designing a fast rowboat

Btw, if you want a self draining boat without relying on a bilge pump and don't like the aesthetics of Jean Marc Fage's boats (and I admit they don't really appeal to me) it is possible to get the same result with a more traditional look. All that's really required is a watertight cockpit sole which is slightly above the waterline and an opening at the stern to allow drainage. Once you have that you can do what you like with the looks. The old Olympic Finn and Flying Dutchman classes had this arrangement (along with more traditional looks) and it works very well. You can stick a Finn's mast in the water, swing your weight over onto the centreboard, bring the boat back up, swing back into the cockpit and sail off with a dry boat in the time it took to type this, and before the boat even stops moving.
Building higher and higher "fences " to keep the water out is not necessarily the most efficient way of dealing with the problem, especially for a racing boat.

 

up date on boat-oars

Melong,
The self-draining concept is a good one, sorry I mis-interperated your earlier post. We had briefly discussed that idea and still could incorporate it with the addition of some large scuppers. We aren't going to panic too much at the moment. The water we took in was splash -over, not the wave just coming in over the gunnels. Right now, our oars are out at the right spread, so if we were to add the wider rails they wouldn't have to carry the oarlocks, just keep out some water. Total amount of water taken in was only a couple of quarts, not too much to worry about, just kind of distracting. I made molds of the port and starboard oar blades over the weekend and molded a new starboard blade out of conventional fiberglass. It is a bit heavier than I would like, and kevlar or carbon fiber will be the next step after I am satisfied that the molds are producing a good blade. Does anyone have an idea of cost for carbon fiber cloth. The blades are 8.5" wide X 22" long. Being able to manufacture my own blades will open a lot of possibilities. I've made hollow shaft oars that are quite light and only need blades to be finished. The ability to have 2 or 3 sets of oars at varying lengths would help compensate for different wind and wave conditions. right now the current oars are all repaired with new PRESURE TREATED wood plugs and a fiberglass oar blade on one oar. There should be no failures this Saturday. This race is only about 4 miles and should be a good test. Based on Should-Have-Beens, and the speeds of the boats in the last race, I can't imagine that we couldn't have won if there hadn't been oar trouble.

 

First, thanks for an interesting story!

I noted the words "PRESURE TREATED".
This process damaged the cells in the wood, so the mechanical properties are not so good as in non treated dry wood. It also make the wood act like a sponge. Are we talking about the same thing? Green pressure treated wood?

 

P.T. wood

the wood is pressure treated, brown, not green but pressure treated non the less. I wasn't aware of the loss of strength or the swelling problem. The reason to choose treated wood is that the plug inserts into the hollow aluminum oar shaft and also into the hollow on the oar blade. Once wet, they never dry out and rotted out in less than 2 years. until I can come up with something else made out of fiberglass or some form of plastic, the wood will have to do. Always open to ideas. The plugs need to be about 10" long and have 2 different diameters to fit inside the shaft and blade. Right now, I don't have access to a lathe, so that limits what I can do to hand shaping and sanding

 

Kevlar and Carbon Fiber cloth

Jeff,

Here's one source. Depending on weight (you'll need to ask them about that, I don't know what the minimum weight/strength combo would be), looks like you could get enough for a set of blades for less than $40.00.
http://www.shopmaninc.com/hybrids.html

 

carbon fiber etc.

Charlie,

Good site with good info. I'm going to do a few blades in regular cloth and polyester resin untill I get more familar with what I need and how the molds are working. The one blade I've done so far worked out OK but not great. All I did was mold the bottom of the blade and work in that. Looks like I'll have to make a top section of the mold to compress the laminate to get the shape right with out any voids or high spots. The tubular section where the blade meets the shaft is a bit of a mystery as of yet, but I think there is a fairly easy solution to that with a pre-molded piece that will slide into the shafts and get molded into the blade as we laminate them. Actually, I'm pretty enthused about this process. The race disaster is turning into something good. If I'm able to mold my own blades,
then having an inventory of oars of differing lengths for different conditions becomes a reality. To go into kevlar or carbon fiber I will need to get some recommndations from the supplier about the thickness and nature of the lay-up to get the right combination of weight and strength.

Thanks, Jeff

 

Will wood covered with glass and epoxy be an option?
Or will water find it's way anyway?

 

Or wood treated with tar and other poisons?

 

elimiminate wood

My brain is churning on a plan to make a two piece mold to the inside diameter of our shafts. A plug of urethane foam would be wrapped with cloth and then saturated with resin and put in the mold to be compressed to the finished size. The resulting hollow lamination can be made as strong as necessary and then be added to the blades as they are laminated. eliminates (hopefully) the weak link in the system.

 

I have an easier idea. Why not use some more aluminium tube of the right diameter for your plug? Then you just laminate the blade around it and stick it in the end of your oar.

ETA: One thing to watch with aluminium and carbon in salt water is galvanic corrosion. Carbon is a top cathode and will eat aluminium for breakfast unless thoroughly insulated by resin. Keep an eye on this or you'll have trouble.

 

Got another idea you could try. Are there any amateur wood turners near where you live? One of them would probably knock you up some tapered plugs in whatever size you like for a six pack of beer (assuming you supply the wood).

 

oars

Melong,

Good info. The problem is that there is no stock tubing size that is a close slip-fit inside the shafts we have. Did not realize the problem with carbon fiber and aluminum. Would there be a problem with Kevlar? I'm building a small wood lathe in my shop. Crude, but it will turn out the pieces I need. The goal is to eliminate the wood plug entirely and replace it with a molded piece that is integral with the blade. Interestingly enough, the crude fiberglass and polyester resin blade, complete with plug isn't horribly heavier than the original blade. It is, however, much stiffer than the originals. We'll see how bad that affects things on Saturday. Forecast for race day: cold, in the range of 45 degrees F, rain showers, and a gusty wind out of the North-East. Plymouth Bay runs north and south and to a lesser degree, easterly. We'll be doing a triangular course. North then south-easterly then north-westerly back to the start/finish line. the wind will a miserable factor in the 1st and 3thd legs of the race. A good test of the boats sea-keeping abilities, I think. If the "official photographer" does her job I'll have some pictures to send along. Last race, she didn't know how to operate the zoom lens and the pictures show us as a small amber dot in the distance.

Cheers, Jeff

 

finishing the boat

As I've mentioned, the boat is a cosmetic mess. My brother is finishing the garage on his house so we'll have a place to get in out of the weather to work this winter. With a lttle heat we can probably finish her off this winter. Plans are for a buff hull with white interior, rub rails ( decking mahogany) either natural oil finish or painted black or dark grey. We have decided on the name. It will be done in a comercial stencil style midships on both sides of the boat.

NORDFIJORD salt CO. #1
cod

Kind of reminiscant of the way dories on the Gloucester Fishing schooners were identified. At any rate, it will confuse most folks about its' meaning. Letters of the major words the way I'm showing it Aren't accurate, the major words will be larger and the words "salt cod" will be much smaller to have the same height as the major letters.

 

race start

I just was on the Hull Lifesaving museum site and found a picture of the start of our last race. Go to www.lifesavingmuseum.org and look at race results for the Weir river race. there are three photos there. Click on the middle photo, it shows us in the upper right corner as well as a good sample of the competition. got to check to see if our other boat is in there too

 

Kevlar's fine with aluminium. No galvanic action at all as Kevlar is basically glorified nylon. Carbon is potentially lighter though.
Having your new blades stiffer would be an advantage IMO. I'm not sure what your old ones are made of but if they're similar to some of the moulded plastic blades I've seen over here they'll be too flexible and not particularly light.
Your boat looks good in the water from what I can see in that photo. I like the black double in front of you too. That one looks like serious competition.
Btw, if you're up against quads as well it isn't really fair. Take a look at the results from sculling and sweep championships (ie. Olympics, etc). A good double will always be faster than a single, a quad faster than a double and an eight beats the lot. Incidentally quad and double sculls are slightly faster than fours and pairs. Two oars per person is more efficient.
Race conditions sound bloody terrible. Best of luck.