Electric Boat Design

Discussion in 'Boat Design' started by John Klimek, Nov 27, 2001.

  1. John Klimek
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    John Klimek Junior Member

    I am intrested in displacement hulls for use with electric motors. I have been playing with multi hull designs for a four person fishing boat for use on restricted reserviors. I like the multi hull approach because I believe it will be most efficient for a boat that must be must be between 14 ft and 18 ft overall in length very stable and relativley wide ( ~ 8ft). I am looking at a RAY electric outboard motor that can produce ~ 195 lbs thrust max (4 hp) and 1.5 hp at typical medium speed. Eight batteries and motor weigh 670 lbs.

    My goal is to get the most efficient hull design for this application to get the most range out of the battery power. I have look at "pontoon boats" but I don't think they are all that well designed, they are basically pointed clynders on one end only. Aluminum bass boat have a lot of neat features but are all planning hulls which are even less efficient than pontoon boats at the slow speeds. I have the Michlet 6.06 software (no longer available) from Leo Lazauskas which generates some intresting tri hull designs making use of wave cancelation to increase efficiency. Does anyone know of any boat manufacters that make a boat I am looking for? I having some fun running some hull designs but it is a long way to get from the hull designs on the computer to getting out on the water and fishing.
     
  2. Stephen Ditmore
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    Stephen Ditmore Senior Member

  3. Stephen Ditmore
    Joined: Jun 2001
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    Stephen Ditmore Senior Member

  4. Guest

    Guest Guest

    Tip for electric engine

    You could also use an engine called "Ozecodrive"
    Here is a link to their current website:
    www.ozecodrive.com
    Unfortunately only in english but you can contact them on email:
    mailto:OZ@autocontrol.se

    The basics are as follows:
    4 kW engine from zero to full power in 2 secs.
    Full reverse to full speed ahead 4 secs.
    Could be compared powerwise to a Honda 7.5 hp fourstroke.

    Nice construction beautiful engine but a bit on the expensive side.
    This is what an engine installation looks like:
    http://www.ozecodrive.com/pages/axel.htm

    Good luck

    Erik
     
  5. Stephen Ditmore
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    Stephen Ditmore Senior Member

  6. Stephen Ditmore
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    Stephen Ditmore Senior Member

    Some other web sites that might be of interest:

    http://www.brooks36.fsnet.co.uk/main.htm
    http://www.plasticpontoon.com/
    http://www.wing.com/
    http://www.wing.com/pic4.html

    I own a Catapult catamaran. If you're planning on having more than one person aboard you probably would want hulls with more volume. My thought is you could do something similar but larger. Plasticpontoon.com offers a plastic bow and wing.com makes custom tubes. Perhaps you could do something longer than 18' that could be broken down.
     
  7. John Klimek
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    John Klimek Junior Member

    Thanks for the replies. I have been searching the web recently for pontoons with a point on both ends. I have looked at the inflatable one and two man rowing cats. The pontoons on these boats is the shape I'm looking for. Another restriction for the reservior boats is that inflatables are NOT allowed. I'm suprised that there are no boats (with the exception of three manufacturers that I found) that are designed for low power motors. All the fresh water reserviors here (Maryland) have the no gas restriction and the lakes in Pennsylvania have a less than 10 hp restriction. I guess most people in our gas hungry go fast society do not think of low power efficient designs.

    I have further developed the boat design I have been working on; 17.5 ft LOA, 7.5ft wide tri hull. The center hull carries the 8 batteries, the two outer hulls I am designing to swing inwards so trailering width is less than 6ft wide. Currently the three hulls displace 1900 lbs and should be capable of 6.2 Knots (calm water no wind resistance) with a 4 hp electric, 5.4 Knots @ 2 hp.

    Now my question is if I were to make the hulls (pontoons ,amas) with cedar strips, is it an acceptable fabrication process to have internal frames and fiberglass only the outside? The kayak book I have seems to say that there is a problem of the wood spliting and causing leaks if the boat is taken in and out of the water often. I do not have the space in my home to do the fiberglassing so my thought was to take the hulls to a fiberglassing shop and have them do it. Has anyone have information on building pontoons (length 16ft, max width 13 inches). Are there boat shops able to make custom aluminum hulls?
     
  8. John Klimek
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    John Klimek Junior Member

    After looking at some of the other threads, if I could find a catamaran like the one at http://www.prestige-boats.co.za/catamarans.htm , model prestige cat 475 or 550 only in a rigid hull (remember restriction no inflatables), I would be happy:)
     
  9. Jeff
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    Jeff Moderator

    I'm curious. What do you think the reasoning is behind this?
     
  10. John Klimek
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    John Klimek Junior Member

    Jeff,
    These reserviors are the drinking water supply for Baltimore and Washington D.C. They do not want people in the water at all, no swimming, no wading. They do not allow kayaks either. The reason? I guess they are paranoid about diseases being spred through the water suppy.
     
  11. Jeff
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    Jeff Moderator

    OK that makes sense. I was curious if it was about preventing (any) contact with the water (I didn’t realize it was that sensitive) or if inflatables were classed as 'nuisance-recreational' like jet skis are here or if it was based on more family/children users of particular types of boats or if I might be missing something. (I was going to ask about kayaks and then canoes too :) )
     
  12. John Klimek
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    John Klimek Junior Member

    Still looking for some constrution technique suggestions. I have attached an image of the design work in progress. What is shown is one of the hull configurations I am concidering. Only the underwater portion of the hulls is shown. The resistance of the hulls is calculated and optimized for speeds in the range of 5.25 to 7.25 mph with an overall displacement of 1900lbs. Total resistance includes viscous drag components and wave resistance components. Hull form and placement is also opimimized for wave cancellation at the speeds mentioned previously. The center hull is approx. 22 inches wide at max beam; the outer hulls 13 inches.
     

    Attached Files:

  13. Stephen Ditmore
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    Stephen Ditmore Senior Member

    These aren't criticisms -- in several respects I think you might be on the right track. But I find a few things a little surprising about your design.

    One is the flat bottoms - multihull designers tend to use semicircular sections for low whetted surface. Also, most who emphasize performance feel it's important that the ratio of length to beam (of individual hulls) be at least 10, and as close to 16 as possible.

    Also, most trimarans carry 75-100% of their displacement with the center hull (at rest).

    And I'm not sure which end of your boat is the bow. Current thinking for displacement hulls in general is that the LCB wants to be at 53.0-53.7% of DWL for lowest resistance near FR=0.4
    Designers of sailing tris put the bouyancy in the pontoons (or "amas") forward of the main hull's LCB to counter the rig (and waves from a quartering sea) pressing the bows down in extreme
    conditions.

    I think having something of a double volume fore-and-aft may be an element of next generation semi-displacement thinking, so I'm not disparaging your effort is this respect

    Good Luck!
     
  14. Stephen Ditmore
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    Stephen Ditmore Senior Member

    I'll also note that, while you may want to employ a fine stern, my recommendation would be at least a small transom.
     

  15. John Klimek
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    John Klimek Junior Member

    The bow in the image is pointing down in waterlines view, to the left if the profile view. The center hull is the top hull in the profile view. The flat bottoms.. I arbitrarily picked a maximum draft of nine inches, I'm not sure how deep I should allow the hull to go. Again this is a calm water (reservoir) fishing boat. The other constraint I put on the hulls is that it must fit in my basement and allow me to get them out without remodeling. After measuring the stairs and the clearances, I determined that I had better not go over 16 ft for any given hull. Maximum length over the craft must be less than 18 ft. The center hull must also be of a sufficient dimension to hold the 8 batteries (12 X 7.75 inches each). The amas.. I figured that it would be better to have a large portion of the displacement in the amas to make the deck area as stable as possible (landing fish). I should note that the program I am using considers many hull forms and positioning to optimize for the least Total resistance. The non-traditional shapes come about because wave cancellation (at 3 design speeds) is considered. Thanks for your inputs, keep them coming.

    I am considering increasing the draft , any suggestions? If I let the program run with only the maximum length and overall displacement, I get three 18ft very slim hulls. It seems that the program will always use a hull that goes to the maximum draft to make the hulls as narrow as possible. I have let the draft go to 15 inches, the results were the hulls went to that maximum. The center hull was no longer wide enough to hold the eight batteries.
    I am also wondering what is a good freeboard dimension.

    Again I appreciate the comments. I would like to here more.
     
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