designing a fast rowboat

Discussion in 'Boat Design' started by nordvindcrew, Oct 13, 2006.

  1. mike1
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    mike1 Junior Member

    Hi,
    I too fell in love with Sausalito, and have had many sweet dreams about her.
    Sausaltio is featured in the book, Rowable Classics, by Daryl J Strickler, They have a web site.
    Sausalito was designed by Greg Sabourin and Gordy Nash, and built by Mike Lawler from a jig constructed by Sabourin. It is based on a standard wherry of about 1910 rowed on San Francisco . the lines and shape are similar to the wherries built in wood and later fiberglass, by Pocock. ( although the construction is very different),
    Mike Lawler seems to be a restorer and collector and builder ( amongst other things) of lovely wooden boats.
    There are no plans as far as I know, and if anyone is able to unearth any I'd like a copy. even if its a lines only drawing.
     
  2. NoEyeDeer
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    NoEyeDeer Senior Member

    Back when I was thinking about this whole "fastest fixed seat oarlocks-on-gunwales one person" boat thingy I did draw up something to see how far the concept could be pushed.

    Thingy in the pic would eat guideboats for breakfast if the person rowing it was good enough. At 5.5 knots (which would put the crest of the stern wave about a foot behind the sternpost on a 16 foot guideboat) the thingy in the pic should knock a bit over 20% off the total resistance (The Gospel According to Michlet).

    Beam at the sheer is a couple inches more than most guideboats to help with the oarlock spread. This is carried far enough for'd that a for'd rowing station could be used to balance a passenger. There's enough reserve bouynacy to make it good as a solo open boat in some fairly interesting conditions.

    The important bits for drag: Waterline beam is about four inches less than a guideboat. Bottom board is about two inches narrower. Length is a fair bit more (21 feet overall). This is the sort of thing you have to do to get that much reduction in resistance. It would equate to roughly an extra half a knot on the top speed for the same amount of sweating and grunting.

    Of course if you think this is too bonkers and would be happy with a 10% reduction in resistance, then you could look at something that's half as bonkers as a 16 foot guideboat and half as bonkers as this one. Given that guideboats are fairly bonkers to start with, that still wouldn't be a boat for drunken elephants.

    Anyway, point is that this is what I was referring to when I said that if you want to beat guideboats you'll need something more extreme. Hey ho.
     

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  3. dcnblues
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    dcnblues Senior Member

    I agree with everything you just wrote (excellent stuff!) except, to some degree, the last sentence. There's an additional factor that's probably already been discussed in this thread. Forgive me, but I pull useful text from this thread, but also other sources, and throw it all together in one 'note' file for when I'm ready to build my own boat, and I don't have attributes for the following quotes (and I stress I don't take credit for them):

    I'm guessing Paul Neil is unusually fit, and has an unusually capable cardiac pump, and can usually maintain a higher stroke rate than his competitors (or than normal). Which plays nicely into the additional factor that Rick Willoughby made clear early in the thread: keeping boat speed up is much more effective and efficient than letting it slow down critically between oar strokes, and having to re-accelerate the mass to get it up to speed again, then having to do the same thing with each stroke of the oars. That's the primary reason leg-driven hulls will kick an oars-driven boat's *** every time: they get up to speed, and hold it there with relative ease.

    Guideboats also have about the narrowest beam, and therefore shorter oars, but it took a while for me to see that a fit, fast rower, whose stroke rate is higher than a competitor's, isn't letting his boat slow down as much as his competitor's. And that has significantly positive payoff in overall speed.

    These two conflicting forces explain why oars seem so uniform in length to me. Grandma out for a quiet row in a heavy dory, and Paul Neil winning the Blackburn Challenge often will be using oars of exactly the same length. This always struck me as odd, that there wasn't greater extremes between the lowest performance recreational rowing, and Olympic level competition. I consider myself the newbie on this list, but I'm not sure anyone's quiet said it this way yet:

    For the same expenditure of energy, and regardless of ergonomics, longer oars give greater efficiency at slow stroke rates, but that length is limited by faster stroke rates giving even greater efficiencies for competition.

    One last point that hasn't had it's due on this list - A really good ocean oarsman would use the following technique, and most of the time, a shorter oar coming from a narrower beam would likely be an advantage in using it:

    I like the guideboats very much, but their design seems to reward sustained high effort in too competitive a manner for this slow boy. Also, the narrow waterline would be a core / torso workout to keep the boat balanced, and for me, that detracts from fun. But I'm glad I read this thread, and understand so much more than I did when I came to it. Thanks again to all the pros who've contributed.
     
  4. NoEyeDeer
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    NoEyeDeer Senior Member

    Well, when I said "it's what's in the water that counts" I was talking about resistance. Oarlock spread is a separate issue IMO. Guideboats seem to usually use oars around 7 1/2 feet long, which is pretty normal for a fixed seat boat. Correct gearing is achieved by stuffing your hands into the opposite armpits. I have my doubts as to the efficiency of this. IOW, I suspect a guideboat with its oarlocks on outriggers to give optimum spread would be faster.

    My understanding is that Paul Neil is a triathlete and is disgustingly fit. A higher stroke rate would be better for keeping the boat speed closer to the average, but you have to trade that off against the extra energy required to move your body and the oars backwards and forwards at the higher rate. F=ma. Up the stroke rate by ten percent and you have to apply ten percent more force just to move your torso and the oar handles, even before you start putting any load on the blades.

    I'd dispute this: "For the same expenditure of energy, and regardless of ergonomics, longer oars give greater efficiency at slow stroke rates,"

    What I've found is that if you have a very easily driven boat (ie: sorta guideboatish, not Whitehallish) then when you are just cruising around looking at the wildlife and trying to avoid running into rocks, the resistance is so low that it pretty much wouldn't matter if the oars were ten miles long. You can pull any gearing with only a couple of fingers wrapped around the handle. This gives a lovely amount of whoosh per grunt and feels awesomely groovy. It may not technically be the most efficient way to travel at that particular average speed, but you wont care because it's easy and it feels good.

    High gearing doesn't work so well when you try to sprint, because the resistance increases so rapidly at high speeds that the load on the handles get silly, and you'll go faster with an easier pull at a higher rate. As an analogy, it's rather like trying to ride a bicycle up a hill in top gear. You're better off shifting down a few.

    ETA: IMHO, whoosh per grunt is what rowing is all about. Most salubrious, old chap. Feels much nicer than playing twiddlesticks and getting dripped on.
     
  5. sailing canoe
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    sailing canoe Junior Member

    I previous to this response typed in 2 replies which got lost when I looked for a moment else where. Does anyone else have this problem?
    But in between then I got a response back from Greg Sabourin.
    I had asked him if it was the "Petaluma" that Simon Watts sells the plans for. Dempsey's is a Petaluma Brew pub. The Aero and 24 are Maas open water boats.
    Greg's response

    Not the Simon Watts boat, which I lofted for Simon years ago, after taking the lines off my boat now hanging in Dempsey's. The boat in the picture is a wherry design of mine, 22' X18" width waterline, basically similar to an aero, although with a straighter keel giving it more run closer to a 24. I lofted the boat, lines taken from an old, nameless wherry, which was so hogged that I basically started over. I built molds, planking and stem patterns and jigs, and built two of them, one a hard-decked model now rowed by a gentleman in Sausalito, the other, a fabric decked model (like many wooden shells) which was in Austin years ago. I sold all the lofting, molds, patterns, etc. and they ended up in the hands of the guy whose boat you sent a photo of. He's left it undecked and gone to a laminated rigger, which I like quite a bit. Where did you pick up the photo from?
     
  6. mike1
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    mike1 Junior Member

    Hi Sailing Canoe,
    Greg Sabourin's comments are interesting,
    I wonder if Mike Lawless still has the lofting details , or Patterns , or any written info he would care to share?
    Sausalito is certainly an interesting boat, and according to the write up in the "Rowable Classics" has a reasonable turn of speed.
    Mike
     
  7. NoEyeDeer
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    NoEyeDeer Senior Member

    I've been thinking about outriggers a bit. I'm not terribly keen on the whole oarlocks-on-gunwales thing. I know that some people view it as the mark of a "real rowboat", but even for fixed seat I'm not sure it's a good thing if you want a really fast boat.

    Thing is that personally I like to have the oars for a fixed seat boat set up so that the handles just clear on the pull. I find this is much more natural for general use. You can do course corrections easily without worrying about getting things crossed up, which is handy when looking around to pick waves and you need to haul the boat around a bit in a hurry. You can spin the boat easily in tight quarters. Both arms have exactly the same positioning and tension on them, so it feels balanced, etc etc.

    To get this setup with reasonable gearing and oar length, you end up with the oarlocks spaced about four feet apart. If you want them on the gunwales, and you want a fast boat, then the midship section gets quite ridiculous in shape because you have to flare the topsides around thirteen inches in about eight or nine inches of freeboard (assuming BWL is around 22", which is about right). This is not good for weight or stiffness or for handling in wind/waves, and it looks a bit odd too.

    Seems to me that the sensible option is to just make the boat a natural shape and use outriggers to get the oarlocks where you want them. My old boat from years ago was set up like this (with fixed riggers) and I never found the outriggers were much of a problem, even when coming alongside. Since they were quite a bit narrower than riggers for a sliding seat I could still reach past them quite easily and fend off if necessary. Getting in and out of the boat wasn't a problem for me either.

    Another thing riggers have in their favour is that the boat is easier to pick up. Not only do you save a bit of weight, but you only have to lift one gunwale to around your waist to get the other one off the ground. This is more convenient than trying to carry a wider boat by yourself, when you have to haul the gunwale up to your chest or sling it over your shoulder.

    Best of all would be folding riggers, but all the ones I've seen fold up and over towards the centreline. To my mind this is a nuisance, because you have to get the oar out of the oarlock before folding the riggers, and if they have any width they'll drop on your legs and get all tangled up when you fold them. They'll also get in the way if you want to move forwards or aft in the boat with the riggers retracted.

    So I had a brainwave. Build the riggers so they swing around a vertical axis located each side of the footrest (ie: footrest and riggers are built as a drop in unit). When extended, they can be held in place wth a pin on the gunwale, or a strut or whatever. When it comes time to retract the riggers you unpin them and simply pull forwards on the rigger, which makes it swing inside the boat but outside of the space you want for yourself. The oar can even stay in the oarlock while you do this. A setup like this would make coming alongside really easy.

    There's another bonus though. I did a bit of sketching and rough measuring for this a while back, and it seems that by placing the pivot correctly you can arrange the arc of the arms so that the same riggers will work for either a fixed seat (with riggers swung for'd and inwards to around 48" beam) and still work for a sliding seat (with riggers swung aft and out to a 63" beam). The fore and aft positioning can be made correct in both instances without having to do outrageous things with pivot placement and arm length. All that is needed are two pin locations and oars to suit.

    Someone must have thought of this somewhere before, but I've never heard of anyone doing it. I cannot see why it wouldn't be feasible.
     
  8. mike1
    Joined: May 2004
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    mike1 Junior Member

    Hi NoEyeDeer,
    Here in Cape Town we have a local boat builder who builds a 5 m sliding seat boat with a very similar setup for his riggers.
    50mm ally tubing come vertically up from the inner skin and is bent outwards, to hold the riggers at the correct distance, these arms are held in place with a simple pin, after rowing they are swung back again towards the center line . the oars can remain in place.
    This system is the same as discribed by you.
    One of our club members has one , keeps it in the club boats shed, and this system certainly helps with storage and with transport.
    I think that there are huge merits using this idea.
    mike
     
  9. NoEyeDeer
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    NoEyeDeer Senior Member

    Cool. Figures somebody would have tried it before. Got any pictures?

    Oh and this sort of thing would be good for Clinton. He has a bee in his bonnet about a really fast boat that would suit fixed seat or sliding. Riggers like this are the ideal way to tackle that IMHO.
     
  10. ancient kayaker
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    ancient kayaker aka Terry Haines

    Folding outriggers make a lot of sense. If fixed outriggers are a problem when coming alongside, then a hull that goes from a narrow waterline beam to a much wider beam at the sheer, just to provide a convenient place for the oarlocks, is not going to be much better - it’s still a long way to jump from the centerline and the stability isn't there to allow you to step on the gunnel.
     
  11. DickT
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    DickT Junior Member

    Several years back I made a combination outrigger stretcher out of rectangular aluminum tubing that would bolt and unbolt quickly to the gunwales of a 17' canoe I used for rowing. It was awkward looking but worked very well. I got the spread of the locks, lock to stretcher, and butt placement for CG dialed in just right. It was very stiff and didn't allow any flex between the balls of my feet and the locks. It was a great learning experience, but when I built my present boat I really wanted the locks on the gunwales and am happy with 9' oars with 24" inner looms on a 42" spread.
     
  12. NoEyeDeer
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    NoEyeDeer Senior Member

    Jesus. I used to row with 8 foot oars with 25" inner and that was high gearing. Too high for best efficiency at times, and that in a very easily driven boat. 24" inner on a 9 foot oar is over the top IMO, unless you are only ever going slowly in good conditions.

    Btw, I'd still regard 42" as too much beam at the sheer, bearing in mind that my defnition of "fast rowboat" means "waterline beam less than 22". Obviously this is personal reference.

    Regarding overlap, I realise that with a sliding seat you do need to overlap the handles to some extent. Because it's normal to use around 36" inner looms with a sliding seat, if the handles don't overlap at mid stroke they end up way too far outboard at the beginning and end of the stroke (basic trig for you there). This is not good for comfort or efficiency.

    Fixed seat doesn't have that problem because the shorter looms mean that the handles don't move so far outboard for the same angle of sweep, so you can get away with not having them crossed at mid stroke.
     
  13. KJL38
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    KJL38 Junior Member

    I find there is no torso workout from balancing a guideboat, they are quite stable while seated and if you do lean it the stability rises rapidly. I don't think I expend any effort at all into maintaining balance.

    The only time I've ever tipped it was when taking a friend out, he decided to push off while leaning out as far as he could reach.
     
  14. DickT
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    DickT Junior Member

    It works! haven't gotten in the water yet this year mainly because I tore mcls and acls in both knees, but last summer I did a 3 mile course on Lake Champlain in 33:09. I can maintain 3.5-4mph upwind and 4.5-5.5 downwind for a reasonable 1 hour row. My lwl is 16' and wl beam is about 30". Boat and me displace about 300lbs.
     

  15. DickT
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    DickT Junior Member

    Boat and Oar

    Got the boat down from the rafters in the garage today and realized I'd said 42" oarlock spread when in fact the beam is 42 and spread is 45. In any case here is a pic looking forward. As you can see it needs finish work.
     

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