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EMG-6 "Shop Notes" December 2015

December “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.

December 18, 2015 TapMatic tapping head.

We have finally got the tapping process down to a science.
The final resolution to accomplishing the tapping process was the switch from a cutting system to a roll forming process.
The depth of the tapped hole had to be nearly .75 inches deep .
When cutting into soft material like 6061 T6 aluminum is very easy for the flutes of the To get completely plugged up and then increase the torque on the tap to the point where it snaps off.
We discovered this the hard way experimenting with multiple different tapping methods of using a cutting tap.
We managed to break 7 taps before we finally resolved the situation.
We even broke one of the roll form taps trying to tap a hole with the original drill size.

Using the roll form tap with a 1/4-20 Thread requires a #1 Drill bit size.
In this picture here you can see the TapMatic tapping head.
Once the process had been refined the process of tapping each one of the holes went fairly quickly.
I think we tapped nearly 150 holes in about an hour.

Final processing of tube connectors P/N’s  57-10-22 and 57-10-23

The final steps involved in machining the tube connectors is to drill the cross hole that will be used to connect the fittings  to the compression struts.
The fittings have to be attached to a sample spar tube fixture While simultaneously being placed in a drilling fixture and clamped to the indexing truck on the CNC mill.
The fixture contains a leveling bubble to ensure that the fitting is being drilled exactly perfect as it will be the alignment feature that keeps the rear and forward spars parallel.
The fitting is then drilled through just one side with a pilot drill and then moved to the drill press with A “V” block which is used to ream the pilot hole and drill through the adjacent side of the fitting to maintain perfect alignment.
During the setup process the parts are checked for alignment against the compression struts.
The fitting is then removed and rotated 180° and retested for alignment.
If there is any misalignment in the parts, rotating the part 180° will double the error and dramatically show the misalignment with the  fitting  and the compression strut.
In this picture here we can see the alignment with the compression strut in all three axes.
There are separate fixtures for the rear spar fittings as well as the front spar fittings.
Remember from previous posts that the front spar fittings are machined at a 3° angle to accommodate the sweep in the leading edge which creates the tapered wing feature on the EMG-6.
We will complete all of the forward spar fittings and then switch to the rear spar fittings.

57-10-22 Tube Connector 87 deg


December 17, 2015 Parts Manufacturing

More drawings being added to the builders database.

27-11-87 Rib #7

27-11-88 Rib #8

27-11-89 Rib #9

27-11-90 Rib #10

27-11-91 Rib #11

27-11-92 Rib #12

27-11-93 Rib #13

December 16, 2015 Keep Up-To-Date with the Progress Blog

December 15, 2015 Manufacturing Aileron Ribs

All of the ribs for both ailerons on the prototype aircraft have been cut on the CNC router and bent on the CNC press brake.

We even remembered to bend both a top and bottom rim for each location.

There is a little bit higher part count when building ailerons this way but the construction process. Sure is simple.

The ailerons on the prototype #2 glider are manufactured from .025″ .24 T3 aluminum. Normally the ribs would be manufactured from .040″ but because we are not incorporating the flapperons onto the new aircraft. We are able to cut the weight on the ribs almost in half.

What we have found is, that the landing distances, even without flaps are so short that we just don’t feel the flapperons are worth the weight penalty, the added cost, and complexity of adding that system in. The good news is that the flapperons system it is a design element that can be added later at any point in time. Flight testing without the flapperons feature and the new wing design should give us a little better idea whether or not we need the flapperons. On the prototype aircraft that has the flapperons on it now we have gone through extensive testing using full flaps, reflex, and every setting in between, and yet we still think that the performance of the aircraft without flaps is more than adequate. One of the other things that we are anticipating is that with the electric motor installation. Having the capability for regeneration in flight and even thrust reversing will significantly change the aircraft capabilities. If on approach you find yourself high simply placing the motor in the regeneration mode will add a substantial amount of drag and should the need arise for even more significant drag and a steeper approach thrust reversing in-flight should be a real possibility that should make for approaches that would normally be relegated to the STOL aircraft. I don’t know if you remember, but way back on test flight #3 . We had some good wing cam  footage that shows the landing distance without flaps. Scroll to the end of the video to watch the landing and you get a good idea of what I’m talking about.

Threading of Compression Strut Fittings

We received the ER collets and can now begin the process of using the Tapmatic tapping head.

We have a particularly unusual condition in that we are trying to tap an extremely deep hole. The extends nearly the entire length of the threaded portion of a conventional tap.

So far in the process of setting up the proper G code for the CNC milling machine. We have managed to screw up and break six’s so far.

We have been experimenting with different methods and adjustments on the tapping head but the trick of getting the  to The entire length of the fitting is quite the trick.

All of our research that we have done so far indicates that what were trying to accomplish is fairly difficult .

We may end up coming up with an alternative method of threading the fittings.

In this picture we have broken tap that is broken off nearly flush with the top of the fitting.

So far we been able to be fairly successful at tapping about 60% to 75% of the depth of the entire hole.

If we do that and hand The remaining 25%. It seems to work out pretty good.

We’ve also been experimenting with step tapping and that’s been working okay but it’s not the right way to be doing it.

Couple more fittings with broken taps in them.

A call to the manufacture of the tapping head tomorrow should resolve some of these issues and give us some ideas on better ways to accomplish this.

Were also to look at using the CNC lathe and using an internal threading bar. This also presents other difficulties as this is a pretty small hole to be doing that in.

December 14, 2015 Aileron Construction Continues

27-11-85 Rib #5

27-11-86 Rib #6

December 13, 2015 Construction of Ailerons Begin

The ailerons for the low drag version of the aircraft that were currently building in the shop right now, as prototype #2  has been completed for some time but we have not start construction.
The ailerons are interchangeable with the ultralight version of the aircraft.
The hinge locations are in the same location. The main spar and spar splice tube are the same components.
The primary difference is instead of using round tubes as ribs. We are using sheet metal bent and formed ribs and an aluminum trailing edge which reduces the drag of the aileron considerably.
This also allows for us to use this design with the Stitts poly fiber process. Rather than the Dacron covering system that we use on the ultralight version of the aircraft.

We mention it on every post that we do pretty much, but keep in mind that although these drawings are current and up-to-date When we post them, and you’re welcome to download and print them the only files that are kept up-to-date are the files that are on the builders database.

Where currently finishing up on many of the drawings for the ailerons.
The aileron construction consists of a main spar which transfers all the flight loads into a torsional load up to the Control horn on the inboard section of the aileron.
The spars manufactured from 1.5 x .035 wall, 6061 T6 aluminum tube

The aileron uses four eyebolt hinges along the length of the spar which attaches through the rear spar of the  wing.

The fork bolts that are used as the hinge on the rear spar of the wing that the ailerons are attached to penetrate’s the rear spar directly into the compression struts within the wings.

In the previous posts on this blog were the fittings that we have been machining.



27-11-13 TE Splice Outboard

Although there is the option to purchase all of the components on the aileron assembly Pre-manufactured and ready for assembly. We also try and provide as many drawings as possible so that an individual that wishes to reduce cost by manufacturing their own parts has as many options as possible.

On this drawing . There are templates located on the right side that can be used to manufacture the parts. Simply spray one side of the template with contact cement and stick the drawing directly onto the sheet-metal. Using a center punch Mark each one of the holes and drill with a #30 drill bit. And then using a metal cutting bandsaw cut out each part and use a disk Sander to finish the part to the final dimension.

In addition to the  option for a manually laying out the parts and building them off of the templates we have several other options available to the builder as well.

In the builders database are DXF files that can be used by the builder to have any of the parts CNC manufactured locally.

In addition to providing drawings With DXF files, JPEG files, and PDF files. We also have E drawings files which allows the builder to manipulate and control the part in a 3-D environment directly from their desktop.

27-11-12 TE Splice 1

27-11-81 Rib #1

27-11-82 Rib #2

27-11-83 Rib #3

27-11-84 Rib #4

December 12, 2015 Preparing for Part Tapping

We have just purchased a Tapmatic tapping head for the CNC Milling machine. This will allow us to tap multiple holes quickly and precisely.

The Tapmatic tapping head is rotated in in a clockwise direction threads itself down to the depth of the whole and then on the retracts cycle reverses the direction of the tapping spindle allowing the tapping to occur without having to reverse the spindle on the CNC mill.

We purchased the tapmatic Tapping head on eBay. It came without any collets and so we have a set of ER collets on order right now and we should begin to proceed with the tapping of the wing spar fittings. After we receive those.

December 10, 2015 Component Manufacturing Continues

Each airplane assembly requires 6 forward spar fittings and six rear spar fittings.

On this run we will make enough components for ten aircraft.

After the components come out of these CNC mill they have to be moved to the CNC lathe for the cutting of the spar saddle.

Each part that comes out of the CNC lathe that is required to be deburred by hand.

After the parts are de-burred the next step will be tapping the center hole which will attach the spar bolt into the fitting.

And the final step after that will be drilling the cross hole through the fitting which will attach the compression strut into the fitting.

In this picture we can see the cutting of the wing spar saddle for these forward spar fittings.

December 8, 2015 Production of Wing Components

We have been keeping all of the CNC machines working At a frenetic pace of the last couple of weeks.

We have been machining the wing spar attachment fittings for both the forward spar in the rear spar that fit into the compression struts that form the main structure for the wing.

In this picture here we are machining out the saddle portion that aligns with the forward spar on this particular fitting.

The forward spar attaches to the compression strut at a 3° angle, which is what makes up the taper in the wing. That means that this particular fitting. After coming out of the lathe needs to be machined at .010″ of an inch depth doing a 3-D machining process.

The chip conveyor has to be removed from the CNC lathe every day and cleaned.

This picture here is one eight hour. That generated this much  scrap material.

It takes quite a number of runs to get the machining process worked out just perfectly on the lathe.

The lathe has to be left unattended, which means that it cannot create any scrap turnings that wrap themselves around the part.

Typically, the process involves 10 to 20 different adjustments on each of the tool paths to finally come up with the final result.

This is a picture of the backside of the fitting that is counter bored to reduce weight.

The completed fitting as it comes out of the CNC machine showing the front of the fitting before the saddle is machined in place.

The center hole will be tapped to a 1/4-20 Thread to accept the Wing spar attach bolt.

These blanks will be used to manufacture both the forward spar and the rear spar attach fittings.

In this picture we see the fitting with the saddle machining completed and still awaiting the threading of the center hole.

Link to RND Electric Motor Installation

We have some new electric motor installation data that we can now share with you. Click on the link above to see some of the new motor mount design work that we are doing in preparation for installing the RND Electric motor.

December 4, 2015 Production of Rudder Components

Back in the shop today mass-producing s’more components for the rudder assembly.

We’ve commented before on the tediousness of having to screw each component on to the sacrificial table in order to hold it rigidly in place during the cutting process.

On today’s parts they are not terribly complex and they have no internal parts that pop out which makes it fairly easy to screw down with only about eight screws per part.

These will be the leading edge pieces for the rudder that we’ve seen in recent posts.

Once all of the parts have been cut from the sheet we have to bend each flange using the finger brake.

After the flanges that will function as the leading edge spar are finished being bent we bring them down to the CNC press brake where we will bend the leading edge radius.

This is a 1 inch radius.

Once we were finished with the prototype design We went back to the drawing board and added some additional tabs to both the leading edge and trailing edge of the sheet metal component to use as alignment fixtures during the bending process.

In this picture here you can see how we been the tabs down and they fit into the radiused bending fixture to hold them from moving right to left so that we get a very accurate band exactly down the center of the leading-edge.

Failing to get the parts exactly bent in the center  would cause a misalignment during the construction process.

You can see both the front and rear of the part with the tabs bent down for the alignment process prior to bending.

Because this material for the leading edge is manufactured from .016 2024 T3 manufacturing wooden bending dies is more than sufficient.

In addition to that the soft redwood male die does not leave any scratches during the bending process.

The design of the die is built so that it is much deeper than necessary in order to achieve as much bend as possible on the leading edge.

Once the part has been bent we can pop the female die down and slide it to the side of the male die to make it easier to remove the bent part.

Once we have the set up. It’s pretty easy to mass-produce the components identical to each other.

December 3, 2015 Updated drawings posted to the builders database.

Today we were able to post about sixty new drawings to the builders database that are either new or have been updated since the modification of the low drag rudder assembly leading edge.

We’ve also added more E drawings to the builders database for each one of the parts and subassemblies for the rudder and we are currently working on the revisions to the assembly manual.

In addition we have been working on the web store updating more of the parts inventory.

Keep in mind that the drawings that are posted on the progress blog here are not kept up to date and as revisions occur they normally occur on the builders database only.






December 2, 2015 Progress continues on the Low Drag Rudder Assembly

Jason has been building the rudder assembly SOLO. In this picture here he is covering the rudder with 1.6 ounce glider cloth.

The covering process progresses fairly quickly and usually within a single eight hour workday the rudder assembly can be covered and ready to start applying poly spray.

The aesthetics of the new rudder leading edge on the top are so much more appealing.

The leading edge has a nice rounded profile to it now as compared to the previous rudder assembly.

The new leading edge is a little bit cheaper to manufacture.

To little bit cheaper to ship as it now fits into a much smaller shipping box.

And it’s also quite a bit simpler to assemble.

In this picture here we can see how the leading edge profile looked on the previous version of the rudder assembly.

Not nearly as appealing as the new leading edge.

Reinforcing tapes are applied around all of the cutouts.

In this picture here. Jason is reinforcing the areas around the rudder hinge locations. There are three hinges with net plates riveted to the backside of the rudder spar assembly.

Instead of rib stitching on the EMG-6. All of the fabric is attached using a reinforcing tape  and aluminum pop rivets.

Are using an anodized aluminum 4-2 pop rivet for this Application.

Once the rivets have been placed over the reinforcing strips they will get another layer of reinforcing tape over the top of them.

The rest of the rudder gets reinforcing tape supplied. In addition to the reinforcing tapes. There are the rib reinforcing tapes with rivets installed over each one of the ribs and then an additional layer of reinforcing pink edge tape placed over each one of those locations.

With the new leading edge installed several of the holes that were used for the previous  full wrap leading edge are now used for fabric attachment rivets in the existing hole locations.

The temperature also warmed up enough today that we were able to apply a little bit of poly tone to the fuselage and vertical stabilizer assembly.

We have about 2 gallons of Daytona white left over from a previous project that were going to use up as a base coat for the Juno white.

The Daytona white is almost a yellow color, but it will provide a good base and reduce the total number of coats of the Juneau white that we will have to apply to the surfaces.

Were now starting to get enough poly tone onto the fabric that were starting to get a little bit of a gloss to the covering process.

Poly tone never does really shine like a polyurethane paint. But it’s extremely easy to repair and very user-friendly for the installation process.

Highly recommended unless you’re going to try and win a Lindy award at Oshkosh.

After spraying the fuselage boom vertical stabilizer outside we move it back inside to care for another twenty-four hours before we proceed to the next step.

In the next couple of days. It looks like the weather may hold out for a couple more coats of paint on both the wings and the fuselage boom assembly.


December 1, 2015 Manufacturing of control cable bushings.

Many of the components that we have been waiting to manufacturer that need turning are in production on a daily basis.
These cable bushings are designed to be used with a Nico press Cable fitting And are used in the rudder control system to attach the rudder cables to the rudder control horn’s and the rudder pedals themselves.
The biggest cost in manufacturing any of these parts is typically in the setup of the machine in order to be able to efficiently manufactured the parts.
Usually the best method is to make as many parts as you think you’re going to need for the next couple of years.
Is a close-up of the cable bushing very simple with a large radius on the inside used in conjunction with a 3/16 inch AN washer.
After the part comes out of the CNC machine the backside has a small amount of flashing that has to be sanded flush.
The parts go into the tumbler for about forty-eight hours to polish and deburr.
In this tumbler. We have a unique mix of walnut shells, popcorn, Dryer sheets, and polishing compound.


About Brian Carpenter (255 Articles)
CEO Rainbow Aviation / Adventure Aircraft

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