Now I need trimtab help

[Chrisc]

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?

[tenchiki]

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.

[Chrisc]

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.