Infusion General Problems - Needs It's Own Thread

[CatBuilder]

Thank you very much for the comments, everyone.

Idkfa: I did precisely that with a layer of bog that meets the tape. That is what got me from 10.5 to 17.5. It is a good idea and i may try it next time. The microscopic holes do only run 10's of cms at most.

Random thought this morning upon waking:

What is the difference between laminating by hand, then putting a bag on where you achieve 20" Hg because of a leak and an infusion where you reach 20"Hg due to the same leak? It would seem the leak would have the same effect on the laminate in both cases, correct?

In both cases you have wet out glass that has some air admitted into the bag. Really hard to see why plain bagging is accepting of small leaks when infusing would not be. They are essentially the same thing, once you are done flowing your resin.

[CatBuilder]

Got up to 20 and went for it. There were a few leaks to take care of during the infusion, but it went off well. Babysitting the pump now through the night and most of tomorrow, probably since it's not very warm out.

Oddly, it was my best infusion ever.

[rasorinc]

CAT, I have been reading you plight with infusion and saying to myself (don't ever infuse anything). You have taken on a huge project and the pictures drove that home to me. Wow, you got more fortitude and drive then I have and I'm just cutting frames for a 9" x 30" cruser. I know nothing about infusion but a thought popped into my head.
Is there a tool to infuse the opposite side of those huge hulls with injection pressure using something like air injected shots in the arm? (usmc) Would something like this be of value and would it work like like a vacumn? Just a thought that may have no value. However, in the pics I was very pleased to see something of value I suggested was being used. I'm the guy who suggested a strongback to turn those large hulls as a poor mans beam and Hoyt drew it out. So, I wish you all the success in the world in your endevor--you got more guts than I in taking on such a large project. You will do fine, all the luck in the world to you.

[CatBuilder]

Rasor, thanks for those kind words and for that strongback idea!! That idea saved my whole project. That's the very same beam in the foreground getting ready to life another half a hull out of the mold. Those are some temporary bulkheads attached to it (with straps for safety), which are bogged to the peel ply on the inside of the hull.

As soon as I pull that half that's rigged up to pull, I'm on to the last half of the last hull. Pretty exciting times.

Infusion is actually a great thing, when you are infusing two sides at once. The best infusions are the ones where you can get your entire part into a bag. The only leaks you have then are ones you make yourself by puncturing the bag or doing a bad job on the sealant tape. Not too hard to chase down. I don't recommend against infusion. In fact, I'll be using it for my cross beams (main strucrural components of the catamaran) and for other flat panels like the bridgedeck and deck house top and sides. With those, I can get a bag around both sides of the flat panel and do both sides all at once.

What is difficult is trying to infuse just one side of a part and getting the other side to be somewhere close to air tight.

I take on this project because I have to. My charter business needs a new charter boat and we want to run a catamaran. I can't afford a catamaran like this, so... you know the rest of that story!

Again, thanks for that kind post.

[CatBuilder]

Rasor: I dreamed up the same tool last night! Sort of like a carpet steamer, but to inject resin way down under the laminate at high pressure.

[Herman]

There are RTM machines, that mix resin and inject it under pressure. Most simple version is a pressure pot, more advanced units can sometimes be picked up 2nd hand cheaply. Mostly need refurbishing though, but all can be done. (they are relatively simple machines.)

How is your laminate quality? Still OK?

As for laminating by hand then bagging (wet bagging) vs infusion.
With a leaky surface you get the same problems. The only difference is that leaks in the bag have less effect. (but these can usually be traced quite simply, and repaired)

[CatBuilder]

I am not sure about the laminate quality yet, since the hull is still under vacuum. By looking through the bag, it was my best infusion yet. I had not a single dry spot to correct during the infusion. It went from feed lines to vacuum line without any problem and without skipping any areas.

The pump is still on because it got cold 50F (10C) last night. By noon today, it should be kicked off enough to turn off the vacuum pump.

[AndrewK]

Catbuilder; I am not qualified to answer your question is it OK to wet out from above the porous laminate due to air tracking, secondly you need to see it live to make a judgment call as to how bad the degradation is.
One person you can try is "petereng" from BD, he is a composite engineer and also involved with infusion.

Personally if I was only getting 25" vacuum with a 29+ pump I would not have gone ahead, I would have hand laminated.
My reason for this is this, a good hand laminating job at 50%wt resin will have 3% or so void content and is a very good laminate. Infused laminate done under full vacuum will have 0.5% void content and 30%wt resin. The infused laminate is stronger and stiffer due to the lower void content and better fiber to resin coupling as well as the tighter bunching of the fibers means that they better cooperate with each other.
If you have a leak and drag air through a localized area I guess you can end up with a void content as high as 15%??? in that area, this means that the fibers are not very well supported and will not cooperate well with each other.
Painting over or infusing this area with more resin say 24hrs later will make things better but by how much? The fiber tows would have been shiny smooth so there is no way of getting a good key with the fresh resin.

Your second question regarding the damage done by the same leak on a bagged versus infusion job, is it the same?

Yes and No, depends on where the leak was.
If it was in the middle of the job and coming trough the bottom laminate then the damage will be the same.
But in most cases the leaks do not come through the bottom but around the perimeter or the bag film. In these situations the bagging job has an advantage for these reasons.
1. bagging vacuum is mostly <80%, meaning lower pressure differential so less air entering.
2. the breather/bleeder fabric will be larger than the lamination, this means that you effectively have a low resistance path right around the perimeter of the laminate for the side entering air to be taken care off especially if you have a perimeter vacuum line.

So while the damage with vacuum bagging will be less in many cases infusion has one very big advantage, you know if you have leaks prior to mixing your resin.


Additionally regarding airtightness of single sided infusions, I have not found this to be a problem, on one job I did not even have a backing laminate.
What I do is either put on a 5cm wide strip of soft bog or resin and peel ply on to the bare foam and seal the bag onto this, the inboard edge of the 5cm.
I also almost always center feed the resin even on vertical jobs so that I can have a vacuum line on both of the long sides, side benefit to this is that the infusion job is also quicker.
I also have a couple of spare 1/4" cheap micro irrigation tubing lines connected to the vacuum pot. On the ends of these I have small suction cups fitted that also hold a small nail. If you notice a leak (air tracking) and can not find the source to seal then I seal the suction cup over the position where the air appears to be entering. Then press down the cup and the small nail punctures the bag, this new vacuum source will minimize the damage to a very small area.
I also use the suction cup lines also to fix dry spots, where resin flows around a patch
leaving an island of dry cloth. The new vacuum point will draw the resin into the spot, once filled it can be clamped off.

[hoytedow]

It's supposed to go up to 80 F here today.