Quadrimaran: what do you think?

[DrHans]

Hi All! I just designed the "Qmaran 46", with 4 hulls.
I believe it may have big advantages over performance cruising cats of the same length.
What do you think of it?
I'd love to hear your thoughts.

[Benz]

You should build it and tell us how it does.
How much living space is inside each of those skinny hulls?
How much wetted surface is there compared to two hulls with same displacement?

[HankOnthewater]

Hi Hans, is that a catamaran with outriggers? sorry could not help myself
I always like to see new things, even though I am a one-hull type of person (I am a person of simple means and of a simple mind).

I think you will find it hard to break into the market, that is generally very traditional. I can see two openings: get it into charter, and the clients/buyers will follow. Or get a couple of 'influencers' to use /sail your boat. Then the younger public might follow.
Good onya! en goed geluk

[DrHans]

The inner living space is one of the great advantages of the Qmaran; squeezing double beds inside cathulls makes those hulls too wide and the beds too narrow. So better to lift the beds above the hulls. The Qmaran layout is as follows:

[DrHans]

Draft of the Qmaran will be 23mm per ton; so for ~15 ton it would be just 35 cm (or 14")!

[Benz]

^^That's a neat use of space. Good on you for thinking outside the box.
Have you got as far as building a scale model for tank tests?

[Benz]

One last comment: one of the biggest bummers of a cats is low bridge-deck clearance. It's one of the reasons I have no interest in multihulls. Given that there's bunks in the bridgedecks, are they high enough that slapping waves aren't going to drive people nuts?

[DrHans]

I just built a computer model so far. But on my website I posted a visual comparison with the Outremer 45; to compare layouts, sections, sail area etc - all to scale. You can also see the bridgedeck clearance there:

[DrHans]

Each of the 4 spacious cabins looks like this, with a very large bed:

[DrHans]

[GordMay]

Greetings and welcome aboard the CF, DrHans.

[DrHans]

Sideview of the Qmaran:

[ggray]

Hate to be a naysayer, but as mentioned, you have an inordinate amount of wetted surface.

Length helps speed, resistance to pitch-poling, comfort, probably other things, more than does beam.

You are going to have more structural issues. Imagine being crossways in a wave trough, outer hulls pushing up and weight of inner hulls/cabins pushing down.

Many cats have berths in (on?) bridgedeck same as your model so wide hull or narrow berth is a not a relevant issue.

You are showing flat bottom hulls, not a good idea.

Big question is, for what reason do you need 4 hulls? Marina fees?

[marcjsmith]

Trying to imagine tacking this beast...

[valhalla360]

Originally Posted by DrHans

Draft of the Qmaran will be 23mm per ton; so for ~15 ton it would be just 35 cm (or 14")!

A few thoughts:
- Flat bottom hulls aren't very efficient on sailboats. Change that and draft goes up.
- With nothing in the water, expect it to make a ton of leeway while sailing. You can add keels but then more draft.
- It won't have as much righting moment as a typical catamaran as much of the buoyancy is towards the center. I expect it to act more like a trimaran where heeling will be more pronounced.
- A shorter mast does not make for a lower center of gravity. In fact, it looks very tall which will make it a horror to dock as the wind can catch a lot of the high slab sides while there is little below the water to stop it.
- Beds on the bridge deck are pretty common. We had a full queen size on a 34ft cat. With a modification, it was possible to get your full 2m width.
- They can make cats wider but pitch poling starts becoming more of a risk than capsize.

This looks similar to some of the big trimaran designs. As the central hulls provide negligible righting moment, a single hull could take their place fairly easily.

Since you aren't trying to fit in any kind of slip, just go longer and leave the extra length on the ends empty (could go cat or tri for the same effect). It will add negligible cost or weight but significantly increase the hull speeds without nearly as much wetted surface issues.