designing a fast rowboat

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

  1. keith66
    Joined: Sep 2007
    Posts: 332
    Likes: 24, Points: 18, Legacy Rep: 168
    Location: Essex UK

    keith66 Senior Member

    The RCR is 14 miles dead on with 4 legs of 3 1/2 miles each, look up Canvey island Essex UK on Google maps, we start from the Benfleet yacht club at the top & go eastwards round Canvey point then to Holehaven then to the Easthaven barrier & back to the club
    The boat is a version of the Hanningfield skiff on my website, www.seaxmarine.co.uk, photos of the earlier boat are on there.
    The boat is a working Skiff style and is 18ft x 4' 6" beam, she has a good carrying capacity & can carry a crew of 4, shes a good seaboat.
    I have kept a log of the materials used & with the spars & oars im not far out on that estimate.
    I agree its heavy but the buoyancy issue is something that has to be addressed for RCD purposes, trouble is interior mouldings are hopeless when it comes to weight.
    However earlier even heavier versions have done consistently well in the Great river race, at least one goes well over 500lds. The lightest one Lara has been in the top 5 for years & she was around 200lds
    The design is limited in that its a big boat & there is only so much weight to save without the boat being too fragile.
     
  2. nordvindcrew
    Joined: Sep 2006
    Posts: 541
    Likes: 13, Points: 18, Legacy Rep: 231
    Location: Marshfield massachusetts usa

    nordvindcrew Senior Member

    up dates

    well, we never did the Minots Light Roundabout. It was a beautiful day but I had an acident and burned my right hand with an oxy-acetylene torch and was out of commission. Things healed enough to do the Weir river race in late october and take first in workboat and 4th out of 12 doubles. We got a good time, only 2 minutes off our best time. We rowed a good solid race and managed to stay in synch and navigate well. We took a course way off the straight-line to the finish to take advantage of a strong favorable current.It helped us quite a bit. Other than Sunday morning training rows the next event is New Years Day for a fun row and pot luck dinner afterwards. Usually only 10/15 boats but a good time to row, eat, and tell lies about the races.
     
  3. keith66
    Joined: Sep 2007
    Posts: 332
    Likes: 24, Points: 18, Legacy Rep: 168
    Location: Essex UK

    keith66 Senior Member

    Well its been some time but im in my new building shed.
    Project is a 27' 6" four oared Gig, she is one of a series i drew using Delftship pro & she looks good to me! I have had more than a few hair tearing out moments with the programme including a recent one with control curves & fairing but i suppose that goes with the territory.
    Im lofting her out full size. It might seem to be a retrograde step but lack of time & inclination to learn another 2d drawing programme mean its easier, to be honest im not sure i trust my proficiency with Delftship & my hairs grey enough already! Looking to get the first boat on the water early summer.
     
  4. DickT
    Joined: Apr 2008
    Posts: 96
    Likes: 3, Points: 8, Legacy Rep: 49
    Location: middlebury, vt

    DickT Junior Member

    Lake Champlain Maritime Museum Gigs

    Great get-together last night. My wife works with the kids who work on the boats.
     

    Attached Files:

  5. Clinton B Chase
    Joined: Mar 2005
    Posts: 227
    Likes: 2, Points: 18, Legacy Rep: 21
    Location: Saco, ME

    Clinton B Chase Senior Member

    Racing season is here

    Only been out twice but should be able to get two more rows in before the Essex R. race.

    It may be my last weekend in Drake, if I am lucky.

    I plan to build another Drake -- one that incorporates what I have learned about making a good rowboat since I drew Drake -- and one that might allow me to fold in the outriggers and put my oars directly on gunwale.

    I've also entertained an entirely new design or building a St/ Law. R. Skiff for single rowing...this summer I'll be finishing a Bobby which ought to prove fast for doubles rowing.

    2013 will be the year of a new rowboat for me.
     
  6. DickT
    Joined: Apr 2008
    Posts: 96
    Likes: 3, Points: 8, Legacy Rep: 49
    Location: middlebury, vt

    DickT Junior Member

    What oarlock spread do you have in mind? I'm presently content with 44" with 9' non-feathering oars and would consider less on a lighter boat with lighter oars. I don't like the wide spread on the piantedosi drop-in sliding seat unit.

    Always curious what works for others.
     
  7. flo-mo
    Joined: Jul 2010
    Posts: 49
    Likes: 3, Points: 8, Legacy Rep: 43
    Location: Vienna, Austria

    flo-mo Junior Member

    Great to hear about Drake 2.0 - I am wondering what the changes might be.

    My guess would be:

    More length, less beam at waterline – less stability
    Scantlings reduced to the maximum - therefore less weight
    More spread at the oarlocks (as you already stated)
    Higher prismatic coefficient (0.56-0.58)
    Still keeping the seaworthiness and classy looks of Drake 1.0

    The image that comes to my mind would be a perfect blend of Paul Gartside’s Coastal Rowboat and Puuvenepiste’s finnish rowboats.

    Clint's original Drake:
    [​IMG]

    http://store.gartsideboats.com/coll...edal-boat/products/17-ft-coastal-rowboat-179#

    [​IMG]
     
  8. rowboat70
    Joined: May 2013
    Posts: 13
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: United States

    rowboat70 Junior Member

    Rowing Canoe

    My rowboat is a 23-foot Minnesota IV my Winonah in Minnesota.
    The kevlar canoe weighs 65 Lbs, and I use it in the salt water of Biscayne Bay and in the ocean off Miami Beach, Florida.
    I designed and built my own rowing rig. I can send drawings and photos.
    I competed in the 22-mile Blackburn Regatta, a circumnavigation of Cape Ann (Gloucester), and finished 150th out of 200 entrants both years. I was in my middle 60s at the time. These days, my usual row is more like 10 miles.
     
  9. Clinton B Chase
    Joined: Mar 2005
    Posts: 227
    Likes: 2, Points: 18, Legacy Rep: 21
    Location: Saco, ME

    Clinton B Chase Senior Member

    I'm all ears...planning for the next build. Would like to design something but why reinvent the wheel.

    My goal in life is to beat a Guideboat.

    I'd love to hear more about the hull you drew.

    FLO MO, yes Drake mk II will have those characteristics but it won't necessarily be my answer to beating the Guideboat...it will be the same wonderful, versatile, fast and seaworthy boat but with tweaks.
     
  10. ancient kayaker
    Joined: Aug 2006
    Posts: 3,497
    Likes: 147, Points: 0, Legacy Rep: 2291
    Location: Alliston, Ontario, Canada

    ancient kayaker aka Terry Haines

    The most promising area for research for competitive purposes may be construction. Specifically, to find and develop the construction method that delivers the most flexibility of hull shape for the lowest weight. Traditional guideboat construction has already progressed a long way down this path, of course, but surely there is room for more improvement.

    Leaving aside the composites, for wooden hulls one method that has had a lot of promotion recently seems to have been the strip-build method. However, many including myself consider it a composite since the fiberglass is doing most of the work and the wood is just along for the ride. It certainly gets a lot of support from the epoxy industry.

    Plywood is a great material but it constrains hull shape when plank count is kept low, and also results in prominent chines with the potential for turbulence. When plank count is higher lapstrake comes into its own but again at the cost of turbulence along the seams. This can be mitigated but not eliminated by the use of flow-analysis software.

    Multi-layer veneer-based methods result in very light and rigid hulls. Again, unless sophisticated vacuum molds are used they limit hull shape somewhat, and the cost and availability of the veneer is not encouraging. Resin use is high with this approach, with high cost (epoxy), elevated temperature post cure (vinyl ester) or stinky working conditions and risk of brittleness (polyester).

    So for the competitive wooden boat builder with limited funds, hull shape is still somewhat limited by the constraints of suitable construction methods. I am developing a new ply-based construction system myself. I feel what is needed is lightweight, minimal limitation of hull shape, fast construction for rapid prototyping, use of readily available materials, and possible with non-specialist skills and resources. It needs a little more time: in the meantime what else is out there that looks promising?
     
  11. NoEyeDeer
    Joined: Jun 2010
    Posts: 983
    Likes: 32, Points: 28, Legacy Rep: 300
    Location: Australia

    NoEyeDeer Senior Member

    Those Finnish boats go like the clappers, and they're only three clinker strakes each side. I wouldn't necessarily be too worried about the drag penalty.
     
  12. KJL38
    Joined: Jun 2008
    Posts: 95
    Likes: 12, Points: 8, Legacy Rep: 75
    Location: Tasmania

    KJL38 Junior Member

    Looking at the specs for Drake, I think if you want to challenge the Guideboats you need to lose a lot of weight and waterline beam. My guideboat is aproximately 55lbs and with one person the WL beam would be under 28".

    I am sure that some of the designs that appear earlier in this thread would beat a guideboat but may not work as well for camping trips.
     
  13. Clinton B Chase
    Joined: Mar 2005
    Posts: 227
    Likes: 2, Points: 18, Legacy Rep: 21
    Location: Saco, ME

    Clinton B Chase Senior Member

    Savo 575

    The 19-footer (575) is 4 strakes. I had planned to distribute kits, but I am teaching full time now so don't have the time. However, I need a fast rowboat again to woop some guideboats so have spoken with the Savo builder about getting one over here for me to use in fixed seat class.

    It is light, good looking...my only concern is can I power 19' of waterline fixed seat?
    The hull has a Cp of about 0.52 and the wetted SA 2.47 sq. m which turns out to be less than a 16' GB!

    When in shape, I can be fairly strong but don't want too much boat to get around Cape Anne.

    There is a fair bit of freeboard in the Finnish boat, so I am thinking of taking some out esp. midships. Drake has 12" or so of freeboard, and I feel the wind somewhat. The Finnish boat has about 13 1/4". Perhaps an inch less freeboard a midships would be good.

    I might want to see if we can get the Cp up a bit too.

    We also talked about a touch more rocker to help with negotiating open water conditions vs the lakes that this boat was designed to compete in.

    For fixed seat rowing, what do you think of the Savo575...as is or specialize it for fixed seat rowing with the aforementioned tweaks?
     
  14. NoEyeDeer
    Joined: Jun 2010
    Posts: 983
    Likes: 32, Points: 28, Legacy Rep: 300
    Location: Australia

    NoEyeDeer Senior Member

    If it has less wetted surface than a 16 foot guideboat (make sure you're comparing at the same total displacement) then I'd say you can definitely power it. You'll have less wetted surface drag and less wave drag. How is that going to be harder to row? ;)

    An inch off the height sounds ok to me. IIRC the Finnish boats are restricted to a certain minimum depth, which is probably more suitable for the heavier general purpose boats they evolved from.

    They also have a minimum beam at some height above the keel, so that effectively gives a minimum waterline beam too, which affects wetted surface.

    At a guess, I'd say the low prismatic is to reduce wetted surface. I know there are tables of supposed "ideal prismatic" for every speed/length ratio, but they hardly ever tell you what sort of hull they were testing. They might be testing cargo carriers or anything.

    If you look at sculls and the like, they have a prismatic which is lower than would be considered "ideal" for the speeds they do. This allows them to gain length without adding wetted surface (less girth in the ends), and the reduction in speed/length ratio has a bigger effect on wave drag than the lower prismatic. Net result: less wave drag in total. It's a balancing act.

    Dunno if the Savo would need more rocker. Guideboats have hardly any, but you'd be better placed to judge what you need for your conditions.

    ETA: Btw, guideboats have really low minimum freeboard. Somewhere around 9" I think.
     

  15. El_Guero

    El_Guero Previous Member

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.