Elevators attached

Monday 7th April 2008 (2hr 20min)

levelled 2 benches, attached left and right elevators to HS. Checked for true.

There seem to be two risks in finishing the elevator trailing edges. the first is that you produce a hooked or wavy edge and the second is that you build in a twist so that one elevator counterbalance horn is out of trail with the HS (either high or low) when the other horn is perfectly aligned with its HS and the trailing edges are also perfectly aligned. This twist is locked in by riveting the tip ribs and trailing edges and the solution seems to be to drill out these rivets and allow the elevators to 'relax' into alignment. I planned to avoid this by having the HS and both elevators assembled and aligned while I riveted the trailing edge.

Today, I began to implement this plan. I reversed the heavy aluminium angle that I have set into the top and edge of one worktable so that the vertical flange was screwed to the side of the table and the horizontal flange was flush with the top and extending out from it. Then I attached both elevators to the HS (BTW, there seems to be plenty of space to get the bolts in if your fingers are in any way nimble). I propped up the front of the HS with some timber under its forward spar until everything was 'in trail'. With one counterbalance clamped to the HS, the other was initially just 1cm or so out of true

This was the first time I had seen these three parts assembled- the horizontal surface area of the thing is vast!

First main assembly completed - at a cost!

Monday 24th March 2008 (7hr)

Riveted R-HS top skin. Riveted inner H904 tip rib on left HS. Replaced rivets on inboard left HS rib-spar-shim-inner nose rib join. riveted outboard right HS nose rib to spar. Riveted in left HS inboard/outboard main rib. Riveted rear spar to skins and inboard/outboard main ribs.

Dorothy joined me again today to finish out the riveting of the skins. We did the right HS top skin and went back over any rivets that did not pass muster.

At this point I made one of my regular screw-ups. I riveted in the inner main ribs, beginning with the skin-rib rivets along the inboard edge of the skin . What I should have done was to begin with the nose rib-spar-shim-main rib rivets while the main rib was still mobile. The reason is that the main rib is angled inwards towards the aft end and it is very hard to get access to its forward flange. If the aft end of the main rib can be pushed back to a 90 degree angle or beyond, it would be easy to get the air squeezer in here, at least with a longeron yoke. As you can see from the first photo, I tried to access it with a double offset rivet set in the gun. This worked okay on 5 of the six rivets (though it caused a lot of scratching to the primer and one or two of them had to be done a second time). However that last rivet in the corner just wouldn't set right. When the third rivet in the same hole bent over, I abandoned it and put a rivet in a new hole right next to it - leaving plenty of edge distance.

What annoyed me most was that I had two chances to avoid this problem and missed both of them. Of course I should have followed the Vans assembly sequence more closely in the first place but, when I came across the difficulty in accessing these six rivets, I should have bitten the bullet and drilled out all the skin-rib rivets to go back to the Vans way of doing it.

I will have to see what the inspector says but if he agrees with my fix then at least the entire unsightly area will eventually be covered by the emp fairing. In the meantime, it is going to be staring at me for the rest of the project and saying "BE VERY CAREFUL IF YOU DEPART FROM THE VANS MANUAL".

Perhaps I should not have done it but I went on and riveted in the aft spar, which carries the elevators. This requires more pop-rivets into the aft flanges of the internal main ribs and solid rivets to the inboard and outboard ribs as well as the trailing edge spar-skin rivets. All of these were easily done with the air squeezer but I was not enjoying the process because of my black mood and barely celebrated the completion of the first recognisable part of the aircraft.

Good Friday

Friday 21st March 2008 (3hr 50 min)


Levelled benches for HS assembly, Riveted in the mid-span nose ribs and end ribs.











That mid span nose rib on each HS is notorious and regularly causes problems. I chose my smallest bucking bar so that I could position it properly . Even then, I could only hold the bucking bar in place with my finger tips and I could not stop it scratching against the primer on the skin or on the rib itself. Since then, I have seen where another builder cuts one inch rings from an old bicycle inner tube and stretches them over his bucking bars to protect the surrounding metalwork - sounds like a great idea. I used the flat mushroom set in the rivet gun and put some magic tape over the manufactured head.

You can see from the second photo that the primer has been scratched by the bucking bar but the rivets look okay from the outside so I am not too bothered. Nonetheless, I have ordered a new bucking bar from Avery along with a few other items that I need, as this problem will come up again. It won't get here in time for the other HS however.

The end ribs were a piece of cake as all the rivets can be squeezed with the pneumatic squeezer.

Penance for old sins

Sun 16th Dec 9hrs 30min

Countersunk HS-902-L spar and prepped edges. Cut replacement R-915 A&B stiffeners and match-drilled to rudder skin. Prepped R-915s. Made replacement HS-908 attach angles.

I did the countersinking of the HS-902 spar flanges to accept the skin dimples. This was the part where I had ruined the original part so I took it easy, making sure that the head of a size 3 countersunk rivet fitted down completely in the countersink so that it does not stop a fingernail drawn across the rivet. On this occassion I was careful to get it just right but I am not entirely certain that the skin dimples are fitting down enough, even if the rivet heads are okay. However, Vans support said clearly that the countersinks need to be set deep enough for the relevant rivets, not the dimple that sits into it.

The rudder is one of those areas where it is hard to arrange to drill through the parts that have already been match-drilled into the new parts. The skin is very floppy, even with the stiffeners clecoed to it. So, sespit what I said last Thursday, I drilled through the new part into the old. I seem to have got away with it as all the holes seem fine.

I was not happy with the second set of HS-908 attach angles. They were infinitely better than the first set but still a little smaller than the designed dimenions so, as I was having other parts sent, I decided to sport the $5 for the short length of angle required. This time, I marked very carefully and stayed well away from the lines with the bank saw. I then used a hand file and digital calipers to come right down to the exact dimensions required. Finally, I rounded off the corners to match the full-size drawings. They took a surprisingly long time as the 9 HS902/7 attach holes have to be drilled and then the angles have to be match-drilled to the HS-907 doubler and HS-902 spars. In the case of the left attach-angles, I only drilled the location hole and then did the remaining drilling throught the already match-drilled holes in the spar and doubler. Naturally, I clamped a straight edge across the two angles to ensure their bottom webs are in the same plane.

Eventually, I was happy that my HS-908s are spot on and all the other little 'oops' to date had been cleared up. Pity abut that trim tab.

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.

Countersinking feeling

Thurs 8th Nov. 3hrs 10min

Countersunk forward and aft spar flanges #40. Countersunk spar doublers and aft spar web #30.

Another evening of mistakes. Firstly, I had difficulty working out how to adjust the microstop cage and set it to the correct depth for the intended rivet. There is no measurement gauge (at least on the model I have) so this is a trial and error process and I went through a lot of scrap pieces to get it right (as I thought). Then moving on to the actual work piece, my first countersink was way bigger than the test pieces. Perhaps I did not push the drill fully home on the test pieces. The very first hole is definitely enlarged. I corrected the setting of the cage and went ahead. Looking from the top, it seemed that the countersink was removing material right through to the other side and when I put a #40 drill bit into the hole, it seemed to be very slightly undersized. I rang my inspector about this and he reckoned if that was the case then I should stop. However, when I looked at the holes very carefully with a jeweller’s loupe, I could see that the holes do indeed have a cylindrical section remaining so the countersink did not go all the way through the material. The play that I experienced between the hole and the drill bit was probably because I was using the fluted cutting end . If I had tried with the shank it would probably have been tight. Overall, I have one enlarged hole and I don’t think that will unduly affect the strength of the skin-spar join. After all, it is one of twenty or more along that flange. I will use an oops rivet or make one by slightly compressing an AD3 rivet in the squeezer so that its shank ‘thickens’ while the head remains the same size.

Next mistake was to countersink some of the wrong holes on the forward face of the aft spar doubler. I now have three additional holes that should have stayed flat. There is plenty of warning about this on builder’s sites and I did look carefully at the drawings. I just mis-identified the holes on the actual work piece. I guess I should be more liberal with my markings before I commit to removing material. In sporting parlance, this would be an ‘unforced error’. I think the best thing to do now is to use a countersink rivet in those positions. It’s strength will be similar to a universal head. It is just that the pattern of rivet heads on the finished structure will not be perfect. However this will eventually be hidden under the tailplane fairings.

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.

The HS Skeleton

Fri. 2nd November 2007 3hrs 10min

Prepared edges of HS-905 nose ribs. Adjusted flanges to 90 degrees. Straightened ribs by fluting flanges. Fabricated the HS-909 shims. Clecoed the skeleton together.

Even though there was plenty of the required .040 material in the bundle of trimmings, I was taking no chances this time. I marked out the HS-909 shims with great care, cut them out with a reasonably wide margin (about 3/32) and filed them back to the line, measuring the dimensions with a digital calipers as I came near to the final dimensions. Overkill, I know but it was as much about developing the skills of getting a part absolutely right as it was about these two minor parts. After all, the key dimension is the thickness of the metal they are made from rather than the width or height.

I held the shims in place in the ends of the appropriate ribs with side-jaw clecoes and match drilled them. I should have immediately marked them for position and orientation but I was able to match them up perfectly later on, as it turned out.

The skelleton of spars and ribs went together without any trouble and gave me a nice point on which to end the evenings work.