Rudder repositioning and Tankard info?

Just bought a Tankard 24' (Brian Tankard 1970's sailing cruiser in dreadful condition) and cannot find information on the design- any pointers would be appreciated. Also I intend to remove the through hull rudder stock and replace with a transom hung rudder. This will place the rudder much further aft. Is there any disadvantage in doing this from a hydrodynamic viewpoint? The boat is a glassfibre hulled bilge keeler with ply upper and deck and a moulded 'blister' type main cabin raised roof- slightly odd but not unattractive! Thanks for any assistance.

 

Without knowing anything, I am willing to bet that someone knowledgeable (spl?) naval architect will come and tell you something about lateral resistance being moved aft (not sure if the term lateral resistance is the right one, though), and that this will significantly alter the behaviour of the boat. Further, he will tell you that changing the rudder placement is not a small thing to do.

No, just kidding. I'm bored, tired and should've gone to bed hours ago. I'd like to have a transom-hung rudder on a spækhugger (a danish double-ender) – that would be neat, not to mention look neat.

I found a reprint from a used boat-test of the Tankard 24 here:

http://www.ybw.com/ym/secondhand_a-z.html

I don't know how much information is there, but it's not that expensive.

Oh, and a picture here (more if you sign up):

http://www.boatshed.com/tankard_24-boat-5747.html

 

It's possible you may develop some lee helm, as a result of your moving the rudder aft so much. This may be correctable with rig adjustments.

The under belly rudder is a much more efficient arrangement, particularly if the rudder top is very close to the underside of the yacht. Why would you desire to move it, especially in light of your inexperience in the configurational differences?

 

Thank you

Thanks for your input. I did find the YBW review but I know these are pretty scant writeups and I'm after some slightly more detailed info if I can find it. Have printed out the pics from the advertised Tankard which may be useful.
Had lots of boats including a Wharram 40' Narai and like the 'belt and braces' design of transom hung rudder. The Tankard unit is very corroded and siezed in the trunk so will need major surgery anyway. Thought while I was having to work on it I'd prefer to change to something I can see and sort if the need arises. I'm also going to use an outboard in preference to installing a replacement inboard in the limited space available. Not too keen on the steel plate splayed bilge keels with heavy iron bulbs bolted to the bottoms either but will just strengthen the hull in this area and live with them.
The boat itself reminds me of a plywood 20 footer I owned some years ago called a Mystic. Wonder if there is any common ancestry?
Thanks again
John