Electric Boat Marathon Question

[Mark 72@E]

I think my jaw dropped when I read about Mike Bontoft's 98+ MPH record in a 144 Volt Hydro at the Devil's Lake Kilos. I had no idea that speed like that was possible under electric power.

Let me ask my question first before you begin reading the details below. Would it be feasible for a >>planing<< hull, race boat or not, to carry the necessary battery power to last 24 miles at a speed just fast enough to keep the boat on plane?

In this month's PropTalk Magazine which is about powerboating on the Chesapeake Bay and occasionally covers local inboard boat races, I learned about the Wye Island Marathon. This electric boat race is run annually to "foster fun and invention in electric boat propulsion and design". Slow boats are encouraged because, according to www.electricboatmarathon.org, "in order to go the entire 24 miles, the boats, by necessity, must go fairly slowly".

Or do they? Current entries include canoes, skiffs and other very long non-planing hulls. The fastest record for any class is 3 hours. 6 minutes, 30 seconds for a blistering 7.66 average MPH over the 23.82 mile course. There is a mandatory 10 minute coffee break about halfway through the race (I'm not making this up). So there would have to be enough energy left in the batteries to get the boat up on plane a second time.

It seems to me that if you could plane a hull and sustain it at just 12 to 15 MPH you would not only shatter the existing Wye Island Marathon record, you would shatter expectations of electric power just like Mike Bontoft did with his new record.

You can read the article now about this year's race and see pictures of entries from this year by going to www.proptalk.com. Click on the December 2008 magazine cover and go to page 31.

Your thoughts?

[sam]

Mark, there is a Hybrid class ... I'm sure a hybrid could be devised that stayed on plane and won even if a full battery electric only could not make it.

[Bill Huson]

Say what ???

I mean WATTS . . . as in a boatload of watts. Rough conversion, 746 watts = 1 horsepower. With only 4 hours sleep last night my tiny brain is too muddled to devise formula for a high speed endurance electric craft, but I'm guessing it isn't practical until some geek invents a superlight battery.

Numbers in my head: My 18' Starcraft weighs about 1500 lbs. with a full fuel tank and me on board. 115 hp = 85,790 watts. She planes easy and will run close to 50 mph. My 23' Parker weighs about 5,000 lbs. and romps over the waves at 40+ mph with 250 hp = 186,500 watts. Rough guess the Starcraft would get on plane with 25 hp = 18,650 watts. BUT - add enough batteries to punch out 19K watts for enough time to run a marathon and there goes your svelte 1500 lbs. displacement. More tonnage = equals more wattage to push the boat on plane.

I have not figured out how many pounds per square foot of planing surface my boats have, but I'm sure an increase in planing surface would support more weight at the cost of increased drag. The project might work with a BIG flat bottom (skiff style) boat of ultralight composite construction. Since you mentioned canoes I assume the race is on calm water.

And I course I'm thinking Green Electric? Maybe not. Boats crash and sink. I'll bet fish and sea veggies just love a sulfuric acid bath, not to mention several hundred pounds of lead.

[Geezeracer]

About 16 years ago the electric utility I worked for sponsored a variety of E-boat events to promote rec sites we had to build in exchange for a FERC permit to raise dam height for a power project. I was appointed "den-mother" to make it work. For about three years the utility ran electric only kilos and circuit races plus battery and solar marathons.

Utility kilos only ran twice. After the second Kilo I retired and took the E-kilo players to APBA as a special event. The utility wanted to break the 50 mph record then held by a UK boat but running only once a year that wasn't likely. Running SE all were scrabbling to avoid being last and it only took five races for competition to present a record breaker in Norm Boddy's 55 mph DiSilva runabout. At the end of the first season we'd learned that you could trap enough air to fly a battery pack, and a year later the record was pushed to 70.5, where it stayed until Mike turned his 98.8 in October.

On the Marathon side prize money ($5,000) drove the competition pretty hard. The battery marathon boats were allowed 125 pounds of lead/acid batteries (three automotive) and the initial event was 12 hours...Winner being the boat going the furthest distance. Almost all carried two batteries aboard and rotated the spare as needed in pit-stops.

The winner ran about 74 miles and only won by virtue of a screw-up by the second place driver. The winner's strategy was to build a huge lead by running hard for the first three hours then coast. The runner-up loafed the first half then went flat out. In the end, as he was about to overtake for the lead, a course patrol called out a minute left and the overtaking driver thanked the patrol official...alerting the leader, who cranked up power to win by about 3 feet of bow at the finish.

The next year the two reversed strategies but the previous year's winner took the check again by running a slightly longer, lighter, more efficient copy of his winning hull. He let his competitor build about a 1.5 lap lead, then turned up the wick to pass and, with 30 minutes un-lap, stampeding his target into cranking up to speed and amp-draw that led to terminal battery sag in the last lap. The interesting part was that after the initial 12 hour ordeal of the first marathon the second was reduced to 6 hours...total distance covered by the winner was 72 miles.

I talk with one of the Wye Island competitors now and then and comparing it to the utility marathons I see Wye Island as more social event than race. Probably good fun, but not the sort of lure at the end to suck in hard competitors. The typical utility marathon hull was very long and narrow running an efficient motor and a big prop. The Utility Marathon winning hull was a 25 foot foam copy of a sea-saber pedal boat. It ran a 24v system, the motor was a 1hp Bosch permanent magnet throttled by a PWC controller. power was run through a 90º angle reduction gearbox and u-jointed shaft to turn a 14 inch aircraft-style prop at 300 to 700 rpm. Planing wasn't considered...They just went for slickness and power-thrift.

In the case of kilo boats, we initially used runabouts, including a very wide Sorensen kit, but near the end of the first season one racer got a hydro to work. Motors were never a problem because they're all torque all the time, and pretty bullet-proof. The Prestolite Mike uses has been the motor of choice because it's hard to break and will take over 4 times mfg spec voltage without a melt-down. Batteries in the water haven't proven to be a problem. Rules demand they stay in the boat and the boat have floatation, and the few occasions we've had to deal with sunken batteries none were lost and there's been no electrolyte dilution to indicate leakage.

The big drawbacks have been the weight of the fuel and low rpm. The battery pack for a 144v weighs in at about 500 to 700 pounds, and motor RPM is limited to about 5,500. Also, most e-boats have been conversions of older outboards that weren't really intended to pack the weight and aren't set up to distribute the loads well. Mike's boat set-up changes everything. The hull's modern, a variant of Ron Jones Jr's second-generation D-stock. The batteries are Lithium polymer...Total pack weight of about 80 pounds (about half the weight of the four auto batteries we ran in Brother Will's 48v project runabout) yet have over double the density. When we ran the 48v we had to calculate for distance allowed at max power and tow Freddie to a predetermined start point away from the trap entry. Mike started from the pits with the same long entry, pass and return as any of the gas/alky boats. About a 5 mile total with enough power left for another. And to deal with rpm he ran a step-up gearbox that took advantage of all that torque to spin the prop at the 8,000 plus range where it's happiest.

Finally, as of this morning there's a new video of the run up on Youtube. This ones much better than the first that showed. It's pretty clean and includes good footage from scanner-2

http://www.youtube.com/watch?v=-yNu2_LlO9s

John

[KG4]

HOLY MOLYThat was bad azz

[ram95]

Just out of curiosity, do these "electrical" things make any noise while they are torturing all those poor watts? NO??? Ohhh that's gonna be just great. A boat race with NO noise Well bunky's I'm going to tell you what... I mean WATT. I'm going to convert my toilet bowl into a generator power unit so that when it comes time to 'hook up' and charge those freaking batteries, yer gonna hear some NOISE. Second thought, I've still got a set of pipes I got from Dudley Malone. I'm gonna stick those on my 55H and use that thing for a generator.... yeah,, I'll put a governor on it too... set for about 7200-8000 under load!! Speaking of "load"

Lock n load!
Alex
Mad Russian Racing

[Geezeracer]

It looks like noise r you Alex...Ever considered getting professional help?