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Robert H. Wilkinson



Joined: 26 Jan 2011
Posts: 1231
City/Region: Port Ryerse
State or Province: ON
Vessel Name: Romakeme IV
Photos: Romakeme IV
PostPosted: Mon Mar 08, 2021 9:38 pm    Post subject: Re: Docking Reply with quote

digger wrote:
having trim tabs at full down will improve the docking control.


I remember reading a thread somewhere once that suggested dropping the tab on the side that you wanted boat to turn. Assume using the tabs drag.

Was just researching tabs yesterday and saw where Smart Tabs offer a bracket where you can drop tab straight down(90deg.) to bottom. This to act as a trolling plate.

I assume the theory is to increase control by reducing way while maintaining the same thrust.

Rob

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localboy



Joined: 30 Sep 2006
Posts: 4656
City/Region: Lake Stevens via Honolulu
State or Province: WA
C-Dory Year: 2007
C-Dory Model: 25 Cruiser
Vessel Name: 'Au Kai (Ocean Traveler)
Photos: 'AU KAI
PostPosted: Wed Mar 10, 2021 2:52 pm    Post subject: Reply with quote

Personally, I don't believe the Permatrim helps any in slow speed maneuvering (we have one on our 25). Those two small "skegs" on each side of the Permatrim are very small, perhaps 2" deep. Control surfaces they ain't. Again, just my opinion. If the prop isn't turning, even at idle speeds, you have zero control anyway.

The only reason I put the Permatrim on is 25's are very stern heavy. Fuel tank, water tank, batteries, engine(s), cooler etc, all at the back of the boat. When on long trips the boat is very heavy and I can tell when handling as the boat lugs up onto plane and throws one hell of a wake. Does the Permatrim help? I don't know. Anecdotally, sure. But do I have science or numbers to prove it? Nope. I'm not an engineer nor physicist.

We use the trim tabs to:
-fine tune the roll or side to side out of balance once underway
-to force the bow down in lousy conditions, should the need arise

The second can effect speed and fuel efficiency, but not enough to avoid using them when faced with chop etc.

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ssobol



Joined: 27 Oct 2012
Posts: 3362
City/Region: SW Michigan
State or Province: MI
C-Dory Year: 2008
C-Dory Model: 22 Cruiser
Vessel Name: SoBELLE
Photos: SoBelle
PostPosted: Wed Mar 10, 2021 4:01 pm    Post subject: Re: Docking Reply with quote

Robert H. Wilkinson wrote:
... I remember reading a thread somewhere once that suggested dropping the tab on the side that you wanted boat to turn. Assume using the tabs drag. ...


Seems that the tab lifting that side up would eliminate some of the hull drag on that side. So the effect might be a wash.

Also, on my boat the tabs do not really move fast enough to make changing their position to aid turning worth it. Maybe if you were making long sweeping turns, but then the turn rate would be low.

Lowering the tabs might be of some use if you lost steering control. But with a 22 you can just walk (step) from one side of the boat to the other. It is faster and has greater effect.
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