Diesel in fiberglass

[yno]

Hello,

I suspect I might have parts of my fiberglass hull soaked with diesel. Although it is still unclear to me how exacly it got there, and if it did at all, the fact is that I had diesel sitting in the bilge for several months (away from the boat, couldnt check regularly), and there are strains on the outside. It feels oily to the touch, hence my assumption of it being diesel.

I peeled the gelcoat a year ago in an attempt to dry any moisture and left the boat outside. Other parts being affected by this phenomenon are a couple of holes where thruhulls used to be, although from the inside I hardly see any way for the diesel to get there, so maybe it is just water (but feels oily as well, weird).

Although I dont know whether diesel compromises the mechanical properties of the fiberglass (a study performed on aircraft fuels has found very little strengh loss, but wasnt performed with diesel Influence of Fuel Absorption on the Mechanical Properties of Glass-Fiber-Reinforced Epoxy Laminates ), I am pretty sure it prevents any barrier coat or extra layers of laminate to stick to the hull. So far I emptied the fuel tank and cleaned the bilge.

If any of you has any suggestion on how to dry the hull or what needs to be done, it would be really appreciated, thanks.

 

[Jim@sea]

Don't try this at home Perhaps wiping the effected area with petrol then wiping it with a cloth would help as the diesel would soak into the petrol and come away on the cloth.
Then do the same again with acetone. You may end up with an area which you could paint.
I know years ago before all the Health & Safety stuff I knew a welder who welded Petrol Tanks, as even when empty the tanks would stink of petrol, he would put paraffin in the petrol tank, then empty it, put the tank on the other side of a wall and throw a lit match in, the tank would go "pouf" (or words to that effect) as it ignited internally. He could then weld it. He saved me a fortune once as I had a BMW with a leaking tank and a new one was unbelievably expensive.

 

[pvb]

It certainly looks as if diesel has impregnated the lay-up. It can "wick" along glass fibres. It's a problem, but you're stuck with it. You can try coating the peeled hull with epoxy, or whatever finish you were planning to use. It may stick well enough to allow you to antifoul and get on with life. Best of luck!

 

[burgundyben]

I dunno about the grp but that keel is rough!

 

[[159032]]

I would suggest getting a surveyor or grp expert to look at the pics. If the contamination has weakened the grp, that bit alongside the keel could be a weak point, with the action of the keel levering the hull in an area that needs the most integrity.

From Fibreglass FAQs - East Coast Fibreglass Supplies

Why can't general lay-up resin be used for petrol tanks?
General purpose grades have never been suitable for storage of petrol as they do not have sufficient resistace to oils, diesel , petrol and other similar materials. Before un leaded petrol became the norm you could store it in an iso resin like our Crystic 491PA - this was actually sold by a company called Petseal for sealing rusty motorbike petrol tanks. Un leaded fuel currently used contains methanol which has made it more aggressive towards GRP so we now only recommend highly crosslinked iso resins like our Crystic 199 - this also needs post curing to develope sufficient resistance.

 

[pvb]

I would suggest getting a surveyor or grp expert to look at the pics. If the contamination has weakened the grp, that bit alongside the keel could be a weak point, with the action of the keel levering the hull in an area that needs the most integrity.

The problem is that, at the end of the day, the boat is still 50+ years old and has a limited value. Spending money on expert advice, and then on expert repairs, may not be economically wise. The OP might well recover the usability of the boat without incurring huge costs, which could be a better outcome.

 

[[159032]]

If the integrity is compromised the hull could crumble under high load as the keel exerts pressure.
Some expert opinion would be a good idea.
If the OP has any expertise in grp repair (he has already stripped the gel coat) I would suggest some some fundamental repairing of the area.
Did we know the boat's age?

 

[Slowboat35]

I think the aircraft fuels study should give you some confidence.
Integral GRP tanks have been with us for decades now and if strength was affected we'd certainly be well aware of it by now - and it appears we're not - so I suggest there is little if any structural problem.
Hotvac operators have reported sucking diesel through hulls from integral tanks so I don't think this is a novel problem
What to do about getting new layup or gelcoat to adhere is another matter but thorough swabbing with acetone or similar immediately before aplication would seem a good idea.
Can you try this on a test patch?

 

[yno]

Thank you all for your answers.

When I bought the boat a year ago it had already been sitting on the hard for about a year, and there was already some diesel in the bilge, however after peeling the gelcoat, there was no sign of it on the outside. After all you kinda expect a bilge to be diesel/oil proof to some extent, seems like a reasonable design. The bilge is coated in some kind of paint that seems less permeable than plain fiberglass.

The other difference with this winter as compared to the previous one is that I also removed the thruhulls. In fact, the stains only appear around holes. Maybe some motor oil and/or diesel (I noticed the engine is losing a small amount of oil) that was sitting in the boat for a long time finally found its way out through those holes. Stains around the keel could be explained by runouts I guess.

I sanded an area and thoroughly cleaned it with acetone, and although it seems the stains go beyond the first couple of layers, I did manage to get some laminate that looked like epoxy could stick to (no I dont have a sixth sense yet, the fiber just looked nice and oil free to the touch). The stains are odorless, so either:

• most of the methanol found its way out
• it's motor oil
• there is not enough diesel for it to smell

Cant think of another theory. The laminate also sounds (hammer) the same as uncontaminated one, and there is no visible delamination. Not trying to say the mechanical properties have been preserved, just reporting observations so far.

Don't try this at home Perhaps wiping the effected area with petrol then wiping it with a cloth would help as the diesel would soak into the petrol and come away on the cloth.

Well I am not at home but still do not feel overly confident about that one I did hear about some cloth/pads made to soak up fuel though, I could give these a go.

If the integrity is compromised the hull could crumble under high load as the keel exerts pressure.
Some expert opinion would be a good idea.
If the OP has any expertise in grp repair (he has already stripped the gel coat) I would suggest some some fundamental repairing of the area.
Did we know the boat's age?

I would quite happily welcome any grp repair suggestion (either from a forum member or a surveyor, it's a rethorical question not a formal one), I feel confident about my glassing skills but not my judgement of the details about the repair: how many layers? which fiberglass type? What resin? I did hear about stress problems between two different kinds of laminate should one of them be stronger/softer. But as pvb pointed out, if the survey + repair is more expensive than this boat (or a new one for that matter), it is indeed not very worth it. And yes the boat is from 69, so about 50 yo. I wish I had pvb's crystal ball.

I dunno about the grp but that keel is rough!

Cant quite capture the tone but I hope you mean well ! It's a 1.5 ton cast iron keel (fin keel with bulb version) from a dufour arpège.

I think the aircraft fuels study should give you some confidence.
Integral GRP tanks have been with us for decades now and if strength was affected we'd certainly be well aware of it by now - and it appears we're not - so I suggest there is little if any structural problem.
Hotvac operators have reported sucking diesel through hulls from integral tanks so I don't think this is a novel problem
What to do about getting new layup or gelcoat to adhere is another matter but thorough swabbing with acetone or similar immediately before aplication would seem a good idea.
Can you try this on a test patch?

Actually according to the internet it would appear we are indeed aware of it, as it would seem people with old glass tanks started having problems when they replaced lead for eth/methanol in gasoline. The test patch will unfortunately have to wait a few weeks for logistics reasons, but I'll be sure to keep you up to date with the progress. As for the study, I just realized it tests for epoxy laminates and not polyester, however, it does quote another study :

In a study on immersed glass fiber polyester composite in No. 2 diesel fuel and lubricating oil for about 200 days, the strength and modulus of the specimens were slightly reduced compared with standard dry specimens (Springer et al., 1980). Hence, GFRP experiences mechanical degradation because of moisture uptake, although some degradations are not permanent and can be restored after drying the specimens.

So it would seem there is hope.

 

[[159032]]

I think the aircraft fuels study should give you some confidence.
Integral GRP tanks have been with us for decades now and if strength was affected we'd certainly be well aware of it by now - and it appears we're not - so I suggest there is little if any structural problem.
Hotvac operators have reported sucking diesel through hulls from integral tanks so I don't think this is a novel problem
What to do about getting new layup or gelcoat to adhere is another matter but thorough swabbing with acetone or similar immediately before aplication would seem a good idea.
Can you try this on a test patch?

My quote from East Coast Fibreglass Supplies makes it clear that certain resins needed to be used where fuels are involved. In the absence of data from the boat manufacturer (and the assumption they used a standard resin for the whole boat layup) I would think that at least an investigation of the integrity is needed. A failure there would be unlikely during benign conditions.

.

 

[Stemar]

I don't know how deep it would go into the GRP, but I had a hard to trace diesel leak that set the bilges stinking to the point that Milady would send me to change when I came back from the boat because my clothes stank. The only thing that got rid of it was Bio Clean. I just left it sloshing around in the bilge and the delicate aroma of eau de bilge was gone in a couple of weeks.

 

[pvb]

Did we know the boat's age?

The OP said in his previous thread that it's a 1969 Arpege.

 

[Deleted member 36384]

The wicking is extensive, far more than bad wicking. On good GRP there is a uniform opaqueness indicating full coating of the glass strands with resin. Some of the survey books show wicking and it is mostly opaque with a few strands, clumps of strands not coated with resin. It looks to me (an amateur), that the hole cut for the seacock has allowed the diesel to travel through very small channels of dry strands, wicking along the hull to the keel. If diesel doesn't weaken the GRP the lack of bonding may very well be a cause of worry.

It may not be diesel, it could be one of the by products of the resin chemicals, ethylene glycol, from poorly mixed resin that is very hydroscopic and greasy. However, if you need to dry the hull vacuum bags with heating elements appear to be a good solution to pull out the crap from the laminate and dry it. There are tales of boats being left for years with moisture levels failing to drop despite a good airing and protection from the elements. The spaces are so small that normal airing does not work, hence the vacuum process.

Commercial Hotvac Hotvac Boat Hull Drying, Osmosis Treatment, Osmocure


The comment about the keel condition, the need for professional opinion and the extensiveness of the wicking might indicate that the hull is beyond economic repair. I have renovated an old GRP boat with no issues on the hull and it was costly and timely, and far more than the value of the boat even today, after it has been finished. The price of good quality second hand boats is very good for a buyer these days. Think carefully about the commitment and costs, especially if you have storage overheads; do try and keep the heart away from the head. Advice offered with the best of intentions.

I would recommend that you read this book, available free to download, Untitled Also read other stuff as well to get an informed opinion on repairing your hull.