Have found a nasty soft spot in the aft cabin on our 361

[Sean&Lou]

G'day Sean here with a first time post. Have enjoyed reading all the great posts. But now have a reason to post myself. Usual small job that grows into something colossal, installing a nice new electric toilet as part of the upgrades ready for cruising, I dropped a washer whilst installing the new "y" valve so lifted a floor board hoping to find it, but found water instead - normally pretty dry bilges on Siga Siga. After finishing the install I mopped up the water from all sections around the centre of the boat, to my disbelief the sea water ran straight back in over a ten minute wait but stayed at around an inch deep across the centre sections. Thinking that the refilling was maybe a bulkhead discharging to raise the level I mopped again and again, for the next couple of hours. No luck though, level stayed at an inch, monitored over the next four hours - no change. Of course automatically thought that my toilet install would have caused the issue, but no leaking valves or pipes. So a restless nights sleep gave way to an early morning revisit to the marina where all floor boards were removed, every inch of hull that was available for inspection was studied and alas the entrance way to the aft cabin revealed a soft spot which under pressure gave a resounding slush sound. Incredible to believe as the rest of the boat is solid, quite a mystery also how the water is making its way to the centre of the boat. Now for my questions - anyone had this before, what sort of a job is it to repair.
Thanks in advance,
Sean.

 

[xsiddr]

Two or three cabin model?

 

[Paul Mermelstein]

Need more info to help you diagnose the problem over the internet.
Where exactly is the soft spot?
Is the soft material wood, fiberglass, or what?
Is the water salt or fresh? Clear or discolored?
Can you see any water trail leading to the area where you have standing water?
When did last see that the bilge was dry, or when did you first notice this problem?

 

[Picflight]

Welcome.


Good to post pictures for a clearer picture.

 

[Sean&Lou]

Benny is a two cabin model, water bubble is in the aft cabin entrance fibre glass floor. The area is around the size of a dinner plate photos just give an idea of the area from the shadow. Clear salt water, no evidence of a trail, bilges have up until now been dry. Problem was first noticed two days ago, boat has not left the marina for over a month, so no impacts.
Sean.

 

[Captn TJ]

Benny is a two cabin model, water bubble is in the aft cabin entrance fibre glass floor. The area is around the size of a dinner plate photos just give an idea of the area from the shadow. Clear salt water, no evidence of a trail, bilges have up until now been dry. Problem was first noticed two days ago, boat has not left the marina for over a month, so no impacts. Sean.

I assume from an earlier post that this is seawater vs fresh? If fresh I assume that there is a tank under the aft bunk? If salt lift the bunk and track back to beginning of the liner

 

[Sean&Lou]

Definitely salt water, water tank is under the bunk but viewing down past tank to hull appears dry. So would you know if the entrance floor to the cabin is a PVC liner applied after construction.
Regards,
Sean.

 

[peoples1234]

Could you have pierced the hull when you installed the Head? I know in the 321 it is possible if your screws are too long. If it was one of the back bolts close to the waterline then it is possible that it stops at 1 inch of water because the pressure is equalized. With a lag screw in it, it would be a relatively slow leak.

 

[Paul Mermelstein]

Definitely salt water, water tank is under the bunk but viewing down past tank to hull appears dry. So would you know if the entrance floor to the cabin is a PVC liner applied after construction.
Regards,
Sean.

Beneteau does use liners, stringers etc on the inside of the hull. So water could collect there, sandwiched between the two layers.

How does the engine compartment look? Any salt water on the floor pan, or is anything wet in there? Sometimes the vented loop springs a leak.

If the engine compartment is dry, and this problem occurs when ALL thru-hulls are closed, explanation above about long lag screws sounds plausible. If so, maybe it's be time for a haul out.

 

[Captn TJ]

Other areas : the shaft log, the hull swim platform joint (covered by the rubber strip) and if you have a locker in the swim platform then check the drain.

 

[xsiddr]

We live on our 361, 2 cabin, laying in aft cabin as i write this. There is definitely a space between the floor and hull. There is a limber hole in the flooring and this connects to the hull under the liner throughout the boat. The water could have come in from many places. First thing is to siphon the water from the hull space through the limber hole in the main salon. You may get several gallons of stinky water from there. Your boat likely leans to starboard and the water has been collecting there for God knows how long. The fiber glass is likely not protected on the underside and has now gotten squishy. I would get the water out, watch if the problem goes away and put the wood sole back in place. It doesn't impress me as being in a structurally sensitive area. Once it's dried out, it should stop any progression. The wood sole sits on the elevated edge, so no weight is on the soft spot.
Good luck
Bob s/v Kaylic

 

[Sean&Lou]

Thank you to all for your suggestions and ideas. I have managed to borrow a flexible pencil camera so will be able to investigate tight spots. Is it possible to find construction details on line, I have been searching but to no avail. Do all voids drain to lowest point of the hull.
Sean.

 

[Tejas]

As for all voids draining to the lowest point in the hull, that was not the case for our 36.7. You might not even be able to rely upon the limber holes being low enough to drain well or even not having obstructions.

Here is a link describing the problems and methods for removing the water that might be helpful.

http://beneteaufirst367.org/forums/upload/index.php?showtopic=463