Kaboom!!!

Monday 25th August 2008. 2hr

Tidied up after priming. Assembled both aft spars. Dissassembled left leading edge. Marked leading edge ribs for position. Stripped blue vinyl from rivet lines of left leading edge skin.

It was dark by the time I finished last night, so everything was just thrown back into the shop. This evening had to start with a tidying session to make the shop habitable (and workeable) again.

I had just clecoed the parts of the two aft spars together and set up for the first rivets when I noticed that I had no pressure in the hose, even though the compressor had run normally when I switched it on and had cut out after about the right amount of time. On opening the compressor cabinet, I could see that the regulator knob was missing. I found it on the floor of the cabinet with some other parts. The pressure adjustment knob is plastic and fits to a threaded plastic moulding that screws into the top of the regulator. The knob varies the compression in a spring beneath it, which pushes through a plastic flap sitting on top of a valve between the top outlet chamber and a filter chamber below. Everything above this valve had blown off.

Nothing seemed damaged so I tried just screwing it back. No luck. It just blew again more or less immediately. Fortunately, the compressor was bought new and is just entering the last three weeks of its one year guarantee. I took the complete regulator off to return to the supplier tomorrow.

So I had to find some other jobs to make myself useful for the rest of the evening. Getting the blue vinyl off the rivet lines of the skins is always a good fallback to fill in time. As that involved disassembling the left leading edge, I went on to mark the ribs for position, using the same scheme of punch-marks beside holes that I had used for the main ribs.

Back to the Left Wing

Saturday 16th August 2008. 5hr 5min

Dimpled right wing ribs. Assembled left wing skeleton. Fitted leading edge and match-drilled ribs to spar. Fitted splice strip and match drilled to leading edge. Fitted tank and match drilled attach brackets. Match-drilled join strip to tank. Fitted top skins.

All of this was a repeat of the left wing so it happened without drama and much faster. The only difference was that I cut the join strip short to clear the wing flanges and stiffner bars, top and bottom. This still leaves way more edge distance than is needed and does not interfere with the fit of the leading edge or tank skins against the spar flanges. As I see it the join function of the join strip is to join the tank and leading edge smoothly. It has no function in joining both to the spar and it would spoil the fit if the skins if it was left long.

Winging it

Thursday 14th August 2008. 6hr 40min


Marked right wing main ribs for position. Installed W-919 joint strip and W908R leading edge rib, match-drilled to leading edge and removed for deburring and edge preparation. Fitted W-902/903 top skins and match-drilled.


With the tank still off the spar, I began the fitting of the W-908R leading edge rib and the W-919 joint strip that joins the leading edge and tank skins. This strip is sandwiched between the inside of the skin and the W-908 rib underneath. I had been dreading this job, knowing how tight the other ribs had been in the skin. However, it went quite easily. With the rib clecoed to the spar through its aft flange, I pulled the tip end well out of position, leaving about a 2" gap between it and the leading edge. Then I put the join strip in place under the skin. Because the joint strip was still not fixed in position, it was quiet easy to angle it's edge slightly upwards to allow the tip of the rib to pass underneath. As it passed under the edge of the joint strip, I paused to fix the strip in positon on the spar with edge-clamp clecoes over the flanges - the strip had not been trimmed for length and was overhanging.

Thumb pressure was all that was required to move the rib towards its proper position but the join strip wanted to move as well. Initially, I used a pliers to hold on to it while I pushed the rib but this was awkward and the pliers was marking the aluminium. Instead, I drilled through one of the forward-most pre-punched holes and the join strip. This held the strip in positon until close to the end. Eventually the rib flange hit that cleco and it had to come out to allow the rib to be moved into its final position. By this stage the surfaces are all more or less parallel so the forces involved were smaller and the strip did not move out of position.

After a bit more pushing and pulling to get everyting exactly right, I was satisfied enough to put the tank back in place and then match drill the join strip to the leading edge skin and end rib, clecoing every hole as I went. I didn't match-drill the holes for the tank attach screws just yet as I would prefer to see a perfect join with the top skins fitted before I do that.

I marked the ends of the join strip to be cut off flush with the aft edge of the tank and leading edge skins but I am not sure about this. I can't make out from the plans or the manual where the strip should be cut off. It seems to me that they should not be allowed to run aft between the tank and leading edge skins and the spar flange as that would raise these skins above the top of the upper wing skins immediately behind. However on the basis that you can always cut more but you can never put material back, I decided to cut them off flush with the aft ends of the skin for now. The strip and end rib had to come out to allow this to happen but putting them back after the cuts was easy once I knew how.



I got both sets of W-902 inboard top skins out and prepared both wing-walk doublers while I was at it. To save the worktable surface, I did this on my sacrificial sheet of chipboard, setting the forward edge of the wing-walk doublers back by the required amount from the forward edge of the W-902. Fitting the skins was a non-event as they overlap each other and simply but up against the tank and leading edge skins. Again, the join was spot on.


Though I started the match-drilling, I didn't finish out. That's a whole lot of holes! I better get Dorothy mentally prepared before we start to rivet them

It looks like a wing!

Wednesday 13th August 2008. 4hr 15min

Mounted leading edge assembly on right spar and clecoed in position. Mounted tank on right spar and clecoed in position. Match-drilled leading edge skins to ribs and spar and rib aft flanges to spar. Match drilled tank attach brackets to spar. Removed tank and fitted platenuts to tank attach ("Z") brackets

I decided not to disassemble the right skeleton, as I had done with the left, and instead I carried on to fit and match-drill all the wing skins to the skeleton. In that way, the ribs will be fully prepared before I go on to prime and assemble them. If I followed the Vans instructions exactly, I would be match-drilling, deburring and dimpling the top and bottom flanges of the ribs after final assembly of the skeleton and (presumably) after they were primed. I don't think that is a great idea. Probably, the priming would survive the deburring and dimpling but my way seems better. I am only sorry that I did not think of this before disassembling the left wing skeleton as that was a waste of time -











I needed to take the sag, which was considerable, out of the wings by stretching a fishing line between clecos inserted in the two end-most skin attach holes on the top flange of the spar. Once that was done, the join between tank and leading edge was perfect. With such a good fit, I was confident enough to go ahead and match-drill the leading edge skins to the spar and match drill up through the spar into the aft flanges of the leading edge ribs. Changing to a #12 bit for the AN3 bolts, I also match-drilled through the spar into the tank attach brackets. I didn't have a drill stop big enough for the #12 bit so I took it extra-easy to avoid punching through the back of the tank just over an inch behind.

Next step was to fit the tank attach platenuts to the tank attach brackets (three on each except the inboard one, where the platenuts go on the aft side of the spar). The manual advises that these platenuts should be fitted before the brackets are riveted to the back of the tanks as it is difficult to do afterwards. The manual is right on this point; it is difficult. However my pre-built tanks did not allow me this luxury as the brackets are already attached. The problem is that there is not enough room behind the bracket to allow the squeezer yoke to be positioned straight on to the rivet and there is certainly not enough room to hold the moving set against the outer machine head of the rivet to hold it in place before the squeeze begins. A hand squeezer would be better here, but with an air squeezer you have to start with the squeezer at a slight angle and neither set actually touching the rivet. Then, once the squeeze is completed and the yoke is firmly clamped on the bracket and squeezed rivet, everything wants to become square and parallel and in that position, the thicker end of the yoke near the U bend doesn't have enough space any more and pushes against the back of the tank, putting leverage on the bracket and twisting it out of position. Fortunately the extent of this twist is not enough to permanently move the bracket and it springs back into position (I hope).











With care and good trigger control (on the air squeezer) it is possible to get the rivets properly set. However, I was not able to get the factory head as fully flush with the surface of the bracket as I would like (nowhere near bad enough to get a finger nail under them, so not in the 'reject' class, but just not good enough). Not wanting any disturbance to the fit of the tank brackets against the spar (which would have thrown the screw - platenut alignment out and messed up the seam with the adjoining skins), I decided to shave off the tops of these rivets with a file and polish them afterwards with a small scotchbrite wheel on a die-grinder. In any case, rivets in a platenut are not actually structural. Their purpose is only to hold the platenut in position and withstand the torsional forces while the screw is being inserted. It is the screw itself that carries the structural load.

Leading with the Left

Thursday 7th August 2008. 6hr, 20min

Built wing stand. Assembled left leading edge. Received new spars. Drilled out and countersunk platenut holes on left spar.

The posts for the wing stand went up today. I left a 133" gap between them as recommended by Smitty. The advice he got was to put the brackets at 'chest height'. I interpreted this as being about arm-pit height which, for me, is 50". I am pretty certain now that this is too high for comfort by about 5"-6".


The replacement spars arrived. There had been some confusion caused by the shippers about who was paying for freight so I had to shell out €285 to take delivery, which I will get back. There is not much else for me to do at this stage so I need the spars in order to maintain progress, otherwise, I would have delayed and let them sort themselves out.

I went straight to work on them and had finished countersinking the 74 holes on the left spar by the time I finished this evening.

Sorry, no photos tonight. In fact, I don't know where I have put my camera. I suppose it will turn up.

Course Correction

Wednesday 6th August 2008, 1hr 40min

Completed reversal of leading edge ribs. Rearranged the workshop for wing construction. Glued posts for wing stand.

I wrestled the remaining ribs out of the leading edge and wrestled the correct ones in. None of them were easy - I definitely should have just disassembled the whole thing and started again. I bought more duct tape this morning so I was able to pad the saddles for the leading edge, which are now a perfect fit.

I had decided to erect the wing stand over to one side of the shop, leaving enough room to move around the back. This required me to move all three worktables across the shop to line up under the windows. With the castor arrangement, this was not a problem.

I could not find 4X4 lumber for the posts of the wing stand so I had bought 2X4s planed. This stuff was refered to in the store as "CLS". I don't know what that means but it was beautifully straight, nicely planed with radiused corners and had tight core-wood rings, indicating that it was likely to stay straight. I can't understand why it was so cheap ((€4.40 for an 8' length). Construction timber grows very fast in Ireland but it is not of a high quality like this stuff.

Anyway, I glued four lengths together in pairs back to back, with the rings on the end of the posts looking like this: [))][((]. I glued and clamped them overnight.

Wrestling with the leading edge skin

Tuesday 5th August 2008 5hrs 20 min

Drilled conduit holes in main ribs and deburred. Countersunk outboard holes in W-907A aft spars. Made Leading edge cradles. Assembled right leading edge.

I am going with the conduit option, though I have not decided what lighting set-up to go with. Not to put it in would seem to limit my options. There is no guidance as to the optimum placing of the 3/4in hole for the conduit so I placed it by eye in the centre of the area suggested by the instructions downloadable from the Vans site. I initially drilled a #40 hole and then used that to back-drill a scrap of aluminium jammed up against the lower flange and placed with its edge against the the edge of the vertical stiffening indentation - basically any landmarks that were convenient and would be the same on every rib. Using this template, I put the same #40 hole in every rib and then opened them out to 1/4in - the minimum dimension on my unibit. Then, I opened the hole out to 3/4in with the unibit before finally deburring the edges of the hole on both sides - not that they needed it much as the unibit gives a very clean hole.

Countersinking the spars was a step I had left out so I decided to catch up on it now. I had to research how to approach the need for flush rivet heads on the outboard doubler holes that go under the outboard aileron attach brackets. The .040 material of both the doubler and spar are too thin to countersink for a #30 hole though that material can be successfully dimpled. I did not want to also dimple the aft flange of the nose rib that gets riveted with these two so I decided to countersink the spar which is the 'meat' in the sandwich comprised of the doubler and the rib. This will leave a flat surface on the forward face of the spar under the rib.

The countersinking operation is standard except that the top hole is too close to the flange of the spar for the countersink cage. It is possible to cut away the flange of the cage to get closer but I did not feel like doing that so I removed the cutter and used it in the hex adapter that is normally used for the hole deburring cutter. The slow electric screwdriver was not giving good results so I switched to the the high-speed air drill. This was still not nearly as good as the countersink cage but I think it is easily good enough for this situation.
I made the cradles from the HS cradles. There is plenty of timber in them for the size of the leading edge. I used a rib to mark out the shape and then cut outside this line with a jigsaw to allow clearance for some padding. As it happened, I was out of duct tape and decided to go ahead without the padding anyway. This didn't work out so well as the cradles were loose around the leading edge. However, the blue vinyl was (just about) enough protection for the time being.

I began by attaching each rib in position on the skin with the two forward-most holes on the bottom. This was done with the skin out of the cradle and was just to fix the ribs reasonably firmly in the right positon. Next I put the assembly into the cradle, which forced the skin to wrap around the top of the ribs. Getting the rest of the holes to match up was a real pain. The temptation to use the awl was huge and I did, in fact, use it to help line things up. However, I did not exert any leverage on the holes that would have come close to damaging their edges. In any case, the match-drilling stage should sort out any minor imperfections caused by the awl.

Having done the whole leading edge, I became suspicious and found that I had the right hand leading edge skin but the ribs were for the left leading edge. They were all facing the wrong way! Swapping them around one-by one turned out to be slow. I probably should have just started again with the left skin. It took the best part of an hour to do three of the six and at that stage it was long past time to quit.

Rudder Rolling

Sunday 13th July (3 hr)

Rolled and riveted leading edge of rudder. Put in rivets at narrow end of elevator end ribs. Pop-riveted ribs at narrow end of rudder tip rib.

With a clean shop, I set about finishing off all the left-over jobs from the empennage before settling down to the wing construction phase of the project.

I decided to roll each section of the leading edge separately. These sections are defined by the hinge cut-outs that divide them. Before rolling, I put slight bend in the leading edge of the overlapping skin so that it would lie flat after riveting. Not everybody does this, especially because it is such an inconspicuous spot, but I wanted to get a feel for the process before I get to areas where it may be far more necessary. I used the Isham-supplied tool for the job and I was reasonably happy with the results. There is certainly little or no gap between the skins but the bend that I put in was a little too aggressive and is still visible. It is possible to adjust the gap between the rollers so I may try to have them a little less tight in future. Also, I will probably borrow the Avery's tool from my friend and fellow-builder Bryan Sheane and see how that compares.

For the roll itself, I used a metal tube of just under an inch in diameter. In fact, it is the bottom telecopic section of a lawn umbrella with the plastic fittings removed. This was taped on to the skin using 3M duct tape. I don't think the diameter is critical but a bigger tube will not allow you to over-bend the skin enough so that it springs back to the position you want.

I clamped a vice-grip onto the tube in the hinge openings and rolled the skin making sure that I was also exerting pressure downwards into the bend. This was to prevent any bending of the skin at the point where it crosses the forward edge of the rudder spar. The duct tape adhesive was so strong that removing it threatened to alter the bend just created but, with a little care, it eventually came off. Getting clecos in to the holes was easy at the top but a little harder near the bottom where some hand pressure was needed to get the holes to match up. From there it was a simple matter of drilling out the holes to size and putting in the correct pop-rivets.

Riveting on the skins to the narrow ends of the elevator and rudder ribs was something I had not been looking forward to and had not had any success with until now. My new masonry chisel (with the sharp edge ground off and polished) was a definite improvement. The flats on the handle made it easy to keep everything in position while the rivets were being set. I still had not located rubber grommets of the right size to put over the rivet tail so as to squeeze the skin and rivet flange together but I was able to get the corner of an edge clamp cleco onto the corner of the rib flange close to the rivet without interfering with the job.

Ultimately, however, there just is not enough space in there to set both rivets in the last position, so I had to content myself with pop-rivets on the underside of the elevators and on both sides of the rudder.

First day of 'real' building since the break - and very enjoyable it was too.