Electric Launch Design optimized for semi-displacement speeds

VGYD has a great aesthetic.

At hull speed, drags at ~ 18-25/lbs? The Torqeedo Travel max thrust in pounds is ~ 68 lbs, so with those kind of numbers, our Torqeedo Travel at ~ 1/3 rd throttle would be good for a couple of hours at 3-4 knots. Take two batteries! (Half assed guess based on experience with our Torqeedo Travel)

Rowing with the Torqeedo Travel at 1/4 -1/3 throttle might assist things more than you’d think- pedal/prop unit too.

Think about it more as an electric bike rather than a motorcycle.

 

I see Van Oossanen & Associates are the patent holders on HullVane: Hull Vane for Efficiency - Professional BoatBuilder Magazine https://www.proboat.com/2015/03/hull-vane-for-efficiency/

 

Two electric launches in professional boatbuilder, both built in The Netherlands.
Self explanatory: Tideman Boats Launches Electric HDPE Patrol Boat - Professional BoatBuilder Magazine https://www.proboat.com/2020/06/electric-hdpe-patrol-boat/
April/May 2024 issue, photo page 50, a Werffboat by Sheepstimmerwerft De Hoop:
https://digital.emagazines.com/prof...erdtp_professional_boatbuilder_1_net_paid#p50

 

This launch, from Moonday Yachts in Turkey, is notably similar to my thinking in its hull shape.
According to a late 2019 post on the company's Facebook page, hull #1 was destined for the United States.



Other news: Yamaha acquires Torqeedo. Pure to use Tesla charger.

 

Interesting stern of Luna Rossa Prada Pirelli. https://www.americascup.com/original/m18649_240413_LRPP_AC75_B3_D0_089-2.jpg

 

Stephen Ditmore
We are still missing a proper SOR from you.
Therefore, you will not receive an adequate response to your posts.
It is only when you have performed an SOR that we can sketch a hull with decent performance that can then be developed further.
JS

 

Electric Launch Design optimized for semi-displacement speeds

Statement of Requirements

Intent: A multi-purpose electric launch, comparable in utility to an Oldport 26.

Purpose: Support for a yacht club or marina that emphasizes sailing and where most boats are kept on moorings in the northern summer season. It will be expected to serve as a committee boat, photographer’s boat, instructor/coach and tow boat for the youth & dinghy programs with the ability to run errands on the other side of a bay and to occasionally make a short transit across unprotected ocean. The yacht club has slips available with shore-power hookups; Tesla-style chargers could be adapted. The club does NOT have a conventional fuel dock.

In the winter season the boat might be taken aboard a megayacht or cruise ship headed for the Caribbean to transport people ship-to-shore. The ship or megayacht utilizes an alternative fuel and deliberately does not carry conventional gasoline or diesel. Using the alternative fuel it has significant on-board electric generating capacity.

Length limit: 26 foot (7.925 m) waterline

Capacity: Utilizing the USCG (CFR §178.330) criterion for unprotected waters, the design must be rated to carry 7 persons (6 persons plus the operator). It may be rated for a greater number of passengers, and the higher partially protected waters capacity may be used in transportation efficiency analysis for comparison.

Intended top speed with two people of combined weight 380 lbs (172 kg): 15.3 knots (28.3 kph, 7.87 m/s)
Intended top speed, full load (each person 190 lbs (86 kg): 13.6 knots (25.2kph, 7.00 m/s)
Intended cruise speed: 11.9 knots (22.0 kph, 6.12 m/s)

Proposed power: Pure Watercraft 50HP Electric outboard system – single

Alternative power suggestion: Torqeedo Cruise 10.0 or 12.0 outboards – twin (contra-rotating props would be ideal)

Proposed battery & power system: TBD. Note that Pure builds a pontoon-boat style catamaran with single or twin 50HP outboards. That boat shares a battery and power system with the Chevy Bolt EV with the following specs:

• 12V auxiliary power up to 10A for on-board electronics
• 65 kWh automotive battery pack from GM®
• Integrated level I & II Charger supporting 120V-240V charging.
• Support for DC Fast Charging

Range: I want to be able to go 6 hours at 11.9 knots (22.0 kph, 6.12 m/s), at full load displacement. Is that too much to ask? That's 71.4 nautical miles. [Modified slightly by a later comment, post #84.]

Scratch boat:
As a design starting point I’ll suggest taking the Uffa Fox design Ankle Deep:
Ankle Deep http://www.uffafox.com/ankledp.htm
And scaling it up slightly to match the 26 foot waterline length of the Atkin designed Spermaceti:
Atkin & Co. - Spermaceti https://atkin.mysticseaport.org/Cruisers/Spermaceti.html

I like the idea of a launch having a foam collar. Two companies in the Pacific Northwest make metal boats with foam collars, SAFE boats and Life Proof Boats. In Scotland, Ultimate Boats makes composite ones using a thermoplastic resin (I wrote an article here). Whatever form the collar, fendering or rub rail takes I’d like for it to continue aft a little, or for the motor(s) to come forward a little. This is doubly true if there’s any sort of Hull Vane or Hydro-Fin; I want it to be protected from the side. Also, I’d like for the aft quarter to be rounded, tucking in a little so in pulling away from a moored boat the launch operator can work the bow away from the boat by thrusting the outboard toward the boat.

Before going composite, though, I’m thinking the first boat will be in some form of cold molded wood construction, like the van der Werff, or plywood, like the Clara 8m.

 

Aahh..the beauty of a cut and paste SOR

Ok, so based upon your numbers, she would have a Fn of 0.9..this is post hump speed. Not technically planning, but well into the semi-range.

Looking at similar size and hull shape vessels this yields a power requirements of circa 35 hp/ton, for said speed.

So given your 50Hp outboard, your vessel needs to weight a max of 1.43 tonne….call it 1.5 tonnes for Jazz!

The question is then, can you build a monohull that satisfies your SOR with a total all up full load of 1.5 tonne?

 

1.43 tonnes puts displacement between the Oldport and the Clara. Yes, the value I gave for top speed with two people is intentionally lFn=0.9. The value I gave for full load top speed is lFn=0.8, and for cruise speed lFn=0.7.

I see above I made a reference to cruise speed being lFn=0.6 @ half load in my earlier post. We could use lFn=0.6 @ half load in thinking about range. I'd still like 70 nautical miles if that's achievable; if it has to take more than 6 hours, so be it.

 

Question: how is passenger capacity established in Europe? The Oldport claims a passenger capacity of 18 while the Moonday 850, which is larger, only claims 8. Something is amiss.

I do not wish to suggest that I am averse to inboards. I'm not; I think an inboard arrangement is worth considering. The Oldport, the Spermaceti and the van der Werff, are examples of inboard designs I've cited. A topic I'd be interested in is the applicability of a self-pitching AutoProp or other variable pitch technology to this application. If a fixed pitch prop makes more sense, the Sharrow Marine propeller interests me.

While I showed a jet drive on my sketches years ago, I think the project of attempting to optimize a jet drive for the speeds we're talking about complicates this exercise too much.

 

Here's the sketch where I showed a jet drive. I can't now locate the CAD file. This image file is dated 2011, but I think the sketch is even older.

Except that I think I should put the jet drive aside, my thinking hasn't changed much in the years since.
Here's my more recent sketch (again):