Renovation of the Starboard Aileron

Well into May now and my shipment of hardware is only just being shipped from America mainly due to some bulky items including the new windscreen having to be back ordered. In the mean time I have sourced the etch prime and epoxy primer from Trimite in the UK so I can start to strip one of the ailerons and prep all the aluminium components so that when the American shipment is received I can put the aileron back together.

I started by taking numerous photographs of the aileron and all it's fittings and fixtures as a reference for when I have to reassemble the aileron. I will also use the other aileron as a pattern and the wing as a jig for aligning the brackets. Next, I removed the brackets and put them to one side. Because they are visible they will be painted in the red top coat which I don't have yet so I will bead blast and paint these at a later date.


The aluminium leading edge was carefully teased off and the nails removed with with a nail claw. I used a piece of aluminium sheet to protect the spar from being crushed during this delicate operation. Interestingly the aluminium was stamped as 016" 24S-T which according to a colleague of mine, was last used as a standard in 1929. The equivalent today is 2024T3.



The ribs are nailed to the spar so again each rib is teased off and the nails removed. As the ribs are removed they are stamped with a number (starting with the inboard rib) so that they will be reassembled in the same order.





With all the metal work removed from the spar, the plywood patches used to prevent the spar from splitting where the brackets are bolted through the spar, are removed. Although these were glued to the spar they came away very easily. The spar has been crushed by the bracket attachment bolts and will be repaired later.









The only visible damage to the aileron is a small split at the inboard end which will have no effect on the structural strength of the spar.







The spar is then rubbed down with wire wool to remove the old varnish. New plywood patches will be glued onto the spar where it has been crushed. The patches will then be sanded down flush with the spar thus filling the crushed areas. New plywood patches will then be glued on to prevent the spar wood splitting when the brackets are attached.









Most of the ribs needed to be stripped of old paint. This could be done by rubbing down with scotchbright or another soft non-ferrous material but I decided to do this chemically instead to save time. I'm using a paint stripper formulated specifically for removing epoxy and polyurethane paints (D23V). It came in a 25 ltr drum which I have converted into a dunk tank by removing the top then pouring water onto the surface to create a barrier as the fumes can be toxic. The ribs were then suspended in the stripper overnight.






Next day the ribs were removed from the dunk tank. The old paint literally ran off the aluminium and after washing in clean water the results are very impressive.











After washing the ribs were treated with alacrom (surface treatment) to protect them. The ribs will then be painted with an etch primer and epoxy before reassembly.

I should be receiving the wood ordered for the door and skylight frames and the floorboards soon so that will give me another job to be getting on with. At least I will soon be reassembling instead of just pulling the aircraft apart.

The Harer STC

As part of the restoration project I will be implementing the Harer STC (Supplemental Type Certificate) which will have the benefit of allowing an increase in the aircrafts all up weight from 1200 lbs to 1280 lbs. Not a great increase but in addition to a target reduction of 50 lbs to the aircrafts current weight will bring a very useful increase of 130 lbs to the usable load.

In essence, the Harer STC calls for:

• An 85 hp engine to be fitted.
• The wing attachment fittings to be strengthened.
• The lift strut attachments (at the wing) to be strengthened.
• Additional cross bracing on the fuselage.
• Provision for a larger baggage compartment.

I already have the 85 hp engine and don't intend to add the larger baggage compartment as this goes against the idea of keeping the aircraft as light as possible, but the other modifications will be implemented.

So while I await the delivery of all the hardware, paints and fabrics from the States, I decided to do as much of the airframe work, that will ultimately require welding, as soon as possible.

The first job requires welding a diagonal bracing tube across the bottom of one of the fuselage bays. In fact two tubes are required so that they will form an X with an existing bracing tube. The first job was to work out how I could accurately cut the tube ends so that they would fit into the tube clusters and the existing bracing tube. Luckily I found a very useful web site some time ago and remembered to bookmark it for later use.

http://www.metalgeek.com/static/cope.pcgi provides a tube coping calculator that will give you a cutting template for joining two tubes. For the tubes I have there are various intersecting angles from 40 to 90 degrees. I've had a look at a couple of other programs for doing the same job but this one is very simple and straight forward to use.

Here's a sample template, downloaded in PDF format then printed and cut out ready to be wrapped around a tube.







The Template is wrapped around the tube, which can then be cut and ground to shape. I used a dremmel for grinding.







A finished 90 degree intersection.








The final join in the center of the X. This was straight forward as the intersecting angle is 90 degrees.







The rear tube cluster showing the new bracing tube in place. Cutting this pattern is slightly more complicated as there are two horizontal tubes which intersect at different angles. I used a mashup of two templates to get the basic cutting template and then had to finish the grinding by eye plus a lot of trial fitting until I was satisfied with the result.




The forward tube cluster was even trickier because there are two tube sizes and different angles. Again I used two templates to get the general shape.

The tubes will be welded in place once I have prepared all the other fittings such as door hinges, harness attachments and repairs to the rudder and horizontal stabilizers.

A new interior - Floorboards

I've been sidetracked so far this year with three other projects, a new car, an AD on Taylorcraft lift struts and the small matter of someone trying to build a new town on our airfield but I have at last managed to make time to start work on the aircrafts interior. The old interior was not unattractive or particularly tatty, but I feel that it could be better in a number of ways. The floor was the original aluminium which had been modified over the years and then covered with carpet. This will be replaced with a 6mm birch plywood flooring and aluminium kick plates.

Working on the principal that everything will have to be done at least twice before it works I set about creating a template floor in cheap 5.5 mm plywood first. This will then be used as the template for the final floor. First the shape of the current floorboards was transferred onto the onto the plywood.




I used a hole cutter and fly cutter to get the shape around the heel brakes. The rest of the cutting required is just straight lines at various angles.






I used a jigsaw to cut the straight lines which meant setting up a straight edge to help guide the saw. The calipers have been set to the distance between the edge of the jigsaw footplate and the saw blade. Once set this is used for all cutting.





Once cut, the floorboards (which are in two halves so that they can be removed) are laid out. I will have to make some fine adjustments before I am happy with the fit, mainly because the old aluminium boards overlapped and the new plywood boards have to but up to each other. This photograph shows the two floorboards in situ with work still required.



The bulkhead will slot into a grove formed by two quarter round strips of wood that will be glued in place. A battery box holding two sealed dry cell batteries will be fixed in the center of the bulkhead where it shouldn't take up too much space and will be easily accessible. It will also help fix the floor and bulkhead in place.

I still have to manufacture the kick plates and battery box before I'm confident that I can finally make the floorboards.

A new year and the first sign of trouble

January 1st begins pretty much as 2007 ended - foggy - so I'm back in the workshop to finish off removing fabric. All that remains are the rudder, horizontal stabilizers, elevators and undercarriage legs which shouldn't take too long.

The undercarriage legs had been recovered a few years ago when I discovered some corrosion and had to have sleeves welded over the corrosion so I don't expect any serious issues here.

Unfortunately as I began to strip the various components it soon became clear that there is serious corrosion in all the tail feathers and that these will all require time and effort to sort out.

Rudder
The rudder was the only area where there was a visible hole in the tubing although I have not carried out a punch test on any of the other sections of corroded tubing yet. It appears that moisture must have been getting through the fabric for some considerable time but because of the thickness of the Razorback fabric it was not obvious during any of the previous 9 annual inspections.










Horizontal Stabilizers
The horizontal stabilizers are mainly corroded around the fuselage attachments which means they cannot have an internal sleeve welded inside. Note that in the second photograph the repair is to a curved tube which will be more difficult to achieve.










Elevators
Similarly, there is a lot of corrosion around the weld clusters which will be much more difficult to repair and will probably require new U channel pieces and tube.



















With so much work to do, I will have to get approval from Carl, my inspector, for each repair method. The repairs must also conform to AC43.13-1B to ensure that structural integrity is maintained. For the moment I will try to reduce the opportunity for the corrosion to get worse while I try to figure out how to repair the damage.

Strangely, this has not depressed me but has confirmed the need to renovate the aircraft in the first place as I now know that in places it did need it after all.

Uncovering the Port Wing

It's almost Christmas and I've stripped the fuselage to the point that I can give it an initial inspection and satisfy myself that there are no major problems, or at least nothing that wasn't expected. so I thought it was time to check the wings out. Once I've stripped the fabric from all the major components I can put my orders in for the hardware, fabric, paints and tools that I still require knowing that I should have 90+% of all the items I require for the rebuild.

Starting with the wing leading edge, I cut the fabric so that it could be peeled back over the wing. Within two minutes I remembered that the first job should have been removing the tapes and Martin Wire clips that hold the fabric on.

Note that while removing fabric I use a mask and gloves to protect against the fiber glass and dust.



The tapes were easy to remove by cutting at one end using a craft knife (single edge razor blades are also good for this) then prizing the tape away from the main fabric with a screw driver to the point that I could just pull the tape off. This reveals the wire clips.

The quality of the wire clips varied from rusted or brittle to reasonably good condition although I didn't spend too much time trying to save all the wires as I have 300 feet of new stock that will be used on the wings when they are recovered.








The first look inside the wing reveals that it is in very good condition with just a little surface rust on the compression tubes and drag wires but nothing to worry about.

The spars look fantastic with no apparent splitting along the scarfed and lamination joints. Luckily my Farther was a carpenter and joiner so he had a quick look and declared the spars OK although the final say will go to Carl, my inspector.


With all the clips removed, the fabric was rolled back over the wing. The wing was turned and the process repeated on the underside.

Before starting on the next wing I will photograph each bay in turn and all the fittings. The second wing will then be stripped and photographed before I turn my attention to the ailerons and undercarriage.

Spiders Web - The Seat Support

In all the time that I have owned IH, I've never been entirely happy with the fit of the harnesses but I could never quite put my finger on what the problem was. Each annual, when inspecting the harness for wear, It would be bunched up in one corner of the triangular attachment rather than a nice even fit along one side of the triangle.

Now that I am able to get at and remove the spiders web that is the seat support I have worked out what the problem is and I think I now know how the support should be located. So before I forget all the detail I must commit it to paper or rather html.

This is the center of the cross support tube with additional straps (not standard) which have been added by a previous owner at some point. This was probably done to stop the support from sagging. Note that the two V shaped wires are held by a U clamp and the U shaped wire on the cross tube is virtually horizontal. This prevents full and free movement of the two triangular harness attachments. This as what caused my problems during each annual.


I decided that I would remove the support and assemble it on the workbench as it should be reinstalled.

The general layout of the support consists the cross tube, a supporting wire at each end of the cross tube and two V shaped wires (one being slightly shorter but made of a larger gauge wire, this was fixed to the rear of the support on the aircraft).





Each cross tube end has a supporting wire looped around it ensuring that the supporting wire goes through the U shaped wire welded to the tube. Note that the U shaped wire now hangs below the tube so that the harness attachment is free to move above the tube.





The center of the cross tube will also have the U shaped wire now hanging below the tube. I have looped the V shaped wires through this so that they will lock in place. If anyone knows if the two V shaped wires should interlock with each other, then let me know, although I already suspect that this is the case.

The frame will now be disassembled so that it can be straightened out a little, cleaned up and repainted.

Fuel Tank and Boot Cowl

It is early December and work is progressing as quickly or as slowly as I had anticipated. The fabric is off except for the area immediately surrounding the doors, instruments and panel are out as are the seat, baggage sling and floor. The next thing I want to tackle is the main fuel tank and boot cowl and for some reason I decided to do it in that order, probably because I imagined that removing the boot cowl would be more difficult than is actually was. In hindsight remove the boot cowl first as this gives you much better access to the nuts that hold the tank in place.

Removing the tank is not difficult in itself, just disconnect all the fuel lines, undo four nuts, remove the mounting rods and hey presto, one tank removed. Of course in practice there is muck skinning of knuckles as you try to reach that inaccessible nut or your spanner slips in a confined space.

The tank is held in place by two threaded rods that pass through the tank and then through short tubes welded to the fuselage tubing. These are locked in place by nuts.
To prevent the tank vibrating, felt is trapped between the rod and the tank (this can be seen in the picture where the rod exits the tank body.
All four nuts are fairly easy to remove allowing the rods to be pulled through the tank body. The tank can then be lifted out from between the fuselage tubing (this would have been easier if the boot cowl had been removed already because I wouldn't have had to maneuver the filler neck through the boot cowl which required a little forceful help on the way).
Note that the tank should also have some felt pieces glued to the side of the tank to prevent it from vibrating against the fuselage tubing.
The boot cowl was then tackled and this turned out to be very easy, just a matter of removing a couple of dozen screws from around the boot cowl and firewall. The boot cowl was then prized off the supporting framework revealing the tubing for the first time in decades.

This revealed the first bit of corrosion on the tubing. It looks like the paint had peeled off the tubing some time ago allowing the steel tube around the engine mount to rust. I have since used an automatic center punch to test the tube and found that it left only a small mark on the tube so I don't think the corrosion is serious although I will leave the final decision to someone with more experience in these matters than myself.



This nows gives me a lot more room to work and I have since removed the 'H' frame, rudder bars, aileron pulley's and cables. These have all been bagged and tagged and put away. Although it looks as though the fuselage is stripped, there is still a lot of work to do. All the stringers need removing along with the elevator/rudder control runs and I need to clean up the tubing so that it can be visually inspected for damage/corrosion etc.
Then I can start on the wings.