September “Shop Notes”
“EMG-6 Shop Notes” is a day-to-day accounting of what’s going on in the shop with the EMG-6 Electric Motor Glider.
September 29, 2015 Finish Covering of the Left Wing
The last step in the process for the finished tape will be to cover the rivets and the reinforcing tapes at each rib.
One of the inspection panels is located at the trailing edge near the wing tip.
And the second inspection panel will be located at the trailing edge just inboard of the wing strut attach fitting.
September 28, 2015 Covering the Wings
First step is to roll out the fabric to the length of the wing so that we are installing one complete piece per side.
Using the poly brush on a very large surface, such as the leading edge tube gives lots of adhesion.
We are cutting out around each and every fastener, because we are trying to maintain exact orientation for the hinges and the fittings
In this picture here you can see the bottom fabric has been installed completely.
The top fabric now installed and the edges overlapped.
The compound curves of the wing tip can be a little bit tricky and require a little bit of preheating to shrink the fabric in order to eliminate any wrinkles.
The new trailing edge design on the wingtip looks really good.
Should be considerably less drag them. The prototype aircraft.
Also the wingtip ribs look really good.
It’s surprising that the amount a sag in between each rib was slightly more than we had anticipated.
This is one of the reasons that we went with the NACA 23015, airfoil for the ribs rather than the NACA 23012
The outboard section of the wing has been slightly heated, where the inboard section has not yet been shrunk at all.
See a considerable difference between the shrunk in an shrunk sections of the wing.
Initial shrinking of the fabric in order to achieve a well distributed shrinkage.
The final step is to stabilize the fabric with the iron set at 350°F and go over all sections of the fabric one step at a time.
This is a little bit tedious with a very small iron like we have here. But we like to use the small monocoque iron that is used for model airplane covering systems because it has a very stable thermostat and can control the temperature very accurately during the heating and shrinking process.
The next step in the process is to begin the poly brush covering with a nice 2-3 inch wide brush maintaining very parallel strokes.
The covering with the brush actually takes about two hours to cover the whole wing.
In this picture here we can see the bottom side of the wing has been completely covered and Jason is now working on the top side.
Every detail where there is a cutout or an overlap receives extra reinforcement. In this case here, where there is a slight compound curve. It requires the use of a pink edge bias ply tape.
All of the bolt holes, Eye Bolts, fork bolts Get two additional reinforcement layers around the perimeter. This will allow for removal, or maintenance of these fasteners. Later on.
The next step is to install the reinforcing tape set each rib.
Remember that we predrilled each one of the ribs with a very specific spacing pattern.
We install the reinforcing tape which is 3/8 of an inch wide, and then we pierce the reinforcing tape and install a an aluminum pop rivet into each one of these locations.
With the reinforcing tape permanently installed on to the rib with an aluminum pop rivet it will provide greater adhesion of the fabric to the rib structure.
This is the equivalent of rib stitching. But goes much quicker.
More reinforcing tape’s around the hardware that sticks out of the structure.
We are almost finished with the basic covering of one wing, and we did all of that in a single day.
September 24, 2015 Prepping the Wings for Covering
The entire wing needs to be cleaned with acetone prior to covering. Any of the ink marks left on the tubing from the manufacturing process that identifies the type and material of tubing will bleed through the fabric.
After all of the ribs both top and bottom have been marked we will drill at a #30 hole For each one of the fabric rivets.September 23, 2015 Wing Holding Jigs Completed
The left wing is hanging on the fixture and we are almost ready to hang the right wing.
The balance of the wings are nearly perfect. Even without the holding clamps tightened the wings will hold position where we rotate them to.
The alignment tape from the tip to the pivot for the right-hand wing.
This is what balances the wing is properly positioning the fixture related to the center of gravity.
The right wing inboard fitting complete and ready for the pivot arm.
Pivot arm being tack welded in place and then double checked for alignment.
Both wings laid out on the rack in the horizontal position.
And the wings rotated to the vertical position.
Quick release pins for the wing attachment
September 21, 2015 Continued Progress on the Wing Holding Jigs
.The wingtip has a fixed location, which we can rotate the wing around which is located slightly forward of the center of gravity.
And since the wing will need to be balanced and have both pivot points at the root and the wingtip on the same axis we balanced the wing in the covering configuration and strong a blue tape line to use as an alignment guide during the installation of the inboard fixture axle.
The inboard axle mount is designed with a clamping mechanism that will allow us to position the wing in any position and then clamp it from rotating while were working on the wing.
In this picture Jason is welding. The inboard axle mount.
Positioning and tack welding. The inboard axle in alignment with our marking tape.
A look at the inboard mounting fixture.
The CNC machined out inboard axle mounting plate.
The mounting plate for the right side welded into position
Duplicating the fittings for the right Wing. We start with a stub and a centerline hold drilled through the stub to hold the wing spar in position
The same process happens for the rear spar.
With the wing mounted onto the fixtures the act sole sticking out provides enough clearance so that we can rotate the wing 360°.
A view of both fixtures and the wing in position.
We used Quick release pins on all the fittings to be able to easily remove the fixtures from the wings.
A homemade tea bolt provides tension adjustment on the axle. To give just the right amount of holding power while rotating the entire wing.
Forward spar fitting.
A couple of eyebolts provides for a rotating Pivoting action, allowing the wing to rotate.
An end view
With the second wing on the sawhorses we will soon have both wings on to the fabric covering fixtures and we can begin the process of prepping for covering.
September 20, 2015 Making the Wing Holding Jigs for Covering the Wings with Fabric
This week we are working on making up the fixtures that will be used to hold the wings in place during the covering process.
These fixtures will allow us to attach both left and right wings to these frames and rotate them 180° while we are working on them.
This will also be used as painting fixtures which will allow us to paint the entire wing with one coat having no overlaps and making it easy to spray both sides simultaneously.
The stands are being made out of scrap material that we have in the shop. I’m not sure if you can call 12$ a foot streamlined chrome Molly steel scrap material. But nonetheless it’s been in the shop for twenty years we might as well use it
This is a good opportunity for Jason to be able to practice his take welding skills.
Any practice at all is very valuable when it comes to developing technique.
We also had some spare adjustable feet that we installed on the new fixture to go along with the other fixture. This will allow us for precision leveling.
The stand on the left will be used for holding the wing tip and the stand on the right will be used for holding the wing root.
We still need to manufacture additional fittings to adapt to the wings.
September 19, 2015 Machine Shop Making Parts
September 15, 2015 Reno Air Races
September 14, 2015 EMG-6-250 Fun Flying September 2015 (Video)
September 13, 2015 EMG-6-250 Back in the Air For the first time since the Oshkosh Airshow.
If you click on the pictures below, they will turn into a full-size picture with a slideshow format.
September 11, 2015 New Video “Manufacturing the Wing Rib Attach Fittings”
September 10, 2015 New Video ” Manufacturing Wing Ribs”
September 9, 2015 Manufacturing of wing ribs
In this picture here we can see the socket being used to adjust the tension on the toggle clamp.
The next sequence of photos shows positioning the stock aluminum tube into the bending fixture of the lower wing rib bending jig and pulling smoothly down along the profile until the rib is bent to the proper contour.
Once the ribs have been bent they are positioned on to the profile template and marked for the cutting of the leading edge section so that the rib tube may properly position into the leading edge rib fitting.
In the next couple of days we should have a YouTube video on the complete process of manufacturing the ribs
September 8, 2015 Wing Rib Bending Jig’s
We have changed the rib mending jigs to include lightning holes and reduce the overall profile, which will lower the shipping weight and costs for those that would like to rent the rib bending jigs.
In addition to the availability of the 3 rib mending jigs. There are also on the builder database. DXF files which will allow you to send the files to your local cabinet shop and have them CNC manufactured.
In addition to that the PDF files on the drawings have enough data that it is pretty easy to lay out on a piece of MDF or plywood the dimensions and duplicate the jigs without much effort.
There is one bending jig for the upper profile rib.
And there is one bending jig for the lower profile rib.
In addition to the bending jig’s there is also a profile jig which is used for ensuring that the bent rib matches perfectly with the airfoil profile design for the airplane. This is a NACA 23015 airfoil.
The ribs can be placed directly on to the profile and after positioning the leading edge of each rib can be marked at the cut off position for the leading edge to ensure proper positioning. Once placed on to the aircraft.
In the picture. The right we are positioning a piece of cabinet grade plywood onto the CNC router and are preparing to cut out a set of 3 rib bending jig’s.
The 1st step of cutting any piece of plywood is that all of the small pieces have to be drilled and screwed in place so that they do not pop up during the cutting process and jam the CNC router.
After all of the holes have been drilled the next step is to cut out the internal lightning holes.
In this picture here we can see Jason capturing the center plugs and removing them and then simultaneously screwing down the perimeter of a few holes of each bending jig to hold it in place during the cutting of the outer profile.
With cabinet grade plywood and a fresh carbide router bit. There is virtually no sanding required of any of the jigs. Once they come off of the router.
This is the upper rib bending jig being cut out. The router cuts a depth of .26 inches each pass requiring 3 complete passes to cut out each part.
In the upper left side of the picture you see the original prototype bending fixtures made from MDF. The plywood with the lightning holes is nearly half the weight of the original MDF bending fixtures. The MDF was used on the prototypes because it took over a dozen tries to get the profile exactly perfect and we went through several sheets of MDF before we were able to come up with the bending profile that translated into the exact shape of the rib. Once the spring back was taken out of the aluminum tube.
September 7, 2015 Machining the forward and aft spar rib fittings
Once the profile of the fitting has been cut out the fitting then has to be re-positioned to bore out the socket on the end of the fitting that the one half inch diameter rib tube will be inserted into.
The builders database has to also be updated with the most current drawings.
In addition to the PDF files for the drawings of each component. There are also E drawings and DXF files that will allow the builder with the capability to manufacturer any of the components.
Although it’s not likely that a part like this would be undertaken for the few parts that a builder has to build himself.
The drawings provide lots of additional data should the builder have questions about how the part is to be manufactured or for inspection purposes.
September 5, 2015 Manufacturing of components for Fuselage Boom Assembly
September 2, 2015 Bending Fuselage Boom Assembly Components
Every bend on the fuselage boom assembly uses a 1/8 inch radius die for the bending. This radius works really well through most all of the material thicknesses up to about .063 when using 6061 T6.
September 1, 2015
Our machine shop is in full gear this week, producing parts. For the next couple of days. The milling machine will be producing the wing rib sockets for the dope and fabric covered wing version of the aircraft. We have over $300 worth of stock material and will run the milling machine until we have exhausted all of the stock. Surprisingly, that’s only enough material to produce 65 of the wing rib sockets.
Visit August 2015 Shop Notes
At this point in time. This is a pretty inefficient way for us to manufacture these components. However, until we are able to justify some other manufacturing techniques. This will have to do. This method does provide for very accurate components but the machining time is still a bit time-consuming. I have managed to rewrite the G code to machine with a single end mill So that the part can cut the entire profile without supervision. Cycle time for the profile cut out is now about 45 minutes.
