Working On Flap Controls

Spent some time working on components that make up the flap controls. The flap handle is a hollow tubular shaft that internally receives a thumb knob, a spring and fork assembly.  These parts allow the flap handle to be raised or lowered then locked in three preset positions. The fork assembly has a pin through it which locks into groves cut into the F-1266A flap detent bracket. The fork assembly has three spacers sandwiched between the two forks this is typically done with pop rivets … but AN470AD4 solid rivets were used in the place of the pop rivets.

Using a rivet gage to determine the correct rivet length that will hold together the fork assembly.

After the flap handle fork assembly was riveted together, it was clamped onto the F-1260A flap handle tube, carefully aligned, then the F-1260A tube was match drilled to the rivet holes in the fork assembly. The assembly was disassembled, deburred, then riveted with LP4-3 pop rivets.

Riveting the flap handle fork onto the F-1260A flap handle tube with LP4-3 pop rivets.

Completed flap handle fork assembly with the locking pin installed.

The next flap control component to be riveted was the F-1266A flap detent bracket. The flap detent bracket becomes sandwiched between two F-1266C flap detent angles then attached onto the F-1266B detent bracket plate.

Riveting the two F-1266C flap detent angles onto the F-1266A flap detent bracket.

One of the two F-1266C angles only has holes on one flange … the other flange becomes match drilled to the F-1266B flap detent bracket plate after the angles are riveted to the F-1266A flap detent bracket.

Flap detent assembly secured onto the F-1266B flap detent bracket plate with Clecos. Note how the nearest F-1266C flap detent angle has no rivet holes … there are holes in the F-1266B bracket plate below which will be used to match drill the angle.

Using the rivet holes in the F-1266B bracket plate to match drill the one F-1266C flap detent angle that had no rivet holes.

After match drilling the F-1266C flap detent angle the assembly disassembled and deburred. Next the six rivet holes in the F-1266B bracket plate are machine countersunk on the bottom side of the plate for AN426AD4-6 flush rivets.

Machine countersinking the six rivet holes in the F-1266B bracket plate with a #30 100 degree countersink bit.

Riveting the flap detent assembly onto the F-1266B bracket plate with AN426AD4-6 flush solid rivets.

Completed flap detent bracket assembly.

Plumbing The Matco Parking Brake Completed

In spite of a limited work session Saturday, was able to finish measuring and cutting the poly brake line tubing along with installing the compression fittings for the brake lines that attach to the aft end of the Matco parking brake. The Adel clamp for holding the brake lines to the right tunnel rib was loosely screwed in position so fairly accurate measurements could be made for cutting the poly brake line tubing.  Once cut marks were made, the brake lines were pulled forward so there would be enough slack to cut the lines and install the components for the compression fittings onto the brake lines. Once again, placing a very thin film of CorrosionX on the tubing made assembling the fittings much easier following the procedure described in an earlier post.

Pressing the brass insert into one of the poly brake lines. Masking tape was used around the tubing to keep the nut and sleeve out of the way.

Sweeping the brake lines underneath the fuel line worked out quite well. The brake lines clear both the bottom skin and the fuel line nicely, plus the Adel clamp will secure their positioning and keep the brake lines out of the way of the rudder cable when it is installed.

Finished attachment of the brake lines to the aft end of the Matco parking brake.

None of the brake lines are tightened yet because the rudder/brake pedal assembly is just temporarily sitting on the tunnel ribs … it will now be removed until such time as the tail cone is attached and a few more wires are pulled in for the buttons on the not yet discussed Tosten stick grips that were purchased at Oshkosh. That said, one can see from the photo below how the overall fit is of the entire assembly.

Rudder/brake pedal assembly temporarily sitting on the tunnel ribs and connected to the Matco parking brake.

 

It is unfortunate Aircraft Specialty came out with the vinyl coated braided Teflon brake line kit for the RV-12 after the bottom skin was riveted in place on the DOG Aviation RV-12. It would have been nice to have had the entire brake system made from braided Teflon brake line. That said, the Aircraft Specialty RV-12 brake line kit configured for the Matco parking brake is a quality offering and should last for many years. I’m very pleased with the quality of Aircraft Specialty’s custom hoses and their great customer service.

A Hodge-Podge Of Work Activity

Worked continued on the brake line in the center channel – the excess was pulled forward leaving what appeared to be the approximate amount of brake line in the center channel. Unfortunately, obtaining a precise measurement will require a human wire tie to hold the brake line up against the center channel’s aft bulkhead while the brake line is positioned and adjusted for proper fit to the inboard landing gear attach brackets.

Pulling the excess brake line forward … will need help to finish the job of measuring in the center channel.

On the recommendation of a Rotax mechanic on the forums, the DOG Aviation purchasing department procured a Handi-Cut made by Sears. This tool has a razor sharp cutting blade that will easily cut through all sorts of tubing - fuel line hose, water line hose, oil line hose and fire sleeve while making perfectly smooth square cuts every time. Have to say, it works great.

The Sears Handi-Cut becomes the official tubing cutter at Dog Aviation.

Using the Sears Handi-Cut to cut the poly brake line.

Mike said he was stopping by the hangar later in the afternoon, so while waiting for the extra help to correctly position the brakes line in the center channel, decided to work on other items to keep progress moving forward.  The longer AN525-10R20 screws ordered for mounting the Matco parking brake came in … so they were installed on the Matco parking brake. At first glance they look too long but are the right size. This is because Matco wants a rubber washer installed between the bolt or screw and the body of the Matco parking brake so the unit can flex a little … the additional length of the screw will be taken up by a thin washer and Nyloc nut - this should leave a couple of threads showing which will be perfect. Did not permanently mount the parking brake at this time because it appears it may be easier to use wrenches to tighten the brake line compression fittings if the parking brake is not tight up against the tunnel rib.

AN525-10R20 screws ordered from Aircraft Spruce for mounting the Matco parking brake.

While waiting for Mike, went to work on installing the VA-146 bearings onto the F-1263A&B flaperon mixer bellcranks.  This is another one of the places where it was easy to squeeze solid rivets with the pneumatic squeezer so AN470AD4-5 solid rivets were installed in place of LP4-3 pop rivets. Gee, it has been a long time since the pneumatic squeezer had been used … it still works.

Securing the VA-146 bearing onto the F-1263A flaperon mixer bellcrank with Clecos in preparation for riveting.

Using the pneumatic squeezer to rivet the VA-146 bearing onto the F-1263A flaperon mixer bellcrank using AN470AD4-5 solid rivets in the place of LP4-3 pop rivets.

Both completed F-1263A&B flaperon mixer bellcranks with the VA-146 bearings riveted in place with AN470AD4-5 solid rivets in place of LP-4-3 pop rivets.

Looking for more to do while waiting for Mike decided to turn my attention to the task of trimming the F-1262 flap handle blocks. The plans call for trimming 3/4" off both bottom corners of the blocks. Because these blocks were black, decided it best to use masking tape to mark the cut line.

One F-1262 flap handle block with two cut lines marked with blue tape … one down one to go.

Running one of the F-1262 flap handle blocks through the band saw cutting 3/4" off the bottom corner of the block.

Cuts completed on both of the F-1262 flap handle blocks.

When Mike arrived he was promptly put to work as a human wire tie holding the brake lines in the center channel up against the aft bulkhead while I adjusted the slack of the brake lines to obtain a good fit to the inboard landing gear attach brackets. Once the brake lines were in position, their position in the center tunnel was marked at a pair of grommets … this was done so the brake lines can be pulled forward to facilitate installation of the compression fitting components then pulled back to their correct position.

Van’s drawings has the builder sweep the brake lines over the top of the fuel line … because of the location of the Matco parking brake and wanting plenty of clearance for the rudder cable, this routing did not work well. Instead, the brake lines were routed under the fuel line which resulted in a nice sweep over to the right tunnel rib where an Adel clamp will be used to hold the position of the brake lines. Marking the location of the Adel clamp was another step that required two people. While I was holding the Adel clamp with the brake lines inside it Mike made sure the clamp was positioned at a good angle to provide a good transition to the Matco parking brake. Once a good placement was obtained for the Adel clamp, the tunnel rib was marked and drilled.  Thanks for the extra hands Mike.

Drilling the tunnel rib for the mounting screw for the Adel clamp that will secure the brake lines to the right tunnel rib.

Brake Line Install Begins - Parking Brake Aft

Because of the instillation of the Matco parking brake, the measurements  shown in the plans no longer applies for the length of brake line tubing required to run between the parking brake and the inboard landing gear attach brackets that the brake lines connect to. This required locating the powder coated U-1203 inboard landing gear attach brackets and temporarily setting them in place so a true measurement can be made. Prior to mounting the gear attach brackets for the brake line measurements, two brake line fittings were installed in each mounting bracket using Loctite 567 thread sealer. The F179CA-4-2 fittings are 45 degree elbow fittings and require being clocked to a 45 degree angle when installed into the U-1203 inboard landing gear attach brackets.

Installing the 45 degree elbow fitting into the inboard landing gear attach brackets.

Both U-1203 inboard landing gear attach brackets with the F179CA-4-2 elbows installed and clocked to 45 degrees per the plans.

After the inboard landing gear attach brackets were readied, the poly brake tubing that will run through the center tunnel from the Matco brake into the center channel was fished through the center channel. An excessive amount of brake line was pulled through the center channel so the brake line could be pulled out the side of the fuselage to make installing the pesky fittings easier.

Installing the compression fittings on the poly tubing is not a piece of cake and ultimately took up a good amount of time to get it ironed out. Unfortunately (well not for Pete), Pete’s RV-9A did not use the poly tubing supplied by Van’s for the brake lines … his RV-9A has all custom built brake lines. As such, I did not have any first hand experience installing the pesky brass inserts into the poly tubing. Van’s suggests soaking the poly tubing in boiling water then installing the brass insert onto the tubing. This method may or may not work, but I have heard folks on the forums complaining that it is still not that easy. However, not having boiling water at the hangar required coming up with another method. To that end, experiments were made on heating the tubing gently using a heat gun on the low setting, but I was not overly impressed or completely happy with the results … so decided to investigate other options. Lacking boiling water, the best overall solution appeared to be spraying a little CorrosionX on my finger and working a drop inside the tubing to coat the inside and waiting until it migrated about 1/2" inside the tubing. A small film of CorrosionX was also placed on the brass insert that is placed inside the tubing … the brass insert prevents the tubing from deforming as the compression fitting is tightened. Those familiar with CorrosionX know it creates a very thin slick film that migrates … a little drop goes a long way.

The brass inserts that are pushed into the poly tubing which prevent the tubing from deforming as the compression fitting is tightened.

After a little CorrosionX was placed in the tubing and on the brass inserts a steel back riveting plate was used to press the brass sleeve into the tubing. Still not a piece of cake but overall this worked well.

Pressing the brass insert into the poly brake line tubing by pushing down on the metal plate.

The brass insert fully seated into the poly brake line tubing.

To facilitate sliding the nut and sleeve for the compression fitting over the area of the brake line tubing with the brass insert, a thin film of CorrosionX was placed on the outside of the tubing then a small open ended wrench and mallet was used to tap the nut and sleeve down over the brass insert until the compression sleeve is 1/8" from the end of the tubing per the plans. Overall this went well and did require very much tapping to slide the nut and compression sleeve into position. Don't forget to inspect the inside of the fitting to insure none of the poly was scraped off to possibly interfere with the proper seating of the fitting.

Gently tapping the compression fitting nut and sleeve down over the area of the tubing with the brass insert by using an open end wrench and a small mallet.

Finished compression fitting for the inboard landing gear attach bracket end of the brake line ... note the sleeve is 1/8" from the end of the tubing per the plans.

Some may wonder about possibly contaminating the brake fluid with the CorrosionX. For starters just a very small amount was used (only enough to put a thin film on the desired areas) and the decision has been made long ago to use synthetic transmission fluid as the DOG Aviation RV-12’s brake fluid … either Moble 1 or more likely Amsoil because it has a higher flash point of 453 degrees … which is a good thing. I truly don’t think any slight CorrosionX residue left behind will affect a synthetic ATF by the time the lines are flushed of possible debris and air during the brake bleeding process. Plus, in a pinch on a Sunday night, it will be far easier to locating a synthetic transmission fluid than it is to locate aircraft brake fluid.

Final Parking Brake Position Determined

After running errands and working on non aviation related items at the hangar, there was enough time left in the day to finalize the position of the Matco parking brake and drill the mounting holes in the F-1217A-R right tunnel rib. The Matco parking brake assembly was mounted 1/2" below the flange on the tunnel rib this allows just enough clearance for the screws that secure the tunnel cover onto the tunnel ribs. Mounting the unit high will also offer plenty of clearance away from the rudder cable assembly.

Matco parking brake assembly mounted and temporally bolted in position so the brake lines continuing on down the center tunnel can be correctly measured and cut.

Have decided to mount the assembly with an AN525-10R20 screw which will need to be ordered. A 10R18 could be used if the builder decides to not use a Nyloc nut. (I’m pretty sure the 10R20 will be long enough if not, will make a correction to this post). With the permanent position of the parking brake finalized, the brake lines from the parking brake going aft through the center tunnel to the center channel landing gear mounts can now be cut and installed.

Locating A Home For The Matco Parking Brake

Due to outside forces the last work session was abbreviated …. plenty of time was spent at the hangar, but little meaningful actual work on the RV-12.  One of the things accomplished was temporally placing the rudder/brake assembly in its general position so a permanent home for the Matco parking brake could be determined. The Matco parking brake is not part of the Van’s kit … but a nicety being added to the DOG Aviation RV-12. For the trial fit, the white blocks that hold the rudder/brake assembly together were held together with wire ties.

Rudder pedal/brake assembly temporally setting in place so measurements for the Matco parking brake can be made.

Looks like the Matco parking brake will end up on the right center tunnel rib in this general area.

Decided not to drill any holes for the parking brake mounting so will take up this task during the next work session.

Firewall Forward Parts Repainted

Wednesday, prior to the plunge in temperatures, decided it would be a good idea to revisit the firewall forward parts that were painted earlier in the summer with VHT white gloss ceramic engine paint.  Frequent readers of the Blog may recall I was less than satisfied at the results. Decided to sand down the imperfections with 320 grit wet or dry sandpaper and have another go at it.

Parts in the bin ready for recoating with paint after sanding and cleaning with solvent.

The red paint I sprayed on the spar pins the other day was also VHT paint and the spray nozzle from that can seemed to spray somewhat better than the spray cans I used previously … so the nozzle was removed from the red can and was used to re-spray the parts. I still contend the spray nozzles supplied with the VHT paint are far less than stellar, but this time a better finish was obtainable. Overall the finish is still not as nice as I was hoping for, but far better than it was, so I won’t powder coat the parts. Because of the falling temperatures, a second light was added to the bottom of the paint drying box to generate more heat. This will likely be the end of spray painting for the year.

Firewall forward parts re-sprayed with VHT gloss white ceramic paint and placed in the drying box.