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Fitting rudder blades into castings
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Author:  findbluesky [ Thu Apr 07, 2011 10:09 am ]
Post subject:  Fitting rudder blades into castings

Does anyone have any tips on fitting epo rudder blades into their castings when they are a very tight fit? I would like to add a shim to make them raise and lower smoother and to stop the scratching on the blades, but I can't fit them in. In fact I can hardly fit the blades themselves in.

Author:  MBounds [ Thu Apr 07, 2011 11:01 am ]
Post subject:  Re: Fitting rudder blades into castings

EPO blades are thicker (that's one of the reasons they're better), but as you found out, they can be a very tight fit, especially in old rudder castings.

File the insides of the rudder castings until they are very smooth, and round the edges just a bit. You should be able to get very thin sheets (0.01") of Delrin (acetal copolymer) to use as shims.

DO NOT try to "open up" the castings by bending them. Cast aluminum is brittle and will break before it bends.

Author:  newsreader [ Mon Apr 11, 2011 8:23 pm ]
Post subject:  Re: Fitting rudder blades into castings

Thanks for the advice. I was just about to do that.


MBounds wrote:

DO NOT try to "open up" the castings by bending them. Cast aluminum is brittle and will break before it bends.

Author:  findbluesky [ Tue Apr 12, 2011 12:45 pm ]
Post subject:  Re: Fitting rudder blades into castings

Thanks for advice, tough job but completed now. Forced blades in with shims, I'm sure that opened the castings up a mm or so but nothing broke. Absolutely no slop in the rudders at all now, perfect!

Author:  MBounds [ Tue Apr 12, 2011 1:50 pm ]
Post subject:  Re: Fitting rudder blades into castings

findbluesky wrote:
Thanks for advice, tough job but completed now. Forced blades in with shims, I'm sure that opened the castings up a mm or so but nothing broke. Absolutely no slop in the rudders at all now, perfect!
Non-plastic deformation (non-permanent bending) is OK, but there's a very fine line between that and plastic deformation / breakage. Finding that line can be very expensive.

They'll loosen up over time (rudders are probably hard to move up/down now).

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