designing a fast rowboat

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

  1. nordvindcrew
    Joined: Sep 2006
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    nordvindcrew Senior Member

    help

    I'm at a stop on my skin on frame boat. Robert Morris, who wrote the book I'm working from says either canvas or balliatic nylon can be used to cover the frame. I'd prefer to use the nylon if I can. The problem is that I don't know what to buy, both weight and type of nylon. I can get 15 OZ canvas locally but, I'm am not sure if it is strong enough. I've asked mr. Morris to help and have no reply as yet. When I first contacted him about this project, he was very supportive, but now, I'm getting no answers. Any ideas to help me? The boat frame is all done and just needs to be painted out before the skin goes on. I'm going crazy wanting to get her out on the water but don't want to rush it and screw up on the fabric choice. If I choose canvas how do I waterproof it? I'm thinking of marine enamel, using a lot of coats, but wonder if it will be too brittle and tear easily. Maybe an acrylic house paint?
     
  2. kmorin
    Joined: Apr 2005
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    kmorin Senior Member

    Aircraft Coverings?

    nordvindcrew,
    I'm the last guy on the board to ask about covering a frame with cloth but it occurred to me that the aircraft fabric and coatings might be tough enough? I'm almost sure the stuff is a synthetic fabric now-a-days and I'm sure the planes I've been in that were 'rag' covered were very waterproof and the fabric tough.

    I don't know if its as tough as kayak/canoe coverings and its bound to be expensive if its for an airplane, but its a very durable product that has lots of R&D and harsh testing.

    cheers,
     
  3. KJL38
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    KJL38 Senior Member

    Last edited: Aug 22, 2008
  4. nordvindcrew
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    nordvindcrew Senior Member

    problem solved thank you.

    I guess it will be 15 oz canvas with an oil based marine paint. It's so easy when people with more knowledge than I have offer help. I'll buy the canvas next week and start skinning her out shortly. Work on the boat as been slow due to Projects in my yard: grading and filling low areas and moving my shed/ workshop to a new location to improve working conditions and improve the way my property looks. New set up has two sheds pararrell to one another and 10' apart so I can have a 10' X 20' platform in between to work on. My land is low and damp so I can't build a real work shop with a foundation. Hell, my house doesn't even have a cellar because the water table is only 30" below grade. Just love to work out in the weather just like the real boat builders did and do
     
  5. kmorin
    Joined: Apr 2005
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    kmorin Senior Member

    Thanks for the Inspiration Nordvincrew

    nordvindcrew,
    after reading of your rowing adventures with your brother and being of an age, I decided to take another look a rowing dory I built some time back and showed its new seats here, I think? (didn't look back)

    Anyway more to the point http://www.cityofseldovia.com/html/harbor.htm this link should take you to a picture of a rowing route a friend and I followed this past weekend.

    This is Seldovia Bay and the tide moves up and down 20' high to low in 6 hours and back up again. That empties a lot of water and the current when it runs is upwards of 5 knots and 8 at some points and headlands.

    http://www.cityofseldovia.com/ http://www.seldovia.com/images/pict_aerialtown133_2.jpg views of the harbor and Bay from another angle http://www.seldovia.com/pictoftheday/070708_GrayCliffsJune2007-DSC06741_glover.jpg this last link shows the two islands in the background and the point on the Harbor side of the Bay we used as the 2nd point in our triangular route. http://www.seldovia.com/pictoftheday/070807_AerialSeldoviaJuly2007-DSC06876_glover.jpg here is a shot of the Bay looking to the South up Seldovia Bay past the town.

    [We rowed past the far island, in the middle of the last link's picture, then to the far side of the Bay also, sometimes standing still for several minutes as the tide beat our efforts, but eventually moving enough to get back inside the break water.]


    The reason I'm writing to thank you for the inspiration is that we had accepted the 'fact' that we couldn't row against this tide effectively so we hadn't tried.... everyone said...... so we didn't try.

    Well, two of us left in the Harbor in the fore ground (first link's pic) while it was flooding past the islands and into the Bay at the left, pulled to the nearest island and then to the farthest then to the right out of the photo's edge and back with the tide. A power boat with GPS 'clocked' us at 3.9 knots for a short pull and we beat the tide -which was a surprise as we figured it was just too much to do.

    No race, no one else thinking of rowing there, some kayaking here and there, but we rowed the few miles and were smiling every pull on those oars.

    I'm confident if I hadn't read your contributions to this thread here - I'd have left the dory in the weeds at the back of the shop yard. Thanks again for the inspiration, I've had more fun in a series of rowing trips in this area in the last few weeks than I've had there in a decade of going with our power boats.

    Cheers,
    kmorin
     
  6. Squidly-Diddly
    Joined: Sep 2007
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    Squidly-Diddly Senior Member

    Nord, when I 'skinned' a PVC pipe framed kayak with

    water-proof nylon tent material...it was surprised at how much the water bowed in the fabric and how much volume was lost.

    Couple tips.

    Make sure the fabric wont stretch, or shrink. Shrinking would probably bust up your light frame.

    After my first test paddle with decks nearly awash, I decided to add one layer of fiberglass over the nylon, and it worked great without much added weight.

    PS-my frame 'runners' were pretty far apart, about 3-5 inches.
     
  7. nordvindcrew
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    nordvindcrew Senior Member

    cheers

    Hey Kmorin, glad you got out the dory and went rowing. We get out almost every Sunday year-round and feel cheated if the weather is just too nasty to go. We see seals, basking sharks, ocean sunfish and many other kinds of sea life. Mostly though we just enjoy being out on the water and each others company as we ponder the mysteries of rowing efficiency. A couple of years ago, we got caught in Hull Gut. THe gut is very narrow and funnels a lot of water out of boston harbor. A falling tide and an East wind almost proved to be our undoing. Rowing at pretty near full clip, we rowed into a patch of steep,close waves coming at all angles. We took on some water until we slowed enough to just ride in it. It was kind of scary for awhile until things settled down. Good feeling though to get the adreniline pumping and feel a bit of danger on a cold winter sea. Look up the poem thread by searching " Kipling" I've got one in there you might like. Pull hard, no excuses!! Jeff
     
  8. nordvindcrew
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    nordvindcrew Senior Member

    Welding aluminum

    Kmorin, this is off the thread topic, but I'm still working on the idea of building a S.F. Pelican. I can weld reasonably well but don't have the equipment or knowledge to welding aluminum. I currently have a gas powered Lincoln stick welder and am pretty good with it. Am I crazy to think I can utilize what I have with some additional equipment and also learn to lay down a good weld on aluminum plate. If I do this, I'm going to err on the heavy side on the plate due to the abundance of large rocks lurking under the surface and on the beaches around here. Thanks, Jeff
     
  9. kmorin
    Joined: Apr 2005
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    kmorin Senior Member

    Aluminum Welding with Stick Machine

    nordvindcrew,

    Metal Inert Gas [wire MIG] needs a power supply that is CV or constant voltage where the amperage is modulated, by the power supply, up and down when the resistance (distance of wire feed tip and wire to parent metal) changes. By modulating the amperage in order to keep the voltage as constant as possible the wire's burn rate is most constant.

    Since the wire's cross section is fixed and thin, any voltage change will result in a variation of the arc length ('rate of burn or wire') and that will translate into a varied puddle width and deposition so the bead will be radically NON-uniform. So, the control circuit for MIG tries to keep a constant voltage in order that the weld is most uniform.

    The only way MIG works is to constantly feed wire, at hundreds of inches of wire per minute, into the top of the arc cone so that the arc doesn't 'burn back' or reach the copper contact tip. If that happens the copper melts and the wire quits feeding and welding copper mixed with molten aluminum is not good practice!

    Stick machines don't usually have CV control circuits, but some portables do, so they don't convert to MIG well.

    If you're planning to build something this small you should plan for a new CV machine/power supply; an inverter based power supply intended for that type of welding. I'd suggest using/buying/acquiring a "1 lb." or pistol style 'mig gun' instead of push pull since there is so much cost difference and the push-pull gun/wire feeders are for full time 8 hour days of burning wire.

    There's no need for sheet any heavier than 0.080" just for rocks- but you'll probably end up in 0.125" just because welding thinner that that has some headaches. Also the alloys available in your area will 'vote' on your material thickness choices- you want 5083 or 5086 and could settle for 5052- but try for the first two. Unfortunately they're not as readily available in thicknesses below 1/8" so that's why the alloy and thickness cycle has to be resolved with your supplier(s).

    Don't discount eBay or Craig's List sources as these machines and welding feeders are always up for sale. Many of them are not reliable but a used Lincoln or Miller system retains most of its serviceability for decades. I've seen and bought very high quality systems for fractions of the original costs as the systems were a generation of technology older than today's. The value was still there- I'd used exactly the same systems but paid much less 20 years later compared to new prices when buying the first version.

    Cheers,
     
  10. clmanges
    Joined: Jul 2008
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    clmanges Senior Member

    Yeah, don't try welding aluminum with stick. You'll use up all your cuss-words and have to invent new ones.
     
  11. nordvindcrew
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    nordvindcrew Senior Member

    welding

    The other option is to jig everything up and bring it out to be welded. Trick there though is to find a welder who isn't trying to retire off my project. If the logistics (cost) are too daunting, I'll go back to the plywood the plans call for. Back to rowing. The frame for the new SOF boat is done but for a little sanding and a couple of coats of primer. Will order canvas this week and hope to launch by end of Sept. There are a couple spots where he fairness is a little less than sweet, but with some spot steaming and maybe a couple of shims they will go away. I'm really excited to try a light boat to see the difference losing a hundred pounds makes. It's all a learning curve. Just being on the water makes it worthwhile. I'm looking forward to a sunny winter day and a long row on Duxbury Bay and down to Plymouth. Lying at anchor and soaking in the sun on the right day is a treat, especially when you have the whole bay to yourself.
     
  12. DickT
    Joined: Apr 2008
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    DickT Junior Member

    Short Race

    Did a 3 mile mile race yesterday in 32:16, 7 seconds behind a 17' Adk Guideboat with two rowing, and about 30 seconds behind a 6 oared gig and a 22' outrigger canoe. They started the gigs a minute early and I passed 4 of them which was kind of sketchy, especially near the marks. I'm pleased with the way the boat performed, but I was still pulling a steep transverse wave that I haven't noticed on guideboats with similar lwl at the same speed.
     
  13. nordvindcrew
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    nordvindcrew Senior Member

    congrats

    Great effort and finish in the race. To pass a six oared gig is to be going some. we manage to beat some on time but have never passed one. Our races start in the reverse order with slower boats first and fastest last, therefore, our task is to keep gigs from passing us. RE your transverse stern wave: I'm not an expert, just an observer. What is your weight? draft affects stern waves. How about fore and aft location? that affects it too. Lastly, you are at or above hull speed and that's when the waves start to build up. Have you checked out your hull lines against any others? anything radically different shuold attract your attention. Your chagrin is understandable. When I row against a guide boat, the lack of stern wave and apparent ease of motion makes me almost crazy. On the other hand, people often comment that our boat looks to be easily rowed and, believe me, it isn't. Kind of a watery optical ilusion being played out on everyone.
     
  14. DickT
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    DickT Junior Member

    The six oared gigs were high school crews. One team had it together and was way out front with the outrigger canoe guy. I stuck tight to the couple in the 17' guideboat and we passed the other gigs as one boat. I use an eyeglass mount rear view mirror so my view of all this is about the size of a bottle cap.

    I weigh 200lbs and the boat and oars is probably another 100(maybe more). My latest "hypothesis" for the transverse wave is that the hollow in the forward water line is letting the water under the flat bottom board which pushes it down creating the wave. I'm considering fattening up the bow and putting a shallow vee on the bottom board. Maybe I should quit worrying, leave it alone and build another, lighter boat with a different set of problems.
     

  15. Guest625101138

    Guest625101138 Previous Member

    DickT
    I have produced an approximate wave patch of your 17 foot boat at 6 knots and displacing 300lb. The wave patch shows peak to peak of 104mm or about 4 inches. This may seem small but sitting in the boat it will look significant. Almost have of your power would be going into wave making at this speed.

    Typically when you start pressing toward hull speed you need fuller ends to get the lowest drag and reduced maximum beam. The compromise is stability.

    I only estimated the hull from the photos so it may not be all that accurate but if the wave pattern looks like what you are seeing then it would be useful basis for analysing benefit of any changes.

    The wave patch is a 20m square and provides a birds eye view with shading to represent wave height. This is output from Michlet.

    Rick W.
     

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