Bits & Pieces No 8

This blog covers a number of small items overlooked in previous blogs on the wings / flaps

Aileron's
Both ailerons were checked before closure and meet the minimum engagement but at this point, it was noted that access to the rod end mounted to the bell-crank would be difficult to access to replace the rod end bearing.

Note: The minimum thread engagement is 1.5 times the major thread diameter - Aurora Bearing Company. 

The factory advised that an additional access hatch would not be required but the words of Kel Gore [Great LAME, now gone] echoed in my head "Cut one now because if I have to, it might not be so pretty". With those wise words, a cover was installed onto the inside face of the skin, secured with 6 x M3 rivet nuts with another cover was fitted externally using M3 x 12 pan head S/S screws. 

If needed, all that needs to be done is drill a 90 mm hole at the centre of this assembly.

Note: The bellcrank has been redesigned and relocated on the new models, this is no longer an issue.

Flaps
The attach brackets were fitted using 4 Dia x 13 multi-grip rivets using the pre-drilled holes on the outside rib, all four [4] holes were reamed to clean them for riveting. 

Four [4] rivets were driven into their mounting holes using a small socket and then pulled using the small rivet gun.

Countersunk Riveting
All holes were dimpled using a simple hand tool, while not ideal it proved to be cost effective. 

To achieve the best possible finish when fitting countersunk rivets, it has to be pressed into the dimple using the rivet gun with the centre-line of the Pop Riveter as perpendicular to the surface as possible before pulling the rivet. 

Stringers
The top and bottom stringers were secured at both ends using a T shaped clip to place the stringers face flush with the top side of the rib. The clips place the stringer flush with the top side of the skin, in particular, were a rib and two skin meet creating a 0.05'' thick attachment point.

The mounting faces were coated with black polyurethane adhesive/sealant at assembly to help ensure a tight assembly when riveted. 

Checking fit before fitting

To prepare to fix the stringers a centerline for the stringers was marked along the outside of the skins, next the rivet centres were marked starting by marking 20 mm from the centre line of each rivet line. At each bay, the distance between each mark was measured, divided by 40 and corrected to a whole number, finally, the centres marked. In most cases on this aircraft, this worked out to be between 38 and 40 mm across all 5 bays.

This operation is required to be undertaken at the top and bottom.

Note: A cheap compass with a fine line felt pen was used to mark the centres.

Next, all holes were drilled and a centre line added along the full length of the stringer. With the stringer installed is was manoeuvred over one of the holes at each end by sighting the line through one of the drilled holes, a hole was drilled and clecoed, this operation was then repeated at the opposite end and finally at the centres the centre of the line.

Once happy with the locations of these 4 holes all holes were matched through the stringer then the skin/stringer was dimpled and finally the skin/stringer prepared for final installation

Note: This operation is criticial, there can be no errors

Fuel Lines

With all the fuel lines installed they were all tested with air pressure to check for leaks. While most of the key points have access hatches it would be better to rectify issues before the skins were fixed. The pressure regulator on the compressor was lowered to about 10 psi and all open ends were sealed with plugs and the springs removed from the return check valve allowing a full system check. Each joint was checked by spraying with detergent/water around each joint while checking for any bubbles, all joints passed.

Pressure testing lines

What's wrong in this picture?

After completing the 3.2 mm riveting on the starboard wing and then working on the port wing a large OMG was noted. 

The last two skins should have remained un-rivetted at the topside to allow installation of the fuel cap adaptor. This builder had started blindly building an aircraft not assembling an aircraft. This procedure is noted in the new kit notes and the builder was fully aware of this, in fact, it was all part of the mental plan. 

To fix the issue an area of skin was de-riveted and some careful aerobatics performed to install the adaptor and connect all the aluminium pipes for the static line. This created many hours of fun along with the prerequisite mess, blood and incantations. 

Note: BEWARE and think when you have a rivet gun is in your hand.

Comment
There will be more little bits to tidy up