Lifting keel rudder – nightmare

James Dargie

6th March 2009 at 11:23 PM

Hi,

I bought a lifting keel Sonata last year (it has auxilliary bilge keels added – so it can dry out and stay upright), the rudder was cracked and clearly needed replacement, so I have had one made; it arrived this week and has been in the kitchen since. I brought the old rudder in from the garage this evening to start strippng the fittings off and became concerned that the old and new are a different size – panic set in.

I’ve had a look around on this forum – and I’m slightly confused. Way back in 2005 Tim Owen wrote: “I had believed that L/K rudders were shorter than the fin rudder, and I and the other owner were contempolating making a lifting rudder arrangement to accomodate a longer rudder – I got as far as a designing one, but when I checked the class rules on this site I found that my rudder was exactly as drawn for fin keel boats.” Tim’s note makes sense as I have an original profile diagram of the lifing keel sonata and there is text on it which states: “Rudder: Same depth as on fin keel boat but on sliding pintles so can lift for mooring or shallows.”

My new rudder is larger than the old rudder and I really don’t fancy a rudder longer than the depth of the keel stub/ bilge keels as clearly this is going to be a problem on a drying mooring.

Confusion reigns because:

a) The depth of both rudder designs on pages 28 & 29 of the class rules [ http://www.rya.org.uk/assets/technical/Web…nata%202008.pdf ] is given as 1013mm +/- 15mm from base to rudder datum mark.

My new rudder (for which I’ve paid good money) has an equivalent depth of about 870mm

c) My old rudder has an equivalent depth of about 790mm

So I appear to have a rudder shorter than that in the class rules, but longer than my old one, I seem to rememenr that before I had the boat back on the cradle that the old rudder only just cleared level ground, yet my new rudder is 8 cm longer. I’m hoping it will lift along the sliding pintle – but I’m worried!

My question is simple does anybody know what the dimensions of the rudder for the lifting keel version are supposed to be. In terms of class compliance or Portsmouth Yardstick this does not matter as the bilge runners make it. But sailing performance and issues of drying out have me thinking.

Any ideas?

Thanks

James