Hulls & Gelcoats

[david_e]

Went to look at a used Elan the other day and noticed a few things I've not really encountered before. The first was that in some of the internal areas not lined I could see daylight through the hull. Broker/importer said it was normal and that they are providing more waterproofing than strength in this area. Second was I thought that the hull looked a little more "matty" than the norm. i.e. I could see evidence of the strand matting when looking down the line. Thinking this might be a defect I mentioned it the broker/importer who explained that seeing this is often the norm and it is a 3 part NGA gelcoat which is sprayed, typical on modern boats. Benefit is that it is more abrasive than the traditional method of brushing/rolling it on.

Appreciate that the main reasons are likely to be for economy in production, but is this something I should be giving more than a passing thought to? Appreciate some experience/input.

 

[peterg]

You can often see 'light' coming through areas of GRP particularly on white/cream hulls which have not been flow-coated on the inside, it doesn't necessarily mean it is thin. Seeing the matting is rather more likely to be evidence of a lighter 'build' than others or could just be that they save costs by not finishing the inside to 'outside' standards like some other builders but it depends on the thickness of the lay-up as well - the manufacturers should be able to provide a specification for the lay-up (kilos per square metre or similar) which you could compare to other makes.

 

[Guest]

No worry

like the post above, it's normal. My last boat was built in 1971 and had VERY thick GRP yet it still allowed light through. Worried me silly when I first noticed it.

Manufacturers often finish the inside too, but often just hide the rough finish under a liner. Indeed, there's a lot to be said for not having a liner: better access to the hull in case of a holing, see the condition of the frames and the bonding, etc.

Relax.

 

[jamesjermain]

A question

Is the 'matty' look on the inside or outside. I

f it is on the outside you are getting 'print through', either because the gelcoat is too thin or because a layer of 'tissue' has not been included before the first layer of woven rovings or mat; or both.
In either case it need not reflect a lack of structural strength, but a thin gelcoat will tend to wear away more quickly leading to unsightly discolouring and an early recoating job.
Best practice in laying up hulls is to put down a thin, finely woven grp cloth after applying the gel coat. This protects the gel from the later, coarser woven cloths which can leave an imprint through the gel coat that may become visible from the outside. This is unsightly rather than serious. The gel coat may still be thick enough to last a reasonably long time but there is a chance it will wear unevenly and need overcoating earlier than you might like.

JJ

 

[david_e]

Re: A question

Thanks for this info very helpful, it is on the outside, and I have to say I have seen worse. Thinking ahead for budgets any rough idea what this would cost on a 30 footer?

 

[Guest]

Re: A question about gelcoats

James,

On that general topic, I have heard of people having their gelcoats renewed (as opposed to being repainted). In broad terms, how much does the process cost for a 33 foter and is it a practical solution for getting the new look back into the cockpit and deck?

 

[jamesjermain]

I\'m not sure...

...but I would guess about the same as epoxy treatment below the waterline. The materials are somewhat different but the man-hours are probably about the same

To be honest, though, I can't see the point. Gel coat above the waterline may lose its colour and go chalky, but it doesn't blister and fall off as it does below the waterline. A properly prepared and professionally applied topside repaint will be every bit as shiney and durable as the original gel coat, and by not taking off the old material, you increase, very marginally, the thickness of the outer layer and reduce the risk of show-through.

Possibly if the hull was very warn and chipped it would be worth it.

As for the cockpit and deck, I really can't see that it would be worth the expense. It would be very difficult to grind back or blast off the gel, and you would have to redo the non-slip moulding or replace it with deck paint.

JJ