Help: Need optimum Hull shape for 35 foot Solar/Electric Water Taxi

[Tiki Luc]

Hi Everyone,
I'm looking to hire a designer to provide me with a 3D hull shape, optimized for the following criteria:
Boat description: 35 foot pontoon (displacement fiberglass hulls), open deck, lightweight poly carbonate roof, aluminum railings, cedar deck.
Boat Length: 35 ft
Overall beam: various from 8'6" and up, depending on analysis, (making a trailer legal model) Maximum overall beam: 12 ft
Pontoon maximum beam 30"
Power, 2x Torqeedo cruise 6kw
Target weight: 3500 lbs or less empty, 7500 lbs full load.
Passenger capacity: 24
COG with full load: 2/3 aft of bow
Desired cruise speed: 10 knots empty, 8 knots full load.

For those interested, I have built 3 boats already, based on the Skoota hull form. 24ft long, fully solar electric, 7.4 knots top speed, 4.5 knots cruise with full load, unlimited cruise when sunny. Some photos attached. I'm willing to share knowledge gained....

 

[kapnD]

with 24 passengers aboard, I’d be concerned about the potential stability impacts of passenger’s movements.
Fixed seating would probably control weight distribution better than plastic chairs.

 

[BlueBell]

You've got about 6 000 pounds usable buoyancy leaving ~12 000 pounds reserve buoyancy with round pontoons.
If you were to square up the cross section of the pontoons you'd be looking at ~7 500 and ~15 000 pounds respectively.
These are conservative numbers as I am using a 1/3 load : 2/3 reserve buoyancy ratio and tapered bow and stern.

How confident are you in your weight estimate?

Can you really trailer up to 12' beam in Ontario?
No wonder your roads are in such bad shape.

 

[philSweet]

The weight estimates don't make any sense to me, so please provide the weight calculations. For instance, when I looked at this a couple years ago, I figured I needed about 100 pounds of battery system weight per passenger, plus whatever the boat hull needed empty. So a passenger had a weight profile of 250 pounds for the person, 25 pounds of carry on, 100 pounds of battery system, and about 20 pounds of supplies such as water, snacks, first aid kits, lifejackets, etc. Call it 400 pounds per person. At 24 people, that's 9600 hundred pounds payload. The bare boat in trailer mode will need to have about 25% weight premium of batteries, generator, solar, BMS, and electronics cooling systems - stuff you can't easily offload onto the truck for trailering. I'm guessing I could build a 35 foot hull at 7,000 pounds. Add 25% - 9750 pounds. Launch weight would be about 2000# more after you put the thing together at the ramp. This puts the loaded weight a touch under 20,000 pounds. Keep in mind there are a lot of American tourist couples who weigh over 1000 pounds. I've loaded them into canoes and Kayaks in the everglades and the Florida Keys.

I like that you have worked with the Skoota and made a go of it. I strongly suggest you continue to work with well developed designs. I suggest your next step should be a 28' version and get some experience with that. A 35'er should be about 16' beam, and would need to be broken in half to be transported. I designed one for a friend about 30 years ago that could be folded in half for transport, but it would take about 10 hours to do that. He was okay with that. It could be stuffed into a 40' ISO container for hurricanes.

And then there's this - Inquiry looks at boat design https://www.baltimoresun.com/maryland/bal-te.md.safety09mar09-story.html

 

[patrickza]

I'm curious about your electric setup of the boats you already built? How much power does your solar bring in? I have a 30 foot electric Catalac catamaran with 3200W of solar, and I can also cruise pretty much indefinitely at 4.5 knows in good sun. I'm using two 6kW ePropulsion outboards.