Warbird Information Exchange

We have quite a lot of plwood panels to remove on the fuselage, mostly because slopy repairs or them being oiled up.
But, the most serious damage is not always evident.
Here is the image of the upturned fuselage which shows the cut out for the center section. You can see that there is a patch in the corner of the cut-out.
Moreover, the patch is cracked again. Hmmm.



The other side revealed the same situation. Serious alarm bells started going off. Cracked on both sides, repaired and cracked again! What is going on here? Careful inspection revealed that the longerons can be moved slightly by hand in relation to the fuselage former/frame.
Therefore the longeron was delaminated from the fuselage frame - which is structurally a big no-no.
First the whole panel was removed:



Which of course resulted in a big hole:



With the panel removed, the movment of the longeron became even more obvious.



The longeron was reglued, and a new panel installed. Those small holes are supposed to look that way (wing tip position light, hydraulic line for brakes and pito-static lines).



Of course simply regluing the longeron back and covering it with a new plate is not enough. The essence are corner blocks. You can see them in this image, which shows the panel from the inside of the fuselage.



Work is repeated on the other side. On this image you can see the initial scarf joint preparation.



And look at that longeron go!



A wooden aircraft always gives signs of structure giving up. But unfortunatly most of the time, they are very subtle.
Kindest regards
Saso

Hello again,
Unfortunatly I do not have a lot of progress to report, since we were pretty uch caught up in some minor (or should I say petite) outside commercial work.
What you can see here is that the wood team was working on a Robin. There were some leading edge repairs, patches, replacment of some of the plywood skining etc.
As the work was minor we didn't transport the thing in our workshop, but did the work in situ.



On this second image you can see the nearest bottom suface wing root panel rotten, while the farthest is already replaced.

These Robin related stuff took about ten days and now the termites are back on the Aero-3.
To make it a bit easier to understand where exactly the work is going on I inverted this image so that it shows the fuselage in the upright position.
The angled end of the fuselage on the right side is where the firewall is.



The longeron was delaminated from the fuselage frame and therefore it had to be glued back on and larger corner blocks added. Notice the direction of the grain of the corner blocks.



On the really crappy image somewhere above you were able to see how the small longeron delaminted as well. This was reglued and again corner blocks added. This time it was a bit more difficult due to the fact that fuselage bottoms out about there and that there is a substantial fitting there.



The next steep is to replace the whole forward bottom side. This is done because the plywood is really oiliy since it is directly behind the firewall and also the fact that is has been patch-inspected/repaired on a number of places and is looking rather like a quilt. Some preparations were already made in removing the old plywood.




But, what I am happy to report is that the aft side of the bottom reskining is now complete. You can see the new panels in place.



Coming up this week (hopefully) is the skining of the forward bottom side and start of the inspection of the tailbay - always a critical item in wooden taildraggers.
Please indiciate if I should continue with posting these images. Some bloke actually tried to drive me away with posting an image of two very large wimmen, so maybe I am not really taking a hint?
Kindest regards
Saso Knez

Absolutely we want you to keep posting, Saso! I enjoy your photos and blow-by-blow explanations, and the fact that it is wooden construction rather than aluminum may teach some of the younger WIXers some new skills regarding aircraft restoration and maintenance.

As to those wimmens, I think Dan was just showing our Yankee pride with an example of.......never mind.

Keep up the great work,
Scott

Saso, the pictures are great. Thanks for posting them.

As for the picture, ignore him. He doesn't quite know how to make humor cross international borders yet...

I love these updates. Please continue with them

_________________
Magister Aviation
It's all in my book

So, here we go again.
This week was very active on the fuselage.
Ten days ago or so we de-skined the front lower portion of the fuselage. Again remember that we have the thing turned upsidedown. The section runs from the centersection cutout to the firewall.
This is how it looked when we removed all skinning:



The oil on wood was and still remains a big problem. Oil has a very bad effect on the glueing characteristics of wood involved. Therefore we decided to replace the two central ribs, that are more or less just big brackets for control column assembly. This was done because cleaning them would take the same or more effort. When making a list of things to correct we were a bit focused on the details like this one



This is the frame portion to which the bracket for the rudder pedals attach. As you can see more evidence of shody workmanship. The frame itself was doubled with plywood, but the plywood is too thick and somebody used a chisel to cut it down to correct size. We are having none of that in our airplane.
But then a big thing popped up. Again we found that the middle frame was delaminated from the longeron. How can you tell? Well if you exert a force on the frame it moves relativly to the longeron. In an effort to show you how much this is, I taped a measuring scale to the longeron and tried to level it so the frame is at 10.0 mm at the begining.



Then I applied some fore-aft pressure to the frame. The picture is a bit crapy, but I had only one hand left for the camera.



You see the movement was only about 0,5 mm but this has a determental effect on structural integrity of the aircraft. The usual tip off is that the skin cracks, but here the skin is 2 mm thick and managed to hold it's own.
The solution was more corner blocks. Now at this time I think most of you have some doubts of continually adding corner blocks. However, when we started cleaning the joints on the frame like the picture below shows, we found that corner bloks were originally installed, but they fell off.



Moreover during the last airframe overhaul someone painted new paint over remaining glue of the corner bloks and nobody cared about making the replacments.
We made ours a bit bigger, used way better glue and clamping pressured and doubled them with plywood gousets and I think that we are on the safe side. However during operations this will be an area that will be under constant observation.
In the mean time the afore mentioned rails/ribs were manufactured.

Here is a cornerblock with it's plywood guset installed.


Some more details for the fuselage were produced. This is a funny way of attaching a nut plate, but you can see here the old ones:



And the newly manufactured ones:




They are installed by gluing the face to the inside skin of the fuselage. Why they weren't just riveted on I'll never understand fully.

One such detail is the new mountning flange for the external power connector plug. This is made in very fine detail and is light years ahead on the cracked one, we had replaced.



And this is the whole assembly back in order. New ribs are in, corner blocks added, plywood doubler for the rudder pedals installed and drilled.



Other side view:



And looking at the frame that the spar connects to. Notice the scarfed in repair to the spar.



Well, this is more or less it from our side. This weekend I hope the bottom will be skinned over. Then we will turn the airplane the right way up, apply varnish to the inside of the new skins and start painting. After that the first steel and aluminium brackets will go inside permenantly. I already prepared and sent some of them for galvanic protection. I did this also with some of the stuff in the systems department like this drainvalve you see in the bottom image.



I'll check back in about 14 days when I will have something concrete to report about the work on the aft half of the fuselage.
Till then...
Saso

Thanks for the update, Saso.

Scott

I love this thread Saso! Thanks! Keep up the good work!

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DBF

The super-sized girls and I like this thread, too. Keep the pics coming.

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It was a good idea, it just didn't work.

Hey there,
I was in the montains during the weekend, and I must say that more work then I had hoped for was acomplished during my absence. (again this could be a hint!)
Anyway, we have the bottom skinned again!



Ant the other side:



This was a very dificult area to skin, as it curves in two directions and the plywood used is 2mm thick, which absolutly refuses bending.

On the second image you can also see the first step of making the engine bearer fitting reinforcment.
As this is an unusual sequence of making things, I documented the process to give you a general idea.
The first step is to glue several layers of plywood on the fuselage itself. If you can keep up the clamping process the result will be a fuselage conforming shape.



The trick is not glue the plywood to the surface -only laminate it together.



AS the fitting is level, this wooden part is a transition between the round fuselage and the plane fitting. You do this by running the completed plywood part over a good and accurate plaining machine. The end result is like this:



Of course the correct thickness is obtained by measuring it toward the fitting.



Today in the afternoon this plywood part was decked with a 1mm plywood face and left to set overnight. Tomorow we hope to finally glue it to the fuselage. After that the fuselage is to be turned over and varnishing of the inside will begin. At that time the woodworkers will move to the rear side of the fuselage, where they have some more work to take care of. A crack in the bottom skin was rectified during the weekend, since it is much easier to access with the bottom side of the fuselage upturned.



This is it from our end.
Kindest regards
Saso

I've done a fair amount of woodwork in my past. I must say that you and your team have great craftsmanship!

absolutely amazing work!

_________________
Magister Aviation
It's all in my book

Hi there,
First I must say thanks to everybody for the compliments. Especially to bdk, as I have visited your blog and your work seems like top notch.
Anyways:
the two faces of the gussets were decked with 1mm plywood, and glued to the fuselage. Phase finished. Now we will upturn it and start varnishing the insides of new skins. Fun times with a lot of visual progress ahead.
Here are the images of the gusset (still haven't found a way to spel it correctly...)