Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 05-01-2015, 16:35   #1
Registered User

Join Date: Dec 2014
Location: AUSTRALIA
Boat: ADAMS BLUE WATER 30
Posts: 74
Cat Bridge Deck Clearances?

Hi Guys.... anybody done some research into bridgedeck clearances from best to worst and whether they could post up a list of makes and models for us newbies?
__________________

__________________
ALIAS is offline   Reply With Quote
Old 05-01-2015, 17:06   #2
cruiser

Join Date: Aug 2014
Posts: 506
Re: CAT BRIDGE DECK CLEARANCES??

Quote:
Originally Posted by ALIAS View Post
Hi Guys.... anybody done some research into bridgedeck clearances from best to worst and whether they could post up a list of makes and models for us newbies?
May I just say that I think it is most commendable that you are researching sailing and safety qualities of a catamaran rather than the normal "has it got a galley up option and what colour is the carpet".

I wish you well in you research.

It must be noted that manufacturers data must be taken with a grain of salt as their in the business of making money. Data such as bridge deck clearance depends on where one holds the tape measure,( Eg ever looked under a Seawind
1000) , if its measured lightship what is the published sinkage rate (good luck with that one), and displacement means different things to different marketing departments.

Have you checked out a "chincogan 40" or the smaller" Lightwave". Both designs are nice middle of the road Aus production cats.[
__________________

__________________
Seaslug Caravan is offline   Reply With Quote
Old 05-01-2015, 17:29   #3
Senior Cruiser
 
mikereed100's Avatar

Cruisers Forum Supporter

Join Date: Dec 2005
Location: Santa Barbara
Boat: 46' custom cat
Posts: 1,573
Images: 2
Re: CAT BRIDGE DECK CLEARANCES??

The information you are looking for can be found at Multihull Maven.

Guide to all trimaran, catamaran and proa models

As far as I know nobody has made a list comparing different boats, but after looking at a few you will know which have the higher and lower bridge deck clearances.
__________________
Mike

www.sailblogs.com/member/rumdoxy

Come to the dark side. We have cookies.
mikereed100 is offline   Reply With Quote
Old 05-01-2015, 17:44   #4
Registered User

Join Date: Oct 2007
Location: Winters cruising; summers Chesapeake Bay
Boat: Catana 471
Posts: 1,239
Re: CAT BRIDGE DECK CLEARANCES??

Quote:
Originally Posted by mikereed100 View Post
...but after looking at a few you will know which have the higher and lower bridge deck clearances.
I think Mike is right here. As someone like ALIAS proceeds along his analytic approach, he/she will accumulate in his mind a database of boats of various attributes just by observing. When it comes to bridgedeck clearance, this is an easy discriminator. Most available pictures of cats include a stern view. Just imagine whether you can get under that boat in a dinghy? If not, it might be too low...

2 Hulls Dave
__________________
2Hulls is offline   Reply With Quote
Old 05-01-2015, 18:02   #5
Registered User
 
UNCIVILIZED's Avatar

Join Date: Jun 2014
Location: Up the mast, looking for clean wind.
Boat: Currently Shopping, & Heavily in LUST!
Posts: 5,629
Post Re: CAT BRIDGE DECK CLEARANCES??

Quote:
Originally Posted by Seaslug Caravan View Post
May I just say that I think it is most commendable that you are researching sailing and safety qualities of a catamaran rather than the normal "has it got a galley up option and what colour is the carpet".

I wish you well in you research.

It must be noted that manufacturers data must be taken with a grain of salt as their in the business of making money. Data such as bridge deck clearance depends on where one holds the tape measure,( Eg ever looked under a Seawind
1000) , if its measured lightship what is the published sinkage rate (good luck with that one), and displacement means different things to different marketing departments.

Have you checked out a "chincogan 40" or the smaller" Lightwave". Both designs are nice middle of the road Aus production cats.[

+1
On this, someone once told me to use the rule of thumb of 1" (2.5cm) per foot (30cm) of beam. Though that's not exactly a standard which I'd necessarily go by. From most of what I've run across, 2' +/- on a loaded with stores & cruising gear, small to mid-sized cat is kind of the minimum starting point. With 2.5'-3' being that much better.

However, a lot of it depends upon the boat's design. Features including hull shape, the hulls being flared or not, flare built into the hull to bridgedeck connection, how far back from the bows the bridgedeck starts, how far from the end of the boat it ends, etc.

And the truly key thing, is to find out via querying owners of the various, desired candidate boats in question. IE; chatting with them on the topic to see what they think of the boat's performance, and under what conditions it slams under the bridgedeck. As to varying degrees, from everything I've gathered, most boats will slam, the key point(s) being: under what conditions, & how much?

For example, Woods Designs are small boats with a medium amount of clearance (limited due to size), but they seem to fare well in this area. Woods Designs & Bridgedeck Slamming
I did a decent amount of research into them (and wish that I could modify the title of that post), but they seem like good boats. Also, another place to look for designs, performance, & many other things catamaran is www.Multihull-Maven.com

I've been in touch with a bunch of good designers, so if you need some POC info, just let me know.
Good luck in your search.

PS: One important thing to state when asking this question, is the size of catamaran which you're looking at, & what it's purpose will be. There are some excellent questions to ask yourself here;
Kurt Hughes Multihull Design - Catamarans and Trimarans for Cruising and Charter
Kurt Hughes Multihull Design - Catamarans and Trimarans for Cruising and Charter
__________________

The Uncommon Thing, The Hard Thing, The Important Thing (in Life): Making Promises to Yourself, And Keeping Them.
UNCIVILIZED is offline   Reply With Quote
Old 05-01-2015, 18:15   #6
Registered User

Join Date: Jan 2014
Location: Sydney, NSW
Posts: 682
Re: CAT BRIDGE DECK CLEARANCES??

Go have a look at Multihull Dynamics.

Multihull Dynamics, Inc. - Home


He has posted bridgedeck clearance on most multihulls and where he does not have them, it means the manufacturer or designer has asked him not to publish the data, or he has not been able to get the information.To my mind that is not a good sign, hint, hint.

I know that he talks to the boats designer directly.

You will also be able to compare boats side by side on many other parameters in order to get an idea of their safety characteristics and sailing performance.

Well worth the time to spend some time at that site.
__________________
BigBeakie is offline   Reply With Quote
Old 05-01-2015, 19:10   #7
Registered User

Join Date: Dec 2014
Location: AUSTRALIA
Boat: ADAMS BLUE WATER 30
Posts: 74
Re: CAT BRIDGE DECK CLEARANCES??

Thanks Guys with the multitude of info.
__________________
ALIAS is offline   Reply With Quote
Old 05-01-2015, 19:33   #8
Elvish meaning 'Far-Wanderer'
 
Palarran's Avatar

Cruisers Forum Supporter

Join Date: Jan 2008
Location: Me - Michigan / Boat - Tenerife
Boat: 56' Fountaine Pajot Marquises
Posts: 2,641
Re: CAT BRIDGE DECK CLEARANCES??

Hello Alias,
I know your new to the forum so welcome. Bridge deck clearance has been discussed many times in the past, not that it's a problem to do it again. But if you want, try searching for past threads. You can use the custom google search by clicking the search tab and selecting the second search box. I used "catamaran bridge deck clearance" and got catamaran bridge deck clearance - Google Search
__________________
Not all who wander are lost

http://www.sailblogs.com/member/palarran/
Palarran is offline   Reply With Quote
Old 05-01-2015, 19:56   #9
Registered User

Join Date: Dec 2014
Location: AUSTRALIA
Boat: ADAMS BLUE WATER 30
Posts: 74
Re: CAT BRIDGE DECK CLEARANCES??

Quote:
Originally Posted by BigBeakie View Post
Go have a look at Multihull Dynamics.

Multihull Dynamics, Inc. - Home


He has posted bridgedeck clearance on most multihulls and where he does not have them, it means the manufacturer or designer has asked him not to publish the data, or he has not been able to get the information.To my mind that is not a good sign, hint, hint.

I know that he talks to the boats designer directly.

You will also be able to compare boats side by side on many other parameters in order to get an idea of their safety characteristics and sailing performance.

Well worth the time to spend some time at that site.
Thanks for the GOOD link and yes not all have bridge deck clearance listed including the Leopard 42 or the Corsair 3600 just to mention two.
__________________
ALIAS is offline   Reply With Quote
Old 05-01-2015, 19:57   #10
Registered User
 
RichinBoca's Avatar

Join Date: Jun 2014
Posts: 57
Re: CAT BRIDGE DECK CLEARANCES??

Check this out:

http://www.liveantares.com/pdf/BridgedeckClearance.pdf
__________________
RichinBoca is offline   Reply With Quote
Old 05-01-2015, 20:23   #11
Registered User
 
Training Wheels's Avatar

Join Date: Aug 2014
Location: Left coast.
Posts: 673
Re: CAT BRIDGE DECK CLEARANCES??

More is better!


Sent from my iPad using Cruisers Sailing Forum
__________________
Training Wheels is online now   Reply With Quote
Old 06-01-2015, 05:19   #12
smj
Registered User

Join Date: Nov 2007
Boat: Searunner 38 catamaran
Posts: 3,657
Re: CAT BRIDGE DECK CLEARANCES??

Quote:
Originally Posted by Training Wheels View Post
More is better!


Sent from my iPad using Cruisers Sailing Forum

Up to a certain extent. As the bridge deck clearance rises so does the CG, so there has to be a happy cut of point.
__________________
smj is offline   Reply With Quote
Old 06-01-2015, 06:01   #13
Senior Cruiser
 
colemj's Avatar

Cruisers Forum Supporter

Join Date: Oct 2005
Location: Presently on US East Coast
Boat: Manta 40 "Reach"
Posts: 10,049
Images: 12
Re: CAT BRIDGE DECK CLEARANCES??

The shape of the bridgedeck needs to be considered along with its clearance. I have seen bridgedeck shapes with flat panels and even vertical panels in them that accentuate slamming, noise and things bouncing off tables. Also, large bump outs can be bad - especially if they are holding the berth you need to sleep in.

Mark
__________________
www.svreach.com

You do not need a parachute to skydive. You only need a parachute to skydive twice.
colemj is offline   Reply With Quote
Old 06-01-2015, 06:09   #14
Marine Service Provider

Cruisers Forum Supporter

Join Date: Jul 2007
Location: Marmaris
Boat: FP Orana 2010, Lipari 2011, Hélia 2013, Catana C 47 2013
Posts: 1,033
Re: CAT BRIDGE DECK CLEARANCES??

The worst that I've seen so far are Prouts..The best are Catana, Eric Lerouge design cats, etc. FP and Lagoons fall into the middle, Leopard probably more on the lower side. These charter oriented boats have had various models over the years and not all of them have the same bridge deck clearance.
I should add that bridge deck clearance is not the only parameter to consider if the issue is under bridge slamming; the opening between the hulls and the protrusions inside the hull or the bridge deck do equally matter. Many new models now are installing front cabins at the entry of the bridge rather than on the bows. This is not a good idea, particularly if the boat is shorter than 50-52 ft.This leads the hulls to be fatter, the tunnel underneath the bridge narrower and even if theoritical bridge deck clearance is OK, you will get a lot of slamming with the water compressing in between the hulls..
Hope this helps
Cheers
Yeloya
__________________
yeloya is offline   Reply With Quote
Old 06-01-2015, 08:19   #15
Registered User

Join Date: Apr 2013
Posts: 4,886
Re: CAT BRIDGE DECK CLEARANCES??

Beam plays a big role. Smaller 16-18' beam boats need far less clearance than a monster 25-30' beam boat.

To see why draw a sinosoidal wave:
- Now draw a boat with a beam of one wave length sitting on top of the wave. You will find that the bridge deck must be at least the wave height to avoid hitting the wave.
- Now draw a boat with a beam of 1/2 wave length sitting on top of the wave. You will find a clearance of around 1/3 of the wave height is enough to keep the bridge deck off the water.

Of course this is a simplified example and waves come in many heights and lengths but it demonstrates the principal.

In practice, you will find large cats get high bridge deck clearance. They can get away with it without becoming top heavy (both in appearance and center of gravity) and providing plenty of headroom for the bridgedeck living space.

Smaller boats must balance higher bridge deck clearance with sufficent standing headroom:
- Some boats address this by making it more of a crawl space.
- Some skip bridge deck accomodations.
- Others accept lesser clearance in return for more space.
- Then there are tricks to help such as nacels and varying the clearance with it being high at the front and lower at the back so the boat is better able to rise with the waves.

While generally a good thing, high bridge deck clearance is only one factor in designing a good cruising catamaran and other factors can take precedence.
__________________

__________________
valhalla360 is offline   Reply With Quote
Reply

Tags
deck

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Big River Bridge Clearances cruiserbill Navigation 1 05-07-2013 08:12
Gulf ICW Bridge Clearances F51 Navigation 6 11-07-2011 20:07
Bridge Clearance of 'Seven Mile Bridge' (South of Boot Key) ? Almost Heaven Navigation 4 18-11-2010 15:20
What's Your Cat Bridge Deck Clearance? Atlantic42 Multihull Sailboats 10 08-07-2009 21:26



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 20:56.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.