17 lbs thrust trolling motor how big a boat?

[switters]

I have recently taken possession of a 17lbs thrust Minkota trolling motor which seems to operate nicely, thanks Mariah. I can mount it on one of the canoes, and don't want to. I can mount it on the OSS but then I would be solo. The summer breeze is going to Oregon soon, and the GIS which is starting this month needs more than 17 lbs and I don't know if I need a trolling motor with that anyway.

So, if you care to dream with me, what would I build that would accomodate 500lbs of people and fishing gear and maybe one or two beers, with a hull wieght of less than 500, trailers are abundant and so are pick-ups in my world. Protected lakes, trout fishing. construction methods could stretch my skills, like a lapstrake somethingish. I kind of envision a character boat like a mini simmons skiff or something I can fish out of but still not sit on the floor.

Total weight based on 17lbs thrust*70=1207lbs total weight wich is a "rule of thumb" I picked up off of the internet. This could be totally useless for all I know, hence I bow before the collective wisdom of the WBF.

I wont be building until the spring but I am getting wood ordered for the GIS and want to pick a design soon if it ends up needing marine ply, which has to be "imported" in this town.

Thanks,original designs will be considered, winner gets a free boat ride anytime they come to Colorado. The amp eater has already been looked at and seems to need more power than I have available, though not sure about that; Amp eater is 1/2 hp, but with a hull wieght of about 200 lbs it could be a contender.

[switters]

http://www.selway-fisher.com/Steamup20.htm#FELIX

a steam launch, 13-feet, very salty looking, with a place to hide batteries.

the propulsion unit could be taken apart, I'm guessing, and then only a through hull for the wiring would be required.

That's one heck of a great idea, how fast do you think it will go?

I don't know, as long as it can move against a 15knt headwind so I can get off the lake that would be fine. Hmmmm....

a solar panel charger would be a neat addition to this little experiment. possible pole mounted so it could be rotated to face the sun.

[ben2go]

Here is my experience with a 20 pound thrust Minn Kota.

Boat=Flat Bottom Jon Boat 10 foot long with 32 inch beam and 27 inch bottom
Weight=Boat 55 pounds
5HP outboard 45 pounds
Trolling Battery 65 pounds
Paddles 5 pounds
Me 210 pounds
Fuel tank is on the out board=included in out board weight
So that's a total of 380 pounds.The motor struggled to push the boat.Once it was up to speed it was fine until a head on wake or chop.Then it would struggle.It couldn't hold the boat steady in the wind,especially a head wind.The out board was pulled up to eliminate any extra drag in the water.I've only seen small trolling motors used on Jon boats and canoes.

[patrick.blanchard]

The trolling motors have thrust, but no torque (power). If you look at the prop on the salty, it's a big screw designed for low rpm of the steam engine; a great combination for a slow and powerful drive train. Now look at the trolling motor prop and you see a deep pitch and small diameter. It is designed for high rpm and is terribly inefficient. To move against headwind w/ 500+ lbs, the big, slow turning prop is ideal so the trolling motors are on the other end of the power curve. When working a solar panel, efficient use of electrons is the rule. It's OK for charging the batteries but don't expect it to supply the amps for any electric drive train for a boat.

Just put the steam engine in, so after you have your catch you can cook up the shore lunch faster than you could grab the dinner bell.

[willmarsh3]

Just for reference I have an 80 lb thrust motor on my Elver. The displacement with two people aboard and supplies - about 1600 lbs. It pushes her along fine and into winds and chop at about 3 knots or so.

If I scale these results down to a 17 lb thrust model then I'd estimate that it is sufficient for a one person kayak or canoe sized boat with maybe 30 lbs of provisions. Or something like a shellback dinghy might work.

For this size of motor I'd surmise that it uses speed coils for speed control. This means resistors as opposed to pulse width modulation. This is fine while running at full speed but inefficient at lower speeds.

As for a solar panel the rule of thumb is that for each amp it puts out it will produce 5 amp hours per day. The motor (presumably 12v) draws about an amp for each pound of thrust it puts out.

Given this a 4 square foot poly crystalline panel putting out 50 watts or 4 amps facing full sunlight could over the day supply 20 ah or enough power for about 1 hour of run at full speed. The battery (with a charge controller) would tend toward being fully charged too which is very good for the battery.

The solar panel would have to be mounted on some sort of canopy to avoid shadows and keep it out of the way. This leads to any number of intriguing boat designs such as the Enigma seen on www.microcruising.com and http://e460.blogspot.com/

[switters]

Thanks guys just the experiences I was looking for, sounds like I should scale back any plans for building around such a small trolling motor. My inner hippie wanted the solar charger but it probably wouldn't add much to the usefulness of the boat.

I'm thinking a small punt would be ideal and slow, although no where near as sexy as the Felix. I might just make a mount on the one sheet skiff and use the trolling motor for the kids to play with.

[ben2go]

I upgrade my 20 pound thrust to and 55 pound thrust unit.