The rudders are 0.5mx1.0m, located 2+ metres from the bows.
Regards,
Arttu
Rudolf vd Brug [rpvdb@freeler.nl] kirjoitti:
> Rob,
> With the old rudders there was noticeable bow down trim when sailing.
> Front rudder up or down didn't seem to make much difference.
> Upwind or downwind wasn't different either. We never experienced any lee helm no matter what combination
> of sail/rudder up or down. I think we covered most combinations.
> Steering was ok on all courses, but over 10 knots rudders couldn't handle the load.
>
> The new rudders downwind have about the same angle to fight the luffing as upwind.(10 deg at least)
> Going upwind they stall easily if you it point a bit too high.
> The front rudder needs to be in the water to help keeping the boat from luffing.
> I think it isn't as much lack of lat. area as rudder placement causing the problem. See old rudders above.
> Adding the extra (lee)board/keel made a huge difference when pulling the sheet lying beam to the wind.
> Without it getting going was a matter of going almost dead downwind before we were able to counteract the luffing.
> With the leeboard we just pulled the sheet and sailed of. It was actually easier then with the old rudders which also needed
> a course a bit downwind to get going.
>
> Ask as many questions as you like, I think rudders are the most important proa-issue at the moment.
>
> Rudolf
>
>
> ----- Original Message -----
> From: Rob Denney
> To: harryproa@yahoogroups.com.au
> Sent: Thursday, March 10, 2011 12:49 AM
> Subject: Re: [harryproa] Beam mounts and tillers
>
>
>
> Rudolph,
> Did it sail bow down with the old rudders? Was there any noticable
> change in trim with the front rudder raised? Did it make any
> difference upwind or down? Do the new rudders steer ok downwind?
> Sorry about all the questions, but the more I know, the more able I am
> to sort it out.
>
> Ben,
> There is no question it is sailing bow down and no doubt this affects
> the steering. The question is why is it bow down? I suspect it is
> because the rudders are turned at a big angle. The only other change
> is the keel. If it is the rudder angle, the next question is why are
> they at such an angle? Obviously a clr/coe balance problem. But if
> you lift the front one (or align it with the flow), the coe is ahead
> of the clr of the aft rudder which should provide lee helm. The keel
> will influence this, not sure how much. If you reduce the sail area
> aft of the coe (reef the main, the lee helm should be even more
> pronounced. Apparently (Rudolph?) it wasn't.
>
> I have found that once any of the boats are moving, the helm is pretty
> easy (see the various videos). BD is the exception to this. The
> time when it can be tricky to steer is coming out of a shunt. That is
> when big rudders and no fixed foils work best, in my experience.
>
> All very perplexing.
>
> rob
>
>
>