Rudder Trailing Edge Riveting

Sunday 20th April (4hr 45min)

Riveted rudder and left & right elevator trailing edges. Pop-riveted trim tab end tabs and trim tab horn. Match-drilled hinge to trim tab upper skin & spar and cut to length.

It is a week now since 'tank sealant day' so I went back to work and began by removing the clecos and cleaning the little stray bits of solidified tank sealant out of the dimples and holes. The edges are still laser-straight at this stage but it is the riveted end-product that counts. I did notice one place where the tank sealant was lifting the skin off the trailing edge wedge very slightly. Obviously, this was close to the end of the sealing job when the sealant was getting very stiff and lumpy and difficult to spread.

The idea here is to half set each rivet with a back-riveting set, flip it over and then finish by riveting on the manufactured head with a mushroom set. In the event, I was not very comfortable with the back-rivet set and decided to try the air squeezer with the gap set to squeeze each rivet just enough to fix it in place. I found this easier although I had to be careful to exert enough pressure on the manufactured head with the non-moving side of the squeezer to ensure it was fully seated in its dimple before it was fixed in place. I worked on every fifth rivet from the centre out and then went back to do the rest randomly.

I was very pleased with the results. I would call it perfect if it were not for that little bump caused by tank sealant and I think the edge material is microscopically dented by the action of the rivet set at each rivet site. It certainly no longer looks like pristine new aluminium sheet but I think paint will hide that completely.

Another anxiety-causing job off the list!

With time on my hands, I went on to pop rivet the control horn to the trim tab. If I had not forgotten this step before 'tank sealant day', I could have easily done these with solid rivets using the longeron yoke. In fact, I should also have solid riveted the bottom skin-spar join at that stage so that will also have to be pop-riveted. The manual quotes MK-319-BS pop rivets as an alternative here. However, I don't have enough of these rivets to cover all locations where they are called out or are an option. I will have to get 30 more from Vans.

I also put pop rivets into the ends of the trim tabs and match-drilled the hinge to the underside of the top flange of the spar. I got this dead wrong first time but fortunately caught my mistake before I had cut the hinge so I was able to re-position the hinge and match-drill again. The first set of holes won't do any harm and can be regarded as 'lightening' holes - if they are ever noticed in such a well-hidden location.

Trailing edges sealed

Saturday 12th April 2008 (5hr 40min)

Attached 2nd aluminium angle to edge of bench. Positioned HS and elevator assembly with counterbalance arms in line. drilled trailing edges to angle and clecoed. Cleared bench for rudder and rearranged shop. Cleaned AEX wedge of elevators. Cleaned skins inside trailing edge. Mixed tank sealant. Sealed in trailing edge in left and right elevators, sealed foam ribs into trim tab.
With the entire HS/elevator assembly in place on the worktables, I attached the remaining part of the aluminum angle I had bought (the first part was used on the rudder) under the trailing edge of the left elevator (now located on the right, as the assembly is upside down to allow the elevator control horns to stick up rather than down) One of the counterbalance arms had initially been about 1cm out of alignment but by the time everything was weighed down and the trailing edge clamped to the angles, it was all perfectly aligned again. I match-drilled through the trailing edge into the aluminium angle, putting a cleco in every hole. I worked from the centre outwards as I feel this is more likely to avoid any waves or curves in the trailing edges.

My drill press, bench grinder and band saw had to be cleared off the third worktable to create space for the rudder. These machines are attached to a second work surface which is cut into three sections, one for each machine. These usually just lie side by side on the worktable relying on the weight of the machines to keep them steady. I can clamp them to the work surface if I need to. Other than lifting the heavy drill press and band saw carefully for the sake of my back, it was easy to get them down off the worktable. I was pretty happy with the arrangement and pleased that I had gone to the trouble of installing them this way. BTW, the space under the table is taken up with my compressor. It is lined with two layers of scrap carpet and the front panel is removable. The compressor is an oiled belt-driven model and is fairly quiet anyway, but with this extra insulation, it makes only a little more noise than our kitchen fridge.

Before starting this morning, I went out to buy a length of wooden dowel. I used this to spread the skins slightly at the trailing edge (this is why the last three rivets at the narrow ends of the root and tip ribs are left open until now). I cleaned everything as well as I possibly could with methylated spirit, including the site of the foam ribs on the inside of the trim tab skin. Once the wedge with the sealant spread on them is in place, the dowel rod is drawn out sideways allowing the skins to close on the wedge.

Mixing the tank sealant in the cartridge took some figuring out but I got it done. I recorded the process on video with a view to posting it on Youtube after I edit it down to about 3-5 minutes. It takes quite a lot of strength to move the plunger up and down through the material in the cartridge. I wonder whether it was A) too cold (I stored it in a fridge) or B) too old. Also, once mixed, it was nowhere near as smooth as I had hoped and really quite difficult to spread on the AEX wedge surfaces. The trouble with this stuff is that once you start there is no turning back so I pressed on. I spread it as thinly as I could on the foam ribs and wedges, put them in place and clecoed and clamped them shut. By the time I got to the last trailing edge (the left elevator) the material was already clearly going off so I got the job finished just in time. I reckon it was useable for not much more than an hour after mixing. How you are supposed to carefully apply 3.5 oz of really thick muck within an hour, I really don't know. I suppose you could say that I am no longer a Proseal 'virgin' and the experience has left me feeling dirty (in fact, I am actually dirty). I will not be using the cartridge format again.

Anyway, that's it for a week until I am certain that the tank sealant has fully cured.

Movng towards the (trailing) edge

Sunday 6th April 2008 (7hr 15min)

Riveted rudder except skin-tip & root ribs - last 3 rivets top and bottom. Prepared alu angle and match drilled to rudder trailing edge. Riveted left and right elevator tip and root ribs top and bottom to skins. Cleaned trailing edge parts of rudder in preparation for tank sealant. Installed rudder counterweight.

I spent the day finishing all the remaining jobs on the rudder and both elevators to get them ready for prosealing the trailing edge. ,

Earlier, Vans had sent me the 3.5oz size in the cartridge instead of the 1 oz size that I had ordered. From all I had heard, this job is very messy so the cartridge format of the 3.5 oz seemed like a good idea and I decided to order the dispenser gun that goes with it. By the way, the only difference between the gun that Vans sells and the cheapest gun you can get at your local hardware store is in the diameter of the disk at the head of the plunger. If I had it to do again, I would find a way of reducing the diamater of this disk on a cheap gun until it fitted into the end of the proseal cartridge.

The downside of the cartridge is that it is all mixed at the same time and goes off at the same time so you have to have everything that you want to use it for set up and ready at the same time. I have a heavy aluminium angle set into the edge of one of my worktables but this was not going to be enough to do both elevator trailing edges and the rudder trailing at the same time so I had bought an extra 8' length of 35mm x 35mm x4mm aluminium angle. I cut a piece off this to suit the length of the trailing edge of the rudder and match-drilled it to the existing holes in the skins and trailing edge web.