Another Try at an Electric Catamaran

Discussion in 'Boat Design' started by Motivator-1, May 29, 2010.

  1. portacruise
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    portacruise Senior Member

    FWIW comments above.

    Porta
     
  2. Motivator-1
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    Motivator-1 Junior Member

    Thanks Porta,
    As I mentioned I'm looking into the more efficient Outrunner Motors and comparable Prop drives. I still do not want the Asian Weed-Eater-Prop drive system because I am designing a Fishing Boat. I might re-consider a single higher power Trolling Motor setup like on my present boat which is only 45lb thrust. The present Bridge-Deck already has provisions for Pull-Pull type Steering System by way of Cables, and a Tilting motor mount, along with a unique "Foot-Steering" capability already designed. I just want to know "How Fast Can I Go"???? I have bailed out of the Trolling Motor concept because I cannot seem to get the Data I need or that I can understand as to the potential power available, only that I should not be trying to design a Tug-Boat, albeit that what I have presented is not the best.

    Effiency to most here seems to be squeesing out ultimate performance with a given Drive and Prop and Smallest Battery. To me, it is the fact that I can fish all day, and still come home on a single charge, and require only about$0.25 cents to charge back up. To me, that is effiiciency enough, as I am not that much of a Tight-Wad, and I'll gladly spend 50 times that for the enjoyment that the boat brings to me and the many passengers that waited in-line for an oppurtunity to go fishing with me, and catch the "Poundage" of fish that we could with this very unique Boat and fishing method. The fishing methods that I unfolded are reasons for a whole other thread here or elsewhere, or a book of it's own...believe me!!! I will add Battery, and what else is necessary to fulfill my Boating needs. My last boat was so successfuly catching fish, that I and the Boat became Legendary around here in Jupiter, Florida. I'm just trying to do better. It's all about "Quiet-Trolling" at very low speeds. I occasionally need to pick-up and move quickly to a new spot or to get to my initial spot, hence the need for more speed.

    I hope you guys can feel from where I am coming from....... and continue to help me. My Freezer is getting Low on fish!

    Thanks,
    John
     
  3. portacruise
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    portacruise Senior Member

    how fast

    Motivator, the fastest I've ever driven a streamlined carbon fiber catamaran with the largest minn kota troll modified for speed with only me on board is 6 knots. Some fishermen use gas longtails and I use a small portable electric version for same. I was just putting ideas out there and trying to help, not aware where you were coming from....

    Thanks for letting me know.

    Porta



     
  4. Motivator-1
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    Motivator-1 Junior Member

    Hello Porta,
    I hope you did not get the wrong message from my earlier post. I just seem to not quite understand why there isn't more that can be done to tap the power of these Trolling Motors. My last 18' Catamaran was heavy with 2 65 lb fiberglass hulls, a stout 185 lb Bridge deck, 2 105 Amp batteries, Anchors, Bilge Pumps, Ice chest with 15 lbs of ice, Depth sounder, Oar, Bait well pump, Tackle boxes, etc. I powered it with a single 24 Volt Motorguide 45 lb thrust motor and got 5 1/2 MPH (5 knots) out of it with no fancy props, just a slightly larger one from another model. Does this mean that by going to 2 107 lb motors, and adding more battery weight, that 6 knots is all I'm going to get? If that is the reality, then I'll persue the Outrunner motors and build the drive system for them, but I'll have a learning curve ahead in designing what size motors, reductions, and controls would be the best. You guys have thankfully pointed me to a lot of information about this, but again it is generally for modest light weight craft at modest speed. Rick's numbers show that I can power my hulls or his JV6 hulls up to 10 MPH by throwing more wattage into them.

    So far, I have found what I believe is the largest Hobby Outrunner motor from Turnigy, the the C80-100-130B or the C80-100-180B. Would these be large enough, or is there something out there more appropriate? It would be great if I could do a 24 volt system, but it seems 48 VDC is what is called for, so I'll probably need to look into the higher tech batteries, or have to use 12 volt Lead Acid batteries in series. My problem with the 48 volts is that I would have to run long wires from the 2 batteries in one hull to those in the other hull to get the series connection, instead of having 2 separate battery banks, one for each motor. Keeping the motors cool in the damp environment inside the hulls is another issue I need to work out. That is the direction that I am presently heading in.
    Regards,
    John
     
  5. portacruise
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    portacruise Senior Member

    Comments above. Some good info on Poorquedo posts.
    Hope this helps.

    Porta
     
  6. Motivator-1
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    Motivator-1 Junior Member

    Re-Group

    Hello Porta,
    There has been so much development from my first posts that the information is getting mixed up. My tests 25 years ago with my Pedalcat involved marking floating objects mostly to calculate prop slippage of the Inboard style Propeller that I was using with my Home Built Outdrive, and as a result, gave me some reasonable idea as to how fast I was moving. I also did timed distance measure in 2 directions, for the sake of corrections, to get more real results. You might recall that back then, there were no GPS, and hardly an accurate Loran positioning tool. My tests, though, with my Electricat were done recently when I got my boat back from a lengthy Borrow, so these results are as accurate as anyone's here.

    As I mentioned, I am still willing to consider the new technologies offered here, but something as simple as these large capacity Trolling motors with perhaps the Torqeedo Prop mounted, might perform, I just do not know how well. Your suggestion of using a 12 volt motor and overvolting it might be the answer.

    Since I am planning on building a "Quick & Dirty" Hull & Deck Plug and Fiberglass molds, as I have in the past projects, I want to have the best information before beginning this lengthy project. If Rick's design help can give me nice refined hulls, then the Molds will be beneficial, as I know lots of people that might want to by them to duplicate my efforts. I could have sold my Electricat fishing boat numerous times to passer-bys and to those watching and impressed with my fishing successes from their homes on the water. The boat was a phenominal Inshore Trolling Machine.

    Anyway, I have always tryed to do the KISS system with respect to design, and I'm still hoping to get some of that here.
    John
     
  7. Motivator-1
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    Motivator-1 Junior Member

    Moving over to Poorqeedo

    Hi guys,
    Thanks, Porta for the tip on checking on the Poorqeedo thread. It seems as if there is more discussion about what I am seeking going on over there instead of here on this thread. Jeremy has had a great deal of useful input on motors and controls, and I hope to see more of it. I would like to now start posting there and maybe drop this, otherwise, parallel topic thread as I have suggested in the past and pick it up over there. The Poorqeedo thread is progressing much faster than this one. If anyone disagrees with this please let me know.

    http://www.boatdesign.net/forums/bo...do-another-efficient-electric-boat-33033.html

    I want to sincerely thank everyone that has helped me in the ways that they have in the last few weeks.

    Regards,
    John
     
  8. Motivator-1
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    Motivator-1 Junior Member

    Poorqeedo goes Toorpedo

    Hey everyone...I'm Back,
    No sooner did I bail out on my thread here about Catamaran design, to start to follow the Poorqeedo thread because of where it was going, and then his boat suddenly ended up going to a long Monohull design instead. Granted the efficiency of that design, I'm still persueing my Catamaran, and any suggested Propulsion systems for it. I hope that I havn't lost anyone here, but I liked where the posts were going on Poorqeedo in respect to "Possible" Trolling Motor application, though I am checking out the other concepts previously mentioned in this thread.
    Please come back and help if you have more to offer.
    Regards,
    John
     
  9. mental_boy
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    mental_boy Junior Member

    You can easily measure the rpm of the trolling motors with a RC motor tachometer, available for $20 or so.

    For the trolling motors:

    Volts x amps = watts

    So:

    70 lb Thrust @ 24 volts X 42 Amps = 1000W (1.34hp)
    80 lb Thrust @ 24 volts X 56 Amps = 1344W (1.8hp)
    101 lb Thrust @ 36 volts X 46 Amps = 1656W (2.2hp)

    Rick's most recent calculations in this thread were for 5.4m/s, or 12mph. This speed required 780w on each hull, so 1560 watts for both hulls. If your trolling motor and RC prop are 60% efficient, then you'll draw 2600 watts. If you mess around with more exotic drivetrains and get your motors/props to 70% efficiency you'll draw 2230 watts.

    So at 24v, 12mph:

    2230w will draw 92 amps.
    2600w will draw 108 amps.

    So let's say you need 105 amps to go 12 mph. If you're using regular flooded 105ah batteries you should only discharge them 50% (DOD), meaning they have 52.5 usable amp hours. You'll have more capacity past that, but you want to keep it at 50% to get good life out of the batteries.

    So your run time at 12mph will be:

    2 24v 105ah batteries: 1/2 hour, range = 6 miles
    4 24v 105ah batteries: 1 hour, range = 12 miles
    6 24v 105ah batteries: 1 1/2 hours, range = 18 miles

    etc.

    So let's say you design your boat for 8kts/9.2mph instead of 10.5kts/12 mph. Your power requirements are cut in half, but your speed only goes down 25%.

    Now your run time at 9.2 mph will be:

    2 24v 105ah batteries: 1 hour, range = 9.2 miles
    4 24v 105ah batteries: 2 hours, range = 18.4 miles
    6 24v 105ah batteries: 3 hours, range = 27.6 miles

    The range with more batteries is underestimated here because of Peukert's law.

    So you definitely want to think about how fast and how far you want to go, and how many batteries you want to carry.

    As for propulsion: if I were you, I'd just use the Trolling motors right off the back of the platform. I don't think you'll gain much by trying to incorporate them into the hulls, and you'll lose the tilt up feature for beaching and prop inspection/replacement. You'll also lose cooling which means reduced efficiency. Gang 2 RC props on each motor if you need to (like Rick mentioned) and build a fairing for the shaft like MCdenny. When you settle on a good pitch and diameter you can build your own props if you like.

    To test the suitability of RC props strength wise you can do Rick's load test. 12mph means a 145N load on the prop. So support the prop 25% in from each end and hang 32 pounds of weight from the hub. Measure the flex.

    For 9.2mph just halve the weight (Edit: not 1/2, more like 96N, so 22lb) and measure the flex. Then talk to Rick to see if it is an appropriate amount of flex. I'd also load the prop until it breaks to see what the limit is.

    If the props flex too much just use two for each motor to reduce the loading. Rick mentioned you may also find suitable 3 or 4 bladed props or even folding RC props, but they may not be strong enough.

    For the hull there is no need to make a mold, you can just make the plug out of plywood and use that for testing. Make the mold once you are satisfied with the design.




     
  10. Motivator-1
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    Motivator-1 Junior Member

    Thanks so much Mental, for your valuable input.
    I was taking a time out in order to re-evaluate my entire boat project. One thing that I previously noted was that my hulls will need to support about 500 kg combined, and possibly slighty more if overloaded. Rick's 400kg (JV1) hulls appear much fuller at the ends than the way I drew my hulls, thus giving more bouyancy from less beam. I hope Rick can tweak his hulls to my 500kg requirements, and give me final expected energy requirements. Then I will have to sort out which direction that I will ultimately go with the Propulsion. Also, please remember that my boating purpose is to Troll & Fish at rather slow speeds, but have fast moving capacity when moving or scouting. Rick's figures also show quite good effiency at 5 MPH, which was near full performance on my old boat with a 24 volt motor @ about 25 amps. I can see a very long range for this craft by varying the speed as will likely be the case.

    In the mean time, I investigated Solar Panels, and much to my surprise, you can now buy them at under $2.00 per Watt, and they are getting more efficient. By adding 1 - 215 Watt panel, I might be able to supplement a good deal of energy at the slow speeds, and help increase range considerably. What I do not know is what ineffiencies are associated with losses in these panels, and I'm curious if the panels wattage can be used directly by the motor if it doesn't have to charge the Battery instead if your pulling more amps at the time.

    Rick, Jeremy, Porta....Can you guys elaborate on what has been said so far?

    Best Regards and Thank you,
    John
     
  11. mental_boy
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    mental_boy Junior Member

    Also, if you size your motor and prop for high speed, it won't be as efficient as it could be at lower speeds as with a motor and prop sized for lower speeds. No idea how much less efficient....

    I'm curious, where can you buy a 215w solar panel for $2/w? I thought they were still closer to $3 per watt.

     
  12. portacruise
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    portacruise Senior Member

    Solar comments above.

    Porta
     
  13. Guest625101138

    Guest625101138 Previous Member

    I have updated the comparison with a 6m, 500kg cat. The shape is very close to the earlier JV6 cat.
     

    Attached Files:

  14. Motivator-1
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    Motivator-1 Junior Member

    Hi Porta,
    Thanks for the info. If I put it another way, my curiosity was that if, as you say, the motor draws more than the Solar Panel, there is no electrical efficiency losses, but if the panel charges the battery first and then has to convert it back to the motor, are there losses in each direction of the current flow?

    Mental,
    The site that had the low prices on Solar products was here: http://sunelec.com/
    They have a house brand of Panels that are made for them by Evergreen with out a UL approval, but otherwise the same but cheaper than those sold by Evergreen. Their prices on Charge Controllers, etc. also seem very low.

    Rick,
    Your numbers in the graph have me very excited. At low speeds around 4.5 knots, with whatever inefficiencies are occurring, it would seem that the boat could move along under Solar power alone. Is this true? The weight of the panel that I'm using would only weigh 40 lbs including the charge controller. This could well offset the need for 6 batteries, and use only 4, or possibly a size up in Amp/hour capacity. Did you re-draw the 500kg Hull? If so, you have done the work for me and I'm very close to moving forward. My questions are still about what are the characteristics of the most efficient shape in reference to the Full ends, etc. Also, I am curious about the Wavy Lines your hulls have at the low speeds, instead of the general smooth curve of the others. Once again, thanks for your effort.

    Regards,
    John
     

  15. portacruise
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    portacruise Senior Member

    Hope this helps.

    Porta
     
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