A Bad Infusion - What Would You do?? (Pictures inside!)

I've been having a tough week in the boat shop. One of the main problems was that I had a bad infusion. My hull infusion (even with lower vacuum and visible leaks) came out fine because any air in the infusion moved up to the flow media, leaving the laminate perfect, as you can see in this picture:


HULL INFUSION RESULT

I am now infusing flat panels (beams) on the glassing table and finding that the quality isn't there.

I had a full 30" (highest the gauge can read!) vacuum, but ended up with some slightly dry spots both on the top surface and bottom surface, as well as at the resin feed line along one edge! You can see that dry glass where the feed tube was if you look closely along what is the bottom edge of the beam in the first picture of the closeups (further down the post) and also in the last picture of the closeups.

There were no audible leaks with the ultrasonic leak detector even on 100x amplification. Somehow, some air got in the feed tube, I think. Both sides were infused at one time, laying flat on the glassing table.

The result was this:


NOTICE DRY AREA AT BOTTOM OF PICTURE

ON ONE SIDE, THERE ARE BITS OF AIR COMING THROUGH THE PERFORATED FOAM

ON THE OTHER SIDE, THERE IS MORE AIR IN GENERAL

ANOTHER ANGLE - THIS ANGLE MAKES IT LOOK WORSE. PICTURE ABOVE THIS ONE IS MORE ACCURATE.

This beam is part of the aft beam. Its purpose, structurally, is to create a box to prevent the aft most beam (absolute transom where catamarans paint their name and hailing port from twisting. It is like a large stiffener.

The laminate schedule on each side is 2 layers of 34oz triax (1150g), 2 layers of 9oz uni, about a foot wide, running along the top and bottom edges.

It is attached to the aft most beam through a couple of internal mini-bulkheads inside the box and of course, the top and bottom of the box are also glassed in and all is tabbed together with long strips of biaxial tape.

Here is a picture of where this part of the beam sits in the boat. It does *not* travel into the hulls and there is a rather large cutout in it for the berths you see sticking up on to the bridgedeck in this picture:


BEAM CIRCLED IN RED IS THE PROBLEM. IT ACTS AS A BOX WITH THE MOST IMPORTANT AFT BEAM TO PREVENT TWIST>

Questions:

1. Is this beam going to be safe with these lamination issues?
2. At $88/gal for infusion epoxy and/or $6000+ for the little drum kit, I feel like this quality is not up to what I am paying. Any thoughts?
3. Can the beam be fixed?
4. Does the beam even need to be fixed?
5. Would you infuse the 2 other crucial beams, or... would you hand laminate them? It may be nearly impossible to hand laminate the main beam due to the number of layers of uni all over it, including a stagger of layers directly under the mast.
6. What would you do in general? How would you proceed?

 

Could you not just wet out the dry part of the surface of the panal while laying flat using a hard heavy roller (like they roll over linoleum floors to get air bubbles out.) with thin epoxy? Or am I missing something?

 

You're missing something.

It's infused, so the "dry" spot isn't really dry at all. It's solid if you whack at it or try to pry strands of glass apart with a screw driver.

Basically, on a microscopic level, there are small air bubbles within the fibers of the glass and possibly between the glass and the foam. These are not entirely open to the top layer, so you can't just drop more resin in from the top. The air is within the laminate, evenly distributed.

The glass a lot like when you don't quite wet out a hand lamination enough, but it's still wet out enough to all stick together properly.

The beam is able to be picked up and moved with no flex by holding each end and laying the beam flat as you carry it and it's rock solid. It's more a question of what will happen at sea under large dynamic loads in a storm or something.

Also, the pictures do make it look worse than it really is. They pick up the dulling out of the dry more than the see through of the good stuff for some reason.

 

OK, I was missing the point and you explaned it well now I understand. You have air
pockets within the panal taking up space thus weaking the panal and no way of removing them or filling them with a hollow needle. we know air pockets weaken the panal but do we know by how much or what factor? Could you hand lay a light additional covering over the panal using Bi or Tri in say an 8 once cloth to make up for the weakness? What % of the panal do you feel is dry? 5%--10%--1 %. There must be some math to determine a strength factor of one more layer. However, that is above me. You might consider S-2 glass. I've got to really hand to you taking on a job this big and this complex. Looks like your doing a great job and I compliment you and glad your sharing it with us. I feel that the panal can easily be saved and strengthened W/O to much effort or money. Can you ask whomever did your laminate schedule if this would work?

 

Maybe you can re-use it in another place. Can you salvage the bad beam and re-use it for cabinets or something similar and just try again with new material rather than take a chance on failure at sea if injection filling isn't possible? Or will that glass make that too much a pain in the arshe?

 

Another thought. If you can see and mark the dry areas out put a 6,8,12" tape across those areas like an additional laminate one side or both to repell any forces that might act on those areas.

 

The real strength is in the glass more than the epoxy so maybe the problem is more cosmetic than anything.
Maybe strength is not compromised? I'm waiting to be corrected here.

 

I agree with you there Hoyt. Also, my experience in engineering beams and connections
is that they are at least 20% over engineered. I do not know if laminates are done that way. We have some very knowledgable N.A.s here who could answer that question.

 

I do know my designer designs his beams with a safety factor between 4 and 6, so 400% to 600% more than needed on the beams. I may be able to use it elsewhere though. Looks like it would make a nice (though heavy!) table.

Would love to hear what some of those infusion experts here think of the quality, too.

My concern with extra patching is that it does nothing to address the real problem: Possible poor adhesion to the core. I think the glass would be fine, since it's a lot of Uni where the problem is. However, if there is some peeling effect and something that is not well stuck starts to spread, my beam will unravel. Or maybe I'm just being paranoid. I just don't have the experience to know.

 

I dont know much about infusion (anything? ) but I do know that I wouldnt risk using something that MAY be sub standard on a major structural part of a multihull such as the beams.

Hopefully it ends up being ok

DAVE

ps much credit to you for building such a impressive cat,

 

My area of expertise is not laminates... but in general, I agree with Hoyt.

If I had any concern about inadequate safety factor, I'd make a test shape using your current process and destructively test it against the engineers expectations.

If the test panel meets the expectations, then the issue is primarily cosmetic.

 

The problem with dry laminates is the the adhesion to the core is poor and it will fail in compression at a much lower load.

 

My first few infusions looked the same Cat... im 100% sure it didnt have any leaks, i dont think its air in there either.... i thinks its simply a dry laminate whereby the vacuum was so strong the fibres do not get fully wetted out due to the high compression from the vacuum. So the white colour is just the glass fibres, not air.

As to the strength, id guesstimate that it would be ok - but thats hardly reassuring is it!!

Going forward, i would try reducing the vacuum pressure to around 26" give or take... and make smaller test panels first when you're working with different laminate thicknesses, core materials and resins before jumping straight into an important part such as a large beam...

my first infusion was with a vinyl ester resin and i had so much vacuum the resin was boiling off... live and learn...

 

Email the designer and supplier???

 

It's best to repair.. grind the worst places first to see if there's some bonding issues, set new GF and hand laminate over.. I have had sometimes dry spots or air pockets (in hand laminates) and there's only one option.. repair IMHO