designing a fast rowboat

variable seems good

I got an excellent response from Dick Dreissigacker at Concept2 Rowing (http://www.concept2.com/us/oars/selection/oarlength.asp) and have re-posted it below.

What I'm starting to get is that there's a conflict between ideal efficiency (long oars, wide span), and practical constraints which limit oar length for a given design of the kind we're discussing. And a limited oar length can dictate beam for a clean-sheet design.

As well, and I need to look into this, having an outrigger which can be adjusted for horizontal angle, oarlock angle, and span seems highly desirable. As would oars with some adjustment for length. No matter how careful my design, I may need to tune.

From their web-page:

From Mr. Dreissigacker's email:

 

Thanks very much for the recommendation. I found the book on Amazon, but the lone, short review stated it was "Very helpful information for fixed seat row boat construction and operation,” and I'm interested in building a sliding-seat design.

I'm really looking for reassurance that I’m getting the highest possible efficiency out of oars and rig. This thread has been for about hull design (and even propulsion methods), but I’d love to learn more about oars and rig. What I’d like is to be able to row a decently long and narrow hull for an hour at 1/2 to 3/4 effort, and feel I'm getting the most speed and distance for that energy. By the way, Dick, I'm learning a lot from the Concept2 web page. It's well made, and full of useful knowledge. Thanks very much.

However, I'm wary that expertise about competition rowing might skew my boat or rowing rig design away from a more civilian application. This isn't a knock, or even a complaint. Again, I'm grateful for your help on this list and the expert info on your web page. But you guys market to racers.

Here's two examples from your web page about optimizing that would be better for competition, I think, than for me:

Racers need much higher stroke rates than I will. I think that means a lighter pull / less torque, though they generate more power as their rate of work is higher. And while I love the beauty of wood oars I think I want less weight. But I don't think I need something optimized for high stroke rates. So I'm getting the impression that my ideal span (and oar length) are longer than what's 'typical' for competition, for someone my size. Possibly, my ideal oar is longer than anything you, or any high-performance manufacturer, sells. It may be hard to find. I’m also under the impression that a light, high-performance oar balanced with weights in the handles would be a pleasure to use (assuming weight is not a priority). I've never tried something like that, but imagine that at relaxed stroke rates, it would be great.

(I’d love to hear impressions and advice about weighted handles combined with light oar shafts from anyone experienced with them).

I’d like to look again at your web page’s ‘General Recommendations’ for oar length:

“The more efficient your blade, the shorter your oars should be to keep the load reasonable.”
Hmm. I’m under the impression that high performance blades can be a bother for casual rowing in any kind of chop. I may need something I little less razor-edged. That also suggests a longer oar.

“The slower the boat you are rowing, the shorter your oars should be.”
I want a relatively light, long fast boat, so that suggests a longer oar too.

“The narrower the spread of your oarlocks, the shorter your oars should be.”
I’m taller, so I need a wider spread, so I’m going to need longer oars.

“For sculls, rowing with less overlap of your handles, the shorter your oars should be.”
I feather my oars, and don’t mind overlap, so I’m going to need a longer oar.

“The longer your reach, or more specifically, the greater the angle of your oar at the catch, the shorter your oar should be.”
Well, if I have wider than usual spread, and I set up the seat for comfort, catch angle is likely to be reduced, so this suggests a longer oar as well.

I think it's possible all you stud iron-butt gunwale-class guys have driven the sliding seat rowers off this thread. Fair enough, it's your thread. I hope I cause no offense by wanting to learn more for my own desires.

 

I started out as a traditional fixed seat rower, i like the boats & its what i grew up with, now i build them as well. Having started a club from scratch 8 years ago i met a lot of people & made a lot of friends. One thing i did notice was that beginners tend to want to have a go at fixed seat & sliding seat & have no predjudices about either.
On the other hand some rowers from both disciplines are often dismissive to the point of rudeness about the other, its kind of ironic that high performance guys into sliding seats can sometimes be this way & yet the sliding rigger that represented a real step forward in technology got banned!
Hell i just like rowing & find it all interesting!
As for sources of info heres a link for you, http://users.ox.ac.uk/~quarrell/,
Rachel quarrels rowing service, though predominantly fine boat orientated it has links to all over the place including a lot of technical & physiological stuff

 

I think the best approach for open water rowing is exactly what Nordvind suggests, seat of the pants. This seems to be because we have a lot more variables going on...many more boat shapes, traditional or modern, and sea conditions that are more variable than a sculler would take on. So maybe that is why I took the approach:

--rowed a number of boats. 9' oars felt right to me when used on boats that called for 9' oars based on the SHaw and Tenney formula.

--I designed Drake to have a beam that would give me the oarlock span (using folding outriggers) that got me a 9' oar.

--I am 6'6" so my oarlocks are like 15" aft of aft edge of seat. Thwart is only 5 inches above my heels, I think.

--My blades are long and narrow because I am rowing fixed seat and do not feather. So the long and narrow blade is OK when it is windy. I am altering my blade design to be slightly shorter and wider, however...5" x 34" for my open water oars.

--I am designing a short wide blade, hard pulling oar for off the wind, or following sea conditions.


Rowing Upwind SRR 2010 by Clint Chase Boatbuilder, on Flickr

 

Blades, Boats and speed

Hi dcnblues, you could try biorow.com but be warned Although he seems to be very thorough, some folks dont always agree with Dr Valery Kleshnev.
He is very approachable, and all his studies and tests are reported, and his focus is on sliding seat , both sweep oar and sculls.
On the 29 September he published an interactive rigging chart that might interest you.
Be prepared to do a lot of technical reading.
mike

 

Fwiw

My boat is 17', oarlock spread is 45", stretcher to lock is 15". Oars are fixed pin 9', inner looms 24", 15" blades 7" at tip. I sit on a concept 2 erg seat spaced up about 4-5" above the bottom board.

I'm 5"11", 63yrs old. I did 3 miles in 33 minutes last summer. I doubt I'd be any faster with a sliding seat given that there's only so much gas in my tank. I also shredded the MCLs and ACLs in both knees skiing 5 weeks ago and though I'm using the erg for rehab, I doubt there's sliding seat rowing in my future.

I keep coming back to Steever's book, but I found it invaluable dialing in this boat. Like Clint I'd like to try short wide oars and and also some really long downwind "elephant ears".

 

I hope you don't mean me, I'm not dismissive toward anyone on this list. I just want a sliding seat on my boat. But I must confess a desire at some point to try one of those aussie surf boats. That looks like buckets of scary fun!

I was pretty shocked to read about them banning the sliding rigger in the early 80's as well. Very disillusioning. Up there with the Olympics stripping medals from pot-smokers because it's a 'performance enhancing' drug. Seriously? Does the Olympic committee have any clue how bad / stupid they look with that policy in place?

Another great movie I saw on the same theme, and I think the homebuilder / tinkerer mindset prevalent on this thread would really enjoy it, was 'The Flying Scotsman' the story of Graeme Obree (http://www.imdb.com/title/tt0472268/) who built a bike himself, set a world record for distance in one hour, and kept getting disqualified by corrupt industry scumbags. Sorry to dip off topic...

 

Mike, thanks for the link. Leo sent me the same one. Yeah, lots of technical data to wade through. I need to actually crunch some numbers and post what I get, and will do so as soon as I can. I keep coming back to competition ergonomics needing more speed, less effort for fast competitive sprints. I want a slower, more deliberate power stroke. Less total arc, easy pace, relaxed return motion. More torque, less HP.

I'm 47, and reasonably experienced, reasonably out of shape. As I've said, not interested in racing, so not needing to optimize for max boat speed or being able to sustain max boat speed seems to suggest a longer spread, and oar than the numbers I'm getting.

Most numbers I've found suggest a spread of 162cm, or about 5.3 feet. I think I may want some custom-made outriggers that push that to 6 feet (ideally with the ability to adjust inward if I find wider is not better). Most oar calculations end up just shy of ten feet, so I'm thinking of pushing that 10% to 11 feet. Don't know if I can find any that long, will wait until I'm ready to build to research further.

I would like to find out more about putting weights in the handles though. I imagine that's nice.

The other x-factor is whether modern high performance blades will take more concentration than I want to spend to drop into the water. The feathering doesn't bother me, but it's been about six years since I had a shell out in choppy water, and I can't remember what kind of oars I used. Too much effort to balance the shell, wasn't that fun. Frankly, the rowing motion on shells is too easy for me. I can barely feel any resistance. Might as well be doing aerobics with no weight.

 

Clint, thanks for the help. Your boat's very pretty. I suspect that what will end up happening is I'll build myself a too slender, not-enough-rocker speedster that won't like rough water and I end up being limited to taking it out at dawn. Oh well, could be worse.

Dick, thanks as well, and I also like your boat. Can you clarify whether Stever's book covers sliding seats? One review suggested it didn't, and I didn't get the impression it covered lighter high performance oars either. If that's not accurate, I'd like to know. I'm also curious why, with your resources, you're using heavier wood oars without so much as grips on the handles. Clearly the wood must feel good in your hands, but is there anything negative about racing oars that eliminated them from your boat? Perhaps it was just a dimension thing. I'd like to know.

 

At first glance it does seem stupid, but:
(1) The Olympics are not always about having the most up-to-date technology.
(2) If sliding riggers were allowed, all competition boats would have to be retro-fitted because they wouldn't be competitive otherwise.

Similar arguments apply to, for example, the use of fairings on the front of paddling boats, or to better designs for the discus. Olympics are as much about tradition as about breaking records, so there is a lot of inertia in the rules.

Hope you found the "Shorter Oars" paper interesting!

Leo.

 

Leo, yes, I haven't had time to really go through it, but I will, and am very grateful for your sending it [Dr Lazauskas has copyright issues that prevent him (or me) from posting the paper he mentions to the list, but for my individual use, it's not a problem].

I guess I misspoke in that, regardless of Olympic tradition, I'm surprised that the FISA 'World Rowing Championships' limit the technology at all. They really should have, if nothing else, an 'unlimited' category for new technology. My opinion, however, is uninformed and I don't push it very strongly. Thanks again for your links and help. I'll be posting more when I have some numbers to share.

 

Radical new equipment (in rowing) is often rejected out of hand by Olympics' committees. In general it must first be used at World Championships or other major, nominated events.

I agree that there should be some unlimited competitions, but whether FISA should be involved is another matter.

There are many other competitions that cater for human-powered vessels of all shapes and sizes. I doubt that a rowing shell with sliding riggers would be competitive against many of those beasts.

 

cruising

I keep coming away confused by dcnblues. It seems that you want to be able to use your boat in a variety of conditions and want to cruise at a pretty fast rate but not actually race. On any of my boats, about 3/4 of top speed is easily reached at a very modest effort. getting the last 1/4 is what kills you. To me, all your angst about perfect spread ect. doesn't make sense. You will get to fast cruise speed even if yor set up isn't perfect. Pick your boat then set it up as right as you can, using all the PRACTICAL advise and forgetting all the high tech stuff meant to wring the last 1 one 100th of a knot out of a racing shell. A couple of posts back, you were given some good advise: get out there and just enjoy rowing.

 

Sliding vs Fixed

Dick, thanks as well, and I also like your boat. Can you clarify whether Stever's book covers sliding seats? One review suggested it didn't, and I didn't get the impression it covered lighter high performance oars either. If that's not accurate, I'd like to know. I'm also curious why, with your resources, you're using heavier wood oars without so much as grips on the handles. Clearly the wood must feel good in your hands, but is there anything negative about racing oars that eliminated them from your boat? Perhaps it was just a dimension thing. I'd like to know.[/QUOTE]

The book is primarily of interest to fixed seat/pin applications like Adk guideboats, St Lawrence skiffs, and ******* one off hybrids like mine. However, I think you are dividing the world into fixed seat and sliding seat as if they have little in common. Slip, surge, blade tip design, length, etc.as concepts can be applied in either case.

I'm not sure what you mean by my resources(I bought the erg used for$100) but I'm not flush, and nice lightweight racing oars would cost many times more than I have invested in materials. I made pretty much everything by hand to be able to afford to enjoy this fun activity on a limited budget and also to get a good fit.

The oar handles are weighted to offset the short inner loom using Steever's guidelines. I'm not his agent,BTW, but I found he answered questions I had and introduced concepts I didn't know existed.

 

Hi Folks,
We should remember that the weight of the oars while very important, should be considered in relation to where that weight is.
The oar would be easier to row with if the weight was brought inboard,, using the same principle for setting the speed of a grandfather clock, ."move the weight closer to the pin point , and the easier the oar will rotate.
Biorow .com,,,, I think that everyone on the group should read what dr Valery Kleshnev publishes. He is thorough and not afraid to publish the result if his research . The research focuses on sliding seat but the methodology is applicable to fixed seat as well.Purhaps someone should ask him if he'd like to do some work on fixed seat rowing,,, he's really very good
DickT, your boat looks great, seems to remind me of the Herreshoff/Gardner row boat, which has a very good reputation. i also have a copy of Steevers book,, I am looking to make a pair of oars myself, and am trying to source wood in my country, i'd be interested to know what weight your oars finish at?
Just to keep the record straight , I am 67 this year and for the past 4 years have been rowing a skinny sliding seat , but am looking to build a more friendly (stable) boat this year, I kinda fancy something like and old American wherry of 190something. I'll be using macons , dont like cleavers.