What caused this unusual gel coat cracking on a Typhoon

[LilYachty]

I am beginning restoration on a 1983 Typhoon Weekender. It has a peculiar cracking pattern in the decks aft from the chain plates and in a couple other spots. I have seen typical stress cracks, but these aren't the same. Does anybody know with certainty what causes them? As far as I can tell, the core isn't wet. it doesn't have any detectable softness and hammer testing doesn't reveal any conclusive signs of rotten core. The boat spent the last seven years out of the water under a tarp. I'm not sure if it may relate to that. Any help would be greatly appreciated.

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[wikakaru]

That's actually not "unusual" gel coat cracking, at least not on the small Cape Dorys. Like you, before I bought my Typhoon in 2016 I had never seen that sort of gel coat cracking on other brands of boat I had sailed. My Typhoon has it, and my "new" 1981 CD22 also has it.

From what I've read on this board, the cause of the cracking is that Cape Dory, in their usual "let's overbuild it" mentality, applied the gel coat too thick and the extra thickness makes the gel coat brittle and it cracks. Perhaps different rates of thermal expansion between the fiberglass and gel coat? It is interesting that it only seems to appear on the decks and not the hulls. Perhaps because vertical surfaces wouldn't hold the same thickness of sprayed gel coat as horizontal surfaces.

The general consensus is that the cracks are, as you have found, typically cosmetic rather than structural.

When we refit our Typhoon in 2016 we chose to have the boatyard only refinish the cockpit area instead of the whole hull and deck. This was the worst area of cracking on our Typhoon, and it is the area we typically look at and spend time in while aboard. It was significantly less expensive to do just the cockpit, and it is easier to ignore the cracks on deck with that beautifully finished cockpit to look at.

Good luck restoring your Typhoon. The results when you are done will be well worth the effort.

Smooth sailing,

Jim

Cracking in the cockpit drain gutter, port forward

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Cockpit after gel coat restoration, during teak varnishing

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[Walter Hobbs]

Wow! Did you polish your hinges?

[wikakaru]

Wow! Did you polish your hinges?

Yes and no. Yes they are polished, but no I didn't do it. Spartan Marine sells two different finishes on those hinges, and one of them is polished the way you see. When I ordered them I thought I was ordering chromed bronze instead of polished bronze. I haven't kept up with the polishing, so they have reverted to normal weathered bronze after 3 years. I'd rather be sailing than polishing.

Smooth sailing,

Jim

[LilYachty]

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The sort of cracking in your photo is pretty typical stress cracking that occurs in high stress areas like corners and usually run parallel to the corners. My 87 Catalina 22 has those on the cockpit too. The thing about the ones on my Typhoon is they are randomly oriented to one another and aren't in a high stress area. I went ahead and chipped away the gelcoat at the worst crack and found that the gelcoat was completely delaminated from the layup. The cracking is on the deck on both sides of the cabin starting about a foot back from the chainplates extending back to the end of the cabin. There are some cracks on the sides of the cabin in the same area. I'm beginning to think it is related to standing water or ice under the tarp. The boat was in the snow belt of northern Ohio and would have been subject to a lot of moisture and freeze thaw cycles. The way the deck curves, if the nose of the trailer was low, water may have collected there. This is a guess. Here's a photo of the area where I removed the chip.

[LilYachty]

Wikakaru did you paint your cockpit or actually repair it with gelcoat? It looks great and

[wikakaru]

The sort of cracking in your photo is pretty typical stress cracking that occurs in high stress areas like corners and usually run parallel to the corners. My 87 Catalina 22 has those on the cockpit too. The thing about the ones on my Typhoon is they are randomly oriented to one another and aren't in a high stress area. I went ahead and chipped away the gelcoat at the worst crack and found that the gelcoat was completely delaminated from the layup. The cracking is on the deck on both sides of the cabin starting about a foot back from the chainplates extending back to the end of the cabin. There are some cracks on the sides of the cabin in the same area. I'm beginning to think it is related to standing water or ice under the tarp. The boat was in the snow belt of northern Ohio and would have been subject to a lot of moisture and freeze thaw cycles. The way the deck curves, if the nose of the trailer was low, water may have collected there.

Sorry, the photo I posted was one I could easily lay my hands on from prior to the refit in 2016, and you are right, most of the cracking shown is stress cracking. Below are some photos I just took of the deck area (which was not refurbished in 2016) that show the type of cracking you are talking about that is randomly oriented. To me it almost looks like someone practicing trying to throw a knife and embed it in the decks, though I'm certain that's not what happened.

My boat spent its first 36 years in Alabama, and was stored inside during the winter, so I doubt ice and freezing is the issue, at least with my Typhoon.

In the photos you sent, it looks like the randomly oriented fibers in the mat were not fully wetted-out with resin, so there are air pockets between the gel coat and the rest of the fiberglass layup. The cracking may be caused by the air pockets expanding in the sun and cracking the gel coat from the inside.

Those photos are very helpful to the rest of us--thanks for posting!

Here are the photos of some of the cracks in my Typhoon's decks that are more similar to yours:

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[wikakaru]

Wikakaru did you paint your cockpit or actually repair it with gelcoat?

I can't take credit. The beautiful work was done by Flat Island Boatworks in Pensacola, Florida. If I recall correctly, they ground the original cracked gel coat, then laid a thin layer of cloth and epoxy, painted that with a high-build epoxy, sanded smooth, filled with a low-density filler, and did final fairing sanding before spraying on new gel coat.

I would love to have them do the same to the rest of the boat, but that's way too many $$$ to think about, and I can't bear to have the boat put out of commission for as long as it would take to do the work myself, assuming I had the patience and fortitude to do it, which I don't.

Smooth sailing,

Jim

[LilYachty]

Yeah, that is the identical type of cracking. Was your boat under a tarp for extended periods?

[wikakaru]

Yeah, that is the identical type of cracking. Was your boat under a tarp for extended periods?

I don't think this boat was ever stored for extended periods. From what the previous owner told us, she was sailed every summer on the lake behind their house, and stored every "winter" (but this is Alabama we're talking about, so "winter" is a relative term, because snow would have been rare indeed).

When we bought her she was stored in a big powerboat dry-storage shed:

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We're not sure how long the previous owner used indoor storage--the boat did come with a custom Sunbrella canvas cover that fit around the mast and over the boom and enclosed the whole deck area (we have never used it), so the boat was obviously covered at some point, but it wasn't a simple tarp. Because the cover was designed to fit around the mast, I'm thinking it was used during the boating season, perhaps to keep the bird poop off the boat, and removed for sailing.

--Jim

[LilYachty]

Nice boat! Where on your boat do you have the cracks? On mine they are on the decks rom about a foot aft of the chainplates to the aft end of the cabin on both port and starboard sides. Some are on the sides of the cabin itself. They don't occur elsewhere on the boat. Just wondering if yours are in the same area?

[LilYachty]

So the verdict is in on the cause of this type of cracking. It is due to a lack of resin in the chopped strand mat just beneath the gelcoat. When they laid up the boat, first they spray the gelcoat into the mold, then start laying in the mat and woven roving, wetting it out with resin as they go. In this case, they did not work the resin into the mat all the way. This results in dry strands of mat beneath the gelcoat, entraining air into the layup and the gel coat above those strands cracks. The random orientation of the cracks reflects the random orientation of the strands. The solution is to remove the gelcoat, sand the surface of the layup, then lay some new mat and either finish with gelcoat or paint. Here is a photo of the area I pictured in the OP, after exposing the layup. You can see the poorly saturated, light-colored fibers of the mat after sanding. I started removing the gelcoat with a wood chisel and loose, completely dry fibers were sticking to the underside of the gelcoat. All in all, this represents some pretty poor workmanship by the factory.

[robwm]

LilYachty, you're spot on with your interpretation of how the problem occurs: the factory probably "starved" the fiberglass layers of sufficient resin.
Once upon a time, during the mid 1960s to 70s, I worked as a technician in the lab of a major resin manufacturer (national firm that I would rather not mention) where I was responsible for doing trial layups of gel coat/fiberglass mat or roving/and resin composites as part of our quality control program before releasing resin batches to the various vendors/manufacturers. The primary mechanism for failure of the layups was inadequate saturation (sometimes over saturation) of the fiberglass layers. Second in line was excessive time delay between the application of the gel coat and the subsequent layers and resin, and, third in line was wrong proportions of catalysts (they cause the resins to set). We had a hard time ensuring proper saturation in the lab's setting even with rather stringent procedures in place, so it is not surprising that inadequate saturation, time delays in the build up of the "fiberglass sandwich", or improper addition of catalysts were/are a real problem in production settings where personnel are often insensitive or not properly trained to the nuances of the chemistry that is involved. Such problems were probably more prevalent back in the "earlier days" of fiberglass use when our CDs were manufactured.
Unfortunately, once the problem is "cast and set in cured resins" so to speak, the only remedy is to re-build the defective areas as discussed in the previous postings.
Robert,
1982 CD22, HunkyDory

[LilYachty]

I guess that's why they invented vacuum bagging!