Electric Rowboat for 100 mile race

[Tom the rower]

I have made a 20 ft 2 man high sided rowboat, 10 ft oars, sliding seats, flat bottom boat. I rowed for about 2 years before a friend suggested his trolling motor mount and his 3 hp trolling motor, that he described as the most powerfull 12 v trolling motor made. Well, now that I have added that darn trolling motor, I can never go back. I row my river, here in Jacksonville,Fl at dawn and sunset, both per day, on a fairly regular course, of about 2.5 miles per day. I use a normal deep cycle battery. I never run out of power, and frankly, there is a kind of groove thing that happens with the combination of rowing and electric, both building on each other, each helping.

I want to participate in next year everglades challenge, a 300 mile race. But, I will have to finish the north carolina challenge in sept, on the outer banks, which is 100 miles. I could probably row it alone, but now that I have been exposed to electric, I am spoiled.

So, I would like to trade out my deep cycle battery for a pair a of GPL 4C 6v batteries wired in series for more effeciency. Would a torqeedo do the trick for me. What I am worried about is especially rowing into the wind. Right now, the trolling motor makes this do-able, as I normally face big wind and 3 ft waves with no problem, thanks to the electric. Granted, my speed is around 2.5 in a big wind, but this morning, with no wind, and rowing hard I was at 6.1 mph.

Any ideas are most welcome

Thanks

Tom the rower
Jacksonville, Fl

[mr.electric]

I have posted about my electric canoe set up a few times here on Endless Sphere. I suggest using a lithium battery with your existing motor. You could probably spend $250 and get a 20 amp hour lithium pack and charger - good for a few miles with no rowing. Your deep cycle probably has about 60 -80 amp hours but since it is lead it is only delivering about half the rating.
Starting with a small lithium pack would help learn the technology with a small initial investment.
Most people here on Endless Sphere buy lipo batteries and chargers from Hobby King use in ebikes. I used the same for my canoe motor.
Other e boat thread:
viewtopic.php?f=39&t=19115&start=15

[liveforphysics]

Weight in boats is extremely extremely important. Every extra pound you carry is an extra pound of water you displace, and hence and extra pound of water that must be pushed out of the way for your boat to move.


That 220Ah Lead acid battery you suggested would honestly be a terrible choice.

I also think operating at 12v is foolish option as well, I would recommend at least 48v to keep your conductor loss and wire weight down. Lithium is definitely the way to go here. If you're not looking to learn much about batteries, a couple of Ping 48v 20Ah packs would be good. That would give you about the same usable capacity of the 2 6v lead batteries you were considering, but at a small fraction of the weight, and they should last over a thousand uses for you, automatically stopping charge when full and cutting off power when drained to protect themselves, so you don't have to worry about much.

The efficiency and performance greatly comes down to the prop. Normal boat props are pretty awful, and designed around clearing weeds and durability over efficiency. You want a very large diameter very thin prop, much like the prop from a large RC airplane. The downside, is anytime you're going near weeds you will need to lift the prop out, or you're going to be spending a lot of time untangling weeds, and if you even bump a rock it's shattered, and the leverage may also bend the prop shaft or break the drive motor.

If you want to find how to do efficient human power boats (and then convert this efficient drive system to be electric power). The human body can only give about 300watts, so when they want to set a record for the fastest or longest traveling human powered boat, they have to come up with designs that use every available watt as efficiently as possible. The long thing props are what all the record holders for speed and distance use.

[Lock]

+1 on what liveforphysics said Tom. The two Ping packs he refers to with similar energy storage will lighten the boat by 88lbs. Purchase cost about 2.5x as spendy as the lead but will last 2x or 3x longer. Much less voltage sag with the LiFePO4 also as the charge is consumed.

Row on!

Lock

[Tom the rower]

I have studied electrifying by bike and have seen similar batteries suggested there. So, I could see adding the batteries, but does that not make my trolling motor not able to be used? I have no problem taking along some APC props. They seem plenty cheap. My expedition boat is 20 ft long double ended like a canoe, 20 high sides at the end, but at the middle it is 17 high, so that helps the boat have no rocker. I have spoken with Rick, and do intend to do a design he did for me for a dedicated pedal boat, that could also serve as a test bed for these same electrics. But, I still want to use this boat, as described for this race, so bulding the long slender hull shape with two outriggers is not my wish for this race currently. This hull is the expedition hull. I do not anticipate a electric only time during the race. It will either be rowing alone, or row/electric assist, with possible pull overs for a small sleep/eat period,during which I would have a beefy battery charger to quick charge the batteries. So, I say it is a yes to the batteries, but where does that leave me for the motor and prop. APC 16x16, and plenty of them or something like apc20x20. We have 3 navy bases here, and a few miles away are friends in my former submarine community, so I suppose I could try to make my own props, carbon fiber with stainless core, but I would rather not at this point.


Very interested in your responses.



Tom The rower

[mr.electric]

The Torquedo has a special efficient prop and comes with lithium batteries. Otherwise a regular trolling motor costs about 1 / 20th the price of a torquedo motor and lasts forever. I think the efficiency gain from going lithium with a basic trolling motor will be a quantum leap from using lead. You could always go with the special custom prop/ brushless motor set up later if you have time to do a bit of R&D or some cash to spend on a torquedo.

[Beachcruzer]

I was a competitive rower and coach for many years. One thing to consider is that a rowing shell has an oscillating power curve unlike any other type of boat. It accelerates and decelerates significantly with every stroke cycle. If you're going 6.1 mph average, your speed is varying between about 5 and 7 mph with each stroke cycle. 5 mph just after the catch, and 7 mph just after the release. In a 100-mile race you'll probably be rowing at 18 or 20 strokes per minute, so that's 1,200 cycles an hour, for however many hours it takes you to finish (20?).

Just bring that up because it could have some bearing on motor load, cavitation, and the type of prop you want to use. If your trolling motor is working as a daily driver I'd stick with it.

Re batteries, do what these guys say. I'd house the batts in a Peli box or big ammo can (20mm "rocket Box")

[bigmoose]

A chap who might be able to help you a bit is Jeremy Harris. He was an active member here for quite a while but now appears to be focused on his boat building. You might be able to tag up with him here http://www.boatdesign.net/forums/profile/jeremy-harris.html He built an electric drive canoe a few years ago the ran off a drill motor. He is quite proficient in boats and is quite an efficiency expert on drive systems.

[Lock]

Tom

Just to give you an idea of Jeremys expert opinion, he posted some pics of a recent boat building project of his together with his approach to what an efficient electric drive might look like, in this thread:
http://endless-sphere.com/forums/viewtopic.php?f=39&t=9806&start=101

[Tom the rower]

Well, I like the battery idea, as I could use them for a powered bike as well, but so far, I haven't found a 48 volt trolling motor without a short stubby shaft, and all the 48 volt trolling motors seem to cost something like $1200 to $1400. Also, since the power consumption curve vs speed seems to be exponential, my buddy who a manager of a West Marine told me that I would extend my battery life a whole bunch by running the trolling motor at 3 instead of 5, which is full out. Would that hold true with 48 volt, and would that medium power on the 48 volt possibly be faster or more powerfull than the same speed setting on the 12 volt?

[mr.electric]

Yes you need a 12v lithium battery.