About Triton Bilge

Hello,

I had read many threads about the Triton structure, but I am surprise by the following fact : il seems there are NO floors between the bottom of the bilge and the cabin sole. Is it true ? I had think that the role of floors was to strengthening the keel ...

Thank you for yours advices.


Jacques

 

Not all of us have read the same threads I assume.

Could you tell the ignorant here what kind of vessel you are referring to?

 

The purpose of floors is to distribute loads.

They tie the weight of the keel, which is attached to the keelson, to the planking of the boat.

The planks are further tied together with ribs.

When I say loads, I mean two kinds.

First and most obvious is tension. The weight of the keel is going to tend to pull the bottom of the boat off, straight down. with wood planked construction, this would tend to open the seams at the lower planks. This tendency gets even worse as the boat heels. Now you not only having the weight of the keel trying to pull itself off, but now it is twisting itself off, putting all the tension load on the high side. With wood planking the seams on the high side are going to end to open up. With GRP construction, the material on the low side is going to tend to buckle.

The second load is bending. Since the weight of the keel is anywhere from 1/4 to 1/2 the weight of the boat, the hull material is going experience a lot of over pressure, meaning pressure from the bottom pushing up. This is especially true with narrow, deep, slack bilged hulls and wide, shallow, flatish hulls. In both cases, the hull material has little arc across the bending moment.

Now, supposing I want to build a traditional hull of, say 35 ft. It is going to have a long, shallow keel and the lower part of the hull is going to be made of thick, seamless material, such as GRP or steel, so it can bounce off unmarked reefs. Suppose, also, that this hull has a healthy rocker along the centerline. Now, due to the thickness of the material and the shape of the bottom, it is more than equal to the two loads I just mentioned. To save weight and to facilitate easy cleaning of the bilges, I might be able to dispense with the floors.

With GRP, I would have to make the keel shell a continuous part of the hull and put the ballast inside it.

With steel, the keel would be made of the same material and I would hire a really good boat welder.

Either way, I would run through my calcs at least three or four times to make sure this is gonna work.

With aluminum, I wouldn't even consider it.

 

Triton

The boat subject of my question is the Carl Alsberg Triton, built in GRP ; the exam of few photographs show the interior of the bilge ... empty, i.e. without floors.

 

Floors allow attachment of the keel (though some Tritons had glassed-in keel ballast). They also much stiffen the boat's underbelly (though the Triton was so heavily laid up it probably needed no reinforcement). Lastly, they allow a cabin sole to rest on something level.
In any case, while I've never looked into a Triton's bilge, I can't imagine the boat was built without some floors, as the bilge was deep and the cabin sole had to sit on something, let alone the other issues mentioned.

 

Structural floors are not are not always necessary in GRP building methods. For that matter they aren't always necessary in wooden or alloy building method either. The Triton is a well engineered laminate, though a bit heavy by modern standards, well regarded none the less. Many yachts have no structural floors and survive quite well.