Multihull or Monohull

[Oliver L.]

Hi, Guys!

I've got a question about the mini keel vs. daggerboard on multihulls. If I look at my new beauty (see attached), the keel depth ends within a few cm (or inches) of the rudder. And behind both (in my opinion a very nice design) the saildrive.

If I were to raise a daggerboard, my rudder would become the lowest point of the boat, which in my opinion would be immeasurably more vulnerable to even minimal contact with the bottom. Granted, any contact hurts - but if I really screw up and make first hand acquaintance with a reef, the worst that can happen with the design above is I lose half my water storage, back out and try again somewhere else.

I've sailed Catanas, so I know they point higher - but I also remember the incredible pounding the daggerboards caused when the boat accelerated past a certain speed. And since I don't plan on racing (well, at least not officially...) at least for now I am pretty happy with the design of my boat.

...comments? And I DEFINITELY don't want to back up to the beach - without a diver around to watch it sounds like an invitation for a very expensive service call...

Oliver

[Mr B]

Originally Posted by Oliver L.

Hi, Guys!

I've got a question about the mini keel vs. daggerboard on multihulls. If I look at my new beauty (see attached), the keel depth ends within a few cm (or inches) of the rudder. And behind both (in my opinion a very nice design) the saildrive.

If I were to raise a daggerboard, my rudder would become the lowest point of the boat, which in my opinion would be immeasurably more vulnerable to even minimal contact with the bottom. Granted, any contact hurts - but if I really screw up and make first hand acquaintance with a reef, the worst that can happen with the design above is I lose half my water storage, back out and try again somewhere else.

I've sailed Catanas, so I know they point higher - but I also remember the incredible pounding the daggerboards caused when the boat accelerated past a certain speed. And since I don't plan on racing (well, at least not officially...) at least for now I am pretty happy with the design of my boat.

...comments? And I DEFINITELY don't want to back up to the beach - without a diver around to watch it sounds like an invitation for a very expensive service call...

Oliver

I wouldnt back that one up to the beach either, You dont have folding rudders like the Gem,

[tamicatana]

Originally Posted by Oliver L.

but I also remember the incredible pounding the daggerboards caused when the boat accelerated past a certain speed.

I'm trying to picture this 'pounding.' Could it be also described as the daggerboards vibrating in their cases? Or would it be more like a 'hum,' like the beachcats experience?

[44'cruisingcat]

Originally Posted by Oliver L.

Hi, Guys!

I've got a question about the mini keel vs. daggerboard on multihulls. If I look at my new beauty (see attached), the keel depth ends within a few cm (or inches) of the rudder. And behind both (in my opinion a very nice design) the saildrive.

If I were to raise a daggerboard, my rudder would become the lowest point of the boat, which in my opinion would be immeasurably more vulnerable to even minimal contact with the bottom. Granted, any contact hurts - but if I really screw up and make first hand acquaintance with a reef, the worst that can happen with the design above is I lose half my water storage, back out and try again somewhere else.

I've sailed Catanas, so I know they point higher - but I also remember the incredible pounding the daggerboards caused when the boat accelerated past a certain speed. And since I don't plan on racing (well, at least not officially...) at least for now I am pretty happy with the design of my boat.

...comments? And I DEFINITELY don't want to back up to the beach - without a diver around to watch it sounds like an invitation for a very expensive service call...

Oliver

Daggerboards are great when you have kick-up rudders, and either retractible drives like outboards, or shaft drives well tucked up with a strong skeg. For instance, with rudders raised or floating, and board up, we only draw 450mm - about 18 inches.

If I had fixed rudders or saildrives I think I'd want minikeels also.

I'm also interested in the pounding caused by the boards, I've never experienced that.

[44'cruisingcat]

Originally Posted by dirkdig

They don't need to hit anything to snap, just ask owners if you don't think it happens.

Sorry, I wasn't saying I don't believe it happens, but it SHOULDN'T happen. It's not hard to build board strong enough. If they are charging $6000 for replacement boards that can't handle sailing loads, owners should be getting them built elsewhere.

[D&D]

Originally Posted by 44'cruisingcat

If I had fixed rudders or saildrives I think I'd want minikeels also.

What 44cruising cat said...and the ability to 'beach' for maintenance is another big plus for mini-keels

[Factor]

Originally Posted by Oliver L.

Hi, Guys!

I've got a question about the mini keel vs. daggerboard on multihulls. If I look at my new beauty (see attached), the keel depth ends within a few cm (or inches) of the rudder. And behind both (in my opinion a very nice design) the saildrive.

You raise an interesting point, the location of the saildrive reference the rudder. It has always been my thought that the rudder should be behind the prop. for a number of reasons, firstly it gets the motor weight further forward and out of the aft of the hull, which means that the hull end doesn't have to be as fat to take the load. I also find that you can use the flow of the prop over the rudder to aid in manoeuvring. Also, I would worry about any significant reverse thrust if the rudder was a balanced spade in that the thrust may push the rudder off centre and it would become a highly unbalanced system.

But, clearly you have a view that it is a nice design - so I would be keen on hearing your thoughts as to why.

[D&D]

Originally Posted by Factor

You raise an interesting point, the location of the saildrive reference the rudder. It has always been my thought that the rudder should be behind the prop. for a number of reasons, firstly it gets the motor weight further forward and out of the aft of the hull, which means that the hull end doesn't have to be as fat to take the load. I also find that you can use the flow of the prop over the rudder to aid in manoeuvring. Also, I would worry about any significant reverse thrust if the rudder was a balanced spade in that the thrust may push the rudder off centre and it would become a highly unbalanced system.

But, clearly you have a view that it is a nice design - so I would be keen on hearing your thoughts as to why.

There may even be a thread somewhere about this...rudders or saildrives, which comes first?

Anyway it took us a while to work through it too as the rudder first seems counter-intuitive. We eventually came round to the notion, but like all things there are pluses and minuses...

The biggest minus is when operating with sternway. The rudders really need to be locked out of the picture, then steer with the engines, but for a multihull that's probably the best way to go in any close-quarters situations anyway.

The biggest plus is when operating in seaways where there is a high risk of fishing lines. The rudder effectively keeps the lines away from the saildrive.

You're probably right about the 'fat' hulls, but that too can be a beauty-is-in-the-eye-of-the-beholder situation. We prefer the fat hulls for their advantages in both load-bearing and reducing slamming...although we conceed those advantages may come at some cost in close-hauled sailing situations. The engines well aft also permits more living volumes in the hulls (as do the 'fat' hulls, of course) and less engine noise.

[SimonV]

How much money initially do you want to spend ?
How much money per yer do you want to spend ?
it all comes down to money ion the end.

[Therapy]

Originally Posted by ty.gregory

Therapy, come on man, where can I get one of dem B.S. Meters?

If you are serious...........

right click/save picture as...

Or google "jpg bs meter"

[Islander]

Originally Posted by Mr B

I wouldnt back that one up to the beach either, You dont have folding rudders like the Gem,

Front in to the beach with a Gem, Mr. B.

The rudders don't fold up enough to back in - they will get damaged.

Cheers

[Oliver L.]

Tamif, Cruisingcat,

re: pounding: the charter agent had told me I needed to retract the daggerboards fully above 8 knots. Weeeell, 8 knots came and went and it was so much fun I did not even think of retracting them. Then we heard several loud "bangs" - as if we hit something. Checked the boat, no, we didn't. Tried to see whether it was maybe the props, so put the engines in gear to stop them - wasn't that either. Finally we retracted the daggerboards, and the banging was gone. It was not continuous, but it seemed to happen whenever the laminal flow reversed itself, i.e. when the daggerboards tilted only a tiny angle and then went full speed to the other extreme position.

re: prop behind the rudder - I think you get used to it easily, but it got me one laugh already. My wife was backing in our boat the first time, and upon increasing the thrust furiously told me to keep my hands off the wheel - that she knew what she was doing. Well, I hadn't touched the wheel, but she had for the first time experienced prop wash on a large rudder going the wrong way...

Next training session: Just 10 days away...

Oliver

[Therapy]

Originally Posted by Islander

Front in to the beach with a Gem, Mr. B.

The rudders don't fold up enough to back in - they will get damaged.

Cheers

Correctomundo.

[Russell7171]

Mono hull or catamaran .... cheeze, tricky question.
A typical Kiwi - born in a dinghy. Monohull for >20 years.
Now live aboard - on a 46' Fountaine Pajot catamaran.
Again, mono or cat? Depends on what the intended use is.
Racing and weekend meanings, go for half a boat = monohull.
Liveaboard? Catamaran without question.
You spend >90% of your time at anchor, and a cat doesn't wallow in the swells.
I have seen plenty of monohulls look like a metronome at anchor - pretty scary.
Most important of all - on a cat, you never spill your drink.
Size? If doing passages, I read somewhere that delivery guys don't like delivering a cat less than 40' because of the hobby horse effect.
Sooooooo, go longer. An interesting point that the December 2011 Yachting World made in an article comparing different cats, is the new versions of both Lagoon and Fountaine Pajot are both pretty heavy (at around 42') and hobby horse quite a lot. Also, the driving station upstairs is very uncomfortable in a big sea.
Hope this is of some help. If you would like some links to my wires blog and other sailing stuff, I have a website. Still being added to, so keep on checking it out.
poulston.com is the address.
cheers, Russell

[D&D]

Originally Posted by Russell7171

Mono hull or catamaran .... cheeze, tricky question.
A typical Kiwi - born in a dinghy. Monohull for >20 years.
Now live aboard - on a 46' Fountaine Pajot catamaran.
Again, mono or cat? Depends on what the intended use is.
Racing and weekend meanings, go for half a boat = monohull.
Liveaboard? Catamaran without question.
You spend >90% of your time at anchor, and a cat doesn't wallow in the swells.
I have seen plenty of monohulls look like a metronome at anchor - pretty scary.
Most important of all - on a cat, you never spill your drink.
Size? If doing passages, I read somewhere that delivery guys don't like delivering a cat less than 40' because of the hobby horse effect.
Sooooooo, go longer. An interesting point that the December 2011 Yachting World made in an article comparing different cats, is the new versions of both Lagoon and Fountaine Pajot are both pretty heavy (at around 42') and hobby horse quite a lot. Also, the driving station upstairs is very uncomfortable in a big sea.
Hope this is of some help. If you would like some links to my wires blog and other sailing stuff, I have a website. Still being added to, so keep on checking it out.
poulston.com is the address.
cheers, Russell

All good stuff Russell. We share and agree with everything EXCEPT...

"the driving station upstairs is very uncomfortable in a big sea"

...definitely not so, in our humble experience (including plenty of big seas) of now ~18000nm on an L440...and even our racing and hardcore monohull biased delivery crew (on the voyage from Sardinia to Sydney) ended that voyage with remarks like "can't understand why all cats don't do this..."

All the rest though, we agree 100%.