Row boat, take two

Discussion in 'Wooden Boat Building and Restoration' started by cameron.d.mm, Jul 17, 2014.

  1. cameron.d.mm
    Joined: Mar 2009
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    Location: Ontario, Canada

    cameron.d.mm Junior Member

    NoEyeDeer, please don't feel that I am asking you or anyone else to design me a boat. I've already done that, for better or for worse. However, I am willing to share what I was thinking as I did so (I'll refrain from claiming it has any "strong points").

    I was motivated to achieve a better result than last time (keeping my sights low, perhaps), and was inspired by exposure to a wineglass wherry built by a family member.

    I want the boat to be good for rowing individually, but also capable of holding two comfortably, acknowledging that performance will be compromised with the extra displacement. Occasionally, I use an electric trawling motor to power my other boat, and have a small transom for this purpose (it will require a removable bracket). I would also like the boat to track better than the last one, but still be manoeuvrable. It will be rowed primarily on a small river (the Rideau in Ontario, Canada). Finally, I placed some restrictions on the design. I decided that it had to fit on four sheets of ply, that it would be stitch and glue built, and that I would build it cheaply - acknowledging that it is an experiment, and that I'm trying to pay a mortgage and rent at the same time. Keeping it small and light is also good, because I live a few blocks from the water and use my bicycle to transport the boat.

    To try and meet the goals outlined above, I chose a maximum length of ~15 ft (to fit on two scarfed 4x8' panels after the shapes are flattened out). In an attempt to limit drag I tried to keep the transom out of the water, although I elected to have a narrow portion immersed to help it track straight. I tried to keep the immersed volume narrow at both ends, as it seemed that many boats nice to row are double enders (I had not considered the squatting motion associated with the act of rowing pointed out above). I chose a single chine design to keep the number of panels low, and to help them fit on the plywood sheets better. The single chine limited my options for the shape of the entry, but I like the visual style of plumb bows. I kept the freeboard tall at the bow to try and minimize spray from the narrow front end cutting through wakes instead of floating over them. I played with the beam of the boat (I originally tried to make it much narrower) and the rocker to try and meet my displacement target of ~300 lbs (the boat plus me). Finally, I "followed my eye" as to what pleased me visually.

    Things that I've considered but that are not pictured include what I described in the first post. A large breasthook to keep the front dry and stiffen the boat, the possibility of a lateral seat with sealed storage/buoyancy below it, etc.

    Maybe not how a pro would do it, but I think a fairly honest description of my thinking as I sat at the computer.

    Messabout: Googling "Whitehall" and looking at the images is very pleasant. I'm reminded of the wherry I linked above. It is interesting to know some of the history.
     
  2. NoEyeDeer
    Joined: Jun 2010
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    NoEyeDeer Senior Member

    Ok, cool. Well I'll give you my 2c. I can see a few problems.

    Carrying a passenger is likely to be a bit awkward. To balance the weight out you'll have to have a forward rowing position, and the sheer rapidly gets narrower forward of midships. Rowboats usually try to carry the sheer beam a bit further forward, to give better spread at the second rowing position. You can do this while still keeping a fine entry at the waterline.

    The length makes sense for moderate performance, although a deeper hull with less beam at the waterline would make it move easier. Even if you go down to 30 or 32" at the waterline it will still have plenty of stability (in case you want to).

    Immersing the transom in an attempt to help tracking isn't a good idea. For a start, it wont be very effective. You'll still need a skeg to keep the thing on track, particularly if there is any breeze at all. Second, it will drag (particularly with a passenger). You might as well get the transom well out of the water, so it's only slightly immersed even with a passenger, and use a decent sized skeg for tracking. You can mess around with the size a bit once you have the thing in the water. The idea is to get it pretty well balanced with a breeze on the beam or on the quarter, which is where they tend to misbehave most.

    I wouldn't worry about a flat run for what you have in mind. It's not a planing dinghy, and even planing dinghies don't worry about that as much as they used to (modern ones tend to get most of their lift from the middle sections). I wouldn't worry much about squatting either. It takes awfully hard rowing to get a 16 foot boat to squat, even if they are double-ended. You wont be keeping up that sort of speed for long, even in a faster boat than this one.

    The last thing is the entry. Running the chine horizontally like that will cause turbulence at the chine, because there is far more pressure against the topsides than there is against the bottom. It'd be better IMO to give the chine a bit of sweep forward, with a bit more vee in the bow sections. The forefoot doesn't need to be immersed as deeply as you've drawn it.

    There ya go. Do wotcha like. :)
     
  3. messabout
    Joined: Jan 2006
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    messabout Senior Member

    I agree with No-Eye with regard to the front sections. Raise the fore ward chine some. The depth of the fore foot may very well cause the boat to be twitchy when quartering a wave or boat wake. Some boaters call that action; rooting.

    Too deep a forefoot will also make the boat annoyingly more difficult to turn.
     
  4. cameron.d.mm
    Joined: Mar 2009
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    Location: Ontario, Canada

    cameron.d.mm Junior Member

    Thanks again to both of you. My epoxy and fibreglass tape arrived yesterday, so I've started to scarf the panels. I didn't get time to work on it today - so I've stayed up late and tried to incorporate your hull design suggestions into the computer model. Attached is the result.

    The boat is designed to run much deeper now, and I've tried to sneak a few more inches out of the panels to add to the length. I think I'm managed to incorporate the suggestions regarding the bow. The beam hasn't really changed, but it is moved farther forward, and now the transom is just kissing the water. It was difficult to maintain my desired displacement, and I had to widen my transom to do so.

    Anyway, many thanks. Now I just have to double check the panel developments in CAD and see if it still actually fits on my plywood.
     

    Attached Files:

  5. SukiSolo
    Joined: Dec 2012
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    SukiSolo Senior Member

    May I suggest you have a really good look at boats like the Whitehall and similar, maybe the Thames rowing skiff. Thes craft have been developed over many, many years and the resulting underwater forms are not accidents. They can be very specific, for one particular water area or more general. They all work in their specific environment.

    When you understand some of the thinking and forms being used, then use that as input into your own ideas. Remember the problem was almost the same then as now, the sea has not changed....;)
     
  6. NoEyeDeer
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    NoEyeDeer Senior Member

    I'm afraid you've entirely missed the point, because you have slightly increased the beam at the waterline.

    My suggestion was that a narrower and deeper hull would have less resistance, if that was what you were after. The reason is that it would have less wetted surface, which is one of the major components of resistance at normal rowing speeds. By making the hull slightly wider and deeper you aren't saving any significant amount of wetted surface, therefore you will gain no advantage in terms of resistance. If you want to cut resistance you should start paying attention to how your changes affect the total wetted surface of the boat. This is dead basic for rowboat design. It's why sculls are so narrow. Obviously you don't want to go as crazy as a scull, but generally the better you want it to row, the narrower you make it at the waterline, up to the point where it starts getting too tippy for your personal requirements.


    And it now has an extremely blunt entry. My suggestion was to carry the beam at the sheer at bit further forward, while still keeping a fine entry at the waterline. In other words, you would do this by increasing the flare in the topsides panel forward of the 6' station in your previous drawing, just to give a bit more spread for the second pair of rowlocks.

    This really is getting to the point where a bloke might be inclined to ask how many bad boats you want to build before you take the time to learn why good ones are shaped the way they are. Only you can answer that question.
     
  7. cameron.d.mm
    Joined: Mar 2009
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    cameron.d.mm Junior Member

    NoEyeDeer, your are right, I misunderstood what you meant by sheer. I apologize again for my my lack of familiarity with boating terminology - after some more reading I think I understand better now what you suggested. You suggested I widen the front of the boat at the topsides, but not at the waterline.

    As for the wetted surface you are correct, I've not reduced it. However, it hasn't really gone up either (less than 0.5 ft/q). I feel that I am fighting my design displacement and length. Yes, I deepened the hull under the waterline, but I also pulled the chines up at the bow and stern - so I actually lost a lot of displacement. I had to maintain the beam to meet the 300lb design.
     
  8. NoEyeDeer
    Joined: Jun 2010
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    NoEyeDeer Senior Member

    You pulled the chine up in the middle too. Nobody suggested you do that.

    Seems to me that the main problem here is that you have no real feel for what the result should be like. Existing boats (or the good ones anyway) are pretty finely honed for their specific purpose. Improvements are not easy, and always involve trading of something against something else. To do this you need to thoroughly understand what the trade offs are, and which ones you want, and why you want them.

    Without going bonkers about technicalities, since it seems you don't want to read up on details at the moment, if I had to give a rough suggestion it'd be this:

    Take the second boat you posted. Raise the forefoot so the heel of the stem is just in the water, rather than being 2 inches or so down.

    Make the maximum depth of the chine about the same as it was, but take it back to where the maximum depth of the hull is.

    If you want to get less resistance, take a look at narrowing the beam at the chine a bit, and see how it affects wetted surface.

    If you need a bit more displacement, there would be no harm in giving the run a bit of curvature. It doesn't really need to be that flat.

    Twist the topside panel a bit forward of the 6' mark, to help the spread for your second rowing station.

    Put a skeg on it. Go rowing. After a year of using it and looking at other boats and thinking about stuff, decide what you would change.
     
  9. cameron.d.mm
    Joined: Mar 2009
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    cameron.d.mm Junior Member

    Just thought I'd pop in and mention that I did finally get this thing in the water. Only one quick row so far, but everything seems to be pretty much as expected.

    It definitely needs a skeg when rowing with a passenger in the back, as the front bites hard and the back end floats around. It is better behaved rowing single, but still floaty. The river was super calm this evening, and it will be interesting to try some rougher water, big boat wakes, etc.

    Thanks to everyone who participated in the thread. It was my first time building stitch and glue, and I'll do lots of things differently next time.

    Enjoy the pictures.
     

    Attached Files:

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  10. messabout
    Joined: Jan 2006
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    messabout Senior Member

    Cameron, that boat looks pretty good to me. I like it.

    Examining one of the pix where the boat is moving parallel to the bridge, the boat is not making much fuss in the water. The degree of disturbance depends largely on the speed that you were going. It'll make more waves when you pull hard but so far so good.

    P.S. The sign in the bridge is alright too. Grafitti is everywhere and some of it is suitably philosophic. :)
     
  11. cameron.d.mm
    Joined: Mar 2009
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    cameron.d.mm Junior Member

    Thanks Messabout. I was pretty much drifting past the bridge there, but the boat does start to pull some water behind it at speed - not too much though.

    I was going to put on the skeg this evening, but its raining now. Guess it'll have to wait until tomorrow.

    Cheers.
     
  12. Easy Rider
    Joined: Oct 2009
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    Easy Rider Senior Member

    The orange flat in this design is what fascinates me. Just a little change whereas one can double the displacement and still not have a submerged transom. I really like it.

    But now it's not clear to me what hull of those presented got built and is in post #24?
     

  13. cameron.d.mm
    Joined: Mar 2009
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    Location: Ontario, Canada

    cameron.d.mm Junior Member

    Easy Rider,

    Thanks for the comments. The boat shown in post #24 is built to the plans shown in post #1 (I said to myself, 'Screw it, already printed them').

    I have since added a huge skeg about 30" long, tapering from 1" to 5.5" in a straight line. The boat really needed it, and now it is very pleasant to row. It tracks well and you can lay in the power without worrying about it walking away to the side. Very relaxing.

    I was having a little leak where the axle for the wheels pokes through the stem, and just got it sorted this evening. I took it out for a quick row, and was able to sustain ~8 km/h (4.3 knots) fairly easily. 5-6 km/h is obtained simply by dipping the oars in the water - it comes effortlessly.

    Considering this is a 4 panel wheel-barrel boat, I'm happy with it except build quality. I made several mistakes, mostly by rushing and being cheap on materials. I think I'll row this until it falls apart and then refine the plans a bit and do it again with the lessons I learned from the build. We'll see. I also want to design and built a really fast rowing boat some time.
     
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