Infusion General Problems - Needs It's Own Thread

Since you were able to infuse the first side successfully this means the foam itself was air tight. So the leaks should be located along the sealing edge, plastic film or if you drilled a hole somewhere to hold a bulkhead in place perhaps and forgot about it.

 

The leaks are through the "already infused" part of the hull, right in the infused glass surface. It is pulling air through the "already infused" part, under the tape sealant and along any core gaps or air passages.

I am infusing the rest of the exterior of the hull. The other infusion on this hull was done on the other half of the exterior, while it was at rest in the mold/form. It is attaching a bag sealant tape seam to the "already infused" part of the hull that is causing the problems.

The "already infused" part leaks air because it's a drier layup than hand laminating. So, there are some small gaps and pinholes in various places where it would have had a more airtight seal to the core if hand laminated.

 

The news is, I was able to get to 17.5 inHg after the painted epoxy on the porous "already infused" part kicked.

Now, there are some new holes in the bag from me hitting it while painting the epoxy on, but I feel confident I'll be able to get her up to about 20 in Hg, which is good enough with a 6CFM pump and a 45+ hull that is also about a 12' infusion length up to the keel from the starting point at the deck (boat is upside down).

Should be FINALLY completing this infusion tomorrow.

 

Good going Cat.

 

If you are pulling air through the adjoining infused external laminate then you must have had air leaks during the first infusion. Infusion does not produce dry laminates, its air leaks that flush out resin while its gelling.
Personally I would never infuse unless I get full pump vacuum, if you can not achieve this then better to hand laminate.

 

Yes, you are correct, Andrew. That is exactly what happened. The laminate has some very small air tunnels in the outer skin laminate because when infusing one side of a core, you cannot get all leaks out. It's not even possible.

I'm not sure I've ever known anyone to achieve full pump vacuum on infusion. Is that what you did? You achieved 29+ in Hg? Thats is very impressive. I have never been able to do that on a full hull, nor known anyone who has. I only know 6 people who have infused hulls, yourself included.

Most people suggest 25+ in Hg as a good place to infuse and your panel will be fine.

 

I use a 5cfm two stage pump and get 29+ vacuum.
25" vacuum is fine if thats the pump capacity, but not if its a 29" pump not being able to keep up with the air leaks.
I mentioned it before I only had a problem once trying to get a full vacuum, spent two days trying to locate the leak. It was where I put a screw from the outside to hold a bulkhead in place. What happened is that I was not able to settle this b/h on top of bog but instead I beveled the edges and squeezed the bog into this, obviously a channel still remained along the b/h edge. Unfortunately when trying to do the outer infusion I was not able to get back to this inner area to seal off this channel.
In my case this was at one end of the hull so I lifted the bag and hand laminated two strips of glass. The next day I resealed the bag on to this and got full vacuum.
Can you do something similar, is the downgraded laminate concentrated only in one area?

 

If you are thinking of taking the risk and infusing at < full pump vacuum then I would only do so if you have a vacuum line around the parameter of the job. This way the entering air coming from your porous adjoining laminate will at least not be tracking through your infusion job. But remember you will have a reduced driving pressure that will make the infusion slower.

 

Unfortunately, it's the the hull laminate is like a microscopic "Swiss cheese."

It is night right now, so I don't know where the leaks are now that I am up to 17.5". I will start in the morning, checking the whole bag again, as well as inside the hull on maximum sensitivity of the ultrasonic leak detector.

I have not ever been able to achieve 29" vacuum on any part that is bagged on one side of the core only. I had 20"+ on the last hull section, which had a few localized dry spots I wet out after the infusion, as well as some of that bubbling you speak of that had to be wet out after the infusion. That is the section I am now having trouble with because it is leaking.

Other builders I know did the same (wet out dry spots from above later if they happened).

Isn't this OK? I mean, you can't get a perfect vacuum on just the outer half of the laminate. Well, I can't anyway.

Please respond if you can. I plan to shoot the hull tomorrow and do not want to wreck it. The other side that has a few dry streaks fixed up nicely wetting then out from the outside after the bag came off. Is this not acceptable?

It is literally impossible for me to get a perfect seal on my hulls. They always leak to some extent.

Answering your 2nd post...

I may infuse if I hit 20Hg just like last time. I know it will create some less than ideal spots, but I can wet those out from the top, after the infusion, right? I have a vac line at the keel with resin feed lines on the deck and part way down the other side of the hull (hull is inverted right now). Vac line is at the top. I also have Enka flow channels, so infusion time isn't an issue at all. I can always get a hull done in under 2 hours. The only distance the resin has to travel is the 18" between flow channels and then up the flow channels. it does this very quickly. It is as fast as I can mix resin in large buckets. I usually stop my infusion with a valve momentarily to catch up.



But are the dry spots or "less than fully wet out" spots really a big problem? Is it fine to wet them out from above later?

 

Why are there so few people on this forum who know infusion? I could use a second, third and fourth opinion here...

 

I am no expert on infusion, but I am not surprised at your frustration.

Chasing leaks may be a pain, but think of how much effort & cost the whole project will take.

More experience can lead to more efficient methods of avoiding many of the problems you have to deal with. If you are not experienced, you really do need to slow down, take a deep breath, be careful, and do what it takes to do it right.

If this was a 2 meter model, your risk would be low. It is not.

Do not despair, and keep plugging away. You will have much satisfaction when you succeed.

 

I am a student here. Can only absorb knowledge this thread and think about chewing a lot of gum for emergency patches.

 

Why?, from my perspective, infusion looks & sounds like a fabulous process & I plan on doing a small settee/engine box with it for a customer- but at my risk as I've not done much of it(In the Lab at FGI & a couple of void repairs) if the settee goes pear shaped it isn't much material etc to remold by "bucket & brush". However with 30 + years in the marine industry what I've been seeing as infusion "acceptable" laminates often don't look like the the neat & tidy job I was trained in & learned some time ago(I have seen excellent results also), I know what can be achieved by other methods at low cost in consumables where as infusion can come at the loss of whole laminates(as can "open molding") plus the cost of bagging & peelply, mesh, piping & fittings etc. I am willing to learn the process but will "sneak up" on it as cant afford a biggish F up, I'm loving your build posts as I reckon your going pretty good & a pretty "ballsy effort. All the best from Jeff.
Ps I'm not giving another opinion- just a perspective.

 

Infusion of a high quality laminate is all about vacuum integrity, as you discovered. I have done large infusions at full pump capacity (ranging from 0,15 bar abs, which translates into some 25" Hg or so, to about near absolute vacuum (0,01 bar abs).

the latter actually can provide new issues with residual water boiling off, so when reaching such a vacuum, I recommend throttling back the vacuum after the infusion, to some 0,05 bar, which is well above the boiling point of water at RT. Also the "springback" of the laminate is not such that it will be a problem.

However, all these infusions were done in high quality moulds or similar (glass or steel sheets)

In your case the problem is not a seemingly untracable leak, but porosity over a larger area.

In the case of an "untracable leak" you can start the infusion, and as soon as you see the leak bubbling in your resin, fix the leak then. If it cannot be fixed for whatever reason, install an extra vacuum point at the leak, so the leak does not destroy much of the surrounding laminate. The laminate that might be destroyed will be just a small patch, which can be repaired later.

In the case of a larger field of porosity, you can either choose to roll a couple of layers of epoxy onto the porosity, or apply a fabric over the area, carefully hand laminating, so the layer will not be porous.

This is why mostly I recommend to hand laminate the outer skin, which is fairly easy to do without making a mess of the workshop or yourself, and infuse the inner skin (inner skins tend to be a pig when hand laminating). The hand laminated outer skin should be well enough free of porosity to do a succesful infusion on the inside. The foam is not critical re. air leaks, it is not "part of the equation". Eventual voids in the foam (messed up glue lines) will all be filled with resin. Same for woodcore.

In your case spend your time chasing leaks before the infusion, and fix whatever you can.

[anecdote mode on]
In one case during leak testing we discovered a leak in the mould, which could only be fixed from the laminate side. We were able to locate the leak with an ultrasonic leak detector. To repair the leak the mould looked like an operating theatre, cutting back the vacuum film, runners, infusion mesh, carbon, removed the foam, again carbon, before we reached the mould surface, which we were able to repair. Then the fun started to get things back in place, beginning with mould release, then carefully patching things up. The infusion afterwards went perfectly, and although a day of work was lost, it was the result that counted.
[anecdote mode off]

 

"Unfortunately, it's the the hull laminate is like a microscopic "Swiss cheese."

Maybe each hole does run very long, a few cm, how about making a larger seam line, with maybe spray adhesive and wrinkle-free laying the plastic film on?

best of luck,