April 2009 Archives

The epoxy took too long to cure last night (even with the 205, fast hardener) to make any more progress, so I came out this morning to put the glass in place.  I used two pieces on each size of lightweight 1.45 oz cloth (the flexible stuff you see hanging off the sides).  I covered it all with peel ply (dacron) which is the stiffer looking cloth you see in the middle.



After work, I peeled off the peel-ply and trimmed the overhanging fiberglass.  Looks pretty good for a first effort.



I also mixed up some epoxy with some WS410 (microlight fairing filter) and filled the open end.  I'll sand this back to prove a concave surface to allow the rudder to swing freely while still providing a tight joint.



I attached the fairing last night with some pop rivets (sorry, no pictures), and put a layer of the 1.45oz/yd fabric over the joint.  This morning, I removed the peel-ply and did a little sanding.  The joint looks pretty smooth now, but with a little lightweight filler, this will be sweet!



I dimpled the left elevator skin in preparation for riveting.



I did a little more work on the trim tab tonight too.  It's hard to see here because of all the clecos and cleco clamps, but the trim tab horns have been match drilled to the trim tab skin.



Left Elevator Riveted

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I riveted the left elevator skin to the structure and bolted on the counterweight.



Here's a shot of the complex intersections of the spar, counterweight rib, elevator skin and counterweight skin.  These rivets turned out even nicer than on the right elevator.



I did a little more prep on the trim tab as well.  Here are the holes in the trim tab spar, countersunk to accept the skin dimples.  These are countersunk because the trim tab hinge will mount flush to the underside of this flange.



Elevator Trim Tab

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I worked all day today, but managed to make a little bit of progress on the elevator trim tab.  I positioned and drilled the hinge to the trim tab.



I attached the trim tab servo to get it out of the way.



I prepped and primed the parts for the trim tab.  I can't start riveting these tonight since the spar is back-riveted onto the skin and that will make too much noise.



Elevator Trim Tab

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I back-riveted the row of rivets attaching the trim tab spar to the bottom of the trim tab.  I also back riveted the trim tab horn on.  I left out the rivets along the edge on each end so that the rib I'll be fabricating can rivet through that as well.



I used a long piece of aluminum angle to ensure the trailing edge of the trim tab aligns with the trailing edge of the elevator (and ensured the inboard edges are aligned).



Elevator Trim Tab

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I drilled the forward part of the hinge to to elevator.  The clearance between the elevator and trim tab (below my thumb) is intentionally too tight right now.  I'll file this back to the recommended minimum clearance of 3/32".



Since I'm deviating from the plans and cut off the ears on the elevator and trim tab that are normally folded over to close off the end, I started trying to fabricate the ribs that will be used instead.  Here's the rib that will fit in the end of the elevator.



And here it is installed.  Luckily, the first one I made fit really well.  I tried making one for the end of the trim tab, but that will need to be remade.  Fortunately by doing it this way, if you screw up, you're only wasting a few cents in aluminum instead of a large part that requires an order from Van's to replace.



My buddy Andre stopped by tonight to help me roll the leading edges of the elevators.  They turned out better than the rudder, but this is still a pretty non-precision part of the construction.  My hands are killing me after this, so I'm done for the night.



I did a little fine tuning of the leading edges and installed the pop rivets.  I also installed the bearings into both elevators.  Here's one of them (I don't know which), but they all look about the same.  Basically, you screw these in until the center of the bearing is 13/16" away from the spar face.  It's not hard to be precise since one too many or one too few half turns is obviously off of 13/16"



Here's another one.  This is the inboard bearing (the spar is wider at this point since all of the empennage surfaces taper as they move from the root to the tip).  Overall, I'm pretty happy with how the rolled leading edges turned out.  There is no puckering between the rivets as I've heard a number of builders complain about.  You really want to get the edges to lie flat against each other when the holes line up.  Also, putting a small roll in the top edge really helps.  I purchased the Cleaveland Tools edge rolling tool, and I'm really happy with it.



Now that I have the trim tab mounted and I'm happy with the alignment, I cut off the inboard ears inline with the inboard edge of the elevator.  I still have to fabricate a small rib to fit in here. 



I also opened up the gap between the trim tab and elevator to 2/32".  Van's specifies the minimum gap as 3/32", but that's with folded ends and rivets that could conceivably interfere if something ever moved or flexed.  Since I'm using ribs here, nothing could move to decrease the clearance (There actually is a small amount of side to side play in the hinge, but the 2/32" clearance is with the trim tab pushed as close to the elevator as possible.  The actual clearance varies from 2/32" to almost 3/32").  Even if hinge wear theoretically allows greater play at some point in the future, I could always increase the clearance here by filing these edges back a little further (definitely not an option with the folded ends).



Here's another shot of the elevator rib.  This picture makes it look like there's a gap on the top edge, but the rivets will pull this down flush.



Here's the second rib I fabricated for the outboard end of the trim tab.  The first was way off, but this fits perfectly.  I still need to dimple all of this which is why the little ear on the left isn't sitting flat.  It was a little more work to make the ribs have these little ears to tie in to the spar, but I think it's well worth it to reduce the potential for flex and cracking.

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Trim Tab Rib

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I fabricated the inboard trim tab rib.  Just like the outboard one, it took two tries before I was happy with the fit.  It's easy enough to make the paper template accurate, but it takes a bit of practice to determine where to start the bend so that it winds up in the right spot.



I finished riveting the trim tab with the exception of a couple of pop rivets that I need to order.  I'm really happy with how this turned out.  It's not perfect, and I'm sure I could do better after I get more experience, but it turned out really well.



Here is the bottom side with the trim servo hooked up.  I'm not getting anywhere near the +25º/-35º travel the manual states is optimal, so I'll have to call Van's about that, but at least it's all hooked up and working.



Here's a closeup of the trim tab push rod.  I'll probably need to file the edges of the opening in the elevator to get a little more clearance, but that can wait.



I pulled down the rudder and fit in to the vertical stabilizer.  The clearance between the vertical stabilizer tip and rudder counterbalance skin is too tight right now, but I'll open it up a bit when I do more of the fiberglass work.



The gap between the lower edge of the counterbalance skin and the upper edge of the vertical stabilizer is nice and uniform though.



Next I got started on fitting the elevators to the horizontal stabilizer.  The horizontal stabilizer skin needs to be trimmed a bit to allow the elevator counterweights to clear, so I marked and trimmed the extra off.



The lower portion of the rear spar flange also has to be trimmed to clear the elevator horns.  This is tricky because you really don't want to nick the spar reinforcing bars just behind the flange.  I stuck an extra strip of 0.032" aluminum under there when using the dremel tool to give me a little insurance.  Worked great; clean cut and no nicks on the reinforcing bars.



Here are both elevators fit to the horizontal stabilizer.  It looks so cool to finally see some big parts taking shape.



I purchased a drill bushing from McMaster-Carr to ensure the elevator horns were drilled directly inline with the center bearing.  The bushing was a couple of thousandths too large to fit in the center bearing, so I spun it in my drill press and used some emery cloth to take it down until it fit.  Here is the bushing fit through the bearing and pressed up against the left elevator control horn.



The bushing has a center hole sized for a #40 drill bit.  Using a bit of Boelube, I drilled through the bushing to make a pilot hole in the elevator horn.



I stepped up the size of the hole using a couple of intermediate bits and finished with a 1/4" unibit.  After a bit of deburring, here is the finished hole.  I then repeated the process for the right elevator control horn.



After reinstalling the elevators, I slipped an AN4-14A both through to check the fit.  The holes are in perfect alignment.  Various washers will eventually be installed here to take up the intermediate space.



I finished trimming the horizontal stabilizer to allow for clearance of the elevator counterweights.  I'm allowing for 1/8" clearance on the front edge to the center of the counterweight (where the screws are).



The clearance between the side of the horizontal stabilizer and the inboard edge of the counterweight skin is also 1/8" and is perfectly even here on the left elevator.



The right elevator is off a little bit.  The clearance on the back end is 1/8", but the clearance on the front end is 5/32" (it was over 6"32", but a little leaning on the elevator while it was standing up on the counterweight brought it in slightly.  I might have been able to bring it in the rest of the way, but it would have required more force on the elevator than I was comfortable applying).  This is almost unnoticeable, so I'm happy with it.  With tonight's work behind me, I'm done with the elevators other than the fiberglass tips.



I got started on the elevator tip fairings by cutting the relief notch to allow them to clear the counterweights and trimming the flange so that the tip can fit in completely.



Here is the tip fully in place.  There's some unevenness between the weight and the tip, but I'll fill that with flox when I bond this in place.  This entire front edge will be glassed and filled.



Here's the horizontal stabilizer tip fairing rough cut and in place.  I opened the gap here up to 3/16 to give me some room to glass and fill in this area.



Here is the right side.  Clearly a lot of filling and sanding to do to get this looking good.



I cut a couple of pieces of last-a-foam for the elevator tips.



I epoxied the foam in place and put a couple of pieces of 1.45 oz/sq yd glass in place to bond them to the sides.  It's a lot warmer in the garage than when I did the vertical stabilizer tip, and the epoxy kicked off a lot faster.  I ended up having to mix a second batch to finish the other tip.  That's really all I can do tonight since I have to wait until this cures.



I mixed up some epoxy and microlight filler and filled the end of the elevator tips.  This stuff is incredibly light.  A five ounce container of the microlight additive fills a container about the size of a two liter bottle of soda.  It's great for filling and fairing.



My buddy Andre stopped by again tonight to get a little experience with fiberglass.  We riveted and glassed the horizontal stabilizer tip fairings on which took all of about 15 minutes.



Since we have to wait for the epoxy to cure, we got started on the rudder top fairing.  Here, I'm checking the fit.  All of the fairings have needed a fair amount of trimming and sanding to fit properly.  It's easy, but it sure makes a mess.



After riveting the top fairing on, we glassed both sides.



Here is the tip with peel ply in place.  That's all I can do tonight since this all has to cure.



Elevator Counterbalance

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I ran across a neat trick on vansairforce.net for adjusting the elevator counterbalance.  I installed a 1/4" nutplate through the forward tooling hole in the counterbalance ribs.



This lets you add or remove washers (probably large area washers) here to balance the elevators.  Ideally, you would want to have a few washers here to balance the elevator without paint, then remove them and adjust the amount of lead to balance the surfaces after paint.


I didn't get any pictures, but I also riveted on the elevator tips.

Wings Arrived!

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About 1:30 this afternoon, the FedEx freight guy showed up with my wing kit.



My buddy Dan dropped by to help me unpack the boxes since I didn't have room in the garage to store them.  This is the box containing all of the skins, ribs, tips, etc.



And this long box contains the spars and most of the hardware.



Cracking open the first crate.



After unpacking both crates, the benches and floor are covered in parts.  My buddy Andre dropped by later in the evening to give me a hand inventorying the kit.



Main wing ribs on the left and leading edge ribs on the right.  These things are seriously distorted (this is normal).  It will take a lot of fluting and tweaking before these are completely flat.



Inventorying the hardware.  The are a lot more components in the wing kit.  I had to hang up a second set of organizer drawers to hold all of the parts.



Spars laid out on the benches.  This things are truly works of art.  It's a shame that these will never be seen on the completed airplane.



Started Wing Kit

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My buddy Andre stopped by today and helped me get started on the wing kit.  The first thing you do is install a lot of platenuts.  These will be the platenuts that receive the fuel tank screws and inspection cover screws.  Here is Andre drilling one of the center holes for the platenuts.



Here you can see the countersinks for a couple of the platenuts.  The center hole is countersunk for a #8 screw and the outer holes are countersunk for AD3 rivets.



Here is one completed row of countersinks.  Instead of Van's recommended method of countersinking.  I used a long piece of 1/16" aluminum angle clecoed below the spar flange.  Way easier and more precise.



Here are both spars prepped for priming the exposed countersinks.



The battery in my digital scale died, so I broke out the NAPA 7220 self-etching primer.



After the primer dried, we installed all of the platenuts.  This went surprisingly fast with two of us and we had them all installed in about an hour.  Here you can see that the lower platenuts are countersunk for #8 screws and the upper platenuts are not countersunk for the #6 screws in the access plates.



I installed two more center section platenuts per spar.  Given that I was alone today, I shot and bucked these solo.  They turned out pretty good.



I also tapped the tie down brackets. Apparently, many builders have trouble with this, but mine turned out great and only took about 15 minutes.



Here are both tie down brackets with their threaded ends.



Finished Main Spars

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I got started making the tie down bracket spacers.  The crappy harbor freight hole saw and fly cutter I had sucked, so I went to Lowes and picked up a bi-metal 1" hole saw to make these holes.



Here is where the spacers will sit on the spar.



And here is how the tie down bracket will sit on top of them.



The spacers are back-drilled through the holes in the spar and then holes for nutplates are drilled.  Here are all of the parts primed and riveted together.



And here they are installed and torqued to the spar.



The backside of the spar showing the nuts holding these on.  The four hole in the middle bo through the spacers and line up with the nutplates.  These will be used for mounting the aileron bellcrank brackets.



Identified Wing Ribs

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I took the time tonight to identify and mark all wing ribs.  This was a surprisingly time consuming process because there are three types on main ribs (on the left) and four types of leading edge ribs (on the right), and all of these come in left-handed and right-handed variants.  Also, each wing has a mix of the left and right handed variants and they don't follow any simple pattern.  Basically, you have to study the plans and make sure you're using the right rib in the right spot.  I have all of these stamped now, and I've double checked them, so it will be easy when it comes time to attach these to the spar.



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