Twisted: Week 162 (2) - Flap drive and Canopy

Hours to date: 1460.5

Onto the dreaded flap drive job!

Well to be honest so far it has not been too bad at all.

First thing to do was put a 6mm thread into the flap securing bracket on the wings. Easily done with the drill method (as described in a much earlier post about the elevators). The manual is a bit confusing here as it states a 372mm distance in the text (between the trailing edge of the flap and the trailing edge of the wing) then states 370mm in the diagram. I went for 371mm.

To make things easier to move around I decided to put the Twister on all 3 wheels for the first time.

Onto the flap drive - I spoke to Johan in Belgium first to see if he could offer any advice or 'gotcha's'. As it turns out he described the method that I was going to use anyway but added something really helpful - thanks Johan!

That extra something was the use of a straight rod (or tube as in my case) as a device to get the holes lined up before drilling out to their final size.

As you will see below it worked out really well and I only have a 1 to 2mm gap in the safety cell holes to the flap torque tube.

The photos below better describe the method so please see them to understand how it was done.

I found out afterwards that the torque tube supplied was 24mm too long. A careful bit of measuring and cutting later had it to the right length.

I then riveted one end of the flap drive onto the end of the tube (as per the instructions). The other end is riveted on after the aircraft is painted.

I made up the flap torque tube drive and pre drilled my holes to secure that in the drive arm to make life easier later on.

Good news is - I finally got the Port wing on and the spar pin in. This allowed me to fix the rear wing pin bearing and also fit the front wing pin bearing after that. All that's left to do now is fit that wing to the fuselage (by filling the gap with flock).

The starboard wing has not proved so straightforward. I spent the better part of a day trying to get it to fit and ending up finding out it was the front wing pin that was fouling on the wing inside. I've fixed that and it should be okay to fit now.

But before I do I'll need to fix the rear wing pin bearing on that side too as I found out that it was 1mm out. So the lesson here is - do not fit your wing pin bearings in the factory drilled holes! Wait until you can put your wings on and do it then.

I'll end this post by talking about the canopy.

I've made up the retaining cable - using a Swaging tool for the first time - things worked out good.

The manual states that you need to fit two threaded hooks (one in the canopy frame and the other onto the fuse on the inside) as securing devices for the retaining cable. Guess what? They were not included on my kit so I had to make a trip down to my hardware store to buy some - best to do this job before fitting the perspex to the frame as it would be impossible to drill a pilot hole afterwards.

After many many hours of fitting the perspex to the frame I was finally ready to bond it in place - a very long and frustrating job doing the fitting - take your time and be patient (lots of sessions rather than trying to do it in one go).

I masked off the canopy frame (where it was painted) with duct tape.

I also masked off the inside of the perspex - where I had previously put masking tape (as a guide of where to key up the edge to be bonded).

Finally when all of this was done and the frame was cleaned with Acetone - and the perspex with meths (do NOT use Acetone on the perspex it will graze it and most likely melt it!).

Following Pete's advice I carefully drilled 4 holes into the perspex and frame on the 4 corners (1.5mm holes) for some securing nails. These are then waxed for releasing.

Then I mixed up a heap of flock (175 grams to be precise) and put that all around the frame edge where the perspex would bond to it. I thought I had overdone the flock and put too much on but it turns out that was just the right amount - I only ended up scrapping about 25-35 grams off afterwards.

With the help of my brother we lowered the canopy carefully onto the frame - lining up with previously marked lines front and back.

After that I just gently pressed the frame in all round and then crawled inside the fuse (through the baggage bay end hole) and scrapped off the excess flock on the inside with a sharpened stirring stick.

As you will see below one area would not sit flush with the frame so I resorted to gently pressing it in place with a block of wood while it set.

We'll see how it all turned out next time I post!

6mm thread cut into the flap securing bracket.

On all 3 wheels for the first time!

Determining position of holes for the flap torque tube by putting the end attachments on the flaps and sliding the wings on and marking where they touch on the fuse root.

Using a straight tube to determine where to drill out the safety cell hole - remember that the fuse wing root is not straight - dihedral! Use a spirit level to get the tube square.