Dry bridge on keel stepped masts?

[massnspace]

I am in the market for a used sailboat.

High on my list is having a dry bilge. I will install a dripless stuffing box if needed, and fix any leaks.

But what about the mast? Is it possible to stop water from coming in there? Or instead allow it in, and build in a small “mini-bilge”, complete with auto pump, around the base to contain the water and eject it overboard???

Of course a deck-stepped mast would be better, but most boats I am looking at seem to have keel stepped.

Ideas?

[Jim Cate]

^^^^
Quite possible! On our boat we have a shallow alloy dam around the base of the mast with a drain to the nearby shower sump... pumps via the sump pump, obviously. Variations which fit with your particular design are pretty easy to work out.

Jim

[massnspace]

Originally Posted by Jim Cate

^^^^
Quite possible! On our boat we have a shallow alloy dam around the base of the mast with a drain to the nearby shower sump... pumps via the sump pump, obviously. Variations which fit with your particular design are pretty easy to work out.

Jim

When you say “alloy dam” you mean aluminum?

And is your bilge completely dry?

[Jim Cate]

Originally Posted by massnspace

When you say “alloy dam” you mean aluminum?

And is your bilge completely dry?

Sorry to be unclear: yes, aluminum! Only about two inches in depth and the drain is 1/2 inch tubing about six inches long overall. This has proven quite adequate to keep up with the rain that gets down the mast.

And yes, the bilge is dry... except for unusual events like raw water pump seal failure and occasional inputs from burping the shaft seal or getting a bit of grit blown into the seal when trying to back out of a grounding.

Jim

[Russ]

Only metal boats have truly dry bilges
Trying to plug all the mast holes is a tough task but not impossible. Also you need a really well made mast collar at the deck. Lots of wide mast tape plus a rubber inner tube wrap over that and canvas outer cover.

[Jim Cate]

Only metal boats have truly dry bilges

See the post just before yours for a differing opinion.

Metal boats have t he same water entry points as other constructions, and how well all those points are addressed determines the dryness of the bilge. (Of course, traditional carvel planked timber does have a few (!) extra entry points and is not included in my statement above).

Jim

[Kettlewell]

The only boat I've ever owned with a dry bilge was an epoxy/ply catamaran. There were no through hulls below the waterline and no engine shafts, and the bilge was split up into multiple compartments with bulkheads up to floorboard level. We had a deck-stepped mast. Even then, occasionally one compartment or another would get water in it from something leaking above, spillage, or a leaky water tank. Very, very difficult to have truly dry bilges. However, ours were dry enough so we stored things like tools and cans of food down there. Still, I would say if you have any through hulls at all they must be marelon plastic types. All it takes is for one head malfunction or a tank to leak and you will have a wet bilge, so prepare for that in mind and have a way to be able to pump out any compartments. On monohulls I have found it best to have everything drain into a deep sump that keeps sloshing water out of most of the bilge most of the time.

[malbert73]

I maintain a completely dry bilge on my 1987 Tartan 40 due to a drip less shaft seal aft, and the fact that the mast is mounted on the cabin sole, just forward of a small, partitioned bilge sump with overflow bulkhead. So I am able to divert the mast water from that sump to my separate AC condensate sump which has its own bilge pump.
Complicated to describe but it’s well worth it- as my keel bolts stay dry 99.9% of the time

[Russ]

Metal boats have no fasteners penetrating the deck for cleats, life line stanchions, chain plates etc etc
Most importantly there is no hull to deck joint
The hull is a single solid welded structure
All those things mentioned are welded to the deck
Recall Chichester was plagued with deck/hull joint leaks
The only penetrating holes are the exhaust , the mast and the single through hull to the sea chest ( yeah another thing most plastic boats don’t have rather a plethora of above the water line holes everywhere )
Whoops for got the bilge egress