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Old 07-17-2012, 06:29 AM   #1
Ocean Senior Sailor
 
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Default Catamaran Design and Bridge Deck Clearance

Open for discussions and opinions


(1) Interested in comments from Catamaran owners re Bridge deck clearance. I have heard reports
about low bridge deck clearance causes Slamming and pounding of significant proportions when sailing to windward. Comments please.

(2) Some designs have .500m clearance others .700m and I notice the latest designs on some are rising to .950m and 1.2m
bridge deck clearance. Comments please.

(3) I have noticed quite a few catamarans stay in port while Monohulls make passage to their next port. When asked why they are staying in port
I,m told waiting for for less wind and a better wind angle. Supposedly this has something to do with Slamming and pounding? Comments please.

(4)Galley preference. Main bridge deck or hull. As a interested cook and have cooked on numerous vessels I ponder the merits in having the galley within the bridge deck. Re heat transfer- Condensation- Moisture- the heat generated from the galley causing condensation on the ceiling, moisture gathering in drapes, upholstery plus smells and vapours, books in library pages being affected and absorbing the moisture. As usually with most modern designs the chart table and electricall main board and electronics are also positioned in main saloon - bridge deck, I wonder the wisdom re this.
I would have thought the galley in the hull would be preferable with higher head room - hatches and extractions fans and more ventilation - thus removal and moisture control would be more efficient, plus providing a larger lounge area in the main saloon. After all the kitchen in most homes is not in the lounge. Plus normally in the tropics if one does not have air conditioning one gathers with chilled drinks in the cockpit area with sea breezes and a view and possibly to be a nosey parker while the cook cooks. Comments please.


Below are some hyperlinks to a new design with increased bridge deck clearance. How ever I,m would have thought for offshore passage and in moderate to heavy seas a clearance around about 1.6m to 1.8m
would be needed to avoid constant bridge deck slamming when going to windward or even slightly cracked
sheets. Comments please.

"Schionning Designs -" Catamaran design.

"Schionning Designs -" Catamaran design.

"Schionning Designs -" Catamaran design.


Thanks in anticipation.
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Old 07-21-2012, 06:10 AM   #2
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Default CATAMARAN design and bridge deck clearance:

Open for discussions and opinions


(1) Interested in comments from Catamaran owners re Bridge deck clearance. I have heard reports
about low bridge deck clearance causes Slamming and pounding of
significant proportions when sailing to windward. Comments please.

(2) Some designs have .500m clearance others .700m and I notice the latest designs on some are rising to .950m and 1.2m
bridge deck clearance. Comments please.

(3) I have noticed quite a few catamarans stay in port while Monohulls make passage to their next port. When asked why they are staying in port
I,m told waiting for for less wind and a better wind angle. Supposedly this has something to do with Slamming and pounding? Comments please.

(4) Galley preference. Main bridge deck or hull. As a interested cook and have cooked on numerous vessels I ponder the merits in having the galley within the bridge deck. Re heat transfer- Condensation- Moisture- the heat generated from the galley causing condensation on the ceiling, moisture gathering in drapes, upholstery plus smells and vapours, books in library pages being affected and absorbing the moisture. As usually with most modern designs the chart table and electricall main board and electronics are also positioned in main saloon - bridge deck, I wonder the wisdom re this.
I would have thought the galley in the hull would be preferable with higher head room - hatches and extractions fans and more ventilation - thus removal and moisture control would be more efficient, plus providing a larger lounge area in the main saloon. After all the kitchen in most homes is not in the lounge. Plus normally in the tropics if one does not have air conditioning one gathers with chilled drinks in the cockpit area with sea breezes and a view and possibly to be a nosey parker while the cook cooks. Comments please.

Below are some hyperlinks to a new design with increased bridge deck clearance


Schionning Designs -

Schionning Designs -


Schionning Designs -


http://www.schionningdesigns.com.au/...udyplansA4.pdf










How ever I,m would have thought for offshore passage and in moderate to heavy seas a clearance around about 1.6m to 1.8m
would be needed to avoid constant bridge deck slamming when going to windward page or even slightly cracked
sheets. Comments please.




Thanks in anticipation.
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Old 07-23-2012, 01:51 AM   #3
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Hi piclarke, some quick thoughts/responses to your question points.

(1) Slamming in cats can happen on all points of sail, not just when going to windward. Wave shape and spacing, weight of cat(loaded) and amount of sail up(speed) all play a part.

(2) Normally small cats have less clearance than big ones, same goes for size of beam, for obvious reason. Shape and hull beam are also different from one cat to the next. Design and weight are major factors in amount of slamming a cat may expect.

(3) More likely strength and direction of wind. Not many sailors like beating in strong winds as it is uncomfortable and progress is slow. Also most cruising yachts are set up for down wind sailing and do not have a good tacking angle. Experience and confidence also play a part in making decision when to leave port.

(4) Most cats are well ventilated, so comes down to personal choice. At least a cat gives you the choice.

All boats are a compromise, I hope you find the boat that suits you.
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Old 09-11-2012, 03:23 AM   #4
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Default Not quite so simple!

Any multihull can and probably will slam in some conditions...have you been on a large offshore wavepiercer for example?
After many thousands of ocean miles cruising a 10m Banshee catamaran (yes comparatively low bridge deck .5-.7m) I have found that you just have to sail to the conditions, it's the same on any vessel, mono's included. There are some catamarans (S. African comes to mind) that have next to no clearance but they seem popular enough although the owners do admit to having to pretty well stop the boat in really rough conditions.
I can honestly say that I have no complaints about the Banshee even though at odd times the ride has been a bit uncomfortable..due to me pushing a bit hard.
As to the galley..being low and central in a hull is a secure and stable place to cook and if you can see out too, that's a bonus.
All comes down to preference and depth of pocket. Maintanance goes up exponentially with size.
Enjoy the search for your perfect boat.
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Old 09-11-2012, 04:14 AM   #5
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I briefly owned a trimeran (Piver 32) which I had bought as a project to then renovate for sale. I confess to not being a multihull convert after sailing it. I have sailed on big cats and loved sailing my tiny little Maricat on a lake. I can't point to specific performance related issues with cats, except for the slamming in rough conditions. But, monohulls have their problems in big seas also.

I remember having to spend two hours skirting a reef to get into an anchorage in North Queensland after leaving Watson's bay at Lizard island. I was on my 53' sloop. A fellow sailor on a 45' cat left after me and as the tide was high, when he reached the anchorage, he sailed straight across the reef in five feet of water. On that day, I cursed my 7' draft and wished briefly to own a catameran.

However, I recovered and remain a traditionalist. I think cats are great for coastal cruising, but I would still choose a mono for serious offshore work.

The perfect boat must always be a compromise.

Just to finish; I sailed with an aquaintance on a Heavenly Twins, 28' cat in a 3' harbour slop in Darwin. It was bloody awful! But, the owner had sailed it all the way from Portsmouth in the UK, to Darwin and is now, presumably back in the UK after setting off across the Indian ocean some 3 years ago. Horses for courses!
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Old 01-15-2013, 02:56 PM   #6
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Auzee: Like you, I too owned a Piver, I bought in 2000 from a Jax Fla owner - kept it about a year, after discovering it had no room for living aboard. The tri had different set of learning problems than our old Morgan 46 O/I. We traded up to a Frers designed 55 whatever cat - which had tremendous liveability and manuverability. Not much in the way of slap - tho it did dive into the sea on occasion while crossing to the Azores. We kept it for several years and I thoroughly enjoyed the up cook station. It had four staterooms, which we made into two and a master suite. The B-Cummins engines were derated to 210 hp, and were still too much for the boat. We went with Walters Keel Coolers to keep the engines in tip-top shape and eliminate the raw water exchange and then put in two dry stacks about 10 ft forward. They never got in the way, nor did they soot up the boat. That said, after we reluctantly sold her - she was a grand boat, and I wish I still had her.
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Old 02-05-2013, 04:09 AM   #7
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Most people who own catamarans don't understand how the boat works. It has no rolling motion but does pitch, swiveling around the . The idea is to keep the boat light, and the weight out of the bow and stern. Underway, pick the anchor off the bow and stow it in the anchor locker. A 35 lbs anchor on the bow is like 700 lbs due to the lever effect. Same for the stern. If you have a water maker, you don't need to carry 100 gallons of water (700 lbs). Instead carry 20 gallons and make water when you need it. All kinds of tricks you can do to keep your boat light. If the cat is poorly designed then you are screwed, no matter what you do.
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Old 02-05-2013, 05:13 AM   #8
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I had an aquaintance who named his monohull 'Onemaran'.
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