Crack in GRP hull, to buy or not to buy ?

[Guest]

We are looking at a Super Seal 26 (Baker built hull #58). We were going to use this smaller yacht while we work on a long term steel project. However we found some cracks in the hull on our last inspection and are not sure how to interpret these. Some photos are to be found on the following page:

http://groups.msn.com/projectyacht/superseal26bakerbuilt.msnw

The craks are in the forward section of the hull close but quite at the bottom. They are one continuous crack that runs for over one meter on each side (port & starboard) of the hull. There is no surface displacement inside or out and the crack is not visible from outside.

There is also a crack in the centerboard well (see photos) and it look like it has been repaired in the past with the crack now in the repair. The yacht has a ballasted hull and a lift keel without ballast.

We are new to GRP and have no idea of the implications of the cracks to the integrity of the boat. The boat is located a long way inland away from the water so getting a marine surveyor to look at it is out of the question.

If anyone can shed some light on the subject it would be much appreciated.

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[oldsaltoz]

G'day Robbony,

Looks like the cracks in the keel case were not fully ground out prior to re glassing, the metre long crack in the hull is a bit of a mystery, may be haul out damage or poor support on the hard.

Repairing them should be no problem apart from the god awful amount of dust your going to make. Just make sure you use only epoxy resins and fabrics designed for use with epoxy, that means no chopped strand.

When grinding out cracks, keep going till there is no sign of the crack in the newly exposed area, then go another 100 mm or so to remover the material that has been stressed, this should prevent further cracking.

If you need further information or sites with info, just say the word.

I'm sure our readers will have all the answers you seek.



<hr width=100% size=1>Andavagoodweekend, Old Salt Oz /forums/images/icons/cool.gif

 

[Guest]

Thanks Old Salt Oz

How wide a strip would you make the repair beyond the crack ?

Does anyone have any good links to sites that explain how to do GRP repairs ?

The yacht is on a skid with two supports across the bottom. The boat had been transported from Bharain to Australia on a ship then transported 700km on a semi trailer to where it is now. Though I suspect the cracks originated well before transport and the current owner took posession. The floor does not look repaired. Perhaps it had been beached a bit too brutally, sometime in the past.

The boat would have to be transported again so I guess that all repairs should wait until it reaches the launch point.

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[johnmuir]

sailboat hull and deck repair by Don Cassey is a good guide. Use a Dremel or similar to open up cracks and spend time with sanding repair, once filled, with eventually the finest wet and dry paper you can fine. Work down the grades and try to avoid sanding good gel coat as much as possible. Finish with paste, can't remember brand, which polisshes and removes surface abrasions and again polish with Mer. See book for complete details
John

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[snowleopard]

sorry, can't agree with 'only use epoxy'. for a bond to grp, experiments conducted over 30 years by derek kelsall, whose designs rely on grp-to-grp bonds, show that polyester provides a stronger bond than epoxy in these circumstances (not by much, but certaily enough to disprove the widely held belief that it has to be epoxy).

in all other cases, e.g. bonding to wood, epoxy is the only answer but when polyester bonds direct to old polyester there is some chemical bonding taking place and the strength is 70-80% of the original laminate.

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[oldsaltoz]

G'day Ribbony,

If you have access, try to do the hull repair from inside, this will save you Woking overhead and reduce the area of gelcoat to be repaired/replaced.

You only need an overlap if you consider it needs extra strength, otherwise, use a 4 inch grinder and grind out the crack with about 1 and a half to 2 inches each side feathered, so you finish up with a 3 to 4 inch wide depression.

Run some masking tape around the area when grinding is complete and tape some plastic down, this will save you a lot of clean up later and avoid drips on non repaired sections.

If the gringing creates a hole thru' the hull, cover with plastic sheeting and secure it with some thin ply or other material that will conform to the hull shape.

Re glassing is just a matter of brushing on a coat of resin, laying a pre-cut strip of cloth and rolling it out till fully wetted, then apply another strip and so on. Keep an eye on heat build up after the first 4 lays, stop if it gets too hot or the resin will boil and bubbles will form, weakening the repair.

Use a flexible straight edge (a plastic ruler is fine) to level the last lay-up flush to the surrounding level.

If you think it needs extra strength, you can overlap about 3 inches, with up to 4 layers, but make sure each layer is a bit larger than the one being covered by not less than half an inch, this will produce a feathered edge and avoid a hard spot.

Make sure you have good ventilation, a fan blowing unto the boat from outside helps, wear surgical rubber gloves (about 7 quid for a hundred pairs) and a good quality respirator.

I have included a few links to get you started.

Sounds like you are near Alice springs, I'm only 1,500 Km east, Whitsunday Islands area.

http://www.atlcomposites.com/west_system.htm

<A target="_blank" HREF=http://www.mdacomposites.org/materials.htm#Epoxy>http://www.mdacomposites.org/materials.htm#Epoxy</A>





<hr width=100% size=1>Andavagoodweekend, Old Salt Oz /forums/images/icons/cool.gif

 

[Guest]

That is an excellent rundown and some good links to GRP related sites.

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[PeterGibbs]

Cracks are usually signs of stress or damage, resulting from inappropriate use or poor design / layup. I urge caution - there is always another deal; this is the preferred route. Even GRP fails eventually - maybe that's what happening here.

PWG

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[warrior40]

Cracks in the gelcoat are common, I wouldn't let it put you off, most boats will definately have them somewhere or other.At least you know where they are.

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[tcm]

The internal shot seems to show a newly-added post-sales support, needing cutaway of the teak wall bulkhead lining, possibly following a fairly significant (yard?)accident or , well, something has happened. As others say, it wil probaly be okay. But your worried and so wil be you buyer. Offer very low, 25% under asking.

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[billmacfarlane]

A long way inland or not the only way to find out what's causing your cracks is to get a marine surveyor to look at the problem. It'll cost you more but what's that compared t0 buying a complete pup which in this case is possible. You also might try phonong Bill Parker who buils the current models.

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