Pearson Triton mast beam bulkhead removal

[Titan]

Hello,

I just bought a Pearson Triton, hull #648 woo! I am in the process of refitting and need some advice regarding replacement of the mast beam; its delaminating from the deck and from itself. I am at the same time looking to rejig the interior layout by moving the head from its location adjacent the V-berth, further aft into a newly constructed (ehem) stateroom. At the same time I would like to remove the bulkhead that is currently integrated into the mast beam and open up the V-berth into a larger cabin.

My question is: if I replace the wooden bulkhead with a GRP reinforced aluminum mast beam of the same size, and carry the load into the keel and frame anchors with reinforced verticals; would this be enough to allow for the bulkhead to be removed without compromising the structure?

Thank you,

T

[SVTatia]

I don't have a direct answer to your questions, but you need to check this:

Pearson Triton 381 Glissando | Replacing the Mast Support Beam

Main Page:

Pearson Triton #381 Glissando | Restoring, Maintaining, and Cruising a Plastic Classic on the Coast of Maine

[jimbunyard]

Originally Posted by Titan

My question is: if I replace the wooden bulkhead with a GRP reinforced aluminum mast beam of the same size, and carry the load into the keel and frame anchors with reinforced verticals; would this be enough to allow for the bulkhead to be removed without compromising the structure?

T

Possibly, but the design and execution will be critical, especially if you plan on using the boat in any extreme conditions...and those are hard to predict.

From the drawing of the boat on sailboatdata, it appears you want to move the main structural bulkhead aft about 2 feet, out of column with the mast.

While this could in theory be done, would the resulting complications be worth it? If you're not familiar with the distribution of forces in a working sailboat, you'll likely need the resources of a marine architect to ensure you're not building in some weaknesses...

And, just to illustrate, have a look at some of the 'discussion' about just repairing the existing deck beam on a similarly constructed boat...

http://www.cruisersforum.com/forums/...-186039-5.html

[jimbunyard]

Originally Posted by Titan

My question is: if I replace the wooden bulkhead with a GRP reinforced aluminum mast beam of the same size, and carry the load into the keel and frame anchors with reinforced verticals; would this be enough to allow for the bulkhead to be removed without compromising the structure?

T

Possibly, but the design and execution will be critical, especially if you plan on using the boat in any extreme conditions...and those are hard to predict.

From the drawing of the boat on sailboatdata, it appears you want to move the main structural bulkhead aft about 2 feet, out of column with the mast.

While this could in theory be done, would the resulting complications be worth it? If you're not familiar with the distribution of forces in a working sailboat, you'll likely need the resources of a marine architect to ensure you're not building in some weaknesses...

And, just to illustrate, have a look at some of the 'discussion' about just repairing the existing deck beam on a similarly constructed boat...

http://www.cruisersforum.com/forums/...-186039-5.html

[ZULU40]

Originally Posted by Titan

Hello,

I just bought a Pearson Triton, hull #648 woo! I am in the process of refitting and need some advice regarding replacement of the mast beam; its delaminating from the deck and from itself. I am at the same time looking to rejig the interior layout by moving the head from its location adjacent the V-berth, further aft into a newly constructed (ehem) stateroom. At the same time I would like to remove the bulkhead that is currently integrated into the mast beam and open up the V-berth into a larger cabin.

My question is: if I replace the wooden bulkhead with a GRP reinforced aluminum mast beam of the same size, and carry the load into the keel and frame anchors with reinforced verticals; would this be enough to allow for the bulkhead to be removed without compromising the structure?

Thank you,

T

without drawings/sketches this is impossible to answer with even any approximate sense. Generally bulkheads are supporting, kicking them out and replacing with framing entirely possible, but we need to see whats going on

[alley]

You need to worry not only about static loads (mast compression), but also dynamic loads imposed by gusts, waves, etc.

In this case, the bulkhead serves not just as a compression post to transfer and distribute the forces generated by the tension in the standing rigging down to the hull, but it also serves as a stiffener to reduce hull twisting as you're working over/through waves.

In my (engineering) opinion, you need to think long and hard before moving this particular bulkhead.

[Adelie]

You want to make the V-berth long by 2’ by taking out the bulkhead in line with the mast.

The beam that is there has a very short span between the bulkheads on either side. Moment in the beam goes as the the square of length if I recall correctly. I don think you can get away with deleting the bulkheads and making the deck beam deeper.

You could put a deep enough beam down at the hull under the berth but you would need to have a post under the mast down to that beam and knees or partial bulkheads at deck edge with connections down to the ends of the beam.
If you didn’t mind a post in the middle of the berth you could go that way.

[ZULU40]

Id be interested if Pearson produced any other variant layouts on this hull, as was typical with the 365. Different layouts may reveal some possibilities.

Also take a look at the bulkheads and see how well (or not) they are tabbed to the hull. Sometimes some features are more or less cabinetry and not structural at all. Much of the 365 is like this but it was built much later.

It is also true that early in the fibreglass experience there were no known ways of computing the strength, so they built hulls a similar thickness to the wood that plastic replaced.

These days the joke around the marina is, with new boats at least you can tell if f you left the lights on

[crazyoldboatguy]

I own a Pearson Triton - there was an early problem with the support beam that required extra support (metal plates bolted to either side of the existing beam - carried to the door frame uprights) to address the deficiency. We have that on our Triton.

Deck stepped masts require strong support as the compression forces are significant. It’s the reason for the bulkhead and vertical supports as well as the added stiffening of the arching overhead beam. Not to mention the “panting” distortion created while going upwind, which are controlled by the bulkhead contacting the hull and house.

There is a yahoo/Triton group - you could start there to see if anyone has attempted this. In the end, it would be prudent for you to secure the services of a naval engineer/architect to tell you if it’s possible.

My suspicion is you could actually do it - but the overhead beam would be so large in vertical cross section as to take away the benefit from moving the bulkhead.

[navysurfer]

Look Atom, S/V he twice went around world in a Triton, I also owned one and loved it.

[Cadence]

My dumb guess is the mast compression load is distributed to the hull through the bulkhead. Equally distributing the load without it may be difficult.

[Don C L]

First of all, welcome aboard and congrats on a really nice little old boat. First, before you break out the sawzall, I recommend sailing her FIRST and see how things feel the way they are. You may find you may not want to change things after all. It is very easy when getting a new boat to want to personalize it but I recommend holding off. But if you are determined, how about some drawings or pics? I too would echo Jim about getting an engineer’s input. One thing that comes to mind is the stress on the hull at the chainplate(s) is supported by the bulkhead too, so do your plans require removing the bulkhead entirely?

[liquidice]

Originally Posted by alley

You need to worry not only about static loads (mast compression), but also dynamic loads imposed by gusts, waves, etc.

In my (engineering) opinion, you need to think long and hard before moving this particular bulkhead.

Statics and Dynamics. An engineer has spoken. I think this is right. You shouldn’t remove any bulkheads if you want your boat to be robust. It’s like cutting the frame of a car. Why are you moving the head again?

[Don C L]

BTW on my own boat, very much like yours, as near as I could figure, I needed to be ready for it to support up to 10K pounds, though the shrouds will probably break before that. There was some discussion of compression loads in that previously mentioned thread
http://www.cruisersforum.com/forums/...se-186039.html
Fortunately mine managed to come out strong enough, but I'd still like to rebuild it more elegantly.

[liquidice]

Originally Posted by Don C L

BTW on my own boat, very much like yours, as near as I could figure, I needed to be ready for it to support up to 10K pounds, though the shrouds will probably break before that. There was some discussion of compression loads in that previously mentioned thread

http://www.cruisersforum.com/forums/...se-186039.html

Fortunately mine managed to come out strong enough, but I'd still like to rebuild it more elegantly.

Don that was quite a thread! How’s that arch holding up anyway?