Dents in GRP hull from cradle

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Chaffers

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Hello,

My tub was craned into the water a few weeks ago but I only noticed at the weekend that she has two dents either side of the hull forward of the mast which appear to correlate to the front mounts on the cradle she was sitting on.

At a guess I'd say they were less than an inch deep. The hull dates from the early 70s hence is thick (3/4 inch thick or so ) GRP.

I had a full survey done on her in January which didn't throw up any problems with the hull, are these likely to be a problem?
 
Solid layup that thick would require enormous force to put one inch dents in it. In fact I would say that it would be near impossible to do such a thing without fractures appearing. Either these are shallow depressions that look bigger than they are, or there is the grim possibility that the thick layup has become spongy, allowing for easier distortion.
 
Get the yard to haul her out sharpish and get the cradle impounded before someone alters the settings. You'll need a good surveyor and lawyer too. I've seen poor boatyard practice dent a fair few boats. Those hydraulic trailers are the worst offenders, followed by idiots with shores, wedges and a hammer.
 
If those dents are new, and the grp is not totally shot, I would expect crazing of the gelcoat.
Could they have been there since new? If the boat was turfed out of the mould early and put on a similar cradle?
Sandwich construction will often dent without crazing if the skin is thin though.
 
Would have to be an identical cradle if so.... DSCN0114.jpgDSCN0115.jpg

She was listed in an old advert as foam sandwich construction... Survey and others say solid GRP though..
 
Could you possibly edit one of the last two images to show whereabouts the hollows are?

Back pad or front?

Further edit.

Have got got a pic from the other side. The props make almost no sense to me.

The strut that looks like it it supporting the boat by the toe-rail/capping.

The aftermost struts are not symmetrical.

I can't see any pads on the bow struts on this side.
 
Last edited:
Hi

Just wondering if there is any indentation on the inside of the hull where the external dents area? It may be the hull is solid glass below the waterline and a sandwich construction above (not an uncommon method).
 
The front one on the second photo, between the strop and the leg frame slightly below the waterline. Same on the other side.

Difficult to check the stern ones though could be the same story...
 
Have got got a pic from the other side. The props make almost no sense to me.

The strut that looks like it it supporting the boat by the toe-rail/capping.

The aftermost struts are not symmetrical.

I can't see any pads on the bow struts on this side.
Click to expand...

No photos from the other side handy whilst she was in the cradle.

The props are bolted to the hull and act as beaching legs as her eventual destination has a ramp but no crane.

I couldn't find any deformation inside the hull on either side, though on one side the dent would be behind the heads.
 
Just been on to the surveyor, who says he didn't notice anything either in January or two years before when he surveyed her.

No-one seems to know whether she is grp or foam sandwich so I'll see if I can contact the designer...
 
If it's 3/4" thick solid fibreglass, as others have said, I'd be amazed if you could get dents that deep without cracks. Avocet has been in a cradle for 6 years now (an early '70s solid layup) and IF there are any dents they are (literally) thousandths of an inch deep. That said, looking at the photos, I don't think yours are much more than 1/4" deep - appearances can be deceptive though.

I think it's much more likely that yours is a sandwich construction and the "filling" has crushed, locally under the pads. Not great. Can you take out a skin fitting and see what the hull construction is?

Either way, I don't think your boat's likely to sink as a result of these, so I'd probably just casually monitor them for the rest of the season now and then look at doing something about them next layup.
 
I really doubt that it is 3/4" thick solid GRP on the sides. It would make this boat extremely heavy. You should be able to tap the hull with a heavy coin and tell whether there is core there ..... or look at the interior, the core is unlikely to go up to the deck molding, so you should see a difference in levels there.

As for the dents ... I need better photos than these.
 
Her designer has confirmed that she is airex foam cored throughout.

Unfortunately I only noticed the dents this weekend, not sure how I missed them when she was being lifted. I took lots of photos but none specifically of the dents or the area around the dents.

The surveyor rang back and said she was full of water on the cradle for quite a while so he thinks the weight of it has warped the hull against the cradle supports....
 
This is really a job for the surveyor.

Unfortunately a lot of cored yachts get damaged when they aren't supported properly ... i.e. not on the bulkheads, or the pads are too small. The damage can also be done alongside a dock, especially when rafting.
 
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