Sunday, April 3, 2016

Interior - flap actuator, seat belts and seat brackets

Finished off a few more interior items before I rivet  the rear and center fuselage together.

Installed the flap actuator. The Sling 4 instructions on the actuator show Sling 2 components, but nonetheless it was straightforward to figure out how to install it.  Although I had previously installed the flap actuator support bracket, I ended up drilling those out to facilitate working on the actuator.  I started by bolting the actuator to the brackets, and then riveting the brackets into place.  The kit is supplied with 3 thin and three normal washers - use the three normal washers on the forward bracket, and the three thin washers on the rear attachment.  A small 9 volt battery had enough juice in it for me to extent the actuator far enough to enable bolting it to the flap torque tube.

Forward portion of the flap actuator bolted  to the support brackets using a castle nut and cotter pin.
Flap actuator installed.  I ended up drilling out the brackets to 4.8 mm rivets.
I then started playing around with the front seat belts.  Installation of these requires that you fully unwind the belt from the spool so that you can thread the belt through the slots in the side channels.  The instructions have a few photos on this that are pretty clear.  The spool appears to be held in place using a single bolt that goes through the side of the fuselage.  It took me a while to figure it out, but I finally saw that the forward front seat belt attachment point gets riveted to the the landing gear support channel.  The final front seat belt attachment point is in the canopy, which I do not have yet.

Bolt for the front seat seatbelt spool

Front seat belt spool in location after threading the seat belt through the slots in the
side channels and rewinding the belt on the spool
Forward attachment point for the front seat base - this will be riveted to the fuselage
and landing gear support bracket
I then spent some time trying to identify where the rear seat stop and support bracket go.  After a number of tries, I finally identified a location that seemed to make sense - I will need to verify with TAF on this location (NOTE- verified this is the correct positioning), but the rivet holes do seem to (mostly) line up.

Proposed location for the rear seat stop and support bracket -  looking from the inside.
Location needs to be verified with TAF (NOTE: verified this is the correct position).
Proposed location for the rear seat stop and support bracket -  looking from the exterior. 
Location needs to be verified with TAF.

In preparation for riveting the side skins on, I also attached the interior skins to ensure they fit properly.  Once they were in place I was able to identify the location for the CF-CVR-003 cover plates - will need to install a couple more rivnuts for their attachment, but at least I know where they go now.  This leaves CF-CVR-002 as the only fuselage components that I have not identified the location of - have a question into TAF to figure out where they go.  I also riveted the support channels on the rear floor foot support so that it is ready to be riveted in its final location (which I will hold off doing for a while).

Right side forward interior skin.

Right side rear interior skin (with rear seat in position as well).
Location for CF-CVR-003 - a few rivnuts will be needed in the underlying ribs to allow
removal of the cover for inspections.
Support channels riveted to the rear seat footwell.

Sunday, March 27, 2016

Continuing work on the fuselage

Received a shipment of a few replacement parts so I finished off a few items that had been sitting partially complete for a while.  Next step was to rivet on the floor of the front fuselage.  It took a little while to sort out what holes in the side channels should and should not be riveted - once I figured out that one line of rivets was for the floor and one line of the rivets was for the interior side panel, it all made sense.  I also just about forgot the junction stiffeners, but managed to get them installed without issue. Also riveted on the lower firewall channels and the rudder pedals at this time - though I held off on installing the rudder cables for now.

Riveting the rear seat base
Riveted parachute box.  This is the updated box that is designed to sit about
 a foot forward of the initial location -  the move is to improve the
center of gravity when the rear seat was being  used.

Riveting the forward fuselage floor, rudder pedal base and lower firewall bracket

Rudder pedal bushings and clamps riveted in place
Not really clear, but the photo shows two lines of rivets in the floor of the front fuselage.
 The red line (with the installed rivets) is for attaching the floor to the floor channels.
The blue line, without any rivets, is for attaching the interior skin at a later stage.
After that, it was a deep dive into the fuselage center console and all the associated  forward and center fuselage covers.  Installation of many, many rivnuts was required for all the cover panels.  The rivnuts are used so that the covers can be removed during annual inspections, maintenance, etc. It became clear quite quickly that high quality hex keys will be very helpful.  I also riveted the slider on the front seat rail.  My sliders were a couple mm too long, so the ends were trimmed so they would lie flat on the aluminum angle.  The slider uses flush rivets to enable the seat to slide smoothly over its surface - it was easy to countersink the slider with a deburring tool. Since I had the seats complete, and since I was test-fitting the seat rails anyway, I figured I might as well go ahead and throw the seats on to see how it looked.  Was tempted to hop up on the bench into the seats and make airplane sounds!

Forward fuselage with center console and floor panels attached using buttonhole screws.

Rear seat foot well, with some panels  attached using buttonhole screws,
and some panels clecoed for future riveting.

Back panel of rear foot well riveted in place.  The floor panel will be riveted at a later time.
Components of the rear control cover riveted together.
These panels will be secured in place using buttonhole screws and rivnuts.

Support channels for the rear foot well still need to be riveted in place (on the underside of the floor).
Note that the location of these channels is not called out in the instructions, but it is a pretty obvious fit.

Front seat rails - remaining rivets will attach the rails in the final location.

Trying out the seat fit - pilot and co-pilot up front, and a bench seat in the rear for 2 more passengers.
The seats will eventually have leather upholstery (and perhaps an electric seat warmer as well).

The rear and front/center fuselage had been sitting a couple feet away form each other for some time so I decided to push them together and try out a test fit.  It became clear quite quickly that the longerons and rear seat ribs were not going to line up.  After scratching my head about it for a while, I emailed TAF and we determined that the orientation of the rear fuselage short longerons (RF-LGN-902) in the instructions (2014/02/19 revision) was incorrect and they needed to have their locations swapped.  So  the rivets holding the longerons were drilled out and the longerons were swapped and re-riveted.  This fixed the alignment issue and enabled the fuselage halves to be pushed together.  I also took the opportunity to add the forward skins and clecoed all the forward skin channels and the firewall to ensure everything else fit properly.

Oh-Oh!  No way these longerons are going to fit between the rear seat ribs. Turns out the
image in the instructions (2014/02/19 revision) is incorrect and the short longerons need
 to be drilled out and swapped.
Drilling out the rivets holding the short rear fuselage longerons, swapping their location,
and re-riveting them in place.

Rear and center fuselage easily match up when the longerons are in the correct position. 

Forward fuselage skins and side channels clecoed in place
Another view of the side channels and gussets.

Complete fuselage clecoed together 

Side reinforcing ribs - the wing will be installed in this location.
Firewall and top skin clecoed in location as well

Sunday, February 21, 2016

Autopilot servos, torque tubes, and undercarriage

Autopilot servos and control surface torque tubes were installed as described below. The area around the servos and torque tubes looks to be pretty tight, so I decided that I would install the servos now and hopefully prevent some scraped knuckles down the road.

I am planning for Garmin avionics, so the servos I installed are Garmin GSA-28's.  TAF has optional brackets specific for these servos.  The first snag I ran into was that the rear spar did not have pre-drilled holes for the elevator (pitch) servo bracket.  I mounted the servo on the brackets to get the proper alignment of those components, clecoed one bracket in its correct location to the seat rib, and then aligned the servo so that it was parallel to the seat ribs.  I then used a number of cleco clamps to lock the front bracket in position and removed the servo without disrupting the bracket location. With some careful drilling and clecoing I was able to match-drill all the bracket holes through the rear spar. Then it was easy to rejoin all the components and rivet in place.  The aileron (roll) servo attachment was much simpler - just a matter of getting the bracket holes to align with the servo mount holes.   One point I did notice while mounting the aileron servo was that the position of the aileron control stop is reversed in the Garmin install instructions compared to the visual depiction of the control stop in the fuselage instructions - not sure if other brand servos need the stop to be mounted differently, but do keep this in mind if you are using Garmin servos.

Garmin GSA-28 servos - just over 1% of the total plane cost in this photo!!!

Drilling holes in the rear spar for mounting the bracket of the autopilot pitch servo

Autopilot pitch servo riveted in place

Hidden on the top left is the mounted autopilot roll servo
This is the correct orientation of the aileron control stop bracket for the Garmin servo.
With the servos mounted I transitioned to the torque tube brackets.  The torque tubes are held in position by vesconite bushings and aluminum brackets.  For the front and rear elevator torque tubes and the flap torque tube, I found that there was quite a bit of friction on the tubes that prevented them from being relatively easily rotated.  Since we want the control surface connections to be free of any binding, I carefully trimmed the bracket edges to reduce the pinching of the torque tubes by the bushings.  By selectively excluding bushings one at a time, it was relatively easy to identify which bushing/brackets were binding.  I was careful to remove as little of the bracket as possible since if the bushing was too loose it would just rotate in the bracket, instead of the torque tube rotating in the bushing.  The front elevator torque tube in particular was a real pain to get in and out - it has a narrow gap to get past before being seated properly.  After a lot of  fine-tuning, I was finally satisfied that the torque tubes were rotating freely enough and riveted the brackets in position - a lot of hand-riveting. Note that I found that the bracket/bushings tightened up a bit with rivets compared to their movement with clecos - the rivets pulled the brackets together a little more tightly than did the clecos.

Riveting the elevator control stop tot he torque tube - this step was not described in the
instructions, but it is barely visible in one of the instruction images. Saw this correct positioning
 initially on Peter's site
Test fit of the torque tubes (and components of the center console). Flap tube is on top,
elevator tube on the bottom.

Another view of the clecoed flap and elevator torque tubes

Rear elevator torque tube just prior to riveting
Riveted rear elevator torque tube
About the only other thing I could do on the fuselage while I wait for the replacement parts was to cut out the soundproofing for the forward fuselage floor.  This won't get installed until final assembly, but they are ready to go when that happens.  Note that the soundproofing was not described in the Sling 4 instructions, but it is in the Sling 2 instructions, so I followed the Sling 2 instructions for this aspect.

Soundproofing cut out and ready to install.  It will get affixed to the bottom of the floor skin
that is riveted on top of these channels.
And then it was time for something completely different - the undercarriage.  I have never changed an airplane wheel before, so this was all new territory.  As airplane folks know, in contrast to automotive rims, the wheel rims for airplanes come in two halves that are bolted together on the tire. Dismantling the rims was straight-forward, though if I had taken a photo of the front rim before dis-assembly, the re-assembly would have gone a bit quicker.  I found the hardest part was to get the valve correctly positioned.  I ended up putting the tube around one rim half, with the valve in position, and then setting them both together into the tire (being very careful not to pinch the tube). I made sure to coat the inside of the tire and the outside of the tube with Johnson and Johnson baby powder aviation talc before assembly to help the tube slide and position itself properly in the tire during inflation.  I used hand clamps to squeeze the tire together so that the both halves of the rim could be placed in position and bolted.  The final hurdle for the front tire came with the nut and washer used to lock the valve stem in position.  I simply could not get any threads on the nut to engage the valve stem threads.  After doing a little on-line research, I found someone else that had this problem and they solved it by grinding down the washer.  So - off to the Scotchbrite wheel with the washer - I ended up carefully thinning it down to about half it's original thickness.  That freed up just enough thread on the valve stem to allow the nut to engage the threads - once started it was then easy to tighten it in place.

Front wheel rim is pretty simple.
Completed front wheel - note that the valve stem feeds through the rim to the other side.

The main undercarriage wheels were done in a similar manner, with the added complexity of the brakes. However, having figured out the steps on the front tire it was very straight-forward putting the main wheels together. 

Both main wheel rims before assembly

Using hand clamps to narrow the tire so that  the two rim halves can be bolted together

Wheels need to be mounted on something, so out came the components for the front tire strut and the main undercarriage.  The front tire strut goes together nicely just as shown in the instructions.  The threads for the bolts holding the top bushings on were pretty cruddy, so I ran some spare bolts through the threads a couple times to clean them up before final install.  As the photo below shows, I also have some rust on the strut that I will clean off and repaint before final install - it had been sealed in plastic shipping wrap and this seems to have trapped the moisture in and facilitated the rust formation. Should be easy to fix.  I struggled initially with trying to figure out how to mount the wheel on the main undercarriage. I just could not figure out how to mount the rim and brakes in the same orientation as shown in the paper Sling 4 undercarriage manual I received. After a while I remembered to check the dropbox to see if there were any updates to the instructions.  Sure enough, the orientation of the brakes in the paper manual is opposite that in the updated electronic Sling 4 manual.  Once correctly oriented, the wheel assembly slid on just like that (though admittedly, the cut-out in the undercarriage for one of the brake stems should have clued me into the proper orientation sooner).    

One main wheel mounted to undercarriage. Front is to the left.

Both main wheels on undercarriage and completed front wheel.
Nose wheel strut.  This will be dis-assembled, rust removed, and re-painted.

Although I will not mount the undercarriage for a while, I checked the fit of the 10 mm bolts that are used to bolt the undercarriage to the fuselage.  I have previously drilled these out, but did not have the bolts to check the fit.  Now, with bolts in hand, I found that my holes were just slightly too small for the bolts.  I  turned a 10 mm reamer  (from Amazon) using a hand wrench to take the holes to final size - all bolts fit now.

Using a hand wrench to turn a 10 mm reamer for the undercarriage bolt holes.
Fit of one bolt shown after hole was reamed