June 21, 2008

  • Wow,
    three months since my last update.  In that time, I have made some
    progress but in the process I had to learn A LOT!  After finishing the
    channel under the front section, I decided to build the rudder bar.  This
    proved to be a lot more challenging than I thought it would be.  I built
    them according to the plans, but had to start over three times to get it
    right.  I started by welding up the pedals, that was ok.  I am going
    to have toe brakes on both sides so I had to change the set up a little. 
    Basically, the copilot side needed removable toe pieces like the pilot side.
    Also, I added a finger strap to the top of each pedal (not shown on the
    plans.  Then came the trouble.  I first welded the “V” that connects
    the two sides together.  My plan was to weld that to the longer of the two
    rudder bar tubes and cut out the section for the right pilot pedal.  The
    problem arose when final welding, it kept cracking!  Finally after some
    advice from Supercub.org, I got the sequence down and no cracks.  Getting
    everything to fit and turn was a pain; 4130 will not stay straight when
    welded.  I finally got everything turning ok and it was time to make the
    attachment hardware.  I made a set of the “U” shaped connectors but did
    not like the metal to metal contact.  After a bunch of research, I settled
    on making pillow blocks out of UMHW Polyethylene.  As my research made a
    full circle, I discovered that the RV aircraft have been using this method for
    a while now so I felt good about the change.  One problem, how much friction
    in the pedals is too much?  So, on to
    build the rudder and tail fin. 

    To
    build the rudder, I needed ribs.  These
    were made from 22g mild steel, bend to a taper. 
    So, I needed a bending break.  So,
    I built one. Than, I needed to bend the 15 degree edge on each rib.  So, I made a wood bending block for each rib
    with proper taper and angle.  All in all,
    I spent about a month figuring all this out and getting materials together.  Making each rib turned out to be very easy,
    about a half hour for each. 

    So,
    I set up the table and built the tail fin and rudder using the same kind of
    blocking method used in building the fuselage. 
    With the fin and rudder finished (except for hinge) I now am trying to
    figure out how to enlarge the ends of the stabilizer leading edge tube to
    accept the connecting tube.  At this
    writing, I have no idea how to accomplish this task.  Stay tuned.

    Below are pictures of the rudder bar construction along with rudder and tail fin.

      

    Rudder pedal and cable connector tube and rudder bar with most parts in place.

    Ready to weld the V.  Gap must be maintained to keep weld from cracking as weld expands and cools.

     

    Using a saw blade to maintain the gap at final welding

    Rudder bar clamped in place with wood blocks for pillow block bearings.

    Clamped in place with final pillow blocks

    Making ribs using home made bender.

    First bend followed by bending the 15 degree bevel with wood bending block inside.

     
     

    Finished rib.

     

    Welding the washers and bushing for tail brace wires.

      

    Ready to weld and welded.

    Bending the trailing edge of the rudder.  I actually bent this around the tree in my front yard to get the correct bend!

    Ready to fit other parts in place.

    Support wire welded in place followed by top of spar.

     

    The welding process............. blocked than tack welded on table.
                      

    Rudder horn made from .090 4130.  Make sure to leave extra metal on the tabs before bending and than trim off extra.  I didn't do that ................. this is the second one I made!

    Rudder in place ready for hinge and rudder horn.

    Below is an idea to redesign the stab tube to eliminate the need to swage the ends of the tube.  Any comments?