Step 5.0 Wings arrive

I've spent the last two months working on house projects in my spare time instead of the airplane. Hopefully, with my schedule clear, I'll be able to devote more time to the airplane going forward. So although I've been very busy, not much progress was made on this project.  To get an idea what I have been up against, here is a partial list of house projects completed:

1. Paint main room interior vaulted ceiling and one wall.
2. Repaint / recondition 20' of interior track lighting.
3. Build a 3' high, 40' long retaining wall with cinder block and then face with cultured stone.
4. Replace 6 sheets of siding on back side of house.
5. Replace 2 windows.
6. Replace 70' of barge rafters, facia board and 1x3 trim.
7. Repaint entire house exterior.
8. Take 6 loads of leaves and branches to the dump.
9. Install an evaporative cooler in shop.

Whew, I'm exhausted!  Thank goodness I can now get back to the airplane project -- it's so much easier.

The wing kit arrived via Fed-Ex freight in good condition, and although I had not yet completed the empenage tips my curiosity was piqued, but I was determined to complete the tips before opening the shipping crates.

Alas, one really can't overestimate the difficulty of ignoring couple of wood crates on the shop floor.  So after a couple of hours my curiosity was overwhelming, and out came the crow bar and hammer.

My first impression is that there is a lot of paper in there...

Slowly, we unwrap the parts and then Carol goes to work on the inventory over the next couple of days. Yep, all the parts are in there.

The next order of business is to construct the wing stands.  I am going to construct both wings at the same time (In theory, this allows one to save time) so I will need to build two stands.  The stands hold the main spars during assembly allowing access to either side for attaching the ribs and skins. I wanted the stands to be adjustable for leveling and be mobile.

Fortunately for me, I was able to enlist the help of my friend Chuck to work on the stands while I would  continue on with the empenage tips and my house projects. Below, Chuck cuts out the adjustable feet from some of the scrap plywood using a 2-1/2" hole saw. The feet adjust on carriage bolts through the plywood feet and tee-nuts in the base.

The stands have rubber feet attached to the bottom of the plywood feet and it gives structure a wonderfully solid feel with out any tendency to slip on the floor. But for mobility, I can set the stands on Harbor freight 3 wheel dollies at each corner. Chuck did almost all of the work on the stands and they came out beautifully.

In the next posting the actual work on the wings will commence with the attachment of nut plates to the main wing spars. Stay tuned!

Step 4.7, Empenage tips

With the elevators complete, the last step of the empenage is to fit the fiberglass tips to the horizontal and vertical stabilizers and to the rudder and elevators as well.  The first step is to fit the tips relative to each other such that they are even on the outside edge and in alignment along their chord line.  A notch is made to clear the lead balance weight.

 On the forward end of the elevator tip there was a gap between the lead balance and the inside of the fiberglass tip.  I used epoxy mixed with 3M micro-spheres as a filler.  The micro-spheres are teeny weeny glass balls that are hollow and take up a lot of space when mixed with epoxy.  This makes a very light weight filler material called 'micro' in the aircraft builder's community.  The micro is the white colored material in the photo below.  One shouldn't miss the opportunity to chuckle at the irony of light weight filler bonded to a lead weight.

I have decided to smooth the transition between the fiberglass tips and the aluminum of the stabilizer with a strip of fiberglass and a very thin coat of glazing putty.  Although I am familiar with auto-body repair and fiberglass techniques, I was offered a chance to learn from a master builder from my local Experimental Aircraft Association chapter.  I visited Keith Peterson's shop and was treated to fiberglass 101.  We fit and glassed on the rudder top tip in a few hours, and in the process, I was given the information essential to continuing on my own.  Thanks, Keith.

To facilitate bonding, the fiberglass gel coat on the tip is roughed up with #40 grit and the aluminum with #80.  I'm using West System's 105 epoxy and 206 hardener.  Two strips of 9oz fiberglass cloth are cut the length of the tip and a thin layer of epoxy is painted on to insure complete coverage beneath the glass strip.  Then the glass is laid down and the brush is used in a stippling fashion to remove all bubbles.  The glass is completely 'wetted', but just barely so.

Once the epoxy is cured the fiberglass is smoothed out and blended down to a feather edge.  I used #60 grit for this process before the final step of applying a light weight glazing compound to smooth the transition even further. 

It would be difficult to overstate the tedium of working with fiberglass were it not for the sheer bliss of not having to think too much.  Lots of sanding and filling, sanding and filling.  But it's not particularly difficult and  I was ready for a break from the interpreting of plans thing anyway.  I find that a lot of my time goes into just standing in front to the plans set and I'm definitely enjoying my vacation from that.

So at the time of this posting, I've completed the rudder tips and one elevator tip, with the vertical and horizontal stabilizer tips still to go.

The big news is that I have received my first technical inspection from EAA 1175 technical counselor, Miles Bostic.  I am pleased to report that there were no issues.

Oh, and one more thing, I have received my wing kit...

Step 4.6, Finishing the Elevators

The final steps on the elevators are rolling the forward skins and then hanging the completed elevators on the horizontal stabilizer.  To encourage the elevators to cooperate, the first step is to show them the implements that will be used against them.  Iron pipe, duct tape and pliers.  I understand that this alone is usually sufficient to scare the elevators into curling their own skins.

However in my case things must be done the hard way.  The pipe is placed inside the skin and taped securely to the edge of the skin one section at a time. The pipe is then rotated inward using the channel lock pliers while it is also being held down against the table.  The skin then just follows the pipe around its circumference and presto!  A curved skin.  Peel the tape off and go to the next section.

Making sure the top skin overlaps the bottom skin discourages water to enter.  Although I suppose that water would then elect to enter via the hinge cut outs between the sections all the same.

The bent skins are brought into as near as perfect alignment as possible with some judicious bending by hand.  It is preferred to not have any tension (in shear) on the rivets when they are installed.  So after a small amount of wrestling with it, the shape is very close and I proceed with clecos, match drilling, and finally, securing with pull-rivets.

With the closing of the forward edges of the skins, the last step is to hang them on the horizontal stabilizer.  First the rod end bearings are installed using the Sam Buchanan installation tool mentioned in a previous post.  From there the elevators are attached using two very small bolts through the hinge flanges on the stabilizer, continuing through the rod end bearing, then through the opposite hinge flange, and finally secured with a Nylock nut.

This is Carol looking for the hardware in bag 618.  Fortunately for us, she labeled all of our parts bins by rivet type and, for hardware, by bag number.  She also annotated the plans with the bag number where ever hardware is called out.  Thanks to Carol, finding parts is one area where little time is wasted.

While hanging the elevator one discovers there is a step on the horizontal stabilizer that has not been completed.  Notching the skin for clearance with the elevators's counter weight.  "Insert sound effect of record player arm scratching across a record"  Ok, mark and cut the HS and then continue.

In the photo below I'm working the right elevator with my hand on the control horn and checking for clearance with the horizontal stabilizer.  There were no issues.  Moving on.

So now the control horn must be drilled so that a bolt may pass through it and the horizontal stabilizers center bearing.  Remember that?  It was the first part we riveted.  Here it is again.

It's the doo-dad in the center.  The trouble is, you need a bushing in the bearing to protect the bearing surface while it guides a drill through and into the control horn for a perfect match drill.  So what can I use for a bushing?  Nothing.  I have nothing at all.  Unbelievable.  I guess, I need that record scratching sound effect again.  I will have to make another trip to the hardware store.

Yes, I'm back already.  I found a 1/4" standoff that worked out just right.  Now with the holes drilled we continue with the assembly.  Here are a couple of photos of Carol trying to fish the washers through a very tight space stuck to the end of a screwdriver.  One at a time, as we advance the bolt through.  Last one?  Great, we're done.  Oops, I got the wrong bolt out of bag 618, and it's too short.  Arrgh!  Start over.

Once the elevators are hung the last step is a balance check.  Since the elevators are not yet painted, we should have an over balance condition such that the elevators want to deflect upward (counter weights down).  My right elevator does this, but the left does not, probably due to the added weight in the trim tab and servo.  I will have to add some more lead to the left side before closing the elevator tip.

Step 4.5, Trim tab

Well, no more putting it off.  The time has finally arrived.  Time to build the dreaded trim tab.  Quite a lot has been written (on the internet) about the difficulties of constructing this diminutive, yet all important component.  First of all, the build manual instructs one to bend the skin to the final angle.  Then just bend the tabs over.  After all of the drama bending the elevator tabs, I was seriously considering cutting these off and building replacement ribs from the start.  But, I thought I would give the Van's method one more try and so I did.

I had the same difficulties with the bending block moving in, but the results were somewhat less catastrophic this time so I'm going to just live with it.  Since practice makes perfect, I figure that in ten or twenty more planes I could make the Van's tabs look pretty good.

The next step is to attach the tab actuator flange to the bottom of the trim tab skin.

Once that is done then the tab hinge and the tab spar are match drilled and then riveted.

The completed trim tab is then ready for installation on the left elevator.

Here is a view after riveting the tab hinge to the elevator.

Next, the trim tab servo is fitted.  It took a considerable effort to get the servo to fit through the access door and to prevent interference between the elevator actuator rod and elevator skin.  The build manual just barely mentions that it may be necessary to trim the actuator rod egress area.  Out comes the cut-off wheel...

Trim...

Trim...

Trim...

Trim...

And Trim!

What is really annoying is all of the test fitting between each cut-off wheel attack.  It was most of a night's work on this tiny weeny little part.  Finally, the result:

  

Since the build manual fails to give any guidance whatsoever on the proper way to adjust the trim tab servo linkage, I came up with this method:

1.  Using a 12 volt power supply, run the servo out to its furthest extent and measure the arm length.

2.  Run the arm back in to its minimum length.  Take half the difference and then add it to the minimum length to find the exact midpoint of the servo's extension.

3.  Run the arm out to the midpoint.

4.  Cut off the actuator's threaded rod at a length that allows it to be half way in the clevis fork with the trim tab in trail with the elevator.

This method insures the maximum travel possible with the supplied servo.  There is quite a lot of deflection available.

For me, the trim tab was not nearly as horrific at the elevator tabs.  Your mileage may vary, of course.  I did have a minor mishap while fitting the servo access plate though.  One of the #6-32 screws broke off in a nut plate.  Oh, $%@#!

I replaced the nut plate rather than risk damaging the backing plate.  In all, it was a ten minute detour on my way to finishing this airplane.  Not too bad considering I probably still have most of 2000 hours to go.

Step 4.4, Bending the tabs

It been a while since my last post and my progress has been fairly slow due to a misstep in bending the left elevator tabs.  The tabs in question were not photographed before they were originally bent so there won't be any before and after.  Shucks.  The tabs in question, close off the end of the trim tab cut-out on the elevator.

According to the build manual, one simply bends the lower tab up and the upper tab down over the lower and shazzam! An instant mini-rib.  Well this is, no doubt, the least expensive way to go. It is also a sure fire way to induct new members into the club of tab bending goofer uppers.  Fortunately, membership does have its privileges.  For example, I now know what not to do next time.

To join this fine, and apparently quite popular club, one begins by following the instructions to build a tapered bending block.  I used some plywood shown below.  The double sided tape is suggested to prevent the blocks from sliding during the bend process.

   

Then, the blocks are arranged inside and on top of the elevator skin such that the tabs can be bent over the edge of the block, 90 degrees.  In the picture below, the tabs have already been bent over so the lower block is only just visible inside the elevator.

To bend the tabs one is instructed to strike the tab with a hammer using a small block of wood to spread out the force across the length of the tab.  This is where things go south, because the force of the hammer blows cause the bending block to move inward an undetermined amount.  This causes the finished tab to be located too far in.  The undetermined part is especially troublesome as the bending of the opposite tab will most likely be a completely different undetermined value.  The bottom line is that in my case, because of this issue, the tabs were not perpendicular to the surface of the elevator skin.

At this point, I had no choice but to unbend the tabs and apply for membership in the aforementioned club.  Unfortunately, this horror story doesn't end here because unbending the tabs, I knew, would distort the skin.   And the tabs can not be rebent in the same place anyway without significant risk of stress fatigue in the aluminum and in the builder.

Still, the tabs had to go, so the new plan was to unbend it, but then cut those SOBs right off!  I have read online many accounts of intrepid builders doing just this; and so I did.

Good so far, but what about the distortion caused by the unbending?  No problem, I'll just hammer it out flat using the mushroom set on the rivet gun.  Genius!  So, the skin does get flattened, but now there is a little too much of it as the skin has been stretched out by the jackass with the pneumatic hammer.  

Now there is a definite bow to the skin along the edge and the corner is pretty ugly as well.  But, I'm not about to let this elevator die on the table, so I begin to think about what can be done to correct  the stretched out skin.

I was vaguely aware that it is possible to shrink metals using heat, some hammering, and a rapid quenching process.  After a quick consultation with the oracle that is the internet, I'm pointing a propane torch at my elevator.  

Since I had one hand on the torch and the other holding an infrared thermometer, there aren't any pictures of the shrinking process.  Suffice it to say that what is said about making sausage may also apply to airplanes.  Consider yourself lucky you didn't have to see it.   After the quenching process, the skin lays mostly flat and I'm thinking... I can't believe that actually worked!

The next step then, is to fabricate rib to close the elevator in place of the amputated tabs.

After final adjustment and then counter sinking, the new rib was ready for installation.

Finally, I'm installing the new rib which to my utter amazement, fits quite nicely.  I really thought my elevator skin was a gonner, but Roxy who looks on knowingly in the background, is always confident that things will work out in the end.