Here are two photos of the new mk III float that I have made from foam cut to shape, glassed, filled and faired, and now waiting for the towing arms to catch up before they all get a few coats of paint. 

In its present state, it weighs 1200 gms. With the log unit, it will weigh about 1500 gms. It is 550mm long, 150mm wide and 135mm deep (+ the towing posts). I cannot give a finished weight for the towing arms yet, as they are still in construction, but I expect a total weight of 3 - 4kg (the total weight of the mk II float with its towing arms is in the region of 10kg). I could have made everything still lighter, but the total weight should not be so little as to risk skipping over the waves and entraining air bubbles over the working face of the log, as this would degrade the quality of the data.

David, I can't get into your Box file because my computer says it is not secure and won't let me go there. I wonder if others have that problem?

I was going to upload all the raw data files, and in due course the polars, but I keep having problems with Box and security. It is my intention to make everything available online as soon as I can.

Arne, you will appreciate that most of the first article was written before we did any testing, and it went to press shortly after the testing in Scotland. I have been spending a lot of time running data through Polauto with different filters set up. There are potentially over 1 million filter combinations, but I'm not trying them all!

If you look at the raw data you will find that the performance curves are not quite the smooth curves we would like to see, and in any case tend to flatten in the upwind zone, so there is a range of "optimum" upwind angles for each boat.

I am currently putting together the next article about the results, but I certainly haven't finished yet, and I'm reluctant to put it into the public arena until I have completed it, and thought through the ramifications. What I can say is that the indications are that an optimum upwind angle of around 32-36 degrees apparent is typical for the better performing junk rig variations and for the Bermudan rig we tested on Calisto, a Varne 27.

I did an interesting experiment putting junk rig sail onto Topper which have a free standing mast. I used sails of the same sail area and position of CE. The result showed that flat junk sail cannot compete with the Cat Rig but the camber junk sail can. However, it is important to reduce the number of panels and battens to reduce the weight aloft the little dinghy.

Sailing with Ingeborg’s Tohatsu swung up and down.

Today I had another sailtrip in Ingeborg (no. 27 this summer). Apart from testing the Fan-Up Preventer, FUP, I also decided I would try to detect any speed difference (GPS) between when dragging or not dragging the Tohatsu’s propeller.

This turned out to be less than easy, since I was alone on board, with no autopilot. I soon found that the easiest way to keep a constant drive was to head straight downwind and aim for some mountaintop in the distance. The problem was to keep the boat steady while I moved aft to lower the outboard. Several times Ingeborg rounded up 45° or more and it took time to turn back and pick up speed again  -  and the wind may then have changed. However, I think I hit quite well a couple of times. At one of those tests, the speed was about 3.0-3.1kts with motor up, and it dropped to some 2.5-2.7 with the leg down. On another go, the speed was around 3.5kts with leg up, and 3.0-3.2kts with the leg down.

In other words, at this low speed, the propeller appeared to drag the speed down with about 10%. I noticed that as the speed increased, I had to push on the motor head to bring the leg down and lock it. Now, Ingeborg is 2150kg empty and with a SA=35sqm. Since Weaverbird is fitted with the same motor on a smaller and lighter boat (1200kg, 22sqm?), my guess is that the lowered propeller will have a bigger impact on that vessel.

Btw, I tried to measure any difference between when the propeller was locked (reverse gear) and with it spinning freely. I can’t say I registered any real difference, although I felt a slight tendency to speed up a little with free propeller. I may be wrong on this. I hope to repeat this whole test with a crewmember keeping the boat on course while I handle the engine.

Cheers, Arne

I don't know much about Spot GPS but the internet search tells me it costs $150 per unit, plus an annual fee of $200 per year or $20 per month. Plus another $200 for the weather station. So that's $500 per boat in the first year alone. I'm not sure our members or the JRA are willing to pay for this on "a number of boats". 

I think it only sends your location (not speed) at the preset interval, so speed will have to be deduced from two successive locations and will effectively be an average over the period of 5 mins, or whatever period is chosen. I don't think it will transmit the data from the weather station, so some time after the event someone has to try and match the recorded weather station data (which will require another device to record it) with the GPS data. 

Also, the GPS data will not give you boat speed and direction through the water, only over the ground, so including any current, leeway, etc.

I think the data produced for boat speed through the water, wind speed, and direction, will not be very accurate, and therefore not very useful for comparing the performance of different boats and rigs.

It could be that if lots of members were to fit the same Spot GPS device, and the same weather station, we could over time collect some averaged voyaging data. However, being independent minded folk, I suspect that they would likely fit different units from different makers, and then there would be questions about whether the calibrations of the weather units match, and so on.

Meanwhile, we now have a set of instruments which can be transferred from boat to boat, (so the calibration is not an issue), which can measure quite accurately boat speed through the water, wind speed and direction. We have started measuring the performance of some boats with interesting rigs, and there are more being lined up as we speak. I plan to put an article in the Jan/Feb issue of the JRA mag to discuss the results already obtained.

We are already up and running!