I finally got to the boat last week for my last sail of the season.

First I calibrated the log. I marked a 1/2 mile track on the chartplotter down the middle of the river and went backwards and forwards with the throttle fixed at 5 kts following Ueli’s instructions.
I then did the sums. 

It will come as no surprise to anyone that Arne was right!
(and apologies Arne for my taking issue in my ignorance, with your doubting of my initial figures).

According to my calculations the actual speed through water with 5kts showing on my log, was 4.45 kts, ie the paddle wheel is over reading by 11%.
IF this margin of error remains the same at higher speeds, it would suggest that my actual speed through water at the 6.1 kts I previously reported corrects to a little over 5.4 kts.

This at least puts my claims into the realms of the possible, as opposed to the absurd as per my previous post! 

hi paul

Paul Gardham wrote:

…(am I right in thinking that if I run a measured distance in both directions then take the mean time that will account for any current?)

no, you don't need the mean time. you need the mean speed.
you have to calculate the speed in both directions first. then you take the mean value. (this will give a faster speed than you average time calculation, as in a counter current you will loose more time than you win in the opposite direction…)

ueli

Paul,
I don’t doubt that your report is correct in the sense that you read and report the numbers correctly.

However, three factors still make me sceptical:

• ·         I have never been on board a sailboat with any rig which sailed faster than the theoretical hull speed when fully closehauled  -  in the Sadler 25’s case 5.87kts. A speed of 6.1kts is no less than 4% above hull speed.
  I know my last two boats can go 8% above the hull speed, but that is on a beam reach. Fully closehauled, my Ingeborg only makes 80-87% of the hull speed.
• ·         Thirty years+ as a maintenance engineer (electronics) have taught me to be sceptical to any measured numbers, whether being presented on analogue or digital gauges. I suggest you motor at a fixed speed over a measured distance and use the stopwatch to calibrate the log.
• ·         That video shows that your boat sails well, but at that short waterline (5.84m) and at a suggested speed of 6.1kts, I would have expected more serious stern waves. To me the speed looks like ‘good, normal’ speed on that leg.

I would say that an upwind speed of 5.5kts, or even 5.0kts would be very good. I, for sure, would have been very happy with those numbers.

Arne

Hi Folks,

Next on my list of winter projects is building a windvane.

I bought a Hebridean kit from John Flemming three years ago and haven’t got round to building it until now.

I know a few of you have experience of this design, so wanted to ask if there were any modifications you might recommend.

Cheers

I have the same kind of chainplates, and have left them in place against the remote possbility that they may be useful for tying something to. They don't seem to get in the way.

As regards the forehatch, is it really necessary? Perhaps as emergency egress on a large boat in case of engine or galley fire, but otherwise it's a hole in the boat that might leak. If it's over the heads, wouldn't a ventilator be enough?