Trim tab hinged.

Saturday 26th April 2008 (2hr 10min)

Bent and cut trim tab hinge pin. Trimmed and fitted elevator counterbalance weights.

Bending the hinge pin is not as easy as you would imagine. I marked where I wanted the centre of the first bend to be and heated the spot with a plumbers buthane blow torch until it was bright orange. By now the mark had dissapeared of course but I guessed that the centre of the heated area was the intended centre of the bend. Using my long -nose pliers, I grabbed the pin to the outside of what I thought was the centre point and twisted it over to create the tightest right-angle bend I could manage. it was surprising how much force it still needed and how quickly it regained its strength as it cooled.

Now, with the pin back in the hinge and the right-angled part hanging down ofer the inboard edge of the elevator, I marked where I wanted the centre of the next bend - about an 1/8th from the trim tab spar. Once again, the mark served only as an aiming point for the blow torch but the bend worked out just fine. It only remained to mark and cut off the unwanted tail and clean up the end on the Scotchbrite wheel. The finished item sits beautifully against the elevator trim spar.

I would like to have done as builders of other models have done and use one 'ear' from the hinge scrap screwed into a nutplate to hold the hinge wire in place. However, there does not seem to be enough space for the nutplate at the end of the trim spar on the forward side so I will probably have to just safety wire it as per the plans. I will leave this until later in case I think of some way around the problem.

The trim tab bottom skin's forward edge was interfering with the aft edge of the bottom skin and spar of the elevator, so I needed to bend this upward so that it just cleared this obstruction when the trim tab is deflected downward. I found the best way of doing this was to take the trim tab off and bend the entire length of the skin edge at the same time by pressing it against my bench.

I have heard of builders having problems in sawing the counterbalance weights because the band saw blade starts melting the lead. I saw no sign of this problem, maybe because my blade travels slower or because of the 16 tpi pitch. I did need to file some material from the top and bottom edges of the weights to get them to fit inside the flanges and rivets of the counterbalance arm webs. I hope this will not be a problem when it comes to balancing the elevators at final assembly. The weights are supposed to be too heavy so that material is removed rather than added in order to achieve balance.
I torqued up the nuts to 25 in-lbs and used Loctite to secure them.

Trim tab hinge

Tuesday 22nd April 2008 (1hr 15min)


Riveted hinge to trim tab skin and top spar flange. Match-drilled hinge to left elevator trim spar.

I used my air squeezer for the easy job of putting in the solid rivets to join the hinge, spar and top skin. The other part of the hinge had not yet been trimmed to length at this stage.

You can see from the paint on my overalls that I have already begun to get involved in the remodelling job in our reception rooms. Dorothy started on this a few weeks ago and it has long been planned that I would join in for the six to eight weeks that the wing kit will be en route to get here. In fact, the kit is already shipped so I am racing to get the emp finished quickly before Dorothy gets to the bits that she can't do on her own.

Next, I joined the two halves of the hinge and positioned the trim tab and hinge on the elevator, using a level as a straight edge to align the trailing edges. It's nice to have the inboard edges match up but it is more important to get the minimum 3/32 inch clearance in the gap between the outboard edge of the trim tab and the adjoining edge of the elevator trailing edge. I just about got away with it as the bend of the end tabs of the trim tab are not razor sharp so the ends bulge out a tiny bit further than they should, adding slightly to the overall length.

I clamped the hinge to the underside of the elevator trim spar at the inboard end only, using an edge-clamp cleco. This held things well enough to match-drill the first hole. From there, I just put clecos in every hole as it was drilled. I felt no need to support the hinge up under the trim spar along its full length for this operation.

Once finished, I drew out the pin and cut off the extra length of the hinge, leving a margin which I filed back flush with the inboard edge of the elevator and then polished up with the scotchbrite 1" wheel in the die grinder.