My First eBoat Build

[number1cruncher]

Well actually it will be my first boat build as well. I've found the following set of plans that seem easy enough for someone with average wood working skills. Here it is: http://www.boatdesigns.com/10-Imp-flat-bottom-rowboat/products/175/ I have been building things out of wood for over 30 years and feel quite comfortable with this part.

The next part is where I could use some input. Adding power.

My goal is to use an old 9C 9x7 hub as the motor for this thing. I'll of coarse remove the hub from the rim, pull the wires from the axle and redirect them through the side cover. This should allow me to mount the hub between the back seats and use the axle to spin the prop. I'll need to come up with a linkage to extend the axle length into the water. Maybe press a bearing on the axle shaft and support it just above the water line with a cantilever arm to keep the axle straight under load.

Does anyone have any idea if the hub would work in this setup? I'm not sure if the 500W motor (I regularly put over 1000W contiuously through my other 9x7, without much heat) will give me enough power to troll around a lake for fishing purposes. My last concern is using the axle to power the boat. Will spinning the axle instead of the hub wear anything wrong faster than normal? Not that I care too much, as the hub is collecting dust anyway.

Thanks in advance for any advice you have to share!

[Jeremy Harris]

That boat is OK, but will need a fair bit of power, as the transom will create more drag than you want for electric power. If you want a simple to build boat with relatively low hull drag, then I'd suggest looking at some of the sharpies, dories or perhaps the bateux flat bottomed canoe, or maybe even the West Mersea Duck Punt (Which is what I'm building at the moment). Here's some links to free plans that may be of interest:

A pretty good 14 ft canoe from 2 sheets of ply: http://www.bateau.com/freeplans.php

The West Mersea Duck Punt plans: http://www.keepturningleft.co.uk/galler ... t-gallery/

Free motor Pirogue plans: https://secure.boatplans.dk/pictures.asp?id=57&page=1

Free 12 ft dory plans: http://koti.kapsi.fi/hvartial/2sd/2sd.htm

Free light sculling boat plans (probably a bit tippy, but fast): http://koti.kapsi.fi/hvartial/scull1/scull1.htm

First off, you can't make the axle go around on the hub motor, unfortunately, as it's connected to the stator and has all the wires going to it. The other problem is that hub motors go pretty slowly, a bit too slowly really unless you want to use a very large diameter (say, around 15") prop. You could arrange a drive off the outside of a hub motor, using a belt to another shaft, but overall I'd suggest it's more trouble than it's worth to do this. Several people (including me) have had success with under-running fairly large RC outrunners. Under-running them means they run cool and are generally more efficient. These will need a reduction drive though, of between 2:1 and 3:1 to get the shaft speed down to something that's about right.

You'll find you only need around 100 W or so to propel a slim boat around at normal rowing/paddling speeds, as long as the motor, reduction drive and prop are properly matched.

Jeremy

[number1cruncher]

Thanks Jeremy! You have given me some things to think about. And things to abandon...

I'll update this thread once I get further into the project.

[dnmun]

yeh, don't waste a great hub motor on a boat. i wonder why there is not more investigation of the trolling motors for power. only a few comments on the board so far, and the overvolted one held up for a while until the plastic brush holders melted.

[Jeremy Harris]

yeh, don't waste a great hub motor on a boat. i wonder why there is not more investigation of the trolling motors for power. only a few comments on the board so far, and the overvolted one held up for a while until the plastic brush holders melted.

TBH, they are pretty rubbish when you take them apart. Every one I've looked at has been a cheap and nasty brush motor, often using big, switched resistors in the lower unit for power control Often called something like "power coils" by the manufacturers). The most powerful ones I've seen are capable of around 1kW or so when cooled by the water around them, and even then they struggle to get better than around 75% motor efficiency.

The exception is the Torqeedo range, which use RC outrunners in the underwater unit, driving the prop via a epicyclic reduction gearbox. These are pretty powerful and efficient, but are a bit noisy (the gearbox tends to whine a bit) and they are very expensive (several times the cost of a typical trolling motor).

Trolling motors, even cheap ones, can be massively improved with a bit of work, though. A chap on the Boat Design forum, MCDenny, did some great experiments and got a great performance and range improvement with a few cheap mods. See here for more details: http://www.boatdesign.net/forums/boat-d ... post305142

Jeremy

[amberwolf]

FWIW, if you really did want to use the hub motor to drive the prop, you could raise the voltage sufficiently to compensate for the lower RPM at lower voltages.

Then, if you can make a sufficiently strong clamping mechanism for a single end of the axle (the wire-end) to prevent it shifting or turning, preferably clamping it thru a thick-crossection plate to help prevent lateral movement, you can directly drive the prop using a tube bolted to the hub's cover plate on the other side from the mounting.

I doubt this is the best way to drive the boat, but if you already have the motor and want to try it, you could still return the motor to ebike or other service if it ends up not working as planned.

[Xanda2260]

Well actually it will be my first boat build as well. I've found the following set of plans that seem easy enough for someone with average wood working skills. Here it is: http://www.boatdesigns.com/10-Imp-flat-bottom-rowboat/products/175/ I have been building things out of wood for over 30 years and feel quite comfortable with this part.

The next part is where I could use some input. Adding power.

My goal is to use an old 9C 9x7 hub as the motor for this thing. I'll of coarse remove the hub from the rim, pull the wires from the axle and redirect them through the side cover. This should allow me to mount the hub between the back seats and use the axle to spin the prop. I'll need to come up with a linkage to extend the axle length into the water. Maybe press a bearing on the axle shaft and support it just above the water line with a cantilever arm to keep the axle straight under load.

Does anyone have any idea if the hub would work in this setup? I'm not sure if the 500W motor (I regularly put over 1000W contiuously through my other 9x7, without much heat) will give me enough power to troll around a lake for fishing purposes. My last concern is using the axle to power the boat. Will spinning the axle instead of the hub wear anything wrong faster than normal? Not that I care too much, as the hub is collecting dust anyway.

Thanks in advance for any advice you have to share!

Am I being dense? Surely this won't work. The wires are connected to the stator, which is joined to the axle. It seems you intend to hold the rotor stationary, and have the axle spinning. This means the stator (and wires!) will be rotating! Without some kind of brush/commutator setup the wires will tangle in seconds.

[Jeremy Harris]

Am I being dense? Surely this won't work. The wires are connected to the stator, which is joined to the axle. It seems you intend to hold the rotor stationary, and have the axle spinning. This means the stator (and wires!) will be rotating! Without some kind of brush/commutator setup the wires will tangle in seconds.

Which is precisely why my first reply post above said this: "First off, you can't make the axle go around on the hub motor, unfortunately, as it's connected to the stator and has all the wires going to it. "....................

[csmarr]

Think out of the box. Mount the motor in a front fork and attach paddles to the spoke flanges. Make it a paddlewheeler. Heck mount two with one on each side.

[Jeremy Harris]

Think out of the box. Mount the motor in a front fork and attach paddles to the spoke flanges. Make it a paddlewheeler. Heck mount two with one on each side.

Better still, fit paddles to bike wheels and add a third wheel that can be steered and lowered when required. That way you could have an amphibious trike.............

[Xanda2260]

Am I being dense? Surely this won't work. The wires are connected to the stator, which is joined to the axle. It seems you intend to hold the rotor stationary, and have the axle spinning. This means the stator (and wires!) will be rotating! Without some kind of brush/commutator setup the wires will tangle in seconds.

Which is precisely why my first reply post above said this: "First off, you can't make the axle go around on the hub motor, unfortunately, as it's connected to the stator and has all the wires going to it. "....................

Oh yeah. Sorry Jeremy, clearly I didn't read that properly.
My bad