Hi,
BD had the kick up dagger rudders. To be able to steer them you need balance.
The old BD rudders worked, but only when fully down (2 m draught)
The balance you need by canting the blade forward is gone when it's partially retracted.
That's why BD's new rudder is on a shaft in bearings hanging from the beam.
Bearings are on a tube through which the shaft can be pulled up. That way balance doesn't change.
Kick up function by having shear pins holding the bearings in place.
This seems to be a difficult problem in bigger boats. The rudder boxes on BD's beams are big and heavy.
I'll post some photo's soon.
Regards,
Rudolf
----- Original Message -----From: George KuckTo: harryproa@...Sent: Friday, July 10, 2009 4:30 AMSubject: Re: [harryproa] Re: MODERN NAMES of things/ Rudders
Hello Robert ,I think it should be possible to have a daggerboard rudder that can kick up. It would work on a ruder that can rotate 270 degrees but would be a problem on 360 degree rudders. All that is needed is a kick up dagger board case. This is what is used on the F32. Take a look at the F32 rudder upgrade plans.I think the original rudder on Blind Date is a dagger board type but I do not know if it can kick up. What ever happened with the new rudder for Blind date ? It should be possible to make a kick up case that the dagger board can go through. That would allow you to raise dagger rudder part way up for shallow water and it can still kick up.Rob, what type of rudder is on the current 12 M Harryproa plans, Is it a dagger board rudder ?Happy sailing,George KuckChestertown, Md.--- On Thu, 7/9/09, Robert <cateran1949@yahoo.co. wrote:uk>
From: Robert <cateran1949@yahoo.co. uk>
Subject: [harryproa] Re: MODERN NAMES of things
To: harryproa@yahoogroups.com.au
Date: Thursday, July 9, 2009, 7:33 AM
Sounds like you've got the winter blues. You certainly have got stuck into the rebuilding but can imagine it can seem interminable at times. I am pretty impressed at the rate of progress.
There is a plant biology paper on Hypolithic Cyanobacteria in the Tanami Desert ticking away (green slime that grows under rocks living on the light that manages to get through the quartz) but mainly I am organising some house plans for moving back down to Eden. It is to be a mud brick house in the town so it may cause a bit of a stir, but should be reasonably cheap and very energy efficient. I was hoping the admiral was going to retire next March so I could get back to being a beach bum again but she was give a promotion and decided to hang in for another year or so. She is in the same line of business as Rob's wife. We plan to visit Rob when he moves up to Qld and get some sailing in.
I have not changed what I want in a Harry for a while now, but am still not sure what what to go for in the rudders. It's is easy to have kick up or retracting but difficult to get both. I have played around with telescopic rudders and a shaft that moves up a little way. I have looked at rudders that kick up by pivoting on the shaft and by the shaft letting go at the bearings.I am tending to go for the shaft letting go at the bearings and allowing a small amount of retraction and maybe a sacrificial tip. - In harryproa@yahoogrou ps.com.au, Doug Haines <doha720@... > wrote:
>
> hi robert
>
>it's your choice.
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