B311 forward bulkhead cutout.

[tombravo]

I want to make the forward cabin entrance larger than the doorway Beneteau designed. I have removed the door but I want make the opening wider by about 11 inches on the starboard side and 7 inches on the port side. The standard opening is displaced to starboard (there is a hanging locker to port in the berth). I am NOT going to cut the bulkhead margins where they meet the hull or deck. The bulkhead is single layer 1/2" wood. The hull is solid fiberglass with a liner and the deck is cored. The deck stepped mast with post is more than 2 feet abaft the bulkhead.
My question is: Is this bulkhead a structural component and if it is can cutting out a larger hole in it excessively weaken it? Has anyone made a larger opening in this bulkhead?
Its Saturday. I'll call Beneteau on Monday but I imagine they will (and I guess should) say 'don't be cutting on those things'.
Thanks

 

[Mechone]

I think you answered your own question , the bulkhead is structural and has been engineered for horizontal and vertical loads ,and is where the sling goes when hauling the boat out . Personally I would not touch it or even buy a boat that had had it modified. Remember these boats flex ,yes the hull is solid glass and the matrix is glued in you would hate to weaken the bulkhead and upon lift out with loads the bulkhead crack or while sailing in rough water.
Beneteaus are known for not being built the strongest (glued in matrix) and there have been many failures, making it weaker is not good and your insurance might agree that you modified the boat and not cover you if something happens.
I even close all doors when having the boat lifted in or out to help spread the loads

 

[tombravo]

I think you answered your own question , the bulkhead is structural and has been engineered for horizontal and vertical loads ,and is where the sling goes when hauling the boat out . Personally I would not touch it or even buy a boat that had had it modified. Remember these boats flex ,yes the hull is solid glass and the matrix is glued in you would hate to weaken the bulkhead and upon lift out with loads the bulkhead crack or while sailing in rough water.
Beneteaus are known for not being built the strongest (glued in matrix) and there have been many failures, making it weaker is not good and your insurance might agree that you modified the boat and not cover you if something happens.
I even close all doors when having the boat lifted in or out to help spread the loads

Thanks for the reply. After posting I read up on it more and was coming to that same conclusion. Maybe making myself shorter, thinner and more flexible would be the way to go instead.

 

[ron2photo]

I have a 2016 Beneteau Oceanis 38. That year, and maybe other years, the bulkhead was an option and my boat came without a bulkhead. We are planning to put a bulkhead in but are putting a 2018 model year bulkhead. It has a double door arrangement. You should inquire about switching to a double door bulkhead.
The bulkhead can not be a structural component because it left the factory without it and some folk just took them out for more room.

 

[Davidasailor26]

I have a 2016 Beneteau Oceanis 38. That year, and maybe other years, the bulkhead was an option and my boat came without a bulkhead. We are planning to put a bulkhead in but are putting a 2018 model year bulkhead. It has a double door arrangement. You should inquire about switching to a double door bulkhead.
The bulkhead can not be a structural component because it left the factory without it and some folk just took them out for more room.

The 38 and some related daysailor like designs are pretty different from traditional designs in that sense. Traditionally the bulkhead is definitely a structural component for hull strength, chainplate anchorage, or both. The 38’s hull is presumably specifically designed to not need that support. Much like how a convertible car can be designed to stay rigid without a roof, but that requires extra strengthening of the rest of the frame. Even in the case of the 38 it does look like there’s some periphery framing to give extra strength -

 

[CapitalistSailor]

I agree with the previous posts that the bulkhead is structural. The B311 hull is pretty light and needs the stiffening the bulkheads provide. I am saying this based on observation and not because I am familiar with the technical details of Beneteau's/Finot's design. If you decide to go ahead with making the doorway wider by removing material from the bulkhead, you will need to beef up the bulkhead or provide additional structural support another way.

I don't know if you race, but if you do please be sure to inform your handicapping organization if you have modified the boat by removing some of the stock interior. In no way am I implying any ill intent here, but there have been enough people caught intentionally cheating by gutting their boats' interior and making the boats significantly lighter than what's on their handicapping certificate. Many committees and competitors are touchy about the issue.

 

[tombravo]

For what it is worth, I talked to a senior customer rep. at Beneteau USA and he said that, though he was not technically familiar with the 311 that his guess would be that removing part of the bulkhead while leaving at least 6" of material where the bulkhead is bonded to the hull would be reasonable (not his exact words). He also thought lifting the boat in a sling would alright but he was concerned about storing it in a cradle. I'm in the PNW and leave the boat in salt water all year. There is about 3 inches of material between the top of the doorway and the deck without any stiffener or extra thickness. This bulkhead is approx. 1/2 inch thick wood so he reasoned that it's structural importance is relatively low compared to true structural bulkheads that are twice as thick or more. He did say that ultimately he could not advise me that it would be okay to cut material from the boat.
I have race crewed on various boats but I don't race this one (unless of course when I'm out cruising and any other sailboat comes within a mile of me).
I've decided it would be better to improve my gymnastic techniques and maybe remove material from my almost 7 decade old body rather than the bulkhead.
Thanks for all of your inputs.