Saturday, April 30, 2016

A DAY OF SETBACKS – All Self Imposed

Ever have one of those days where you should have stayed home? Yesterday was one such day … a one step forward, two steps back kind of day …. more on that later. The work session began with filing the eyelets on the hinges that are on the curved portions of the fuselage skins. This is done so the piano hinge that will be attached to the cowling halves can be mated to the fuselage. Because of the curve, the outer edges of the eyelets on the hinge are closer to together … so the eyelets along the curve need to be filed a little to create a small angle that makes them somewhat trapezoid shaped.
Filing the edges of the eyelets that are on the curved portion of the fuselage. The edges are filed at an angle to form a trapezoid shape.

After the edges of the eyelets were filed per Van’s instructions, went to test fit the longer F-1201J hinge and here is where the wheels fell off and instantly ran into issues. Bernie had come by to visit and with his help, I was pushing the hinge pin in while he was trying to make the hinge conform to the curve, but the hinge pin kept binding up. We fought and fought with it for a very long time … removing the hinge and doing a little filing then refitting, etc. … the hinge just did not want to cooperate and conform to the curve. After fighting with it for quite some time the dim light went on and dawned on me, all along I had been trying to install the hinge upside down … DUH!!!  When the hinge was reshaped and flipped upside down, it fell right into place.
The F-1201J hinge installed “proper side up”.

The second setback for the day - it was discovered that all the rivet hole marks that were meticulously placed on the hinges were on the wrong side. I missed a note on the upper corner of the drawing stating:

NOTE: Mark hole locations on the hinges so that when installed the
markings will be to the outside as shown in Figure 3”.

Although I missed reading the above note prior to marking the hinges, I blame some of the error on a very poor drawing in the assembly manual. Here is one case where a picture is worth a thousand words …. all profane. Below is a photo of the plans which illustrates how easy it is to mark the wrong side of the hinges if one misses the above note as I did. If the solid line that defines the loop for the hinge as shown in figure 2 were not there altogether or at least a dashed line, the builder would know the drawing is depicting the backside of the hinge. But no, they made it look like the front of the hinge not the backside.
The upper hinge material was marked as shown on the Figure 2 drawing … the lower hinge is positioned for the side that actually should be marked so the marks can be seen through the fiberglass when it comes time to drill (as pointed to by my finger). It is easy to see how a builder would mark the wrong side if the note mentioned above is missed and the builder uses the figure 2 drawing as sole reference as I did.

Being upset with myself for foolishly missing that note … not to mention frustrated with having the F-1201J hinge upside down for so long before catching the error, I was not in a good mood by this time. Decided it was best to pack it up for the day and head home early and get over it.

Friday, April 29, 2016

A Hinge & Pin Fest

Since it was another rainy day outside yesterday, decided to focus attention on the mounting hardware for the RV-12’s cowling as opposed to getting fiberglass dust all over everything inside the hangar.

The plans call for cutting two sections of hinge material 22" long to create the F-12115 side hinges. These will become the left and right cowl side hinges that will secure the upper and lower cowling halves together. Had a minor issue to sort out … in that the plans are not real clear how to cut the F-12115-R hinge. Only the left hinge is shown and by just cutting two pieces of the hinge material as shown on the drawing and flipping it upside down for the right side it will make the hinges differ because the forward most eyelet will be on the bottom cowl but on the right side it will be on the upper cowl. Not that it makes a difference … but it will just not look symmetrical when the top cowl is off. To remedy the situation, the 22" measurement for the right hinge began 1/2" in from where it shows on the drawing.
My fingers are pointing to the left and right F-12115 hinge halves that will attach to the lower cowling. Note that by offsetting the beginning of the cut by 1/2" now the forward most portion of the hinges that will attach to the bottom cowl on both sides will begin with an eyelet.
By cutting the right hinge material with the 1/2" offset, the right side will be symmetrical to the left side as shown clearly in this drawing.

The hinge pins that come with the hinge material the F-12115 hinges are fabricated from are not used … instead, Van’s supplies two very long hinge pins that has a tabs welded onto them that need to be cut to size. The tabs have holes that will be used as a point to secure the hinge pins to the cowling by using a screw placed through a hole in the tab. The cowl hinge pins are to be cut to 26" so the Dremel (which has been getting a work out the last few work sessions) was outfitted with the cutting wheel to cut the cowl pins.
Using the Dremel outfitted with a cutting wheel to cut the right cowl hinge pin to 26". The tab welded onto the left cowl hinge pin can be seen in the background.
Left and right cowl hinge pins cut to 26" and ready for action.

Next on the agenda was fabricating the pins for the F-1201J & K upper cowl hinges which need to be 27 1/2" and 14 1/2" respectfully. The hinge pins require having a 90 degree bend to form a handle of sorts that is 1 3/16". I found using the seaming tool (which has rounded bills) did a great job of bending the pins by rolling it over on a piece of wood. After the 90 is made on the ends of the pins, the pins are to be shaped to follow the curve of the fuselage.
Using the seeming tool to bend one of the upper cowling hinge pins.
After bending the pins, and shaping the ends per the plans, they both slid through the eyelets without much difficulty.

The remainder of the hinge pins were made using the dimensions in the drawings and the associated hinge pieces were cut to size per the drawings with no issues. Once all the various hinge pieces were cut, rivet hole locations are to be marked on the hinge sections, BUT NOT drilled.
Finished pile of hinges and pins. The four F-12115 side hinge pieces on the right still need to have the rivet hole locations marked.

Ran out of time so will finish up marking the rivet hole locations for the side hinge pieces during the next work session.

Wednesday, April 27, 2016

Lower Cowling Receives More Cutting

After doing a little fine tuning of the joggle on the lower cowling, as per the plans the lower and upper cowling halves were mated and clamped so two #40 holes could be drilled. This was accomplished by using a piece of wood for the lower cowling to sit on so the long tabs would stay flat to the floor and aligning the side edges of the two cowling halves so they could be held together with duct tape. After the two halves are clamped together, measurements are laid out for 6 screw holes … three on the front surface of the cowlings on either side of the hole for the propeller flange. HOWEVER, only the two inboard screw holes on either side of the center prop flange hole are drilled to #40 and Clecoed at this time … the remaining four holes will be drilled much later.
After securing the two cowling halves together with duct tape and clamps, as cab be seen in the photo, measurements are to be made for three screw holes on either side of the center prop flange hole.
For now, only the two screw holes closest to the prop flange hole are to be drilled. The first hole has been drilled and Clecoed and the second hole is being drilled to #40.

Moving on, the next step is to cut out the slot for the nose wheel gear leg. The Dremel was outfitted with a cutting wheel and used to make the rough cuts followed by hand sanding down to the scribe lines.

After the rough cuts were made for the slot but prior to separating the two cowling halves, Bernie and Mike were available to help me do a test fitting while both cowling halves were still held together with Clecos and duct tape. As expected, the cowling touched the spinner back plate because the cowling halves are still 1/8" too long since the aft edges have not yet been sanded to the scribe lines. If taken to the scribe lines all the way around, the cowling appears it may be skewed slightly left of center … by having a little extra material to work with, the hope is to improve on that a little when the lower cowling half is fitted. At this point the two halves were separated and the lower cowling half was carried back outside to finish sand the rough edges of the slot.
Sanding down the edges of the slot for the nose wheel gear leg.
Almost there … the slot needs just a little more tweaking to get down to the scribe line.

The lower cowl will get fitted first after six pieces of hinge material are fabricated to length. Eventually the hinge material will be riveted onto the inside edges of the fiberglass cowling halves … the end result is typical the Van’s Aircraft fleet in that the cowling halves will be secured to each other and the firewall with hinges sporting removable pins.

Tuesday, April 26, 2016

More Trimming & Cutting Of The Lower Cowling

The weather was nice enough yesterday to allow for more trimming & cutting of the RV-12’s lower cowling outside. Some material needed to be removed from the inside edge of the large oval opening in the lower cowling. I had a very difficult time finding the trim line … it was very faint and could only be seen if the cowling was studied very closely while being moved around at various angles to get the light and shadows just right so it would appear. There were a few places the trim line just could not be made out at all, but fortunately enough of the line was marked that it was easy to fill in the gaps.
Marking the cut line on the inside edge of the oval opening on the lower cowling with a mechanical pencil.

Once again, the Dremel tool outfitted with a cutting wheel was used to trim off the excess material from around the oval opening on the lower cowling. At this time, the oval opening for the exhaust pipe was also cutout. After making the cuts, the edges were sanded down to the trim line. I ended up wrapping sand paper around a small bottle to sand down the areas where the cutout for the exhaust pipe is rounded then switched to a PVC pipe about the same size as the curve ... worked quite well.
80 Grit sandpaper wrapped around a small bottle did a great job of getting down to the trim lines in the areas where the exhaust cutout is rounded.
Lower cowling after sanding the areas where material was removed. My finger is pointing to the area where another cut needs to be made … but only after the lower cowl is mated with the upper cowling and a couple of holes drilled.

As can be seen in the above photo, my finger is pointing to a long slot that still needs to be cut. Prior to doing so, the instructions have the builder mating the upper cowling with the lower cowling so a couple of holes can be drilled where screws will eventually go. Cutting the slot out now will likely make the lower cowling much more flexi …. So will hold off on doing that until after the holes have been drilled … hopefully later today.

Monday, April 25, 2016

Calibrating The Auto-Trim Settings For The AP Panel Module

Frequent readers of the DOG Aviation blog may recall my elation when the anti-servo trim tab moved in the correct direction when the panel mounted trim switch was activated. This was after  discovering there was an error in Van’s instructions regarding the trim motor wiring when installing the AP Panel module … so the wiring of the trim motor was done based on what I “felt” was correct … and is.

Having the optional Dynon AP Panel module installed in the DOG Aviation RV-12 necessitates that the autopilot be configured using Van’s “expert mode” configuration files for the autopilot. This is because the AP Panel module requires the SkyView’s autopilot’s settings be set to expert mode to function correctly. This also makes it necessary to perform a calibration of the autopilot’s Auto-Trim function. Why is it necessary to go through the trim calibration process if the anti-servo trim tab moves in the correct direction when the panel mounted trim switch is activated?


The reason for the above statement is because there are two trim control circuits at work here. The panel mounted switch is one circuit available to manually trim the aircraft using the panel mounted trim switch. PLUS, there is an additional trim control circuit built into the AP Panel module that can “Auto-Trim” the aircraft during flight when the autopilot is engaged … (I believe this is based on feedback from the autopilot’s pitch servo motor). The Auto-Trim calibration process makes sure the Auto-Trim circuit built into the AP Panel module will move the anti-servo trim tab in the correct direction when the AP Panel module calls for an Auto- Trim correction when the autopilot is engaged.

Calibrating the Auto-Trim is a piece of cake and begins with positioning the anti-servo trim tab approximately in the center of its range of motion prior to entering the Auto-Trim calibration menu in the SkyView. As usual, the Set Up menu is entered by depressing buttons 7 & 8 simultaneously. Using the left joystick, cycle down the list to highlight Hardware Calibration.
The calibration for the autopilot’s auto-trim feature can be accessed from the Hardware Calibration menu highlighted in this photo after joggling the left joystick to the right.

As can be seen in the photo below, one of the options in the Hardware Calibration menu is Trim Motor Configuration. Highlighting the Trim Motor Configuration by moving the left joystick down then joggling the joystick to the right will enter the Trim Motor configuration menu.
The trim motor calibration menu has two choices Motor 1 and Motor 2 … the RV-12 only uses Motor 1.

Selecting Motor 1 will open the options menu for motor 1. The Auto-Trim function is the first item in the list. Note in the photo below that Auto-Trim Function is set to None ... this is because the calibration test has not yet been performed.
With Motor 1's Auto-Trim  Function highlighted, joggling the left joy stick to the right will enter the calibration test menu. The test will begin then the “Start” button is pressed.

With the Auto-Trim Function highlighted for Motor 1, as in the photo above, joggling the left joy stick to the right will open the calibration test menu. The testing will begin when the start button is pushed. When the test begins, the AP Panel module will activate the trim motor and move the anti-servo trim tab. The user is to select which “trim” was called for by the AP Panel module based on the direction the aft edge of the anti-servo trim tab moved. In my case, the anti-servo trim tab was moved DOWNWARD … this is “Nose Up” trim. (Remember the trim tab moves opposite of the desired trim, so nose down trim moves the trim tab UP and nose up trim moves the trim tab DOWN). Anyway, the user interface asks which trim was called for and in my case I selected “PITCH NOSE UP” and pressed the OK button.
The test began by the AP Panel module moving the anti-servo trim tab DOWNWARD. This equates to calling for PITCH NOSE UP trim so that entry was highlighted before pressing the OK button to continue the calibration process.

After pressing OK, the AP Panel module moved the anti-servo trim tab in the opposite direction moving the anti-servo trim tab UP this time. On the screen, the user interface asks which trim was called for and in my case I selected “PITCH NOSE DOWN” because the anti-servo tab was moving UP. After highlighting PITCH NOSE DOWN and pressing OK the calibration process is completed … the Auto-Trim feature is now calibrated.
The calibration continued by the AP Panel module moving the anti-servo trim tab UPWARD. This equates to calling for PITCH NOSE DOWN trim so that entry was highlighted before pressing the OK button.

Taking note of the text on the left side of the screen in the above two photos, one can see there are additional trim control settings that can be manipulated. As an example, should the pilot feel that the trim is a little too sensitive at speeds above 100 knots, using the trim speed settings in this menu, the actuation speed of the trim motor can be slowed down if the aircraft is flying faster than the predetermined speed entered in the menu. If the aircraft is moving faster than the predetermined speed, the trim motor will run slower thus the anti-servo trim tab movement will be slowed down thus making the trim “feel” less sensitive above 100 knots. Elected to leave these settings alone for the time being until I get a better feel for the trim ... which can only come after flying the RV-12 for a while. However, it is nice to know the option is there to customize the trim settings should one desire to do so.