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**HappyMdRSailor** · 05-10-2014, 06:41

Quote:

Originally Posted by UNCIVILIZED

To explain a bit of how some boats are built, & give an explanation to my earlier post, there's another long'un below. My apologies for taking up so much screen space, & or if I oversimplified things a touch. But in my travels, I've found that more often than not, it takes a bit of explaining before folks understand the how & why behind what holds boats, etc. together.

On a big catamaran, the entire cabin structure is essentially part of a monocoque "box beam" which both carries/distributes the stresses of connecting the hulls. In addition to being a major supporting member of the base structure which handles the loads from the rig.

The cabin is at the center of where the shrouds come together, so you have both big vertical & horizontal loads from that alone. And with some types of rigs, the vertical loads can be greater (sometimes by multiples of) the boat's weight. Not necessarily quite so much with a cruising cat as say with a racing Maxi mono, but... let's just say that those wires which hold up the mast are big for a reason. And that the loads which they both generate, & carry, have to be resolved by equal forces & structures elsewhere.

As to the cabin's roof, you have the loads from the jib sheets being resolved by the cabin top & how it connects into the hulls & the monocoque structure mentioned before. And on a boat that size, jib sheet loads aren't small.

When the designers/engineers are designing things to handle these loads, in a boat like this, often enough it's by adding extra glass cloth or carbon into directional load carrying pathways (as well as omnidirectionally). The same as you can see the heavier load paths in a sail, by following the densities of the patterns of the tapes/extra fibers in a tape drive/laminated sail.

So if you happen to cut, or take a chunk out of one of these areas of extra reinforcement, bad & very expensive things can happen (as semi-alluded to in my earlier post). Which is why I strongly recommended speaking with the boat's builders, prior to reaching for the power tools.

It's kind of like if you've ever pulled out the headliner in a car, & can see where the extra reinforcing beams are welded to the inside of the car's metal skin. And in some cars these beams cross over the areas where the driver & passenger sit. Which is why in cars of such construction don't, and cannot have sun roofs. It just doesn't work structurally. And were you to go ahead & put in a sun roof despite this, the whole car would be as flexible as a slinky when driving down the road. And at a certain point, the other structural metal would become fatigued enough that the vehicle would bend sharply under the floor, until it's underside was grinding it's way down the pavement at 60mph.

AKA, something to avoid in a $1,000,000 sailboat, upon one's lives may depend.

Oh Darn...

I was already on my way down with my Sawzall to help cut giant holes in the coachroof... We bought some angle brackets from Ace Hardware to connect the coachroof skin to where we cut out the boxed beams...

Originally Posted by HappyMdRSailor

I don't see anything crazy load wise there on your boat, but the warnings given would make me do some research to be sure...

**weavis** · 05-10-2014, 06:49

For me.,

If Im spending serious money and a vessel does not meet the basic criteria in its design, I go look for another vessel.

This has got complicated from the word go, and if..... if the enhancements dont work.... you have an expensive vessel plus useless vents.

Delancey · 05-10-2014, 07:15

Um, yeah, duh. The reason why I couldn't remember where I had seen it done was of course because it's on my neighbor's boat. A boat I only look at like several times a day. A newer Beneteau.

The right boat can be hard to find, some people look for boats for years. If everything is right about the boat for the OP, except the ventilation, then I would encourage the OP to contact the builder. Might find you are not the only one to consider these changes.

The windows are not designed to carry any structural loads and your mast will not likely fall down if you add a hole to something that is already a hole in the structure that carries the loads.

Not really that complicated.

Sailingcouple13 · 05-10-2014, 08:21

We have what you are talking about cut in ours.

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AnchorageGuy · 05-10-2014, 10:28

My preference would be opening hatches in the coach roof instead of in the window/ports. This will allow heat to escape and fresh air to funnel in. With proper size and placement, I doubt you will have any structural issue but a discussion with a marine builder of your vessel or a like one should confirm. Chuck

Stu Jackson · 05-10-2014, 10:43

Good advice. I would avoid Lewmar ports. Our Catalina 34s have six of them, and have created nothing but headaches for their owners, with leaks at the frames, the seals on the opening part and in the O rings for the handles. I'm glad my boat was built earlier than those, and we have Beckson opening ports throughout.

There are a LOT better opening ports out there on the market.

Beckson if you're not going offshore, New Found Metals if you are.

Good luck.

Cheechako · 05-10-2014, 10:59

You could put one or two hatches on the coachroof. I don't like the idea of cutting the plastic windows to put a hatch in.... an stress riser will make them crack even easier than they currently do. My Lagoon had one opening hatch at centerline under the boom (as a front window... not on top) and that made a world of difference.
With that forward hatch open, and the companionway slider open the wind would roar thru the salon....
The Lagoon had overhead hatches in the forward staterooms also, with those open and rear stateroom port open the wind would run thru each hull very well also.

Sailingcouple13 · 05-10-2014, 17:23

We have 4 that open and 4 that do not in our roof. Taken at night. To keep to much sun out we have a cover on top. Will take pictures in am to show.

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**HappyMdRSailor** · 06-10-2014, 08:00

Quote:

Originally Posted by Sailingcouple13

We have 4 that open and 4 that do not in our roof. Taken at night. To keep to much sun out we have a cover on top. Will take pictures in am to show.

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Oh man!

I'm sayin'... with the right reflecting cover over the coachroof... and some dancing colored lights... That is one SUPERB setup for a disco room!

**HappyMdRSailor** · 06-10-2014, 08:00

Quote:

Originally Posted by AnchorageGuy

My preference would be opening hatches in the coach roof instead of in the window/ports. This will allow heat to escape and fresh air to funnel in. With proper size and placement, I doubt you will have any structural issue but a discussion with a marine builder of your vessel or a like one should confirm. Chuck

+1 !

Sailingcouple13 · 07-10-2014, 01:10

You Should See The dance POLE

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Southern Star · 07-10-2014, 08:10

Wow, there certainly is a lack of ventilation in the saloon as it now stands! I'm with Anne on this one, although I also believe that even if there is a slight curvature in the area of the central opening in the front portlight, a hatch could be installed. Regardless, I suspect that you will want to modify the opening in order to precisely fit a hatch and to leave a lip for the remaining fixed ports to the side. If you are already doing glass work, there is no reason that the area around the hatch cannot be modified so as to eliminate any curve. Since the verticle framing will now (or should now) be somewhat bigger and thicker, it should be stronger than the exisiting structure.

In addition to fixed forward portlights, my boat has two forward facing Lewmar 60 series ( 22 5/8" square) Ocean Hatches in that area and they provide tremendous ventilation when at anchor or underway in good conditions. I also have two smaller overhead hatches that open to the sides (helpful if docked without the bow into the wind) - although they have to be closed when tacking in order to avoid fouling the sheets.

Brad