Subject: Re: [harryproa] Re: Leeway Prevention
From: Rick Willoughby
Date: 8/3/2010, 9:10 PM
To: harryproa@yahoogroups.com.au
Reply-to:
harryproa@yahoogroups.com.au

 

Todd

Given that the rudders serve as your leeway preventers as well as steering they are necessarily  powerful rudders.  So their working angle is less than conventional rudders.  The large radius nose gives wider working angle but is unnecessary for the control you require.  You can go down to a very small radius on the nose and still have control.  Compare what you have with the leading edge of a marine prop.  These are very small radius because they are designed to work at low angles of attack.  Reducing the edge radius will improve the flow off the edge when it is trailing.

Also having the rudders solidly linked means that you will often have more drag from them than needed.  If they are set up to prevent leeway on the wind then they will be trying to lift the hulls sideways upwind when sailing freer.

If you can set up some form of adjustment on the linkage to move the relative angle of the rudders you should find you can trim the rudders out to improve speed under various sailing conditions. 

Rick
On 04/08/2010, at 10:49 AM, tsstproa wrote:

 

I do have some entry angle on the flat side but I wanted to keep the leading edges a fuller shape knowing there both used as such. It does have a small tucked liked surf board rail on flat side of board I could probably get a little more out of it. My board thickness is only 3/4 inch thick at center chord. I could probably draw back a little more.

I have always associated the humming with slop or play some where along where the board its self is touching or where its connected. Like dagger board case, rudder cheek pieces, etc... Everthing has to be tight no gaps, slop, or play what so ever.

Todd

--- In harryproa@yahoogroups.com.au, Rob Denney <harryproa@...> wrote:
>
> It is almost certainly the trailing edge of your rudder/daggerboard shedding
> vortices and it slows you down. Make the trailing edge a 45 degree angle
> instead of a flat and it will disappear.
>
> rob
>
> On Wed, Aug 4, 2010 at 9:22 AM, bjarthur123 <bjarthur123@...> wrote:
>
> >
> >
> >
> >
> > >I seen speed recorded on my gps unit of 12mph sailing on the outside open
> > ocean with no problems just some vibration and humming.
> >
> > i've heard such humming on my Weta and a Farrier that i crew on when going
> > at similar speeds. everyone gets excited when this happens because they
> > think it means we're planing. perhaps it's correlated, but i'm thinking that
> > it's really due to the foils cavitating. true? if so, that's bad, right?
> > more drag less lift?? short of replacing the foils and/or slowing down, is
> > there anything i can do to stop it?
> >
> > ben arthur
> > weta #358, "gray matter"
> > ithaca, new york
> >
> >
> >
>


Rick Willoughby
03 9796 2415
0419 104 821

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