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Fixed Rudder Trim Tab


During the initial test flights it was apparent that at typical cruising speeds the aeroplane needed a slight left rudder input to centre the slip ball and thus fly in balance.

The screenshot on the left shows the degree of unbalance.


So I decided to test fit a small wedge on the aft edge of the rudder to try and centre the slip ball at cruise IAS.

I chose a location on the rudder trailing edge which would mean a wedge could be painted easily, and not be involved with the colour scheme’s red checkers or stripe.


I did a couple of test flights with a balsa wood wedge attached in position with “speed tape”.

Since the aeroplane needed slight left rudder pressure to fly in balance, the wedge needed to be on the right side of the rudder trailing edge.

Having flown airliners with various hatches secured with speed tape, I reckoned it could cope with a balsa wedge!


It didn’t need a very thick wedge to sort the issue.


Once the wedge thickness had been determined, I covered the balsa with glassfibre cloth and resin to produce a durable component.

After finishing with wet n’dry, the wedge was sprayed to match the rudder’s white colour.


I decided to bond on the wedge, and the obvious choice of adhesive was Pro-seal, so the monster had to be let out of its cage again …


… and as normal, out came the masking tape to keep it under control!

After a gentle scuff of the paint, and cleaning with isopropanol, it was time to attach the wedge.


I held it in place with tape until the pro-seal set.

I had to be sure the wedge would not slip down overnight due to gravity … that would have been a challenge to sort out without damaging the rudder’s paint finish!


Once bonded I ran a small bead of silcone sealant around the wedge to finish off the join line on the rudder.

Now she flies nicely in balance with no rudder input required at cruise speeds.

The picture below shows an IAS about 15 kts faster than normal cruise, but I was chasing 200 kts groundspeed with help of the 30kt tailwind : )


One comment on Fixed Rudder Trim Tab
  1. Marty DAlton

    Brilliant Steve, I’ll plan my paint scheme with the same foresight. 😁

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