H'mmm. From the Sailtracker and PRO Sailtracker app descriptions in the Playstore:

"Sailtracker computes polar based on angle and true wind speed, calculated from apparent wind and boat speed obtained by GPS (COG)"

Not boat speed obtained from a log. This app would only be of use in non-tidal waters, if so, but there may be something lost in translation, the app is of Spanish origin.

[edit] the iOS app 'NMEAremote' appears, as far as I can tell, to include data from the log as well as from GPS, and includes background logging. It costs £18.99, less than PRO Sailtracker.

That's good news!

A few random thoughts:

It would seem to be easy to mount an anemometer on the pulpit, on a short pole attached to one of the commonly available clamp- on antenna mounts.

A rotating cup anemometer would be vulnerable during transportation. A ROWIND Ultrasonic Wind Transducer, for example, or the Airmar equivalent, would be more robust. 

I don't think a transom mounted log impeller will suit many sailing boats. A through hull impeller mounted on a (faired) pole at the bow would put it in clear water, avoiding calibration problems.

Do we need a display head? The Rowind outputs an NMEA sentence - isn't what we need simply two "smart" transducers that output NMEA directly into something like the Anenomind? The Android/iOS app then provides a display, if needed.

A pole that carried both transducers would have to be about 3 metres long - more difficult to transport. Also, Weaverbird needs the centre of the pulpit to be kept clear, to deploy the anchor, and I suspect other boats will have similar restrictions.

So I come to the view that there might be two poles, each 1.5 metres long with an antenna mount that clamps onto a 1" tube (the pulpit, pushpit or a stanchion), with a transducer at its other end. The wind transducer needing no further support, but the water transducer needing an extra lashing or strut, as it will experience more load from the water flow.

Weaverbird can find enough power for an Android phablet, and (marginally) for an iPad. She cannot power a laptop without adding an inverter, and would in any case object to having a Windows device aboard. It would seem that an Android or iOS device would do all that's needed.

Something is needed to take an NMEA sentence and transmit it onwards via wifi/bluetooth to an Android/ iOS device. If not Anenomind, what else is there that will do this? [edit] found the answer - a wifi router 

I'm delighted to see such an interesting range of thoughts on the proposal, and the other plans in the pipeline - see my earlier comments on a small trimaran as a better two boat test bed than a dinghy. Of course, if the two boat idea does happen, they could also be ideal as part of the measurement programme, the same boat with many different rigs, provided they weren't constantly capsizing.

I'm also happy to be able to report that a number of members have already volunteered their boats (and their time) to enable performance measurement to take place. They currently represent roughly 1% of the membership so far! I have approached some others with "interesting" rigs but I'm still waiting for replies, and that is just in the UK.

The noble folk who have already committed are:

David Tyler, offering 2 rigs on his Hunter Duette "Weaverbird" if we can test her in September this year when he will be in Falmouth with his current rig

Edward Hooper, with the split junk on his Splinter "Amiina" based in Poole, and possibly some sister ships there with Bermudan rigs.

Lynda & Dave Chidell, in Falmouth with their Newbridge Pioneer "KRKA" with hinged battens.

Iain Fraser Grigor with a cambered panel sail on his "Solitaire", based in Scotland

Rodney Whitworth with his flat sail Sunbird 32 junk schooner "Gung Ho", based near me in Ipswich, so a convenient boat for me for setting up and testing the gear initially.

Robin Blain with his Swallow Bay 20 "Gigi", with hinged battens, based in Dorset, but mobile so may be able to combine testing with "Amiina", or even possibly in Falmouth

Chris Gallienne is also independently seeking to measure and record performance on his boat, perhaps with two different rigs, so might also participate, which would also be an interesting opportunity to compare two measurement systems.

That is without any attempt to recruit volunteers in NZ, where we would expect to see at least some. Our thought is the kit can be couriered to NZ for their summer season. We would welcome approaches from anyone else (in either hemisphere) interested in joining the performance measurement programme.

There are things we can do to adjust for the fact we are measuring different boats, for example we could correct the boat speeds to a "standard" waterline length as a simple first order correction. If we chose a standard waterline length of 25ft, convenient because the square root equals 5 and it is a mid range size, then a 16ft waterline boat would have its speed multiplied up by 5/4, and a 36ft waterline boat would have its speed multiplied down by 5/6.

We can of course get even more complicated and consider sail area/displacement ratios, and even produce vpp (computer generated) polars and compare the measured performance with those, but that would be complicated, and it would be very time consuming and challenging to get the right (accurate) data to put in to produce the performance prediction. However it can be done at a later date, provided we get some performance data to start with. With no data, we have nothing objective to work on.

Honsec JRA wrote:

Since Alan posted his ideas on the Forum he has received requests from members who would like their boat performance to be measured. This is an interesting development and maybe we could all learn from the findings. The gear can be couriered around the world to help members measure and possibly improve their individual sailing performance. The measuring equipment could be employed at a junket where 10 boats might try out the instruments. This concept will not appeal to every junk rigged sailor but some will relish the opportunity to find out how to get the best performance out of their rig and at the same time add their results to a database. Personally, I would like to see how my boat goes to windward – am I constantly pinching her, is the mainsheet in too tight?

In response to the wide range of opinions recently expressed I would like to briefly try and explain how we got here. I think the following Maori proverb is very appropriate:

Ka mua, ka muri is a Māori proverb that expresses a great truth around a simple image. The image is of a person walking backwards into the future. It suggests that the past is clearly visible but the future is not, that we have imperfect information for the road ahead, but also that this is a natural state of affairs. Let us look back for clues to the way forward, but also understand that the future is unwritten. The future comes out of the past but will not be identical to it. The only unchanging thing is change.

At the AGM there were 8 items brought up from the floor for general discussion. The committee has discussed every item and attempted to make progress on some and defer others. Some ideas require the spending of JRA funds, whilst others can be achieved for free. The idea from Jim Creighton, for example, about an animation of how a junk rig works could well be an expensive exercise. On behalf of the committee, I wrote to Jim and he has recently responded with a detailed proposal for the committee to consider. He will post his thoughts on the Forum so that everybody will have an opportunity to comment and we will take it from there.

The idea brought up by Pete Hill has also been keenly discussed by the committee and before Pete left for French Polynesia we had 2 meetings to discuss the way forward. The second meeting was attended by the Chairman, the Membership Secretary, myself, Pete Hill and 2 other knowledgeable members. The idea that we came up with was for the JRA to promote a one design dinghy. It would primarily be a tender, light weight, easy to build, easy to row, economical to build and could be rigged with any junk rig you wanted. Members could take them to junkets and have fun sailing them against other members. Crew and rigs could be swapped. We realised that a small dinghy was far from ideal for measuring performance but felt that something could be learnt and it would be good fun. We were mindful of the story of when member, Roger Scott, rigged a split junk rig to his Laser – all fine until he capsized and the tangle was epic! Members wanting to try out new ideas for junk sail plans could experiment at low cost with the one design dinghy. These thoughts were then taken to the committee.

At this time, and before we had posted anything on the Forum, Alan Boswell came in with his proposal. This sort of shunted our small time dinghy idea sideways. As everyone agrees, however we are talking about 2 different concepts. One about comparing different rigs and one about measuring a boat’s performance. The only time these could be combined is if David Tyler measures Weaverbird’s performance now and after he makes and sails with a wingsail. It will be the same boat and same helmsman. As we know David might have another rig in 2019?!

Since Alan posted his ideas on the Forum he has received requests from members who would like their boat performance to be measured. This is an interesting development and maybe we could all learn from the findings. The gear can be couriered around the world to help members measure and possibly improve their individual sailing performance. The measuring equipment could be employed at a junket where 10 boats might try out the instruments. This concept will not appeal to every junk rigged sailor but some will relish the opportunity to find out how to get the best performance out of their rig and at the same time add their results to a database. Personally, I would like to see how my boat goes to windward – am I constantly pinching her, is the mainsheet in too tight?

The committee is considering a capital budget of ₤3,000 for purchasing the equipment and an operating budget of ₤600 in year 1, ₤400 in year 2 and ₤200 in year 3. The project would be subject to an annual review. If the committee decides in principle to accept this proposal with the above budget a technical sub-committee will be set up to consider the equipment purchases and the operation of the performance measuring programme. At all times the committee will act in accordance with the Constitution and comply with the financial transparency requirements. The committee will reach a decision looking to further the aims of the JRA and its members.