Measuring junk sailing performance

  • 03 Jul 2017 16:05
    Reply # 4929926 on 4913961

    Well done Edward!

  • 03 Jul 2017 11:33
    Reply # 4929608 on 4913961
    Anonymous member (Administrator)

    Well done, Edward! You must be pleased to have matched Sparkle, at least on handicap which means you must have sailed as well as them over the whole course.

    I see the handicappers gave you a benefit compared to her, (TCF of .776 against .821) of about 5%, which I guess reflects their assessment of the rig, but the results suggest it is about right. Does she have a spinnaker, and did she use it?

    There ought to be a prize for the first person to finish (on handicap) in carpet slippers (as per Jock McLeod in Ron Glas)!

    Are you up for some data collection on Amiina?

  • 02 Jul 2017 20:09
    Reply # 4928837 on 4913961

    Ref sailing performance, herewith an email just received from Anthony Cook that details

    Amiina's performance in yesterday's Round the Island race. 

    ""Morning All


    Don't know whether you have access to Excel, but the attached is an analysis of the results.  The first tab, 'All' shows everyone in the race.  The second tab, 'ISC' shows just those boats in the ISC divisions, from which  I have excluded any that didn't finish, or were disqualified.


    Assuming I have interpreted the figures correctly, Amiina was 21st out of 46 in Div 8D, 41st out of 136 in Div 8, and 106th out of 609 in the ISC group.


    I call that a pretty good result!


    Anthony"


    Anthony has also downloaded the Results pages from the Island Sailing Club

    from which all the technically competant can see the details 

    of each boat and their relative performances over a 56 mile  round course

    full of differing conditions and complex waves and tides. The link will be posted as soon as i learn how to do it. 

    Cheers

    Edward

    Last modified: 02 Jul 2017 21:08 | Anonymous
  • 02 Jul 2017 15:56
    Reply # 4928653 on 4913961
    Anonymous member (Administrator)

    Thanks for the latest positive suggestions from David and Rob.

    I have just emailed a proposal to the Chairman & Hon Sec for them to deal with as they see fit. There are some interesting alternatives available ranging from around £1200 to a maximum of £2600 and these figures include wind and boat speed instruments, a recording device, and some analysis software.

    We could spend less by using members computers, tablets, or phones as recording devices, and cheap(er) software, but the instruments and mounting pole(s) will cost at least £600 for off the shelf units and metalwork.

    No doubt the proposal will end up being posted somewhere, and at that point you will be able to see the details, and pick it to pieces. It is by no means absolutely comprehensive, but I reached the point where I was spending more and more time researching ever finer details, and I felt diminishing returns had set in.

    I hope you will be able to see it soon.

  • 01 Jul 2017 02:03
    Reply # 4927231 on 4913961

    David,

    I think it would be very worthwhile and it is fantastic that you have volunteered to use Weaverbird to get the testing underway. On talking to Pete before he left he rattled off no fewer than 14 possible rigs that we could test!!

    To move this along, maybe we need Alan to specify the testing process, the test equipment and a cost so we could discuss it as a committee and on the fora to see whether we want to proceed or not.

    Rob



  • 30 Jun 2017 08:16
    Reply # 4925722 on 4913961

    Rob, 

    I was assuming that Alan would be specifying a set of instrumentation in a form that could be fitted to any boat, and that the JRA would fund it and make  it available to me and to others.

    My plan would be to make a comparison between my current rig and a wingsail. The mast position could accommodate a Sunbird sail, designed by Alan and made by Exe Sails, or a sail designed and made by Arne, thus making it possible to run comparative tests on four different types of sail, if that were thought to be a worthwhile thing to do? 

  • 30 Jun 2017 06:25
    Reply # 4925694 on 4913961

    David, 

    I cannot believe that you are going to build another rig for Weaverbird! You are just amazing. Will it be possible to measure Weaverbird's current performance before you change? Do you need some special instruments that maybe the JRA could contribute to? Could Alan or others use the same instruments?

    Alan, 

    On behalf of Pete Hill, who is currently on route to French Polynesia, we would welcome you onto the technical sub committee and look forward to your expertise. Pete will be back in New Zealand in 6 months time but I'm sure we can move things along in the meantime.   

    Rob

  • 29 Jun 2017 10:29
    Reply # 4923498 on 4923407
    Anonymous member (Administrator)
    David Tyler wrote:

    Now I have a boat for which a wingsail would be a more achievable proposition, at a smaller size than was the case with Tystie. I could make a wingsail this coming winter, to the same planform as my current sail. I have enough cloth for the sail, and could reuse most of the hinged battens that are in the current sail. I think this would be a worthwhile comparison - same area, same planform, same camber, but one sail with a sharp leading edge and exposed, draggy mast, the other with a better foil section, a rounded leading edge and a concealed mast.

    But I would need a self-contained wind and water sensor setup, at either end of a long tube that I could lash to the bow. Anyway, I've always felt that masthead anemometers are not much use in a seaway, when the masthead is describing wild circles.

    David,

    I bet your Duette is just the right boat to be used as a rig testbed. Still, before you change your rig, I hope you get in some sailing in company with original Duettes or Sonatas.
    The proof of the pudding is  -  the match-racing.

    I agree with you that masthead anemometers are not the best. Apart from flying around up there, they tend to see much stronger winds than I sense in the cockpit. Quite a few times, when I have been out sailing in a breeze, other sailors around me report about gale-force winds...

    Arne



    Last modified: 29 Jun 2017 16:41 | Anonymous member (Administrator)
  • 29 Jun 2017 08:17
    Reply # 4923407 on 4922225
    Alan Boswell wrote:

    Annie suggested I should email the people who have developed different versions of the rig, which I will do if I can track them down, but I don't necessarily know about all that is happening, so it would be very helpful if anyone developing rigs would put a post on this forum to let us know what they are doing, or have done, and if they would be interested in doing some testing to get performance data for their rig and boat combination.

    OK, I'll volunteer.

    I now have a rig that is very easy to work with, it reefs and furls well, tacks and gybes well and goes to windward quite well enough for cruising purposes. How well? I don't know.

    Yet I still hanker after the wingsails that I was trying to develop on Tystie. Were they faster to windward? I felt they were, but had no proof. The character of the airflow, as revealed by a wind-wand, was very good. I failed to get the engineering good enough, but they were very easy to sail with, once rigged, and I was convinced that the future of sailing lay somewhere in this direction (the people at Beneteau thought so, too, but I've heard nothing recently about their wingsail trials).

    Now I have a boat for which a wingsail would be a more achievable proposition, at a smaller size than was the case with Tystie. I could make a wingsail this coming winter, to the same planform as my current sail. I have enough cloth for the sail, and could reuse most of the hinged battens that are in the current sail. I think this would be a worthwhile comparison - same area, same planform, same camber, but one sail with a sharp leading edge and exposed, draggy mast, the other with a better foil section, a rounded leading edge and a concealed mast.

    But I would need a self-contained wind and water sensor setup, at either end of a long tube that I could lash to the bow. Anyway, I've always felt that masthead anemometers are not much use in a seaway, when the masthead is describing wild circles.

  • 29 Jun 2017 01:18
    Reply # 4923122 on 4923065
    Deleted user
    Annie Hill wrote:
    Bryan Tuffnell wrote:An alternative may be to produce scaled models of the rigs, and trot them along to the nearest university that has a wind tunnel. It's easy to derive the relative magnitudes and directions of lift and drag at different angles to the wind, and that may be as far as anyone needed to go.
    Been there, done it.  Read all about it here.  Well, not exactly - there weren't as many experimental rigs to play with, then and rather than making comparisons, we were trying to understand how junk sails to their stuff. 

    Interesting, but the comparisons are what's needed in this case.

    I belong in the camp that wouldn't use windward speed potential as the criterion for selecting a rig, and personally wouldn't spend a lot of money on determining which rig was 'the greatest', simply because for me there are too many other factors in that choice. Like most of us though I have an idle curiosity in seeing which rig is fastest. 

    In a previous life, I've used instrumentation and software to try and determine aircraft performance, often in conjunction with side-by-side in-flight comparisons. I've done a fair bit of it, and always found it very hard to get results that are trustworthy unless there's a clear-cut winner, and that's using $big$, laboratory calibrated instruments. It's really hard to do. 

    I'm just suggesting tunnel testing of models is a way of getting qualitative results at low cost, with fewer variables, than instrumenting full-scale boats. It's just less fun than hooning around a bay in a sailboat.


       " ...there is nothing - absolutely nothing - half so much worth doing as simply messing about in junk-rigged boats" 
                                                               - the Chinese Water Rat

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