Zugvogel IIIa

[mlachow]

Next up is the elevator. It is pretty simple. I will have to make a control horn to attach to the elevator in the middle. The tips were added to the stab. And the front, rounded part of the rudder has been added. The elevator trim tab still has to be cut in and added.

[mlachow]

Attaching the fin to the fuselage and build up stab mount. The rudder post was glued to the fuselage first. Time to get out the three-axis laser tor alignment. The fuselage is open so you can also see the light shining down between all the stations in the tail boom. The fin was still tilted a little forward but that is the next step.



There is another vertical piece that gets added near the front of the fin. That will get the fin to vertical relative to the fuselage line. Two other small formers are added in the stab area. Those provide the rest of the shape to the mount. There are precut pieces laminted balsa and ply that get glued to these formers. The front one is triangular. I used some CA to glue some triangluar stock near the front former so I could clamp it during the glue up. It took several clamps at each former as well as vertically to keep that piece against the stringer as it gets twisted near the front of the stab mount. It still looks straight.

[mlachow]

I added a few extra blocks of balsa below the bolt plate for the stabilizer. After gluing in these pieces, the ply bolt plate was added on top.



There will be a single horn for the elevator. It will be a wire on the center of the elevator and that will slide through a ball link in the pushrod in the fuselage. The front of the fin needed to be relieved a little to clear the elevator movement. Now I can add the final top longeron and do some some balsa infill in front of the stab. The rear of the fuselage will get sheeted with thin plywood.





A little vintage balsa going into a vintage sailplane.



The 1/16x4 is from around 1977

[mlachow]

The fuselage is off the fixture so now I can finish up work on the bottom near the front. The landing gear box needed a little work. I made some aluminum brackets to help out the 1/8 ply holding the wheel. It's a recycled Halco landing gear I cut up since the thickness was perfect Two M4 screws hold these to the ply box. Another long M4 goes through it all as the axel. A 50mm screw has just the right unthreaded length to make a nice axle.



Some balsa blocking has been added to the ply and stringers in this area too. This area will be sheeted with plywood. The wheel well was coated with some epoxy to seal it up.

[mlachow]

Now all the wheel hardware gets installed. Everything fits, the wheel rolls and there is not a lot of play. One side of the gear mount is threaded. The bolt will get threaded in there and then another nut will get added to the end of the bolt to lock the axle in place.



Time to finish up more of the front sheeting. The remaining strips were glued to the bottom of the nose area. Now the entire front is planked with 1.5mm plywood. The gear box area gets covered in 0.8mm plywood. The sides are real easy, almost flat except right at the front. I started with a strip and then marked the top and bottom towards the tail to cut it down to shape.



Next comes a coat of glue on the structure and then the ply is placed to transfer the glue to the plywood. Any areas that are missed get spread with a qtip.


I applied glue to the left and right side pieces and then let the glue dry. The final step is to position the ply into the proper position and start ironing the ply into place.


All that is left is a little trimming and standing on the bottom edge. Then the two bottom pieces of ply can be added.

[mlachow]

I used some drafting mylar to trace the area for the sheeting in the back. The tail skid is just a simple outline, simple and light weight. The simple outline is what is printed in Martin Simons 3-vew drawing. Pictures I have collected from the Internet have other variations.


The tail sheeting was ironed on. Plans call for 0.60mm ply but I haven't found any sources for that in the US. I am just using 0.40mm, 1/64 ply



A piece of carbon tubing goes through the rudder where the rudder horns will be installed. The skid is glued to the bottom. I will add a little light glass to the side next time I mix up some laminating epoxy for something.



The servo tray is installed up font down low.



There are a few remaining details on the back end to complete. The fairing in front of the stab. The elevator horn, and pushrods. Then the nose can canopy. This is mostly smaller stuff that can be done while waiting for glue on other parts of the construction. Time to clean off this work bench to get ready to build some wing panels.

[mlachow]

The workbench was cleared and cleaned up. A few glue spots to remove to get the bench ready. I had to do minor tweaks make sure the bench was level before starting the wing. Nothing worse than a bench that is not quite true.

The spar is long. I had some spruce that was almost long enough, but it still needed a little splicing. The spar also thins out on the last two bays since the ribs are so thin out there.

I also laminated the trailing edge. It is 1.5mm spruce with a balsa strip added on top. Two TE strips and two shorter strips for the ailerons.


The ribs were all checked and sanded to get them ready for the build. I used the LE of the ribs to precut the sub-leading edge strip close to size.


I used some foam board and cut slots in the foam board at the rib spacing interval. This will help line things up quickly when gluing up the wing ribs. I also made a shim for the trailing edge. This way the spar sits flat on the building board and the TE is close to where it needs to be. There are four wing alignment jigs sitting on the bench. They get used later when the top sheeting is installed to lock in the proper wing alignment along the full span.



I made a few tweaks to the construction materials. The ribs on each end of the spoiler bay are lite ply instead of balsa. All the ribs in between will be cut when the spoilers are done There are some 1/32 ply rib reinforcements near the TE. This will prevent accidentally breaking ribs before the cap strips are applied. It also adds a little strength if some plastic sailplane guy grabs the airplane by the TE while it is in a hanger. Nothing worse than seeing a crack in your TE in the morning.

Time for some glue and clamps. Lots of clamps.

[mlachow]

I glue ribs in groups with the alignment guides. They hold the ribs nicely while applying glue. The ribs are glued to the trailing edge and the spar. I have a good collection of steel and brass strips. Great for holding things down and all in a straight line. I precut all the webs with the router. They are just sitting there for later use. The ribs at each end of the aileron are doubled. The TE of the wing in the aileron area also had notches precut for alignment.


Some of the center plywood ribs were glued with epoxy. The joiner goes between the spar so those ribs are cut in two pieces.. You can also see the holes for the servo wires, predrilled. The sub LE is not yet glued. It has a few shims glued to it and it is just held against the ribs by the brass bar.

After the glue dries on the bottom spar, the top spar is glued in and the sub LE is glued in place. Now all the webs can start being glued in place. Sometimes I use bar clamps, other times I use some cauls and spring clamps.

[mlachow]

I didn't post everything last night. After the webs are all glued in, an additional 5mm sq spar is added in front of the web for the center part of the wing. You get a nice I beam. The recommended construction method was to glue in the first spar and web, then cut in the ribs for the second spar. I just cut a wider rib slot and made sure the rib was against the back of the slot. I also used q-tips to make sure no excess glue was in the rest of the slot. Only a little bit of cleanup with a file was required to fit the spar. A lot of the other work done today is dry but I want to wait overnight until removing it from the board. That way the glue is really dry and the epoxy is fully cured.



After gluing, get out a lot of clamps.



And while I was waiting for the webs to all dry earlier, I built an aileron.

[mlachow]

The bottom spar doubler is now glued into the panel. The sub LE has also been shaped.




There are also a few spars to cut in. One on a diagonal near the root for the end of the sheeting.



The other will be for the spoilers. These need to be cut on both wings on both the top and the bottom. I made a template to guide the cutting.

[mlachow]

Time to start the second wing panel. Same thing over again, sand all the ribs and webs. Splice the spars. Glue...... Stopping for the day just before starting all the webs.

[mlachow]

Progress continues on the wings. The first panel now has one side sheeted and the second one is getting close to that point.



Found some nice vintage balsa suitable for the leading edge sheeting.


Both panels are off the bench so I can make sure the joiners are all in alignment.

[mlachow]

Both wings now have sheeting on one side now. I worked on some other wing details before final sheeting. The servo mounts for the ailerons were glued in.


I also cut some balsa sheet with a nice hole and servo covers to screw on the wing.


I have to build the spoilers before I glue in the spoiler servo mount.

[mlachow]

The elevator linkage will be a cross between the setup Chris Williams uses and a Pike Perfection. I used some brass sheet and made two straps so I could solder some music wire as the control horn. The elevator is one piece and this will be bolted to the cross piece. The linkage will end up inside the fuselage.

I put the big 4mm tip on the Hakko iron and got out the flux pen. No problem tinning the wire and the solder flowed nicely under the straps and even from the wire to under the straps.



Cleaning up a little and you get a nice horn. I might need to bend a little angle in the wire.


The second piece is a length of brass tubing and a little piece of brass I machined to accept the tube on the one end. The other end is tapped for a M2 screw to hold on the ball link. The pushrod will need a support guide under it near the elevator. The elevator horn just slides into the brass tubing when the tail is installed. I will need to trim the wire length a little and the ball link i the photo is sitting 90 to the real pushrod direction since it is just flat on the soldering pad.

[mlachow]

I found some useful documentation. It starts around page 33 for the IIIa.

https://www.ig-scheibe-flugzeuge.de/wp-content/uploads/Zugvogel_01-01-2021.pdf