T-Pain Is On A Boat: Re: [Electric Boats] electric prop and re-charging

Tom,

Good luck with your dream - it is surely doable.

Some additional thoughts:

You might a consider a Torqeedo electric outboard which could be tipped up to operate in very shallow water. They seem expensive but are not any more money that buying all the separate parts you need for a custom inboard installation and surely are orders of magnitude easier to install. I'm told the newest Cruise models are much quieter than the smaller 401 and 801 sizes.

Efficiency is critical with electric power because you can carry only a tiny amount energy in the battery bank so you need to make every electron count. I don't really know if an Atkin tunnel stern design would be less efficient than a conventional smooth bottomed round chine hull but I have my doubts. They were designed before reliable outboards existed and I expect the tip-upable outboard was a better solution to running in shallow water. Getting the prop out of the water for sailing would be a plus too. OBs are great in so many ways, if only they weren't so damned ugly...

Have you looked at any sharpie designs, like Munroe's Egret? They were made to sail in very shallow water and have some capability of coast wise passage making. With a smaller, easier to stow unstayed rig (how about a standing lug?) and a removable leeboard they could fit your design brief quite well. Phil Bolger and Jim Michalik have many sharpie plans for sale. You just need to find on designed for ballast so if will float on its lines with the battery bank.

And how about a kite for a down wind sail? You want something compact to stow and don't need upwind sailing or maneuvering ability. I've never tired one but they are rapidly developing for the sport of kite-boarding. Seems like they must be generating a significant amount of power to get a water skier going that fast so ought to be able to tug a 25' boat along at 3-4 kts.

You will be surprised how little power is required to drive an efficient hull up to an S/L ratio of 0.8 to 1.0.

Denny

----- Original Message -----

From: thomashjohnsonjr

To: electricboats@yahoogroups.com

Sent: Monday, November 16, 2009 12:11 AM

Subject: Re: [Electric Boats] electric prop and re-charging

Mr. Wolfe:

Thanks so much for taking the time to reply and encourage.

Referring to 1) & 2) of your post- for

1) acceptance of slow speed - that is my intent.
Canoeing, kayaking speed is 3 to 5 miles an hour if one really pushes the paddling.
2) re-charging from shore power would be the preferred re-charge method.

A range of 100 to 140 miles - electric only - would enable crossing to the Bahamas during good weather.

Sails would/could certanily extend the range for poking around. A gaff rig is exactly what I've considered - or a crab claw set up, except there seems to be little information on 'off the shelf' crab claw rigs, if any even exist.

A Honda generator seems to be the path of least resistance for re-charging in isolated areas. Proper grounding, safety, fuel storage AND determining how to operate the generator during terrible weather would HAVE to be part of the basic design.

The boat on your web-site resembles some of the Atkins designs above water. Your craftsmanship appears to be of quite high standards. Thanks so much for posting the link to your web site.

I've cut many a groove in oyster beds and have had to wait for the incoming tide while stuck on mud-flats. Having a sea-worthy boat with a shallow draft (besides electric power) would be a dream come true. The attraction for the tunnel stern Atkins design(s) is the protected prop, and being able to beach on rollers if necessary. A winch or come-along would work wonders for such.

I will most likely use a combination of marine ply-wood and wood stripping for the hull and decks.

Thanks to all for everyone's responses. I went to St. Simons Island this weekend for a meeting, but took a break to inspect the boats at two different marinas.

Again thanks,

Tom H. Johnson, Jr.
Pine Mountain, Georgia

--- In electricboats@yahoogroups.com, "dennis wolfe" <dwolfe@...> wrote:
>
> Tom,
>
> I don't think your requirements are too 'out there'. Seems to me there are just a few constraints on your project. 1) You must be willing to accept slow speed and maybe even no speed (i.e. don't go) when adverse wind or current conditions occur. 2) Recharging from shore power must be convenient because that's the energy source that's cheap and quiet. All the other options, when sized to be practical for every-day use are either very expensive or bring with them the downsides of ICE power. Plus most of them would work better driving the prop directly instead of the daisy chain of prime mover to generator to battery to motor to prop.
>
> I could see a long narrow light hull ( a catamaran would be even better) optimized for a speed/length ratio of perhaps 0.6. A boat with a 30' waterline length, weighing 3000# with (16) 220ah 6v batteries could go 140 miles at 4 mph.(11 amps at 48v) 100 amps would give 8 mph for 22 miles. Total battery weight would be about 1000# and cost maybe $3500 for top of the line AGMs. Maybe 1/3 that for wet batteries. You could cut the bank size in half in you were happy with less E range or more reliance on a gen set.
>
> A 2kw quiet generator like Honda EU2000 ($900, 50#) hooked to a 1.5 kw battery charger would drive the boat about 5 mph with no battery drain. You'd want the generator out in the open for cooling and gasoline safety. They are not marine rated and not safe in an enclosed area. They are very quiet though, I'd say as quiet as a little four stroke outboard. It could recharge your 80% depleted bank in about 15 hours.
>
> You stated you don't want a 'regular' sailboat with aux E power. Just about anything will sail down wind, though, and that's what I'd set up, making the rig easy to strike when not sailing. A 150 sq ft balance lug rig would have spars short and light enough to be taken down and stowed without any mechanical advantage (build them hollow) and would perform well off the wind. You don't want any foils sailing down wind and a simple lee board would give you a modest reaching ability.
>
> Denny Wolfe
> www.wolfEboats.com
>
> PS: I envy you the time spent with Robb White. I was a great fan of his and had hoped to make it to one of his speaking engagements one day.
>
>
> ----- Original Message -----
> From: thomashjohnsonjr
> To: electricboats@yahoogroups.com
> Sent: Thursday, November 12, 2009 12:08 AM
> Subject: Re: [Electric Boats] electric prop and re-charging
>
>
>
> Thanks, I'm no authority on the White family, just happened to visit 'the T'ville boat shop' just before the time everyone was hooked up to the internet or before I knew Robb White wrote for Wooden Boat and other. But he seemed quite happy that I liked pokin' around on the water, and knew many of the same watery places in which one can poke. I hope some of the water oriented Whites will continue to 'slap'em together', their collective good workshop, boating & plain ole pokin' around example has enabled lots of people to begin playing with materials and designs - and combine old methods with new materials.
>
> So, . . . back to electric boating and extended travel with electric.
>
> An extended travel electric boat with the ELECTRIC wagging the dog's tail, not a sail-boat with small/minor electric power is what I'd like to construct, and have the workshop space and time in which to do so.
>
> Lee-board(s) could be added to the tunnel-stern designs sail to increase the range. Sails would be in proportion to the size of the craft as with canoe or kayak sails to those boats.
>
> Each 'easy off the shelf' change of state seems to be expensive :
>
> solar to electricity,
> internal combustion to electricity,
> water/prop re-charge to electricity,
> wind to electricity (docked),
> or stationary bike to electicity,
> and so on.
>
> And electric storage is quite expensive for the amount of total mileage/life of the battery bank/storage, though as one of the links pointed out above that the slower one can travel, the more mileage comes from a battery charge, and I suppose that also means a bank of batteries could ultimately pack in double or triple the miles or more than storage banks that were quickly dis-charged.
>
> I'll continue to read the links and posts, thanks for continuing to consider and respond to this thread.
>
> Tom Johnson
> Pine Mountain, Georgia
>