Electric Leisure Boat Design II

Back to the 'design': several users have modified a paddle boat or peddle boat with an electric motor, and here are the links. There watersports people have some paddelboat hulls lying around so that should take care of the hull. With a little modification it could be made into a small electric speedboat.

How to put a motor on a paddle boat

Paddle Boat With Motor - with electric and outboard motor attached

One of the conversions lists the parts - trolling motor and battery, comes to under $200. I would add a deck and a steering wheel and linkage, that will be in the next few design drawings. Also, it should be beachable without damaging propeller, maybe with some skids or wheels underneath. Maybe the bow needs to be changed a bit or re-shaped. The general layout is shown, a pod type motor between the twin hulls may work.

 

This company has come up with an electric boat, placing the motor in between the twin hulls and out of harms way, just as I suggested. Now all it needs is a steering wheel attached to the central tiller, that could be done simply, a dashboard, windscreen and a clock, gps unit and voltmeter.

I know have to work out the speed, and range under different mission profiles. Let's take a lake 1 mile in length, then if there is enough power to cruise for 1 hour, that means a cruising at 4 knots for 15 minutes to the other end of the lake, loitering for maybe one hour at slow speeds, and heading back at full speed in another 15 minutes, with 15 minutes reserve. There should be a spare battery that can be switched to manually in case of an emergency. A nice boat simulator would help.

Here are some more illustrations with rudder, motor position and overall layout. I moved the seats backwards to correspond to the more rearward positions of the seats in the actual pedal boat.

No doubt other cosmetic improvements could be made.

 

Your proportions are way off if you are looking to cruise efficiently at 4 knots. Less than 2M hull length implies an efficient displacement speed under 2.5 knots.
The SunDolphin electric is based on cheap adaptation of existing pedal boat to add a trolling motor. The only significant number it offers is price.

 

There is a better boat, the pedal boat used to cross the channel. The Nauticraft. The hull shape is more traditional, although the standard pedal boat is a twin hull, which may mean that the hull speed may be higher?

English Channel Crossing Pedal boat | Nauticraft - Pedal & Electric Boats https://www.nauticraft.com/tag/english-channel-crossing-pedal-boat/

There is an electric version also.

For the normal electrified paddle boat, assuming a speed of 2.5 knots and a distance of 1 nautical mile, this means it will take 1 hour to go up and down with possibly some reserve with another battery.

The lakes or lagoons I am looking at are here at the beach in Huluhumale, Maldives, 1 km or 0.5 nm, Bolgoda Lake and Lake Gregory in Sri Lanka that are about 3km or 1.5 nm and again about 1.3 km or again about half a nautical mile in length. Given the fact that pedal boats are used on the lake Gregory (see picture taken from linked page), an electric boat with an endurance of 1 hour at 2 knots continuous running could be workable.

Some links:

Lake Gregory, Sri Lanka.

Another article with pictures. Scroll down to item 2.

"Tourists can hire small boats, and go boating across the lake, or whizz across the lake in a speed boat."

I have been there and to the lovely park but hesitated to venture into watersports as it is cold (relatively for me) out there.

Bolgoda Lake, Sri Lanka (Trip Advisor)

This design is for a basically electrifying a pedal craft, and an existing water sports unit could either buy new or retrofit the pedal boats they already have to an electric version for about $200. An operator will be able to rent electric boats out for much less, and they have their attraction, less noise, less pollution, hopefully these will be introduced soon.

 

The hull of the Sneakeasy, if I'm not mistaken, is VERY simple, though I suppose the arched deck could be annoying. But you don't NEED the latter.

 

I had a look at the Sneakeasy plans. Flat bottom, yes, simple design. Only thing is it is 26 ft long. I get what you are saying though, modify a paddle boat and then... can this thing go any faster? 2 knots? So I see the need for a long hull in order to reduce drag.

According to the hull speed formula, 1.34 x Sqrt(26) is equal to 6.8 knots compare to the 4.2 knots for a 10 ft boat.
No a bad result for just lengthening the hull. The article says that:

She's one of the series of Bolger "power sharpies", the original of which (Tennessee) was closely related to Albert Hickman's "Viper" of 1910. The original Viper attained 18 knots from her 12 hp engine, a truly remarkable feat especially for that time. Sneakeasy is designed for 7.5 to 20 hp.

A Bolger Sneakeasy Homepage http://boats.backwater.org/Sneakeasy/Sneakeasy.htm

 

Out in the Kayak again I managed 1 knot, as registered on my speedometer app on my phone. 3 knots or more will be fine for my purposes, for the moment. It is a leisure boat after all.

 

The Sneakeasy has such a light displacement for its length, that the conventional hull speed isn't really a barrier. Anyone who's sailed a Hobie Cat in a reasonable amount of wind has seen it greatly exceed the conventional "hull speed". If you look at a Hobie 14, the waterline length might be 13 feet if it's got one hull flying. That gives a "hull speed" of 4.8 knots. The D/L ratio on one hull, in Imperial units, is around 90, or about 3 times that of the Sneakeasy! (Sneakeasy displacement on one drawing given as 1,300 lbs, waterline length same as 26.5 foot OAL). But the Hobie can go a lot faster than that, without making much of a wake.

The Hobie's ride is remarkably smooth in small waves, even at fairly high speeds. That's due, in part, I think, to the v-shaped hull, which it needs to go upwind without daggerboards. That v-shaped hull also means more wetted surface.

So a Sneakeasy can almost certainly go much faster than 6.8 knots without a sudden, steep rise in resistance. This doesn't mean it won't gobble up more power than, say, your 10 foot pontoon boat doing 3 knots, but I bet that if both were at 4.2 knots, the Sneakeasy ought to be using less power. Just a guess, though. The Sneakeasy, though, is completely comfortable with 4 people on board. I'd guess 6, based on being on one with 4. A disadvantage of the Sneakeasy is that it has more wetted surface than a more rounded shape, but it's also very stable. I don't know if it has more wetted area than a catamaran with a more sophisticated hull shape. The Sneakeasy bumps quite a bit in small waves, and there's some noise as the waves slap the hull. You'd expect with any flat bottomed hull. However, this is based on a ride using most of 10hp, so it may not be relevant, and almost any powerboat user will be used to it. Anyway, I think, for two people, you could shorten it quite a bit and still go a lot faster than the 10 footer.
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I'd left this message in draft form and forgot to send it. For three knots, a good rowboat might be very suitable. A classic Whitehall would do a good job, though I'm sure there are simpler shapes that would work. 15 feet would probably be long enough for reasonable efficiency, depending on just how much load was carried. I've rowed a similar, 14 foot boat fairly easily, with 5 adults on board. The speed depends a whole lot on the wind and somewhat on waves, though. A classic peapod would also be a good shape, I think. If a lot of boats were to be produced, a fancy shape might actually be cheaper to make than a flat sided one. A pontoon boat would work ok as well, IF the pontoons were shaped like kayaks or something else relatively narrow and low drag.

Some of those Nauticraft boats seem to have suitable shapes, and there's even at least one electric model that could meet your task pretty well, unless you wanted to go into really shallow water. The model I looked at required about half a meter of water, due to what appear to be a permanently installed rudder and propeller. Something similar, but with a trolling motor, could pull up the motor when necessary, and if it hit something, it might pivot up the way outboards do. In a rental environment, it might be very convenient to remove and replace a trolling motor after some idiot figured out how to damage it.

Lines drawing of a Whitehall type:
http://4.bp.blogspot.com/-LOZ0d1r9pa0/Urm3S78CsNI/AAAAAAAAcQM/zqW0gn-lRp4/s1600/Whitehall.jpg
Lines of a peapod:
https://store.mysticseaport.org/med...25d08d6e5fb8d27136e95/w/s/wsp_129_12-comp.jpg
These are not completely optimized, but boats with similar shapes move along nicely with low power. Probably significantly less power than a hull shaped like a Sneakeasy's. If you want to get up to 4 or 5 knots at a 15 foot length, you'd probably need something else.

 

"rnlock" is that yourself sailing the catamaran Hobie Cat? That looks fast, as fast as the ferry I have been on, and fascinating. I am re-reading your post again and again trying to get the all the information in there.

As for the design, I have started to look at portability - without a trailer, a catamaran might have a big advantage in having smaller hull volume overall. Better to look at a proven plan and adapt that I think.

This 'portable double canoe' catamaran is supposed to go quite fast for the power. Will post link when I find it.

The problem is I want my boat to look like a speedboat with proper seats, steering wheel and a windscreen. I am not sure if that violates any design rules but there you go.

 

Could this 6ft dinghy be the basis for a leisure boat? No one wants to rent it out though. Could it be turned into the yellow jet boat?

 

Power

Let's talk about power for a small 5 ft boat. One of those small outboard motors are fairly inexpensive:

Minn Kota Pontoon Freshwater Hand-Steer Bow-Mount Trolling Motor with Latch & Door Bracket, 52" Shaft
on Amazon $ 250 (24 Volt)

Batteries: ? Preferably Lead Acid.

 

Some random thoughts:

If high capacity battery costs go down as much as General Motors claims they will over the next few years (look up Ultium batteries), electric leisure craft might increasingly make good sense. Add together the reduced motor maintenance, and the quieter power, an electric motor can give, and I think they might be nice. Look how much improved battery technology has already made electric scooters, and ebikes, more popular. One could also imagine renting an e-boat as easily as an electric scooter, with your smartphone app; no customer service rep need be present to handle the check-out. The customer returns the boat to the charging stand. No one needs to play with gasoline. The app can also check whether the battery has enough charge, and warns the renter when the battery is getting low, as well as whether the business is reaching closing time, when rescues become unavailable. And after the customer leaves, the app occasionally invites the customer to come again, or offers special deals.

Boats will never be completely safe. It might be cool if when the boat tips, it sends out a radio signal to the operator, so they can come help. But that adds cost.

For reduced rental operator intervention, there are some advantages to self-bailing boats (that have lots of flotation + drain holes, like a surf ski), though I'm not sure if that is worth the cost.

I think there is often a trade-off between hull shape efficiency and the number of rescues the rental operator needs to give. E.g., the most efficient boat shapes are often tippy. For the rec market, efficiency isn't the biggest issue.

BTW - decked kayaks can scare claustrophobic novices, and can be a safety hazard - newbies can get trapped underwater if they don't stay calm enough to figure out how to exit. Though some people do rent kayaks.

BTW, on a completely different tack, I've never understood why transparent boats aren't more popular. Could a nice rental boat be transparent too?

Should some of the rental fleet have a fishing rod holders, in case the customer wants to fish?

And don't forget that many good rental fleets should have more than e-boats. Some people want to paddle or row or sail, for a bit of exercise.

 

Years ago I was dreaming about building a completely transparent sailboat. Hull, free standing mast, sails, all transparent.

Recently I found you can rent transparent kayaks all over the world. Google: rent transparent kayak and you'll get a lot of results.

As it turns out they are rather cheap at Alibaba:

Enjoyable Clear Kayak With Transparent Bottom - Alibaba.com https://alibaba.com/showroom/clear-kayak.html

 

Here is a video for some inspiration....

 

These guys are building (have built?) a little jet drive speedboat with the intent of putting a 100 hp petrol engine in it. They had the hull constructed to specification, and tested it with — of all things — an electric drill. I was a bit shocked to see how fast it went.



BTW, your original inquiry asked a lot about why renting boats costs so much relative to renting cars, and delved into ideas of how to build a business renting boats more cheaply, seemingly driven by your desire to rent a boat cheaply. There are several business drivers you’re not taking into account, such as depreciation (those used boats you’re looking at are cheap for a reason), cost of operations (including liability insurance, employees, rent for your facility, taxes, etc.), and the desire to make a profit. Seasonality is a big factor in recreational rental businesses, even in tropical locations that aren’t as affected by seasons as northern or southern climes.

But I digress. I, too, have a desire to design a small electric runabout. I came here to ask advice on a design I’ve sketched, and found this thread, which has been instructive. I’ll post another thread so as not to hijack yours, but I think we’re of a similar mind.

Cheers.

JD