GRP (Glass Reinforced Plastic) Boat Repair

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rlaggren
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GRP (Glass Reinforced Plastic) Boat Repair

Post by rlaggren »

Hi Lois

I've started this thread so there can be as many contributors as possible.

We all have different approaches to a project. Mine involves using the inet to find the stories of others who have already done the same thing on the same boat; barring finding the exact same boat, I look for how-to's on similar boats. There is a LOT of good info (and bad also - you learn the difference over time) on boats easily available - but when starting from scratch like you are, it takes learning time to get a "feel" for your situation. I can't think of anything as important as spending the time to absorb an overview, a general idea of what holds GRP boats together, what makes them work, where they fail and what people have commonly done about it. If not you, then somebody there with you working on the boat. Without this general understanding you're just rolling the dice and pasting on patches with only the slightest chance that the boat will end up "fixed" enough to sail safely and make you and everybody happy.

Your description of "keel repair" doesn't ring any bells with me and it seems likely that when you learn about how a boat is put together you may well refer to that problem differently and likely somebody here would recognize it. Keels are not something ANYBODY wants to mess with if they don't absolutely have to. They are a major structural part of any boat and I'm not really qualified to say much about that.

So do google "ANASTAR" and see what you find; somebody may have posted about this boat from a previous life. Then google the boat manufacterer and model and you will almost certainly find lots of info. I think you need to get an overview of all that is going on with the boat before trying to plan much less do anything to the boat. As you noticed, material are expensive so you don't want to make false starts and maybe have to just kiss off hundreds of $$$.

> pox

Pox has to do with water working its way up into the GRP along threads of glass which didn't get wetted out fully during production; the water interacts with resin compounds and creates an acid and other unhappy chemicals. There are also other causes and mechanisms described on the inet and it's often blamed on "bad resin" resulting from oil shortages in the '70s. Generally it's a cosmetic not a structural problem but that depends on the extent and depth of the pox; it can look _really_ ugly w/out being dangerous. Some boats end up looking like a pebbled sidewalk all over their bottom while others have one or two bubbles and you have to look hard for them. Repairing individual bubbles (less than, say, 500 over all the bottom of the boat) involves grinding out the bad area (trying not to go too deep, but still getting it all) drying with heat lamps for as long as you can stand to wait, and applying epoxy resin to wet the area, then mixing a thick epoxy paste with structural filler and filling the hole very slightly below the surrounding surface; then after the patch "kicks" (goes through jelly stage and gets firm) but no longer than 6-8 hours, mix a bit of epoxy w/light weight fair filler and smooth the patch up to a little above the surface.

The object of the repair is to prevent water from seeping back into the the GRP. Whether its individual bubbles or the whole bottom, epoxy is used to seal out the water (epoxy is more water resistant the polyester resin used to build the boat).

The problem with pox is that the quality of the repair depends very much on getting the area of the bubble completely dry and that can be extremely problematic and take a very very long time. There are boats where the bottom was covered w/pox that have been sitting in yards in Mexico for 2-3 years in 100F 0 humidity so their bottoms (which have had 1/4" or so of the surface ground off over the entire bottom of the boat) will dry enough for a good repair to "take". There are numerous controversies over pox repair and many repairs have only looked good for 2 or 3 years, then large areas sprout bubbles again.

So a whole bottom covered with pox is not something you want to deal with. A few bubbles you can take a shot at if you want and think you can get it dry enough (heat lamp) to make a good repair.

WARNING: GRP does NOT LIKE HEAT. IIRC most polyester GRP starts to weaken and break down when it's temperature rises about about 130F and epoxy starts to degrade at 120F. So when you're using hair dryers or heat lamps to dry GRP, pay careful attention and keep the temps below 110F. Most people cannot hold their hand comfortably on a surface of 110F so if you can hold your hand on the GRP continuously w/out distress you should be OK.

> keel

As I've said before, this needs to be fully clarified by somebody who has seen the problem. If the keel is indeed in need of repair, this might well be a total show stopper.

> General boat stuff...

Boats usually die from the top down. Ie. water leaking in from above does way more damage than water leaking in from below. Of particular import is what is construction type and condition of the deck. GRP decks were often sandwiches of GRP on the top & bottome with plywood or balsa in the middle - about 1/2-3/4". The plywood or balsa rots from water leaking _into_ the deck from screws holding stuff down on the top and the deck becomes spongy and weak. The boat's strong points are (must be) under the mast and at the attachment points for the standing rigging, the stays, at the bow and stern and to the sides; if these have been weakened by leaks, then they must be fixed or you risk losing the mast. The connections for the stays are usually some kind of stainless steel fittings - they crack. The need to be examined with a halogen light and a magnifying glass; using a die to reveal the cracks helps, using a buffing wheel or sand paper on the fitting hides the cracks. You do NOT want to hide these cracks. A cracked fitting must be replaced.

Does this start to look like a lot of work? It's not rocket science but it needs somebody who can spend several hundred hours finding and correcting the major issues - and that person needs to know which issues _are_ major issues and how to find and deal with them. Finding the issues is a job specialty of a marine surveyer. Last I checked they cost $500-$1000 for a survey; surveying the rigging above the deck is an extra cost option. They produce a 20 page or more report listing all that's wrong with the boat and some indication of what ittakes to fix it. There are as many scam artists in the field as there are bad lawyers or mechanics so you have to spend considerable time asking around and finding the good one. However, it's generaly aknowledged by people with decades of boat experience that they are way more than just worth the money. $1000 (usually some less in the 30' range) up front can prevent sinking $5-10k into a boat _then_ find you need another $20K to get it sailing.

When "storing" the boat you MUST prevent leaks from the top down. That can be extremely hard to do because of all the screw holes and other ways water canget in. The fastest dirtiest way I know to do this is with blue masking tape; cover every crack, seam and screw that even hints it might leak. Next summer the tape is stuck forever and must be scraped off with a wood or plastic scraper but it will have kept the interior mostly dry. Another big help is a tarp hung over the boom and down sides covering as much oftheboat as possible.

Well I've beat the keyboard to death - the space bar and severaw keys are quitting. So I better had too!

Rufus

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Re: GRP (Glass Reinforced Plastic) Boat Repair

Post by stuartcnz »

The only photo I could find online of a 24 ft Riviera Star, has a bulb fin keel. Couldn't tell what it was made from, but I would say that the biggest issue is likely to be the keel bolts. I wouldn't even look at doing anything to it, without knowing the condition of those bolts.

If the bolts are okay, then there wouldn't likely be to much issue structurally with a keel of that design. Ascertaining the condition of the bolts though, will necessitate the removal of the keel, which is somewhat of a specialist job, as the boat will need to be lifted off the keel, unless you are fortunate enough to be able to pull one bolt at a time. If it is a cast iron keel the bolts will most likely be galvanized mild steel, hopefully connecting to the hull with a flange on either side of the keel, if there is no flange then the job gets a whole lot harder.

If it is a lead bulb on the end of the keel, the only suitable bolts are bronze, anything else will almost definitely be suspect, and if they are stainless steel walk, no run away from the whole project. As fully immersed stainless steel suffers from crevice corrosion. And it would also indicate other likely poor metal choices on the boat.

rlaggren
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Re: GRP (Glass Reinforced Plastic) Boat Repair

Post by rlaggren »

Hi Lois

I've seen a bit of pox. But first you'll need to pressure wash the bottom first thing it comes out. They should have a machine at the haul out, should do it as part of the deal. After that there will be a lot of scraping. A carbide pull scraper with as wide a blade as you can find may be the easiest. They cost 3 times what a regular painter's scraper costs but a regular scraper will got blunt w/in about 5 minutes. They can be sharpened with a diamond "stone". The lot will cost about $35 at HD.

Blisters will become apparent as you scrape. You'll recognize when you get some.

When you get to sanding remember that the bottom point was/is poison. Try not to breath it. Don't expect to grow much where ever the dust goes. You want to wear a _real_ breather mask with the best dust filters. Make sure the rubber seals completely on your face and replace the filters if you smell anything or if the inside of your nose changes color (!).

Rufus

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