7th August 2008 - Setting up the HS incidence and control linkage

Having completed the framework of the right HS it was an opportunity to mount the HS and elevator on the fuselage. The HS is a tight push-fit on the HS spar carry through and then bolts to the fuselage at the front to set the incidence of the whole tailplane. The fuselage was set up on the bench with the datum exactly horizontal. Then the HS was set to 0 degrees using the level set across a 3/8" spacer on the leading edge to provide a datum with the main spar. A bolt hole was then match drilled from the leading edge tab into the fuselage mounting. This was repeated at incidences of 1, 2, and 3 degrees using the digital level. The first test flight will probably be done with 1 degree of positive incidence and then this can be adjusted to get level cruise with the elevator exactly in-train to minimise drag.

Next the elevator pushrod was connected to the control system through to the control column. Although the mechanism worked correctly there was inadequate movement of the elevator - the plans call for 30 degrees up and 25 down. After spending some time pondering this and looking at the options it seemed that moving the control column pivot point forward was the answer. Re-reading the plans made it clear that I didn't have enough horizontal distance between the control pivot point and where the elevator pushrod enters the aileron torque tube. Luckily this wasn't a difficult fix. The pivot hole was re-drilled an inch forward and the original hole plugged with a short piece of 5/16" rod welded into place. The new hole was lined with a piece of 3/8" * 0.028" tube as before. The trim lever rod also had to be lengthened by an inch so a new section was welded in place around a length of 7/16" tube to provide additional strength. Finally the system was re-assembled and I now have 31 degrees up and 25 degrees down - perfect. In addition with the original rework I had done on the system the movement is perfectly smooth, frictionless and without any discernable play - that will do!

6th August 2008 - Right Horizontal stabiliser

After the little distraction on the ailerons and flaps it's into the right HS. First the outline was laid out on the building board. The 1-1/4" main spar sets the datum for the height of the tubing so I needed 1/4" under the rear spar, 5/16" under the top cross piece and 3/8" under the front edge. As before drills were used as the shims to set the heights. The various pieces of tubing were then cut to length and notched as required. They were then half welded into position before the stabiliser was turned over and the rest of the welding completed and the second bottom cross member added. Next the leading edge and the two spars need cutting to length, the remainder of the cross members adding together with the tab that will be bolted to the fuselage to set the HS incidence.

5th August 2008 - Odds and Ends

The tubing arrived that I needed to install the supporting diagonal on the undercarriage mount so first job was to cut and weld this into position - my joints may not be the prettiest but I guarantee that this is not going to come out!
Next job was going to be to make a start on the right horizontal stabiliser but that uses the same tubing as the front spars for the flaps and ailerons (1-1/4" * 0.035"). These require longer pieces so I decided to cut these first to make sure I didn't end up with tubing in the wrong lengths. Having cut them I then set about making the Delrin bearings that support the aileron torque tubes in the flap spars. Four of these were made from 30mm round Delrin bar stock. I used a 3/4" holesaw in the drill press to cut the hole through the bearings and then reamed them out for a loose fit on the torque tube as called for in the plans. The outer 30mm diameter needed just a light sanding with the belt sander to get a tight fit into the spar tubing. For each flap spar there is one Delrin bearing in the middle and one at the outer end. You can just see the installed bearing in the flap spar second from the top in the picture. It is secured with a 4-40 set screw tapped though the spar and into the bearing. The inner end of the flap spar has a metal bearing so I've ordered some 30mm bronze bearings. As these are metal I can heat the spar tube to insert these and get a shrink fit. The inner diameter of these is 15mm so they will need drilling and reaming to fit the 3/4" torque tube. Not surprisingly you can't buy bearings with a 1.18" OD (1.25 - 0.035 - 0.035) and 3/4" ID.

The 1-1/4" diameter aileron spar has to be connected to the 3/4" aileron torque tube so washers with the same 1.18" outer diameter and 3/4" inner diameter are required to centre the 3/4" torque tube in the spar for welding. These were fabricated by cutting out circles of metal plate using a 35mm holesaw which happens to give a disc of metal, normally, discarded ,pretty close to 1.18" in diameter. A 3/4" holesaw was then used on the same centre to create the final shape of the washer. The plans call for just one washer at the joint but I'm going to use two spaced about 3" apart to make sure the aileron spar and torque tube are nicely co-axial.

3rd August 2008 - Right Horizontal Stabiliser

Completed the bit I forgot on the right elevator by welding in place the positioning pieces that locate the hinges. Then cut and welded 3/4" lengths of 5/16*0.058 tubing onto what will be the right horizontal stabiliser (HS) rear spar. The hinges screw through these using AN3 bolts. This will allow me to get perfect continuity between the HS and the elevator as I build the framework of the HS on the building board.

2nd August 2008 - Undercarriage preparations

It will be helpful to get the fuselage onto the undercarriage to make it easier to get into and out of the workshop so taday was spent preparing the undercarriage. First the second of the undercarriage sockets was reamed out to 1-3/8". Then the brake mounts were positioned and match drilled to the undercarriage legs. These legs are tough!! Even with cobalt drills it took some time to drill each 5/16" hole and used up two new drills. Finally the wheels were assembled with their tires. I'm using 500-5 tires on exactly the same wheels and brakes as Vans use for their RV range. I'll buy from Vans the spat mounts, spats and leg fairings.

1st August 2008 - ...and reaming

The undercarriage legs for the Tailwind made by Harmon Lang are sized to fit into a 1-3/8" socket (1.375"). 1-1/2" * 0.058" tubing has an inside bore of 1.384" so there is about 1/100th of an inch of slop. 1-1/2" * 0.065" tubing has an inside bore of 1.37" and the legs won't fit. I decided to use the 0.065" wall tubing and ream it out to fit. I managed to find a 1-3/8" hand-reamer second-hand for £5 so all it needed was to pass it through the tubing to get a perfect fit - easier said then done!!!

First issue was how to hold the tubing tight enough without squashing it. I solved this by cutting it overlength and then welding one end to a piece of box section tubing that could be held in the vice. This allowed me to ream down from the top. a large spanner was used to grip the reamer and then it was more oil, turn, back-off, and repeat ad nauseum. At the end of an hour the reamer had disappeared into the tubing, my back was in spasm, and it was time to cut the tubing off the box section and weld it to the other end so I could finish the length from the other end. This time it only took 30 minutes before the cutting started to get easier and I was into the section reamed from the other end. Finally, dripping in sweat I had the first undercarriage mount socket. Only one more to go but that's a job for another day.

1st August 2008 - Tapping ...

Received the 3/8" * 0.065" tubing I needed to make the tailwheel linkage. I'm using 5/16" Heim joints bolted to the wheel and rudder so I needed to tap the tubing to take the screw threads on the joints. As always with tapping its lots of oil half a turn in then quarter back and repeat until done. The result works well with the ability to adjust the length of the rod to get the wheel and rudder directly in-line. Lock nuts are used on the screw threads to avoid any chance of the linkage coming undone