Woods Designs & Bridgedeck Slamming

[UNCIVILIZED]

G'Morning Folks,
I was hoping that some of you out there might help me a bit experience wise. I'm toying with the idea of switching to a catamaran, but have a couple of sticking points... one of them being bridgedeck slamming.
I've sailed & raced a LOT, at times in conditions where your sphincter would leave pucker marks in the deck, & when you got to port you'd have to see a dentist, as the conditions shook the fillings out of your teeth. But I'm Real lean when it comes to multihull experience.

From what I've seen, particularly design wise, I really like Richard Woods's boats. The Sagitta (30') and it's bigger sister, the Eclipse (33'). However, from what I've seen via pictures, and the time which I spent on a Banshee 35' (dockside), they seem a bit shy in terms of bridgedeck clearance. Like 1.5', maybe, or 2' max (in glassy calm waters). And if I'm wrong on these numbers, someone please correct me.

Now I know that they have the flared hulls, which helps a good bit in terms of avoiding the slamming thing, but bottom line, from what I can gather, little beats vertical clearance when it comes to avoiding slamming. Not even ideal hull shapes which minimize pitching, so that you aren't hobby horsing & forcing the front or aft end of the bridgedeck into the next wave.

So if folks out there could share there real world experiences with me on this I'd REALLY appreciate it. The more specifics the better on this, too. In particular:
- what you are/were sailing
- wind & sea conditions @ the time (including wind & wave angle, plus sea state)
- boat make & model
- and... measured bridgedeck clearance.
Plus any other important specifics which my under caffeinated brain may have forgotten to ask/list ;-).

I'd hate to spend 3 years building a boat, & then cry about how she handles/have a fair weather floating condo. Especially as I'm a fan of being able to tote plenty of toys, spares, & stores, when I head for the horizon... regardless of what it's blowing.

I've really liked the pair of trimarans which I spent some time on, but they were Definitely weight sensitive! Albeit for ride comfort and speed, I'd never been on anything like them in my life. Both on the hook, as well as under sail.
15kts in 25kts of breeze on a reach, while comfortably sliding down 20'-25' rollers, with just a genoa & 1 reef in the main - Sweet!

One of the other reasons which I'm ask these questions is that I so frequently see folks with cruising cats, extending them by 5', and or simultaneously raising the bridgedecks. And these trends aren't specific to one designer. I've seen it on Woods's, Shuttleworths... even Searunner trimarans. So it's not just one type of boat. Nor are the owners particularly gear happy.

Thanks in advance, & fair winds.
Andy

PS: Ah, & for specificity, I'm thinking world cruising here. Including ocean crossings with regularity.

[GordMay]

Here’s what Richard Woods has to say on the subject:
➥ Bridgedeck Slamming

Here is an article, by Sackville Currie, suggesting a guideline formula to consider the relative merits of diverse cat designs in regard to bridgedeck clearance.
➥ http://www.liveantares.com/pdf/BridgedeckClearance.pdf

[Dulcesuenos]

Any cat can slam depending on the conditions. . Boatguy30 is building a larger woods so he may be able to answer more questions about woods. I will say the pictures of a few of woods cats loaded they seem low in the water.

Sent from my LG-LS980 using Cruisers Sailing Forum mobile app

[Roy M]

Going fast is good. Slamming is bad. You are probably going to have a better experience with these two factors if you have a lightweight trimaran. But there are very few of these out there, and a world of catamarans. Supply and demand. Not good for the budget. But even light trimarans get caught in short interval chop and square waves, so they bear off and get happier.

[UNCIVILIZED]

Originally Posted by Dulcesuenos

. I will say the pictures of a few of woods cats loaded they seem low in the water.

My point Exactly. And also the reason why I'm looking for advice & experiences coming from folks other than someone with a vested interest in a particular vessel(s). Like say, it's designer.
Not that they'd be dishonest persay, however, they're going to have a slanted point of view, no question. Such as where Richard Woods states "I always say that for offshore sailing one should be able take a conventional inflatable dinghy under the bridgedeck".
To me, that ain't much clearance - call it 1.5' max... with an outboard, & less without one.

And here Sagitta - 9m round bilge performance cruiser in picture #2 (of a 30' Sagitta), there appears to be perhaps 1' of clearance under the bridgedeck. Which will turn into a good bit less, once that vessel turns to go upwind. As the numbers/formula for upwind clearance state that when you're going upwind, knock a good 20% off of the boat's static bridgedeck clearance height.

I know that most catamaran slamming isn't structural, however, I don't want to spend days or weeks at see living inside of a giant "woofer", "feeling" the bass.

[colemj]

It is going to be very difficult to find a 30-35' boat suitable for what most think of cruising with >2' bridgedeck clearance.

Bridgedeck clearance is a relative measure wrt slamming, and not an absolute value.

Taking plenty of toys while having high bridgedeck clearance requires waterline - no matter what design.

Waterline is also the key to slamming - longer boats need less relative bridgedeck clearance.

Lighter boats need less relative bridgedeck clearance.

While adding length to the sterns (and even bows) of an existing boat is easy and often done, I don't know how one would go about raising the bridgedeck without MAJOR work.

Mark

[UNCIVILIZED]

colemj,
Thanks for the info & input. And yeah, I totally get what you're saying. The big factors for me looking @ the noted Woods designs have to do with:
- Build Time(s) & Complexity
- Cost(s); both for building the vessel, & especially with fitting her out to cruise
- Ease of handling, especially for the "dangerous" parts of sailing, like docking & marinas. Especially including Short & Singlehanded sailing.
- Resale value, including the factor which is based on the Designers; Reputation, & Name brand/reputation.
- Engine type & number. In this area, outboards have a LOT going for them.
- Vessel Longevity. Both perceived & actual.
- Resale value

One other design which I've got my eye on is Kurt Hughes 36-footer. However, while I love that design, it looks like a LOT of boat to build. And I'm, of course, VERY aware that boat size goes up with the cube of it's length. Albeit, Kurt's designs seem to kind of have mixed reviews. As to why this is, I'm uncertain. Though they're supposed to sail almost in a class of their own.
But if $ were no issue, then yeah, I'd pick up/build that 36' of his Kurt Hughes Multihull Design - Catamarans and Trimarans for Cruising and Charter Small enough to easily sail shorthanded, fast, high righting moment (stability), GR8 ability to carry a load, & a nice bit of room inside, PLUS, 2 1/2' of bridgedeck clearance (with the ability to easily design in more.

[colemj]

Bridgedeck clearance on a cat that size is a compromise. That Hughe's design only has 5'8" headroom in the saloon. Whether that is an appropriate compromise for full-time cruising is a personal preference.

Mark

[Cavalier MK2]

You could build a longer performance oriented design without the bridgedeck cabin for more bridgedeck clearance using the same materials investment.There are many of these designs offered by most of the major designers.

[Dulcesuenos]

Hull design is important too. Fatter more buoyant hulls will ride up and over waves that would slam on other types, lots of variables

Sent from my LG-LS980 using Cruisers Sailing Forum mobile app

[Cheechako]

a bit hard to find pics on line but I found a couple of the Eclipse. On the BD clearance it looks like middle of the road to me, not as minimal as some, not as good as others. I was able to get a 10 ft Caribe with the 15hp Yamaha under my older Lagoon 42.... just barely... pushing down on the back of the dingy.

[django37]

Originally Posted by Cavalier MK2

You could build a longer performance oriented design without the bridgedeck cabin for more bridgedeck clearance using the same materials investment.There are many of these designs offered by most of the major designers.

Yes: 31' LOA with 3' to bridgedeck - but no cabin

[smj]

Originally Posted by django37

Yes: 31' LOA with 3' to bridgedeck - but no cabin

Nice boat


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[UNCIVILIZED]

Thanks for all the info, ladies and gents. And any more which you have to offer will be appreciated as well.

To perhaps clarify what I'm after in a catamaran a bit more. A bridgedeck cabin isn't optional, it's THE Whole why behind building a cat to me. And it needn't have full standing headroom either.
I'm actually in a position similar thinking wise to Richard Woods on this, in that it's actually an advantage. In that, if your cabin has 5'3" of headroom, it's still pretty easy to see over when you're in the cockpit. And I'm not a fan of needing an elevated helm station with 1 or dual destroyer wheels mounted on the cabin's aft bulkhead.
Call me a simpleton, but push come to shove, I prefer a tiller (well for all but heavy duty auto-pilot mounting).

And while I'm a solid 6' tall, bending down 6"-8" to walk around in the bridgedeck's more than an acceptable trade off, given the up sides it adds to sailing the boat.

[snort]

Your reasons for a shorter cabin roof regarding visibility are good, but you could also get nearly the same 360 degree visibility in a design like the Seawind 1000. You can see through the windows that are amply sized.
I don't know if there are any perfect designs out there. Trade-offs like any boat, but Australian designs are among my favorites.