I was delighted to read in his "Travels with Paddles" blog that the highly respected coach, Axel Schoevers from the Netherlands, has discovered Flat Earth Kayak Sails! In his enthusiastic write up of the sail he writes "The sail was reviewed in issue 22 of Ocean Paddler Magazine and that article didn't mention or even hint towards the, for me, most rewarding part of the sailing: tracking by edging!"
The first people I saw sailing sea kayaks here in Scotland were all experienced sailors or windsurfers but recently non sailors are discovering the delights of sailing a sea kayak. So I thought I would give a few pointers here to help those who are new to sailing, which might also explain why I did not mention controlling the track of a sailing kayak by edging in the OP article....
As Flat Earth sails become more common, photos and videos are beginning to appear on the Internet, usually with the kayak being sailed with a lot of edge and the paddler in a trailing low brace position. Additionally, some videos show the application of frequent stern rudders to keep the kayak tracking straight. In contrast, Gnarly Dog's video shows his kayak sailing upright and the paddler still paddling!
In all the photos below, David and I are sailing with the kayak upright and as it was me who wrote the article in Ocean Paddler, why didn't I mention controlling the tracking with edging? By his own admission, Axel is not a sailor and as an expert kayaker, he is trying to use a kayaking technique to control what is now a sailing craft. In contrast, I have only been kayaking for 11 years but like David have been sailing for over 50 years (everything from 38foot yachts to windsurfers). Sea kayak sails are very small, about a third of the smallest windsurfer sail, and they operate close to the waves, where the airflow is disturbed, so they need to be sailed efficiently and this requires some understanding of sailing technique.
When sailing any craft, you want to keep the airflow running from the front of the sail (luff) to the back (leach). As soon as you lean (edge) a kayak downwind (to leeward) the airflow is disrupted and starts to run up the sail, as in the top two photos. If you lean into the wind (to windward) the wind tries to run down the sail and escape from the bottom. It takes a while for the proper airflow to reestablish and in doing so, the centre of effort in the sail is moving all over the place, further upsetting your trim and where you want to go!
Every time you edge (or lean) you will loose speed as you have stalled the normal airflow. If you maintain edge for any length of time, in your effort to hold a course, you are creating extra drag and cutting your speed. Since the main point of kayak sailing is to go faster, it helps if sail, skeg and hull configuration are as efficient as possible and are working with each other and not against each other.
So in sailing, you want to keep the rig as upright and steady as possible to keep the wind flowing aft across the sail. In a sailing kayak you steer a course by a combination of sail sheeting angle and skeg. You start with the right sheeting angle, which generally means that you let the sail out as far as possible, without allowing the wind to get round the leeward side of the luff. If you are not a sailor you can thread a piece of fine wool through the luff half way up the mast and about 15 cm back from the leading edge. When the sail is let too far out, the airflow will be going up, when just sheeted in enough, the airflow will start moving back and the telltale will be horizontal.
If you sheet out more than this, the centre of effort will move aft in the sail, if you sheet in more than this the centre of effort will move forward Incorrect sheeting will altering the balance between rig and skeg and make it more difficult to hold your desired course.
If you want to sail with the wind about 90 degrees to direction of travel (beam reaching), you trim the sail as above then adjust the skeg to maintain tracking in the right direction. Move the skeg up, if the bow of the kayak wants to go down wind, or move the skeg down if the bow of the kayak wants to go up wind. On both my Quest LV and Nordkapp LV, the balance is so sensitive that I move the skeg slider only a few mm at a time.
With practice you can even sail the Flat Earth rig upwind (at about 45 degrees off from the direction of the wind). You can only do this if you keep the kayak upright. If you edge the kayak, when close hauled to the wind, you will stall the sail and lose speed and then you will need to paddle further off the wind to get going again.
Watching some people new to kayak sailing in Scotland I can always spot the non sailors. The better kayakers try to maintain tracking by edging, those that do not have effective edge control end up using stern rudders.Every stern rudder slows you down, so its much better to get the sail/skeg trim right in the first place. It's all about balance and the kayaker now needs to think as a kayak sailor!
If you are sailing downwind, either broad reaching (wind 45 degrees behind) or running (wind behind) in waves then there is still a place for a quick use of edge or stern rudder to give just a momentary correction of direction. However, when the sail is correctly trimmed and set, it makes the kayak more directionally stable (even in waves) so you will find you need less stern rudder and edge than without a sail. In fresh winds in these conditions, you will be travelling much faster than without a sail and you will find that the kayak responds by turning a given amount after applying much less edge than you are used to. However, I like to use only a minimum of edge, to keep the sail steady with good airflow.
I was doing 14.4km/hr here without paddling, note how vertical the kayak and sail are. This is broad reaching and without the skeg, the kayak would have weather cocked strongly. I adjusted the skeg to hold my chosen direction but as I also carried on forward paddling (then my speed went up to 17.2 km/hr) I could also maintain direction by adjusting the power on each side.
This is broad reaching in a fresh wind, which is gusty. David keeps the kayak vertical and when the gust hits the design of the Flat Earth Sail allows the roach (top rear) of the sail to twist off, spilling wind and so not overpowering the kayak. In most conditions, you do not need to spill wind by leaning the kayak to leeward and supporting yourself using a trailing low brace (as in the second top photo).
This was paddling up wind, just far enough so that we could bear off, put the sails up and cross to our destination close hauled, sailing as close to the wind as possible.
David and I are now setting off sailing close hauled, note the vertical kayaks. Sailing close hauled is the most tricky course in kayak sailing. We are in the process of adjusting the sails to our course. David has eased his sheet until the luff has just started to collapse with wind getting round behind the mast, then he will pull it in until the luff just fills. His sheeting angle will then be similar to mine. My bow is a few degrees closer to the wind than David's and the luff of my sail has started to collapse. I would lose speed if I pulled the sail in any tighter than this, so I will ease my skeg up a little to allow the bow to move away from the wind a couple of degrees to match David's heading. As we cross the loch, the wind direction will be changing slightly all the time, so we will be continually testing how high we can point into the wind without the sail stalling and losing speed.
David sailing close hauled when a gust has just hit him. Gusts have most heeling effect when sailing close hauled into the wind. However, David has resisted the temptation to lean the kayak to leeward and use a trailing low brace. He carries on forward paddling, note the kayak is vertical. In the gust, the mast has moved aft along the fore and aft line of the kayak. As the gust hit him and the elastic in the fore stay, which holds the mast up and forward has stretched. Together with the cut of the sail, this allows the roach to twist off reducing the power and heeling effect of the sail. David is still travelling fast.
Another broad reach in a not very strong wind but I am doing 9.7km/hr (without paddling) as I am sailing efficiently. Note the vertical kayak. When I resumed paddling, I was doing 14.5 km/hr.
This is close hauled, I am pointing into the wind as high as I can without slowing down, I am about 45-50 degrees off the wind.. I would not sheet in any tighter than this in an effort to point a few degrees higher. I would slow down too much and also stretch the elastic in the fore stay pulling the mast back (as in the gust photo of David with the red and blue sail above). I have experimented with removing the fore stay elastic to allow a closer sheeting angle (without the mast raking back) but I found the rig was much less forgiving in gusts. The elastic also helps prevent gear getting trashed if you capsize in surf, especially near the beach....
Here there is a small swell, I paddle upwind first so that I can then bear off the wind, put the sail up and broad reach to my destination.
In this photo I have lifted my port edge and this would normally cause the bow to swing round to the left. However, when sailing at this speed in the Nordkapp LV and Quest LV, lifting the left edge causes the bow to go round to the right (this might not happen with all kayaks). I am sailing diagonally down the waves and in this case I feel I am just slipping off the back of the wave, so I am bearing off to pick up speed on a broader reach and hopefully stay on the wave. (At the same time I would normally paddle a little harder as well, but I was taking the photo!)
Broad reaching in waves is the fastest point of sea kayak sailing. So far, my maximum speed has been 24.7km/hr in a P&H Aleut Delphin, see video below.
One problem when sailing in stronger winds is capsizing when launching the sail. The safest way to do this is to reduce the apparent wind acting on the kayak by paddling downwind as fast as you can. Launching with the sail on a dead run (with the wind directly behind you) can also be tricky as the full area of the sail is exposed and fills as soon as it is launched. The best solution is to paddle on a broad reach (wind blowing about 45 degrees from the stern). I mark my sheet so that I can see where to cleat it so that on a broad reach only the rear half of the sail fills with wind. The luff (front) is back winding with wind getting round the lee side of the mast (side away from the wind). This sail sheeting position allows the sail to spill wind.
Once I am travelling fast preferably surfing on a wave, I quickly pull the uphaul and cleat it to launch the sail. I put in another couple of paddle strokes to get the speed up again then I sheet in the sail until the luff stops collapsing. Once the sail has settled I then adjust my direction, retrim the sail and adjust the skeg. You can see all of this in the above video.