Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 17-07-2013, 20:19   #1
Registered User
 
Chrisc's Avatar

Join Date: Aug 2006
Location: Whangamata. New Zealand
Boat: H28
Posts: 210
Now I need trimtab help

From an article on vane/trimtab geometry.


"The linkage should transfer three degree of vane movement into one degree of trim tab movement.
It should act 80% forward of the distance between trim tab pintles and rudder pintles. This is very important to provide 'feed back', which stops the system over steering. (This actually means that when 15 degrees of trim tab is applied, the rudder will move 15 degrees and at this point the rudder and trim tab will realign, so exerting no more force). If the two sets of pintles are not parallel, (i.e. if a line extended vertically through both sets of pintles will meet at some point above the yacht) then the linkage should act 80% forward of the aft pintle line, wherever the trim tab tiller is fitted. "


Unfortunately, I don't have a clue what he is talking about as it applies to me with non-parallel pintles. (see my artwork)
Can anyone explain it to me please?




Attached Thumbnails
Click image for larger version

Name:	Scan0001.jpg
Views:	81
Size:	209.4 KB
ID:	64226  
__________________
Chrisc is offline   Reply With Quote
Old 17-07-2013, 23:42   #2
Registered User

Join Date: May 2010
Location: near San Jose, CA
Boat: Yankee Dolphin 24'
Posts: 113
Re: Now I need trimtab help

Let me give it a try (though without a diagram). You need to figure out where the imaginary line that continues your main rudder pintle pins is at the height of the tiller on the trim tab. A long straight-edge clamped alongside the rudder pintles should likely work OK (Make sure it is really straight when in position!). Measure the distance from the trim-tab shaft to this line from the straight edge along the trim-tab tiller. The linkage should attach 80% of that distance along the tiller from the trim-tab shaft.

If the forward edge of the rudder is straight and parallel to the pintles all the way to the position of the trim-tab tiller (as the drawing implies), you could just measure the offset of the pintle centers from that rudder edge and use that to figure out the needed distance.

In any case, the linkage attachment needs to be *behind* the axis of the rudder pintles to get the correct feedback.
__________________
tenchiki is offline   Reply With Quote
Old 17-07-2013, 23:57   #3
Registered User
 
Chrisc's Avatar

Join Date: Aug 2006
Location: Whangamata. New Zealand
Boat: H28
Posts: 210
Re: Now I need trimtab help

Thanks for the explanation - I understand it now.
I have the rudder sitting on my workshop floor for fibre glassing, so it should be easy to set the linkage up correctly.
__________________
Chrisc is offline   Reply With Quote
Reply

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off




Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 19:56.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.