designing a fast rowboat

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

  1. nordvindcrew
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    nordvindcrew Senior Member

    irony

    Got a call from another rower last night, he wants to row a double in the race and is asking to borrow our "old' boat. He's real strong, and it could open the possibility of being beaten by my own boat. Going to check with my brother for his imput but I'm inclined to say yes just for the competition. Melong, thanks for the encouragement, even if you row something different, the design process is the same and I'm sure that your knowledge would be of help to all of us
     
  2. nordvindcrew
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    nordvindcrew Senior Member

    suicide watch

    well, we're going to loan our old boat to Jon Aborn of Buzzards Bay ma. and an un-named partner. Jon is a tremendous oarsman, and if he recruits someone of like ability he might murder us. All we can hope for is that being in a different boat that isn't maximized for him and his crew will slow them down a bit. As usual, the pre race butterflys have started up big-time. Once we get the boat in the water and line up to take our start we''go into the "zone" where only the boat ahead of us matters. The hardest part is to get your breathing co-ordinated with your stroke pace. Once that happens the only thing is to try to remember to breath through your nose as much as possible to avoid getting a dry, cracked throat. Butt-Chafe is an ever present threat that can be combatted by lberal doses of baby powder. saturday is predicted to be high 50's to low 60's with a chance of rain or showers. No predictions of wind strength yet. If the weather goes berserk, the harbor-master will turn us around at the mouth of the Wier River and we'll back-track into Hull Harbor for the finish to a shorter race than the scheduled 6 miles. Next race is the Plymouth bay Row sponsored by Team Saquish. It is a 4.75 mile event on a tringular courser in Plymouth harbor. It is difficult in that the turning points are so far apart that it is hard to pick them up with a quick look over the shoulder to keep on course. We've got a score to settle with a crew fron New Bedford, Ma. They showed up with a 24' (More or less) version of a St.Lawrence Skiff with wierd club shaped oars. They got a mental edge on us and made a big jump on us at the start. They made that lead hold up for the whole race, and only added a hundred yards or so through the rest of the race. If we had out-sprinted them at the start it might have gone the other way. This year, maybe we'll hold the mental advantage with a lean mean looking 20' boat they've never seen before. Well' I can always dream, can't I?
     
  3. charmc
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    charmc Senior Member

    Dream bulls__t, Jeff! You're strong, you're experienced, you can row your heart out, and you're focused. The other boats don't matter, 'cause you're both going to pull like hell at the start signal, then after the initial sprint you can watch the other guys all you want 'cause you're facing to the rear where they'll all be. It's a done deal. ;) :cool:

    Your friendly forum cheerleader, :)
     
  4. nordvindcrew
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    nordvindcrew Senior Member

    remove suicide watch

    Jon Aborn will be in our 16'8" boat the "Nordvind" (hence:Nordvindcrew) with a totally inexperienced rower just to try to interest him in the sport. Unless he's a ringer, they won't be a threat. If the "Daniel J Murphy" shows up on Saturday, that will be our big challange. At 22' long and with a superb crew, they are, or have been unbeatable. We think we've got every chance in the world of beating them. Last race they got us by 6 feet per minute. Not an insurmountable difference.
    RE: Charlie and cheerleading, much appreciated, but a few sweet young ladies in short skirts would also be appreciated and do wonders to distract us.
    There's full moon high tides this weekend and I'm not sure how that will affect the race. Figuring the currents in the bay and using them, even if you row a slightly longer course, helped us to win a couple of times until the competition wised up and took the same route as us. Right now, too many variables. We'll spend the hour before the race talking strategy and hope to remember the plan as we start to get exhausted in the later part of the race
     
  5. melong
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    melong Junior Member

  6. Landlubber
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    Landlubber Senior Member

    Oh my God. PLEAS do not let Frosty see this pic, all those red and white pom poms, he will melt.
     
  7. nordvindcrew
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    nordvindcrew Senior Member

    fickle finger of fate

    Disaster struck! 100 yards into the race we broke an oar and had to struggle for the rest of the race trying to figure out the best way to continue. We settled on each rowing with one oar. The boat did not respond well at all and tried to pull to the opposite side of the boat as the aft oar. Keeping a straight course was impossible. We were beaten by our own boat, the Nordvind. our time over 5.5 miles was 1:04:15, the Nordvind with a novice crew member came in at 0:56:51. Winning time was 0:50:16 the boat was the Last Chance from Connecticut. We have never seen her before although the crew was familar. they turned a great time that would have been tough for us to match. At the time our oar snapped, we were still accelerating and had her up to almost 7 knots. We wouldn't have been able to hold that for too long, but clearly 5.5 knots for the race was easily possible. Got to track down new oars for the November race. Our oars are composite aluminum shafts and reinforced plastic blades. The manufacturer is no longer in business so we'll have to replace the nmissing blade with a copy of our own making or buy a whole new set of oars. Oh, Well, we'll see what the next race brings. One structural issue cropped up: we're too low in the waist and took in a couple of waves broadside. I think that the rub rails will have to come off to allow us to raise the sheer amidships about 3". Other than that the boat moves real well and surfs down-wind beautifully. Into the wind the ride is smooth with little pounding. Quartering is the only problem where we took in water in a fairly moderate choppy condition.
     
  8. melong
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    melong Junior Member

    Damn. I s'pose you'll be taking a spare next time. The boat full of cheerleaders could carry a few for you. The boat sounds good anyway. More freeboard amidships? How about using a leecloth arrangement of some sort? Less weight, not permanent when you don't have to deal with large waves, lower CG, etc.
    Or you could do like the French gigs and others and have a notched sheer. Keep your rowlocks at the height you want them and have a higher "barrier" each side. No point raising anything you don't have to.
    I always like to keep freeboard and thwarts as low as possible, but of course there are practical limits.
     
  9. nordvindcrew
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    nordvindcrew Senior Member

    spare oar

    0ur oars are asymetrical ie: port and starboard and do not interchange hence an extra set would be needed. To complicate matters, the manufacturer is out of business. I'm going to try to mold a new blade out of fiberglass to replace the one we lost. The weak link in the oars is a wooden plug that connects the molded blade to the aluminum shaft. It was not pressure treated and simply rotted. Shame on us for not checking them out on a regular basis. New oars are not an option financially at the moment, so the next option is to buy some clear spruce staging planks and make our own at a cost of about $20.00 per oar plus a lot of labor. better than $160.00 plus shipping. Still, all in all, to do almost 5 knots with a crippled boat encouraged us. Our old boat was within 6 minutes of the leader and a boat we always beat was only 4 minutes behind the leader. Conclusion: with the new boat all sorted out, we can do it!
     
  10. Clinton B Chase
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    Clinton B Chase Senior Member

    Nordvincrew, You are a serious racer! TX for the thoughts on the fine entry/flare question. The faering lofted out well. I have to relate a story that speaks volumes about the importance of changing a perspective while drawing. I brought what I thought was my finished lines plan to the copier to make some working copis for the shop. The gentleman made me reverse copies...negative images if you well such that the bow was now right side of paper. The boat looked weird and aweful to me! I hated it! The stems were strange looking and I was quite dismayed. I slept on it and finally redrew the stems and am satisfied now. I redid that part of the lofting. When I thought I was finished lofting I picked up my loft boards off the shop floor and propped them up on the bench and I stood on the opposite wall. A flatteness to the first lap slapped me in the face...my glasses almost flew off. I couldn't see it on the floor but there it was! So, change perspective a lot as you draw. I am pleased with how the body plan faired up and once I am done putting fresh paint on my Shellback dinghy I am off to make molds. I have a feeling the flare I put in forward may present some 'fairing' issues (no pun intended) but I am going with it. This is only version 1. Good thread.

    Cheers,
    Clint
     
  11. melong
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    melong Junior Member

    Here's an idea I just had; if the budget's tight and you need a new blade anyway how about making four blades out of carbon? You've probably already got resin and the amount of carbon you'd need wouldn't cost much at all. You could get lighter blades (and they're the part that have the most effect on balance and inertia) for much less than the cost of new oars. Might be worth considering.

    Regarding the tradeoff between windage and dryness, I really think that for best results you'll ultimately have to go for lower freeboard and a decked boat. I know it's a ******* of a thing to say at this stage but it makes a lot of sense. The weight of the decking can be partly offset by the weight reduction associated with lower freeboard. The centre of gravity can be lower, which helps stability. Furthermore you said earlier that you have your rowing stations quite widely separated for directional control in a strong breeze. This is a damned good reason to reduce windage. Having the weight of the crew spread out for and aft is bad for resistance in waves. The technical term is "polar moment of inertia". It leads to compounding effects.
    The higher inertia means the boat will pitch more slowly but through a greater range. This soaks up energy. Then to lift the greater weight at the ends you need more bouyancy. This means either more freeboard (therefore windage) or more flare (therefore a blunter entry into a wave). Either of these will increase resistance.
    My current thoughts are that the ultimate boat for your purpose would be fully decked (ballistic nylon is tough and light) and pretty much self draining if possible. The sheer could be made like a Thames Skiff if necessary to get the height and width at the rowlocks. The requirement for the rowlocks to be on the sheer would be the main determining factor for the shape of the midship section.
     
  12. nordvindcrew
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    nordvindcrew Senior Member

    changes

    Wow! so many ideas. First, the amount we might raise the sheer would be only about 3" in the waist of the boat to 0" at the ends. As much as we have raised our oarlocks almost that much anyway it wouldn't be any change to our rowing positions. Our position spread is 4'-6" with my thwart centered about 8' from the bow; 2nd thwart is about 12'-6' from the bow. Hopefully that hasn't spread the load to far fore and aft. Total boat length is 20'-3" , so it seems like we're not too far fore and aft. the only area where we're taking on water is amidships. This happens in a beam or quartering sea condition. Apparently the overall length of the boat is such that it is going through the waves rather than riding between them. Decking the boat may or may not be necessary. No water over the bow or stern. Decking amidships would make handling the oars impossible so that doesn't look like an option. Any coaming makes it difficult to drop the oar handles enough to get the blades high enough out of the water to clear the waves. New blades are in the agenda for this weekend. I've only got polyester resin on hand, so that's going to have to do along with a fiberglass mat and cloth lay-up. not super light, but servicable. We row with a slow cadence and very long pulls with that "snap" at the end of the pull. Certainly, if we rowed a fast pace, the lignter oars would become more important. Finishing dead last in class for the race was a serious dissapointment. We got a lot of support from everyone just for finishing. The general opion is that the new boat will be a serious competitor in future races. Nov. 17th is the Plymouth Bay Race. If the oars are repaired we'll give it another try then. Looking forward to seeing Clints lines for the faering. it is kind of spooky how much things change from paper to lofting to final three dimension. I don't "see" very well in 3 dimension so I rely heavily on my brother for that. He has a great sense dimension and proportion as well as the ability to visualize a complete boat from a set of lines.
     
  13. melong
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    melong Junior Member

    I wasn't suggesting decking the boat at the current sheer and fitting a coaming. Believe me I know all about the difficulty of handling oars in a beam sea and the necessity of getting the blades out of the water. What I'm suggesting is something along these lines (ie. not identical).
    http://www.jmf-yole.com/Version Anglaise/prod-en.html
    Look at the pictures of the one called "Regency". Unfortunately the idiotic site layout doesn't allow linking straight to the right page.
    It doesn't matter if water comes on board because it'll go straight out again. No problem. You're working on the mindset that you need a big fence to keep the water out. I'm saying you just need a way to drain it. Remember the Australian surf boats I mentioned earlier? They drive straight out through breaking surf up to thirteen feet high. You think you have problems? They do it by having a boat which is self draining. It works. If they tried to keep all the water out they'd need topsides a mile high.
    As for oars, by using heavier oars you are still wasting energy. How many strokes do you take over the course of a race? Every stroke requires you to stop the blades and reverse their travel twice. Being all macho about it won't make you faster.
     
  14. Clinton B Chase
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    Clinton B Chase Senior Member

    Fast, racing sailboats use the open transom concept, too. That is a wild, good idea. Sure ruins the traditional look of a boat, though.

    Nordvindcrew, what do you guys do after you've shipped water? Also, is it splashover from when the wave hits you broadside, or is it the wave face creeping up towards the gunwale and going over the side?

    Here is what I'd do: a very wide outside gunwale/rail...2-4" wide that tapers fore and aft. In a traditional yet fancy wherry I rowed this past summer, I was awe struck how the wide rails kept out 95% of the scary waves that came at us, usually large powerboat or ferry wakes. I would suggest, 3" of laminated pieces that are 3/4" thick each. Laminate them on, plane them down to a taper towards the ends of the boat down to an inch or inch and a half...you can step/stagger the lams so you don't waste wood. And you can end the rails to a normal thickness before you reach the ends. This has the effect of raising the sheer, b/c it really helps keep out the water. Gartside has rails like these on his boats; it is a traditional UK thing.

    Cheers,
    Clint
     

  15. melong
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    melong Junior Member

    That'd help, and has the advantage of giving more spread for your rowlocks. Two things you'd have to watch are a) added weight and b) bracing. The stress on the rowlocks could cause problems with a wide rail if you didn't have sufficient blocking near them.
    For self-bailing the Aussie surfboats have a small electric bilge pump that runs all the time.
     
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