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

[AndrewK]

Originally Posted by CatBuilder

I had a vacuum pump failure and had to switch the pump out mid-infusion.
The positive to this is that it was a simple equipment failure that caused the poor laminate, you should have mentioned this. Disregard my comments about mixed in air and off gassing.

I had dirty oil in the pump (milky white, actually) and I think it wasn't able to pull the full volume it normally does (6CFM), although it was pulling down to full vacuum.
This is water being removed from the laminate.

ANDREW: The holes in the foam were as ordered from Divinycell. This foam is Divinycell H100, perforated. I believe it is 6cm spacing, but I am not recalling perfectly. There was one difference in flow rates between top and bottom, but it was just the opposite. In one part (a part that came out very well), the top lagged behind the bottom. It worked that at times resin came up through the holes before the resin advance line on top made it to the same area. This only happened in one area, but that area came out well. Also, I use a resin stop (stop the flow media/mesh 2" from the vacuum tube) to allow faster and slower areas to catch up to each other. This worked as well as it normally does and allowed that slower top to catch up to the rest of the infusion.
That perforation spacing while it works as you demonstrated is not ideal for infusion. For infusion many small holes is better, Diab also have hole spacing at 20mm spacing for infusion.

For degassing, I normally run the pump at full vacuum for about 30 minutes to an hour before starting the infusion process. Is this enough time?
The degassing I was refering to is the degassing of your mixed resin to get rid of mixed in air and dissolved gasses. This is not necessary, but it does improve the laminate quality.
Pull down time of 30 - 60 minutes, is it enough? yes for smaller parts on the table that were asembled in low humidity. The milky oil is a teltale sign of moisture in your laminate, in these circumstances I dont mix the resin untill the oil has cleared.


If I looked at fixing this beam (preferable), what would the repair joint look like?
You grind away all of the non translucent dry laminate and replace it with the same schedule overlaping onto the good base laminate. Looking at the picture it may be easier just to cut the section with the additional UD right off, remake this and tape together. Use the offcut for steps going down into the hulls.

Has Kurt looked at the pictures?

[CatBuilder]

Steps are a great possible use for an off cut.

I also think I spent too much time on the computer on this problem, since going out today to work, I am looking at the beam and wondering why it doesn't look as bad as before.

The camera really made it look about 3x as bad as it really is.

I am not sure if Kurt has seen this thread. You don't get many questions per month with Kurt, so I need to save them for design related questions. This is more of a building related question.

I think I need to take a step back and do what P Flados suggested. Really take a look at what I do have and how strong it is. I was thinking of driving my sprinter van up on the panel to see what happens.

[AndrewK]

Problem is how do you relate the Sprinter van load to sailing loads. Personally if I could not get Kurt's opinion I would remake the part.
To make you feel better I remade my mast beam as the first one was degraded when a leak developed through the tape seal at some stage after I did the infusion. In this case I only had the vacuum line on one side and of course the leak was on the opposite side, ever since then I center feed the resin with vacuum lines on either side.

[CatBuilder]

I suppose you really can't know how to relate a Sprinter RV (caravan) conversion load to dynamic wave loads. The Sprinter can really only test deflection loads, which, I think, would be the most likely to propagate a delamination, if one is possible.

One thing I do know is my Sprinter conversion weighs 3.25 tons. Considering my entire boat is supposed to weigh in at 9 tons filled with toys, food, fuel, people, etc... etc... , I am guessing that the load on a stiffener attached to the main aft bulkhead/beam is going to be less than 3.25 tons. Also, the load will be, as P Flados was saying, in plane with the beam, more or less. In fact, that's what this part is for. it takes up the out of plane loads from the real aft beam. If I do a 3.25 ton 90 degree out of plane load on this part and it doesn't delaminate (or snap in half), I think I will keep it. I would load it up with the bad side taking the compression load and the good side taking the tension load. That way, it is more likely to delaminate.

Remember... this part acts as a stiffener for the more heavily laminated and stronger aft most beam/bulkhead that goes from hull to hull. This stiffener has cut outs in it for berths can access doors and doesn't even continue into the hulls. it just sits up on the bridgedeck, keeping the real load carrier straight.

Well, still deciding...

[waikikin]

Originally Posted by AndrewK

Problem is how do you relate the Sprinter van load to sailing loads. Personally if I could not get Kurt's opinion I would remake the part.
To make you feel better I remade my mast beam as the first one was degraded when a leak developed through the tape seal at some stage after I did the infusion. In this case I only had the vacuum line on one side and of course the leak was on the opposite side, ever since then I center feed the resin with vacuum lines on either side.

I concur,

your connective structure is no place to have concerns on, use the panel for something less critical like a sole or hatch panels- how much does it weigh - x $ per kilogram.. don't spoil the ship for ha'penny o tar etc.

[Herman]

Indeed, Either fix it, or discard (reuse) it. When sailing in hairy conditions, you do not want to remember this piece.

I am also thinking humid materials might be part of the cause. (in combination with the milky oil).

You did change the oil on the bad pump, did you? Also let the pump run for a couple of hours, to get it hot and repel the remaining water which might be in the pump.

Next part leave the vacuum on for a night or so, to get rid of the water. Keep an eye on the vacuum gauge, water cooks at 20 mbar or so. If the gauge stops there, it might be water boiling off. Preferably use a gauge which reads absolute pressure.

[CatBuilder]

I agree with you guys.

I was giving this some more thought today and I cannot live with a questionable aft beam.

I will make a new one.

This man inside me got the upper hand for a few moments when I was tired at the end of last week!




I will just save this part and put it aside, using it for steps or any number of a hundred other uses that are possible when you are still in this early stage of building a catamaran.

There is no need to take any risk at all given that there are so many other uses for the panel.

Thanks for the input. If there's one thing I've learned doing this build, it's that Andrew and Herman are seldom incorrect.

Herman: It was my own fault. I left the same oil in that compressor for a very long time and even saw it was milky white on another infusion before this one. It didn't affect the pump performance on the previous infusion and since this was such a small part, I figured I'd just go one more time without changing the oil. Bad mistake.

My vacuum hit 20+ mbar (just about 30" Hg) within a minute of starting the pump, including bag pump down. Half way through the infusion, it just started going slower and slower... and ... slower...

All my complaints about leaks before in other threads were due to hull leaks, through the hull, bagging one side only. For this infusion, I had a bag around the entire part, so no leaks. Very refreshing!

I will keep the vacuum on longer to get rid of the water next time. I had thought 1 hour was enough. Thanks for the tips.

[hoytedow]

Originally Posted by Herman

Indeed, Either fix it, or discard (reuse) it. When sailing in hairy conditions, you do not want to remember this piece.

I am also thinking humid materials might be part of the cause. (in combination with the milky oil).

You did change the oil on the bad pump, did you? Also let the pump run for a couple of hours, to get it hot and repel the remaining water which might be in the pump.

Next part leave the vacuum on for a night or so, to get rid of the water. Keep an eye on the vacuum gauge, water cooks at 20 mbar or so. If the gauge stops there, it might be water boiling off. Preferably use a gauge which reads absolute pressure.

The oil is not lost. Get a Fry Daddy for under $20 and use it to crack (distill) the water from the oil. Watch it until oil goes clear and un-plug it.

[themanshed]

On a smaller scale I vacuumed bagged some bulkheads - 2 skins to foam on each side in one session on a table. When it dried it looked like I had a bad lay-up not air bubbles but rather it did not look like I did not have good saturation as if I pulled to much epoxy during the bagging. Again the light color looks much like what your picture shows. After the cure I pried and pulled on the skins and they came off. I re-made the pieces. In your case it is much larger piece - but in cost a failure is a failure. Always seek the advice of your NA but I say be prepared to at minimum to remove the section of bad laminate and replace it. I think you question is it time and cost effective to repair or remold.