Last steps of dismantling

Over the last week, Mark made great progress in removing the excess welding maetrial from the old repair. He pretty much removed everything that needed to be removed except the portion of the flat plates still welded to the bottom longerons.

 

I wanted to use these plates one last time before removing them and here is why. As I need to oversize the gear attachment bolts (AN5 to AN6 size), I need to get rid of the old bushings and replace them with larger ones. I decided to progressively drill them out until reaching the OD of the new bushings. In order to achieve that with reasonable precision, we decided to fix a mag drill on a steel beam sitting on the bottom longerons while the fuse was mounted upside down:

 

As you can see, having the old flat plates still welded to the longerons was a good reference to clamp the steel beam on the fuse. Big thanks to friendly Claude from whom I could borrow the mag drill.

 

While Mark was working on removing the old welding last week, I decided to take the opportunity to make a small modification to my landing gear. I wanted to do this for a long time and since everything is teared down, it is much easier to do it now: rotate my brake calipers aft. My original setup was with the calipers mounted downwards and I didn't like much the idea of scraping the caliper on the ground if I ever have a flat tire or tire burst.

After a few tests playing with the different components, I found the caliper position that I think was a good compromise; it needed a small adjustment of the nutplate attachment lug and a bit of trimming on my wheelpants.

First I washed the wheel hub and brake parts with varsol to have clean parts to work with:

 

Then, I slightly trimmed the nutplate lug, and with the use of a cardboard template and my Dremel with a cutting wheel, I trimmed of the piece needed on the wheelpant:

And here is the almost-final result:

 

I'm going to have a little extra trimming to do to clear the fitting on the top, but I preferred to have the final fitting in hand before doing that.

The 4130 steel tubes and plates are in transit right now. With chance, I will receive it this week and start trimming the first tubes this week-end!

Rack'n Roll

Last couple of days, I really experienced the benefits of my fuselage support. Once I removed the gear with the help of my friend Marc, I could swivel the fuse around to reach areas that would have been difficult to access without it. Wx was nice outside so I could make some progress on the tube cutting:

I tried various cutting methods and the best compromise I found between precision and efficiency was using a Dremel with 1 1/2 in diameter cutting disk for metal. I even tried a buffer tool but it is too big to perform the precision cutting when getting around a tube to be preserved and is not much faster than the Dremel.

 The following is the status of what I cut from the structure and what remains to be removed:

1. Gear support diagonal - Done LH - RH to be removed
2. Nut plate attachment lug - Done both LH and RH
3. Bottom central gear support - Done
4. Bottom gear support reinforcements - Done both LH and RH

Here's a CAD view to better visualize what parts I removed. I highlighted in blue the members in question. Note: I didn't model the nutplate attachment lug (#2):

...and here are the reasons for the removal of each member, again with the same numbering convention:

1. The LH diagonal was terrifying and I intend to comply with the Steen S1 drawings i.e. replace them with 3/4 in 0.035 wall tubing (was 5/8 0.035). Also, removing these will help getting access to install the lower longeron reinforcement sleeves:
2. Also need to remove the nutplate lugs to allow the installation of the longeron reinforcement. 
3. The welds were bad and the gear bolt bushing were welded to it. Since I will not need the inboard bushings (passing from 4 bolts per side to only 2), I decided to replace this member and remove everything I don't need anymore.
4. Same reasons as 3.

The CAD picture above also doesn't show the gear support flat plates in between which the gear was held. Here are a few pictures that progressively show the parts removed:


Before the removal of RH#4 and a part of #3:

Another view.. This one is very interesting: the crack due to the torsion of the gear is obvious. The crack propagation  is close to 45° which is a typical failure mode for round elements in torsion. ATTENTION PITTS OWNERS WITH SPRING GEARS WITHOUT RADIUS PLATES: THIS IS THE CRACK YOU DON'T WANT!!

Finally got the RH assembly removed:

Same cuts on the LH side (one of your last chances to admire the masterpiece (of shit) of an unknown welder):

Another interesting picture here.When I removed the RH nutplate support lug (#2) another crack was hidden under! This one seems also due to torsion, but aft of the spring gear. With time, the longeron section sitting on top of the gear would have probably broke, which is most likely what happened on the LH side. Makes sense doesn't it?

AGAIN SPRING GEAR PITTS OWNERS, CAREFULLY INSPECT YOUR LONGERONS HERE!!

Big thanks to my friend Scott who helped me pull the fuse back inside:

And last but not the least, a picture of some acro with Marc in the Citabria before my grinding Sunday : )

Coming up next: the removal of diagonal #1 RHS!

Full rack

This evening I finished the rack to support the fuselage. It allows the fuselage to rotate along its axis in order to provide better access to areas underneath. I made a triangle shaped frame in order to reach three engine mount bushings and let the fourth one free of any wood structure:

Different holes can be used with the dowels allowing to lock the position at 45° steps. The triangle frame can also be flipped over to let access to the RHS if required. I set the height so that I can easily remove the gear, however the price to pay is that the vertical fin doesn't clear the ground so I will warn my welder not to turn it past 135°!

Next target: gear removal and resume the grinding!

The first cut

Last week, my friend Marc helped me removing the tail surfaces. Two surfaces were a little more complicated to remove: the RH elevator and the LH stabilizer. The RH elevator was a little puzzle due to the trim tab cable going through it. What we ended up doing is removing the cable from the sleeve. This made the sleeve much more flexible and solved the problem. The LH stab was simply stuck on its leading edge attachment. I've put some LPS 2 lubricant and let it penetrate a few minutes and finally got it off.

This is what the fuse looked like once the tail surface were all removed:

This week-end I had an appointment with my welder, Mark Clément from Aérosoudage. The objective was for him to inspect the structure and determine the work to be done. The conclusion was encouraging; all bad tubes and bad welds can be either replaced or repaired. I am going to have to bring the fuse to his shop; this will help him getting a good setup and maximizes the chances of having a high quality repair. However, before that I have some homework to do: saw off the bad tubes and burn off the paint around all areas where welding will be required.

I also had the idea to build a support for my fuselage that is going to allow it to rotate. This is in order to help my welder to have good access to the areas that need work. I asked him if my idea was going to help him and he said it was going to make a good difference so I dedided to proceed. I bought the wood, cut it and started assembling it:

Today, wx was really nice and I couldn't stand the 2D world anymore so I went for one hour of fun in the Citabria in the morning.

Once back at the hangar, I decided to continue taking advantage of the nice wx and pulled the fuse outside and start my homework. I don't want to do any metal grinding in the hangar as it creates a lot of dust. I chose to saw off the member that I hated the most first (NB: don't apply this last sentence to members of your family). The sound of my airplane being sawed-off was a tad annoying at the beginning, but I finally got used to it...

Once the tube in question was removed I could appreciate how bent it was...

I also removed the lug on which the side panel nutplates are mounted:

Nice view of the lovely welds on the LH side. Admire the beauty of the paint on the gear and hardware. I am so anxious to clean all this...

That's about all I could do on the fuse before I mount it on my super rack and remove the gear.

I also went to Scott's hangar today to have advice about a repair I noticed on my header tank when I removed it last week. The tank seemed to be patched with fiberglass and an epoxy based compound that was hard like rock. Since I'm going to have a welder available, I thought I was going to convert this small repair also into a proper repair. Had no idea how to remove that stuff...

Good thing Scott knew that it took only a little heat! Used a paint removal heat gun and scraped off the compound quite easily:

I did not notice any crack under it, even with a magnifier. I suspect there was a leak there so I think I'm going to perform a dye penetrant inspection to see if there is a crack or a pinhole there. If so, I'll mark it for my welder.

That's about it for this week-end! I'm happy of the progress I made in the last coupe of days. Next time I go the hangar, my objective is to finish the assembly of my fuselage rack. Stay tuned!