designing a fast rowboat

[terhohalme]

Yes, the stern is required.

 

[nordvindcrew]

oars again

We currently have a set of oars with filled plastic blades and aluminum shafts. they are a lot heavier than you might think but bite the water beautifully. I also have ten hollow wooden oar shafts made with birdsmouth joints. The manufacturer of the plastic oars is no longer in business and I can't find any patent info on the blades so "splashing" shouldn't be an issue. Anyway, I've changed the general shape by narrowing the blades and lengthening them a bit so they are no longer the same blade anyway. We broke a shaft conection two years ago and lost one blade. I made plaster molds of both blades (asymetrical ) and some day soon will vacume bag a couple of sets of blades and graft them to the hollow shafts which should net me a good oar and one greatly reduced in weight. If it all works out maybe Clints' students could have a go at it too.

 

[Clinton B Chase]

Jeff would love to see what you are talking about in person. Maybe next rowing event. Which is that anyway? I chickened out of the Blackburn. Small craft warnings were out; not going to mess with that. I was still sore from a 15 mi row two days ago.

Clint

 

[nordvindcrew]

events

Clint, Not sure where the next race is. There doesn't seem to be any clear cut place to find them all. I'm sure that there is something up your way soon. My next will be the Great River Race down here in Marshfield in August. A 15 mile row is going some, good for you. There is an event down in Plymouth Ma. Nov. 7th being billed as the "nationals" with people being solicited from up and down the coast and as far away as England. Team Saquish is ponsering it but it isnot on their regular web site. I have to mold up a couple of blades to see how they come out. Probably will be Kevlar and epoxy considering how little material is involved. The Culler oars are looking good and will be ready to use by the time my brother is ( hopefully ) able to row again. He's expressing interest in rebuilding our 20' boat with a new bottom and geting into the skin on frame as a double to see how we can make it go. I'm glad to see his interest on the rise as well as his spirits. I hope this next medical procedure gets his heart rate under control so that he will be feeling like his old self

 

[DickT]

Stretching Waterline

Glad to see this thread is still going. I'm contemplating plumbing the stem and stern on my boat(pics on posts #296 and #301) to bring the waterline from 16 to 17'. By my gps I cruise in the range of 4.3 to 6.0 mph depending on conditions and effort. What I'd add would be essentially narrow deadwood and would be concave unless I added a lot of filler. I'd keep the keel line flat at the stern, but taper the forward two feet up to the waterline. Is it worth it?

 

[ancient kayaker]

The shape of entry would have to be fair, which means that you would have to add some filler, or the turbulence and extra skin drag will slow you down. Also take care that the fore-aft trim is still OK.

Since the beam to length ratio isn't going to change a whole lot your speed at best will increase by sqrt(17/16), say 3%. Your effort will also have to increae to overcome extra skin drag. Whether that is worth it is your call, but if it means beating the guy in the next lane ...

As an afterthought, I have a 12' canoe, my design and construction, and a 13' plastic kayak that is claimed to have racing heritage. At a level of effort that I can maintain the canoe has the legs of the kayak; but when sprinting the kayak is slightly faster.

 

[DickT]

I'd have a real knife edge if I did it which might have some problems of it's own. I could fair it out but the WL in and out would be concave. 3% would have let me beat the 17' Adirondack Guideboat with two rowing that beat me last year. my time for the three mile course was 32:13.

 

[nordvindcrew]

3%

Remember, that 3% is real but the results are highly theoretical. So many things can go wrong and louse things up. Just as an example, if you start to bow steer down wind, that will slow you down. Also, you are not going through absolutely flat water, wind and waves really mess up all the equations. I'd probably go for it, make the change, and hope for the best. Good luck with the project

 

[DickT]

Well I'm into it now. The bottom was getting trashed dragging over the gravel, so today I ripped out some 5/8 x 1 1/4 HDPE strips and made a full length keel. I'm going to run it wild over the ends and see what seems reasonable to extend the WL. Doubt I'll get more than 8-10" overall. hope it doesn't lay up the boat for too long. I missed a nice day on the water today.

 

[nordvindcrew]

keel

What is HDPE? 8'-10" of waterline could be significant. Look at the Finnish boat back a few pages to see their results. Keepus informed, maybe a picture. I got the rub rails on my Skin on frame boat as well as installing the floor boards. Just some paint and foot stretchers to finish her. It's not the light-weight I concieved initially, but it rows well and weighs less than 100 lbs, so still is pretty easily rowed. I do need to figure out a dagger board for the transom that I can raise and lower from the rowing thwart. The transom blows off terribly with wind off the stern quarter. Next race is the NSWRA North River Race Aug.22nd.

 

[DickT]

WL Extension

High Density Polyethylene. Pic shows stern. Profile not yet shaped.

 

[nordvindcrew]

keel

Dick, the underwater section is looking like a Jersey skiff with boxed garboards. In my mind, I pictured you revamping the entire stem and stern profile. I'm just about to start re-doing the bottom of my 20' boat: a narrow flat bottom and steeply sloped garboard panels. I think I can plumb the bow and stern a bit but won't know until I start to mock it up. I want it to be done for November and the " Nationals" in Plymouth, that is, if my brother is healthy enough to row.

 

[DickT]

I see what you mean about the Jersey Skiff. I took it out late this afternoon with just the stern done and no sanding or fairing. I also cut away the bow a little. There was more drag but it tracked much better and the wave train seemed to look better over 5mph. I'm at 29-30" max beam and 16'6" WL at this point.

 

[nordvindcrew]

racing

Dick, how about coming to marshfield for the river race on Aug 22nd? It's a long hike, but a good race with a bunch of kayaks and not enough rowing boats. 6.5 miles up stream with a rising tide to help you along. Lots of twists and turns and great scenery. Wining time for a fixed seat single would be about 1 hour 3 minutes based on last years times. Look for North river watershed Association ( NRWA ) for info. As soon as the Skin on frame boat is done, I'm jumping on the renovation project on the 20' double ender I built out of fiberglass a couple of years ago. There was great promise there that needs to be realised.

 

[DickT]

Thanks for the invite but I'm committed to a three day energy audit workshop that weekend. I may pass up a race this weekend because of a big family party. I left the same party early last year for the race only to get there and have it cancelled because of TStorm warnings.