Subject: [harryproa] Shunting improved by moving CLR or CofE?
From: Luca Antara
Date: 10/16/2009, 12:48 PM
To: harryproa@yahoogroups.com.au
Reply-to:
harryproa@yahoogroups.com.au

 

The BD sailing discussion has been about a Harryproa already built and therefore has obviously emphasized the more feasible alterations that can be done to an existing proa by looking at moving the CLR rather than the CofE.

Rudolf has just pointed out that BD had a tendency to luff up anyway after a shunt unless she was already pointing downwind somewhat, which leads me to think that the Cof E is too far back and results in larger loads than necessary on the rudders. 
For a boat that is still at the design stage (at least for the masts, sails and rudders) I can see three possible CofE solutions that could change the dynamics of shunting. The first is the obvious one of having a larger jib and smaller main, but this would not work with a Ballestron rig if the Cof E became forward of the mast, and anyway, Rob has indicated that the jib is already quite difficult to raise.  The second is to have a wing mast which should bring the CofE of the main forward (same possible problem as solution 1 with the Ballestron rig). 
The 3rd is to have 2 masts. I have never shunted a proa but from my windsurfer experience moving the mast (and therefore CofE) fore and aft, it should go like this. 
  1. While heading upwind a little, let go the fore sail sheet  and there will be a tendency to luff up more as the CofE has temporarily moved way aft. 
  2. Let go the aft sail sheet and sheet it in immediately as the fore sheet in the new direction, which gives a temporary CofE way forward. 
  3. Sheet in the new aft sail once up and running.
Other benefits of 2 masts could be the ability to move the CofE at will by sheeting in or out the aft sail and thereby reducing the load on the rudders. In theory one might be able to take the steering load completely off the rudders and steer on a reach with just with the sails, as with my windsurfer which obviously has no rudder steering. 
Does anyone (Rob,Doug?) have a proa with 2 masts that can verify or disprove this?

Also from my windsurfer experience, I had theorized that the CLR could be moved aft by raising the fore rudder but this does not seem to work for BD.....

Cheers,
Robinho (mech.eng. windsurfer).

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