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Capt. Sam's picture
Capt. Sam
Last seen: 3 months 1 week ago
Joined: 2/22/10
Posts: 319
reducing rudder depth on shoal draft boats

I know there has been some discussion about the fact that the rudder on shoal draft boats is as deep or almost as deep as the wing keel.
My 1994 MK I.75 was heavily damaged in hurricane Michael back in October and the rudder was bent and had to be replaced with new.
I just measured the depth today with the boat on the hard and found the depth to be 4ft 5inches, the exact stated draft of the keel.
Since this is the second rudder I've had this happen to, I'm seriously thinking I'll have the bottom 6" sawed off horizontally, and epoxied over. Hoping to make it less vulnerable to such damage. Question is has any brave soul preceded me in this experiment and with what results. I'm worried of course that I my will have a significant loss of steering controll by this reduction in rudder surface area.  All comments appreciated.
Capt. Sam

Capt. Sam Murphy
1994 Catalina 36, Hull 1327
Shoal draft, two cabin model.
Panama City, Florida

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Capt. Sam Murphy
1994 Catalina 36, Hull 1327
Shoal draft, two cabin model.
Panama City, Florida

No Rush
Last seen: 4 days 1 hour ago
Joined: 3/15/17
Posts: 14

We have the identical boat, Hull No. 1363 shoal draft wing keel.  I find the steering iffy as it is, I wouldn't cut anything off the rudder.

McFly
Last seen: 4 days 21 hours ago
Joined: 10/22/18
Posts: 146

It's a bit more of a project, but what if you added the lost surface area to the trailing edge of the rudder?  I'm no nautical engineer, but I would assume the surface area, cord, camber, length and all that other engineering stuff is fairly important.  If you shorten the rudder, I would try to make up for the loss of surface area by fairing on some surface to the trailing edge.  I have seen other C36s on the hard with NON-factory rudders, different shapes, so I know its possible.  See if you can find a salvaged, stock rudder and work on that one before you cut in to the one that is currently hanging on your boat.

Mike

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Jackfish Girl, 1999, C36 MKII, Tall Rig, Wing Keel, In-mast furling, Phinneys Harbor, Bourne, MA
Haro's picture
Haro
Last seen: 2 days 11 hours ago
Joined: 11/7/14
Posts: 256

Adding to trailing edge may place additional torque on the steering mechanism.
I suppose you would need to add no more than 1".

McFly
Last seen: 4 days 21 hours ago
Joined: 10/22/18
Posts: 146

The more I think about it, changing the geometry of the rudder is kind of a big deal.  Tread carefully.

Mike

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Jackfish Girl, 1999, C36 MKII, Tall Rig, Wing Keel, In-mast furling, Phinneys Harbor, Bourne, MA
Capt. Sam's picture
Capt. Sam
Last seen: 3 months 1 week ago
Joined: 2/22/10
Posts: 319

Yes I aqree that rudder modification is a risky venture. I'm holding off until I can maybe get a word in the one of the Catalina design team..

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Capt. Sam Murphy
1994 Catalina 36, Hull 1327
Shoal draft, two cabin model.
Panama City, Florida

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