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Cracks along the bulkhead

mihaso

.
Apr 24, 2017
25
Oday 25 Montreal
Hi everyone,
I noticed a bunch of cracks along the bulkhead, starboard side, see the photos.
I am not sure if they were there before, or if they appeared suddenly.
But I only noticed them after a few hours of sailing, and some pounding in 10-15 knots and 3-ish foot waves. Shouldn't me more than the boat can handle.
Any idea what kind of stress would cause this type of cracks?
O'day 25 1975
Thank you

b2.PNG
b1.PNG
 
Jan 1, 2006
4,489
Slickcraft 26 Greenport, NY
Note that the crazing is under the chain plates. My guess is that the boat was oil canning a bit and that's a likely spot for the laminate to bend a little. Gel coat doesn't bend so much so you get crazing. I don't think it needs a repair. I wouldn't be surprised to learn that most 45 YO boats would have a bit of this. I don't think the location on the topsides is subject to very much water intrusion. Take it easy on the old gal!
 
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mihaso

.
Apr 24, 2017
25
Oday 25 Montreal
Thank you,
I hope you're right, but I'll do some exploratory sanding just in case. The boat goes on the hard soon, the season is ending.
Yep, she's an old girl and I'm a new sailor. I can never tell how much she can take until I try it :)
 
Jan 1, 2006
4,489
Slickcraft 26 Greenport, NY
Ask around about the exploratory sanding. How are you going to refinish it?
 
Oct 22, 2014
11,365
CAL 35 Cruiser Portland OR, moored EVERETT WA
You have 2 sides to the hull.
  1. What are you seeing on the inside?
  2. Do you have a tabbed bulkhead and are the tabs still solid?
  3. How tight is your rigging?
  4. Did it happen on both sides?
  5. Was it there before you got the boat?
Our boats are sturdy girls but they sometimes like a little soft touch. I would not go crazy sanding right off the bat. What are you looking for in the sanding?
 

mihaso

.
Apr 24, 2017
25
Oday 25 Montreal
On the inside I have an insulating cloth. And since the main problem seems to be covered by the bulkhead, I'm not sure I'll be able to see anything going that way. There's also cabinets so there would be a lot more work going that way.
The bulkheads were fine but I didn't check them well after discovering the cracks. One more thing to check. But I'm sure they are fine.
The rigging is 10-15% of breaking strength. I have a Loos gauge, I just followed their instructions. They're pretty foolproof.
The crack is just on one side. The dock side for that matter. Though the fenders were set correctly. I don't know when the cracks appeared, they definitely weren't there at the beginning of the season.

On the other hand I have some other scratches, not cracks, to fix this year. I thought I'd order some paint and kill two birds with one stone....
If there are no structural cracks, I'll just cover it with a layer of west systems 406 / 407 and paint over. The hull is painted. Well, I think it's paint over gelcoat.

I had a similar experience with a big spider crack on the transom, next to the water level. I thought they were surface cracks. I ended up sanding away 1/3" of glass to get rid of all cracks. It's an old boat...
 
Oct 22, 2014
11,365
CAL 35 Cruiser Portland OR, moored EVERETT WA
Be careful. Will be interested in how it comes out. Let us know. Sounds like your have a good grasp of the issue. Let it be surface issue and not something else. ;)
 
Jan 1, 2006
4,489
Slickcraft 26 Greenport, NY
You didn't include the fender info in your first post. Yes, fenders could do that if the boat was hard up against them. Same issue. If the laminate deforms the gel coat or paint over gel coat doesn't and a craze line appears.
 
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ToddS

.
Sep 11, 2017
198
Beneteau 373 Cape Cod
While there's nothing-at-all wrong with an abundance of caution... and digging into this further... given no other related signs of trouble... I'd personally just go out sailing... and maybe see how good I could get it to look in the off-season with a buffer... keeping a watchful eye to make sure it isn't progressively getting more serious. There is a pretty high-likelihood that this is just gelcoat damage, from the hull flexing behind it even just momentarily from one rough wave slap, or one moment of stress on a fender, and nothing serious at all. Just know that you can spend all sailing season chasing all sorts of unlikely-but-possible trouble spending too much time being 100% certain of everything, and spending little-to-no time enjoying your boat. Your boat though... so your prerogative. I don't think it would be wrong to launch an investigation, but I also don't think it would be wrong to "just keep an eye on it" either. The good news is that you have pictures of it, so you can compare the pictures now versus what it looks like over time to see if anything is worsening/changing.
 

mihaso

.
Apr 24, 2017
25
Oday 25 Montreal
Thank you for your input. I completely agree, sailing is better than sanding :)
But my boat goes on the hard in October, and will stay there until May. That's sailing life in Canada. Plenty of time to poke around the boat.
 
Aug 28, 2015
183
Oday 28 St Joseph, MI
Those cracks are in the hull, not the bulkhead. A bulkhead is a wall inside the boat/ship that runs perpendicular to the hull. Next time out sailing, observe the shrouds. When on a port tack, the starboard shrouds should not slacken or stretch or move and vice versa. If the shrouds do flex, tighten all turnbuckles evenly a turn or two and go sailing again and observe the shrouds. Of course this could be caused by the rigging being too tight. Shrouds should be tight enough that there is no slack when sailing. Don’t tighten the standing rigging to that suggested by any of the tension measurement gauges. My owners manual says standing rigging should be just tight enough to prevent slack when sailing so yours is probably the same.
 
Jun 2, 2004
1,761
Oday Day Sailer Wareham, MA
These cracks are due to the bulkheads causing a "hard spot" against the hull. Fiberglass will flex and that is mostly OK, but anytime the flexible fiberglass is stopped from flexing by bearing against something stopping it.... cracks may develop. Some custom-built or higher-end boats were built with a gap between the hull and bulkhead, sometimes a foam strip is placed there to cushion the point of contact, to prevent a "hard spot". In other works, it is basically "normal" for this to happen on older fiberglass boats. Keep an eye on the area to be sure it doesn't get worse, but.......as others have said, gelcoat is not as flexible as the fiberglass lay-up underneath it, and so little cracks (crazing) may appear in places. Again, the hull (and/or Deck) flexes, the bulkhead is preventing that area from flexing, and so crazing occurs. I found the picture below o n the following web page, FIBERGLASS BOATBUILDING: Internal Hull Structures - Wave Train
 

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mihaso

.
Apr 24, 2017
25
Oday 25 Montreal
I was able to check the inside joint this weekend, it looks like right angle joint.
Luckily, I don't see any cracking on the inside, so I think it's as suggested, limited to the gelcoat.
Thanks for your replies.
 
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