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knobblyoldjimbo

Maricat Rudder Blade - rehole

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We generally talk about redrilling the pivot hole on the rudder blades to aid balance, particularly after raking the mast back as the modern boats do.

This is a pic of the one I redid this weeked.  You can see where the original hole was - I bunged it up with the epoxy stuff you squeeze together to mix.

The new hole is further forward (and a little higher) than the original.  This allows the leading edge of the blade to come forward of the pintle centreline.

Do this too far and you'll get very hard to manage lee helm where the rudders will suddenly and unexpectedly kick leaving you with an unplanned gybe or drive the bows into the wave.

I think this will still give me some weather helm.  It's not an exact art, my last Mari I drilled the holes to get the rudders forward about the same as Mick's super fast boat but it was too far and I got the effect described above.

 

DSC_0206 (Medium).JPG

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It is an exact art

when rudder is in sailing position draw a line on rudder with pencil thru centre of both pivot points continuing to bottom of rudder 

this will give centre of effort for rudder

now choose a measurement below lower pintle and use as a constant

mark this on previous line at right angle to it and measure distance to leading edge of rudder

this will give you a reference to make incremental adjustment to rudder rake as per your individual requirement

 

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This sounds like a very technical approach.  For my rudders I moved the rudder blade pivot about half a hole forward and then used shims under the top rudder gudgeon.  After some trial and error the shims are now12mm thick which gives me quite good balance.  My rudder blades are the 1979 Hydrofoils.

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Hmm - there's always a different way.  In my case the top gudgeons (and the bottom ones) had bonded into the aluminium backing plate so I had to drill them out with a hole saw!  I guess that now I can undo them I could shim them.

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Yep.  Plenty of old Maricats have hatches aft of the rear beam to allow access for transom repairs and to replace the old metal threads with bolts.

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Yes, there is a Maricat part that has curved bases that nearly fit the rear deck.  Alternatively a couple of BCF hatches at $10 apiece plus a load of Sikaflex will do the job.  Mine came with rear hatches and the bungs had been filled in - another common place for water to get in.  I also have a drill powered pump to remove any water that's got in - I think most of mine comes through the hatch covers!

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