Ultimate river dory.

Discussion in 'Boat Design' started by river runner, Oct 25, 2011.

  1. river runner
    Joined: Jul 2011
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    Location: Colorado

    river runner baker

    Suppose you decide to pull out all the stops and build the ultimate river dory. Instead of starting with an existing design (the drift boat), which is also based on an existing deisgn (the Banks dory), you start with a clean sheet of paper. Cost is no object and neither is build difficulty. Your only consideration is floating down rapid infested rivers with the least amount of effort and the greatest amound of safety.

    What would your boat look like?
    Mine might look something like this.
     

    Attached Files:

  2. WillyG

    WillyG Previous Member

    That will work. I wonder if the multichine design is easier to build than an equivalent stripper that uses the plywood to make the big surface areas and the strips to give you the sweet curves? One might say that your best effort would be to look at the overall shape of the proposed boat fore, aft and side to side. Then make a call as to what build method would work best. Sometimes the build is not one, or the other, but a mixture/hybrid example to get the best of both worlds with the least amount of fuss.
     
  3. garren
    Joined: Mar 2009
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    Location: Billings, Montana

    garren Junior Member

    I can't open your file. Can you post more images?

    It looks similar to a design I have in mind although mine is simply a 17' gunning dory with a wider bottom and enhanced sheer. I'm thinking strip planked.

    Thanks - Gary
     
  4. KJL38
    Joined: Jun 2008
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    Location: Tasmania

    KJL38 Junior Member

    What size whitewater is this design intended for? Also could you post an above view? It has a lot of similarity to the early boats used by Powell and others on the grand canyon except for being double ended which was suggested as an improvement. There are some pictures in "Romance of the Colorado" which can be downloaded at http://www.gutenberg.org/ebooks/4316 These expeditions found it necessary to portage a lot.

    If it were my design for big water I would want a lot more flare and rocker and would also minimise weight to improve acceleration.

    For dealing with standing waves have you considered how waves are handled by surf boats? The Seabright Dories and Australian Surfboats are examples http://www.woodworkforums.com/attac...-ofr-surf-lifesaving-wooden-boat-surfboat.jpg The Australian surfboats are derived from whaleboats with about a hundred years of evolution since and are specialised for racing out through the break and surfing back in. Where they differ to a boat for whitewater is in being optimised for speed rather than maneuverability and having four oarsmen and a sweep.

    As a tool to determine the requirements of the design perhaps you could make a list of attributes such as speed, maneuverability, stability, wave penetrating, capacity etc and rank them by importance as you see them. Then where there is a conflict between competing imperatives you could favour one in proportion to it's importance.

    As a thought experiment this is what I came up with:-
    For the Grand Canyon I think the ability to spin on the spot is probably at the top of my list followed by the ability to accelerate rapidly to cross away from trouble all balanced against stability and the ability to handle holes. I would rate speed on the flats at the bottom of the list as spending time in the canyon is much more important than reaching a destination quickly.

    So lots of rocker for turning, round bilges for speed and to avoid tripping on the chines but mostly flat bottom for stability and low draft, lots of flare above the waterline for secondary stability and climbing waves, self bailing with waterproof storage below the floor to keep the COG low. Reduce weight as much as possible.
     
  5. garren
    Joined: Mar 2009
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    Location: Billings, Montana

    garren Junior Member

    Was able to view your profile image at home. Both images look a lot like the "gunning dory" I scratched out in pencil today.

    What are your dimensions?

    Gary
     
  6. KJL38
    Joined: Jun 2008
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    Location: Tasmania

    KJL38 Junior Member

  7. KJL38
    Joined: Jun 2008
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    Location: Tasmania

    KJL38 Junior Member

    OK rethink- Below the waterline like a scaled up Zet Raptor kayak http://www.zet-kayaks.com/?p=40 This would give a good combination of speed v turning with rails for carving into eddys but less chance of tripping on the chine than the traditional dory.

    Flared sides with extreme flare in the ends like the surfboat bow http://www.woodworkforums.com/attac...-ofr-surf-lifesaving-wooden-boat-surfboat.jpg For climbing waves and a dryer ride, also for secondary stability.

    Enclosed decks at each end and wide side decks. Raised self bailing floor like a surf dory http://www.pearsonunlimited.com/DorySpecs.html Large central scuppers on each side and smaller scuppers in front and back corners with floor sloping down to center aprox 2" above waterline. This avoids large masses of water suddenly altering the balance as seen in this clip http://www.youtube.com/watch?v=-pfnQrXpZ7w The side decks keep the passengers in the center of the boat and improve secondary stability if you drop a gunwale.

    Low seat heights for passengers. I'm also wondering if there is a way to make it easier to get swimmers back into the boat?

    The hull up to floor level could be carved from foam, other sections made from foam and attached with it all encased in composites. This would make a fun lightweight boat for day use or storage lockers could be added for tripping.
     
  8. river runner
    Joined: Jul 2011
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    Location: Colorado

    river runner baker

    influence, image

    I've reattached the image. We'll see if it comes through better this time.
    My design was influenced by a surf boat by John Gardner in his book 'The Dory Book'. It was used by an oil company to get men from the beach out to a boat that would then take them to the oil rig.
    The boats Powell used were wherries. A design meant to be rowed facing the stern, which is what they did. This design is not only a double ender and rowed facing the bow, but is much wider than the Powell boats and has more rocker. This boat is 7.5 feet wide and almost 19 ft. long.
    I'm not convinced the traditional bow on single chine dories is the best for standing waves (see my other thread on penetrating waves). I'm inclined to think a curved stem like this might work better in rapids.
     

    Attached Files:

  9. river runner
    Joined: Jul 2011
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    Location: Colorado

    river runner baker

    Here is an image of a different angle. If nothing else, I think it looks good. I may not know much about the engineering part, but I think I have a pretty good eye.
    I think I have one more boat build in me. I'm torn between a small cruising sailboat, which I've always wanted, and a bigger dory than the one I already built. So there is at least a 50% chance I'll actually build this boat. But I'm not going to make the mistake I made last time and rush into it, then discovery that I made some stupid design blunder or just hadn't thought some detail through completely. I'm going to take my time till I'm as sure as I can be that everything is right.
    The design program I'm using (Prochine) only does chine boats, so I didn't have much choice. I had to design a chine boat. But that probably isn't going to be how I build it. John Gardner's surf dory is lapstrake, and that would make a pretty boat. But I'm thinking of trying to eliminate all wood from the boat(except gunnels) so I don't have to worry about water getting under the glass and epoxy and rotting the wood. I'm thinking of doing a one-off fiberglass with foam core. I'm working up the courage to spend the $395 for the more advanced program that will allow me to design a round bottom boat.
     

    Attached Files:

  10. garren
    Joined: Mar 2009
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    Location: Billings, Montana

    garren Junior Member

    I'm going foreward with my combination gunning/surf dory from Gardner's book although I'm more in line with the dimensions of the Smith/Wales gunning dory. So far, I've considered widening the bottom to 30" and increasing the rocker by an inch or so. Stem height might be increased as well. I will soften the angles in the lapstrake-designed frames and strip plank this hull to see if I really want to strip plank a larger sail boat afterwards.

    I'm not up to speed with any of the computer-aided design programs so I'm going to have to design/loft with pencil and paper.

    Wish me luck. I hope to have it on the river by next fall when company arrives expecting a "guided" fishing trip.

    Gary
     

  11. river runner
    Joined: Jul 2011
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    Location: Colorado

    river runner baker

    gunning dory

    The Chamberlain gunning dory from The Dory Book is one of the most beautiful row boats I've ever seen. I found some photos on the internet of one that some guy built and it is just incredible. He really did a good job. You might do a seach and see if you can find it.
    New Wave Systems has fairly inexpensive design programs. It is pretty easy to get to the point of being able to make a picture like I've posted here. I'm still trying to figure out some of the rest. If you know what you're doing, it will make a table of offsets for you. I used it to make CAD files of the plywood panels I needed and sent those to a company that cut them out with a CNC router. Saved me a ton of work. You could find someone to cut out frame parts or whatever and save yourself some work.
     
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