Elevation

Sunday 25th Nov 7 hrs 45 min

Cut and edge-prepped 16 E908 stiffeners for the right Elevator. Match drilled stiffeners to E901-R skin. Dimpled Stiffeners.

Building the elevators, particularly the right elevator, is like a lot like building the rudder. Much of the time today was spent marking out and cutting the stiffeners and then preparing the edges after match-drilling. This time I didn't have to worry about the length of the stiffeners as they are all the same.

The main difference is that the skin is pre-bent so that it wants to stay closed. This makes it quite awkward to gain access to the inside, particularly if you are working alone. I am quite sure that Dorothy (my wife) would be happy to help out if asked but she was away visiting her mother as she does on most Sundays and in any case, I don't want to call on help too often so that I have lots of 'credit' left for the times when I can't do without a second pair of hands.

So I rigged the set-up you see pictured here (actually this is the left elevator). I used the wooden cradle from the horizontal stabilisers, clamped one trailing edge to the bench and placed one of my lengths of teak seating rail running between the two cradle blocks. The spring tension in the skin kept the length of teak fairly securely in place. I was working on my sacrificial slab of chipboard again as I needed to drill into the surface. The piece of scrap timber you see under the drill is placed so that the far edge just overlaps the trailing edge where it is 'indented' to allow space for the trim tab. It is screwed down into the chipboard to hold that section of the trailing edge firmly.

The tension in the skin is such that it bends up between the clamped trailing edge and the leading edge so it was important to work systematically from the trailing edge forwards and from left to right ensuring that the stiffeners hold the skin perfectly flat.

I kept the blue vinyl in place for this operation as there is a lot of potential for scratches from the stiffners whose edges have still not been polished.

Dimling the stiffeners was done with the pneumatic squeezer.

Tool Trouble

Thurs 22nd Nov 3hr 50min

Prepared edges of R-901 skins, R-913 counterbalance skin and rudder ribs. Deburred and dimpled skins and ribs. Set countersink cage for #40 holes on R-916 trailing edge extrusion.

Dimpling the last 3-4 holes at the narrow end of the R-903 and R-904 rudder ribs is very tricky. Even the pop-rivet dimple dies are no use as there is not enough separation between the flanges to get the long nail that pulls the dies together into the holes. I looked on Doug Reeves Vansairforce forums and found various approaches. One is to drill and countersink a piece of mild steel and use it as the female die to make the dimple. Another builder had adapted his DRDT2 dimpler as pictured here.

While machine countersinking the hole in the steel with the bench drill and the #40 countersink cutter mounted in the hex adapter (that I usually use for my deburring bit), I managed to break the pilot off the countersink cutter. This was because the steel piece was not held securely and the pilot jammed in the hole when it came up off the table and the hole being countersunk moved out of the vertical plane. That will mean that I can't countersink the R-916 rudder trailing edge until I replace the countersink cutter (or borrow one temporarily from someone else).

I got down to the last two holes on each rib using the pop-rivet dimple dies and I tried using the mild steel die on the final holes with the normal male #40 dimple and a light hammer. However, I am not happy with the results. The test rivet did not sit properly into the hole. This is probably because the countersink cutter did not do its job properly before I thrashed it.

The final solution I came across was from Dan Checkoway, whose own website is legendary. He says simply bend the flanges out until you can get at them and then bend them back again. However, I wonder if the metal will be work-hardened by this process. In the end, I decided to partly follow Dan's advice. I gently parted the two flanges until I could just get the female pop-rivet die and nail into the last hole. The flange sprang partly back into position once the nail was in, leaving only a small 'permanent' deflection from its normal position. Once the dimple was made, I had to spring the flange slightly further out of position to get the nail head back out. However, after all the dimples were made, I was easily able to get the flanges back to square using the flanging tool. this picture shows a test rivet sitting in the last hole of the R-903.

Left Right, Left Right

Tue. 6th November 2hrs 30min

Stripped plastic from around holes on the outside of the left HS skin. Deburred and dimpled holes. Deburred and dimpled the #40 holes on the main and nose ribs, both sides.

Yesterday, I emailed Vans support about my problem with the slightly elongated holes in the nose rib. Today, I got an answer from Bruce suggesting that I just go ahead and use the part.

I also posted a question on the RV squadron about polishing the edges in the narrow slot between the tabs and the rest of the flange on the main ribs. I got a variety of suggestions from Scotchbrite pads to 2" Scotchbrite wheels to wet&dry paper. What a great support network!

This evening, I went back to the left HS skin, which was first out of the jig, to bring it to the same stage as the right. So, I stripped off the plastic along the lines of holes, deburred and dimpled. I find the deburring bit mounted in a hex adaptor in my electric screwdriver to be very fast as it is easier to position than the dog-leg manual type. I only need to press the trigger for the briefest moment and then lift off. As the deburring bit has three flutes, one third of a revolution in full contact with the hole is enough to completely remove the burr. It is actually very difficult to restrict the tool to this. I reckon I am getting about one full revolution at a minimum. Still, the holes do not seem to be over-deburred. A deburring bit with only one sharp flute balanced by one or two rounded polished flutes would be a useful tool but I am not about to divert my attention to alter my one and only deburring bit.

This was also the first use of my pneumatic rivet squeezer. I fitted the dimple dies and used it to dimple the rib flanges. It does a superb job very quickly. I need to be careful that the die is properly positioned as it would be so easy to punch trhough beside the hole. I would have preferred to reverse the male and female die but the only way I had space to fit them was with the male die on the plunger. This meant that I was fitting the male die into the hole before pulling the trigger and the work piece would move with the plunger as it travelled up to meet the female die. I would prefer if the work piece was stationery on the male die and the female die did the moving to close the gap (I know you are all thinking up smart double entendre remarks on this theme and all I can say is "Stoppit"!). Anyway, nothing went amiss and I ended up with 16 perfectly dimpled ribs. I even managed to carefully avoid dimpling the tabs on the main ribs as they match up with the inside of the spar flange, which will be countersunk and therefore do not need a dimple in the tab underneath.

Deburred, Dimpled and De-wildered

Tue. 6th November 2hrs 30 min.

Deburred and dimpled the flange holes for skin attachment in the main and nose ribs. Stripped vinyl from left HS. Deburred and dimpled #40 holes

Smitty found that he had to buy dimple dies with a smaller diameter to dimple flanges where the hole is too close to the web. I didn’t have this problem. Perhaps my dimple dies were of a smaller diameter to start with, though they don’t look nearly as small as the ones he eventually bought. I used my pneumatic squeezer for this and it works well. It can feel a little heavy after a few minutes so I found myself sitting down and resting it on my lap as I worked.

For dimpling skins, the DRDT 2 really is a fine piece of equipment, particularly if you go to the trouble of making up the table according to the drawings they provide. I did have to adjust the height of the table in order to match the height of the lower (usually female dimple dies in their holder so that the skin being dimpled . I did this by attaching ‘skids’ planed to the necessary thickness underneath the feet of the table. I took a measurement after the top surface had been covered with carpet. You do need to be constantly vigilant in positioning the skin so that the male die goes straight through it’s intended hole. It would be so easy to miss the hole and punch straight through the skin.

Dimpled Skin

Mon. 5th November 2007 3hr 55 min

Match-drilled the Right HS. Disassembled. Prepared skin edges. Cut plastic from around holes on the outside of the Right HS skin. Deburred and dimpled the skin.

I ran into another problem this evening with the centre HS 905 nose rib on the right HS. It seems to have moved as I was changing clecoes during the match-drilling operation and I have four elongated holes. Using a digital calipers, I get a measurement of 0.1135 inches by 0.098 (the narrow dimension is correct for a #40). The corresponding holes in the skin are okay. I will have to consult Vans about this.

The DRDT2 dimpler came into its own for the first time this evening . I clamped the flat metal 'leg' at the rear to the table, which improved stability. The carpeted table also works quite well, sliding in and out nicely and adding support where you need it on larger skins like this. It does tip up when extended all the way forward because I have it on a 2ft deep table, which is not deep enough. I should have moved the other table in front of this one to give me 4ft of depth but I have the two tables set level and I did not want to disturb that. Instead I used a piece of scrap timber between the back of the table surface and the top arm of the dimpling frame, which prevented it from tipping. The results are really excellent. It just feels much better to use than whacking your skins with a hammer using the normal C frame dimpler. The motion is like pulling pints of Guiness, which I suppose is genetically implanted in all of us Irish. It is much faster and the quality is consistent. The downside is that it can't be used for riveting, unlike the C frame model. However, I think the speed and repeatable quality is a fair trade for this very rare requirement.