Hull slap-is it a problem

[Pilot90442]

My wife and I are looking for a 40 -45 ft cat. We are most aware of the big 3 producers. Among these 3 companies is hull slap a problem in any of them? Please comment from your experience. Just from looking at the 3 the Lagoon seems to me to have the LEAST room for waves/wake to funnel under the deck due to the middle nacelle. Unless it serves some function I don't yet understand.

FP seems to have the highest clearance and Leopard falls somewhere in the middle.

We are trying to better understand this issue from a practical point of view.

[a64pilot]

Usually mono hull guys will tell you its a problem.
Cat guys will usually tell you that yes it can sometimes be a problem, however you can pretty easily sail to where it's not a problem, just fall off a few degrees and it won't slam from my understanding. Or at least you can to a great extent control it.

Now that is just from me reading the forum, no actual experience myself, but let's see what some of the Cat owners say.
Myself I would not put much faith in hearing problems of a certain plane, from someone who never owned or flew that type of plane.

[fxykty]

Depends on which hull slap you're referring to. If you mean the slap of wakes and wavelets on the hull, then the Leopards with the sweeping hard chine are guilty. Right where that chine gets to the waterline are the rear berths, and the slap is noticeable and a nuisance. No experience with the Lagoons and FP.

However, if you mean bridge deck slamming, that's a problem for all cats to a greater or lesser extent. Some design factors that decrease bridge deck slamming are more vertical clearance, more width between the hulls, and a shorter bridge deck that is set further back from the bows.

AFAIK nacelles and other shapes on the underside of the bridge deck only make a small difference in smaller waves - if a swell is going to slam your bridge deck it will, regardless of flat or curved shape.

Bridge deck slam can happen in any direction, though generally worse if the waves/swell are forward of the beam. Slowing down helps.

[Pilot90442]

Thanks for the quick response.

I guess I'm most worried about slamming. I never realized 2 different issues existed. Thanks for informing me.

[Takamoana]

FP Lipari (39'2" LOA) No noticeable bridge deck slamming but an occasional hull side slap as a wave passes under 1 hull and catches the next, certainly nothing to alarm us. In 7 years full time cruising from Europe, to the Caribbean via the Med and now NE USA the slapping that really annoys us is when the tide holds us against the wind at anchor and the waves slap on the hull right next to our aft bunk - we just move to the forward bunk.
Fair Winds
Gary

[Taichungman]

Not sure what you mean by problem. Crewed on SF50 from Capetown to Annapolis Md. last year and it was only a problem depending on where your berth was is relations to direction of waves. I had the forward port berth which is a huge berth over the bridge deck. We had mostly down wind sailing and when waves were coming from aft of the starboard beam they would pass under and slam against the inside of the port hull and then accelerate upward knocking me about 6" into the air. I finally learned to scoot up near the aft bulkhead between my berth and main saloon and it wasn't so bad. So, having a high bridge deck like the SF50 doesn't help much or at all. I think all them are going to get slammed and be uncomfortable on some point of sail. I was not worried about damage to the structure at any time even though the sound wa a little frightening at times and the pressure of the blast was tremendous.

[LoudMusic]

This is a pretty big concern for me as well - I'm looking forward to what information this thread produces.

[Cotemar]

Hull Slap is a big problem, so look for a catamaran with a a high bridge deck clearance.

[smj]

A lighter cat will slam less than heavier as it rides over the waves rather than through. A flat bridgedeck will slam harder than a radiused bridgedeck like the LeRouge designs as they seem to dissipate the waves energy. There are a ton of factors that go into which and how hard a bridgedeck slams.

[UNCIVILIZED]

Originally Posted by smj

A lighter cat will slam less than heavier as it rides over the waves rather than through. A flat bridgedeck will slam harder than a radiused bridgedeck like the LeRouge designs as they seem to dissipate the waves energy. There are a ton of factors that go into which and how hard a bridgedeck slams.

There's the above, plus that boats which are mid to light weight, & have a dramatic hull flare or knuckle to the hull, not far above the WL will tend to slam a lot less. As the sudden increase in buoyancy provided by the flare/knuckle causes the boat to rise up & ride over the wave more, so that she slams a lot less.
For example, some of Richard Woods's boats, or John Shuttleworth's.

Also, as noted above, boats with radiused bridgedeck connections, or chamfer panels. Panels which go at a 45 deg. angle from the bridgedeck to the hull. Slam less for similar reasons. That is, a rapid increase in buoyancy as the wave approaches the leeward hull. More than is provided by just the hull itself.

Bottom line though, since you're looking at spending several hundred thousand dollars, if they won't let you test sail the thing to your satisfaction. In various conditions. Perhaps with the multihull expert of your choosing onboard at the time (call him a buyer's agent) to give you an expert opinion. Then pass on the boat.

[danielamartindm]

FWIW, I've not noticed hull or bridge deck slapping to be a problem. I don't know about other vessels, but for the Leopard 39, the issue is a nothing burger.

[GordMay]

Greetings and welcome aboard the CF, Pilot.

[gspeak]

When you first start sailing/pushing your cat of choice you will probably hear & feel lots of startling sounds & vibrations. That's the nature of Multihulls. The more you sail them, the more you get used to them & understand them. Yep they are different & yep some are different to others.

Some people will tell you that they are atrocious & others (like us) will tell you that they are awesome & you just need to learn to go with the flow.

After 7 years of sailing & the last 3 years of live aboard cruising the east coast of Oz we love our Lagoon 380 & have come to accept what some may call slamming but we call "getting it on". With familiarity & time you appreciate what you boat is capable of & the noises that result. Work within your personal & boats limits & enjoy.

Check out a short video of us "enjoying the ride" on Seabreeze. https://youtu.be/eFostd60i40

Dave

[Pilot90442]

I thank you all for your input. I think it best to let it be known where my wife and I come from in our situation so you can better understand our concerns.

We are 50 yo almost empty nesters. Grew up in Chesapeake Bay area around Norfolk Va. My wife grew up in Miami. We have both been around power boats off and on much of our lives. Quite a bit of camping over the years too. This is the logical next step. Combine boating and "camping" on the water��. Aka Catamaran!

Wife has mobility issues due to a lower back injury that cost her career as a nurse. I am a major airline pilot with east coast bases to choose from. I will continue to work as we live aboard but I can move up and down the east coast from base to base and become "snow birds" while still working. We are not going to be crossing an ocean any time soon. I can commute from almost anywhere from the east coast to the carribean without much difficulty.

My wife's mobility issue drives this. Having her get "slammed" around is a concern. Her comfort is key. We will be in marinas(no slamming concern there) since i will continue to work but we would take trips when I have more then a few days off at a time. Probably motor more then most because of that schedule (slamming concern here because conditions don't follow my schedule).

As you think of the slamming issue think of it the terms of how it affects a person with these issues. Also think in terms of coastal cruising/island hopping. Are we making it a "problem" in our mind or is it one to really worry about?

I am thinking of starting a new thread asking for safety/design input of different cats for a person with mobility concerns.

[billnb]

Originally Posted by Pilot90442

I thank you all for your input. I think it best to let it be known where my wife and I come from in our situation so you can better understand our concerns.

We are 50 yo almost empty nesters. Grew up in Chesapeake Bay area around Norfolk Va. My wife grew up in Miami. We have both been around power boats off and on much of our lives. Quite a bit of camping over the years too. This is the logical next step. Combine boating and "camping" on the water��. Aka Catamaran!

Wife has mobility issues due to a lower back injury that cost her career as a nurse. I am a major airline pilot with east coast bases to choose from. I will continue to work as we live aboard but I can move up and down the east coast from base to base and become "snow birds" while still working. We are not going to be crossing an ocean any time soon. I can commute from almost anywhere from the east coast to the carribean without much difficulty.

My wife's mobility issue drives this. Having her get "slammed" around is a concern. Her comfort is key. We will be in marinas(no slamming concern there) since i will continue to work but we would take trips when I have more then a few days off at a time. Probably motor more then most because of that schedule (slamming concern here because conditions don't follow my schedule).

As you think of the slamming issue think of it the terms of how it affects a person with these issues. Also think in terms of coastal cruising/island hopping. Are we making it a "problem" in our mind or is it one to really worry about?

I am thinking of starting a new thread asking for safety/design input of different cats for a person with mobility concerns.

All cats will slap given the right conditions.



If you're worried about wifes comfort though, any cat will be far more comfortable than a monohull, both at anchor and sail.