26th August 2008 - The build so far

It's unlikely that I'm going to be able to get much done over the next 2-3 weeks so today I decided to assemble everything built so far and check that all the controls are able to move through their full range without any interference. First job was to work out the movement required in the control stick and aileron bellcranks to achieve the required aileron movement - 36 degrees up and 28 degrees down (64 degrees total). The aileron horn was installed on a pivot on the bench and rotated through 70 degrees and the distance between the end points of the horn at the two extremes measured. This, allowing for some contingency, established the movement required in the outer end of the aileron bellcrank that connects to the aileron pushrod. Aileron stops were then welded to the two diagonals that support the bellcranks - one just visible at the top of the first picture. 3/8" tubing was used for these which can then be sleeved to fine tune the movement down once the wings and ailerons are in place. With the elevator control also connected, the movement of the control column could then be checked for any interference with the floor. This revealed a slight touch at full right, full aft position and the cut-out in the floor was then enlarged slightly to solve this. Next the flap mechanism was checked. This revealed a much more significant interference between the left seat bottom and the flap torque tube pushrod. This required a cut-out in the left seat bottom and the removal of the centre-most tab to provide clearance. This was a valuable discovery to make before I boxed in the flap control inappropriately!
The second picture show all the controls installed and the flooring and seat bottoms screwed into place. Given my efforts over the last few days, I was pleased that the rudder and brake mechanism fit perfectly and once a carpet and control column boot are in place the floor should look neat and tidy. Obviously now all the controls were working as required it was time to open the door get in and have a picture taken (thanks Daryl). One interesting question coming from sitting in the aircraft is which hand to fly with and where to locate the engine controls? - I think a question to the tailwind forum to get views is in order.

25th August 2008 - Front floor section complete

Finished drilling the front floor section, the supporting tabs, and installing the clinchnuts. Also fabricated the box to cover the hole for the rudder torque tube carry through. This was made from 0.032" 2024-T3 aluminium sheet left over from the Vans. The sides and the bottom of the box were riveted together using AN470-4-4 rivets and then the box was match drilled to the floor which was countersunk for AN426-3-4 rivets. It was good to get the riveting tools out again and after the 10,000+ rivets in the RV9 it was not surprising that I still remembered how to use them!

24th August 2008 - Cockpit Floor

Spent more time working on the two sections of the cockpit floor. The front section was match drilled to the tabs but still needs the clinchnuts fitting to the tabs and the holes in the floor drilling out for the M4 screws. The bigger task on this section was to measure out and cut the holes for the brake master cylinders and the rudder torque tube carry through. This took two goes and a wasted piece of aluminium but they are now correctly positioned and the rudder and brakes work without any interference. There is still a box to be constructed to fill the hole where the rudder torque tube carry through goes to avoid everything in the cockpit disappearing into the sub floor.

The rear section of the floor is now complete with holes drilled for the rudder cables and glands installed. Also a collar has been made which will carry the control column boot. This can be seen screwed to the floor round the control column torque tube .

21st August 2008 - Tabs 41 - 119

Today I located and welded into place the tabs to support the cockpit floor panels - 79 in total. I established a datum at the bottom of the main fuselage longerons using a piece of 4" * 2" timber and then used a spacer of 11/16" to locate the tabs flush with the tops of the longerons. Then it was a case of welding each one in turn. The vertical tabs under the front of the seat cross member posed more of a problem but a little jig was created to hold them while they were welded. Finally all the tabs were drilled 1/8" ready to fit the flooring. The rear section of the floor was then match drilled to the tabs at the corners and clecoed in place whilst the rest of the holes were drilled. Then the floor was removed and the holes opened up for the M4 screws and the holes in the tabs opened up to 6mm for installation of the clinchnuts which, as before, were tack welded to remove all possibility of spinning.

20th August 2008 - Cockpit floor

Made a start on the cockpit floor today. First a piece of 6061-T6 0.050" aluminium sheet was cut to shape and then clamped to the underside of the fuselage. This allowed all the cut-outs needed to clear the tubing to be marked. The sheet was then removed and cut to shape. At this point it became clear that it was going to be impossible to insert the sheet into the fuselage in a single piece so it was cut along the line of the main fuselage cross-member. The two edges of the sheet touching the cross member were folded up 30 degrees about 3/8" from the edge to allow the sheet to rest on the lower longerons which are only 3/4" diameter whereas the cross member is 1" diameter. The rear section was folded up 90 degrees to fit against the cross member that forms the front edge of the seat and was cut out in the centre to clear the control column torque tube. Next there are about 80 tabs to weld onto the tubing, drill, and fit with clinchnuts to support the two sections of the floor and cut outs are needed for the brake master cylinders and the rudder torque tube carry through.

18th August 2008 - Left Door Latch

Spent a significant chunk of time going through the plans, identifying all the tubing needed to finish the various components of the airframe and comparing it with what I have left. This resulted in yet another order to ACS, but not too big this time - managed to keep it below the $100 cut off for USPS shipping.

Then fabricated the latch for the left door. Two pieces of 3/8" * 0.058" tubing are welded to the door frame to create the pivot for the handle and the guide for the latch pin. The handle itself is fabricated from 1/4" * 0.035" tubing with a loop on the outside and a simple handle on the inside - why? who knows? but it's what the plans say. I haven't bent the tubing to form the internal handle yet so I can remove the mechanism from the pivot to clad the outside of the door with aluminium as required. A lever was fabricated from 0.071" 4130 plate and this was connected to the latch pin with some 1/16" wire. Some 3/8" channel is used to hide the mechanism from the inside and create the end stops for the travel of the mechanism. Finally a tab was welded to the frame to hook the return spring onto which keeps the latch pin closed unless the handle is turned. All very simple and works well but takes a few minutes to get everything aligned.

17th August 2008 - Seat Bottoms

The bending brake went into action for the first time today. I'm using 0.050" 6160-T6 aluminium sheet for the seat bottoms. This was cut to shape using the bandsaw and then the rear edge folded up to give additional strength. The front edge was folded up slightly to fit tightly against the fuselage cross member. A cut out was made to allow the rudder cable to pass through. 1/8" holes were drilled in the tabs and then match drilled into the seat bottoms. The holes in the tabs were then opened up to 6mm and clinchnuts installed with M4 threads. Clinchnuts have a bad reputation as they can sometimes loosen and spin in the mounting holes making it impossible to remove the screws but they are easy to install and provide a cheap solution for creating a blind nut. I solved the problem of them ever spinning by tack welding the flange of each clinchnut to the tab. The holes in the seat base were then drilled out for the M4 stainless steel machine screws and the seat bases installed.


The left door frame hinges were then fabricated from 0.090" 4130 steel. The door was positioned in the door frame using clamps and spacers. The frame hinges were then clamped to the hinges already welded to the door and tack welded to the door frame. The pivot hole was then match drilled through from the holes in the door hinge to frame hinge. Finally the door was removed and the door frame hinges final welded

15th August 2008 - Rest day

No building today but instead flew from Andresfield (EGSL) to Calais (LFAC) for lunch in the RV9A. Here pictured approaching the white cliffs of Dover at FL45.

14th August 2008 - Left door

Started by welding the undercarriage sockets into their reinforcing collars - quite neat by my standards!
Then a final ream of the sockets to clear any weld penetration and the undercarriage mount is complete.

Then decided to make a start on one of the doors. I'm putting off building the second of paired items so the aircraft has currently one horizontal stabiliser, one elevator, and now one door.

The door was constructed in situ using clamps and 1/4" spacers to position the tubing away from the door frame. This will allow the door to open freely and give space for some sort of seal to be attached to the edge of the aluminium door skin which will overlap the fuselage. As each piece of tubing was cut it was welded to the previous piece with as much of the weld as possible completed so that no change in dimension or shape would take place when final welding Once the complete door framework was completed it was removed for completing the welding and adding the hinge pieces to the front tube. Next step will be to add the hinges to the front of the door frame. The positioning of these will be critical to getting the door to shut whilst exactly overlapping the aluminium cladding of the front section of the fuselage.

13th August 2008 - On Wheels!

The second of my large hand reamers arrived in the post today. These things retail on Amazon for 112USD but I managed to pick up a new one for 10USD. This one is 1-1/2" and is needed to ream out the undercarriage socket reinforcing tubes to take the 1-1/2" OD sockets. This only took 2 hours of grunt work this time as the central sections of the reinforcing tubes were removed once the ends were reamed to size. So with the undercarriage sockets in place next step was to align the undercarriage legs.
A 1/4" pilot hole was drilled through the reinforcing tubing and the front of each socket where the 5/16" undercarriage retaining bolt would eventually go. These were aligned horizontally with the spirit level. A line was then drawn mid way up the top bearing surface of the leg so that this could be centred in the pilot hole. The fuselage was then placed on its right side and levelled fore and aft. The left undercarriage leg was then inserted and twisted to get the axle 1 degree from vertical using the digital level - this gives the required amount of wash-in for the wheel. the leg was then

clamped in position and match drilled from the pilot hole through the leg and out the back of the socket- easier said than done as the leg is spring steel and very hard - cobalt drills are essential and it takes more than one! I chose to do this by drilling 1/4" by hand first time and then opening the hole up to 5/16" - most of this latter step through the leg itself could be done using the drill press. Then the fuselage was turned over and the process repeated for the right leg. Finally, the bolts were inserted, the wheels put on the axles and the fuselage became a rolling chassis for the first time. This was definitely the time to get in and make aeroplane noises!
There is still a bit of welding to do to fasten the undercarriage sockets into the reinforcing tubes but that's a job for another day.

12th August 2008 - Tabs 1 - 40

I decided to do something different today so started on preparing the fuselage to take the interior. First up the were the tabs that will support the seat bottoms. The bit that needed thought was where to position the panels relative to the various sizes of tubing. I decided to set them in behind the main cross bar so they sit directly on the side and centre diagonals. This mean't I would need plenty of support on the back of the cross bar and on the cross member at the base of the fuselage behind the seats. These got 18 tabs each at 2 inch centres. Four additional tabs were then located in the middle of each of the side and centre diagonals so 40 in all. The welding is quick and easy but it takes a couple of minutes each to jig the tab into position. I'm waiting on some sheets of 0.050" 6061-T6 aluminium which I will use to for the seat bottoms and backs and then I've got an interesting idea for a housing for the flap lever but will reveal that when its been tried out.

11th August 2008 - Fin rework

Regular readers may remember that I was unhappy at the way that the thin steel channel that forms the middle two ribs of the fin had straightened between the braze points.
http://tailwindbuild.blogspot.com/2008/07/24th-july-2008-fin-complete.html
Discussing this on the Yahoo Tailwind forum led to the conclusion that I had under bent the ribs leaving them in tension so when they were heated whilst brazing they bent at the heated points and returned to straight between them. This will be something to watch when I do the horizontal stabilisers and wing tips.

To improve the profile of the fin, I decided to add a thin layer of resin and micro-balloons which could be sanded to a smooth curve. First the channels were roughened with the sand-paper to provide a key for the resin. Then two pieces of scrap aluminium with the protective plastic still on to act as a non-stick membrane were used as "shuttering" held on with spring clamps and a stiff mix of resin and micro-balloons added where required.

Once dry the filler was sanded to profile to produce the smooth curve required.

Whilst I had the filler out, the joints between the rear of the ribs and the trailing edge were also filled to remove the lip caused by the thickness of the folded trailing edge and the joint between the trailing edge and the tail-light fitting faired in. Should get a nice smooth covering now.

10th August 2008 - A "serious" bending brake

Coming up are a number of tasks that need sheet aluminium bent accurately - the fuel tank, the cockpit floor, the door panels. In order to do this I needed a bending brake and as the starting price for a 36" brake seems to be around £450 it seemed prudent to make one. A bending brake has three parts: the apron, the clamp, and the table.
The sheet of metal is placed on the table, and the clamp is tightened to hold the sheet in place. The apron is then lifted to bend the metal. The starting point was the plans available on the Miller welding machines website http://www.millerwelds.com/interests/projects/bending-brake/
But I needed something longer and stronger so the materials were significantly scaled up. The apron and the table are made from 40" lengths of mild steel angle iron 120mm x 75mm x 10mm. The clamp is made from a length of mild steel angle iron 80mm x 80mm x 10mm. The hinges were cut out from 1/2" thick steel plate and the hinge pins were cut from a length of 3/4" steel rod, 3/4" *0.058" tubing provides the sockets for the handles which are 5/8" steel rod - it's heavy!! The difficult bit was cutting and shaping the hinges from the 1/2" steel plate. The bandsaw was used to do the cutting but the feed rate had to be incredibly slow. The holes were drilled using a 18.5mm drill which was also slow and generated untold amounts of messy swarf mixed with cutting oil. They were then reamed out to 3/4" - a tight fit in the outer part of the hinge and a turning fit in the inner.
The outer part of the hinges which attach to the table were final welded together as per the Miller approach. The hinge pins were pushed into place using the vice and assembled with the inner part of the hinge which attaches to the apron. A section of the edge of the table around the hinge pivot was ground down slightly (about 1/50") to provide clearance and the apron itself reduced in length by about 1/100" to allow the two halves of the hinges to turn without binding. Then the table and apron were then clamped together in alignment and the hinges positioned and tack welded. Then it was a case of final welding the hinges into position. This is the first time I've had to turn the welding machine up but 150amps worked well getting good penetration into the thick metal.

I decided to use the angle iron for the clamp sitting on it's open edges so the bottom of the two sides were ground flat to provide a good contact area with the material to be bent. The edges of the clamp were then shaped to provide two different bending radius. Sections of box steel sawn in half were then welded to the top and into the ends to provide horizontal clamping positions. Finally, some scrap angle iron was welded to the bottom of the table to space it off the bench and provide space for the G clamps used to fasten the clamp onto the table and the tubing used to make sockets for the handles welded into place.

As a test, a 12" length of 0.071" steel was bent to make a blank for one of the spar attach brackets - works well, if it can handle 0.071" steel then 0.050" aluminium should be OK.

8h August 2008 - Flap and aileron torque tubes

The bronze "oilite" bearings arrived today so I completed the construction of the aileron and flap torque tubes. The bearings as purchased were 30mm OD and 15mm ID. They were drilled out to 18.5mm and then reamed to be a smooth fit on the 3/4" aileron torque tube. Oilite is very strange stuff! As the metal gets hot, oil bubbles out of the porous metal and as you drill it the swarf is like a dirty brown paste but they are self lubricating and they certainly provide a good bearing surface. The end of the flap torque tube was then heated to expand it and the bearing tapped into position (note for future reference - it's also an idea to put bearings in the freezer to make them contract before fitting). The bronze bearings are at the inboard end with Delrin bearings at the centre and outboard end of the flap torque tube.

An additional bearing was reamed to be a tight fit on the aileron torque tube. This was then cut in half and a piece inserted about 2" into the inboard end of each aileron spar. The aileron torque tube was then inserted into this and the washers made previously inserted at the end. The piece of bearing acted to exactly centralise the aileron torque tube in the spar and by inserting the aileron tube into the flap tube and lining up the two tubes the washer could be tacked in place with everything perfectly lined up. The aileron torque tube was then removed for final welding to avoid damaging the Delrin bearings. I might drill and pin the two tubes together through the piece of oilite bearing as a belts-and-braces measure but haven't decided yet.

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.