Multihull Size in a Mono Hull Package

[Tscott8201]

So everyone knows that cats have more square footage per linear foot than mono hull boats due to the wider beam. Also, in general the cost of a mono is considerably less than a cat for similar lengths. But that equality doesn't help much since the square footage on board is so drastically different. So when comparing monos to multis, what lengths of each design are similar in square footage (i.e. if one were to look at the room on a 40' cat, what length would a mono need to be to give the same space?).

Also, what other factors creep into the picture as the size of a mono increases that would affect maintenance costs and sailing ability as it pertains to a small family. For example, I assume the sail plan on a larger mono would become substantially larger and therefore harder to handle as compared to a cat of similar square footage. Draft would also seem to become a factor as the drafts on a mono become much greater as they grow in size.

Any information that would make comparing apples to oranges a little easier.

Tom

[Sand crab]

The general consensus is a mono would need to be 30 to 50% longer to have the same accommodation. Sails on a mono would be bigger (although many older designs are ketch rigged) and draft too. Deep draft is good for a mono in the open ocean. Even on larger cats the sail handling is much easier because of that lack of heeling and wide flat decks. Most cat sailors don't generally wear safety gear except sometimes at night or rough weather while on a mono it's just about standard if going forward. Downwind not so much.

[Steadman Uhlich]

Consider a Catamaran that is 44 feet may commonly have FOUR double staterooms with FOUR heads.

To find that on a monohull, I think you would have to go to a 70+ foot mono.

I would prefer to handle and replace ($$) the sails (and other gear) on a 44 foot cat, rather than a 70+ foot mono.

[a64pilot]

I don't think you can get a comparison, I assume your looking for a answer like a 40' Cat is equivalent to a 60" mono, but you just can't. too many variables. Can't even make that statement with 40' monos, big differences between different boats.

[Tscott8201]

Originally Posted by a64pilot

I don't think you can get a comparison, I assume your looking for a answer like a 40' Cat is equivalent to a 60" mono, but you just can't. too many variables. Can't even make that statement with 40' monos, big differences between different boats.

I'm not really looking for a direct comparison, rather a discussion on some of the factors that pop up as you try to get as close to equal accommodations as possible from the 2 designs.

Tom

[a64pilot]

You know, I think it's personal preference.
On a Cat you get this huge salon, usually with big picture windows, a very "open" space.
On a mono you get a much bigger tube than a Cat, only one though, but no picture windows, can be to some almost claustrophobic, others consider it cozy and warm.
The very few that I have seen are really very different boats than the monos, seems to me the most they have in common is they are both on the water.

[Cheechako]

One comparison: a 47 foot (Perry) mono I had was down 5" on the waterline with the gear I had on it. That gear went to a 42 ft cat with only 1.5+" immersion.

[Sand crab]

Beneteau makes both. Why don't you compare the Oceanis to the Lagoons and then you'll have more of an idea.

[robert sailor]

Another idea might be to figure out the cost per sq ft of living space between both styles.

[tbodine88]

What all the above is probably true, but while I was living in my Ericson 32 in Antigua which had I figure MAYBE 200 square feet of living space, a French 22 foot catamaran came in with a leaking bow. While he sat on the hard at the Jolly harbor boat yard, he invited me aboard for a beer in his 22 feet there were three state rooms an gym, a large kitchen/bridge/solon and swim platform, plus trampolines.
I could comfortably house 4 people, he could find space for twenty on a day sail and maybe 6 or 8 over night.
My very used Ericson was 15K, his used Cat 120K.

[Sand crab]

22'? Are you sure?

[Steadman Uhlich]

A comparison of two 40 foot yachts:

MONOHULL
Beneteau 40 2007

LOA = 40ft
Displacement = 18,210 pounds
Ballast = 5,198 pounds
SA = 678 square feet
SA/Disp = 15.73
Ballast/Displ = 28.55%
Displ/Length = 208.30
__________

CATAMARAN
Lagoon 410 1997

LOA = 40ft
Displacement = 15,961 Pounds
Ballast = 0
SA = 957 Square Feet
SA/Displ = 24.2
Disp/Length = 126.93
Mast Height = 60 ft

[StuM]

I'm with Sand Crab. 30-50% longer is a fairly good figure with faster cats more around the 30% end and condominiums towards the 50% end.

[StuM]

Originally Posted by Sand crab

22'? Are you sure?

Sounds more like 22 meters from the descriptions

[Dockhead]

Originally Posted by Sand crab

The general consensus is a mono would need to be 30 to 50% longer to have the same accommodation. Sails on a mono would be bigger (although many older designs are ketch rigged) and draft too. Deep draft is good for a mono in the open ocean. Even on larger cats the sail handling is much easier because of that lack of heeling and wide flat decks. Most cat sailors don't generally wear safety gear except sometimes at night or rough weather while on a mono it's just about standard if going forward. Downwind not so much.

Right -- very well formulated.

Displacement per unit of hull volume is greater in monos because of the ballast. This is a fundamental disadvantage of monos. Which, however, does disappear gradually as you add payload.

Like for like when comparing monos and multis is obviously not by length. A 40' cat will have roughly the same hull volume as a 50' mono. But the volumes are differently distributed, so even with the right formula, it's not quite fungible.

What that means is that the 50' mono has a 15' (or so) beam, so there are no narrow spaces, whereas the cat will have the accommodation stuffed into two rather narrow hulls. But the cat has the salon and galley in the bridgedeck, with a panoramic view. They're just different!