[C320-list] Speed Increase by Installing App on Smart Phone - How to calibrate knotmeter?

[Martin Rosenberg]

Please keep in mind that the knotmeter is telling you speed over water
while the app must be telling you speed over ground. I can't believe that
your lake currents are that strong but have you tried clocking it in
opposite directions to see if it's still the same? If current is affecting
your ground speed that will expose it.
Martin Rosenberg
"Avalon"  #823

On Mon, Aug 3, 2015 at 8:59 AM, Dean Vermeire <dean at vermeire.us> wrote:

> First of all, I should point out that after 40 years of sailing, our
> Catalina 320 (which we have had for 4 years) is our first boat with speed
> and wind instruments.  Electronics aren't all that necessary on a lake in
> Kansas.
>
> So, when I see that I am doing about 2.2 knots in 6-10 knots of breeze on
> a beam reach, or motoring at 2.5 knots with the yanmar humming along at
> 2500 RPM, I really don't have anything to compare to.  And then, some of
> you folks talk about motoring at 6-7 knots, so I just figure that I should
> switch out the 2-blade prop for a 3-blade.  But when you talk about sailing
> at 6-7 knots or more, and the most I have been able to get out of her is 5
> knots with the Asym flying in a good breeze, I start thinking one of two
> things - either the knotmeter is lying to me, or I suck.
>
> Yesterday, I downloaded a simple GPS app, "SailDroid", to my phone. My
> knotmeter says 2.2 knots.  The phone says 4.5!  This is not definitive
> proof, but I'm going to say that I do not suck!
>
> It is amazing how it feels like you are going faster, just because some
> widget thinks you are.  :)
>
> The paddlewheel sending unit is only 2 years old.  Is there a way to
> calibrate the knotmeter (ST-60)?
>
> Thanks,
> Dean Vermeire
> Moonstruck II (#847)
>
>