Is there an existing hull shape that fits this bill?

Yes, I love it. I love to make them puke in rough conditions too.

A monohull cannot work for this proposal. Obviously, it is a proa/outrigger or tri.

 

Large outboard would be necessary when pushing the 1500lbs load into a harbor chop and wind. Hopefully, it would be enough in that case. In the case of just the wife and I with light provisions, 8HP means 14 knots or something cool like that. Or, we throttle way back and use no fuel.

Oh, I also already own the Honda BF8, so it would be best to use it.

Catamaran cannot meet the narrow beam requirements of docking on a crowded float. Power tri or proa can. Catamaran also cannot be quickly hung from davits like power tri or proa with retracting ammas or outrigger.

 

Speed requirements are "as good as I can get." Probably just a few knots against wind/current/chop with full load, and as much speed as possible on the skinny waterline profile with just the wife and I.

 

Why not a narrow beam catamaran? Will a tri/proa be stable enough in retracted configuration for guests embarking/disembarking? To make one stable enough in retracted configuration the outrigger/amas will need to be high volume. Then what's the point of the complications and mass of retracting system?

I assume you will want to go sailing and earn money as soon as possible after your big boat is finished. If so there is considerable value in the quickest to build configuration which meets your requirements. A bulletproof retracting system will add time, mass and cost.

Any constraints on height when stowed on board/hung from davits?

 

You're right about that. A retracting system would be a bear after the whole mothership build.

I figured a proa/outrigger would be the most simple, but then yes, there are some boarding stability issues.

I narrow beam cat would probably require an adjustable beam though, wouldn't it?

Picture the most crowded local dinghy dock you can think of. For me, it's Block Island, Rhode Island on the 4th of July.

You are usually 2 dinghy lengths out, with an inner section of dinghies you have to board and walk through to get to the actual dock. You leave a slack line to keep your dinghy floating way out in the "second row." Other times, you are very lucky and you find a little "half beam" spot and power in, jamming your RIB between all the others. We are talking hundreds of dinghies on a 50'-75' dock.

With a catamaran, I could see not being able to dock there at all, unless the beam could be reduced to the same as a normal RIB - 5ft, I believe.

Not sure where people would sit or how they would be protected from spray in your catamaran thought. I can only seem to picture Hobie style hulls with a big, flat deck. What are you thinking of?

Height constraint is (mostly) a non-issue since there are no davits installed yet. I can haul it as high as the deckhouse roof, I suppose, though it would block the view from the helm. It's already a 3' distance from calm water to the bottom of the bridgedeck, then another few feet to the top of the aft beam. So, 6ft from the water before it even begins to peek up above the aft beam.

 

Here's a pic of a catamaran dinghy http://www.boatdesign.net/gallery/showphoto.php/photo/11471/ppuser/12438 I used to have a mold for this but sold it, it was 2.3 m x 1.3 m , a stretched out one of these might suit, I also whilst cruising had one similar in aluminium, on that one though the tunnel was also a longitudinal seat.Jeff.

 

Another idea. An inverted-V "Hickman Sea Sled" type hull. Mystic Seaport has a Hickman Sea Sled which is 13' 2" x 4' 1". Stretch it to 16' if more capacity is needed. Not great in a step chop but every design has its downsides.

 

It needs to be something highly polished and impressive.
It will be the first impression to your paying guests.
Can't be a contraption like I might build for myself.

 

See this sketch of 15 by 4 cat.

 

Ha ha ha!

Yes, it absolutely has to be perfectly polished, shiny and cool looking.

 

Then don't let me build it!

 

Hoyt, what do the hulls look like underwater on that?

I would be looking for round chine or many chines to approximate round.

Looked at the sea sled... maybe... maybe...

I guess I have a lot of thinking to do on this.

 

You could make it with rounded chines, with corecell strips laid up on rounded bulkheads just as you made the large hull, then glassed. It would be much easier than the hulls you already built. It could even be made to resemble the larger craft except open structure to save weight.

 

A proa with a large enough outrigger would not be a problem in use just get your guests to board one at a time and seat them in the vaka. You can play around with float volume to achieve the right balance and due to it's powered configuration you dont need much beam. I like the idea I've seen on some power proa's where they up the volume of the float and make the area between the float and vaka a cargo load area looks very user friendly and accessible for stores while still having decent seating for guests.

 

Write your requirements, desires and constraints and categorize as:
- Legal
- Absolutely must be met
- Very, very desirable
- Desirable
- Nice to have

Review what you've written and see if some are design specific. Re-write any which are in a non-design specific manner.