Any available 40'-45' low power hulls?

[Quietboats]

Hello,
Does anyone know of any currently available 40'-45' shallow draft (28" max) displacement hulls designed for low power consumption. I am assuming that a prop tunnel would be needed to meet the draft requirement. Other parameters are:

• Approx. 10,000 lb passenger and gear load.
• Top speed of 8-9 knots.
• Max 24 HP diesel power.
• For use in relatively sheltered waters.
• Aluminum or fiberglass preferred.

Any help will be greatly appreciated. Thanks, Tom

[Ilan Voyager]

This kind of boats is not common, so I think you won't find a lot of plans on internet.

For the payload you have given and making some wild guesses about boat weight and shape (draft requisite) 24 HP is not enough for getting 8-9 knots top speed. Tunnel propellers are costly in horses and you'll need also extra power in case of wind, currents etc. A part the power requirement, there is nothing impossible and any naval architect knowing well displacement boats will make plans for a reasonnable fee.

For low consumption, think about a multihull, cat or tri. They can be terribly efficient at low speed with their slim hulls.

[tom28571]

10,000 lbs is pretty light for a 45' boat so it is likely to be both narrow and shallow. 28" is more than you will need and the beam is likey to be no more than the road legal 8'6". Depth will be determined by the propeller and skeg. If carefully designed for displacement speed of 8 to 9kts, I suspect that a 24hp diesel could well be adequate.

There is a 39' Mark Van flat bottom cruiser similar to what you suggest sitting at my dock right now. I have seen 10kts with a 50hp outboard on this boat. http://bradsboat.tripod.com/

With a more efficient bottom and a more torquey (at cruising speed) diesel, your goal may be in reach.

[Quietboats]

Thanks for the input, the link to Brads boat is inspiring and helpful. A few more details on the project: we have been asked to come up with 4-5 boats to be used as eco-tour boats for 25 passengers. One requirement is that the boats be able to run for 5 hours on electric power alone (in sensitive areas) and the balance of the trip using diesel--the 28 hp listed reflected what I thought would be the maximum feasible using electric--so a larger diesel motor could certainly be utilized. Still, the hull will need to be designed for maximum efficiency. Also, the 10,000 lb figure represented the planned passenger, gear and battery weight, and didn't include the weight of the boat itself.
I realize that this is a unique application, but I was hoping for the off chance on coming across an existing commercially available hull to build upon in order to keep production and development time down--perhaps some obscure commercial fishing vessel designed for shallow waters. Thanks again for the advice and interest, Tom

[CDBarry]

Try the NPL series.

[PAR]

Try looking at Parker Marine's sharpie designs.

[Ilan Voyager]

I've made some fast calculations.

For a 13 meters boat, very shallow V (almost flat) total displacement (boat and payload) 7 metric tons (a realistic weight considering a common construction), classic transmission:

10 knots 50 HP
8 knots 33 HP
6 knots 18 HP
4 knots 8 HP
2 knots 2 HP

With 24 HP you'll get 6.8 knots. Also you'll need some extra power in adverse conditions, and not to use always the engine at max power or it won't last. A good rule of thumb is in commercial use to keep a diesel at 80-85 % of its max power. If you want 8 knots every day you'll need 33/0.85= 38 to 40 HP.

A 5 hours autonomy using electric power is a challenge, and very expensive if you want to keep a 8 knots cruising speed. Efficiency of batteries is low and I guess the batteries will be charged during the night.

You may consider an hybrid diesel electric (that simplifies the transmission) with a bank of batteries (very heavy stuff) able to power the boat while the diesel is shut off during at least 5 hours plus a security margin.

My level of knowledge about electric boats is very low, so I won't say more, you need the help of a specialist. That I'm sure that a such system will be very expensive.

Is the electric power a mandatory requirement of the local authorities? You can use very low emission engines, with efficient mufflers and insonorisation at better price.

You'll need a hull optimized for your requirements, but it's the simplest part of your project.

Just some computations.
You need 28hp, so 20kWatt.

Guess a 48 volt power supply. That translate to 400 A under 48 V.

To produce 400A during 5 hours, you will need 2000A/h of battery capacity.

Assume high perf automotive lead battery. You will have roughly 100A/h under 12 V with one, for 70 lbs. You will 20 (for Amp) * 4 (for Volts). SO 80 * 70 lbs = 5600 lbs for batteries alone.

And another joke. You will have to charge your batteries. Where does the charging energy comes from ? a genset ? In terms of pollution, you have done nothing, just displaced the problem. You will have more smokes from the genset than from a engine in the boat, because the process of charging batteries and driving an electric motor with them is far from having an efficiency of 1. (say 70% for charge/recovery and 90% for mechanical power generation).

Best way is to use an ultra low emission diesel engine. VW car manufacturer have made a 80 mpg car (LUPO 3L) With such a 3 Cylinder engine, 70 cid, turbo diesel, electronic direct injection , catalityc converter, with particles filter, and super critical muffler, perhaps you will be able to reach your requirements.

BTW, if a boat with 5600 lbs of batteries sank, what would be the environmental consequences ?

fcfc.

[Ilan Voyager]

Originally Posted by fcfc

Just some computations.
You need 28hp, so 20kWatt.

Guess a 48 volt power supply. That translate to 400 A under 48 V.

To produce 400A during 5 hours, you will need 2000A/h of battery capacity.

Assume high perf automotive lead battery. You will have roughly 100A/h under 12 V with one, for 70 lbs. You will 20 (for Amp) * 4 (for Volts). SO 80 * 70 lbs = 5600 lbs for batteries alone.

And another joke. You will have to charge your batteries. Where does the charging energy comes from ? a genset ? In terms of pollution, you have done nothing, just displaced the problem. You will have more smokes from the genset than from a engine in the boat, because the process of charging batteries and driving an electric motor with them is far from having an efficiency of 1. (say 70% for charge/recovery and 90% for mechanical power generation).

Best way is to use an ultra low emission diesel engine. VW car manufacturer have made a 80 mpg car (LUPO 3L) With such a 3 Cylinder engine, 70 cid, turbo diesel, electronic direct injection , catalityc converter, with particles filter, and super critical muffler, perhaps you will be able to reach your requirements.

BTW, if a boat with 5600 lbs of batteries sank, what would be the environmental consequences ?

fcfc.

fcfc (do you remember the dynacam engine thread and the 300 HP page for monkeys?) I totally agree with you.

I'll add that automotive lead batteries can be discharged of only 20-25 % of their capacity, and special deep cycle batteries until 50 %. The life of lead batteries is short.

NiCad batts are very expensive, and to have a few hundred kilogs of toxic heavy metals is a true concern.

Last issue: cost. I doubt of the rentability of a tour boat using electric technology. See the electric cars...a lot of blabla, nothing real on the market.

Hybrid low emissions diesel-electric will work without the batteries (electric autonomy) requirement. But it's a useless complication on a small boat, compared to an ultra low emisions diesel. Most of the new european diesel car engines would be good basis to start.

[Ilan Voyager]

Diesel engines by VW http://www.volkswagenmarine.com/index_e.htm.

These engines comply with the highest european standards about emissions. Have a wide range until 150 HP.

[Tall Timber]

How bout refurbishing a surplus navy launch with a power take off to a generator? might want to slow a bit while running on batteries. Maybe tear off the power head off an outboard and replace it with an electric motor for running off batteries.