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Old 03-04-2012, 07:12   #1
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X-RAY for My Boat Bottom

My boat recently was dropped in the lift by a boat yard. Thankfully, the 48,000 pounds of it fell back into water..but only 5ft of it. The front strap wasn't placed correctly and it slipped up the front, pulled the bow pulpit and sprit off the boat and opened the front top portion of the boat up like a tongue sandwich when it fell face first back to the water. Thankfully most the damage assessed is repairable and not a major....

but what is worrying me is the fact the bottom of my boat on one spot...apparently the spot where it most likely hit the bottom first, is weeping water and it's not easy to see if it is a blister (I don't think so) or a crack and to what extent the damage is. I was thinking of x-raying it and was wondering if anyone had any contacts or how I could find one and if its feasible and what you could tell on the x-ray or how else we could assess the situation without just using the eyeballs...since apparently.. no one that has looked at it so far can tell anything by just looking at it.

Any recommendations about the x-ray or other types of diagnostic testing would be great. I have a 46' island trader motor sailor. The hull is built heavy and keel has lead..so I don't know if x-raying would even make sense... but not sure how else to assess this exactly???
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Old 03-04-2012, 08:07   #2
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Re: X-RAY for My Boat Bottom

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My boat recently was dropped in the lift by a boat yard. Thankfully, the 48,000 pounds of it fell back into water..but only 5ft of it. The front strap wasn't placed correctly and it slipped up the front, pulled the bow pulpit and sprit off the boat and opened the front top portion of the boat up like a tongue sandwich when it fell face first back to the water. Thankfully most the damage assessed is repairable and not a major....

but what is worrying me is the fact the bottom of my boat on one spot...apparently the spot where it most likely hit the bottom first, is weeping water and it's not easy to see if it is a blister (I don't think so) or a crack and to what extent the damage is. I was thinking of x-raying it and was wondering if anyone had any contacts or how I could find one and if its feasible and what you could tell on the x-ray or how else we could assess the situation without just using the eyeballs...since apparently.. no one that has looked at it so far can tell anything by just looking at it.

Any recommendations about the x-ray or other types of diagnostic testing would be great. I have a 46' island trader motor sailor. The hull is built heavy and keel has lead..so I don't know if x-raying would even make sense... but not sure how else to assess this exactly???

There are non-invasive methods of surveying damage, but they are rare and very expensive. X-ray or ultrasound are generally only used for ballast keels and metal hulls, to do this with fiberglass you need to use thermal imagery. This is a fairly new method and like I said not many do it at all. If the area in question is weeping water, I would start with a moisture meter to determine extent of saturation, then grind off the bottom paint and barrier coat on the area in question and wipe it with acetone. When you wipe the laminate will become extra clear, allowing you to see any fractures or delams. This method also obviously costs because the exploratory grinding must be recoated, but the people who dropped your boat should cover it. Your Island Trader makes me think you may be east coast or Florida for some reason, so here is a Floridian company that does this-


http://www.infraredflorida.com/boat.html
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Old 03-04-2012, 08:17   #3
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Re: X-RAY for My Boat Bottom

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Originally Posted by minaret View Post
There are non-invasive methods of surveying damage, but they are rare and very expensive. X-ray or ultrasound are generally only used for ballast keels and metal hulls, to do this with fiberglass you need to use thermal imagery. This is a fairly new method and like I said not many do it at all. If the area in question is weeping water, I would start with a moisture meter to determine extent of saturation, then grind off the bottom paint and barrier coat on the area in question and wipe it with acetone. When you wipe the laminate will become extra clear, allowing you to see any fractures or delams. This method also obviously costs because the exploratory grinding must be recoated, but the people who dropped your boat should cover it. Your Island Trader makes me think you may be east coast or Florida for some reason, so here is a Floridian company that does this-
Marine Infrared Thermal Imaging
It's second this.

The ultrasound is only good [in actual practice] on composites and/or GRP hulls if you're looking for obvious voids rather than fine fissures or fractures. The low density of the material wouldn't give X-ray much of a chance unless you have a sizeable quantity of water in there. Water's an excellent scatterer of low energy x-ray so would show up in transmission but only if the radiographer is using a low energy and dose rate. Anyway, you may have to do some taking apart to get the film onto the other side of the hull so that's not going to be much fun anyway - and the problem is that neither of the techniques will give you a definitive answer so you may well end up having to become invasive anyway.

IMHO As your problem appears to be limited to one small area, and you're going to have to pull the boat out of the water anyway, the best and quickest option by far would be to take the paint off to see what is weeping more clearly without fog of antifoul and paint in the way.

Please post what you find (with photos if you can), it'll be very interesting to find out what the problem was in the end and may well help-out another CF member in the future!

Good luck!

Phil
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Old 06-04-2012, 14:58   #4
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Re: X-RAY for My Boat Bottom

How about using a tell tail dye mixed with water and fill the bottom,,use this method to track the seepage,,and then grind the hull down to base when you find it.
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Old 06-04-2012, 22:16   #5
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Re: X-RAY for My Boat Bottom

Yard I used to work at tied the straps together. I thought it was overkill at the time, seems like a good idea now.
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Old 07-04-2012, 13:08   #6
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Re: X-RAY for My Boat Bottom

plp, as far as I know xray and ultrasound can be used to see if the actual fibers in the structure have been broken but outside of something like the aircraft or oil pipeline industry, that stuff just isn't around. You might try an aviation repair shop or even the NTSB to ask how you'd find a referal in your area, assuming there is one to be had.

My concern would be that once the fiberglass has been "hit" that can break fibers internally, and the leak might indicate there are hairline cracks now weeping. Shock damage also travels in odd ways in boats, you need to check the tabbing on every bulkhead (they often break free) and examine the motor mounts to see if the engine has shifted on them as well. From stem to stern--that shock travels. The entire rigging needs to be checked as well.

That's why an insurer will often write off a dropped boat as a total loss, even when it doesn't look too bad. They don't want to hear about more damage that turns up six months or a year down the line.

Sometimes you get lucky--but get professional advice, hands on.
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