designing a fast rowboat

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

  1. Ben Booth
    Joined: Jul 2014
    Posts: 10
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Westport, MA

    Ben Booth Junior Member

    jumping in

    Greetings all. John Aborn told me about this forum about a month ago. Wow...many years of design discussion here! I designed and built a boat this past January that is right up this forum's alley - a fast fixed seat rowboat. I call it the Westport Racing Skiff and designed it for New England's open water racing circuit. We've put in some decent times at the Snow Row, Essex River Race, and the Buzzards Bay open Water Challenge. I'll be at the Blackburn Challenge this Saturday, so if any of the illuminaries of this thread will be there please say hi!

    Here's a picture (early pic - doesn't show splash guard). She's a "blank slate" idea where I tried out a bunch of different concepts. Will post particulars if folks are interested.
    racing skiff2.jpg
     
  2. Tallman
    Joined: Jun 2011
    Posts: 31
    Likes: 0, Points: 6, Legacy Rep: 10
    Location: Los Angeles

    Tallman Junior Member

    Yes, please post pics, specs and build details!
    Design seems to have some of the Euro coastal rowing/racing shape -- is that right? How does it handle waves?
     
  3. Jon A
    Joined: Jun 2013
    Posts: 25
    Likes: 1, Points: 0, Legacy Rep: 13
    Location: Bourne, Ma

    Jon A Junior Member

    Watch the results of the Blackburn. This boat is fast and Ben is a very good rower. With decent weather the course record for fixed seat single (held by a Guideboat) could fall. He has taken the category to a whole new level.

    Jon
     
  4. Ben Booth
    Joined: Jul 2014
    Posts: 10
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Westport, MA

    Ben Booth Junior Member

    Thanks for the vote of confidence Jon!

    Tallman and all - I'll post build, detailed specs, handling, etc after this weekend's race.
    Basic specs:
    length: 18'
    beam: 39"
    oarlock spread: 41" (8'oars)
    weight: 55lbs

    in the interim, here's a couple more photos. (apologies for the "on trailer" shots!)
     

    Attached Files:

  5. petersont
    Joined: Dec 2010
    Posts: 6
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: new york city

    petersont Junior Member

    congrats

    on your win on Saturday-
    and on your beautiful boat, which I saw all too briefly as you sliced by heading out the Annisquam...
    love to hear more about it and the race, especially details about what I assume was a match race for at least part of the course with the 2nd place guideboat, finishing 5 minutes behind.

    All ears-

    cheers
     
  6. Ben Booth
    Joined: Jul 2014
    Posts: 10
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Westport, MA

    Ben Booth Junior Member

    Thanks on the congrats.

    On the Blackburn:
    As known it was a calm day for a fast race. It was a blazing start with the Westport Racing Skiff and two Guideboats. One Guideboat busted an oar maybe two miles into it, leaving myself and one more Guideboat opening up on the field. I was amazed at the intensity of the start, thinking, shoot, over 17 more miles to go!

    I was able to spread it out a bit coming out of the river and kept on it all the way around. The guideboat rower is a phenomenal athlete and oarsman, so I think I had a higher top end speed in my boat to thank for at least some of those 5 minutes! And since this is a design thread, let me share some thoughts on that top end speed...

    I designed this specifically as a fixed-seat oar on gunwale boat for the Blackburn Challenge. I kept my criteria pure: under the limitations of that category, go fast. No concern with passengers, carrying capacity, etc.

    Ideas (opinions) incorporated:

    Reverse sheer: decks are better than high sides. Keep the oarlocks high enough to clear waves, get rid of the rest of the windage.

    Narrow: I firmly believe in fixed-seat performance rowing in open water a high stroke rate is the go-fast option. Look at surski vs sliding seat racing shells results in the Blackburn - the windmills are beating the 9' full body oars, in shorter and wider boats too. 39" is plenty for oar on gunwale.

    Full ends. No hollow bow or stern. Fuller run aft. Small U-shaped transom.

    Circles are fast. Underwater, sections are almost pure circles. The boat is really a super simple shape with an easy run bow to stern. No flat spots, chines , etc.

    Rocker- just over 2" as I think ocean boats handle better and therefor go faster with some rocker, particularly surfing.

    Construction: Cold molded. 2 layers 1/16" okoume plywood. 4oz glass inside and out, just about starved of epoxy. Structural members include only the deck and one frame put in afterwards to stiffen the sheer at the oarlocks (I noticed I was flexing the hull a lot each stroke before this frame installed).

    So that's the gist of what I was thinking when I built this boat!

    Great to see a good-sized fixed seat class at the Blackburn, and great to see over 100 pages of people talking about this stuff!!!
     
  7. NoEyeDeer
    Joined: Jun 2010
    Posts: 983
    Likes: 32, Points: 28, Legacy Rep: 300
    Location: Australia

    NoEyeDeer Senior Member

    Seems logical, for what it is. Should definitely have less resistance than a guideboat at high speeds. How evenly matched were the crews, and what sort of guideboat was it?
     
  8. Tallman
    Joined: Jun 2011
    Posts: 31
    Likes: 0, Points: 6, Legacy Rep: 10
    Location: Los Angeles

    Tallman Junior Member

    Thanks for the details!
    Please excuse the additional questions. Did you design this seat of the pants, or with software? Also, it doesn't look like there's a fin -- was that a problem?
    You went with a transom versus a double-ender. Does the transom bottom ever dip into the water and create some stern drag?
    The higher stroke rate idea is interesting -- do you know what your spm was on average?
    I've just finished a double (will post pics later) that has some of the drawbacks you eliminated so I'm doubly curious.
     
  9. Jon A
    Joined: Jun 2013
    Posts: 25
    Likes: 1, Points: 0, Legacy Rep: 13
    Location: Bourne, Ma

    Jon A Junior Member

    The guideboat that Ben beat was designed (I believe) and built by Pat Brown. I think it is kevlar. It is long for a guideboat, 17' and light. The rower, Gerhardt Munger held the course record until last Saturday. These guys are veterans of the 90 mile races in the Adriondacks, pretty serious stuff.

    Jon
     
  10. NoEyeDeer
    Joined: Jun 2010
    Posts: 983
    Likes: 32, Points: 28, Legacy Rep: 300
    Location: Australia

    NoEyeDeer Senior Member

    Interesting. So the other oarsman was probably a bit better, if anything, which implies the new boat is significantly better.

    Time around the course was 3:12 and a tiny bit. Call it 192 minutes. Second boat comes in at 197. Resistance will be varying at close to V2.2, which means power required varies as approximately V3.2. Assuming equal power available, resistance of the new boat would be 92% of the guideboat.

    That seems quite plausible, just taking a look at the pix of the new one and the dimensions, and comparing that with what is known of guideboats. If the other oarsman was a bit better, meaning more power available for the guideboat, obviously the resistance of the new one would be even less to maintain the same time difference. Would be interesting the run the lines of both through Michlet and see what it says.
     
  11. Ben Booth
    Joined: Jul 2014
    Posts: 10
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Westport, MA

    Ben Booth Junior Member

    The Guideboat in question is indeed a Pat Brown. Its not kevlar though, just a nice light strip built layup. Its only about 37" wide and looks trimmed down overall.

    On Tallman's questions (thanks for asking!):

    I don't use software to design. I rely on intuition and many years of rowing lots of different boats! I draw the boat full-sized on plywood sheets, starting with a desired waterline shape, rocker profile, and max beam to get a series of major bearings.

    No fin, no problem. The boat feels responsive and way shorter than 18 feet in handling, while tracking well enough so as I've never had a problem.

    Transom: I'll talk about this at length because this flies in the face of what has been said, and was a big gamble I took when working up the design. The transom is actually submerged. Its about 2 inches wide at the waterline and sits 1.5" deep. So not a big fat transom. 6" wide max at sheer. In flat water at moderate speeds there is definitely added turbulence and the negative factors that were discussed in this thread. In waves and high speeds it shines. It's buoyancy keeps it from submerging far (in my fine ended wherry the stern plummets going over waves, throwing a big ol wake and causing the bow to pound), which I noticed keeps her speed on. No pounding at all, this boat is super smooth into waves. Downwind the transom picks up the boat and surfs like a California longboard - fast, quiet, controlled, and with enough speed to stay with the wave for a long, long time. At high speeds the turbulence goes away and the wake becomes this beautiful clean line ripping off the stern. No stern squat, it doesn't dig a big hole in the water, and creates very little wave overall off the hull. In the world of compromises, I think the added turbulence of the transom is well negated in these other areas, making the boat in practice faster in her open water environment than a theoretically more efficient double ended shape.

    Stroke Rate: I keep at least mid 30's per minute over 20 miles. Faster spm in shorter races. It's a light pull, so puts you into lungs and heart conditioning and not sheer muscular strength.
     
  12. Ben Booth
    Joined: Jul 2014
    Posts: 10
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Westport, MA

    Ben Booth Junior Member

    correction

    The transom is 4" wide at the water. In my haste, I wrote down the half breadth. Apologies. All other comments and specs remain!
     
  13. NoEyeDeer
    Joined: Jun 2010
    Posts: 983
    Likes: 32, Points: 28, Legacy Rep: 300
    Location: Australia

    NoEyeDeer Senior Member

    Thinking about that transom: surf skis have a similar hull shape overall (basically semi-circular sections, similar amount of rocker, and very little freeboard) but don't have transoms. It doesn't seem to stop them surfing well, nor do they squat noticeably (or not AFAICT).

    How sure are you that the comparison with your wherry is completely valid? What I mean is that if your wherry is fairly normal, it will have a lot more reserve buoyancy in the bow. This will tend to buck the bow up more into waves, if the waves are of any size and you are moving fast. Seems to me that to get a really good idea of what the transom does or doesn't do, you would have to try it against a hull that shared all the other characteristics of your current boat, except for the transom.
     
  14. mungoman
    Joined: Jul 2014
    Posts: 2
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: new york

    mungoman New Member

    Still love my guideboat

    I do not build boats but I can row them. Have been following this post and would like to share a second place take on this years Blackburn Challenge. After checking out Ben's boat, his rowing profile and the fast times he recorded on the shorter races this year, I tried to prepare my guideboat and myself for a tough race. On the river the first three boats were closely grouped until the first place boat who was rowing a little too hard got in the shallows and snapped his oar. Ben was now in the lead by a few boat lengths and was rowing with disipline and slowly increasing his lead. The north shore was flat and the pace was fast. By mile 6 I new we would be setting a new resord unless we hit a headwind on the long south side. I was hoping for a 8 to 10 mph wind staight up from the south putting a chop on top of some decent shore bound rollers. Ben had told me his boat could handle such but I felt my craft held an advantage in that setting. Most of you have seen the Paul Neil photo. There was virtually no wind and I have have seen bigger waves in a swimming pool. I stayed hard on the oars to the finish, hoping that Ben would fade but ultimately had to settle for an unaccustomed second place. Ben built a faster boat and rowed like pro. My congrat's to him. I would like to point out that the year I set what was the old record, I was new to this sport and was rowing a slower boat but had ideal weather/water conditions. We can still go faster. Maybe next year. FYI Pat Brown builds the fastest guideboats no matter what others put on their websites. Check out the race records. Guideboat_competiteurs.jpg This photo and the other that is attached show why I love a guideboat. 6 miles of carry in the 90 miler
     

    Attached Files:


  15. NoEyeDeer
    Joined: Jun 2010
    Posts: 983
    Likes: 32, Points: 28, Legacy Rep: 300
    Location: Australia

    NoEyeDeer Senior Member

    If you want to try something faster and easier to carry, without moving away from a wooden guideboat, have you considered trying to get one built out of paulownia (kiri)? It has been done over here, as well as being used for boats other than guideboats and for surfboards.

    Glass layups the same as used for WRC strippers seem to be fine, but paulownia is around 300 kg/m3 as opposed to WRC at 400. That should save a fair whack of weight on carries.

    The stuff apparently works much like WRC (haven't tried it myself) and looks quite decent.

    Pix here: http://www.paulowniatimbersales.com.au/page10/index.html
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.