Zugvogel IIIa

[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]

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]

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]

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]

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 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]

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]

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]

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]

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]

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]

The fuselage still has assorted little pieces to add. Some balsa fillers are needed in the wing mount area. At least this keeps a few bits of balsa scrap from hitting the trash.



The stab is built next. It is just a simple balsa frame with ribs and a sub leading edge. The center is filled with balsa. It will have a bolt through it to hold it down. Some spacers were used to keep things straight when gluing the LE and TE. The plans had a 5mm TE and I used 1/4 balsa and created notches to align the rib spacing. The sheeting is a firm piece of 1/16 balsa. The sheeting was ironed on the first side,



Flip it over, and finish the infill of the balsa in the center. This is the top side so there is some 1/32 ply just under the surface in the bolt area. Some extra balsa was added for the hinge points. The second side of the sheeting will be glued normally and blocked up on some precut fixtures to hold the stab in alignment. The sheeting overlaps the TE to cover the hinge line gap.

[mlachow]

Next up is the fin and rudder. I need the fin to finish gluing the last former at the rear. The rudder post is glued to that former. It is simple construction, rudder post, ribs, and sub-leading edge get glued together. Then it is sheeted with thin plywood. The plans call for 0.6mm ply but that can't be found in the US easily. So, it is either 0.4 or 0.8mm, 1/64th or 1/32. It is not that large, and the sheeting extends back to cover the hinge line gap. I went with some 1/32 and sanded both sides before gluing it on. I used the iron-on technique to attach the sheeting. Precoat the contact areas of the sheeting and the fin with aliphatic. Let it dry. Then attach it by heating up the glue with a covering iron. The LE glued-on front and tip block finish the fin. It is also predrilled for the hinges

The rudder needed some "review". All the ribs are fine on the plans. But the side view does not have R6 and R7 in the correct location. I had used that originally to cut my rudder LE. And I cut it out of slightly thicker 1/4 balsa so I could put in slots for the ribs. I ended up cutting a new rudder with the corrected spacing. The TE has 1.5mm sprue and some additional 3mm balsa laminated to the spruce. The strip fits in a notch in the ribs. It easily builds vertically and easy to check that it is straight. The final detail is adding the gussets at the rudder TE. I precut the shapes from 1/32 ply and used some small chisels and a knife to fit them to the ribs.

[mlachow]

The front planking is almost complete. There are probably four strips remaining on the bottom.



The front end looks pretty good. It's time to do the first coat of filler. West 410 microlight is wonderful stuff. I mixed up some like creamy peanut butter and then spread this over the planking. One of my favorite building tools are the room key cards from hotels. They make great disposable squeegees and bend nicely to shape.

[mlachow]

Continue applying sheeting to the top of the nose. I got lucky and three strips each side fit with just a little trimming along the center. You can see the individual strips and the cut line down the middle of each piece. I mixed a little milled fiberglass in the epoxy for the joint at the cockpit area. Fit, glue, wait a few hours, repeat. I won't be able to do three pieces at a time on the lower part of the fuselage. I will do a little sanding on the plywood, then apply filler to the plywood. I will some of the West systems fillers with epoxy. I don't want to use autobody filler in the middle of winter. The machine cut planking pieces sure saved a lot of time fitting pieces.