Subject: Re: [harryproa] Re: Dagger Board
From: Rick Willoughby
Date: 5/30/2011, 12:11 AM
To: harryproa@yahoogroups.com.au
Reply-to:
harryproa@yahoogroups.com.au

 

Gardner

In my mind I thought you were going to have a smaller pin and allow the board to actually work against the side of the hull.  What you have is like a ring bearing.

I cannot see any reason why you would not place the board on the ww side of the lw hull using this sort of bearing support.  That way there is less transition from shape at the side of the hull to under the hull.

For the revised VPP with schooner rig, the board was 1m deep and 0.3m long.  The section is a NACA-4512-15.  The section Cl is 0.6 at zero degrees.  The pressure face is not quite flat so you would still need a transition from the flat side against the bearing to the part under the hull.  The blade would only be 36mm thick.  This could be a bit small to handle the bending moment from a 1 tonne force at about 0.7m down the blade.   

 Rick
On 30/05/2011, at 1:07 PM, Gardner Pomper wrote:

 

Rick,

Hope you don't mind if I copy the group.

I finally got a chance to try to draw out what I have in mind for the
leeboard, just in case I didn't explain it right .Google Sketchup does
not deal with curves very well and I am no expert, so the drawing is
pretty crude, but hopefully demonstrates the idea. Is this what you
thought I meant?

Oh, the drawinigs are in the same "Gardner's layouts/ToyyoT" directory
as the rest.

I dont have any problem with it being on the ww side. With this big a
pivot pin, I am not sure it matters and I see your point about making
the shape simpler. It will have alot of force on it.

- Gardner

On Sun, May 29, 2011 at 8:10 PM, Rick Willoughby
<rickwill@bigpond.net.au> wrote:
> Gardner
> I have been thinking more about the dagger board.
> It would be a simpler shape if it was mounted on the ww side of the lw hull.
>  It could still work against the side of the hull but the wear pad would be
> well above the waterline.  The pivot would be close to the bottom of the
> hull. This puts the pivot closer to the force and the rubbing pad as far up
> the side of the hull you like.  It could be a slot that secures the board
> from moving out from the hull to prevent flogging.
> There are many ways to make a strong point for mounting the pivot below the
> waterline.  It is no different to fixing a fin keel.
>
> Rick Willoughby
> rickwill@bigpond.net.au
> 03 9796 2415
> 0419 104 821
>
>


Rick Willoughby
03 9796 2415
0419 104 821

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