Minimum/Optimal Rudder sizing

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barts
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Re: Minimum/Optimal Rudder sizing

Post by barts » Sun Sep 11, 2016 5:13 pm

David Gerr's book: Boat Mechanical Systems Handbook is excellent, and contains a lot of discussion about designing rudders of various types. Highly recommended.

- Bart
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Bart Smaalders http://smaalders.net/barts Lopez Island, WA
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cyberbadger
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Re: Minimum/Optimal Rudder sizing

Post by cyberbadger » Mon Sep 12, 2016 6:07 am

Well Locktite Tite Foam maybe an ok product, but I cannot recommend it for a rudder like this and am disappointed in it. Great stuff would work, those familiar with bondo should go with that.

Left 24 hours the enclosed end was still a mess of unset chemical stickiness:
Image

I made due. I just capped the ends with QuikSteel. - Sort of like JB weld, can set underwater and can be put to good use in a marine environment.
Image

Here you can clearly see the warp or twist I introduced. At this stage there is white primer on the rudder. The picture is looking at what would be the stern of Nyitra with the rudder at "center".

i don't think it will be very noticeable unless you look at it right at this angle. I wouldn't be surprised if it generates a small artifact into the wake or slipstream behind the boat.
Image

-CB
Last edited by cyberbadger on Mon Sep 12, 2016 6:12 am, edited 1 time in total.
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cyberbadger
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Re: Minimum/Optimal Rudder sizing

Post by cyberbadger » Mon Sep 12, 2016 6:11 am

Oh - and how close can it be to the stern of the prop?

Is 2" ok? 4"?

-CB
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barts
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Re: Minimum/Optimal Rudder sizing

Post by barts » Tue Sep 13, 2016 4:11 am

So long as it doesn't contact the prop you're ok; an inch or two should work fine. Sailboat rudders often surround the prop. Remember to make it possible to remove the rudder w/o too many difficulties. On our small boats, you can often drop the front of the trailer enough to get clearance to pull the rudder + shaft.

- Bart
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Bart Smaalders http://smaalders.net/barts Lopez Island, WA
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