Trimaran Interior Space vs. Bulkheads

[CptBrightfame]

Ahoy there! This is my first post and first* boat design.

The boat in question is a 42 foot tri with a center-hull beam of 12 feet. The vessel has front and rear bulkheads, which, despite being undefined surfaces in Free!Ship, seem to be taking up a considerable amount of space. I am looking to utilize the interior space to the same tune of efficiency as the Ericson 32 II I grew up sailing; with the intention/capability of blue-water circumnavigation for two permanent live-aboards and up to six max compliment. That boat had neither akas nor bulkheads, and the "trimaran interior" google search results are pretty but uninformative, so I'm looking for spatial use and arrangement ideas.

In the bow I've raised the floor to become the front bunk/"v-berth" and provide storage and bilge access. The most likely part of the boat to be holed should be accessible, no hang-ups there. The forward bulkhead separates the front cabin; the bulkhead hatch is visible on the port side. I'll stuff as much storage space in here as I can but it's basically used up.

In the center cabin, I've placed the head against the rear bulkhead for maximum headroom and minimal movement. In the picture, it's semi-transparent and visible on the port side. This seems like it can't move, based on the general size of a toilet, sink, shower, and the upper deck and deckhouse wall joint intruding into the space (top deck tumblehome). Opposite of that are the remains/intentions of a sail locker; nobody wants to bunk across from the head, so this seems a good use of the space.

It basically goes pear-shaped after that. Tentatively, I've placed the galley countertop attached to the fore wall of the head, to house/give access to freshwater treatment and to centralize the plumbing as much as possible. This could be rotated ninety degrees so that the back edge touches the hull and the cook faces the port ama, but restricts overhead space (deck/tumblehome overhead) and places the galley inconveniently and unappealingly in front of the forward cabin hatch. Not that I need my head OVER the stove, but smashing my head into the tumblehomes is going to make me hate doing dishes. The space between the forward hatch, galley, and between the hull and centerline is proving difficult to use effectively. The tumblehome-to-centerline space affords a fairly spacious bunk but most transverse bunk options don't seem to fit (I could sleep someone overhead?).

The aft compartment, behind the aft bulkhead, will house a radio/nav station. I may be able to squeeze an extra bunk or two in here, but it begins to strain passenger storage and comfort to do so; the length between the rear bulkhead and rear deckhouse wall is about 5.5 feet, only comfortable for my shortest friends.

Thanks for taking the time to read, I look forward to your suggestions and hope to see you out there!

 

[montero]

It seems that the bulkheads are critical to the strength of the boat. You can always cut them aircraft-style, leaving only the bulkhead circumference and reinforcing them accordingly.

 

[CptBrightfame]

It seems that the bulkheads are critical to the strength of the boat.

I don't know that they are necessary but that is why I have chosen to include them, as well as flood management. They are presumably over-kill, especially given the size of the akas.

You can always cut them aircraft-style, leaving only the bulkhead circumference and reinforcing them accordingly.

I assumed that the remainder of the stations (non-bulkhead) would be built this way in my inexperience; that is where I would begin fabrication as an amateur. If you mean to say that using only the current bulkheads as "aircraft-style" would be sufficiently strong, that would free up a lot of space.

 

[montero]

Flood management in the living space is a different story . SEAftey first .
Or not. It depend.

 

[CptBrightfame]

Flood management in the living space is a different story . SEAftey first .
Or not. It depend.

I think they exist at the intersection of available skill and expected survivability.

 

[fallguy]

Your GA is extremely difficult to understand.

Ideally, it would be done in 3 perspective drawing or at a minimum top view with headroom noted.

Out of the box, the head/shower and dish/stove are best across from each other where headroom is precious short. Seating areas are best where headroom is graduating downward, because a seated person doesn’t need it.

 

[cando2]

How wide is your main hull at the waterline? Have you studied the structure of current trimarans around that length? I get the sense, Cpt, that you are very new to trimaran design, and that it may benefit you to peruse the designs of actual multihull designers. Also, you may find like most world cruisers that catamarans make for a better platform to cruise on.

 

[gonzo]

Ask the designer. He is the one that did the structural calculations and determined the location and size of the bulkheads. Accommodations are secondary to structural concerns.

 

[CptBrightfame]

Your GA is extremely difficult to understand.

Probably, I don't know what that is.

Ideally, it would be done in 3 perspective drawing or at a minimum top view with headroom noted.

Free!Ship's input method is 3-perspective. I did not included it because it does not paint a very accurate depiction of the use of space. I'll try to attach it after this.

Out of the box, the head/shower and dish/stove are best across from each other where headroom is precious short. Seating areas are best where headroom is graduating downward, because a seated person doesn’t need it.

I've placed the head/toilet in the lowest-headroom area (outboard, under the deck/tumblehome) and the shower in the highest-headroom area for this reason; the head/bathroom is placed against the wider bulkhead to accommodate these features. I had not considered placing the galley across from the head/bathroom; this would retain my intention for centralizing the plumbing/water processing and eliminate the dead space caused by the standing room in front of the galley. I'll play with some arrangements regarding that.

 

[CptBrightfame]

Ask the designer.

I am the designer.

Cando2 I am new; this is my first design. It is my perusal of said designers that brought me to this point.

Edit: She's 12 feet wide inside.

 

[CptBrightfame]

Out of the box, the head/shower and dish/stove are best across from each other where headroom is precious short.

I've moved the galley to the starboard side, across from the head, and it makes much more sense that way. The available space between the galley and head and the front bulkhead has much more usable space now; the space that was the galley before can easily become foodstores now (seen with the short wall on the port side in the picture). This also tracks to move the sail locker behind the aft bulkhead and into the "radio room".

 

[fallguy]

GA is general arrangement and you would display it in rasp343; it is too hard for us to translate words in the original post to the GA that should show where fixtures are on the top view at least

 

[fallguy]

GA decently done. But while you are adjusting; just the top view would be good to offer contributors here.

 

[fallguy]

When you do it; you can just put the headroom notations below.

For example,

On drawing S is shower and down below in a key you say headroom 75-72, etc

by the way, this is not the credentialed response, a NA may help you more properly, but they can’t always get too involved; depends on the time available, so I help best I can and willing to accept correction

 

[CptBrightfame]

Labelled as described less height measurements.
Don't worry, nothing credentialed is happening here.