Well kids the hulls on my Prindle 16 went soft on me. I need help. Just the topside of the hulls forward the tramp are a bit mushy. Also need to know the best product to clean/restore gelcoat. The boat has been hammered by UV. any info would be great

Thanks, Jason

any help on this would be great guys. Please help

Hi Jason,
What has happened to your hulls is called "low cycle fatigue". The deck of a catamaran hull is in compression bow to stern. The forestay is pulling up on the bows, the mainsheet is pulling up on the sterns and the mast is pushing down in the middle. This tries to bend the hull and make the deck get shorter which puts it in axial compression. Also punching through waves tries to bend the bows up which adds to the hull bending and deck compression problem. The maximum load, high stress area, is just in front of the trampoline, 1 to 2 feet, in the deck. After this has happened millions of times/cycles the bond between the foam core and the fiberglass skins gives up. The foam sandwich in the soft areas of the deck in your boat has delaminated, not glued together anymore; it is old and tired and just worn out. This is hard to fix. You have to rebond the inner skin to the foam and it is major sergury to get to it.
Here's a way to do it. In the soft area of the deck, grind away the outer skin and foam down to the inner skin. Bevel the perimeter of the ground away area back on a shallow slope. Replace the removed/ground away foam with a mixture of resin and microbaloons. Leave the microbaloon core about 1/32 inch low relative to the original deck around it. You can use the original deck around the repair to guide your squeegee. After this has cured, restore the top fiberglass skin coat and add a couple of extra layers this time tapered on the forward and trailing edges at least 1 inch per layer. The hull should have been built with additional fiberglass layers in this high load area in the first place but it wasn't, hence your problem. Paint the repaired area and you are ready to go sailing again and ready for another several million low cycle fatigue cycles.
Good luck,
Bill

Illustrated Delamination Repair Article



Hope this helps.

Hi Damon,
What you are showing here is a 'blind fix' to a delamination problem. The fixer does not know whether or not his work is actually glueing things back together or not. When you cut one of these problem area hulls open, remove the outer skin, the first thing you find is a handfull of dust, ground up faom that broke away from the outer skin. Just because you squirt some resin in under the skin doesn't guarantee you are glueing anything together except maybe a bunch of dust particles. To get the resin to flow under the outer skin, you drill shallow holes on one side of the delam area and vent holes on the opposite side. You cannot force resin in under the outer skin unless you let the air out in another position. Also this 'blind fix' method does nothing to rebond the inner skin to the under side of the foam. It is in the same condition as the bond betweem the outer skin and the outer surface of the foam. I have seen sailors attempt to fix deck delams on H16s and P16s with the 'blind fix' method but I have never seen it be successful.
Good luck,
Bill

Bill,

You know a lot more about boat construction than I do, so I'll bow to your expertise on this. All I know is that I've seen many old cats revived using the injection method and they seemed to be solid. Maybe it's an illusion.

I have a hard time picturing how your method works exactly. It seems like you'd need a lot more skill with glass and it would really need a professional. The injection system is meant to be a "do-it-yourself" solution, so it makes sense that it wouldn't be as good.

I wonder if it would be possible, using your method, to cut the deck off, fill with the micro balloon mixture and stick the deck back down?

Also, Hobie Cat Company endorses the injection method for the old boats, they actually have instructions for it at
http://www.hobiecat.com/support/tech/delam.html

Damon,
Just to back you up, our son Dave is a professional fiberglass guy, and he uses the injection method that you showed in that article on your website. He repaired a soft Laser deck for us, and I watched him drill all those little holes all over it and then use the syringe to pump epoxy into the holes. Worked fine -- when he was done, the deck was solid as a rock. Just looked like it had chicken pox from all those little holes.

Usually people who have an old boat with soft decks are not planning to use it for racing and don't care about adding a little weight. If you can use the injection method to economically restore an old boat and extend its life without grinding fiberglass and shortening your own life, why not?

Damon,
The hull failed because it was not strong enough in the first. Doing a fix that is less than 100% certainly isn't going to last long. I am speaking from experience having helped Hobie sailors.
Bill

From Hobie's own site:
http://www.hobiecat.com/support/tech/delam.html

This method has been tried and true. The only thing I would actually do differently, is once you've filled the layer with epoxy, then dips some drywall screws in veggie oil, and sink two or three of them completely through both layers. This will pull the bottom fiberglass layer back to the top. Once the epoxy has kicked, remove the screws gently, and plug the holes.

The repair that Bill mentions, is the kind that I did on my boat, except I actually laid some marine grade laminated hardwood up under the deck and then used a buttload of low density filler and some layers of glass to fix the deck. Its rock solid, but I wouldn't want to undertake that project without epoxy/fiberglass experience when the epoxy injection will do the same thing for you.

the method bill suggests to use is the right way to do the job. it replaces what was in the boat originally
and brings it back up to the original strength. the injection method works, but it is not 'right'.

wow guys thanks for all the help. I will let you know what I decide to do. thanks again

Basketcase,
The deck is biult with a foam 'sandwich'. The fiberglass has become detached from both sides of the foam; the sandwich is coming apart on both sides. Reglueing the topside glass to the foam is half the job. Squirting resin between the glass and foam on the topside does nothing for the bottomside. Reattaching the topside glass and foam produces a construction that is much less than half as strong as the original construction and it has failed. If the factory had just put a couple of additional layers of glass 2ft and 3ft forward of the forward posts on both sides of the foam at original construction, we wouldn't be having this discussion. It would make the hull cost another ten dollars to build.
Bill

ya bill. i know. i am a builder by trade. for some of these guys with boats that sail every two or three weeks on small lakes, i think the injection method works fine. the boat probably will not see 15 knots, much less the conditions your super cats were built for. i do not agree with your statement as to the cost to build the boat right in the first place. i think it would be lower. scrap off cuts could be used and the 10 oz glass takes nothing to wet out. on the boat sprit of canada, we put a 10 oz on her hull to sand into. we did not wet it out at all. we just let the vacuum draw the resin through it and into the bleader.