Multihulls that don't slam

[roland stockham]

Any boat with a flat surface on the bottom will sometimes slam, many modern canoe bottom mono's slam really badly as well and the wave slap under the stern keeps you awake at anchor. Not only is it uncomfortable it is very hard on the boat and brings progress to a juddering halt so makes it impractical to sail upwind. Raising the bridge deck or narrower beam will mean it takes a bigger sea before it slams.

[Cadence]

Someone made a quip it is called a tri.. Which cat is made with the bridge deck configured like a V hull? I would think that would minimize the slap?

[nimblemotors]

Originally Posted by Cadence

Someone made a quip it is called a tri.. Which cat is made with the bridge deck configured like a V hull? I would think that would minimize the slap?

Not a production boat. When the batteries are fully charged, it weighs it down so much that it might slap a bit more...

[Cadence]

Originally Posted by nimblemotors

Not a production boat. When the batteries are fully charged, it weighs it down so much that it might slap a bit more...

That's not the one. I can feel the thread drift coming, solar power.

[mikereed100]

Originally Posted by REsCat

Mike.... With all due respect.... For all the sailing miles, experience, conditions that you detail above... day or night....have you (or can you?) continually watched the wave conditions and interaction with your bridgedeck underneath, or "fat hulls" and the resultant bang,slap, pound... what ever you want to call it!
Can you honestly say that your bridgedeck has never slammed with an errant wave or cofused sea condition????
I am pretty sure my bridgedeck clearance is probably as high or higher than yours and I have logged similar if not more miles and I could never make that claim.
I know I have "slapped, banged, pounded" with some part of my bridgedeck or hulls at some point (sometimes have observed it...) during the miles and have cringed on the thankfully few "bone crunchers" and been glad that my hull construction/design is pretty robust so far.

I also cannot understand a claim that a monohull, be it loaded or empty has never fallen off a wave, or tangled with confused seas, chop and suffered a "bang,pound,slap,crunch" ???
I have logged offshore miles on Swans, Tartans, Hughes to name a few and they were not immune to the above conditions....

Bob

Bob,

I'd have to say I'm pretty sure our bridgedeck has never slammed, at least in the way I hear described by others. We certainly get 'slaps', but it is just that. Doesn't make you look up from your book, doesn't jiggle the coffee in the cup. We do occasionally get a bang on the hull like someone smacked it with a wet goat, but -as yet- not on the bridgedeck. I fully expect to some day, it's just that I can't honestly say it has happened yet. Of course, I could be completely wrong, but that's my story and I'm sticking to it.
We have very similar bridgedeck clearance and tunnel width to a Catana 47, but our hulls are much wider at the waterline with a more squared off underwater profile, not the more typical half-round seen on most cats. The benefits are less immersion with loading and greater buoyancy, which tends to keep the bridgedeck up and the forward cockpit dry. The cons are that it probably makes for a more 'bouncy' ride than a cat with narrower hulls and there is no way we could keep up with your Catana in a race around the buoys.

[Rotten Ricky]

Yes, there is a multihull that does not slam - it is called a trimaran! You might take a second look at them.

They have the virtue of being something of a cross between a cat and a mono. Their action underway is smoother and less likely to have the sharp correction that a cat can have as a wave passes by underneath on a beam reach - those two hulls have to follow the surface of the water - yet it is not always at a constant exhausting heel like a mono wallowing along. You have to rethink interior space, though, as it tends to be a lot less concentrated on one big volume like a monohull, or in three areas like a cat with a bridge-deck cabin. But the ride can be wonderful, being both quick and comfortable.

RR.

[Cadence]

Originally Posted by Rotten Ricky

Yes, there is a multihull that does not slam - it is called a trimaran! You might take a second look at them.

They have the virtue of being something of a cross between a cat and a mono. Their action underway is smoother and less likely to have the sharp correction that a cat can have as a wave passes by underneath on a beam reach - those two hulls have to follow the surface of the water - yet it is not always at a constant exhausting heel like a mono wallowing along. You have to rethink interior space, though, as it tends to be a lot less concentrated on one big volume like a monohull, or in three areas like a cat with a bridge-deck cabin. But the ride can be wonderful, being both quick and comfortable.

RR.

I've owned two. Love the sea keeping ability. The down side is the beam. Generally have to find a marina that can put you on the outside rather than a slip. And finding a place to get hauled?

[Highland Fling]

Originally Posted by Cadence

Someone made a quip it is called a tri.. Which cat is made with the bridge deck configured like a V hull? I would think that would minimize the slap?

Lagoon 420/421 AND most of the newer Lagoons too

[MIRELOS]

crossed the Atlantic, the wrong way, lots of seas, hardly any slamming.
high clearance and buoyancy...........all boats are a compromise, but I slept well every off shift on the Eleuthera regardless of weather

[savvy]

http://api.ning.com/files/HbsRLQ*GNX...737&height=493

this boat.

[D&D]

Originally Posted by dirkdig

Our Lagoon 440 has 650mm of bridgedeck clearance.
Going head on into seas of about 25 knot winds we get a little slamming, once 20 deg plus off that it drops right off.
Wide buoyant hulls with that clearance works.

...+2

>20,000nm now on ours...very little slamming

As noted by others, all cats will slam in the 'perfect' conditions, but if you stick with high bridge decks + fat hulls you will be comfortable.

[Cheechako]

let's face it, the seas lump up. If they happen to lump up between your cat hulls it is going to slap... has little to do with the boat. The bow waves can join to slap in some circumstances , but my cat was more the seas lumping up I think.
Of course some designs with minimal clearance will slap more than others.
a 24 foot speed boat, even at just barely planing speed slaps hard ...in just 2 ft of chop.
I would guess a Tri might minimize it.

[Cadence]

Originally Posted by savvy

http://api.ning.com/files/HbsRLQ*GNX...737&height=493

this boat.

Nice!

[D&D]

Originally Posted by D&D

...+2

>20,000nm now on ours...very little slamming

As noted by others, all cats will slam in the 'perfect' conditions, but if you stick with high bridge decks + fat hulls you will be comfortable.

...and (with credit to the designers) a nacelle under the bridgedeck also aids in eliminating slamming...

[Scout 30]

A friend of mine has a 40' Wharram that I've sailed on a lot & it's really not possible for the bridge deck to slam on this boat because the deck is on top of the hulls. Of course the trade off is there's no center cabin.