Day 3--Left Wing Finishing, Motor mount, & surprises!

Hello Everyone!
By the Two Weeks to Taxi timeline, we are now 25% of the way to our first taxi and about two weeks from the first flight of our airplane!!  After today, we are actually a couple of hours behind, but nothing we can't make up.  Today was again filled with new experiences (trend item!) as we finished the left wing and mounted the engine to the fuselage.  In addition, while we were working some things magically 'appeared' on the airplane...we had to scurry to find the folks who put them in so we could see how things are done.  Here's the wrap-up!

First, here's the progress on the left and right wings:

This morning we put the right wing up in the rivet room next to the nearly-riveted left wing.  Immediately after this photo Ryan put the upper skin surfaces on the right wing and prepped them for riveting.

This is an example of my sometimes not-so-Zen-like qualities...didn't put full pressure on the rivet head prior to depressing the trigger.  The rivet bucked in the back but obviously isn't flush in the front.  This hole had to get the bad rivet drilled out and a new one put in.  For the record, Tracy's current pneumatic rivet score is 100%...no errors.  I married up.

Left wing right before it came off the jig--skin rivets complete!  I didn't count them.  There are a lot.

This picture clearly shows the different between flush rivets (top) and universal head rivets (the nubby ones below).  In this case the flush rivets are for aerodynamics over the leading edge of the wing.  The black circles are rivet holes that were filled with clecos until the final riveting.

Once off the jig, the next step is to put the "cove skins" on the wing.  The "cove" is at the trailing edge of the wing and it's where the flap fits (inboard) and the aileron fits (outboard).  If you look at the curve of the metal, it looks like it seats the leading edge of another wing--which it does, sort of.  Our flaps and ailerons are each shaped like small wings of their own.  When retracted they fit into the coves with minimal clearance, helping the airflow over the wing.

One of the interesting things about securing the Cove skins: they're actually glued to the top wing skins, not riveted.  The glue is Loctite epoxy, which is nasty stuff (hence the gloves and respirator) but should seal the trailing edge from moisture.  Check out all the clamps--only 1/4" gap between them to ensure a tight seal.  The epoxy takes about 3 hours to dry...so we will remove the clamps tomorrow.

I missed a picture of the fuel tank going in, but hope to get it on the Right wing.  In this picture the fuel tank is already in with the fuel lines run, and Tracy has almost finished riveting in the wing root rib.  The cylinder in the middle of the tank is the electronic fuel gauge--you can see the grounding wire coming out of it.  The fuel from this tank (the primary tank) comes out of the lower-most, silver-dollar shaped hole.  It's gravity feed so the airplane doesn't depend on electronic systems to get fuel to the motor.  Genius.

On the contrary, fuel from the outer wing tank (the auxiliary tank) has to get from the outboard of the wing through fuel lines to the main tank.  It does this with an electric fuel pump (above), which Ryan put in today along with the fuel lines.

Today was also Engine mounting day!  There's a lot of small but time-consuming work to be done on the engine during the mounting process:

First, the engine mount!  This is one of the first things Tracy did this morning.  Note the four big holes on the front end--these are the mounting points.  Unlike a car, you don't mount an airplane engine from all the way 'round--only the one side.  Therefore, the mounting points are reinforced and the engine/prop balance has to be perfect.  Those tight tolerances are one of the driving factors for aircraft engine price.

I caught Matt studying the manual for our motor--good on 'im.  With most of the work we're doing, the techs have the steps memorized, so they don't reference a checklist during a step--only at the end of the step, to make sure they didn't miss anything.  In this case, Matt is being more deliberate because of the various motor types to go on the Sportsman.  He is 'de-pickling' the engine and getting it ready for Sportsman-specific applications.

One of the Sportsman-specific applications is this gold-colored heat shroud that Tracy put over the main fuel pump this morning.  In some aircraft the airflow inside the engine cowling might be enough to keep the fuel pump cool--apparently not so in the Sportsman.

Check out the detail in the safety wire.  Today we learned that when safety wiring, you have to check: direction of twist, number of twists per inch (varies by application) and bend direction.  Note that if anything pulls on the safety wire, it will pull in a clockwise direction--tightening the bolt.  Ben demo'd this safety wire and it took him a good 10 minutes to put it in.

Mom, you asked how to get an engine on an airplane--here's your answer!  The engine weighs around 400 pounds.  No way we're going to lift it without hoist power.

Here's a picture of the engine (gold) on the mount (grey) with the massive shock-absorbing bushings (black) on both sides of the mount.  The bushings look almost the same but are not.  The right one is a "compression bushing" which is designed to dampen the compression forces as the motor pulls on the bolt head/washer.  The bushing between the mount and motor is a "tension bushing" which handles different vibrations as the motor tries to pull away from the mount.  On the bottom of the mount, the order of the bushings is reversed (because the order of the motor's push-pull effect is reversed).

This is my exact view to the lower-left engine bolt.  The working space in here is pretty tight.  It took Matt & me about 45 minutes to get all 4 cotter pins into the 4 bolts with the correct bend & cut length on the pins.  That's longer than it took to mount the engine. 

Finally, here are some of the random additions we either worked on or had to just keep up with today!

I caught Bryce putting a radio antenna into the tail.

Here's the radio antenna from the top of the tail, right before Bryce caps it.  Since our fuselage is carbon fiber, all of our antennas have to be external.  If they were internal or contacted the carbon fiber, the signals would get distorted since carbon fiber conducts electricity.  In this case, the exterior antenna (coat-hanger-lookin' thingie) goes through the rectangular cutout through non-conductive fiberglass glue to the antenna.  the antenna cable runs down the rudder and forward through the fuselage to the avionics panel.

Another thing Tracy worked on today is the control yoke.  Our aircraft has center sticks, not a traditional yoke--but the sticks are connected mechanically by this bar, which is still called a control yoke.  So if one stick moves--they both move.

Three pulleys: Left Flap, Right Flap, and aileron (remember the aileron crossover cable from yesterday?  That's why there's only one, i think.  I'll make sure tomorrow).  One thing is certain--these are right between and directly under the front seats (between the two control sticks).

The springs on the rudder cables (up by the firewall) are centering springs--to pull the rudder (or the tailwheel in taxi operations) back to neutral after a rudder push.

This is our future rear seating/cargo area.  The entire fuselage from the first bulkhead all the way to the tail will be empty to keep the plane within center-of-gravity tolerances.

Whew!  That's a lot.  Y'all gotta let me know when this gets boring. 
On another note--the Arlington fly-in and airshow is this Friday.  In this part of the country there are a lot of vintage and unique aircraft--we saw some of them flying in today.  We should get a small break on Friday and I'll try to post some photos of the happenings around the airfield here!

See you tomorrow! -zen