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 Boat Design Forums When does a monohull become a multihull??

#16
01-03-2017, 07:18 AM
 TANSL Senior Member Join Date: Sep 2011 Rep: 300 Posts: 3,895 Location: Spain
Mr Efficiency, what I mean is that a pear can not be transformed into an apple. What do you think if I ask: when a pear turns into an apple ?.
If you define well what is a pear and, on the other hand, what is an apple, the answer is obvious : never. If you do not do it, the question does not make sense.
So, what is a monohull?, what is a multihull?. See Ad Hoc and Ike answers, they can help in this deep scientific discussion.
#17
01-03-2017, 01:29 PM
 Abby cat Junior Member Join Date: May 2016 Rep: 10 Posts: 9 Location: Blenheim,NZ
TANSL
Quote:
 You can ask if a floating object is mono or multihull but one thing we have already described as mono, can not be multi.
yea but you can blur the lines between if it is a mono or a multi depending on what the definition is.
If you are using the definition of single footprint while the boat is level you could lower the deck between the hulls of a cat until it just pierces the water when it is sitting level at stationary, but when dynamic lift and heeling moments come into the equation, there is two footprints therefore can be both??

Thanks

Nick
#18
01-03-2017, 02:10 PM
 TANSL Senior Member Join Date: Sep 2011 Rep: 300 Posts: 3,895 Location: Spain
I think we could talk about a multihull working like a mono, or quite the opposite, I do not care much.
Cheers.
#19
01-03-2017, 02:44 PM
 CT249 Senior Member Join Date: May 2003 Rep: 212 Posts: 832 Location: Sydney Australia
Quote:
 Originally Posted by Abby cat Hi yea the image was of a concept and would require much more to make it efficient but what I believe the understanding is that a hull is the bottom, sides, and deck but not the masts, superstructure, rigging, engines, and other fittings. But the difficult part is when does the bottom of the hull become the sides as to whether a boat is a monohull or a multihull. The reason that i had these thoughts is because the sydney to hobart yacht race has not allowed multihulls to race, so I have been thinking about how you could get a multihull to be, by definition a monohull so it could do the race, this is because an equivalent length racing multihull is faster than a racing monohull. thanks
The traditional answer, as others have already pointed out, is that a monohull has no "air gap" when at rest or upright.

But it's an odd question to ask in some ways. It's a bit like asking how to enter a Formula One car into a famous motorcycle race by finding a way around the definition of "motorcycle", or like using rollerskates to win a footrace marathon because you wear some cunning shoes that "just happen" to have wheel-like devices on them instead of tread. My old club has a definition of "youth" that could be stretched to allow 30 year olds to sail in its youth regatta - would you be happy if Glen Ashby used that as justification to enter and beat the kids?

If your way worked then all that would happen is that Notices of Race would become longer, more complex and full of tighter definitions. Volunteers would have to work longer and harder at drafting them. Sailors would have to work longer and harder at reading them. Races could be decided in the courts instead of on the water. Does that sound good to you?

Wouldn't it be better to admit that the Hobart is a monohull race just as the world motorcycling championships is a motorbike race, just as the Texel cat race is a race for cats and not for kitefoilers, and just like the singlehanded transatlantic race is just for singlehanded boats? If you would be unhappy with someone sailing with a full crew in the OSTAR because there was a loophole in the NoR, sailing a kitefoiler in a beachcat event or sailing as an adult in a junior event, why would you be happy with a multi in the Hobart?

It's odd that some multi sailors don't accept that mono sailors have the right to their own events, just as every other form of sporting equipment has its own events, and just as people who do many other forms of recreation have events just for specific equipment. The claims that mono sailors discriminate against multis are incorrect - the mono sailors are being discriminated against by those who claim that they, alone of perhaps all sportspeople, cannot run events just for certain types of gear.
#20
01-03-2017, 02:59 PM
 Squidly-Diddly Senior Member Join Date: Sep 2007 Rep: 304 Posts: 1,174 Location: SF bay
Quote:
 Originally Posted by Mr Efficiency There'd be a few planing cats and tris that would qualify as monos based on that continuous waterline rule.
#21
01-03-2017, 03:36 PM
 CT249 Senior Member Join Date: May 2003 Rep: 212 Posts: 832 Location: Sydney Australia
Quote:
 Originally Posted by Abby cat Hi yea the image was of a concept and would require much more to make it efficient but what I believe the understanding is that a hull is the bottom, sides, and deck but not the masts, superstructure, rigging, engines, and other fittings. But the difficult part is when does the bottom of the hull become the sides as to whether a boat is a monohull or a multihull. The reason that i had these thoughts is because the sydney to hobart yacht race has not allowed multihulls to race, so I have been thinking about how you could get a multihull to be, by definition a monohull so it could do the race, this is because an equivalent length racing multihull is faster than a racing monohull. thanks
The traditional answer, as others have already pointed out, is that a monohull has no "air gap" when at rest or upright.

But it's an odd question to ask in some ways. It's a bit like asking how to enter a Formula One car into a famous motorcycle race by finding a way around the definition of "motorcycle", or like using rollerskates to win a footrace marathon because you wear some cunning shoes that "just happen" to have wheel-like devices on them instead of tread. My old club has a definition of "youth" that could be stretched to allow 30 year olds to sail in its youth regatta - would you be happy if Glen Ashby used that as justification to enter and beat the kids?

If your way worked then all that would happen is that Notices of Race would become longer, more complex and full of tighter definitions. Volunteers would have to work longer and harder at drafting them. Sailors would have to work longer and harder at reading them. Races could be decided in the courts instead of on the water. Does that sound good to you?

Wouldn't it be better to admit that the Hobart is a monohull race just as the world motorcycling championships is a motorbike race, just as the Texel cat race is a race for cats and not for kitefoilers, and just like the singlehanded transatlantic race is just for singlehanded boats? If you would be unhappy with someone sailing with a full crew in the OSTAR because there was a loophole in the NoR, or sailing a kitefoiler in a beachcat event, why would you be happy with a multi in the Hobart?

It's odd that some multi sailors don't accept that mono sailors have the right to their own events, just as every other form of sporting equipment has its own events, and just as people who do many other forms of recreation have events just for specific equipment. The claims that mono sailors discriminate against multis are incorrect - the mono sailors are being discriminated against by those who claim that they, alone of perhaps all sportspeople, cannot run events just for certain types of gear.
#22
01-03-2017, 04:50 PM
 Mr Efficiency Senior Member Join Date: Oct 2010 Rep: 677 Posts: 5,371 Location: Australia
Quote:
 Originally Posted by Squidly-Diddly please explain
Well, it is not hard to find planing cats that have zero tunnel clearance at rest, therefore have one continous "footprint". They may not have been designed that way, but through weight increases finish up that way. However, with increasing speed the boat can rise sufficiently that the tunnel is no longer in contact with solid water, though still maybe aerated water and spray
#23
01-04-2017, 10:50 AM
 Angélique aka Angel (only by name) Join Date: Feb 2009 Rep: 1632 Posts: 1,382 Location: Belgium
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Some pics or videos or drawings of it ? - Otherwise we might get stuck in just theorie . .
__________________
Angélique
#24
01-04-2017, 11:05 AM
 upchurchmr Senior Member Join Date: Feb 2011 Rep: 579 Posts: 2,365 Location: Ft. Worth, Tx, USA
This is a waste of time, by someone with an agenda.
Does anyone else actually care?

I liked CT249's discussion, but he is being too nice.
#25
01-04-2017, 12:24 PM
 Angélique aka Angel (only by name) Join Date: Feb 2009 Rep: 1632 Posts: 1,382 Location: Belgium
Quote:
 Originally Posted by Abby cat I have attached a grey area hull whether it is a mono or a multi, I would be interested at what your opinion is. - - - click pic to enlarge - - -
The OP posted an attachment pic in post #6, the pic's URL reads:
http://www.boatdesign.net/forums/attachments/boat-design/111365d1483392339-when-does-monohull-become-multihull-rediculus.jpg
It looks like he knew the answer all along . .
__________________
Angélique
#26
01-04-2017, 05:46 PM
 Abby cat Junior Member Join Date: May 2016 Rep: 10 Posts: 9 Location: Blenheim,NZ
Quote:
 Originally Posted by upchurchmr This is a waste of time, by someone with an agenda. Does anyone else actually care?
if no-one cared there would be no responses.

"Someone with an agenda."??

I was just curious and thought I would pose a question.
#27
01-04-2017, 06:38 PM
 Angélique aka Angel (only by name) Join Date: Feb 2009 Rep: 1632 Posts: 1,382 Location: Belgium
Quote:
 Originally Posted by upchurchmr This is a waste of time, by someone with an agenda. Does anyone else actually care? I liked CT249's discussion, but he is being too nice.
Quote:
 Originally Posted by Abby cat if no-one cared there would be no responses.
Apparently you missed the word actually and the ? as it was a question by Upchurchmr to all posters . . .

Quote:
 Originally Posted by Abby cat I was just curious and thought I would pose a question.
Seems to me you were just curious which the answers might be to your question of which yourself thought the answer was ridiculous !
(at least to me that's what it looks like you mean by ‘‘rediculus’’ in the pic's URL) - (Note: I don't mind the 2 typos in ‘‘rediculus’’)
__________________
Angélique
#28
01-05-2017, 09:26 AM
 rxcomposite Senior Member Join Date: Jan 2005 Rep: 1110 Posts: 1,561 Location: Philippines
If I build the hull with corrugated GI sheet, will it be a super super multihull?
#29
01-05-2017, 11:38 AM
 Easy Rider Senior Member Join Date: Oct 2009 Rep: 732 Posts: 913 Location: NW Washington State USA
I've said "If a duck can swim all around the hulls it's a multihul."
#30
01-05-2017, 11:53 AM
 Angélique aka Angel (only by name) Join Date: Feb 2009 Rep: 1632 Posts: 1,382 Location: Belgium
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They're quick and easy to build, but as Rx says, are those Monos or Super Super Multihulls ? . .

Quote:
 - - - - - - - - click pic to enlarge - - - - - - - - - Villagers surrounding boats made from sheets of corrugated iron, lying on the banks of the River Hugli, West Bengal, India.
West Bengal - Hooghly River
Edit: added P.S. - It's as E.R. says, a duck can't swim all around all these many many "hulls", so the boats are not Super Super Multihulls . .

Here some more advanced plans for a one sheet steel boat . .

Though not adapted to corrugated GI sheet yet, as this would add some wetted surface, as well as some build difficulties . .

Quote:
__________________
Angélique

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