech and try pulling the vacuum from the center of the stack and have resin feeds at each end and put a resin trap before the pump so it doesn't inhale resin.

[TeddyDiver]

Nice work W..

[AndrewK]

Wynand,
When new to infusion no experiment is a waste of time, as discussed the large tank will be good for the initial pull down, finding leaks with no pump noise and as you say good reserve of vacuum if you lose power.
The slower hardener will make a big difference and hopefully at no extra cost. From here on all other improvements to speed things up will cost more, directly in materials or through wasting more resin or both eg more of and bigger bore tubing.
Is the new hardener the same Fanie used for his beams?
Do you know what the resin viscosity is? can your pimp find out? It would be nice to know what you are dealing with.
I imagine even a 5% addition of styrene would give a large reduction in viscosity.

Have you determined how much the coremat is being compressed, my thinking is that it may not be adding much thickness to your laminate and therefore waste of material.
For comparison the data sheet for the infusion grade states that it loses 10% at 80% vacuum.

Another experiment I suggest you do is to make your maximum thickness laminate to make sure there are no excessive exotherm issues.

Also now that you have a number of test laminates it would be good to do a simple test and see how much stiffness is being lost with infusion compared to open lay up.
Say cut a 50mm x 600 strip of each laminate and clamp to a table so that you have 500mm overhanging. Hang weights on the edge and measure displacement.

Cheers
Andrew

[Wynand N]

Andrew,
Fanie is using a different resin altogether, but from the same manufacturer. I traveled today to my fibreglass today and he gave me a liter styrene to experiment with and recommends I start with 2% and work my way up to a max of 7%.
I also got a new catalyst from him that doubles the gel time and I did a test with a little resin with the standard hardener and the new stuff and the gel time is stretched to nearly double - that may help considerably.

The data of the resin I use as per spec sheet is;
Viscosity @ 25°C, mPa.s 200 - 300

[AndrewK]

Wynand,
200 - 300 mPaS @25'C is good, in your case the lower it is the better.
At the moment while your workshop is at 35'C actual viscosity would be a lot lower.
A few more suggestions for you, when doing the trial always record temperature, vacuum (in the bag), plumbing layout and distance resin travels per minute. You will find this very valuable when planning new infusions.
There is a big difference between 200 & 300 mPas, if your resin supply is inconsistent and if you have a ford cup for measuring paint viscosity it may pay to check what the flow time is for your current batch of resin. This can be then used as a reference point for future batches, and if they are higher in viscosity you can make adjustments for this.
So far you have also done your trials with the inlet at one end vacuum at opposite end, do your next few with the feed line in the middle and vacuum lines at either end so the resin travels in both directions. On larger jobs you will be using a combination of both so you need to know the behavior of both feed systems.

Cheers
Andrew

[jim lee]

Wynand, If I read this right, your infusing chop strand mat and woven roving? If this is so, a better experiment would be trying a stack of biax with infusion core.

I -think- that with the material you are using, the flow rate is so slow you will not see the benefit to your tank idea. With the correct materials I'm betting your going to see a much faster flow rate.

Good luck!

-jim lee