European river freighter design

Discussion in 'Boat Design' started by Quietboats, Aug 27, 2007.

  1. Quietboats
    Joined: Feb 2004
    Posts: 32
    Likes: 1, Points: 0, Legacy Rep: 20
    Location: Marshallberg, North Carolina

    Quietboats Junior Member

    Hello,
    While on a river cruise through Holland recently, I was amazed how little wake the river freighters threw off. These boats were around 200-300' and at 15 knots had almost no perceptible wake--the water piled up at the bow quite a bit and then just flattened out. As an electric boat builder working on a designing a small passenger water taxi for use in narrow canals I thought I should look a little further into these hull shapes but so far I haven't been able to come up with any info or even find a model of these boats. Any ideas of where to look? ALso, I assume no wake means very efficient also, am I thinking right? By the way, any wake shown in the photo of the boat leaving came off the boat we were traveling on--not the freighter. Any help or comments would be much appreciated. Thanks much.

    Just for fun, I've attached three photos of our current taxi design--capacity six adults plus driver.
     

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    Last edited: Aug 27, 2007
  2. Pericles
    Joined: Sep 2006
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    Location: Heights of High Wycombe, not far from River Thames

    Pericles Senior Member

  3. messabout
    Joined: Jan 2006
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    Location: Lakeland Fl USA

    messabout Senior Member

    The boats that you describe, 200-300 feet at 15 kn, are at a speed length ratio of one or less. Most boats will make very little wake at those speeds. Increase the speed to 20 or 22 Kn and it will throw a big wake.

    Your water taxi...I would guess a waterline length of maybe 25 feet....would also make very little wake at S/L =1 . That would give you a no wake speed of 5 Kn. That will no doubt be a low drain speed for the batteries. Go faster, expect more wake.

    The taxi is a good looking boat.
     
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  4. Quietboats
    Joined: Feb 2004
    Posts: 32
    Likes: 1, Points: 0, Legacy Rep: 20
    Location: Marshallberg, North Carolina

    Quietboats Junior Member

    Thanks for the replies. Pericles, yes I know those boats well.

    Messabout, thanks for the info. I admit I should have hit the books on this before asking questions--I have a tendency to want to look at pictures rather than read the text, ohhh the lingering effects of reading Playboy at a young age. I was really hoping to find either line drawings or a model of a river freighter so I could get a better feel for their basic underwater shape. I have to think that the extreme rounded bow hull of the freighters has a substantial effect on the wake thrown off as our cruise ship was the same length or longer with a very fine entry at the waterline and it produced much more wake. This was my first opportunity to see such a hull shape in action and I maybe was rash to assume they were designed specifically for low wake to minimize shore erosion on the narrow canals and rivers, rather than something like load capacity.

    An electric boat has to be two things—quiet and efficient. My first 15’ design (photos attached) has a slightly bulbous entry at the waterline which worked well for efficiency but the hull produces a ripping sound at low speed as the water gets pushed away from the bow. Some similar sized boats built by Electricraft (Syracuse NY) in the 1930's had a hollow entry and are quieter through the water at the same speed (of course I’m talking water noise and not motor noise here). So when I went to design the 18’ water taxi’s I put a slight hollow in the water line with good results. Then I observe the freighters and see how little wake they produce and get to wondering if I have been going about this backwards the whole time assuming, maybe mistakenly, that no wake means no wasted energy. The wake produced by our boats wasn’t much concern in the past but in the narrow canals the new taxi’s are operating it would be best to minimize as much as possible. So now I’ve pulled out my underutilized “Principles of Naval Architecture “ books and might learn something I should have known years ago...of course there are aesthetic concerns which have to be factored in as well so maybe this all ends up as just an exercise. Any gentle nudging or other comments greatly appreciated. Thanks much.
     

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