Racing Canoe

Rick,
do you think a KM of .38 will be stable enough for canoers to paddle in an upright position on one knee. What type of power could I expect out of an intermediate paddler in this position?

 

Corey
You a building a reasonably heavy canoe and should be able to get most of its weight close to the keel. You could work it out if you take the time.

In a recumbent position I can get my CoG at 0.28m. I think a male seated with legs flat has CoG about 0.4M above the keel. So I estimate that in a kneeling position the paddler would have a CoG above 0.38m.

However this is not the whole story as a paddle gives the paddler the ability to provide dynamic stability. I think a KM of 0.38m would be acceptable for experienced paddlers.

I have not actually done numbers on racing kayaks but my guess is they work with KM around 0.25m. Rowing shells are probably less than 0.2m and the rowers on singles sit above the waterline but then the oars act as stabilisers. You could never ballance a rowing shell without oars. It is quite a feat to get going if you ever watch them dockside.

I think I made the point in an earlier post that experienced kayakers board the boat with it aground and push off with the paddle. You could always fit some outriggers for training until the crew get their rythm.

Even at the 10 minute level aerobic capacity becomes more important than than the muscles actually employed. Hence my original estimate of 200W is still applicable. Off course it will take training to get full value of the lung capacity actually applied to the working muscles.

I think the seating position in an OC1 is close to optimum for a canoe. From my observations it takes less leg effort in an OC1 than the straight legged position of kayakers. I have watched older fellows on one knee and it looks tough work for long duration. Certainly need knee pads. It is slower to switch sides also than being seated.

If you are unconstrained with how you paddle then I would try a few different methods. Maybe a seat about 200mm above the keel with the feet looked into foot straps about 2ft in front probably underneath the next seat.

The other area to experiment is with the size of paddle blades and stroke rate. You need to do some conditing first to get the muscles trained. After that it is a matter of not straining muscles. You should aim to get a good ballance between breathlessness and muscle soreness.

I have done my own numbers on a few older men for pedalling and typically peak efficiency (defined here as power out over heart rate) is at a cadence of 65. However most prefer to operate above this to avoid muscle soreness. For long duration events I work on a cadence of 75 to 80. I imagine the same sort of thing holds for paddling but it is not an area I have delved into.

It would not be very difficult, with the help of a friendly gym, to set up a paddle handle on a rowing ergonometer and test what power can be sustained. By adjusting the drag you will be able to determine what is best for each paddler. You could even try different seating positions. You could then tailor paddle blades to suit. I think they will have to operate in sync though so there should be an agreed stroke rate.

 

Corey
Care to give an update on the canoe performance?

 

canoe performance

Well, now that this years' rules include a hull design by which all schools must build, I suppose it's a perfect time to post on the performance of our canoe last year! We had the 3rd fastest canoe out of 12. I have no doubt we had the best stability of every canoe there. KMT of about 0.45-ish m was more than enough and we were the only team out there paddling up on our knees. The tracking (probably best quantified by the Block Coefficient: ~0.51) was excellent for maintaining a straight line, but the abnormally sharp v-shaped keel at the stern made turning very difficult... but at least predictable and controllable. In hindsight, I would trade tracking ability and stability for better maneuverability as well as improved acceleration. Overall, the boat performed EXACTLY as I had expected. Everything was consistant with the numbers produced by Mitchlet. Finally, you judge for yourself, but I think we had the best looking canoe as well - truly classic!

http://picasaweb.google.com/meeks.corey/ConcreteCanoe

One big resounding HOWEVER, this competition is much more than a technical competition. I think we had the most technically advanced hull design, construction, and mix design at our conference... I know, that's balsy... and yet we didn't even place top 3. We lost points for things such as; going over time on the oral presentation, printing the hull design drawings on 8.5"x11" rather than 11"x17" in the design paper, having capital letters on the canoe lettering larger than the max allowed thanks to the sans-serif font we chose, and not having the material technical data sheets (not the MSDS, we had those). This comes from having only 2 people doing everything, but all these errors could easily have been avoided. So either have a minimum of 3 people doing everything or consider memorizing the 90 pages of rules... which, aside form the few details above, is what we did.

Anyhow, that's the concrete canoe competition... it's AMAZING!!!

 

Corey
It is good to see the feedback. I suppose the hydrodynamic aspects regarding the shape are now set in concrete - literally.

I wonder if the rules allow surface finishes aimed at lowering viscous drag!!

I guess the aim of the competition is technical aspects regarding concrete and project management. Good project management will avoid the little quality issues that downgraded your endeavor last year. It is easy to be cynical over such "trivial" issues but I have seen the consequence of poor quality control on civil projects so I support the lesson in detail that the judges demand.

I have two recent examples. One is a 400mm misalignment in a 400m long wharf due to a small survey error that will have to be lived with forever. The other came close to condemning hundreds of super "T" beams due to a factory notch in rebar used in the beams. If some of the rebar had not been exposed it would not have been possible to identify where the faulty bar was located. All beams would have to be rejected. There was no batch control on the supply of rebar. So you have had an important lesson in quality regarding detail that may prove valuable through your career.

So, along with the obvious fun of the competition and the satisfaction of making a nice boat, you have gained some tremendous experience for future work. You will have to keep us updated on progress this year.

 

Michlet should be at least as accurate for thin hulls. Remember too, CFD codes can be up to one million times slower.

Hope to hear from you in 2525, after your first optimisation run,
Leo.