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Thread: The first swamping of Green Bean

  1. #1
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    Default The first swamping of Green Bean

    On my recent Portishead trip I had quite an experience with my canoe that left me thinking that some modification is required if venturing out again in similar conditions where I might use the outboard. I didn't mention it in the blog because I wanted to mention it separately and get some feed-back and ideas.

    It happened not when sailing but when under power using the outboard. I've used the outboard a few times now on my outrigger canoe and have noticed that when under power in choppy waters (by choppy I mean steep waves close together, whether small or larger) my canoe takes on quite a lot of spray and I need to bale out much more often than when under sail.

    However, I sailed up the Severn in some pretty rough water, including some quite large standing waves with large troughs further up river. At no time was the canoe even close to being on it's limit. In fact it felt quite at home and safe under sail. But when I changed from sail to power (as we were finally running out of time to make the lock in) it was a completely different story. In the same conditions the canoe took on huge amounts of water and at one point ( in a matter of seconds) a solid wall of water came over the gunnels (both sides) and filled up the canoe to a level at which it filled up my wellies! The next wave went right over the outboard motor which abruptly stopped. Luckily it started again second pull. We couldn't proceed again until we'd baled out most of the water but we had to continually bale whilst we used the outboard.

    As we had two of us aboard and a load of kit for a weekend away I was pleased that the built in buoyancy was well up to the job. With two outriggers as well there was no way we could sink but it was a bit alarming to say the least.

    I am just amazed at how much less seaworthy the same canoe is with an outboard pushing it along in those conditions. It was probably made worse by the frequency of the waves but even so it is a stark difference from the way it sails. Maybe it's because under power we were head on into the seas whereas sailing into the wind and waves nearly always means we hit them at an angle. I'm not really sure about this to be quite honest but whatever the reason I need to think about a way of preventing it from happening. I did notice that the water does not actually come over the bow, but as the canoe hits the waves they part and somehow it comes up each side and over the gunnels at about the point where the outrigger poles sit across.

    I think I may need to make a couple of triangular spray deflectors out of rubberised canvas so that they fasten to the gunnels and the outrigger poles and taper in to the spray hood at the bow.

    Any ideas??

    Steve

  2. #2
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    We noticed (when sailing admittedly) that the outrigger floats seem to create a narrow channel which seems to concentrate the waves and force them upwards (almost the same way the waves of a Bore get higher as the river they run up narrows), could this be the effect you experienced Steve? As you say hitting the waves head on would probably accentuate the effect.

  3. #3
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    I have water coming over between the nose and the outrigger arm on mine when Im paddling just off straight into chop.

    Disconcerting when a bigger wave swamps the boat. First few times frightened the life out of me.

    Now I just keep paddling and ignore it.

    Have you considered an electric pump?

    We use two 350 gpg pumps connected to a 12 volt 7ah leisure battery on the floor of our sailing dinghy. The battery and switches are in a tupperware style box with the wires sealed into the holes drilled for them to exit.

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    I don't think it's happening due to a narrow channel which seems to concentrate the waves and force them upwards (at least I haven't seen that happening). When I paddle the boat (even with outriggers) into the waves the same does not happen. May be it's the increased speed with the outboard? But I'm not totally sure about that yet either because she sails in a good blow faster than the outboard pushes her along. (the speed advantage with the outboard is that we can go home in a straight line).

    I'm wondering if I ought to clamp the camera in place and video it so I can watch it slowed down. (Wouldn't want to wreck the outboard though as it was momentarily submerged last time under a wave)

    Steve

  5. #5
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    Quote Originally Posted by No Idea View Post
    Have you considered an electric pump?

    We use two 350 gpg pumps connected to a 12 volt 7ah leisure battery on the floor of our sailing dinghy. The battery and switches are in a tupperware style box with the wires sealed into the holes drilled for them to exit.
    Not yet. I'd like to tackle prevention before cure. However, I'm not ruling anything out yet!

    Steve

  6. #6
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    Quote Originally Posted by Steve C View Post
    ... Maybe it's because under power we were head on into the seas whereas.....

    Any ideas??

    Steve
    I suspect you're right and that hammering head-on into the waves is the principal cause - slowing down and heading off by 45 degrees will drop the wave frequency and makes them much less steep.

  7. #7
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    Standard powerboat technique going upwind in steep short seas - go up the wave at an angle, and roll the boat over the top. It's likely it's the steepness of the seas, not the height that's the problem; going at an angle reduces the steepness.

  8. #8
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    Sounds like water displacement to me Steve. As you drive your canoe directly into the waves, the water on each side of the canoe is being compressed by the pointy shape of the canoe and this forces it to rise along the edges of your canoe.

    If your canoe is like mine, the gunwales are closer to the waterline than the bow, thus this rising water suddenly has no canoe left to displace it and just before the centre (Widest point) of your canoe when the pressure is the greatest, it pours in over the gunwales.

    Also, the wave is a raised section of water as as you power through it, the wave will travel down the side of the canoe. If it runs out of freeboard, it will attempt to pour in. Slowing down should allow the buoyancy within your canoe to lift your canoe higher so that less water can come in.

    I am fairly sure that you should try to drive the canoe at an angle to the waves. This will leave you without a problem on the lee side and if you angle the canoe slightly over to the side, it will raise the gunwale on the other side, reducing the risk there too. If you still find water coming in, you need to back off the throttle and reduce the displacement water pressure.

    We were taught something about this on our powerboat course. I'll try and find something about it.

    Here, just found this: http://www.mkboatdesigns.co.uk/displ...t_boats_2.html
    Read the first part about limiting the speed of a displacement boat, which is essentially what you have. Also, if you are driving into waves, your actual speed through the water is higher than if you are sailing at an angle to them! Hope this helps.
    Last edited by Steamerpoint; 1st-October-2012 at 12:17 AM. Reason: Found Useful Link

  9. #9
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    Have a quick look at this video. You will see a number of thin pointy sailing yachts powering along and you can see how water is displaced along the sides of the hull.



    This video is also worth looking at. While in calm water, you can see the first bow type wave being pushed up just forward of the canoe centre. Pushing through waves, this would be much higher.

    Last edited by Steamerpoint; 1st-October-2012 at 12:44 AM.

  10. #10
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    sails also hold a hull onto the water, this can give a diferant ride to a power boat that isent being held in the same way

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    Have you considered a Jetski engine instead of an outboard?

  12. #12
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    Assuming the issue is possibly something to do with wave compression between the hull and outrigger floats (amongst other factors), what about experimenting with motoring hard with one outrigger attached and seeing what difference there is in the bow and stern waves each side? Not sure what you would do if this showed a difference, apart from raising the outrigger float height to reduce this? Alternatively, just experiment with raising the outriggers a little?

  13. #13
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    Quote Originally Posted by unk tantor View Post


    Have you considered a Jetski engine instead of an outboard?
    Lol, so funny.

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    Thanks for that guys, yet more thoughts to consider. I'll do some experimentation and see what happens. Promise to keep you posted.

    Steve

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    Hi Steve,

    Found this picture. I could be wrong, but I feel that it is this displacement bow wave you are experiencing that is swamping your canoe.


  16. #16
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    Looking at Steamerpoint's picture above I wonder if the trim changes when you use the outboard? Do you move towards the stern and reduce the effective waterline length and therefore the max hull speed? Does the outboard tend to pull the stern down as well? Both would give rise to a bigger displacement bow wave. Changing the trim may also create bigger bow waves from the floats. Videos on a flat day would be very informative.

    Graham

  17. #17
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    I'll take some video footage when I get the chance to

  18. #18
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    Steve C,
    I agree with others who have deduced that Green Pea spears oncoming waves due to her fine entry, thus the waves are not displaced laterally, but travel along the sides until encountering the lower gunnels. Being a fellow tri-canoe driver, and having followed your adventures, I might also add that the problem is exascerbated by the relatively heavy weight of Green Pea. I experienced the same issues when I was using an Easy Rider Raven 17 as a tri-canoe. That boat had a fine entry and a semi-V hull. While very fast under paddle or oars, when fitted with a full panoply of pontoons, sails, and kit, it would do the same as Green Pea.

    Your options have been laid out: Take the seas at an angle or slow down. At a lesser speed you will still be able to make a straight course.

    I have modified four canoes for sailing or as tri-canoes. The first was an 18ft Grumman with the Grumman gunter rig complete kit. That kit has been moved to each successive boat, finally coming home to another Grumman canoe. The reason: Grummans don't plunge deeply into oncoming waves due to having a fuller section fwd, with a flat section throughout the bottom run. While this design is considered by many to be rather pedestrian under paddle, it comes alive when coupled with a set of outriggers and a powerful sail setup. It is a remarkable dry ride, even though there is relatively low freeboard. And, a Grumman canoe is still a light boat at 75lbs.

    Hull shape is the difference. What may not be very efficient in one instance is quite so in another. You have a very good boat, and I might suggest some type of spray skirt attached along the gunnels with button snaps. Oilskin canvas would look terrific on that craft.

  19. #19
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    Hello OutnBacker

    Thanks for your thoughts on this issue, it's interesting to read your comments on the experiences with the Grumman canoes. Green Bean (a Selway Fisher Prospector) only seems to have this problem with the outboard running. When under sail she doesn't take on much water at all. However, I agree with you that some sort of spray skirt would make things a lot better and I have been coming to that conclusion and thinking that I will try it out.

    I'll let you know the outcome in due course, but it might be a few weeks until I get the opportunity.

    Thanks again

    Steve

  20. #20
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    I understand that you head straight into the chop under power, but not under sail. I mean't to say that I also do the same, but my phrasing seemed to indicate that I do so under sail. What I was trying to say is that while heading into the chop under power, with full panoply, etc, I experienced the same issues. I should be a better proof reader.

    I'm familiar with the Selway version of the Prospector. Nice boat. Have you ever wished for an 18 or 20 footer in the smae design? I very much regret selling my Grumman 18. Longer canoes are so much nicer to sail - especially in rougher waters. If I ever get the chance at a used Old Town Tripper 20, I'll snap it up.

    My experience with Grumman canoes is largely under human power. Mostly under oars as I much prefer to row. My Grumman experience under sail is largely terrifying, as I only have this huge 65ft gunter rig - and now a jib as well. Building a solid set of outriggers was more out of a feeling of impending death by hypothermia than by the joy of lugging around all that kit. Over the years, I've messed about in various hull types and materials, but I keep coming back to a Grumman. Lots of reasons why. None of them having to do with speed or efficiency, but they do the job.

    Here's a link to some pics and video from around here:
    http://s1125.photobucket.com/albums/...ing%20%202012/
    Last edited by OutnBacker; 10th-October-2012 at 01:22 AM.

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