Undercarriage Adjustments

This blog covers those small jobs that ensure smooth operation and to allow greasing at the service points.

Overview
Final assembly of the undercarriage and linkages to allow greasing.

Installation
The first task was to disassemble the trailing link to allow the final adjustments to be undertaken.

Next operation ask was to reduce clearance in the linkage arms, this was achieved by super gluing two brass washers to the face of the cylinder link after dressing the both working faces to remove machining marks. The brass washers were then filed until they would insert into the mounting bracket firmly. Once correct, the arm was removed, labyrinth grooves added to allow grease to be distributed to working faces.

Hole marked A is used for cylinder attachment  was re-reamed 6 mm od and a suitable bolt installed with a nylock nut,

Note: Labyrinth grooves were added after it was found that grease would not pass between the faces when fully tightened.

The next issue discovered was that the grease nipples on the main pivots were hard to access and it was decided to rotate both pivots 30 degrees, this required removing all AN3 bolts plus the brass retainers. 

While removed, labyrinths were added to the retainers allowing grease to pass between the mating faces.

With all the preparation complete the links were reassembled for a final time. 

Each bolt was carefully adjusted to provide a zero clearance but not more with the goal to place the faces in contact under light pressure.

Three different locking methods were used, at the main pivot, an aluminium locking tab was employed at the knuckle, a castellated nut was installed. The later was selected because there is a possibility of relative movement between the two items and this is generally accepted as the reason to use mechanical locking method such as a split pin.

At the rod end secured to the leg, the pivot bolt was drilled to allow lockwire to be fitted after final adjustments are completed. The factory has released an instruction to over this task and should be followed.

Note: A Titanium bolt was used providing a plain shank for the rod end to operate on, this was covered in a previous blog. 

Comment
The gear manufacturer supplies nylon washers to pack the wing pivot that provides a bearing surface but at assembly, it was found that a number of additional washers were required. All pivots are fitted with dry lube bushes, secured with commercial bolts that create clearances between the shaft and the pivots. Hence there is a need to ensure both bearing faces are in full contact without over tightening bolts. 

Dry running is the proven option, but the clearances must be minimal after assembly.

The work outlined in this blog is a conclusion of fitting greaseable points.

Yes, old school but remember, it fitting not assembly.

Navigation Lights

This blog covers the installation of the navigation lights and strobes.

Overview
The use of a camouflage paint scheme created some need to be seen in the real world, so the addition of lights was required, even for VFR operation. Also, after considering mounting methods, it was decided to glue the lens to the tip to avoid the risk of cracking. 

Installation
With the fibreglass wingtips covered in a previous blog, the final task was to install and connect the lights.

Opening for lens cut using Dremel cutting disc
Edge is approximately 12 mm wide

Aluminium 2024-T3 0.020"" covers used to match the profile 
of tip Short cover [no tab] slips through the tip while the other 
rests on the edge allowing glueing

Fixing cover -  Small dabs of Parfix urethane adhesive sealant
were applied to the edge to tack the sheet. The cover is held in
position with tape until cured. After curing a bead was applied around the perimeter on the inside edge.

Covers painted with gloss black. A pair of M3 rivet nuts were 
fitted to the removable cover to allow the screws to be removed from 
the inside of the tip 

The next task was to fit a LED Navigation / Strobe LED pack onto the fixed cover. It was decided to tap the brass inserts for mounting M4. To do this, the hole was enlarged to 3.4 mm to minimise drag while providing enough holding force.

The model selected was Aveo Powerburst Daylight Set in Red & Green.

These were connected to the wing loom using a four [4] pin Molex plug.

Note: Selecting lights again the builder would look for a model that allows rear fixing

The factory lens is a vacuum formed profile combining both lenses for both wings. An initial cut is provided, and this completed to separate the cover into two separate pieces. One is then placed onto the tip, and the first cutting edge marked using a Sharpie pen. This was cut using a set of sharp decal scissors, checked and sanded using 120 wet n dry to the marks. 

Marking initial cutting edge with Sharpie

Cutting edge - A denotes location relative to faring

Trimmed and sanded using 80 grit garnet paper
Edge marked allowing cutting edge to be located

Establishing a final sanding edge

The recess of the tip was filed to provide a constant depth and edge all around the tip. 

After a final check, a 5 mm bead of Parfix Acrylic Urethane Sealant/Adhesive was applied on the centre of the tip recess then smoothed to an even coating. The transparent cover was expanded at the far edge and inserted over the tip and aligned then several pieces of 40 mm masking tape were applied to hold it in position to cure.

Lens glued to faring
Covered with tape to allow the edge to be worked into the adhesive

Note: Here, the builder was a little too accurate, and part of the lens cover was found to lie on the curved edge of the tip requiring a quick trim with the scissors. Doing it again, the builder would ensure that the lens laid on only the flat area of the tip and then fill the recess with a sealant after fixing the lens in position.

With the masking tape removed the edge was prepared for the painting to cover the adhesive attachment with the cover masked to fully cover the attachment point plus 2-3 mm over. 

The paint used was Krylon Fusion Plastic paint, black spray can. This was applied in three [3] light coats and once dry all the tape and paper was removed.

Note: The painted area is confined to the area of attachment to avoid overheating the cover and to ensure as much support as possible on a hot day 

The backing sheet has an M3 rivet nut and screw installed to provide a handle to assist in the removal for cleaning.

Finished

The finished assembly was cleaned and polished with Mr Sheen Spray polish that gave a clean sparkle to the construction, smells nice too.

Comment
The biggest issue was the original decision to mount the light from the front, and this required the tapping the brass inserts M4 as the only possible access for mounting is from the rear.

Doing it again the plate for the attachment of the light would be 0.025'' 2024-T3 with a 0.020'' for the backing plate. The thicker sheet would be just stiffer to mount the backing plate; also, it would be folded in the opposite direction as this would provide improved access for cleaning and servicing.

Postscript
Tapped the factory bushes using an M4 tapered tap, installation used M4 x 12mm button head screws.

Painting Preparation

This blog covers the painting preparation and RAF camouflage scheme.

Overview
The RAF 2010 Battle of Britain colour scheme sent this builder down the road to create the Shorts T1 and a desire to give the Australian Tucano a linkage with the Australian pilot Walter Cale's story.

In the time from the original decision and a lot has run under this bridge, the scheme has been refined but was guided by the Battle of Brittian pattern.

The final decision was the selection for ID lettering, and belly colour between Duck Egg Green, Sky Blue and Grey with the Duck Egg Green to be the most likely applied to aircraft of the 266 Squadron in the Battle of Britain.

Another decision had to be made on the paint method, it was decided early that the aircraft was to be finished in a Satin, so base over clear was selected. 

This process requires a 1K primer, colour and finished using a 2K satin clear with a weight advantage as 1K is thinned 1:1 compared with 2K paint at 2:1

Next task was to obtain samples of the three colours required, Dark Green, Earth and Duck Egg Green. This was made possible with the popularity of plastic models for this era, a Vallejo Battle of Brittian paint pack will allow the base colours to be tinted with reasonable accuracy.

Hardware
The first issue to be solved was a spray booth and having spent enough time getting to this point I was not in the mood to build a spray booth. Three [3] 3 x 3-meter and one [1] 6 x 3- meter canopies were purchased and require being unpacking then folding out. Once in position over the aircraft, a plastic sheet will be fixed to the sides using a lot of 3M cloth tape.

How to apply the paint - big issue for a non-painter, the only way is a spray gun, but the decision was what was to provide the puff. A meeting with Larry Black at Frazier Lake in California, a long time ago revealed a very tidy Falco with a great finish. Larry used a turbine sprayer and as a skilled shooter was impressed by the lack of overspray and economy of application - 4 litres of paint to be exact and this meant saving weight, a lot of it.

Back in now, I decided that this is the way to go. The turbine sprayer has come a long way since Larry used one on the Falco, so which one. Well after a lot of web time I settled on an Apollo 5 stage Premier model - not cheap, but if in doubt get the biggest and best in the range, they charge more for a reason.

These units produce dry, warm air that should be free of water and other contaminants. The main gain is the lack of over overspray as the extraction is primitive, not a match for a spray booth. It is generally stated that a turbine should put better than 85% of the paint on the job when set up correctly.

Note: Once finished it is hoped to sell it for 60% of what it cost. 

Preparation
The first job which was done earlier involved filling around the rivets using applications of etching primer. Blade putty and a lot of careful and gentle sanding. Foam sanding block was used to create the control needed with a combination of 320/400 wet and dry. 

Sanding stopped when any rivet head or aluminium appeared, then a new sanding angle used until the whole area was smooth. The countersunk pop rivets are not as flush as I would have hoped with the primary reason the lack of ability to create a crisp dimple with a hand tool plus the operator's skill.

What was gained - not a lot but it does remove is that product of "Proletariat Tractor Factory No 3" look that an all riveted wing seems to have - its a choice with a lot of work attached to it.

Note: Primer in spray packs is the same type that will be sprayed

Wings filled and etch primed ready for the 
application of the sprayed primer

At this time the end ribs were primed using the SLS Etch spray as was the underside and mating faces of the inspection covers. Once dry, the overspray was removed using methylated spirits and paint thinners.

Note: Methylated Spirits proved to be a very effective remover of the Wattyl SLS Etch primer, and if you can have it with orange juice it cannot be all that harmful, can it?

All the covers were reinstalled using sacrificial screws to be disposed of after painting. 

Comment
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