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Old 09-08-2018, 06:18 PM   #1
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Fish tail rudder idea!!!

My idea is to make 2 TEAK wedges of 1 X 6 inch size the full height of the aft rudder edge and epoxy glue and bolt it thru ss plate rudder to each side. This goes on my 1982 MT34 . Sand and paint to suit. This will avoid high welding costs and be complete DIY except for wood shop costs.
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Old 09-08-2018, 06:57 PM   #2
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If its a S'S rudder its a 10 minute job to weld angle on trailing edge with 308l rods and $150 arc welder.
Added bonus, you now have an arc welder
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Old 09-08-2018, 07:16 PM   #3
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No way would it be strong enough.
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Old 09-08-2018, 07:21 PM   #4
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No way would it be strong enough.
What the teak wedges?

I am guessing done well they would be fine.

My concern would be erosion (unless that is what you meant)....but nothing some epoxy every couple years couldn't handle unless putting a thousand or more hours on it every year.

If something happens to them, no big deal...easy and inexpensive to replace or remove temporarily.
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Old 09-08-2018, 08:02 PM   #5
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Well, if teak would work, why not starboard?
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Old 09-08-2018, 08:02 PM   #6
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What the teak wedges?

I am guessing done well they would be fine.

My concern would be erosion (unless that is what you meant)....but nothing some epoxy every couple years couldn't handle unless putting a thousand or more hours on it every year.

If something happens to them, no big deal...easy and inexpensive to replace or remove temporarily.
Yeah maybe. It’s a lot of force and I can just see them snapping off with one hard turn or two. And by the way, I’m basing my opinion on absolutely no experience what so ever, so there’s that.
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Old 09-08-2018, 10:23 PM   #7
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DIRT FREE was extremely difficult to turn at low speed ..... Stainless steel plate bent at 15 degrees and through bolted to the rudder made a huge difference in low speed manouverability. I installed them perpendicular to the thrust.
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Old 09-08-2018, 11:01 PM   #8
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Anything could be through-bolted to the trailing edge of a rudder...it doesn't have to be teak. I'm not sure that the epoxy would be necessary and, in that application, that it would contribute much for very long.

If a variety of zincs stick on to a rudder, why not the trailing edge fish tail? The tension force on such bolts would be negligible, the shear forces minimal.

If a solid wedge of teak, why not try it? But honestly, a couple of bent metal plates as shown in boatpoker's picture would cost less to fabricate.
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Old 09-09-2018, 06:27 AM   #9
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Well, if teak would work, why not starboard?
Good idea except might not hold the anti foul paint!
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Old 09-09-2018, 06:30 AM   #10
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DIRT FREE was extremely difficult to turn at low speed ..... Stainless steel plate bent at 15 degrees and through bolted to the rudder made a huge difference in low speed manouverability. I installed them perpendicular to the thrust.
"NICE!!! Did it improve straight tracking any ???
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Old 09-09-2018, 06:33 AM   #11
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If its a S'S rudder its a 10 minute job to weld angle on trailing edge with 308l rods and $150 arc welder.
Added bonus, you now have an arc welder
Thanks! Then I would have a welder to move -store and sell----
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Old 09-09-2018, 06:40 AM   #12
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Wouldn’t the flare created by all these approaches create a bunch of drag under normal operation? I suspect that’s why it’s more common to see articulated rudders?
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Old 09-09-2018, 09:14 AM   #13
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Twist,
I agree.
The propwash is way above boat speed. I moved one of my zincs up to the top of the rudder to get them out of the propwash.
As we used to say in aviation the propwash is trying to blow the tail backwards. So it pulls back on the fuselage. Rudders pulling back on boats dosn’t help efficiency.
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Old 09-09-2018, 09:46 AM   #14
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I have a single engine no bow thruster and struggled with controlling the bow in a crosswind. I had a 3 1/2” angle welded to the trailing edge of my rudder and there is no loss of cruise speed, less vibration at cruise and superior low-speed control. I use a welder to attach my anodes so it only cost me another $100 to have this attached and that included the cost of the aluminum. The only part that slowed the process was figuring out how to hold the angle in place symmetrically for the welding. Make it a serious connection or you risk losing the doodad you use. Otherwise think of the consequences if it detaches while backing down. All those other ideas are too flimsy.
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Old 09-09-2018, 09:47 AM   #15
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The million dollar question...

How big of a fishtail to improve turning but small enough to be insignificant drag at cruise?
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Old 09-09-2018, 11:53 AM   #16
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The million dollar question...

How big of a fishtail to improve turning but small enough to be insignificant drag at cruise?
Good article below, with enough hints to track down Dave Gerr's article on Thistle, MacLear, Fishtail, and/or Schilling rudders;

https://www.sailangle.com/group-forum/topic/id/1871
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Old 09-09-2018, 01:31 PM   #17
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DIRT FREE was extremely difficult to turn at low speed ..... Stainless steel plate bent at 15 degrees and through bolted to the rudder made a huge difference in low speed manouverability. I installed them perpendicular to the thrust.
Did a rudder mod VERY similar to your, fabricated two pieces of stainless, 6 in wide, bent the aft 3 in at 30d. Bolted it to the rudder tail and did improve steering, however, not quite as much as I wanted. But, when I get aggressive to modify it again, it will be dirt simple and just unbolt the mod, make a new one with the same hole pattern and bolt back on.

Might use aluminum if I try it again... softer, yes, but significantly easier to work with.
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Old 09-09-2018, 02:03 PM   #18
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Thanks! Then I would have a welder to move -store and sell----
Mine takes up less space than 1/2 carton of beer.
Stays onboard and is rarely used but invaluable when needed and saves a fortune in paying someone not to mention finding someone to do a relatively simple task.
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Old 09-09-2018, 05:32 PM   #19
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I’m not sure where you are getting this high cost for a weldor, they are quite reasonable. However, if you are looking for a fabricator to build something, now it can get spendy.

How much drag do you think is produced by a small piece of aluminum behind a 36” wheel travelling at a max, balls-to-the-wall 10 knots? None of us are driving Americas Cup yachts on here. I’ll bet it’s way less drag than towing your dinghy.
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Old 09-09-2018, 05:44 PM   #20
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"NICE!!! Did it improve straight tracking any ???
Zero effect on tracking which was not an issue to begin with. It did help a bit when backing up.

2 pcs stainless bent at 15 degree. 2 ss bolts & nuts, one drill bit. 1hr. installation and about $100 Cndn dollarettes, I believe that's about ten bucks US
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