Catamaran sailing issues..

[LydiaS]

Hi all, anyone with good catamaran sailing knowledge out there?? We bought a 49ft catamaran fairly recently, and find that in any kind of head on swell, especially the 1m med swell, the cat bounces around like crazy and has incredibly loud pounding underneath. Is this normal for a catamaran?? It also isn't balanced properly, the bow is higher out of the water than the stern. How much would this affect the bouncing/pounding does anyone know? We're considering adding ballast to the front to level her out, but then there's the disadvantage of adding weight to it, which seems to be a big no no for a cat.

It makes life pretty uncomfortable for longer trips, our kids don't like it at all.. We were monohull sailors, so we're just not sure if this is to be expected or not. She sails well downwind though the speeds we're reaching are nothing like we hoped either. 8-10knot max. Any help much appreciated!

[Barra]

Not familiar with your boat but it sounds pretty odd for a 49 foot cat to pound and bounce the way you say in 1m chop even if motoring straight into it near full revs. Even more odd that the stern is so low vs the bow that you are considering ballast.

Have you got any pics? Is there some extreme or unusual weight loaded aft?

There is definitely something wrong from what you say....

[LydiaS]

Hey I don't have a good picture sorry, I'll have a trawl through my husbands pics, but it's about 8-10cm higher at the bow compared to the stern, do you think that amount would make much of a difference? It does have a heavy dinghy so it's better without it, and we're considering trading it in for a much lighter one.

[belizesailor]

What make & model of cat?

Sounds like overloading is one of the issues, typical of cruising boats (including mine)...too much junk in the trunk. Can you eliminate weight in the sterns or at least shift it forward?

[Canibul]

Is there some kind of users group for whatever cat you bought? A catamaran that big shouldn't be slamming in one meter waves. Sounds like you got a lazarette full of chain or water.

[Ex-Calif]

The spec bridgedeck clearance for you boat is .81m Compared to the Leopard 48 at .91 - I looked at a few others and while your boat seems the lowest it also appears "in range" it seems for this class of boat.

Light in the bow is not necessarily heavy in the stern. You may have low water tankage light anchor/chain whatever. A heavier bow may allow the boat to "penetrate the swell rather than be lifted by it.

All boats will pound directly into a sea and it is very hard on the boat.

I am not a cat guy but there are some very seasoned ones who may help out with boat handling to reduce slap and pounding. Maybe most cat guys only travel downwind -

Another strategy may be to bear off and don't take the swell head on. The shortest route in sailing is never the straight line. Also are you sure it was only a 1m sea? That is really low.

[Palarran]

I wouldn't think a Nautitech would slam as much as your describing. There is a difference between waves slapping the hulls and slamming them. With a slap the wave bounces off one hull and then hits the bridgedeck with a wap sound. Slamming is when the boat comes down on a wave which stops the movement. The boat will shudder and shake and the boom sound is pretty loud.


Were you trying to motor into the waves at the time? If so, you are better to motor at 30 degrees off the wave train to stop hobby horsing. Sailing at 45 degrees should stop the slamming and you will have very little slapping. Just avoid straight into the waves.


Also, don't add any weight but try to distribute it better. I wouldn't move any to the bows but maybe see if you can move some from the stern to the middle of the boat. It's difficult to shift enough to make a difference though.


You could try ear plugs for the kids and strong cocktails for the adults Or, reverse that and the kids will really have a fun time.

[Dave852]

Never add ballast to a cat. Get rid of the dingy, no reason to have one that weights more than 53kg. For 53kg you can have an 11'rib. Do you have weight that can be moved forward some? Of course you do. Redistribute, toilet paper at the ends, dive tanks/weights/spare anchors/can goods towards the center. If fact no need to carry can goods nowadays. Then play around with your course, some times a 5-10 degree adjustment will make a big difference. And finally remember that an occasional slam that feels like it going to tear the boat apart will in fact not, they are built to take it.


Sent from my iPad using Cruisers Sailing Forum

[atoll]

sounds pretty normal to me,better get used to it!

bearing off will help,but waves in the med are notoriously "square",and get up very quickly.

if you must motor into the prevailing winds in the med,better to wait for a lul in the weather,winds will be stronger with an approaching low to the north west over the Biscay and mainland Europe.

[boatman61]

If your gonna motor into the wind.. and in the Med waves usually = wind.. try motor sailing.. just the main or a reefed combo to suit conditions.. run on the windward motor.. then change after a tack..
The force the sails exert help hold the boat down in the short seas one gets in the Med..
And.. Atolls right.. cats are noisier than mono's.. just gotta live with it..

[Southern Star]

Lydia, it is very difficult to assess your situation based upon the information that you have provided. Do you have experience on any other cats with which you can make a comparison? Regardless, I agree with a couple of things that Ex-calif has said:

1. The designed bridgedeck clearance is relatively low for a cat of that size and, depending upon whether the boat was built to the design weight (and how you have loaded the boat), it may be significantly lower than that in reality.

2. In a cat, one must remember when sailing to windward the VMG (velocity made good) is the critical factor - not how high you are pointing. Bear off until the motion becomes more comfortable and you will likely find that it is not only less bone-jarring, but faster (slamming/pounding impedes progress, of course, but most cats also slow dramatically when 'pinched').

The Nautitech also has relatively narrow hulls and while this tends to improve performance, it also reduces the load-carrying ability. While cats have a tremendous amount of storage space in comparison to most monohulls, one must resist the temptation to overload the boat.

In addition, the boat should be sitting on her lines. You refer to your heavy dinghy and of course, this would be a factor (although a recently designed 48 foot cat should be capable of carrying a pretty large RIB and outboard). If you are carrying heavy stores aft, you should try to find locations forward in which to store them.

While most think of pounding as occurring towards the leading edge of the bridgedeck, in fact many boats tend to pound further aft. If the aft end of the bridgedeck is down by 8-10 cem, this reduces your bridgedeck clearance aft by about 10 to 15 %. A significant reduction for a boat that is already marginal in terms of clearance.

Finally, it would seem that your boat is a new (or relatively new) model. Did she sit that way at the time of commissioning? If so, it would suggest that the designer/builder got it wrong and it would not surprise me to see a lengthend version (with hull extensions aft) on the market in the near future. This, of course, will provide scant comfort for you, but there is always the possibility that if it is a design/manufacturing flaw, Nautitech would be prepared to provide some reduction in cost in adding hull extensions to your boat.

First things first, though. Avoid motoring/sailing to close to the wind in any kind of significant chop. Move storage of heavy items forward (and reduce the amount of gear that you are carrying to the essentials). As Ex-cal points out, if your water storage tanks are foward, try to keep them full (and if not, consider moving them forward - not too difficult with flexible tanks). Even things like the location (and size) of the house battery bank can be a significant factor. In simple terms, move the weight forward rather than adding ballast as that will only further reduce your overall bridgedeck clearance and performance.

Brad

[atoll]

Originally Posted by boatman61

If your gonna motor into the wind.. and in the Med waves usually = wind.. try motor sailing.. just the main or a reefed combo to suit conditions.. run on the windward motor.. then change after a tack..
The force the sails exert help hold the boat down in the short seas one gets in the Med..
And.. Atolls right.. cats are noisier than mono's.. just gotta live with it..

+1 a reefed main or unreefed main pulled in tight midships,with the boat heading about 25-30 deg off the wind will also make the motion smoother,and give 1-2knots of drive.

also in the med you can also gain a bit when heading west by using the diurnal variation.
Diurnal temperature variation - Wikipedia, the free encyclopedia

with the winds more NNW at night,and more west as the air temp heats up,so stb tack during the day and port tack at night.

[Ex-Calif]

Originally Posted by atoll

.

also in the med you can also gain a bit when heading west by using the diurnal variation.

Now you're just using big fancy words to impress me and get inta my pants -

I thought da-urinal was where one drained the snake...

[atoll]

Originally Posted by Ex-Calif

Now you're just using big fancy words to impress me and get inta my pants -

I thought da-urinal was where one drained the snake...

having fought my way the 2000miles into headwinds up the med 7or 8 times I reserve the right to use fancy words.......and dirty tactics

[2Hulls]

Hi Lydia - let's take this one thing at a time:

Originally Posted by LydiaS

We bought a 49ft catamaran fairly recently, and find that in any kind of head on swell, especially the 1m med swell, the cat bounces around like crazy and has incredibly loud pounding underneath. Is this normal for a catamaran??

"Head on"? Do you mean on the nose motoring upwind head on, or close hauled sailing upwind?

If motoring head on, yes, this may produce an occasional bridgedeck slam, but no worse than most other cruising cats. If you are not yet accustomed to the pitching motion of cats upwind, perhaps this is part of it. This would be worst motoring upwind.

If sailing upwind close hauled, at what apparent wind angle? Perhaps you're pinching too much. Foot off a bit and see what happens. Most cruising cats (those without boards) shouldn't be sailed as tight upwind as you may be used to in a good sailing mono. You may find your best VMG upwind is further off than what was your best VMG in a mono. Separately, what sailing experience do you have?

It also isn't balanced properly, the bow is higher out of the water than the stern. How much would this affect the bouncing/pounding does anyone know? We're considering adding ballast to the front to level her out, but then there's the disadvantage of adding weight to it, which seems to be a big no no for a cat.

Correct, don't add weight - but maybe move around what you do have. Do you have chain or rope rode? If you lower the dinghy into the water, how much does this improve the trim? How much higher is the bow? Can you describe this relative to the bottom paint line, i.e., X inches/cm at the bows and Y inches/cm at the sterns.

She sails well downwind though the speeds we're reaching are nothing like we hoped either. 8-10knot max. Any help much appreciated!

What were you expecting and in what conditions are you getting 8-10 knts? Dead down wind, or broad reaching? What sails? What do you get with apparent wind on the beam as a % of true wind speed?

Dave