Rudder Trim Tab – Additional Details

2-14-2018 – 3.5 hours and 2-15-2018 0.5 hours.  Total 4 hours.

Confession time – I’m just guessing at hours.  It isn’t simple, because I am also teaching full time while I am working on the plane.  So I just guess at the number of hours I got in, and the number of hours that were spent answering student questions and keeping students from chopping fingers off.

So let’s get on to today’s work – completing the rudder trim tab from the parts I made yesterday…

The first thing I had to work on today was adding a way to remove and install the hinge pin.  This involves drilling 2 holes in the rudder – one through a stiffener and one through the bottom rib.  Note the sheet of folded 0.060 aluminum also in the picture.  This is what I intend to make the control horn from.  It has a wide radius bend, as this has a large minimum bend radius.

Here is the route plan for the hinge pin install/removal holes.

Here you can see the hinge pin emerging from the holes.  Now it is on to making the control horn for the tab.

Here is my first attempt at the control horn.  It is folded from 0.060 2024-T3, and looks great.  The only problem is that I would have to cut into the rudder spar to make it work properly.  FAIL.

Another view of my failure.

Here is the control horn 2.0 being planned.  I used another one of the 2024-T3 fittings that I had.  It has a sharper bend, so I can tighten up the location and make it open and close.

Here is the completed control hon, with most of the riveting done.  (Picture out of sequence.)  The horn should be aligned/streamlined with the direction of travel.

And now its time to talk about riveting.  I planned my riveting poorly, and ended up having to set the rivets with odd shaped bucking bars – one at a time.  I have all but three of the rivets set now, and will bring a thin bar clamp to use as a bucking bar for those last three rivets tomorrow.  (See the picture of the complete trim tab control horn with its missing rivets.)  I will not cut in the access panel for the servo or the control arm slots until I have the servo in hand.

Just a little more piddling around, and I will have my first trim tab completion done.  The extra dimpled holes in the skin will have to be filled before paint.

So I went back in today (2/15/2018) and got those last 3 rivets.  Here is the bar clamp I referred to.  Note that it makes a long bucking bar that covers the entire rivet seem.  It did take quite a few more blows to buck the rivets, but they went in.  Rudder trim tab is done except finishing!


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