Keel gap normal? Best fix?

[RLKelly]

I've heard mention that this gap at the aft of the keel is "normal". I noticed it upon haul out this year on our 351. The boat is new to me as of 2017 and I did not notice, but also didn't look for, this gap last Fall. It compressed out of existence once the boat was placed in it's cradle, and I watched the hull flex to absorb the keel a bit and close the gap.

I have not - but will check my keel bolt torque values. Any suggestions on those would be appreciated.

My plan would be to have the yard lower the keel off it's blocks in the Spring to open the gap, and leave the boat in it's cradle. Then - I'll clean and prep the area and fill the gap with 3M 5200, allow at least a week to cure and launch the boat for the summer.

If there's a better approach, or if this gap suggests a more serious problem - any insight or advice would be most appreciated.

Thanks,

RK

 

[Davidasailor26]

The fact that it opens and closes as the boat takes and unloads the weight of the keel doesn’t sound great to me, but I’m no expert. I’d start by checking the backstay tension to ensure it’s not unnecessarily deforming the hull. The fact that the gap opens up when the keel is hanging makes me wonder if there is some separation between the hull and grid allowing for the flex. Attached are notes including the Beneteau keel bolt torque specs for reference.

 

[RLKelly]

I have to agree that I didn't enjoy watching the hull flex like that - but not sure how abnormal that is for this model (grid and hull construction).

Back stay tension is something I pay attention to occasionally over the season and it's not abnormally high. No one else works on the rigging.

Thanks for torque specs! Any idea which bolts are actually used on a 351??

RK

 

[Bluenose]

Been around boats and keels a long time - you should have this looked at by a professional. Maybe an engineer or marine architect. Something is amiss. It's possible that dropping the keel and tightening the bolts may work......

 

[BrianRobin]

I replaced the keel bolts on my 351 a year or so ago. When your boat is on the cradle and your keel is compressed , check your aft keel bolts, they should square washers under the bolts heads. If they are not loose when compressed, you've likely got bigger problems. The bolts aren't that long, 70mm x 20mm dia.

 

[Bluenose]

You do not want to end up like Cheeki Rafiki. If you are unaware of this boat, Google it.

 

[Mechone]

I also replaced my bolts, tighten up all your keel bolts and fill the gap with 5200 as they did at the factory. I upgraded my bolts from 8.8 to 10.9 . I also welded up 1/4 inch s/s plates with guset's all around joining the 2 bolts together instead of 2 separate washers and a large plate on the middle single bolt and a large plate on rear 2bolts. I used transfer screws to mark the hole locations. The bolt tightening specs are in the manual.
On the hard is your floor pushing up?

 

[RLKelly]

Thanks for all the insight folks - appreciated.

@Mechone, yeah - the floor deflected a wee bit for sure - is that good or bad? I noticed it when I went below upon first being put on the hard - the only tip was the wood floor plates crunched a bit as the sand between them had shifted. No visible deformation to the hull when viewed from the outside - and no noticeable deformation from inside either.

We'll be up to check the boat in a few weeks and I'll check the relative tightness of the aft bolts.

Thanks,

RK

 

[Mechone]

Check all the bolts , a 3/4 drive breaker bar works great . I can tell by your photo ,if there was a matrix problem the keel would be pushing up at the back not flat. I'd almost bet your bolts are not tight. You may want to dig out each side and get some 5200 quick dry in there before you tighten the bolts.If you don't you could spring a leak at keel joint