Fat or thin ?

[alec]

[ QUOTE ]
The amount of water being pushed about is proportional to the displacement of the boat. The shape (wide versus narrow) has little to do with it. In general terms, narrow tends t be heavier for a given LOA, so the reverse of what you have said is true.

[/ QUOTE ]

Possibly, I don't know.

I do know that cats can go very fast and don't plane.

It's because they have very narrow hulls. I liken this to my ground breaking theory as mentioned in my previous address.

 

[flaming]

The only issue I have with cats is the motion.

I delivered one last year and I have never been more glad to get off any boat.
Yes it was quick, but the quick, jerky motion made standing very hard and even when sitting you constantly felt like you were about to be thrown bodily from your seat.
And we had a F3 max!
Keels give damping.

(Waaaaaay off topic I know)

 

[copterdoctor]

[/ QUOTE ] Yes, and note also the unpleasant tendency of broader boats to slam in head seas, shaking the very teeth out of the skulls of their crews.



[/ QUOTE ]

I think the best thing to do in any weather is to take them out and leave them in a glass anyway.

/forums/images/graemlins/laugh.gif

 

[Sixpence]

[ QUOTE ]
(Waaaaaay off topic I know)

[/ QUOTE ]

Yes , this seems to have developed into yet another one hull good , two hulls better , thread /forums/images/graemlins/confused.gif

 

[Bergman]

Fat or thin

Wide or narrow not really the question.

Colin Chapman knew the answer:

If you want it to go faster you must add lightness

Simple

Light means quick heavy means comfortable.

Whatever boat you look at will be a compromise between these two

Catermeringues do well on speed because they are light and win on comfort at the cost of having to pay for 2 boats instead of one.

Think I'll duck for cover now to escape the feline hoards

 

[heerenleed]

Re: let me put it this way

You may be quite right, especially in rough weather. OTOH I don't want to be too biased by my own preferences.
cheers

 

[Colvic Watson]

[ QUOTE ]
Quote:
(Waaaaaay off topic I know)



Yes , this seems to have developed into yet another one hull good , two hulls better , thread

[/ QUOTE ] I'm afraid that will always be the conclusion to the multi/mono question /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif

 

[Sixpence]

Ah , but I intended dealing with the seperate issue of extreme drag factors caused by multi hulls seperately /forums/images/graemlins/wink.gif

 

[fireball]

[ QUOTE ]
extreme drag factors caused by multi hulls

[/ QUOTE ] Are they all cross dressers? /forums/images/graemlins/laugh.gif

 

[Sixpence]

I refuse to be drawn on that on the basis that , well , ahem , no comment /forums/images/graemlins/grin.gif

 

[bilbobaggins]

[ QUOTE ]
dealing with the seperate issue of extreme drag factors caused by multi hulls seperately

[/ QUOTE ]

Worried about 'extreme drag factors', Trevera? There's an easy solution you should try.....

Just be a bit careful with the power on the corners.... They tend to over steer a bit, just like the old 911, then the back-end breaks away!

/forums/images/graemlins/grin.gif

 

[mel80]

One aspect that hasn't been mentioned (I think) is the effect on weather helm. A beamy hull, when heeled, will have a much greater underwater asymetry than a trim hull and will have much more pronounced weather helm (especially if the hull lacks fore and aft symmetry).

Of course, a beamy hull will be much stiffer so will be much less prone to heeling, but the effect can be huge. A well balanced, trim hull can still be light as a feather with the side decks underwater whilst a beamier hull would become unmanageable at much less of an angle.

One effect of this is that a trim hull will be much more forgiving if you are carrying too much sail.

 

[Twister_Ken]

>One aspect that hasn't been mentioned (I think) is the effect on weather helm. A beamy hull, when heeled, will have a much greater underwater asymetry than a trim hull and will have much more pronounced weather helm (especially if the hull lacks fore and aft symmetry).<

The corollary to this is that a beamy boat can broach up to windward like a snake going for a rat if suddenly overpowered by a gust. Which is why some of us won't sail close upwind of a certain lederhosen-wearing brand of boat on a breezy day.

 

[jonjo]

You might want to read some reviews of the Hunter Mystery 35 which is one of the few classic narrow shaped designs to arrive on the market in recent years.

Generally the British yachting press heaped praise on this model and its sailing characteristics but there were some mutterings along the lines... "I had forgotten how far a classic design heels before getting up to speed".

The debate will run and run, even with 100’s of years of experience the argument continues at the Royal Navy.

 

[Sixpence]

As you mention the RN I have to admit that some reading a few years back is what's prompted the question . Quite a while ago there was some discussion in RN circles about the merits of submarine hull shape , with some proclaiming that the traditional sleek cigar shape wasn't as efficient as a shorter , much stubbier shape would be . I don't know if there were any conclusions to that though

 

[jonjo]

I was thinking about debates over hull design for the surface fleet. From what I understand today's RN is still oriented towards maintaining an all weather anti submarine capability in the North Atlantic cause you never know when those dodgy Ruskies might come sneaking around the North Cape.

If however the objective is the most weapons platform bang for the buck or chasing the Iranian Revolutionary Guard around the Gulf, then broad beam should be favoured.

 

[fireball]

Why haven't they made a cat-sub ?

 

[Sixpence]

Ah , but the RN surface fleet isn't comprised of vessels with large bulbous lumps on the end of a keel so I'm just trying to understand how that affects performance . I think most are in broad agreement that narrow and wide beam have different carachteristics but how does the weight on the bottom of the keel affect things . Not intending to go into manufacture or anything like that but it would be nice to understand how different shapes affect things