I had opportunity to sail in 15 knots average wind (confirmed by checking the average wind speed recorded at Trondheim harbour weather station at the time) and a wind direction that gave about 10 nm fetch, resulting in 20 - 30 cm (8 - 12") waves. I reefed again. The water stay was a little loose, and the boat heeled a little to windward when the foil was on the windward side. That reduced freeboard to about 15 cm on the weather side and resulted in a fair bit of water coming in. My crew and I dedicated ourselves to studying the ancient Polynesian art of constant bailing because 5 cm water in a boat only 25 cm deep from bottom to gunwales just does not spark joy.
We started off on the weather tack, and the foil hooked in solidly, and followed the waves nicely. That wave height is far from being a thorough test, but I have not yet seen anything to indicate that the foil would lose its grip. I intended to take video, but the camera was set on picture mode, and because I thought I had video, I did not take multiple pictures. So the only shot I have is very badly framed, but should still be informative.
I did not experience again the foil being sucked down when going downwind, but I did that only when returning to the harbour when the wind had dropped to perhaps 8 knots. I was still going faster than when the foil had been sucked down previously.
I don't know when I will have opportunity to test in more wind and wave. Here is a record of average wind speeds for a year. Of the 10 occasions when average wind speed exceeded 16 knots (8 m/s on the scale to the left) for long enough to show up with that temporal resolution, the one in late October was just barely within the sailing season, the next six were not, and the remaining three were in what is sailing season for others, but exam grading for me. Thursday's 15 knots don't show up with that temporal resolution, so there may be the occasional two hour stretch of more wind not visible on this graph. The point is, I can't promise testing in more trying conditions in less than a year or two, as I may not be able to take time off work when there happens to be wind.
In 15 knots, I could not get the boat to tack without paddling. My crude foil has enough drag that the boat could not get enough speed to sail through a tack, and I think the wide beam does not help, either. It is easier to turn towards than away from the foil, indicating that the centre of drag is offset towards the foil from the centre of gravity. Judging by the wake, I think the foil has more drag than hull and rudder. At one point, I had to do a draw stroke with a paddle from the bow to get the boat around. On the other hand, that confirmed again that the boat is stable when the foil is stalled, which I attribute partly to the foil's volume providing about 60 litres buoyancy when to lee, and partly to the foil's large area. The boat is also stable with the foil to weather and stalled, and thanks to the hinge, the weight of the foil and crossbeam can't do much then.
My crew had not expected the ride to be quite so wet and had not brought a drysuit, so decided to call it a day after one tack out and one back. To avoid a lengthy sail to the upwind harbour entrance, I went in through an entrance that required about 30 m paddling upwind. We could not do it, partly because the offset drag of the foil and mast would have required us both to apply power on the port side, and from the forward seat that is hardly possible because the frame gets in the way. For the aft seat, I have rigged an oar, but I still could not get enough power. I consider being able to get upwind under human power in 15 knots most definitely part of design requirements, and I should be able to do so on my own, never mind with crew.
Preliminary assessment
Stability under full sail with the foil to lee: 10 out of 10.
Stability with a reefed sail and centre of effort low enough for non-heeling with the foil to weather: 10 out of 10. I am now confident enough that I am willing to cleat the sheet in future, freeing a hand for taking better video.
Stability under full sail with the foil to weather: uncertain, having been tested only in light wind. I want to add some more different cases to my stability calculations before I do test that. The low lever arm afforded by the current hinge position (I will discuss the trade-offs when I write an article for Catalyst) might be compensated for by a spring. I will have to calculate that, and there may be an implementation that I can test cheaply.
Speed: 2 out of 10. The foil's drag is too large. I don't know how much of that is due to junction drag and not at all optimised profile, and how much to the large size which contributes to the foil's good manners.
Tacking: 1 out of 10. I attribute this first to low speed due to foil drag, and also to the very wide beam.
Moving under human power: 2 out of 10. The reason is bad ergonomics for paddling. A good oar and an oar lock attached to the frame would be a partial cure. However, with a single oar, I would need the rudder to steer, and would have to think of a way to control the rudder while having two hands on the oar. Also, the foil is always in the water. Given the prevailing light winds, cruising would involve some days under human power, and overcoming the drag of the foil would then be annoying.
Sailing without constant bailing: 1 out of 10. A spray deck should be a partial cure. I have finally worked out how to fit a partial spray deck around this hull and frame, but this really needs a self-bailing or enclosed hull.
Fun to friction ratio: 4 out of 10. The boat is fairly enjoyable to sail, though it does not offer the thrills of a fast beach cat or (I presume, in the absence of experience) a boat that flies on its foils. Nor does it offer the fast tacking of a dinghy. And the bailing distracts from the sailing. The experimentation, the opportunity to find out how a new concept works, is quite enjoyable. That is the fun part. The friction is the ancillary time and work it takes to go sailing. I takes about 20 minutes to get trike and bike trailer out of the basement, retrieve all the gear, and get it securely tied down. 20 minutes down the hill to the harbour. Once there, an hour and 15 minutes until I am ready to sail, consisting of carting boat and foil to the ramp, getting my gear there, setting up foil, rig, rudder, oar and paddles. The same for getting the boat back to its spot and the gear on the bike trailer. 30 minutes up the hill, then 20 minutes putting stuff away, an extra 10 minutes if I have to rinse off salt water and hang up stuff to dry. So 3 hours 10 minutes organising stuff, plus 50 minutes commute for a total of 4 hours friction every time I go sailing. That makes sailing after work impractical, leaving only weekends. For comparison, when I had a Paradox (the Matt Layden microcruiser design), it took about 15 minutes to get the sail rigged (I kept it inside the boat to protect it from its greatest enemy, sunlight) and the boat untied, and about the same to put everything away. Everything I needed for sailing I could keep in the boat. So 30 minutes organising stuff plus 50 minutes commute added up to an hour and 20 minutes, which made sailing after work practical.
Where the current iteration has poor scores they mostly seem to be fixable, primarily by designing and building a better foil, combined with either a self-bailing or an enclosed hull, i. e. an entirely new boat. Reducing friction enough really requires entirely doing away with the need to transport gear and assembling and taking apart the boat and so is not specific to the concept of the hinged Bruce foiler. I would need a boat large and enclosed enough to keep the necessary gear inside. Given the time and cost needed to build or have built such a boat, further iterations are likely to be radio-controlled models.