Leading Edge/Tanks on Spars

Total time: 694.1 hours
Since Last Time: 33.0 hours
Leading Edges: 75.0 hours

This time we’ve got a two month span since the last post. The leading edges are now complete with leading edge landing/taxi lights in place. The leading edges and tanks are now on the spars. Lot’s of pictures with little to talk about.

The best thing was the birth of Amelia in early September:

 

 

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Outboard Leading Edges

Total: 544.1

Leading edges: 42 Hours
Since last time: 2.2 Hours

I drilled the holes for the tie-down eye-bolts and had an inspection from an EAA Tech. Counselor (Ralph Hoover).  He gave all good marks which I’m very pleased to report.  Nothing serious to fix or change other than to ask Van’s a question about some lateral “play” in the aileron bearings.  I sent an email to Van’s techincal support and will report what they say.  And also I noticed a very small indentation in the left leading edge – must have happened when we were riveting.  It was hard to notice to begin with and even less noticeable now.  Ralph suggested a wall-paper roller to get rid of the dent completely.

Ralph then gave me some pointers to get started on the fuel tanks.  The fuel tanks are a task I have been dreading since the day I started this project.  But they must get done.

The leading edges are not quite done yet.  I still want to install the Duckworks leading edge landing/taxi lights before fastening them to the main spar.  So we’ll be coming back to the leading edges after the tanks are complete.  I want to get on with the tanks right away because the proseal stuff I bought (for sealing the tanks) has a shelf life of only a few months.

Outboard Leading Edges

Total hours: 541.9

Leading Edges: 39.8
Since last time: 14.1

Pretty much completed the outboard leading edges.  The only thing left is to drill the hole for the tie-down bolt to fit through and to fasten them to the main wing spars.  I’m delaying this part for two reasons.  First, I’m having the EAA Tech counselor over to inspect things and it’ll be a better inspection if he can see inside the leading edges.  And second, I’m going to install leading edge landing/taxi light brackets now because they’re easier to install before the leading edges get attached to the main wing spars.  (light brackets from Duckworks).

The only thing of note was noticing that there was very little clearance between the stiffeners and the ribs.  I filed down each rib just a touch to give more clearance.  In the process, I thought I should check the stiffeners of the top wing skins.  I didn’t think to check this when I installed them.  They too showed very little clearance with a few actually in contact.  I sent an email to Van’s about this, asking if it would be OK to squeeze the bend in the J-Channel stiffeners just a little to make sure there was no contact between the stiffeners and the ribs.  They said it was probably fine as is because there would be very little pressure there, but that it would also be no problem if I squeezed them a little.  I was concerned about vibrations and cracking down the road, so I taped up some pliers and oh-so gently squeezed the bend a little bit, deforming them around the ribs enough to keep them from touching.  On the opposite side – for the bottom skins, I will file the ribs down in the spots where they will need more clearance.

Apart from that, all riveting went fine and quite fast.

 

Outboard leading edges

Total: 527.8 hours

Outboard leading edges: 25.7
Since last time: 15.5 hours

I was way overdue for a major flub and it happened.  There’s this strip of metal that goes between the outboard leading edges and the fuel tanks.  The strips get riveted to the outboard leading edge and then screwed to the tanks.  This involves the installation of a bunch of nutplates.  (A nutplate is basically a nut that gets fixed in place by rivets.)

The attach holes for these nutplates you have to countersink and the plans specifically say to machine countersink for a 3/32 flush rivet head.  Only the strip of metal is really too thin to machine countersink without expanding the hole.  I should have seen this problem despite the plans telling me what to do.  Add to this that the strip is really flexible and the end result is countersunk holes that look more like ovals than they do circles.  And the holes are way too big for the shank of the 3/32 rivet – even when the head fits perfectly flush.  I knew these countersinks were coming out very bad, but I kept going on them mostly to try and understand why (I knew they would have to be fixed).  Eventually I realized that I was allowing the thin metal to flex while running the countersink and also (and related) was that I had drilled a large hole in the wood bench to “receive” the tip end of the countersink bit.  But because it was a large hole, it did nothing to hold the bit cenetered and as a result it drifted, resulting in ovals instead of circles.

My first thought at a solution was to drill out the nut-plates to receive 1/8 rivets.  This would have worked fairly well, but would result in an edge distance issue in the nutplates which would make them prone to cracking.  Nope.  The only solution was to start over with new metal – only there was a problem with this, too.  The strips come attached to the tank skins.  Would I have to order new tank skins ( more than $115.00 each + huge shipping charges)?  The answer was no.  I contacted Ralph Hoover, EAA Tech. counsellor extraordinaire.  he advised me to by the raw aluminum and he would help me rebuild the strips.

I was worried about this because there is a particular bend in the strips.  How would this be duplicated? – not to mention the tight tolerance in the position of the holes.  The original strips would be useless because they were bent, not allowing them to be laid flat onto another piece of metal to act as a guide for the holes and I had mangled the nutplate holes anyway.  Not to worry, though.  Ralph knows how to deal with all these things.  For $7.00 + another $7.00 cutting fee (gotta love that) and shipping (low because I bundled the metal with other items I needed), I got the bare aluminum and brought it to Ralph’s shop.  He marked the bends, made some measurements, then straightened the mangled strips (apparently, you can do this).  We used the mangled strips as guides to drill holes for the attachment to the leading edge (the holes which weren’t mangled) and Ralph made a nutplate jig which in conjunction with the mangled strips allowed us to drill all the propoer holes in all the proper locations.  Lastly, he used his markings of the bends in the original strips and put what look to me like precision bends in the new strips.

Finally, instead of machine-countersinking for AN426AD3 rivets (as called for in the plans), we countersunk for NAS1097AD3 rivets.  These are “oops” rivets with 3/32 shanks and 1/16 heads.  They allow us to countersink but not go so deep, so the holes don’t get enlarged.  The new strips are perfect!  I give a very hearty thanks to Ralph Hoover for helping me fix this issue and showing me how it’s done.  It really feels bad when you mess something up.  But it feels really good to fix it the right way.

Apart from this, there was nothing all that out of the ordinary in the other work done.  Cleco, drill, deburr, dimple, etc.  Next we’ll be priming and riveting it all together.  The fix described in detail took about 4 hours.  The rest of the time was all the normal stuff.

These are the strips with the mangled holes.  Just look at them!

 

 

 

 

 

And this is what the new ones look like – beautiful:

 

 

 

 

 

And this is Ralph Hoover:

 

 

 

 

 

 

Some random pictures of the leading edge (mostly the right):

 

 

 

 

 

 

 

 

 

 

And what post could be complete without seeing a picture of Zach learning to use his new Christmas present:

Left Outboard Leading Edge

Total Hours: 512.3

Hours: 3.3
Outboard Leading Edges: 10.2

It’s been a full year since we began this project.  And it’s been a great time so far. 

In this session, Zach and I got the left outboard leading edge tucked into its cradle and all the ribs clecoed in place.  The next step is to final drill all the holes.

I learned in this step that fluting is very important.  I did flute the ribs as shown in the previous post, but several (if not all) of the ribs proved to not be fluted very well.  I had fluted the ribs so that they laid flat on their web.  But when I put them into the skin, it was very dificult to get the clecos into the holes.  They just weren’t aligned very well.  I wondered about this and looked at the ribs and realized that I need to flute so that the holes are in a straight line more so than the rib lays perfectly flat on its web.  You’d think that one implies the other, and I think it should – and does.  But there is a lot of “give” in having a it lay flat on the web.  What I found was that after I fluted to have all the holes align, the rib still laid flat.  They went right into place in the skin after this.  I also think that the flute itself allows the metal to flex a little easier so that slight misalignments in the flange of the rib work themselves into place a lot easier.

The only reason I can think that this didn’t turn up when I worked on the similar pieces of the horizontal and vertical stabilizers was that the ribs were either made of thinner aluminum (which is true if I recall correctly) and/or that fluting was not called for in the plans and was not really necessary since the ribs were all pretty straight.  Not exactly sure which (if either) of these is the answer.

Outboard Leading Edge

Total Hours: 509.0 hours

Hours: 4.0 hours
Outboard Leading Edge: 6.9 hours

Still making very slow progress.  Seems that things are constantly interrupting the build.  Oh well.  On the outboard leading edges so far we’ve got the stiffeners cut and deburred, the ribs deburred and fluted, and the four special-case ribs notched out to allow clearance for the stepped part of the main wing spars.

Leading Edge/Fuel Tank Cradle

Total time: 505 hours

Hours: 2.9 hours
Outboard Leading Edge: 2.9 hours

Very little progress this weekend.  I got parts ready for the outboard leading edge, seperated a couple of strips from the tank skins and did some edge deburring.  The most significant accomplishment this weekend was building the cradles for the leading edges.  They started out as traces on the crate the wing kit was shipped in.  I cut out on the lines, bought some 1×2 boards and screwed it all together.  This cradle will be used for the outboard leading edges and also the fuel tanks.