Untwisted

Sunday 17th August 2008. 2hr 50min.

Attached platenuts to the left tank. Adjusted wing to eliminate 1/8 inch twist. Match-drilled top skins and leading edge skins to ribs and spars.

Just a short session this morning as, unusually, Dorothy is not travelling to look after her mother, so we decided to go out to visit Russborough house; a beautiful paladian mansion that most recently belonged to the Beit family and has a good art collection. Neither of us have seen it before. We both enjoyed it very much, though we are very spoiled for Georgian splendors in the Dublin area and we have more spectacular treasures at hand.

Installing the platenuts on the tank attach brackets was a simple repeat of the right wing and nothing new emerged.

However, I checked the left wing skeleton for twist using my two plumb-bobs and found that, unlike the 1/32 (negligible) twist on the right wing, I had a 1/8 twist on this one, which is outside the maximum 3/32 allowed. To fix it, I placed a short length of hardwood between the post and the bottom edge of the inboard rib so that it had to be angled slightly to go between them. I then clamped it to the post, which brought it back square and pushed this end of the wing away from the post. As both ends of the spar were clamped to the stand, this twisted the wing back towards square. With a little adjustment, I was able to completely eliminate the twist, with identical measurements from the plumb lines back to the aft spar at both ends.

I checked this set-up a number of times while match-driling as it does not seem as solid as the arrangements that other builders have used (essentially a lower bracket on both posts, made of 3X2) but it did not move.

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.

Look at those Tanks!

Tuesday 8th July

Unpacked, examined and stored pre-built tanks

Evan Johnson built my tanks! There, I said it and you know what, I don't care. In fact, EVAN JOHNSON BUILT MY TANKS AND I AM PROUD!

My esteemed Inspector highly recommended this course of action because of the number of cases he has come across of difficult leaks - during construction and also during operation. Having lost more time than I had planned to the recent home remodelling project, I was happy to recover a lot of it in this way. I should now be back on schedule and finish my wings comfortably by the end of the year.

Vans themselves used to offer this option but they now only pre-build tanks as part of a QB wing order. Evan currently charges $975 for the RV-9 tanks. Then there is the shipping cost in both directions to/from Vans and the onward shipping to you will also be a little more as there is now the weight and volume of a third crate, even though the main crate is a little lighter (not smaller).

Vans offered me the facility of taking payment and passing it on to Evan so I did not have to pay him directly.

How it works is that you tell Vans to ship the tank parts to Evan and he ships the finished tanks back to Vans where they join the rest of the wing kit for shipping on to you. He also builds a very nice shipping crate for each tank, lined with polystyrene sheeting so they arrive exactly as they left him. You need to give Evan time to do his thing. I think three months is about right but it has been much longer in the past so check with him in case his lead time has shortened further.

He recommends some extras, such as the delux fuel caps and the fancy screened fuel pick-ups. I agreed to both of these options. Of course you also have to decide on capacitance vs float fuel level senders (I went with floats as I believe the capacitance ones give different readings with different fuel types and I would like to operate on both mogas and avgas). He will also ask you to get Vans to include a quart of tank sealant.

If I was doing it again, I would probably go for the new Andair caps, which are probably better again than the delux models. These fit the original (non-delux) Vans body so it is an upgrade you can make later. However, with the Vans delux model, you get two extra lock bodies for canopy latch and ignition so you only carry one key and you can't refuel with the engine running (as if you would!)

The workmanship is first class. Check these pictures against most other builders' websites and you can see the difference straight away. The most obvious difference is that Evan has obviously sold his soul to somebody he shouldnt, in exchange for the sacred knowledge of how to do tank sealant neatly. Just as importantly, you will never see better riveting. However, just as Persian rug makers deliberately include a mistake in their delicate patterns because only God is capable of perfection, I noticed just one rivet marked "oops".

Evan is also an RV-10 builder and he loves to talk RVs or any other aviation topic. I am very happy that I have chosen this option and I can thoroughly recommend Evan.