designing a fast rowboat

Tero, the boat looks good.
Do you have more pictures of your boat, was this race in Sulkava?

 

Can you have a small fore deck to keep the water out?

 

As is so often the case, you have a set of conflicting requirements. You want your boat to be as narrow as possible, yet you need at least moderate stability in order to cope with rougher weather. You want light weight, which would suggest low freeboard, but you dont want the boat to be submerged every time it encounters a wave.
Having said that, the requirements are still basically the same as for any row boat. Long, narror, light.
Waterlines should meet at bow and stern, and probably slight rocker as a result. Obviously the craft should be as enclosed as possible - ie decked over - with only a shallow, completely self draining, cockpit for you to sit in. That's if you need a cockpit at all.
PAR's idea of a foil-borne rowing boat is not as silly as it may sound. There's a guy in one of the nordic countires (I think) who was a former olympic rower (I think) who has developed just such a rig. Though I doubt you could maintain the energy required to keep it up (so to speak!) for the sort of distances you're talking about

 

Einar Rasmussen
http://www.aftenposten.no/english/sports/article1161296.ece

 

ah - yes - that's the one, thanks Raggi.
Sorry - it's a paddler, not a rower....

 

I took your criteria and came up with this...my interpretation of your numbers, tho it is a bit longer at 21' 4". A picture is worth a thousand words so here's my grand

Steve

 

Yes, there should be a suitable length window.
John Gardner in his book "building classic small craft , mentions that the old fisher folk considered any boat under 16' as unsafe at sea. Racing Whitehalls were built up to 25 ' , but most working Whitehalls were 17 to 18 ', but rowewd in protected bay/ harbour waters.
The Bailey whitehall is 16' 8" and considered by Gardiner as beign the best example of a White hall still around today ( built +-1870).
The St lawrence river skif were built 21' and 42 " wide . And was known as an extremely sea worthy boat that could be out in a gale. was used as a fishing boat , rowed by a Gilley for rich pleasure fishermen, upto 30 miles a day.
Lucien Fry daughter of a famed St Lawrence builder, claims to have rowed accross the river in a gale , and commented on visiting Norway oslo museum where large burial boats ,that lookin from the bow aft at a them the lines were identical to those of a skiff (smaller of course)
All thes boats were rowed on the gunnel.
so lets say 16' to 25' but that open water mieght need a boat that is more manageable.
I'd settle for 19' to 21' for two, perhaps a bit less for single rowers.
Width, hmmm.
water line as narrow as possible for the weight . nice clean following lines , fine in the bow and finer at at the stern.
Deck width.
you need the oarlocks to be far enough apart to give a reasonable power to the oars./// or you need to have small outriggers .
all these would go for fixed and sliding seat.
perhaps riggers a bit further apart to accomodate the power from a sliding seat.
I searoiusly investigate the lines of a St Lawrence river skiff held at Mystic seaport.
Mike

 

Nordvincrew, Great thread, showing often you have to look back to move forward! as in looking at old boats design rather than the bad rowing pun I just realised I wrote. I've got no usefull input as to the design except that I've got a puffin pacer set up to row, the ergos are a bit wrong as to seat(centre case) height to rowlocks & needs a skeg or small rudder to help directional control in following waves/chop etc.All the best in your rowing endeavours from Jeff.

 

Steve @ lewisboats, on one site, it states "rowing into the future with our backs first" or something like that. Your design is very much in line with what I'm working on but with a transom and a more plumb bow to maximize waterline length . Decks fore and aft will help seaworthyness. they will present a problem at times because on one of our races we are required to have the boat stern up on the beach and at the start, race bown the beach, push off the beach and get into the boat. This in early March with water temps just above freezing. Not a good time to have wet feet, or try to row with heavy rubber boots. The old designs are very good, but it seems like designing and rowing your own boat a bit of a sickness. Our two boats are self designed and people constantly ask us who designed them. It seems that many people are incapable of believing that you don't need to be a big name designer to come up with a good boat.

In response to an earlier part of this thread on my question about planing; I know that true and complete planing is probably not possible in a rowing boat, BUT we row against a stretched Gloucester Gull, and at speed, it is clearly trying to climb on a plane particulary on the power stroke. It is confusing to me how this boat rows so well. It has a flat, rockered bottom, hard chines and gives up a lot of waterline length to bow and transom rake. All of which seem to fly in the face of what "good design" suggests is absolutley necessary for an efficient hull. This is what makes design so interesting, there is theory and reality and sometimes they come together, and sometimes they don't. Just as a further issue of confusion: what happens when a 2' chop is working against the hull and at times all parts of it are in contact with the water. Just more grist for the mill to grind on. Jeff

 

Off topic, but conservative Norwegians say something like "when you are rowing you need to know where you came from (to arrive at your destination)".

 

Design efforts so far

Here are the two boats we currently race. Brother Dave and I designed and built both. Hope the pictures will stimulate some comments and show that my thread is based on real boats. Jeff

Rats, I wasn't able to upload the pictures need help to do this

 

Sulkava races are long distance, 58 km. Not rowed there yet. This boat is optimized for shorter courses like 2 and 10 km.

 

update on fast rowing boat: we have made the decision to create a 20' double ender from our original mold. 2 bow sections 8' long will be joined with a fabricated mid section 4' long. We will be able to take a lot of the excess rocker out of the hull and have good waterlines for a clean entry and exit. waterline beam will be 38" on a waterline length of almost 19'. construction will be hand laid fiberglass; 1-1/4 oz. mat 10 oz. cloth and 1-1/4 oz. mat.
bare hull weight is projected to be 94 lbs. Our current 16'8' boat from the same mold has us up to 96% of the time of the only boat that beats us consistantly. This boat should get us up front. Launch is scheduled for mid/ late August. Will keep you posted with results. many thanks for all t5he advise and suggestions

 

Update on new boat: it is being molded in 3 pieces and then joined together midship to create the new hull. 2 pieces are molded and I'm prepping the mold for the third section. Bare hull weight is going to about 100 pounds and our goal is to add as little weight as possible to finish it and get it race ready. looks like it will be ready sometime in September. Will post pictures as it progresses

 

Nord;
Early on you said that wind was a serious factor at your race venue. Have you considered streamlining above the sheer line? The purpose to reduce aero drag induced by the oarsmen themselves. You can pull this off with some thoughtfully designed framework covered with fabric. It will be possible to mitigate the crosswind effect somewhat also. You have probably considered feathering oars when going to windward/not feathering downwind.

Bolger has done a 21 footer that he called "cruising rowboat". It is the most streamlined rowboat in seven counties. Your racer should not be like the Bolger cruising boat but it is worth a look. See the boat in his book; Boats With an Open Mind.

I have rowed and paddled aplenty and wind along with rough water have been heart breakers and weary makers of the most disappointing kind.

We're anxious to see your pix.