Minimal drag float/ama for a marathon racer

[Skip Johnson]

Over the years I've designed a number of marathon racing canoes, primarily for the Texas Water Safari (TWS) , mostly 4 and 6 man craft and some solos and tandems. In the beginning it was straight Autocad with some autolisp routines and seat of the pants. Then Leo Lazauskas published Michlet/Godzilla and it turned out that I'd made some lucky guesses in those early designs ;-).

With Godzilla its relatively easy to optimise a design for minimum drag for a given displacement and speed profile. Speed profile is important because designing to a specific speed can lead to a drag curve that shoots up past the design speed. It's better to have a speed profile with a fast cruise speed (~80% of the time and a sprint speed for the other 20%).

In the last few years I've started designing some craft for the MR 340 race which is a far different environment. TWS, "worlds toughest canoe race" follows the San Marcos and Guadalupe rivers some 260 miles from San Marcos to Seadrift and is characterized by numerous portages, class 2 and 3 waters, log jambs and an open bay crossing. The MR340 runs 340 miles from Kansas City to Saint Louis on the Missouri river. No portages, log jambs or bay crossing but a wide often debris laden river with its own challenges. Little wonder that different craft have evolved.

The first boat I designed for the race was a three person craft meant to do well but not necessarily win the race. It was an outrigger and fulfilled its function. Since then I've been introduced to the pedal/paddle powered craft that have developed from some pedal/propellor craft. The pedal/paddle boats are a better match for the condition on the river. First boat of this type I was involved with was to design a new hull for a three man craft. The Kraken did well but suffered from a lack of time to train for the crew and the existing amas were suboptimal. The client wanted to switch to a two man craft and expressed a preference for a catamaran. I was very hesitant to do a catamaran believing that a catamaran would never overcome the ~41% penalty in extra wetted surface all else being equal. But when I ran the numbers through Godzilla the catamaran had a slight advantage at the required displacement and speed profile. 'Contempt prior to investigation ' strikes again. But the boat did well on two hulls and brings me to my current dilemma.

I've now designed a new solo pedal/paddle hull for the MR340 and would like to really optimize the outrigger(s). I haven't been able to get Mitchlet/Godzilla to run with extremely low volume outriggers. The best I've been able to come up with to date on my own personal paddle proa some years ago and the the first three man boat for the MR340 was to shape the outrigger like a destroyers hull as the speed length ratios are similar. I'd appreciate any recommendations for a better/different approach.

 

[portacruise]

Rick W. seemed to like pontoons or tri designs in some of his fast boats.

Check out this page on the flex shaft drive systems and some pics/ vids. Flex Should help with "a wide often debris laden river" as the prop will quickly crawl over most debis or just below surface rocks and self adjusts to surface piercing @ shallows. Difficult tangles can be undone quickly with Rick Wiloughby's pictured design where the prop is within hands reach. Rick used the concept to build a pontoon style and set the HPB 24 hr time record many years ago, when driven by a strong rider, but it has since been surpassed by perhaps stronger riders.

Rick is and engineer with an intense interest in HPB and if he still has his web page up, may be available for consultation.

G

Post in thread 'Prop Shaft Systems.'

Jul 12, 2009

Rick,
But will it work on 300 plus diesel hp with a vessel that is driving out thru a hard chop and slamming quite a bit??

.....

I am proposing the idea for easily driven hulls that are set up for efficiency. Like auxiliary in a sailing boat. Fewer people are able to afford to run a 300+HP these days.

That said there is no reason it cannot be scaled. The main reason for poor prop efficiency on boats is draft. The curved shaft allows the prop to be easily elevated to reduce draft and work as surface piercing when in shallow water.

Once you have a compliant shaft the...

• Guest625101138

 

[Skip Johnson]

I've conversed with Rick in the past, primarily regarding wingsails, he's competent, knowledgeable and his abilities regarding mechanical systems are superb. He can be a bit acerbic to deal with ;-) The pedal/prop craft for the MR340 are Rick's designs and the locals are going to pedal/paddle style drives as they are better suited to the conditions on the MR340.

For a short period it looked like I'd be consulting on a try for the HPB 24 hour record but that has apparently gone away ;-( Current record I believe is held by a European kayak paddler. The requirements to prepare and document a 24 hour record are quite stringent.

What I'm looking for now is an approach to minimize the drag on an outrigger for a marathon type craft. It's a tertiary consideration probably below what the peddler had for breakfast but every little bit helps.

 

[Waterwitch]

Although not very hydrodynamic, would something like a Huki gull work, assuming the crew can keep the boat upright most of the time. The floats only touch the water at 22 degrees of heel. Gull Wing :: HUKI Outriggers, Surfskis and Surfboards https://www.huki.com/index.php?page=Gull_Wing

 

[HelmutSheina]

I was reading about a similar topic today that Joe Dobler wrote about his Triad Skip, not sure if it's relevant, but you will know.

Triad Plans PDF

Triad Plans

duckworks.com

There is also the work Mark Palmquist has done with hydroplaning outriggers.

Plans by Designer - Mark Palmquist - Duckworks

duckworks.com

 

[Skip Johnson]

Although not very hydrodynamic, would something like a Huki gull work, assuming the crew can keep the boat upright most of the time. The floats only touch the water at 22 degrees of heel. Gull Wing :: HUKI Outriggers, Surfskis and Surfboards https://www.huki.com/index.php?page=Gull_Wing

The Huki style outriggers are well suited for use in ocean waves less so on a flat water river.
The issue here is a pedal driven craft will have a high COG even in a semi recumbent setup. Also the minute you put your feet on the pedals you lose your ability balance the craft. I discovered this some 30+ years ago when I built a pedal driven 'jet ski' drive for a run at the Water Safari. A friend who could paddle a K1 kayak and chew gum at the same time (the gold standard for balance) couldn't keep it upright.

 

[portacruise]

Skip, what's wrong with paddling and pedaling at the same time? The paddling would be minimal and just enough to keep the boat upright. Maybe shorter specialized paddles or small hand side rudders could be used to decrease the drag factor?

I got some off the wall ideas, but don't know how well they would work in a "debris laden" river. Debris laden means any floats or foils that touch the water have the potential to strike/tangle and turn/slow/stop the boat anytime one side or the other strikes a floating/tangling (or just below the surface) obstacle. If there a extended sections of clear water, then hydrofoils or floats might still help with the overall time. But they (and the prop) might need an engagement reducing system. Maybe something so they can be quickly retracted for the debris sections; debris areas presumably would be done by regular paddle only.

Ok, some other ideas the might be less practical, Ha! Start out paddling on the level, then use an leg cranked air prop with a special separate side diverters which can be auto or separately controlled by the rider to keep the boat level with air puffs to the sides as necessary. Also same concept but using water jets. Have no idea if these are actually feasible, but they have the advantage of essentially zero drag and zero engagement with debris.

Hope this helps, just discard if it not be useful to you!

 

[montero]

"My" ideas for multihulls are always quite large beams.
What you're proposing is a tri layout. Maybe look at how they do it at Ph.
They use very long crossbeams and minimal displacement amas.
By using appropriately lightweight materials, you'll achieve high stabilization power with low displacement. For example, a 1:40 ratio. Of course, use optimization software.

 

[montero]

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[Skip Johnson]

Skip, what's wrong with paddling and pedaling at the same time? The paddling would be minimal and just enough to keep the boat upright. Maybe shorter specialized paddles or small hand side rudders could be used to decrease the drag factor?

I got some off the wall ideas, but don't know how well they would work in a "debris laden" river. Debris laden means any floats or foils that touch the water have the potential to strike/tangle and turn/slow/stop the boat anytime one side or the other strikes a floating/tangling (or just below the surface) obstacle. If there a extended sections of clear water, then hydrofoils or floats might still help with the overall time. But they (and the prop) might need an engagement reducing system. Maybe something so they can be quickly retracted for the debris sections; debris areas presumably would be done by regular paddle only.

Ok, some other ideas the might be less practical, Ha! Start out paddling on the level, then use an leg cranked air prop with a special separate side diverters which can be auto or separately controlled by the rider to keep the boat level with air puffs to the sides as necessary. Also same concept but using water jets. Have no idea if these are actually feasible, but they have the advantage of essentially zero drag and zero engagement with debris.

Hope this helps, just discard if it not be useful to you!

First rule of marathon canoe racing KISS.

A pedaller even recumbent has such a high COG that you either have to go quite beamy or use stabilizers. Compounded by the fact that all sense of balance disappears when you put your feet on the pedals.

Here's what I believe to be the chronology of the pedal style boats on the MR340.

First was Rick W's pedal/propellor drives on slender outrigger stabilized craft.

Those were converted to pedal/paddle drives which were better suited to local conditions, with the drives behind the pedalars.

Then a 3 man team stretched an existing boat to ~ 40' loa and fabricated a chain drive system that drove a pair of enormous paddles in the stern of the boat, from pictures it looked like a ******* child of a strandbeast. The boat did well but was hard on the paddlers. There was a lot of inertia in the system and when a paddle would inevitably hit something in the water it wreaked havoc on the pedallers knees, one guy finished the race paddeling.

They stripped out the drive system and went with individual pedal/paddle stations which was easier on the knees.

Having squeezed all the goody out of the approach they next thought about building a new hull and contacted me. I was intrigued but hesitant since I wasn't sure I would be able to help them. Then in a discussion about boat speed they said that the boat was faster pedalling out of sync and I immediately took on the design work. If a 40' boat slows down between strokes it's got a lot of unnecessary drag. Hence the Kraken.

After the race the Kraken was retired and the the front two pedallers went back to paddling, the new outriggers I designed for them are doing well in races.

The sternman commissioned me to do the design for a tandem pedal/paddle craft the Karakamaran which also did well and is now being campaigned by a second owner.

The second owner has commissioned me to do a solo pedal/paddle craft which brings me to the current conundrum.

I was responsible for only the hull design for the Kraken, they used the existing outriggers which are surely suboptimal.

Optimised outriggers are way down the list of important criteria, which goes.
Crew
Support team
weight
design (outrigger design just a small fraction of this)
but every bit helps

 

[Skip Johnson]

Traditional filipino bangka boats anchored on gorgeous tropical beach. Travel concept. Palawan island, Philippines. Stock Video

Download Traditional filipino bangka boats anchored on gorgeous tropical beach. Travel concept. Palawan island, Philippines. Stock Video and explore similar videos at Adobe Stock.

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Would be interesting, there's over a thousand boats at the start but it is staggered in two stages. Shore supply along the route would also be interesting.

 

[gonzo]

A pedaller even recumbent has such a high COG that you either have to go quite beamy or use stabilizers. Compounded by the fact that all sense of balance disappears when you put your feet on the pedals.

Pedaling does not necessarily have an excessive COG. Definitely not higher than rowing a shell which can be done without any stabilizers. What makes you think that putting your feet pedals make you have no sense of balance?

 

[Skip Johnson]

Pedaling does not necessarily have an excessive COG. Definitely not higher than rowing a shell which can be done without any stabilizers. What makes you think that putting your feet pedals make you have no sense of balance?

Experience, I've mentioned this some where before.

Some time ago I built a pedal driven solo craft with a large volume jet drive for a run at the Texas Water Safari. The hull was a moderate design, fairly flat bottom quick cruiser style. When you took your feet off the bottom of the hull and put them on the pedals all sense of balance disappears, apparently there's more connection between between your feet and the boat than I expected. A friend who could paddle a Olympic K1 and chew gum at the same time (the gold standard for paddling balance) couldn't keep the boat upright. FWIW the boat ended up with a pair of small outriggers and was DQ'd from the race for not making a checkpoint on time a quarter the way thru the race due to the hassle of multiple portages with an overweight boat.

Also a rower in a shell has his heels fixed at a point below the waterline while the pedaler ends up several inches higher due to the geometry associated with the circular motion of the pedals. Look at the guys on the Kraken.

 

[gonzo]

Experience, I've mentioned this some where before.

Some time ago I built a pedal driven solo craft with a large volume jet drive for a run at the Texas Water Safari. The hull was a moderate design, fairly flat bottom quick cruiser style. When you took your feet off the bottom of the hull and put them on the pedals all sense of balance disappears, apparently there's more connection between between your feet and the boat than I expected. A friend who could paddle a Olympic K1 and chew gum at the same time (the gold standard for paddling balance) couldn't keep the boat upright. FWIW the boat ended up with a pair of small outriggers and was DQ'd from the race for not making a checkpoint on time a quarter the way thru the race due to the hassle of multiple portages with an overweight boat.

Also a rower in a shell has his heels fixed at a point below the waterline while the pedaler ends up several inches higher due to the geometry associated with the circular motion of the pedals. Look at the guys on the Kraken.

Those guys are pedaling on pedestals. A recumbent setup could put the operator below the waterline. Also, a hull with more initial stability would help even though it may have more drag. The drag of two outriggers has to be higher.

 

[Skip Johnson]

Those guys are pedaling on pedestals. A recumbent setup could put the operator below the waterline. Also, a hull with more initial stability would help even though it may have more drag. The drag of two outriggers has to be higher.

You may be right. The reason I started this thread is to see if anyone has a simple way to empirically prove this or suggest another way to optimize the configuration. FWIW the winning solo and tandem boats are often single outriggers and the hulls are just wide enough to squeeze the paddlers butt in. Such a solo craft beat the Kraken in its final race; an empirical proof that design is a tertiary consideration.

My function in all these deals is to provide the uber competitive souls with as sharp a tool as I'm capable of. They seem to like it, keep coming back for another one and it's been an enjoyable hobby for me. But I've gotten to an age where my mind is not as quick or agile as it used to be and have quit doing new designs unless it's something really out of the ordinary and interesting. The pedal/paddle craft have developed to the point that they have the potential to set some new standards in open flatwater marathon events. I'm a sucker for that kind of stuff.