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akerman angles 8-10degrees? #175321
04/20/09 06:52 AM
04/20/09 06:52 AM
Joined: Sep 2007
Posts: 757
japan
erice Offline OP
old hand
erice  Offline OP
old hand

Joined: Sep 2007
Posts: 757
japan
so i'm slowly catching up on lots of little improvements to my old cat. yesterday pulled off all the tell-tales and moved them so they are now a foot, 300mm, back from the mast instead of 3 foot, 900mm

my old 5.2 has straight tiller arms but the later versions had inwardly cranked tiller arms, presumably for the "akerman" effect where in a turn as the inner rudder is turning a smaller circle, (than the outer rudder) it needs to turn a tighter angle for minimum drag

from google it looks like "akerman" cat tillers are each cranked/bent 8-10degrees inwards

is that about right and how hard would it be to safely crank my straight tillers? take it to a pro.shop with a correctly radiused bending rig???

Last edited by erice; 04/20/09 06:54 AM.

eric e
1982 nacra 5.2 - 2158
2009 weta tri - 294
-- Have You Seen This? --
Re: akerman angles 8-10degrees? [Re: erice] #175328
04/20/09 07:52 AM
04/20/09 07:52 AM

S
Scarecrow
Unregistered
Scarecrow
Unregistered
S



Cat steering akerman is a "black art" and there is no correct amount as it changes with beam, speed and rate of turn.

Re: akerman angles 8-10degrees? [Re: erice] #175370
04/20/09 11:33 AM
04/20/09 11:33 AM
Joined: Jun 2001
Posts: 623
Gulf Coast
tami Offline
addict
tami  Offline
addict

Joined: Jun 2001
Posts: 623
Gulf Coast
Start with seven degrees, as you're on a narrow beam boat. 'Tis easier to bend more than to unbend. That, and it is difficult to add the metal back to your tiller crossbar, as you'll have to shorten it to accommodate the bent tillers.

I used a fencepost and worked slowly and gently, and I have tiller arms just like yours, having a 1982 NACRA Square.

Last edited by tami; 04/20/09 11:34 AM.
Re: akerman angles 8-10degrees? [Re: tami] #175409
04/20/09 02:00 PM
04/20/09 02:00 PM
Joined: Jul 2006
Posts: 304
H
Hullflyer1 Offline
enthusiast
Hullflyer1  Offline
enthusiast
H

Joined: Jul 2006
Posts: 304
New arms with angle 31" long from Performance $31 each. Part#5551. Nacra 5.2 and 5.8 are the same arms.

Re: akerman angles 8-10degrees? [Re: Hullflyer1] #175410
04/20/09 02:01 PM
04/20/09 02:01 PM
Joined: Jun 2001
Posts: 623
Gulf Coast
tami Offline
addict
tami  Offline
addict

Joined: Jun 2001
Posts: 623
Gulf Coast
You gonna hurt my last feeling if you tell me these arms have been out for, like, years...


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