The Bouncing Bows - Why Didn't You All Tell Me?? :)

[ssullivan]

Originally Posted by Hud3

Sean,

If it's any consolation, I've just received a post from an Island Packet bashing to weather off Wolf Trap Light on the Chesapeake, with green water coming over the decks. Not a comfortable sail for any boat tonight!

Originally Posted by Hud3

Sean,

If it's any consolation, I've just received a post from an Island Packet bashing to weather off Wolf Trap Light on the Chesapeake, with green water coming over the decks. Not a comfortable sail for any boat tonight!

I saw them!!

There were only 3 of us out there at Wolf Trap - me... that cat, and an insane mono who was sailing... making very poor windward progress, but "keeping it real" and sailing up the Bay.

I decided to stop bashing and go to anchor because well... I have nothing to prove and would rather be comfortable. I, too had green water all the way up over my forward set of ports (see photo attached)

I didn't look very closely at the mono because I was paying more attention to the cat's bows from the photo.

The funny part is... after all that slop we were slogging against, the winds have died down completely and it's a beautiful, calm, silent sunset out here. Go figure.

Calm before the storm (tomorrow's gale warning).

[kevinmac]

What would you estimate the wave height at, when you were seeing this bows out of the water thing, and had green water over your first set of ports frequently?

Kevin

[DeepFrz]

I've been on a 50 foot mono that would rear up and slam it's bow down. The helmsman maxed the power once when we were going into the chop. The skipper was in the forward cabin and was coming right off the bunk when the bow headed down. Cats aren't the only boats that will slam when going into the chop. Usually one throttles back a bit to ease the hobby horsing.

For that reason I really dislike canoe shaped hulls for offshore passages. I would rather have a deeper draft with a finer entry. Get there a little later but much less beat up.

How did the mast look when you were bouncing around?

[BigCat]

I remember giving up on sleeping in the fore peak berth on an Ericson 35 (monohull sloop) while sailing to windward because it hurt too much-the bow would plunge into a trough, I would be left in mid-air, and I would fall just as the bows rose to the next wave. Ouch!

Does anybody have a link to that large monohull that was half out of the water sailing to windward? It's on this site, somewhere-

[maxingout]

Most modern cats have their greatest beam and boyancy aft, and the beam progressively narrows toward the bows. When you beat into chop, the boat chops its way to windward with the pivot point being fairly close to the stern. That results in a pitching motion that can become severe if you synchronize the pitch of the catamaran with the frequency of the waves.

After you learn the behavior of your boat in chop, you will find that you can alleviate the pitching to some degree by either speeding up, slowing down, or falling off and tacking upwind rather than going directly into the seas.

I can remember times in Fiji, the Red Sea, and the Greek Island where severe chop was a problem, and we adjusted our speed to deal with it. Usually I motor directly to windward on only one engine, but sometimes I will turn on the second engine to change the frequency of the pitch to get it out of phase with the chop. Sometimes I slowed down. Sometimes, falling off and motorsailing under mainsail makes a big difference in boat motion. One time in the Greek Islands, I just turned around and waited until the next day.

The pitching motion of a cat when moving to windward is relatively quick and makes walking on the foredeck a challenge. A monohull has a slower, less sharp pitching motion that feels better to my legs when I walk forward. I can anticipate the motion better in a monohull, but I feel like I am staggering when I am going forward on my cat because I can't anticipate the quick pitching motion. Therefore, I am extremely careful when going forward under really choppy conditions. On all other tacks, the motion of Exit Only is comfortable and feels good under my feet. It has much more of a monohull feel sailing off the wind.

[David M]

If you think about it, a lead keel acts as a dampener. Much like the flywheel on an engine. Cats simply don't have that kind of moment arm sticking straight down into the water. It relates to Newtons first law of motion. Cats have a faster pitch period compared to a similar length monohull...essentially. Putting a few hundred pounds of weight at the top of the mast would have the same effect...obviously though in reality you would never do that. That's my theory at least.

[Alan Wheeler]

Does anybody have a link to that large monohull that was half out of the water sailing to windward? It's on this site, somewhere

It's my favorite photo and I have it as my desktop background. She's a 53ft Mason and that ain't no chop it's in. That is a much bigger seas than it looks.
http://www.cruisersforum.com/gallery...searchid=16404

My boat just slices through anything to 1m as if it isn't there.

[David M]

Great pic!

[catty]

Originally Posted by ssullivan

Ok,

I saw a very large, new 47-55ft cat today pounding up the Chesapeake with me. Its bows were *leaving* the water completely on every other wave, while mine were flailing skyward.

I've been asking about this for a long time, but got very few responses. Is this a weakness of cats that nobody wants to admit or talk about??

This is certainly how they are all designed and the bows fly up skyward, pivoting about a point somewhere near the helm/companionway door. It was very dramatic (and dare I say worse!) on this large, newer cat I was motoring into the slop with.

BTW: The slop was so bad (or bow flying was so bad) it shot my forward cabin sole into the air, then down into the bilge below where it normally rests. I also took water over the bridgedeck - every 10th wave or so. Rough stuff. Very steep.

Yes. this is a trait of all cats. Some worse than others. Yours should be pretty good though with a fair amount of buoyancy in the ends. Early wharrams and crowther spindrifts were notorious bouncers.

Basically, as a cat by design can not roll it tends to pitch as its the only motion left at its disposal to dissipate energy.

Cats are good at many things, but going to weather in slop ain't one of them. Centralize your moveable stuff and and hold on.

[ssullivan]

Thank you. Good posts.

Dave (Maxingout), your analysis and explaination are exactly what I have experienced and found out in general on this delivery. The motion is annoying as heck pounding into the chop/slop. I did throttle down and head off (same as I would do on a mono) to reduce the motion's severity, but then I ended up at a VMG of about 3 knots. Burning through deisel to get 3 knots in discomfort... ok.... this was the real reason I anchored. Too cheap! ha ha


But, it's good to hear this stuff. I had been thinking I was crazy every time I mentioned it on the forum and got tumbleweeds and a dusty breeze blowing by my thread.

The photo of the Mason 53 is just a little bit different in motion. What you see there is a boat that has hit something that has made the bow leave earlier than the stern. I doubt that boat did that exact movement on each and every wave it hit that day. When I go to weather in a mono (a good one), it rides up and over the wave slowly, with its keel staying put, the bow and stern being mostly level and the entire boat heaving up and over, feeling more like I'm taking an elevator up over the wave.

I think only a cat owner who has been on both a cruising mono and a cat in these conditions can appreciate the difference. It is a rather large difference. I'd have to say, this is one to chalk up on the score board as monos are better than cats. It may be the first one I've found, but hey... I'm not here to say cats are the best. I'm here to be honest.

Going downwind and sailing to windward at a manageable angle, they are often more comfortable in motion than a mono, but in this case, they are definitely not.

Oh yeah... and my anchorage got "rolly" last night. Was very happy to have a cat for that.

[ssullivan]

Originally Posted by kevinmac

What would you estimate the wave height at, when you were seeing this bows out of the water thing, and had green water over your first set of ports frequently?

Kevin

I'd estimate the waves at a size of "tiny."

They weren't large at all. My old Gulfstar, motoring to windward like this would have ate those things for breakfast, spraying out spray to the sides and sitting mostly still.

They were maybe 4-6ft chop, but very *very* steep and annoying. It had more to do with the frequency than the size. They would throw my (and the other cat's) bows up high, then on return they would splash/smash hard, digging into the next oncoming wave, or falling in the pit behind the wave, allowing water up on the deck. The water on deck got up to those large ports in the photo, and was such a splash sometimes it ended up in my dinghy (on the davits!)

I think this is one of those special skills regarding piloting a cat and this is how cats are different from monos. I'm trying to think of a comparable thing with a mono... here it is:

When going dead downwind wing-on-wing in a mono in rolly seas, you have to be very careful not to gybe the main from the rolling motion. It's a difficult thing to keep track of and you have to pay a lot of attention. It's also uncomfortable and annoying having the boat roll all over when you are trying to manage wing-on-wing. On a cat, in the same conditions, you have no rolling, so you have a much *easier* time running wing-on-wing than on a mono in that scenario.

So these are some of the differences between the two designs. Each has a negative. Each has a positive. They are tradeoffs, afterall.

[David_Old_Jersey]

Originally Posted by ssullivan

I'm trying to think of a comparable thing with a mono...

When reading the thread the mental comparison I came up with was like a planing Power boat in a chop.

I am guessing that as you have not mentioned it that this "hobby horsing" is not also knocking you back and therefore decreasing your speed badly, just a case of more going over (the bows anyway!) the waves, rather than more through.

Too lazy to Google ....but how far you now? over half way? a few more weeks?

[Hud3]

We sailed from Virginia to the Caribbean, up and down the islands, and back to the Chesapeake via the Bahamas and Gulf Stream in 2004-5.

The absolutely WORST, MOST UNCOMFORTABLE sailing we had on the entire voyage was in the Chesapeake on our final leg to home.

The breeze picked up to about 20 from the NE, and kicked up some short chop, only 3-4 feet, but the waves were such that our bow was going 15' in the air and plunging down to scoop up green water.

I ended up having to tack "up wave" instead of "up wind", finding the right angle on the waves to minimize the insane pitching. BTW, I have 9,000 lbs of lead in the keel.

[2Hulls]

Originally Posted by Hud3

The absolutely WORST, MOST UNCOMFORTABLE sailing we had on the entire voyage was in the Chesapeake on our final leg to home.

A big ditto.

Worst chop I've ever been in was on the Chesapeake.

Sean, that was no new 47-55 ft cat. An FP Belize 43 at most. More likely a 38 or 42. The other guys' always looks bigger.

I've seen the windward bow of my boat all the way back to the bridgedeck come out of the water in big chop going to weather. It's an opportunity to see how your bottoms look.

Dave

Dave

[ireaney]

99.9% an FP Belize 43.

All boats, monos, multi's etc etc will pitch and behave very differently in different wave cycles depending on speed, direction, weight location etc, but I agree to a point that multi's will be more susceptible to choppier steep wave formations as they do not carry the weight like mono's.