Maststep about to go?

Martin23

New Member
Wondering if anyone could let me know if I have tell-tale signs of a mast step weakening. See attached picture. There's some bulging under the mast bore on the underside of the hull. Is this normal? Just an old hull (late 1970s or early 1980s)? Should I be worried about this? I didn't notice this when I bought the hull 6 years ago. I noticed this last year so I figure whatever is going on that the condition has progressed.
 

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That does have the same shape as the so-called 'donut,' which is a piece of plywood on the bottom (inside) of the hull, into which the foot of the mast step is secured. And it certainly seems very plausible, very likely, that the bulging is caused by the plywood being saturated with water and expanding, and weakening everything around it. Here's a pic of the donut inside my boat, after the mast tube let go.

This mast tube-to-hull joint has failed on a lot of older boats. FWIW, if that was my boat, having been thru what happened to my current boat --- even if it WASN'T bulging, based JUST on the age of the boat, I'd put in an inspection port and pre-emptively reinforce that joint, because (1) it is a proven failure point, and (2) it is a WHOLE lot easier to reinforce it BEFORE it fails, than to fix it after it fails. This is because when it fails and the mast tips over, it tears the deck up badly, and that's a whole lot harder to fix, than simply reinforcing the tube. Here's 2 pics of my deck after the failure, with the remains of the donut next to the hole.

At the VERY least, if it was my boat, I'd open up an inspection port pretty much right now (before sailing it, especially in more than say 8 knots), so I could see what's going on in there. And honestly I'd reinforce it NOW - REGARDLESS of what the visual inspection shows, "just cuz I can." It might take an additional hour or 2 beyond putting in the port, and might take $30-40 worth of epoxy & glass. This is a very good case of "an ounce of prevention being worth a pound of cure."

In addition to the risk of that mast tube letting go --- it sure "appears" that a soggy + expanding donut is damaging+weakening the bottom of the hull too. That just sounds really problematic and expensive to me. I'd get in there, tear up that old donut, make sure the bottom is OK, and do whatever needs done now, before something fails, and makes the problem a whole lot bigger and harder + more expensive to fix. The pre-emptive job shouldn't be too much work, but only as long as you catch it before something fails & tears other things apart.

There's quite a number of threads and a good deal on information on this forum regarding this problem, and both the pre-emptive reinforcement and the post-failure repair... a search should bring it up. And I'm happy to help more if I can - PM me.

Best of luck with it.
 

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check it out from the inside, you can install an inspection port in no time

this is pretty common on older boats, the best thing to do is to reinforce the step and make sure you don't have any leaks
 
So I put in a couple 4" inspection ports to have a good look. It all seemed ok on the inside. The wood doughnut felt solid and the bonding stuff between the wood and the mast step was intact and solid. I tap checked the outside and inside real well and no signs of debonding or sponginess. I'm in the process of cleaning it up and laying down some reinforcing fiberglass. I'll post some pictures when I'm done, for anyone interested.

Maybe it's fine after all? I wonder if it's due to pounding into the waves. The boat can pound down relatively hard sometimes when sailing up wind in rough water. Maybe a bit of deformation from this pounding? I plan on sanding off the hull paint and giving it a new coat this winter, so that'll give me a chance to lay down a couple layers of fiberglass on the outside for good measure.
 
The boat got very hot at some point and "post cured" the polyester resin causing it to shrink. This happened to my laser which was very new at the time. The "donut" and the deck reinforcement blocks(also plywood) telegraph thru the gelcoat.

If you go into a boat yard and find a large hull that is painted black or dark blue you can sometimes see the actual fibreglass fabric pattern. Good quality custom boats are "post cured" before final fairing and painting to prevent this problem. It can happen with both epoxy and polyester boats.
 
Thanks for that explanation, Ahab. Sounds plausible since there doesn't appear to be any obvious deterioration. My boat sits outside all year (only covered during the winter), usually upside down on a rack, and so it can get a lot of sun/heat during the summer. I've been thinking about getting a cover, mostly for the bird sh*t, but maybe it wouldn't hurt for some sun protection too.

Purely coincidentally, after getting ready to leave the club this evening, the sun was just right on the top side of the boat, and I could see lots of little bulges that I've never seen, where there's obviously wooden backings like at the traveler side brackets, and such, so this "post curing" seems to be all over.
 
I built a custom 42 foot epoxy/glass racer with a friend. Before painting we built a tent and heated the whole boat up to 49 C(120 F) for about 12 hours. This is refered to as post curing. It causes the epoxy to go thru its complete cure thereby stopping all future shrinkage.

I've seen it happen in several Laser's. Usually because they are left in full sun with the plug in and the inspection port closed. The inside of the boat would get incredibly hot. Once its happened there is nothing to be done to fix it. It shouldn't affect the strength or anything like that. Atleast the styrene smell will be gone.
 
this is where i would do the inspection the other way so basically i would cut that cracked section out of the hull to get in to see the mast step and whilst you've got it open there's no harm in re-enforcing the bottom of the doughnut and the deck joint too - I've repaired a few recently that have worn through at the top of the pot so if i can get in i reinforce that too otherwise i just lay glass to the inside of the pot to build it back up. and then just make a patch on a piece of polycarbonate drill a hole or two through it and put some string through and then epoxy the patch to the inside of the hull and pull the string so that it holds the patch tight whilst it sets then cut the string away (use nylon string) and then build back the glass to the hole and finally gell basically you should end up with like a sort of H structure a patch on the inside with glass mat coming through the hole and then more glass mat overlaying the outside with gel on top this is a much easier way than cutting a hatch in the deck because the deck pattern is a bit of a pain to repair there are ways but repairing the hull is easier.
 
I have the same problem as Martin23. My old (1971) Laser sat on a trailer outside for several years and was kept dry, so I don't expect to find rot, but I can really see the outline of the doughnut and block in the gelcoat. Also, I've noticed a blister on the hull that I never saw before. Could this be the same problem of "post curing"?
 
I have the same problem as Martin23. My old (1971) Laser sat on a trailer outside for several years and was kept dry, so I don't expect to find rot, but I can really see the outline of the doughnut and block in the gelcoat. Also, I've noticed a blister on the hull that I never saw before. Could this be the same problem of "post curing"?


The transfer of the plywood block shape to the hull bottom happens to almost all (99.9%) Lasers. Some will say they even come that way from the factory ;) The post curing is the reason.

A hull blister is entirely different. That's water trapped between the gel coat and the rest of the laminate.
 
Sun, no cover = uv degradation = eventual osmosis.
Sun penetrates a couple of hundred feet of the pacific, it only penetrates down two layers of human skin ! Amazing.
With grp, there's no melanin so the uv penetrates right through and reacts with the polyester, the result is the polyester chemically produces a vinegar like substance.
This liquid forms in pools or bubbles, the strands of glass are left but the resin turns to mush eventually resulting in weakened layup.
You can if you wished, pop these bubbles allowing the area to drain and dry, refill and touch up. But likely it will return close by
 

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