Sunday, 8 November 2009

Harness Brackets

When I bought IH back in 1998, the aircraft was fitted with a 4-point harness where the shoulder straps were attached to the cross tube that supports the top a the seat sling. This was totally unacceptable as in a crash this can lead to compression of the spine and severe back injuries. Later I moved the attachment position to one of the top cross members further back in the fuselage using a U-bracket around the cross tube. This was better but not perfect, so now I'm taking the oppotunity to weld some permanent brackets into the airframe.

Two brackets were cut from .090" 4130 steel plate and drilled to take an AN4 bolt. After welding, the holes will be reamed out to size.

Port and Starboard fittings

Saturday, 7 November 2009

Refurbishing the Fuel Tanks

IH has three fuel tanks, one in each wing plus the header tank in the nose, and these need some refurbishment and pressure testing before they are refitted. For now I only need to have the nose tank sorted but I'll work on all the tanks as they will all need the same treatment.

Firstly, I bought new fittings for each tank to enable me to fit all new AN fittings throughout the aircraft. The tanks still have their original heavy fittings and also showed some signs of mistreatment around the filler where the pipe has been used unsupported when fueling. So the plan is to weld in new fittings and filler necks and reinforce the area around the filler necks.

The tanks were sent away to a local CAA welding company; the tanks were labelled with the fitting part numbers next to the appropriate existing fittings. The results of the welding are shown below.

Main Tank

Wing Tank
The tanks were also pressure tested by the welding company and all pin holes and cracks welded, so I now have a good set of tanks.
The paint was then stripped from the outside of the tanks using proprietory paint stripper and scotchbright to produce tanks ready for priming.
The tanks were first painted with an acid etch primer and then painted in a white epoxy primer. The nose tank will eventually get a white top coat as well as this is visible within the cockpit. Note that when painting the fitting holes were blanked off to prevent paint getting either inside the tanks or into the fittings threads.

The finished epoxy primed tanks.

More on Floorboards

It's been a while since I made the mock up of the floorboards but at last I made the effort to get some qualaity birch plywood for the final product. Using the mocked up floorboards with I marked out the outline of the floorboards onto the birch ply paying attention so that there were no blemishes in the birch.

There were a couple of differences between the mock up and the final boards (go to to see details of the mocked up floorboards) to incorporate improvements, mainly around the cut out for the brake pedels.

Cutting was done with a band saw, fly cutter and fret saw to get the required shapes; one useful tip here is to score the underside of the ply along the proposed cut with a knife, this prevents the underside from ripping when sawn giving a clean edge to the ply.

The boards were drilled to take the self tapping screws that will fix them to the fuselage (tabs on the fuselage will have tinnerman nuts fitted).

The boards were then sanded and given a brush coat of varnish. Once this had gone off the varnish was sanded lightly to de-nib it and thre more layers of varnish were sprayed on. For spraying the varnish was thinned down with MEK in the ration 1 part varnish to 4 parts MEK.

Finally the bulkhead under the seats was cut and fitted. This is screwed into the crossmember under the front of the seat sling and will drop into a slot formed by two quater round strips of wood glued to the rear part of the floorboards. the battery box, which I have yet to make, will be positioned in the middle of the floorforward of the bulkhead.

I have still got to get a couple of extra tabas welded to the fuselage frame to provide additional anchor points for the floorboards but this should be done within the next couople of weeks as I write.

Sunday, 16 August 2009

Making new rear d-windows

By June it was clear that there were a number of tasks that needed doing before I could go ahead and get all the welding done on the fuselage. One of these taks was to build new rear D-windows. This was important as a tab would have to be welded that would fix the window to the fuselage and tie the window into the stringers along the fuselage.

The old D-windows looked very similar to the Harer STC windows but the position was wrong, they were fixed too high so that the top of the window was higher than the door frame and the line of the door window was not carried through to the rear window. The old window frame was also very heavy so I also have the oppotunity to make thing lighter again.

I have no specific plans for constructing a set of windows so I based the shape of the new windows on those in the Harer STC but slightly smaller. The design was schetched out full size on stiff paper which was then taped to my work surface. The main difficulty was getting the correct angle between the rear door frame (to which the window will be attached) and the line of the door window so that the top of the two windows will line up correctly. I cannot guarantee that this is the same on all aircraft but it worked out to be 100 degrees for me.

The frame is made in two parts, the main part holds the window glazing and is attached to the door frame with machines screws and nuts, and the fusalage tubing with self tapping screws. A separate outer frame is then used to trap the glazing in.

The basic window frame was cut form 0.020" NS4 aluminium using a band saw. The inner curves being cut with a fly cutter and a similar process was used to cut out the outer frame. finishing was achieved using aluminium nibblers and lots of filing starting with a course file and gradually finer files until the final finish using fine grit paper.

The next step is to recess the main frame to take the 2mm Lexan glazing. This was done using Rob's metal rollers. Rob adapted the rollers so that they could take attachments for putting joggles into sheet metal. Manually adding the joggle to the inside of the main window frame resulted in a very pleasing finish although it introduces a warp across the sheet. The warp will be taken out when the edges of the window are bent to stiffen the frame.

At this point the Lexan was cut to size and fitted to the frame. Remember to drill the holes in the Lexan slightly oversize to allow for expansion and contraction with the weather etc. Self tapping screws are used to hold the outer frame and Lexan to the inner frame.

Finally, the frame is bent at the edges to add stiffness to the whole assembley and provide a surface to mate with the door frame. There is still one or two minor tasks to do with fixing the window to the door frame mainly to do with cutting slots around the door frame mounts so once this is done I'll post pictures of the windows in situ.

I've also sent the fuel tanks off to have new fittings welded in and have the tanks pressure tested and have sent all the tail feathers off to have some remedial welding done. At the time of writing, these are back so the next blog will probably show the results of the welding and the work that is progressing on the renovated tail feathers.

Tuesday, 5 May 2009

A new set of aileron hinges

One of the common maintenance issues with Taylorcrafts is th onset of wear in the aileron hinges caused by the hinge rotating against the clevis pin. This is often noticable on the outer hinges and can be checked by pushing the aileron up at the tip; you will feel the movement on the hinge, it's fairly obvious. A small amount of wear is acceptable but as mine are worn to a point where they are only just acceptable I've been on the lookout for a new set of hinges.

Initially I approached the Factory but due to complications regarding the export of stock oversees, and the fact I discovered that I had Rob's jig for the job, I decided that it would be just as easy to make a new set. The jig, in two parts forms the basic shape of the hinge and allows the mounting and pivit holes to be drilled and reemed.

The basic set of six hinges took a weekend to make using the jig and some 0.050" 4130 steel sheet.

1) Six oversize blanks were cut from the sheet steel. The size is sufficient that each piece fits snuggly in the jig ready for pressing.

2) The basic shape is pressed using a vice.

3) While still in the jig, the mounting and pivit holes are drilled and reamed.

4) The blanks are roughly shaped (original hinge shown for comparrison).

5) Final finishing with file and wet/dry paper and comparrison with an original hinge.

6) The final modification is to spot weld a tab onto the hinge to provide a flat. Each clevis pin will have a flat filed to fit thus preventing the pin from turning against the hinge.

Lastly, my thanks must go to Rob Lees and David Nowill, who between them, designed and manufactored the jig, and then let me use it.

Finishing the Ailerons

I have finally gotten two refurbished ailerons, but before I put them to one side, I wanted to check that everything fits in relation to the wings. I'm basically using the wings as a jig to check the alignment of the ailerons with the new hinges.

The port aileron fits without a hitch but the alignment on the butt rib of the starboard aileron is out for some reason and of course I've no photograph to check the alignment prior to the rebuild.

The extent to which the but rib is out of alignment can be gauged by looking at this photo, about 1 cm at the trailing edge.

To rectify this, I've used a piece of trailing edge, cut down so that it forms a box section that will fit inside the existing trailing edge when it is cut.

After riviting, I will fill the gap with micro balloon filler so that the repair will be less obvious. The rivit heads will be visible because they couldn't be countersunk but tey are no worse than screw heads used all along the trailing edge.

I've checked the fit after the repair which gives a much better fit now with the wing. The ailerons will now be put aside, uncovered, until I come to rig the aircraft way in the future.

Now back to the fuselage and a lot of welding work....

Monday, 9 March 2009

Ailerons and Skylights


Just a quick update on the progress of the 2nd aileron. Firstly all the ribs, leading edge, trailing edge and hardware have been cleaned, etch primed and epoxied and are ready for reattaching to the spar. The spar has had some repairework carried out to fix the crushing similar to the first spar. There was also a minor crack running lengthways along the spar from the but, about 6" long and about half the depth of the spar. This will be patched as the majority of the crack lies under a plywood reinforcement plate. The spar had a second coat of varnish at the weekend so I shall be able to start reassembling the aileron next weekend (although I may have to do some gardening as well!).


In the mean time, I progress with the skylight woodwork.

Lets refresh our memories of the old skylight. It extended from the windshield back for nearly two bays, held in place by wooden formers and steel angle (see below).

The second bay does not increase the viewable area and just adds to the weight of the aircraft for no advantage; so on the rebuild I
will stick to a single piece skylight covering the first bay only.

The frame will be made from the same Ash plank used to make the door frames, using the existing frames as a template. These are rough cut with a band saw then shaped with a spoke shave and finished by sanding. Various notches where cut with a fine chisel.

Some time later after many trial fits, the basic frame sits on the fuselage. Note that instead of using a piece of steel angle on the sides, I'm using 1" thick wood (still much lighter).

My plan is to fix the skylight (3mm clear acrylic sheet) to the frame by embedding a threaded insert (below) into the underside of the frame that I can screw into. In addition I will have four internally threaded steel tubes welded to the cross frame of the fuselage which will suport the skylight and give it some rigidity

I hope to pick up the acrylic sheet next week which will be cut to shape, drilled and used to determine the location of the threaded inserts.

Next week I'll try and update you with the aileron reassembley and possibly a bit more on skylight progress. Untill then happy flying.

Sunday, 11 January 2009

First Aileron Complete and a New Hat Shelf

A few photo's of the completed starboard aileron showing the strenghtened but rib.

The tip end rib also had to be replaced as the wood was cracked and had lost much (if not all) of it's residual strength.

Two general pictures showing the end result.

Although I will be starting on the second aileron next week I have also started looking at the design of a map shelf to fit behind the baggage sling. The design (I admit) was taken from that used by Rob in the restoration of G-BREY. Steel tabs will be welded to the fuselage so that the aluminium shelf can be screwed in place with machine screws. The map shelf is large enough that it require stiffening to prevent it from sagging even though it is not intended to support any real weight. It is far enough to the rear of the aircraft that any weight in this area will impact on the c of g of the aircraft.
Next week I'll post more details on the design of the map shelf and the stiffeners to be used.