Thin-end rivets

Wednesday 30th April 2008 (1hr)

Set last rivets at narrow end of elevator root and tip ribs except for the very last ones. Experimented with techniques for these last rivets.

The long-nose no-hole yoke is the obvious tool for this job and does well up to a point (yes that was a pun) where there is just not enough room for the unsqueezed shop end of the rivet as well as the pointy end of the yoke within the flanges of the rib down near the trailing edge.


On most of them, I was able to get the yoke nose in as long as the rivet was not fully inserted. You are then depending on getting the moving rivet set to push the rivet home as it closes before finally setting the rivet at the end of its travel. To do this, you have to have pretty good trigger control skills to get the squeezer to close slowly. Even then, I found that the skin and rib were not tight to each other at the point where the rivet set enough to grab the inside of the holes. These all had to be drilled out, leaving me with only one of the eight where the results were okay. To make matters worse, if you do happen to get one of these set, the rivet head now restricts the space further for setting the rivet on the surface opposite.


I decided to try the 'lever' method so I put some tape around the end of a piece of flat steel bar that I had. However, this wasn't really stiff enough to set the rivet properly, leading to some more drilled out rivets. I will have to look at using a wide 'bolster' masonry chisel, which should be really hard while still being thin enough to get into the space available. Also, I need a rubber grommet with a thickness closely matching the projecting shop tail of the rivet. Placed over the rivet tail, this will push down on the rib flange making sure that the two materials are in close contact as the rivet 'bites'.

That's it with the project for the moment. I really need to help Dorothy out with the remodelling job so I will have to stop work until that is done and the wings arrive. I still have these rivets to finish plus I haven't rolled the forward edge of the rudder skins. Still, building a plane doesn't mean you are no longer a member of the family and duty calls.

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.

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.

The Bends at the Ends

Thursday 13th March 3hr 15min

Ordered replacement R710. Made new blocks. Practiced and then completed trim tab end bends. Match-drilled end tabs. Assembled bending break and completed trailing edge bend.

I found that I had edge distance problems with the R-710 rudder brace, as can be seen from the photo. This happened because I didn't like the half holes left after trimming off the cheeks and I ground down the edges until they were completely gone. The cut lines are supposed to go between the CENTRES of these guide holes. Fortunately, I had left the spray booth in place so it was not difficult to prime up the new part.

The infamous trim tab end bends went much more smoothly this time. Firstly, I made much wider blocks to hold the skins for the bend. Secondly, I used double-sided tape (the white take in the photo. to make sure the skins stayed put in the blocks while the bending was going on. Thirdly, I left out the rivet gun shown in the manual and made the bends by pushing on the tabs with a piece of scrap wood. The resulting bends could be a little sharper but they are in the right place at least and they don't look as if they were beaten with a crow-bar.

I wouldn't use that particular type of double-sided tape however. It consists of a thin layer of foam with a glossy paper layer on each side that you pull off when you are ready to use it. The problem is that the glue is much stronger than the foam tape itself and it was really difficult to get off, particularly inside the trailing edge where access was difficult.

Finishing the Trim Tab Preparation

Tue 10th Dec 2hr 30 min

Prepared the trim tab skin and spar edges. Deburred spar and skin. Countersunk the spar top flange and dimpled the bottom flange holes. Prepared and dimpled the horn pieces. Assembled HS-902 r & L with the HS-907 doubler and match-drilled them.

While I am thinking about getting a replacement trim tab skin, I went ahead and prepped this one, in case I decide to use it. This is not the easiest of jobs. It would have been better to prep the edges at the end of the skin before bending the tabs for instance. I tackled the leading edges initially with the spar clecoed in. This was okay for the lower edge but the spar was interfering with getting a good surface on the upper edge so I disassembled it and worked 'free-hand' with the small Scotchbrite wheel in the die grinder.

There is no more I can do on the trim tab for the moment so I began work on the recently arrived replacement parts. I started with the HS-902 L and R and the HS-907 front spar doubler. The trick here (and in any situation where you are preparing replacement parts) is to use the holes in the parts that have not been replaced as the 'master' holes for match-drilling the new part. If you drill from the new part into the old, you can get mismatched elongated holes. In this case, there was no problem on the right as both the spar and doubler were new but I was careful to drill from the aft side through the spar into the doubler on the left. This is the opposite direction to the original match-drilling.

Trim tab - Another right mess

Sun 9th Dec 3hrs 10Min

Made bending break. Masked and sanded the site of the trim tab foam ribs. Trimmed the trim tab horns and match-drilled. Completed the Trim Tab trailing edge skin bend. Made blocks and bent end tabs. Match-drilled ends and skin to spar holes.

The replacement HS-902 and HS-907 arrived during the week along with the angle needed to make replacement R-915 A&B stiffeners and the angle to make a third(!) set of HS-908 attach angles. I am looking forward to preparing these pieces and eliminating all my past sins. However, I scarcely have the replacement pieces in my hands when I mess up another piece. This time it is the trim tab skin, but more of that later.

I made the bending break from two of my shelves as they were the only pieces of timber I had of about the right side. They in turn had been made from scraps of half-inch ply that I had left over from building the workshop and I had glued two thicknesses together to get the stiffness I needed for the shelves. The bend was not as smooth as I expected and it seemed to vary depending on where I had leaned on the break. However, I got it straight with a bit of trial and error. When I inserted the spar, I found that it was a little over-bent so I put it over the edge of another piece of half-inch ply and pushed gently down on the trailing edge. This spread the bend out a little until the spar fitted perfectly in position at the 'open' leading edge.

The manual shows pictures of the set-up for bending the tabs on the skin to form the ends of the trim tab. This is done using interlocking blocks, one of which is cut to go inside the skin and the other goes on top. The whole assembly is positioned on the edge of a bench and clamped tightly. Another picture shows the tab being bent with a mushroom set in a rivet gun. I also watched the Orndorff DVD again but George just refers to having bent the tabs using his flanging tool. I decided to go with the Vans procedure so I made the interlocking blocks from three-quarter inch MDF that I had lying around, clamped it all up and went at it initially with a timber block and a hammer and then finished off with the rivet gun.

To say the least of it, the results are not good. There were two problems. Firstly, despite heavy clamping, the blocks moved slightly, so the first bend did not end up on the line where it was supposed to be. Secondly, the rivet gun hammered the hell out of the skin leaving it over-bent and all dinged up. Maybe the part is okay from a functional point of view and the problems are only really visible at the edges but I don't think I can live with it.

Afterwards, I searched the forums for other people's ideas. The Orndorff video simply refers to using the flanging tool to make the bends but does not show it. I found that lots of builders have problems with this task, so much so that the replacement skin is with the accessories in the main on-line store rather in "the list" with virtually all of the other kit parts. Those who have done the job successfully are using timber blocks that are much thicker than mine - up to 2 inches. Some have also suggested using double-sided scotch tape between the skin and the blocks to prevent movement. Too bloody late now of course.