Rudder Spacing

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watersports7
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Rudder Spacing

Post by watersports7 » Wed Apr 06, 2011 8:41 pm

In the process of building a lighter pancake cage, my original cage had rudders spaced 30" apart, new setup will have 24 1/4" rudder spacing, will this 'tighten up the handling'
or make it more responsive? prop is 68"
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harley
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Re: Rudder Spacing

Post by harley » Wed Apr 06, 2011 8:47 pm

looks good man .. get~r~done son , time too ride... :thumbleft:
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Smuggler
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Re: Rudder Spacing

Post by Smuggler » Thu Apr 07, 2011 7:56 am

watersports7 You have the perfect opportunity to try out my theory :lol: :lol: Mine used to be 24" apart and I was swinging a 78" prop but when I went to re-rig it I noticed that a lot of boats swinging 78" or bigger props had rudder spacing 30"+. I asked around about it and was told that the boat will handle better if you get the rudders in the "meat" of the prop. I set my new rig up at 30" and it handles WAY better than it ever did!

My new theory is length of prop divided by 2 minus 9= rudder spacing.. So for you.. 68/2= 34-9= 25" With you being at 24 1/4" that's pretty darn close! According to the numbers it should handle way better IMO but make sure you let us know!

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HuntingBigun
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Re: Rudder Spacing

Post by HuntingBigun » Thu Apr 07, 2011 8:08 am

Smuggler too cool, Bobby said the same thing my GTO was 30, my diamondback is 32, and that sucker will turn on a dime. the prop measure 83 1/4 8)
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Re: Rudder Spacing

Post by One Eyed Gator » Thu Apr 07, 2011 8:09 am

I just rebuilt my cage have a 72" prop went with 26" rudder spacing. Very close to your theory Chris. It does drive better. Also the original cage had rudder bar support that stopped the rudder. I move those out 2" as well. I was able to make them 2" wider and now have use of the full throw of the rudder stick. Boat responses better and easier to move the stick.

Mike

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watersports7
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Re: Rudder Spacing

Post by watersports7 » Thu Apr 07, 2011 8:22 am

think the wider spacing works great with longer props, will let ya know if it improves steering/handling, (99% sure it will) the air travels several inches down the blade tip before it starts blowing out, starting to make sense now, with a 68" prop most if not all thrust was directed to the insides of rudders etc.
Like the rudder spacing theory as well, seems to be on target
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Re: Rudder Spacing

Post by Rich Andrews » Thu Apr 07, 2011 8:47 am

Like I said on an earlier post, my next boat will have X and Y axis tabs to make adjustments on the rudders. With turnbuckles and jam nuts it's absolutely feasable.
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watersports7
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Re: Rudder Spacing

Post by watersports7 » Wed Apr 13, 2011 7:47 am

almost ready for paint
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Re: Rudder Spacing

Post by Smuggler » Wed Apr 13, 2011 8:14 am

Lookin good!! Can't wait to hear how she handles!!

That's some good data on rudder spacing compared to handling! After re-running the numbers you guys posted it looks as if the magic number needs to be 10. That would put it right on the money not to mention easier to remember 8) 8)

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watersports7
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Re: Rudder Spacing

Post by watersports7 » Sun Apr 17, 2011 12:57 pm

was able to take a test run yesterday evening, the tighter rudder spacing (24" vs. 30")definately improved steering response! :thumbleft: (keep in mind, this is with a 68" prop)
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12' Predator / Lycoming 4 Cylinder / Old Skool 68x38 Stick Prop
Perfectly said by Lycoming: Some engines purr like kittens. These roar!

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