5 hp motor: highest reliability, highest efficiency

Those are huge props... would take a ton of reduction... I've had good luck with 48 volt 100 amp esc's on 6354 size motors... you've got to be geared right. Those props look homemade... are they? A couple of 8085 motors might be the ticket.
 
I agree with John about the direct drive inboard design. I think that is the way to go for best efficiency.
A propeller that is well matched to the Motor Power/RPM will also make a big difference. Too big/too steep of a pitch and it will bog down the motor, and too small/low pitched and the motor power will not be fully utilized. And there's also 2-blade, 3-blade, and more. You want your motor to be spinning at it's most efficient power/RPM at full throttle. I would recommend starting with a 3-blade prop similar in size to what would come on a 10hp outboard motor, and adjust from there.
 
You could probably find a nice Etek motor somewhere. Rated 6HP continuous, 15HP peak. Yes, it has brushes, but state-of-the-art for a brushed motor. I have one sitting in the garage. Water cooling would be difficult, but force-air is easy.

I love the Flyak and other designs that minimize the drag on the boat. Weight is a critical factor, as the heavier the boat is, the more water it has to displace when moving.
 
I too am a big fan of wooden boats and boat building.... in particular stitch and glue type contruction. I've wanted to visit the area where this event is held and the Okume Fest put on by Chesapeake Light Craft. I have a couple of hulls in work and want to build a poor mans version of a Pacific Style Shunting Proa. I bought a prop off ebay just before getting involved in the EV stuff. My original intent was to use it with a reduction drive on a 5hp briggs and stratton in a modified dragon tail arrangement on a hobie 16. No steering just the ability to lift it out of the water. It is a very thin blade section and should slice through the water very well. I think it was originally on a sailboat. It is a fairly low pitch. Just for grins I may have to try it with a brushless motor on a kayak or even the hobie.... not much room for batteries on a hobie.

I think with a direct drive arrangement it will be much harder to match ideal motor speed to ideal prop speed.

The foil idea is killer... curious to know what size foils it would take to lift all the weight of batteries and gear.

hulls2.jpg
prop.jpg
 
Though the motors I'm talking about are capable of the rpm you want as direct drive, I was thinking of running them with a relatively small reduction. Then you can easily change the gearing and try some different ratios to determine the optimum through water trials. That would also make contra-rotating props easier and that efficiency gain would more than offset the 2-3% loss of the belt or chain reduction. To me, you really need flexibility to get things exactly right. Also, a small reduction enables you to retain near silence.

As a side note I am on the hunt for proper inrunners that should be able to beat the Torqueedo's in all respects except maybe weight. Maybe they've gone to inrunners in their larger motors, but the smaller models that definitely run outrunners is completely baffling. If I find inrunners to match what I have in mind I'll let you know.
 
LOTS of great input. Thank you all. Some replies, from the top:
yawstick: yes, those are homemade props and I had minimum power to the motors (6374) when they torched. I was using a 120 esc and a 100 esc. Both burned. Truely I turned the AstroFlight servo tester only a wee bit.... I'd be inclined to use GoldenMotors bldc's with their controllers, but will burn no more money burning RC ESC's. My props had little pitch compared to a 3hp outboard prop. A little more than a trolling motor prop.
:?
teslanv, John in CR, yes, I'd like to go direct drive. somewhere there's gotta be a prop that can be fitted and modified. I realize the prop is the essence of the whole thing, but so far I haven't even got a motor that would allow experimenting with the prop. I am determined at this point to pursue an inboard motor and a long shaft, probably flexed to minimize downward thrust.

Martin A: the Flyak is King. And yes, foils are down the road. Torqeedo has one such entry already
http://www.technologicvehicles.com/en/green-transportation-news/1799/hydrofoil-torqeedo-motor-quadrofoil-2012-s-most-futuristic-and-desirable-electric-boat-breaks-cover#.VE_-avTF-Ko

Fechter, a single Etek might work; I do want to stay within the 8KW limit and not be in the "Extreme" category. I'd prefer two dragontails, so am looking in the 5hp/3.7KW arena for motors. Then again, I think my Elektra is light enough that one motor might get her on plane and do 18mph and better....

What's truely demanding in this pursuit of folly, is the task of completing the 24 mile distance. As I pointed out earlier, with 24 lithium modules, weight about 200lbs, I finished third.

Yawstick, the MASCF in StMichaels is your place to be next October.

John in CR, I'd want to spend a lot of time exhausting the possibilities of direct drive before I introduced yet another variable like gears and varying reductions. And the complexities of bulk and weight, etc. I'll follow your lead and look at inrunners, but unless someone is manufacturing controllers matched to the motor, I can't see spending the money.

My thinking is that a variable speed motor already provides the flexibility to get things pretty right. My homemade props are crude, but that homemade route is the only one I know to provide counterrotating propellers in the minimal hp range I'm messing with. And I can change the pitch in a couple hours with a protractor and a vise and some levers.
 
I'm curious to know how much reduction you had when running the RC motors. With props that large even with a low pitch I'm thinking it would take a minimum of 50 to 1 and probably more. It does not take much prop at all to properly load a 5 hp motor. Take a look at the prop size on the Torqeedo. I dont know anything about the Torqeedo but my thinking is you would be hard pressed to improve on the efficiency/reliability of a package like that. It would certainly be fun and a challenge to try though. I'm also thinking a single prop would be preferable to two. Possibly even two motors turning a single prop. There are plenty of props on ebay for relatively low cost. Old vintage bronze props similar to the one I have and props specifically for the dragontail mud motor applications. It is an interesting project.

http://www.ebay.com/itm/Elto-Evinrude-C-Service-Racing-Outboard-Antique-Hydroplane-Bronze-Prop-1930s-/291279507055?pt=Boat_Parts_Accessories_Gear&hash=item43d19c8e6f&vxp=mtr

http://www.ebay.com/itm/MUD-SKIPPER-Longtail-Mud-Motor-Propeller-5-Pack-6-25-6-5-7-7-5-8/201205982620?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D27538%26meid%3D64ebdb1b5926448ab8c48756646f0097%26pid%3D100005%26prg%3D11353%26rk%3D3%26rkt%3D6%26sd%3D301371627219&rt=nc
 
yawstick said:
I dont know anything about the Torqeedo but my thinking is you would be hard pressed to improve on the efficiency/reliability of a package like that.
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I think just the opposite. Torqeedo does a great job making their stuff look cool and futuristic, but what's inside doesn't impress me in the least. They use common outrunners as the motor with a planetary gear reduction and a built in controller. The much larger diameter tapered shell means they don't even have a good heat path for cooling. The little one has just a 52mm diameter outrunner, and in their literature they try sell it as big plus. Great look and great marketing gives them tremendous margins.

If there was ever a need for a brushless inrunner, an electric outboard is it. Then you can have the stator steel in direct contact with the shell for great heat transfer, and you could do the whole thing in a smaller diameter and reduce hydrodynamic drag compared to the Torqeedo. Personally, I'd want to eliminate the gear reduction to silence it, which will require quite a bit more motor weight, but imagine the power potential and reliability of a brushless inrunner with that kind of cooling and a size similar to common trolling motors.
 
Punx0r said:
How about the "5kW" brushless motor here: http://www.goldenmotor.com/frame-bldcmotor.htm

I don't have any experience with it, but it's water cooled and some research should turn up useful user reviews.
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This motor was mentioned recently in this thread about its smaller 3kW sibling - which looks interesting. LFP tried the bigger ones and indicates that the heat path isn't the best for flogging the bigger versions, but if you used two of the 3kW units at modest over-power levels the water cooling should work out okay.

You can find the efficiency/power curves in that thread. No experience with them, but if you want to go with a deuce....
 
John in CR said:
yawstick said:
I dont know anything about the Torqeedo but my thinking is you would be hard pressed to improve on the efficiency/reliability of a package like that.
Click to expand...

I think just the opposite. Torqeedo does a great job making their stuff look cool and futuristic, but what's inside doesn't impress me in the least. They use common outrunners as the motor with a planetary gear reduction and a built in controller. The much larger diameter tapered shell means they don't even have a good heat path for cooling. The little one has just a 52mm diameter outrunner, and in their literature they try sell it as big plus. Great look and great marketing gives them tremendous margins.

If there was ever a need for a brushless inrunner, an electric outboard is it. Then you can have the stator steel in direct contact with the shell for great heat transfer, and you could do the whole thing in a smaller diameter and reduce hydrodynamic drag compared to the Torqeedo. Personally, I'd want to eliminate the gear reduction to silence it, which will require quite a bit more motor weight, but imagine the power potential and reliability of a brushless inrunner with that kind of cooling and a size similar to common trolling motors.
Click to expand...

I agree. I would go with a long skinny inrunner with the stator all potted and the magnets coated with epoxy or something to prevent corrosion. I would go direct drive, and spin a cut-down model airplane prop. Boat props are only shaped the way they are for weed clearing properties, if you want it efficient use little cut down carbon RC boat props, and if you hit a patch of weeds, you will need to manually clear the prop.

Keep in mind low weight is way more critical in a boat than in a land vehicle. Each pound of weight added to the boat is another pound of water that has to be displaced out of the way of the boat as it moves.

If I personally were doing this contest, I would run deathbikes drivetrain, and spin a prop that could efficiently load it. Likely direct drive off a long section of pipe for a driveshaft with a prop mounted at the end.
 
Once you are on a plane, weight matters not, only contact area with the water. The key is getting on a plane, and weight does matter for that, but so does hull design as well as weight distribution.
 
Re the Torqeedos: in the Wye Marathon the Cruise R's have distinguished themselves: three years they've come in first and second and this year 1-2-3. Yes they have a large enough motor bulb. Enclosed also inside are some electronics that benefit from the immersion.

Re narrow airplane props used in water: I'd sure like to see match racing comparisons between them and perhaps a threeblade outboard prop. Wouldn't you think Evinrude etc. would have adopted even a faint hint of an airplane prop if it were viable?

Hi-speed offshore boats often choose to run surface piercing props, that look like 5 machetes arranged radially. Others choose total immersion, two and three broad blades. All spinning relatively fast. They have power to burn, and they do it. Batteries need more finesse. I'm still admiring the variety of motors and their controllers and searching for the right combo. Knowing that the powerplant needs to cover 24 miles with a total weight of 650 or 700 lbs. And ultimately, cover the distance in a little over an hour.....
 
I would just put a water ski on the front of the death bike.... a fat sand digger tire on the back with paddles on it.... a flying start from the bank.... and don't slow down. Could be the first motorcycle to pull a wheelie on water. :mrgreen:
 
I just finished watching some Youtube excerpts of motorcycles and motor testing. I'll have to add another criteria to Reliability and Efficiency: NOISE!!!
The PERM 132 and the brushed ETEK motors I tuned to are NOISY. The PERM 132 sported some nice numbers, but they came at the expense of whine.

I'll have to go back and re-read--which I do often, because all you contributors have important things to learn. But somewhere back there someone did talk about noise, and I'd glossed over that. Wrong.

Lots of comments about gear reduction and how big the 5-bladed props are. They are in fact 8.5" in diameter. A torqeedo 801 is 12 inches in diameter, and I think it's limited to 1300 rpm. At least the Cruise 4 Torqeedo is. I located the propeller shaft just above the bottom of the boat's hull, in an attempt to experiment with surface piercing props. Theory being that once a little bit of speed was gained, water off the stern plane would become more and more in line with the lower half of the propeller. Granted there's large torque demands at startup, but as I continue to protest, I was gentle on the dial. I guess not gentle enough.

Anyway DRAGONTAIL is the new goal, QUIET and RELIABLE and EFFICIENT are the goals. Thanks for your input on Motor Selection. I do think I'm tending to brushed PM motors to stay away from electronic gremlins.....
 
Bliss, the problem with all the other motors brought up is that the rpm is too high. The motor I'm talking about turns exactly the rpm you want in near silence, and with plenty of torque to swing an even bigger prop than the torqueedo . The manufacturer rates it at 3kw and tested it at 92.7% peak efficiency. With easy air cooling mods it can go to high power (12-15kw easily), and like I said initially I'll guarantee results. If you really wanted you could go to much higher power than that, but that requires higher voltage and higher rpm to push it into the 20-25kw range. A brushed motor in the 10-15kw range turning less than 1500rpm will not only be massive, but it's virtually guaranteed to come in at 10-15 points or more lower in efficiency, definitely not what you want for a 24 mile continuous run. Regarding your electronic gremlins concerns, the controllers matched to the motors would be part of the deal.
 
You should be able to use a hydrofoil and get the hull of the water.
Using a dc series motor you can generate a ton of torque to pull it up out of the water,
and then drop the current down to keep it flying.
 
Right on, JackB. To pursue that: America's Cup boats, A class catamarans, the Torqeedo powered sportboat mentioned earlier in a post, all use a curved foil, J shaped. That's probably the best shape, based on popularity. Inverted T's also abound, like in the Moth and the adaptation for the Laser.

Whatever shape used, power to the water is going to be by propeller. A rightangle drive under water, like an outboard, will have to sit pretty deep, or be varied while the boat is moving. The Torqeedo sportboat is fixed. A dragontail prop contends with the same issues, with perhaps a more readily activated depth adjustment. With that asset comes the power loss inherent with the angled thrust which tends to push the stern up, the bow down.

The amount of thrust, angled versus inline, is not something I'm qualified to calculate. The amount of drag imposed by the underwater gear pod, or the immersed Torqeedo motor pod, is likewise hard to figure. Is a dragontail prop with no pod, churning perhaps a foot below the surface at an angle, going to be more efficient? (Here's where one ES member motto stands out: to paraphrase: a single test is worth a thousand opinions).

If all of these considerations applied to a one-mile race, some answers would be clear-cut. But when applied to a 24 mile race, with 15kW of Li batteries weighing about 240 lbs, all these small variables grow significantly. Probably one answer is write less, crunch numbers more.....
 
If you run a straight inboard, then the shaft can exit the hull somewhat forward of the transom, and the upward force resulting from the angled shaft will help provide lift to the entire boat instead of lifting at the rear causing the bow to plow. Then you have a much finer form in the water. 2 bulbous motors ala Torqueedo robs power, as does the gearbox and bulbous lower unit of the other approach you mentioned. You can't trim an inboard, but your boat will be light enough that you can trim the boat using weight distribution. That's what practice runs are for. :mrgreen:
 
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