RSS Forum – latest posts

  • Instrumentation & Control • Re: Accuracy of GPS speed measurement
    I have come to the conclusion that, based on specifications from receiver manufacturers, GPS speed measurement is not sufficiently accurate for drag measurement by towing. I have considered a couple of alternatives:1) measurement of speed at a shore mounted winch that is doing the towing2) measurement of speed by timing between start and finish lines […]
  • Events & other announcements • Catalyst 55
    ... can be downloaded from the Members area of the AYRS Forum - viewtopic.php?f=37&p=3514#p3514.(If you have not done so already, you will need to be verified as a paid-up AYRS member before you can access this. Message the AYRSWebadmin).Statistics: Posted by AYRS Editor — Fri Oct 11, 2019 11:27 am
  • Instrumentation & Control • Re: Accuracy of GPS speed measurement
    Hi FredMy understanding is that GPS determines speed by a method that is fundamentally different to the method by which it determines position. Hence knowledge of the positional accuracy does not necessarily tell us much, if anything, about speed accuracy. The American government provides information about the accuracy of GPS here:https://www.gps.gov/systems/gps/performance/accuracy/Looking at the above web […]
  • Instrumentation & Control • Re: Accuracy of GPS speed measurement
    I believe that over a reasonable distance(?) it is accurate but the best GPS units are I think differential and accurate in position to cms where as older (and ? cheap chips ) accurate to 15 metres so the speed may be in error but it may be worthwhile as then on has automatic speed […]
  • Instrumentation & Control • Accuracy of GPS speed measurement
    Can anyone tell me about the accuracy of GPS speed measurement - I ask because I am wondering if it is worth including GPS speed measurement in the unit I built to measure the drag of towed hulls at the recent AYRS event at the Bassingstoke Canal Centre - see posts here under 'Events'.The American […]

Optimization of the length of a Surf-Ski Kayak

This project has been undertaken with the aim of finding a method by which the length of a surfski kayak can be optimised in terms or having least possible resistance. Surf ski kayaking is a highly competitive international discipline that takes place on open ocean, it differs from other forms of kayaking because of the lack of regulations regarding the length of the boats. An aim of this work was to determine if the boats on the market today are fully optimised in terms of having a length with least resistance. Through use of software that incorporates thin ship theory as well as skin friction data from ITTC ’57 it was possible to calculate the wave making and frictional resistances for a series of lengths of Wigley hull forms with constant displacement and beam. This allowed a total resistance to be calculated for each length which in turn leads to an apparent ‘optimum’ length. In terms of boats currently available, it appears from the results that they have indeed been optimised effectively however only for a small weight range of user. A conclusion of this work is that there may well be scope for manufacturers to produce boats better suited for other weight ranges of kayaker or paddler as they are more often known.

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Multihull Capsize Recovery

Multihulls can be light and fast but cruising ones must never capsize: They stay inverted.
Single hulled yachts can be self-righting and seaworthy, some large and small ones can survive storms and work to windward in gales but to be quick they need deep weighted keels and a wide hull. Built in buoyancy can avoid sinking but they are outperformed by multihulls.
Can a multihull be seaworthy? Could one work to windward in a gale or sail on when mid Atlantic breakers flatten her? What about an automatic system for capsize recovery? Could a multihull heave to in heavy weather and work slowly to windward like a Contessa? Probably not, but perhaps it could be as seaworthy as the offshore racing fleet.

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AYRS NWUK Local Group – Winter meeting – 10th December 2016

As is now the custom at our Winter Meeting, members arrived just after noon for a 12.30 pm start. There were seven members and four of their wives present. Three apologies from absence were received from Roy Anderson, Steve McKenna and Colin Weir. After a short introduction, a Buffet Lunch was served which was enjoyed by everyone (thanks Col). Amply fed and watered, the Ladies retired to the conservatory leaving the Gents in the lounge to have their ‘official’ meeting.

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