Rouleur’s canting dagger boards: balancing lift & drag in small R2AK boats

An interesting aspect of helping Matt build his Race to Alaska boat is learning from him, the boat designer Rick Willoughby, and other contributors how important aero- and hydrodynamics are to creating an efficient boat.  When you can only provide ~250 watts of propulsion power (or 500 in Matt’s case), rather than the normal 3600 watts you get from a 5 hp outboard, you need to minimize drag in order to attain admirable boat speeds.

Matt’s boat is version 16 of a pedal boat designed by Rick.  This V16 R2AK is modified for the Race to Alaska in many ways, but one key one is the canting daggerboards.  These foils are designed to be elevated above the waterline so that Matt can pedal without any water drag from them, and then  lowered during sailing to to provide lateral resistance and lift that helps keep the boat from heeling.

When lowered to the maximum angle of about 55 degrees below horizontal, the leeward daggerboard will help with upwind performance.   On a reach it could be raised to provide more lift, while on a run it can again be pulled up clear of the water.

Here are some photos of the dagger boards — both during construction and initial sea trials.

We ended up deciding to shorten the struts from about 63 cm to 58.5 cm LOA.  This allows the struts to come up above the water line (and hopefully many of the smaller waves) and be lowered down to near 55 degrees below horizontal.

Here are the struts after being shortened experimentally to about 60 and 58.3 cm LOA…



It was clear during testing in the lake that the bare aluminum struts were creating a LOT of drag.  Rick explained that fairing them (with a symmetrical foil shape) would reduce the drag by about a factor of 20.  Sailing with them immersed was equivalent to pulling a second Rouleur hull behind us!

Here are a few more photos of the fairing of a second set of struts (made with slightly thicker walled aluminum tubing, too, I think).  This set was faired with cedar, though we may fair the original tube with foam insulation to have a backup (lighter duty) second pair.

The astute reader will notice that I drilled the holes 90 degrees off in the ends of the struts!  This was remedied by re-squeezing the ends (I did this in the vice already without cracking any epoxy, thankfully) and re-drilling (much easier to line up the holes when you’ve got the faired foil shape behind the bit in the drill press!).  Any strength lost from the initial errant holes I hope to regain by injecting silica-epoxy plugs 2-3 cm into the tube ends.

I’m excited to see what these faired struts do for Rouleur’s speed.  So far she’s not quite attained the sailing speeds that Rick expects from his modeling…

First salt water launch and initial speed data

IMG_0325On Sunday (5/22/2016), Team Take Me to the Volcano launched the “V16 R2AK” at the Secret Beach in Ballard, Seattle.  Around 6pm Matt, Mark Dix (Team The Windsurfer, Stage 1 R2AK, 2015), and Scott finished bolting iakos to amas, having leveled the main hull and amas before drilling the final bolt holes in the inboard end of the iakos.  We loaded up the main hull on Mark’s car and the amas on Scott’s and headed (carefully, remembering Colin’s tragedy) down the curvy road to Puget Sound.

At the beach Chris and Mik met us and helped unload onto the sandy beach.  High tide was approaching, so once we re-connected the amas and main hull with some help from Sam (of Team Puffin, R2AK 2015), set up the seat and other gear, it was easy for Matt to pull the boat into the sea.

With Matt aboard and a fair amount of gear, the step out from the lower to upper hull was 95-105 cm above sea level.  We tried loading 50 pounds of weight behind the seat, but thought that pushed the rudder assembly a little too deep.  When Matt was pushing hard the steering arms on the rudder were mostly submerged.  With the 50 pounds removed, the rudder arms were clear of the water (except when waves passed over it).  Overall, it looks like it will be helpful to get some more weight up forward — which of course will happen when the sailing rig gets stepped (just forward of the forward beam).

With the initial trim set and some confidence that it wasn’t leaking, Matt brought the boat back to shore for a proper Christening.  Lisa and Ciana had arrived with champagne and proceeded to help Matt name the boat “Rouleur.”  The beautiful Douglas fir bows were glowing in the setting sunlight, glistening with the recent heavy rains, and foaming with celebratory champagne as we all hailed the arrival of another fine boat on our ocean planet!

Matt then took Rouleur out for another longer spin.  A few minutes after he had disappeared “upstream” toward the Ballard locks, it was an awesome sight to see him blaze bast a couple cruising kayaks.  It seemed he was suddenly off towards Ketchikan at high speed!  But he eased off on the power at the last-minute and circled back to us.  Near the beach a set-screw gave in to the tremendous torques Matt was pushing through the right angle drive, so our sea trials of the pedal propulsion system had to cease.  It was easy to return to the beach with gentle pedaling, and earlier it was clear that the back-up human power method of a SUP paddle was also effective.


Matt takes a seat he’ll sit in a LOT.


The view seaward from the hot seat.



Map of the 2nd test run (w/50 pound weights).


Speed vs distance plot for 2nd circuit.  Cruising speed was 8-10 kph.

The initial speed data suggest that in flat water and no wind, Matt should be able to keep this boat in the 5-10 kph range pretty easily.  Remember for the ~1200 km Race to Alaska, 10 kph mean VMG will get you to Ketchikan in about 5 days; 5 kph will get you there in 10!  Averaging 15 kph 24/7 will beat Elsie Piddock’s record handily; you’ll be there in 3.3 days!

For comparison, when Greg set the world record for distance in a human-powered boat over 24 hours, he averaged 10.22 kph.  Here’s a spreadsheet of long(-ish) distance speed means for human-powered boats.  While sprinting kayaks can hit 17-20 kph, a huge question in the 2016 R2AK — especially if there are extended windless periods — is whether Matt’s cycling prowess and the Rouleur’s pedal-propulsion system can sustain ~10 kph over significant stretches of the BC coast.


Longer 3rd run (50 pound weights removed).


Speed vs distance for 3rd, longer circuit. Top speed was about 13 kph, average about 10 kph!

My favorite part of the evening was seeing Rick Willoughby‘s design assembled and afloat.  The curved iakos seemed to connect in a near-circular arc.  Rouleur seemed perched on the water’s surface, wings outstretched — both embracing the sea and poised ready to streak across it.

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Canting twin daggerboards

One of the unique features of my new Race to Alaska trimaran are the canting dagger boards. They were designed by Rick Willoughby. Not only will the boards provide lift, but they will help counteract the heeling forces from the sail.  I have very low volume stabilizer floats, so this lift will help keep me sailing level in a moderate breeze.

Canting daggerboards near front crossbeam

Canting daggerboards near front crossbeam


The daggerboards can cant from 60 degrees off horizontal to about 10 degrees,  where the tip of the board is clear of the water.  The adjustment is made by moving the inboard end of the brace up and down the guide rod. Originally this control was going to be with control lines, but now I believe I will reach forward and do it by hand. It pays to have long arms.
When sailing you lift the windward board and lower the leeward board each tack.  When reaching both boards could be lowered to provide lift. The boards will also have a friction release of the board on the hinge plate so it is not fatally damaged in a collision. While these foils are not designed to fly the main hull, in the right conditions there will be some lift, and increased speed.
Daggerboard control rods along the side of the hull

Daggerboard guide rods along the side of the hull

Daggerboard hinge plates

Daggerboard hinge plates


Cutting a big hole in my boat

Tonight I tackled the installation of the pedal mast and gearbox. Just another challenging job that I couldn’t afford to mess up. First I had to cut a big hole in the boat where the Mitrpak right angle gearbox will go. The shaft in the photo runs between a pillow block inside the pedal mast, and out to a coupling to the gearbox. The lower 14 tooth cog will attach to it.

Hole for mitrpak gearbox

Hole for mitrpak gearbox

Next I did my best to line everything up




The prop shaft will actually run along the side of the boat. The hole is cut in the cockpit sole which hangs over the main hull about the width of the gearbox.


Here everything is epoxied into place. The Pedal mast aluminum plates are bedded in epoxy, and sitting on a little square of fiberglass. Tomorrow I will fiberglass over the top of the attachment plates for the pedal mast.

The boat: V16 R2AK by Rick Willoughby

Below is a drawing of the latest design by Rick Willoughby. — a custom trimaran or stabilized monohull focused on enabling Matt Johnson to compete in the 2016 Race to Alaska (R2AK).  Rick is an Australian engineer who designed the V series of pedal boats, on of which was used to set a World Record for 24-hour distance attained in a human-powered boat.  Rick has pioneered the flex shaft propulsion system and dipping rudders, and in this R2AK-specific sailing design has also included a centerboard and canting foils.



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Building hulls through the winter

Over the winter of 2015-2016, I stopped by Matt’s house in Ballard a few times to help him build the hulls for his V16 R2AK.  It was a pleasure to work in his recently re-organized shop, in part because I always get good ideas about how to improve the work space in my garage and often get to try using nifty tools — some of which I’ve never seen before!

December 8, 2015

After checking out the table and chop saw work bench that Matt built, we epoxy coated some long lengths of door skin and then started laying out the bulkhead positions for the amas.  I love that Rick’s plans are all-metric!


We used hot glue to tack the foam bulkheads in place.  It seemed to work pretty well, though you had to work fast and together to insert the bulkheads before the glue cooled too much.


The amas have a nice knife-like profile.  Suddenly straight door skin panels start to look like they might move through the water pretty fast…

January 3, 2016

After the holidays we dry-fitted the base of the main hull.  It was tricky to get the longer door skin panels to hold a smooth curve, especially between the bulkheads and near the re-curved part of the bow.


After consulting with Rick, Matt decided to add a few stringers, so we worked together to rip them on his table saw.  I also did some sanding of some a previous epoxy coat that had beaded up in an interesting pattern of stippled patches.  It was nice to have the shop vac set up to filter out the dust.


February 11, 2016

Now the main hull is taking form enough that one can imagine pedaling and sailing within it!


We weighed it and Matt portage-posed with it before settling into the main job at hand: gluing decks on the amas.