Modified Paddle boat. Need more power!

Discussion in 'Jet Drives' started by Chris A Farwell, Nov 22, 2019.

  1. Chris A Farwell
    Joined: Nov 2019
    Posts: 12
    Likes: 1, Points: 3
    Location: Spring Hill Fl

    Chris A Farwell Junior Member

    Good afternoon. Among the few boats I currently own, I have a paddle boat that I converted to be propelled by a 30 Lb trolling motor. Still working the kinks out and am considering some form of jet drive as this seems to be the popular thing to do and the thought of zipping around in it is very appealing. I'm pretty sure due to poor hull design (basically a plastic pontoon boat) that it will never be fast. I'm OK with that. I'd just like to be able to get out of peoples way if needed. Right now it's very slow unless going with the current. It's main appeal for me is that due to a very shallow draft, it will go pretty much anywhere. It also gets us out with our boys with their Kayaks. I mounted the motor in "stealth mode" under and in-between the pontoons in the back with none of it visible while underway (cut the shaft off too). When we launch and/or load up there is usually a small crowd trying to figure out how we are being propelled which I get a kick out of and it usually starts some conversations. My problem is that I usually use it on spring fed rivers (like the weeki wachi river in Fl) and they have a pretty strong current which causes me to keep the motor on high the whole time going up river. Obviously this eats up the batteries faster. Because of this I have yet to make it all the way to the river head. I've tried going while tide is slack and also while coming in. It doesn't really seem to make a difference. I don't really care to invest a ton of money in a pair of 100 AH lithium's and the poor boat won't carry any bigger AGM's. I tried a pair of 75 AH AGM's and the transom was just about underwater so stuck with the old pair of lead-acid 40's I have for now. I will eventually invest in a pair of 50AH LiFePo's (so I can hide them too for the full-on stealth mode) but want to make the rest work first. I have a couple questions for you all. Is a jet drive a waste of time and money for what I'm doing? I'm pretty handy (electrical and fabrication background) so labor will not be an issue, just parts. Will a 3 blade prop give me more thrust than the 2 blade one I'm currently using? And finally, would a shroud around the blades of the trolling motor make it more effective? I thank you all in advance!
     
  2. KeithO
    Joined: Jul 2019
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    Location: Michigan

    KeithO Senior Member

    Build yourself a new boat with much longer and more hydrodynamic pontoons. The "hull speed" of the new boat will be higher and drag should be lower, thus you should go faster on the same power you have now. May need to try to figure out what rpm the motor is running to determine if you need a higher pitch prop. Short blunt hull is always going to be a slug, just accept it.....
     
  3. Chris A Farwell
    Joined: Nov 2019
    Posts: 12
    Likes: 1, Points: 3
    Location: Spring Hill Fl

    Chris A Farwell Junior Member

    Thanks KeithO, I'm not really looking to make it "faster". After all it's a just little paddle boat and just not made for that. I have no delusions of getting this thing up on plane (pretty sure that impossible). I'm simply trying to be able to fight the current on the rivers I intend to explore. I'm estimating the current we are fighting up-river with the tide going out is 4-5 Knots and with the tide going in it about 2-3 knots. I'd be happy with a forward movement of maybe 3-5 knots in either situation. Luckily we put in downriver so getting back is easy even if the batteries are completely dead, the current will bring us home. Goal here is to make ti to the river-head which is 4-5 miles.

    The motor spins at about 1200 RPM on high, Medium is about 800 and low is about 400. I don't want to reinvent the wheel, I'm just looking for something cool that is not common. Assuming all things other things are equal, will a 3 blade prop deliver more forward force than a 2 blade one? I would assume that because of more surface area this would be the case but don't want to tear this thing apart and find that I made it worse. I know I could just get a 50 Lb thrust motor but that would just make the batteries die faster. So not really an option. I'm looking for efficiency here. Maybe a shroud around the blade? That seems to work with fans.

    I've got less than $750.00 (boat was $500 new and $250ish in "stuff") in the project and it works but the run-time is lacking. I'd like to keep the whole thing as cheap as possible. I'd like to keep it under $1500.00 including a pair of new 60 AH LiFePo ($500.00) batteries so I can spend another couple hundred on her. Maybe the solution is to get a couple 100 AH Lithium batteries and be done with it. Not really my style to just do the obvious solution. Kind of a hacker in that sense. Like to make something out of nothing or to use things in ways they weren't intended for. On top of that I found some 60's that will fit inside the same compartment as the motor control, relays and wiring. Want it to look like it was made that way. 100's are just too big.

    BTW, We named her Plan B. The original plan was to use the foot paddles to navigate the local rivers and explore nature. I've since discovered that paddles have to be the least efficient form of propulsion out there. Took one trip out and decided to come up with another form of propulsion. Imagine pedaling with all you've got and still going backwards while trying to get under a bridge. Took 4 tries and we ended up having to accept a tow from a kind gentleman on a jet ski who was also good enough to video the whole thing. I'm sure it's on the web somewhere.

    I've given up on the electric hydro-jet thought. It's just not going to work for what I want. Needs to use too much power to steer, reverse will be a challenge, and we just want to putter around. Maybe another project at a later date (thinking kayak, maybe).

    I've uploaded a pic of the motor we are using and how/ where it is mounted. I used a 1" galvanized floor flange, a 6 inch long 1" galvanized pipe nipple, some good marine sealant and 4 - #10 stainless screws. There is a block of PT wood on the inside for the screws to bite into. It's been stuck in the sand/ mud a couple times and is still holding strong. Once I have all the wiring straightened up I'll upload pics of those in case someone want's to try this as well. At some point I may make the motor turn for steering but for now we are using the rudder that came on the boat. It seems to work OK going forward, but is not very effective in reverse. We use our oars when needed to help her turn.
    20190804_200556.jpg
     
  4. Yellowjacket
    Joined: May 2009
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    Location: Landlocked...

    Yellowjacket Senior Member

    Keith is right, you need a longer boat.. We understand you don't want to go a lot faster, but in this situation even a knot or two faster takes a lot more power. You're battling the effects of "hull speed". That is once you go past the point where your following wave is behind the hull you're trying to climb the bow wave and that takes a huge amount of power to go even a small amount faster. You said you weren't expecting to plane off, but with the length of hull you have now either you plane it or you don't go even a couple of knots faster. If you're hulls were longer and more streamlined you'd be able to go faster on the same amount of power that you are expending now. Longer and more streamlined hulls are what is called for here. That would also give you more buoyancy so you could carry more batteries.. So, with apologies to Peter Benchley... "we're gonna need a bigger boat"..
     
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  5. KeithO
    Joined: Jul 2019
    Posts: 119
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    Location: Michigan

    KeithO Senior Member

    It would be very simple to build using 1/4" ply and fiberglass, you would just have to do sone scarf joints. Go 18-20ft long. You will get plenty of flotation capacity and speed will likely double, maybe more if you have a fine entry and dont have a submerged transom on the back end. My wifes kayak is made from 1/8" plywood (harder to find) and probably weighs 40lb over 18ft.

    For a cat, the pontoons would be narrower than a kayak given there are 2 of them and they make a stable platform.

    The only alternate to investigate would be a lower rpm electric motor turning a much bigger prop, possibly in a duct. This would provide a higher static thrust for your barge like boat. But I fear a custom propulsion system is probably a much bigger challenge than a custom hull. Certainly a custom prop would not be cheap as a 1 off....
     
  6. KeithO
    Joined: Jul 2019
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    Location: Michigan

    KeithO Senior Member

    If you want to see what a die hard electric enthusiast has done who is living on a remote island in panama, you need to look at the cats built by Jamie on Youtube:
    This is the series on his "shark slicer" solar power boat
    Shark Slicer - YouTube https://m.youtube.com/playlist?list=PLZN7OLstp_zmeexx9FkVcuHaKL_3YDeJ4

    So, please bear in mind that Jamie is rather eccentric, very smart and takes advice from no-one so just give the story some time to develop, he does make one of the most awesome electric cats the world has ever seen in a very primitive environment where going to a hardware store is an all day trip in one of his boats... once you understand the environment you will understand more of his choices.

    He moved to Panama btw and renounced his US citizenship after suffering at the hands of micromanaging government in VT on a property that you had to hike into (no roads)
     
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  7. KeithO
    Joined: Jul 2019
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    Likes: 13, Points: 18
    Location: Michigan

    KeithO Senior Member

    If you want to save yourself the construction, try to find something like a hobie 16 and use those hulls.
     
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  8. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    Another thought would be just to add two, new, longer pontoons under the existing ones.
    Simple, long, narrow, light, stitch and glue, glassed.
    The hole rig could sit atop them with the water line at the existing pontoon bottoms.
     
  9. upchurchmr
    Joined: Feb 2011
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    Location: Ft. Worth, Tx, USA

    upchurchmr Senior Member

    Your "power" idea is pretty neat.
    Another thing the typical peddle boat has problems with is wave interference drag between the hulls.
    I once built a rowing catamaran.
    Unfortunately due to my excess weight, the hulls had to be fat to keep my behind out of the water.
    It was rather slow.
    I built another for my 1/2 weight wife with narrower hulls at the same over all width and she was able to run away from me, even with me being stronger rower.

    If you want more physical details send me a PM.

    PS: on the fat boy boat you could see the waves off the bows interfering with each other. The faster I tried to go the bigger the wave interference peaks. :oops:

    Marc
     
  10. Chris A Farwell
    Joined: Nov 2019
    Posts: 12
    Likes: 1, Points: 3
    Location: Spring Hill Fl

    Chris A Farwell Junior Member

    Thank you all for your insight. I already have 2 other boats. one is a 17 foot '66 Searay with a 70 HP Johnson (the old 3 cylinder one) and a 23 foot '84 open bow with a 3.8 OMC sterndrive (Chevy and stringer 800. yes, I know about the stringers). They are the ones I use when I want to go "fast". The paddle boat is using a motorguide 30 Lb thrust 12V with foot control. I have removed everything except the motor and the shaft which has been shortened.

    I guess the solution in this case is Lithium batteries and maybe a shroud around the prop. I have no intention of adding anything to the hull. to make it cut through the water faster. I knew it was a horrible design when I bought it. I need this design to fit in places where most boats won't. Think kayak but more comfortable and no paddling. Draft on this thing is like 8-14 depending on how many batteries I bring. So it is perfect for exploring tributaries. Any longer and it will be tough to turn around on a narrow space. It will pretty much turn in it's own space now with the help of an oar placed in the water at the right time.

    I will also probably drop the motor a little bit because if the stern comes up more than a couple inches due to leaning forward on boat it will cavitate a bit. It's mounted in a pipe with a PTO clip so is easy to remove. Just need to drill another hole lower down the pipe. I will be adding a Fuse/ relay block to fix the rats nest of wires and relays I have to control the speed and direction of the motor and other niceties. Yes it will have lights, USB Chargers, and sound. Already have a small Garmin for it but that might be overkill. It will eventually have a "dashboard" with volt, amps, and battery status displayed. Currently has Voltmeter, key for on/ off, Speed selector switch, and forward/ reverse switch. Still need to add main/ reserve battery switch. I'm also thinking about making a shroud out of PVC pipe to go around the prop to get the most thrust I can out of what I have. If anyone has some insight on this, it would be appreciated.

    If anyone wants more info on the project, I'd be happy to send pictures. Except for having a horrible hull design it actually works pretty well as long as your not in a hurry to get anywhere. Please bear in mind it's still very much in the prototype stage.
     
  11. BlueBell
    Joined: May 2017
    Posts: 860
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    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    KeithO,
    Thank you for the link to Jamie's videos.
    What a kook, I love him!

    C A Farwell,
    As your thread evolved here, it became evident that what you enjoy about the peddle/paddle boat is it's agility and "feeling" of speed.
    I love muscle cars but my favourite car to drive is my brother's Mazda Miata.
    Not because it's particularly fast but because it "feels" fast.
    And, to me, that's thrilling.
    So, on that note, I'm going to make my final suggestion:
    Lighten the boat and crew.
    Weight makes more of a difference to boat performance than perhaps any other variable.
    Good luck, have fun.
     
    Last edited: Nov 25, 2019
  12. Chris A Farwell
    Joined: Nov 2019
    Posts: 12
    Likes: 1, Points: 3
    Location: Spring Hill Fl

    Chris A Farwell Junior Member

    Exactly! She will turn on a dime (with the help of the occasional oar) and will go pretty much anywhere there is water halfway to your knee or so. Also light enough to get out and carry it through the shallows when needed. I guess "faster" isn't what I was looking for after all. I plan on working on weight and battery capacity by changing from AGM's to LiFePo's to help with both issues. I can upgrade the AH capacity 4-fold and cut the weight in half! Only downside is cost. But, they are rated at 3-5000 cycles. That is a LOT of weekends! Still think I will do some sort of shroud around the prop. I will be posting more pics and info as the project evolves. Thanks again to everyone for their input and lack of trolling. Nice to see a forum like this still exists!
     
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  13. Chris A Farwell
    Joined: Nov 2019
    Posts: 12
    Likes: 1, Points: 3
    Location: Spring Hill Fl

    Chris A Farwell Junior Member

    Posting some pics just because. Please excuse the horrible mess of wires and relays. That is all being replaced with a Fuse/ relay block next month. LiFePo batteries come next year sometime before spring. I'll keep posting updates as the project evolves.

    20191125_174606.jpg 20191125_174553.jpg 20191125_174549.jpg 20191125_174540.jpg 20191125_174533.jpg
     
  14. upchurchmr
    Joined: Feb 2011
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    Location: Ft. Worth, Tx, USA

    upchurchmr Senior Member

    Chris,

    After thinking about this, I believe you would get more speed by filling in the gap between the hulls.
    I don't know what to do to mount the drive in a convenient place, but I don't think you will like this anyway.
     

  15. Chris A Farwell
    Joined: Nov 2019
    Posts: 12
    Likes: 1, Points: 3
    Location: Spring Hill Fl

    Chris A Farwell Junior Member

    @upchurchmr
    I had considered that. The front of the pontoons are like a chisel and cause a lot of turbulence under the boat. I had also considered reshaping the noses of each but that just seems like a lot of work for maybe 1 or 2 knots faster if that. I'll just leave the hull as it is and work on run time and of course making it not look like a three-year-old built it.
     
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