This is a bit premature, but we have the main spar and front spar aligned with the landing gear, so it was just too tempting to sit in there and play with a stick.
Here's another view of the gear and spar conjunctions:
Now these are ready to put in the jig.
I'm drilling some holes in the fuselage frames and spars for the rudder cables, battery cables, and other stuff. Some of the holes go at an angle, so my drill press is not much help.
For the smaller holes, the portable drill guide works fine. This has an adjustable base, so it can be set for small angles.
The drill guide has a 3/8" chuck, so for bigger holes, I used an idea in the latest EAA magazine. To drill a 1/2" hole, I started with a piece of 3/8" pipe, and drilled it out with a 1/2" bit. Then I welded up a "C" with two bolts and a piece of scrap, and brazed the pipe in place. Next, I cut out the pipe so it would fit over the spar. Mark and pilot drill the holes on both sides of the spar. Insert a 1/2" bit backwards in one end to position the guide at the correct angle (15 degrees for this one), and start drilling through the pilot hole on the other side. In the picture, it looks like one long drill bit, but it really is two bits. Kind of reminds me of a magic trick.
This frame is glued to the front face of the forward wing spar. Since this spar also carries one end of the landing gear pivot shaft, I've clamped the forward spar to the main spar using the landing gear pivot hardware for alignment. Next, I leveled the main wing spar, and checked for vertical on the #4 fuselage frame center line, since that frame is now glued to the main spar. Finally, I attached a plumb bob at the center line on the top of frame #3, and clamped the frame in place with the plumb bob over the front spar centerline after making sure that centerline matches the spar centerlines.
After double-checking all of this, I'll drill holes for dowel alignment pins so all of this can be unclamped and reclamped for gluing. Also, there is a cavity between the frame and spar that needs to be varnished.
The gray metal gadget is a drill guide to assist in getting the dowel alignment pins square.
The view here is from aft. You might wonder why the forward spar is clamped behind the main spar. It's just that this turns out to be a convenient arrangement for aligning the landing gear hardware, and everything else is relative to the gear. There's no chance I'll forget to put the front spar in front eventually.
The #3 frame carries the base of the windshield.
Hooray for the shortest day of the year!
The first task was to lay out and cut the notches for the fuselage longerons in the fuselage frame. I made a master template for this that can be used with all the other frames.
The #4 frame is the largest of the frames. It forms the "roll-bar" of the cockpit, and supports the canopy latch. It is fastened with glue to the front face of the main wing spar. It is an important glue joint, as it provides a lot of strength in mating the fuselage to the wing. It needs to be positioned with accuracy. For this job, I removed the spar from the jig. Three holes will need to be drilled through this assembly for the gear retraction gearbox.
The Christmas lights are not permanent, only seasonal!
In preparation for attaching frame #4, the wing spar needed to be trimmed to close to its final dimensions. These were determined from templates I made from plywood for transferring the rib chord lines to the spar. The trim lines could then be placed by measurement from the chord line (a chord line is a bit like a center line, but its not in the center of anything, more like a free spirit). The gap between the try-square and the wood shows the taper that the top surface of the wing will have. When you multiply this cross section by a 27' wing spar, it amounts to about 2 gallons of wood shavings. For this task, I purchased an electric hand-held planer, which made the task easy. The angel is taking a good look at my work, so as to report to my guardian.
Happy Holidays everyone!
Time to build the wing. The first step is to build a jig for it. The wing is built in a vertical position, with the leading edge up. Since the fuselage is attached to the wing, the center section of the fuselage is part of the jig. In the photo, the horizontal slots in the center section will hold the fuselage frames.
In addition to supporting the ends of the wing spar, the endpieces establish the angle of the ribs with reference to the horizontal, or 0 degree angle of attack. The wing chord line is marked on the jig endpiece, and will be matched up with the rib chord line when the end rib is installed. It also locates the strings that will be stretched along the leading and trailing edges. This photo is blurry, but the wing chord line appears at the top of the "window" in the center.
The wing spar supports were leveled with a water level. The "horizontal reference lines" for each piece were positioned with plumb bobs. Because the wing is in a vertical position, 'horizontal' is vertical here. The end pieces are braced with wires and turnbuckles. The center piece is braced with a diagonal 2 x 4.
Yes, I've moved to the big shop. Aligning the jig is too difficult where a wall intervenes. Besides, to work on the other end, I'd have to pull the whole thing out and turn it 180 degrees, and reposition it, with a lot of adjustments to assure level and plumb. The main disadvantage to this shop is I can't control humidity. But for attaching ribs, this is not an issue. I'll be working on ribs for a long time.
The jig is on a plywood and 2 x 6 framework that can be skidded around if need be.
Well, harvest is done, so back to the shop. In August I did some research on wheels and brakes up at Oshkosh, and decided to go with Beringer. Wheels and brakes are not included in the Seqair kits. The most commonly used are Cleveland 5.00 x 5. Those have steel rims and the Falco pilots I have talked to all want a little more braking power. The Beringer wheels are aluminum, and 5-6 lbs lighter. Saving 5-6 lbs is not a trivial matter in the Falco, as there are not many ways to do that. Several builders have changed their nose-wheels to Beringer, and they have told me if they were at my stage they would use Beringer for the main wheels, so that's what I'm doing. Another benefit is that the brake pads are much easier to change with these. Here's what came by FedEx the other day, from France:
The two red tubes are the master cylinders, one for the left wheel, one for the right. The blue chunk is a parking brake. The red block in front is an adjustable brake action limiter. When it is set properly, it will prevent the brakes from locking up. It's not quite an ABS system (there are no electronics), but more of a pressure limiter. The two boxes hold the brake fluid reservoirs. The axle nut on the right wheel will not tighten up properly because Beringer shipped it with the wrong threads. They have promised to machine new nuts for me with the 12 UNF threads I need.
Where does the time go? For sure, some of it went to planting and weeding, all necessary for buying Falco kits. Anyway, the work on the main wing spar and the front wing spar is about finished. The front wing spar is now closed in. I've also received the main gear kit, and have the fuselage frames on order, with those scheduled to arrive in a few days. The holes for the main gear were drilled by the factory, so those were not a problem. However, there are matching holes needed in the front spar. To get these aligned, I drew the wing rib chord lines on the main spar, and the corresponding line on the front spar as directed by the manual. Then I installed the gear support flanges to the rear of the main spar, and drilled a small hole through the front spar to hold a matching flange in approximate position. Next, the front spar is clamped in position. It looks like this:
As you can see, the spar is now installed in the shop. After making sure everything is in the right place, I used a couple of dabs of epoxy to fix the front spar flanges in place, and drilled the bolt holes. Here is a photo of the front spar removed from the clamps after the epoxy has cured:
The small hole to the right of the flange on the main spar is for the gear side load fitting. Since the photo, that fitting has been installed as well. The wing rib chord lines are drawn on the fore and aft faces, as well as the spar trim lines. I should be installing the aileron bell crank supports now, but there is a part for that in the control equipment kit, which I have not yet ordered, so that will have to wait. When the fuselage frames arrive, there will be quite a lot of work on those before the real wing construction can begin. One of these frames is glued to the main wing spar, and that will be one of the first steps.
I'm off to Oshkosh on the 28th to 30th, and will be checking my email, so if you're there over those dates, drop me a line!
I've been slow to post here, but it seems there is more to life than building a Falco, as impossible as that seems! I went East to visit family and friends in early March, and hiked in the central PA woods. After returning refreshed from that, two days later I went in for some surgery. After 2 weeks of recovery, I'm feeling better, but still have a week to go on my activity limits. Even so, I've managed some work on the wing spar, and have varnished the interior, and glued on the forward face plywood. This is a bigger job than the other stuff. It took almost 300 g dry weight of Aerolite! I used twine for retrieving the staples. Here's what it looks like:
Preparing for this meant cutting a number of holes in the plywood skins. The aileron pushrod holes show in the photo above. The photo below shows two small round holes for the rudder cables, and some elliptical holes for tubing and various wires. I'm also still working on the ailerons/flaps, and will be putting on the final skins for those in coming days.
This is a fairly critical step, because if the spar is twisted during the process, it will stay twisted forever after the glue has cured. It's fairly easy to tell if something is awry, because the trailing edge will go out of alignment if the spar does twist. I tried clamping to a cleat on the table, but that twisted things very badly, so I changed to running the clamp at an angle to the spar itself, which seemed to work well. Also, to get the skin to tighten down properly onto the ribs, I drilled a 1/4" hole in the surplus plywood by each rib, and applied tension with a screwdriver as I was stapling the skin to the rib. Judging by the glue squeeze-out where that was visible around the hinge openings, this helped put the skin where it should go. The photo shows the clamps and the screwdriver-tightener:
After the glue had cured, I dug out the staples and trimmed off the surplus leading edge plywood. The trailing edge is straight, so this should work OK. I then scarfed the plywood on the spar end with a belt sander to get ready for the trailing edge skins. It looks great.
With the float sanding on the left set finished, it's time to start with skinning that assembly. The first step is to bend the 2mm plywood for the curved upper surface of the leading edge. To do this, I reinstalled the table extensions so the assembly could be clamped into a vertical position. I soaked the plywood 48 hours in my hot tub, and bent it around with the aid of the steamer and clamped it into position to dry. Here is a photo. The right assembly is in the background in position for the final float sanding on the lower surface.
The plywood is not glued in place yet, just bent so that after it dries, it can be stapled down without any steaming. It is important to clamp the spar without any twist when working with the upper front skin. This skin will brace the spar from twisting, so any errors will become permanent after gluing. To check for twist, the manual suggests to draw a horizontal reference line on one side of each of the end ribs while the framework is resting on the table. After the assembly is clamped in the vertical position, the reference line can be checked for vertical with a level. Do this on both ends, sight along the trailing edge to be sure that is straight, and all is well. All of this is critical so the wing root stalls before the tip, thus maintaining control deep into the stall.
This isn't very exciting to watch. It's sort of like watching paint dry. I'm pretty much done with floating the tops, and have turned over the left side to start on the bottom.
Behind the spar, both top and bottom surfaces are concave. I'm clamping a piece of 1 mm plywood over the ribs as a shield while working on the edge of the spar to get it down to dimension. I've screwed a 1X4 to the edge of the table to support the trailing edge strip while sanding. I'm not very happy with the placement of the trailing edge strip in places, and it looks like I'll need to cut it loose on the ribs where it is off and reglue. I had convinced myself it was OK when looking at it from above, but now that it's turned over, I can see the alignment with the ribs is off 1 or 2 mm in places.
This photo shows the leading edge ribs and strip in place for the left aileron. The strip is made of oak, and is 20 x 20 cm. This is bigger than structurally necessary, and of course oak is heavier than spruce. The idea is to get enough weight in the leading edge to balance the aileron. If the aileron is not in balance, it could flutter, which is very bad. The flaps are less of an issue, so the leading edge there will be 15 x 15 spruce. I did as much work on this oak as possible before gluing it in to minimize the float sanding that will be required to get the airfoil. One nice thing about having the balance weight built into the structure is that one doesn't have to worry about the weight working loose. One of the steps on the preflight checklist for my Cessna is checking that the lead weights crimped into the forward spar of the ailerons have not worked loose. That won't be necessary with the Falco.
The right aileron does not have the leading edge strip in place yet. I'm just finishing up with gluing in the leading edge ribs. This photo shows how I used the same angle guides from the trailing edge rib job to get the angle with the spar right. Note the diagonal trailing edge ribs that brace the area of the spar where the controls connect.
Before the skin, however, are the ribs. There are 14 of these on each side, fastened to the spar at 81.9 degrees. Also, the elevation at the trailing edge increases .5 mm with each rib going outward. I have trailing ribs on one side installed, the other side has most of them glued and in the jig. The double rib in the center is where the aileron and flap will be separated. The entire trailing edge is built as one, and the movable parts cut apart later.
The jig consists of the table with some uprights screwed into the edges to hold the spar at right angles to the table top, some angle brackets, a notched stick, and the trailing edge strip, also notched. Here is a closeup:
The clamp at the extreme right is holding the spar to a vertical strip. The angle brackets are cut at 81.9 degrees, and have some strips of ply glued to them so clamps can be used. The notches in the stick are cut to the proper elevation for each rib. The trailing edge strip has precisely cut notches that fix the trailing edge laterally. If for some reason the layout on the spar and the angle clamp does not put the rib in position to line up with the notch, it's time for some checking and head scratching. I've scratched my head enough by now that my hair is turning white and getting thin, but eventually things work out. It's essential to have two or three ways to check everything before committing with glue.
The first work on the flaps and ailerons is closing in the open spar face. The spars are shipped open so you can look over the glue joints before closing them off. After that comes fixing in place the hinges. Since the hinge line is not parallel to the spar face or the spar center line, the alignment is not straightforward. To align the hinges, I used the threaded rod shown in the photo in place of hinge pins while marking the holes. I tried steel rod, but it was a bit over size. Aluminum rod had a tendency to seize up in the hinges, and wooden dowel was not very accurately dimensioned. The threaded rod worked for me. I ran nuts and washers up to the hinge assemblies, and tightened things up while hand drilling the marker holes. I finished the holes on the drill press, and tested each hinge for binding before going on to the next. I had to redrill 3 of about 50 holes.
Under the wing spar fittings, there are thin tapered pads of plywood, about a 1:40 slope. This slope matches that of the hinge line in a vertical direction as the spar rests on the table. I made these pads with my scarfing rig set to 1:40. I'm afraid that this photo is out of focus, but maybe you can make out the base of the fitting and the glue lines in the tapered plywood.
On most aircraft, the hinge lines would be parallel to the spar. Parallel is simpler, but nothing is spared on the Falco to create graceful lines and lots of work for the builder.
Well, here it is, the main spar, all 27+ feet of it. It arrived just before Christmas in an ice storm. It looks a lot longer than 27+. It will take a lot of ribs and plywood to make this into a wing. Right now, I'm working on an auxiliary spar and the aileron/flap spar. Building the ailerons and flaps will occupy me for a while. We had a Christmas day blizzard that promises to curtail any farm work for some time to come, so I'm glad to have this project.
I haven't posted in a while, because I've been busy. On Wednesday I finished with the harvest. As Frank Sinatra would say, "It was a very good year", with record yields and decent prices. Yesterday I cooked a turkey and creamed onions, and the rest of the family brought more food so we had our Thanksgiving feast. Here's some of us enjoying pie:
And here's some more (you must be short to sit at this table)
Today I resumed work on the fin. Over the weekend a friend from Wisconsin stopped by and helped me glue on the left fin skin. Now, I'm steaming the skin around the leading edge in preparation for gluing there. I wasn't happy with using bar clamps for this. It worked, but it was awkward. If you tighten a clamp, the ones next to it loosen up and fall out of place. So I tried these ratcheting straps, with the ends hooked over the spars.
Here is what it looks like with the skin bent around. The screws in the stiffener keep the strap from sliding towards the top of the fin. I really like the straps for this.
In a week, I'm off to France for some R&R. Meanwhile, Sequoia Air is preparing the wing spar for shipment! It should be here along with a whole lot of pieces shortly after I return. The box in the back is full of small parts, so I'll check those before I leave.
A bientot!
This shows the fin with the number one antenna installed. The idea is that Unicom signals are vertically polarized to a greater extent than other comm signals, so this antenna should be vertical. It's a dipole, and consists of two pieces of 1/2" wide copper tape along the leading edge of the fin. It's important to keep it away from the hinge hardware. The advantage of a wood airplane is that the antennas can be inside the structure, thus avoiding unsightly rods sticking out. The coaxial leads are soldered to the ends of the poles, and covered with a piece of fiberglass cloth/epoxy to secure the cable.
There will be additional antennas in the wings.
The fin tip bow is attached, alignment is good, so now the fin can come out of the jig. This feels like progress. It's a big thrill to see this take shape.
The next step is to disassemble this and skin the fin.
This photo shows the clamping system recommended in the construction manual. It works OK. Nail triangular blocks to the forward edge of the strip so the clamps have a flat surface to bear against. Also, nail blocks on the aft side of the strip to prevent the ribs from sliding when the clamps are tightened. After this cures, I'll glue on the tip bow, and the fin will be ready to come out of the jig.
The main fin spar is now bolted to the stabilizer, and on the table with the forward parts on top. I leveled everything with the water level and checked it with the laser. While attempting to line up the forward fin spar, I discovered that the forward stabilizer spar was slightly misaligned. This error gets magnified at the stabilizer tips. It appeared that the left & right forward tips were misaligned by 1/2", which I wasn't willing to ignore. The Falco has none too big an elevator trim tab, and if the stabilizer is too far off, it will not be possible to always trim the airplane. On Alfred's advice, I took everything apart and measured the deviation of the centerline forward edge of the stabilizer from it's desired plane at each of the rib stations. The ribs near the center were within 1 mm, but the left tip was 5 mm up, the right tip was 6 mm down. So yes, the tips are different by 1/2", but the errors are really half that, and offset each other. In cases like this, it is possible to fair the surface with microballons to save the day, but we decided that wasn't necessary in this case.
So, now the spars are back together, and I have the alignment I need. It took about 2 days to glue in these 2 ribs, but it's important to get them right, because they determine the position of all the other ribs and of the leading edge. There will be a ground-adjustable rudder trim tab, but everything works better if the fin alignment is correct.
In the upper right hand corner of the rib that shows in the photo, you may be able to see a small hole. This is for a coaxial cable that leads to the communications antenna that will be installed in the fin.