Cracks in the bilge

[HermanHunter]

Hello,
I've bought my first sailboat, Hunter 33 1980 Cherubini. She was sitting on the ground for a year. When I looked at the boat, I noticed some surface cracks in the bilge, but at that moment I thought exactly that: they were just a surface cracks, nothing special. But now, one month before taking her back to water I started thinking: strange, the bottom of the boat was freshly repainted before selling with 3 coats of paint. Maybe there was a crack between the keel and the bottom and now it's covered up? The previous owner refused to split the cost of an inspection, so I bought without one, maybe being overconfident that I would notice big defects. I did knocking and used a moisture meter and didn't find anything suspicious except some small spots around couple of stanchions (I practiced in my nearest marina to find wet spots, delamination).

Does anybody have similar cracks in the bilge? Are they normal?

Thanks in advance,
Herman

 

[colemj]

To me, that just looks like what happens to really thick gelcoat if there is the tiniest amount of flexing (normal). It also looks like a newly painted bilge, so perhaps that is poor adhesion. The keel bolts are in excellent shape for a 45yo boat. Have they been replaced? If so, then likely that is just thick gelcoat/paint with poor adhesion.

Mark

 

[Will Gilmore]

From what can be seen in the picture, nothing looks alarming. Those bolt look brand new. It does look like there is a little breakdown in the encased plate of glass or wood under that middle nut and washers. If you're nervous, pull them and have a look. No time will be better than now, before she goes back in the water. Remove that top layer, look underneath, repair as needed and repaint.

-Chill Will

 

[Dalliance]

I have similar cracks in the bilge on my ‘82 H30. The boat has been professionally surveyed on the hard three times for insurance and this has never come up as an issue.

The H30 hull thickness at the keel stub is well over 1” of solid fiberglass. On top of the hull is a large metal backer plate (stainless steel I think) the entire footprint of the keel and over it is another layer of fiberglass, less than ¼" thick, some filler in spots and thick gelcoat. That top layer of fiberglass wraps up a portion of each side to the floor pan. I‘m assuming your ‘80 H33 is of similar construction.

I doubt you have any structural issue to worry about there. Worst case I can think of is that there might have been some water from the bilge between the top layer of fiberglass and the metal backer that froze at some point. I store my boat with a half gallon of antifreeze in the bilge over the winter to be safe, though that’s more to prevent the lower bilge pump from ice damage if I ever get significant water accumulation there. I’ve owned the boat since 2006 and have not noticed any changes there other than needing to torque the keel bolts a couple years ago.

 

[HermanHunter]

To me, that just looks like what happens to really thick gelcoat if there is the tiniest amount of flexing (normal). It also looks like a newly painted bilge, so perhaps that is poor adhesion. The keel bolts are in excellent shape for a 45yo boat. Have they been replaced? If so, then likely that is just thick gelcoat/paint with poor adhesion.

Mark

Thanks for your reply Mark!
I don't know if the bolts have been replaced. The previous owner didn't do that, and among all the bills left in the history of the boat there is no such record. They also could have been cleaned with some sort of a rust remover.

 

[HermanHunter]

I have similar cracks in the bilge on my ‘82 H30. The boat has been professionally surveyed on the hard three times for insurance and this has never come up as an issue.

The H30 hull thickness at the keel stub is well over 1” of solid fiberglass. On top of the hull is a large metal backer plate (stainless steel I think) the entire footprint of the keel and over it is another layer of fiberglass, less than ¼" thick, some filler in spots and thick gelcoat. That top layer of fiberglass wraps up a portion of each side to the floor pan. I‘m assuming your ‘80 H33 is of similar construction.

I doubt you have any structural issue to worry about there. Worst case I can think of is that there might have been some water between the top layer of fiberglass and the metal backer that froze at some point. I store my boat with a half gallon of antifreeze in the bilge over the winter to be safe, though that’s more to prevent the lower bilge pump from ice damage if I ever get significant water accumulation there. I’ve owned the boat since 2006 and have not noticed any changes there other than needing to torque the keel bolts a couple years ago.

Thank you for detailed explanation!
Yes, on your photo they look just as on mine.
No worries, then.

 

[HermanHunter]

From what can be seen in the picture, nothing looks alarming. Those bolt look brand new. It does look like there is a little breakdown in the encased plate of glass or wood under that middle nut and washers. If you're nervous, pull them and have a look. No time will be better than now, before she goes back in the water. Remove that top layer, look underneath, repair as needed and repaint.

-Chill Will

Thank you!
I'll think about repairing it. I can try to tighten this middle nut. If it's goes easier than others, then something is wrong underneath.

 

[DianaOfBurlington]

I like what Dalliance said but I would strongly advise using fiberglass for your backing plates. Try to keep large hunks of metal out of the bilge.

I would recommend G10 board. This is an impregnated fiberglass product that is not cheap (but you don’t need big pieces) and is phenomenally strong especially in compression. Plan on a couple of long pieces to catch two or three bolts if possible. Mine pick up two bolts each side and go from the very corner of the bilge to within 5/8” of each other in the center - forming a trough to let water migrate aft to the pump pickup. If you can make one big one and not inhibit water flow, that’s better. Make a pattern and drill your holes. G10 is too hard to lay it on top of the bolt ends and tsp with a hammer. Caution: G10 will dull every tool you use on it. You could buy very expensive German bitts or just a six-pack of cruddy ones.

As with all backing plates in tensile (bolts trying to pull through) make the plates as big in area as possible. You’re not replacing flat washers here. You want stiffness and lamination. If you’re worried about delamination or other damage this is your easiest and safest fix. Then in reinstalling the nuts use new large-diameter fender washers - believe me the G10 will do the rest.

I bedded mine with 5200 to enhance lamination but made sure to put tape on the bolt threads first - because of the 5200 grips them you’ll never be able to remove or adjust the keel again. I’m not sure how important this, but I’m a little OCD so -

Send pics of your set-up pre-adhesive and let’s see what you’ve got.