why don't sailboats have wheelhouses/cabins?

[TeddyDiver]

Originally Posted by Doug Lord

Sliding watertight doors for pneumatic or electrical operation are approved by the MCA for Large Commercial, Sailing and Motor Vessels up to 80m load line length and will withstand a 4 metre column of water from both sides.[/color][/i]

Unfortunately they are a way over any accepptable weight limit in a recreational boat.. Superyachts might be ok with it..
I'm sure it's possible, anyway for class 2, to make light cabin side doors. Maybe there's not demand enought by the commercial manufacturers..

[Guillermo]

Originally Posted by Doug Lord

Guillermo, found this: http://www.pointeng.co.uk/marinedivision.asp


From the site:

Watertight sliding doors
Sliding watertight doors for pneumatic or electrical operation are approved by the MCA for Large Commercial, Sailing and Motor Vessels up to 80m load line length and will withstand a 4 metre column of water from both sides. A60 class fire rated and non-rated doors are available. Please call us to discuss your requirements.

Thanks Doug.
There are several other sliding door manufacturers for that kind of boats, too massive to be mounted in a forty footer! As far as I know, for the recreational market there are not even category 2 sliding doors, otherwise the Nauticats would not have the problem they have with the side cabin sliding doors not being accepted as of enough watertightness, obliging them to consider the sill of such doors as the downflooding point.

That's why I'm amazed about Moody 45DS's stability curve. If that door does not comply with watertightness and structural requirements, the deck saloon cannot be considered as a watertight space for stability (KN) calculations, and to market the boat with that curve stating selfrightness would be incorrect.

I have written Moody asking them about this and I'm awaiting an answer. If my doubts are not well founded and they provide a satisfactory explanation, at least I will learn who is the manufacturer of such watertight doors for the recreational market

Dryfeeet:
Do you own a Moody 45DS?

[TeddyDiver]

Originally Posted by Guillermo

That's why I'm amazed about Moody 45DS's stability curve. If that door does not comply with watertightness and structural requirements, the deck saloon cannot be considered as a watertight space for stability (KN) calculations, and to market the boat with that curve stating selfrightness would be incorrect.

By the picture looks like the slide door openind only back to cockpit. That way it's possible to have maybe 120deg downflooding angle? and so any watertightness isn't mandatory to A category. In that case does it have sills high enough or is the cockpit open down to sole? However if that's the case it's an accident waiting to happen IMO

ps. I believe it should anyway meet the design pressure 12kPa?

[Doug Lord]

Originally Posted by TeddyDiver

Unfortunately they are a way over any accepptable weight limit in a recreational boat.. Superyachts might be ok with it..
I'm sure it's possible, anyway for class 2, to make light cabin side doors. Maybe there's not demand enought by the commercial manufacturers..

==================
It looked to me like they would have the capability of doing special projects which might include lightweight doors. I just googled "watertight sliding doors" and didn't have time to go thru all of them but I did read about several in detail. This one appeared to have potential.....I wonder how they might respond to a request for a light weight door? Might be feasible in production quantities?
==========
Just found this:

"Podszuck manufacture a complete range of doors, complete with control systems, hardware and equipment. Products include marine fire rated doors, joiner doors, hinged and sliding doors and A60 watertight doors. Doors are manufactured from ; metal and composite lightweight materials. All products meet IMO/SOLAS FTP Code. An ISO 9001 certified company."
http://www.podszuck-gmbh.de/myCMS/index.php

They were listed under Allied Marine Services-Prouducts here: http://www.shipequip.com/products.html

[Guillermo]

Originally Posted by TeddyDiver

By the picture looks like the slide door openind only back to cockpit. That way it's possible to have maybe 120deg downflooding angle? and so any watertightness isn't mandatory to A category. In that case does it have sills high enough or is the cockpit open down to sole? However if that's the case it's an accident waiting to happen IMO

ps. I believe it should anyway meet the design pressure 12kPa?

I do not have the rules now here with me, so cannot check if downflooding over 120º requires no watertightness for A category over that. If you say it, it must be so.

But I'm not wandering if the boat is a Category A one or not. What I'm questioning is the fact of including the deck saloon volumes within the watertight zone to calculate the KN curves. That cannot be done if not all appliances are fully watertight and structurally inversion resistant, as for any other vessel, in my opinion.

Let's say the sliding door is 3,5 x 1,8 mts sized, as it looks like.
Applying a 12 kP pressure all over it, we get a total force of: 3,5 x 1,80 x 12 = 75 kN = 7,65 tonnes-force

Am I right? I doubt that door will resist that force.

More opinions?

[TeddyDiver]

Now have to correct a bit.
Supersructures are consideres as area III (not II as I recalled earlier), and the "parts of Area III protected from the direct impact of sea or slamming waves" like rear areas of the superstucture as area IV. Both in areas II and IV watertightness degree 3 is enough. However the 12 kPa design pressure still stands..

[Dryfeet]

Originally Posted by Guillermo

Thanks Doug.

Dryfeeet:
Do you own a Moody 45DS?

No. It's a MaineCat 41.

http://www.mecat.com

[Guillermo]

Just a couple of images to exemplify the very different size and type between the Nauticat 38 side doors (which prevents this boat to reach category A), and the Moody 45DS rear decksaloon door.

I even doubt if the windows of the Moody 45DS wheelhouse qualify for A category....

Could it be the volumes considered in the stability calculations and providing that outstanding stability curve are just the ones of the coachroof only? (asuming it forms a watertight volume)

Moody has not answered my questions about this issue. Anybody out there owning one of these boats who could be of help....?

[BATAAN]

Being an old traditional type of guy and having cruised both Mexico, the Marquesas and the Pacific NW I'd like to weigh in on the P/H question.
All the discussion about efficiency, windage and drag gets vague. Bottom line is everything above the waterline is drag, which is one of several reasons traditional sailing vessels generally have low freeboard, not much cabin and no pilot house. They sail much better that way and in the old days with no engine that was life or death, economically anyway.
A good, strong P/H is not cheap to build. Neither is a Bimini/Dodger combo. I have a good friend who is the local "dodger queen" and builds 10-15 a year, and they are expensive, temporary and pretty necessary here in the Pac NW, so she has job security.
A yacht, with its entirely different design needs, has an engine, usually powerful, and crew that are possibly a little softer around the middle than your old time working sailor. The crew is used to couches and roofs, A/C and heating, so of course pilothouses of various sizes and designs come into the equation, especially if the boat is away from the dock more than a few hours.
On this SPRAY type yawl, the P/H is very small and just big enough for the watchstander who can see most of the horizon from inside. I have personally seen green water out the windows when the boat landed on her side at the bottom of a breaking wave off the Oregon coast and was very glad they were small and laminated glass as they were well underwater at the time.
A P/H, unless very strong with small windows, is subject to destruction in a broach, knockdown or breaking wave, opening the vessel to flooding.
Years ago, when working on the 1840s whaling ship CHARLES MORGAN at Mystic Seaport, the absolute ignorance of most of the public about sailing ships was really brought home to me by how many guests asked why "the steering wheel is at the back and you can't see where you're going?".... I would try to explain that seeing the sails is essential, watching for traffic lights isn't as you have a lookout for that. The same applies to pilot houses and biminis. If you must be an inside sailor due to local conditions, keep it very small and strong and put a window in the roof and you will have a wonderful time.
If your sailing is dockside, or summer afternoons, a glass-enclosed condominium on deck makes perfect sense to keep your guests comfortable as you'll probably be motoring to windward with the sail covers on anyway.

[Guillermo]

Here the answer from Hanse Yachts:

"Betreff: RE: Hanseyachts Website Contact

The stability curve for the M45DS is rather impressive. We questioned this in detail with Dixon Yacht Design when the model was first created and the data was submitted for CE approval.

The superstructure/deckhouse volume is included in the stability calculation, this is in accordance with the CE guidelines. As with a more conventional superstructure this calculation assumes that the cabin does not flood significantly during a knock down. In order to achieve this the hatches and doors need to be sufficiently weather tight to prevent a sudden inflow of water. This is the case with the patio door, which is more closely sealed than a conventional sliding hatch garage.

Dixon Yacht Design also calculated that the opening part of the door itself does not immerse until almost complete inversion, so the risk of partial flooding is further reduced. The enormous self righting force also means that the yacht will come upright in a much shorter time period than a conventional type.

To pre-empt a further question:

The superstructure windows and door are all constructed for Moody by a specialist marine supplier from toughened glass. The glass strength/thickness significantly exceeds the structural requirements.

Best regards"


Well, I am amazed to learn that big sliding door is able to resist a 12 kP/m2 pressure all over it, as required by the ISO 12216. As said this may mean a total load of about 7+ tonnes over it.

Even accepting what is said about the watertightness of the deck saloon windows and sliding door, I cannot less than feel quite worried about the structural resistance of the whole of the thing to resist a full knockdown caused by the impact of a wave.

[TeddyDiver]

Originally Posted by Guillermo

Well, I am amazed to learn that big sliding door is able to resist a 12 kP/m2 pressure all over it, as required by the ISO 12216. As said this may mean a total load of about 7+ tonnes over it.

Thanks Guillermo of interesting info. And thanks to Hanse yachts too. They don't state excactly the amount of strength achieved. The designer may have had their own calculations (of the forces involved) and they maybe have this way gone around the general 12kPa/m2 pressure requirement??