RB Aero Building Blog

Week ending May 26, 2012

2012-05-26T17:38:07Z

This week ended with more work being done on the fuselage. We trimmed the bevels that we made on the aft end of the main fuselage. We also continued to work on the area on the inside of the main fuselage where the spar goes through the skin and where the main landing gear will be attached. Chuck drilled and tapped brake lines in each main gear. Next week we will continue to add extra glass to the spar and landing gear mounting area and, hopefully, attach the landing gear brackets! Here are pictures from yesterday:

Here is a view of the hanger showing large pieces of our airplane. The wings are on the left and the fuselage halves are on the right. The aft fuselage is sitting on the work table towards the back while the main fuselage is on it's right side sitting on sawhorses. The curved sills, between the seat back and the instrument panel were given extra unidirectional glass this week to make them extra stiff.

This view is of the right inside skin where the main spar intersects. I will be adding a little spacer in the corner area.

Here is one spacer (1/4" last-a-foam with 1 ply bi-directional glass on each side) cut to fit. Next step will be to "flox" into place.

Here is the spacer on the opposite (port) side, floxed in place. I have added a single ply of fiberglass cloth which goes over the inside spar cap, spacer and bottom skin.

Here are the main landing gear mounting brackets with their clamps bolted on. The steel mounting brackets will get bolted to the inside of the fuselage and the landing gear legs will get clamped in place.

Houston, we have separation!

2012-05-24T15:08:52Z

Well, it was just a couple of weeks ago that we attached the aft lower fuselage to the main fuselage and yesterday we cut them apart! However, in the meantime we made the mounting plates and the strong pads that they bolt to. We can now re-attach the two halves whenever we want to. Below are "before" and "after" pictures.

The joined fuselage's aft portion is sitting on the edge of our work table. The main fuselage is to the right and is supported by a sawhorse (not shown). The light areas are where last-a-foam panels are embedded between the inner and outer fiberglass layers (these add stiffness to the fuselage). The dark green band between the front and back fuselage sections is the front edge of the aft fuselage. We have added extra glass to stiffen this area. In addition, the little rectangle with 3 holes in it, sticking out to the right is an extra thick pad where a fuselage attachment tab will be bolted.

We have cut apart the two fuselage halves. Note that we cut the pad in half as well. We will bolt the the fuselage attachment tab onto that side with two bolts. Then when we are ready to re-attach the aft fuselage, we will screw it on by putting a machine screw through the aft skin and into a hole on the attachment tab.

After separating the two fuselage halves, we cut a 45 degree bevel on the main fuselage's back edge and sealed the edge with flox and fiberglass. This is called a "flox corner" or "flox edge".

In this picture, the main fuselage is sitting right-side-up and we are looking at the bottom port-side corner. The glass and foam has been cut back at 45 degrees to form a bevel and the foam has been cleaned away from the edges of the glass with a Dremel wire wheel. Next we will wet the glass and foam with resin and then cover with a mixture of cotton fiber and resin (flox) followed by two layers of fiberglass (see the picture below).

Chuck is adding two plys of fiberglass over the beveled and floxed area. Once the resin cures, we will trim off the excess glass and we will have a nice strong beveled edge.

The last thing we did today was the addition of 3 layers of unidirectional (UNI) glass on the inside and bottom of the sill, and inside surface of the fuselage side, between the seatback bulkhead and the instrument panel. This gives that area extra compression strength. I don't have a picture of this yet, but will post one tomorrow.

More Fuselage Activity

2012-05-22T16:39:01Z

We are continuing to make steady progress on the airplane. Last week we attached the center spar to the main fuselage.

This is a picture of our fuselage siting upside-down. The spar
is seen protruding from the side of the fuselage.

Here the fuselage is shown right-side-up. We could not resist inserting the landing-
gear to see how cool it will look!

Here we have the main fuselage and the aft fuselage joined together and we are
test-fitting two bulkheads to their positions on the aft fuselage. The larger bulkhead
on the left is part of the main fuselage.

Yesterday, we fitted 8 of the 9 fuselage mounting tabs onto the fuselage. These aluminum tabs will eventually allow us to be able to attach and detach the aft fuselage from the rest of the airplane.

Over the next couple of weeks will will continue to work on the aft fuselage, adding the bulkheads and bonding the skins together. We will begin making the new horizontal stabilizer and new elevators in the next week or two as well. Here are some pictures of the mounting tabs:

This is a view looking at the area where the aft fuselage joins the main fuselage. The plane is laying on its side, so the bottom tab is actually on the port side and the one on the left of the photo is a bottom tab. We used some flox (cotton fiber mixed with epoxy resin) to "bed" the plate and then used bolts and nuts to tighten and hold the plates in position until the resin hardens. Eventually, we will remove the plates and then cut apart the aft fuselage and main fuselage. Then we will permanently re-attach the plates to the main fuselage with the two sets of bolts and nuts. More about this in future posts.

Here are two fuselage mounting tabs bolted into place on the top fuselage skins. The aft fuselage is on the left and on the right is the area that will eventually become part of the main fuselage (the turtle deck behind our seatbacks).

Fuselage Progress

2012-05-10T18:20:03Z

We linked the lower aft fuselage and the forward fuselage together last week. This week we are making the mounting pads and plates that will be used to hold them together and to take them apart for transport or to work on them.

Chuck standing behind the fuselage at Hanger 115. We set the vertical fin on the aft end of the fuselage because it looked much cooler that way! May 9, 2012.

Progress Report: August and September bulkhead and Wing test

2012-05-02T14:24:08Z

I just wanted to show some pictures of some of the activities leading up to the wing test in September. I will be following up with our more recent work on the forward fuselage.

Seatback Bulkhead (August 2011)

One important first step in assembling the main fuselage was to put together the seatback bulkhead.
Here we are putting "flox corners" and glassing the inside edges of the two cutouts on the seatback. We will have access to our luggage area through these two holes.

Here we are attaching the lower seatback bulkhead to the upper bulkhead (which was illustrated in the first image above). The seatback is angled back for comfort.

Here Chuck is trimming the fiberglass after it has cured.

Here is another view of the seatback bulkhead. Notice the small cutouts on the lower bulkhead to allow the elevator pushrods to pass through.

Besides the seatback bulkhead, we also worked on finishing the rest of the bulkheads that will be used in the forward fuselage.

Such as this one (Bulkhead128) which will be located a couple of feet behind the seatback bulkhead.

Here is the lower instrument panel bulkhead. It will be located ahead of the
seatback bulkhead (September 2011).

As mentioned in an earlier post, on September 19th we tested both wings and the center spar by placing 27 bags of concrete (1,620 lbs) on them to see if they would bend but not break. Great news, they both bent a little over 6 inches but they didn't break!

Next we begin building the forward fuselage!

Wings passed 4G test! September 19, 2011

2011-09-20T04:35:29Z

It has been a long time since I have posted an update on our project. In a nutshell, we assembled both wings, and have finished making all the bulkheads and the panels for the center console. Our next phase is to begin making the main fuselage. But first we needed to load-test both wings!!!

The tests were performed with the wings upside down and and 1620 pounds of concrete bags were laid down along the length of the wing.

First we built two support frames, one to hold down the center spar on one end and the other to support the opposite end. Next a wing was bolted to the end of the center main spar and the wing tip was supported by a jack on the other. We placed 27 bags of concrete, weighing 60 pounds each on a wing. After that we slowly lowered the jack until the wing tip was no longer supported. Both wings deflected down nearly 6 inches, but did not crack or break. They both passed the 4 G test!

Here are a couple of pictures from the test.

The two cars are holding down the far end of the center main spar.
This shows the right (starboard) wing, up-side-down with 11 bags
of concrete. 16 more bags to go!

The same wing now with all 27 bags of concrete. Chuck is measuring how far
the wing has deflected.

Here are some of our test observers (Gordon, Bob, Ed and Bruce). I am standing
in front and Chuck is on my left. Not shown is Walter and Renee (who
took the picture). To say that we were relieved is an understatement.

Now we are ready to begin building the fuselage.

Bottom Wing Skins Completed!

2010-07-26T15:10:00Z

We have completed the five bottom wing skins and are now ready to finish assembling the top wing skin mold's leading edge. Here is a picture of me (Darryl) standing in front of our hanger at Livermore Airport (LVK) and the 5 bottom wing skins laid out behind me.

You can begin to appreciate the size of the wing for our little airplane! Without the wingtips, the
wing is about 30 feet long.

This coming week Chuck and I will be finishing the top wing skin mold.

Three down and seven to go!

2010-06-25T18:24:00Z

We have just finished our third bottom wing skin! We are now able to make one part a week.

Here are our first bottom skins for our wings. This is the outside (or bottom) surface. There are two layers of fiberglass on the outside, next is a 1/4" last-a-foam layer, followed by a layer of fiberglass on the inside surface, for a total of 3 layers of glass. All three parts have been post cured at 130+ degrees for two hours.

Next week we will make bottom skin number 4, that will become the first outboard half of the outer wing. It will differ from the first three because it will have a removable inspection cover/window for to allow visual inspection and removal of the aileron belcrank and linkage. The following week we will make wing skin number 5 that is a mirror image of number 4. After that we will finish the top skin mold and begin to make the 5 top skins.

Plugs, molds and wing skins

2010-06-14T16:02:00Z

Our First Wing Skin!

The picture above shows the first of 10 wing skin parts we will be making in order to build our wings. Here is what went into making this part....

Plugs, molds and wing skins

Since October, we have been working on making molds for our wing skins. We decided to create a "plug" of the wing cross section and use that to make an upper and a lower wing skin mold. The plug is about 6 feet long and is a very accurate representation of our wing's airfoil. We got help from our fellow EAA 663 member Jack Burke and his homemade CNC machine. His machine accurately cut 8 ribs matching Chuck's design. In early October, about the time we moved into the new hanger, we glued together the ribs and spars to form the plug's skeleton.

Three views of the framework for the wing plug. The 8 ribs were cut on Jack Burke's CNC machine. We then glued and nailed wood spars onto the notches in the ribs. The plug is now ready for us to glue on a plywood skin. (October 19-21, 2009)

Next we glued a thin birch plywood skin over the framework. In order to get the plywood to bend around the leading edge without cracking, we soaked about 12 inches of the plywood in an ammonia and water mixture to soften the wood fibers. Other than a small mishap in which Darryl's wood, cardboard and polyethylene sheet trough decided to come apart, the set up worked pretty well.


Our makeshift water trough        Getting ready to glue the plywood onto the plug frame. (Oct. 22, 2009)
containing ammonia and water.
(Oct 21, 2009)

Part way there! (October 22, 2009).

The plug with top plywood skin drying with strap clamps keeping it on tight (October 22, 2009).

Bottom plywood skin glued in place (October 29, 2009).

Here is the plug after we have put a layer of
fiberglass over the plywood skin. February 2-10, 2010)

After fiberglassing the plywood skins on the plug, we found that the surface was not nearly as perfect as we had hoped! There were lots of peaks and valleys which we needed to fixed. We first tried a plaster-like product called "ProForm". We figured that it would be easy to apply and sand down. Unfortunately, the plaster did not stick to the fiberglass. When we started sanding, the plaster just chipped off. So we removed all of the ProForm and went to "plan B" which was to cover the entire plug with epoxy and glass microspheres (also known as "micro").

Chuck squeegeeing on ProForm plaster and Darryl inspecting the dried plaster (February 10-11, 2010).

Because of the cold weather and other outside activities (like the holidays and Darryl and Renee buying a new house) we did not accomplish a lot on the plug between November and February. We did, however make the seat back bulkhead for the fuselage (see below).

Seat back bulkhead, forward facing side.              Seat back bulkhead, aft facing side.

Completed seat back bulkhead with cutouts (November
24, 2009).

Completed seat back bulkhead with one luggage cover
in place (November 30, 2009).

Getting back to the wing skin plug, we spent most of the month of February coating the plug with micro and carefully sanding to get as smooth a surface as possible.

Here is the plug after we have covered it with a slurry of micro. We spay painted
the micro surface with green paint so that we could see where the low spots
were as we sanded it down. Note the 7 foot long aluminum extrusion that we
used to sand the surface.

We did several coats of micro, followed by a lot of sanding. After a few cycles of this, we got smarter and began to use bondo get the final low spots filled in. By the middle of March we were pretty happy with the overall shape of the plug, so we began applying a "high fill" primer on the surface and carefully sanded to get the final surface we wanted. This did this step several times for both the top and the bottom sides of the plug. Here is what the plug looked like at this stage:

Plug with surface primed and sanded (Mar 18, 2010).   Plug ready to be waxed (Mar 26, 2010).

Here is Chuck looking pretty pleased with the wing plug. We are
now ready to make the top and bottom molds for the wing skins
(March 29, 2010).

On March 29th, we made the bottom mold. First we clamped  a very straight piece of wood onto the leading edge of the plug. The wood allowed us to create a flange on the leading edge of the bottom mold. When we make the top wing skin mold we will make a matching flange on it so that the two skins will mate precisely when we put the wings together. I will go into this later on in more detail.

Wood strip clamped to the leading edge. This will create a flange on the mold.

In order to make the bottom wing skin mold, we started by covering the bottom surface of the plug with a gel coat layer, which is made up of resin, Cab-O-Sil (a powdered glass material) and pigment. The Cab-O-Sil makes the gel coat layer very stiff, so that it doesn't drip or flow. We let the gel coat cure for about 2.5 hours and then covered it with seven layers of fiberglass.

Chuck spreading the gel coat layer with a squegee (March 29, 2010).

Bottom wing skin mold after the seven layers of fiberglass had
been applied on top of the gel coat. Note that we used a straight
piece of wood to create a flange on the leading edge. The flange
will be important later on when we make the upper wing skin
mold March 29, 2010).

Here is a picture of the mold after it has been trimmed and placed
back onto the plug (March 31, 2010).

The next step took some thought on our part. Basically we needed to put a backing on the flange and also make sure that the flange edge had a clean and sharp corner with no gaps or pockets. To do this we attached the mold to the plug by inserting screws all around the side and back edges to make sure it would not shift. We then applied strips of fiberglass onto the back side of the leading edge flange.

Next we clamped the wood backing on top of the wet fiberglass and then filled in the gaps with a mixture of cotton fibers and resin (also known as flox)..

Wood backing clamped onto back of      Adding more flox to fill in the gaps on
flange.                                                 the wood backing.

Since the mold was still pretty flexible, the next step was to make it as rigid as possible. We did this by adding foam stiffeners going lengthwise and chordwise while the mold was still attached to the plug. We fiberglassed over the foam which resulted in a very stiff and inflexible mold. Here are a couple of pictures of this process:

At this point, we were able to start making the top wing skin mold. Basically, leaving the bottom wing skin mold attached to the plug, we turned over the plug and then fabricated the top wing skin mold the same way we did the bottom.

Here is a picture of the top wing skin mold. The leading edge is towards the
left and the trailing edge is on the right side of the photo. There is a flange
on the leading edge that was created by presence of the flange on the lower
wing skin mold which we left in place when we made the top mold. Notice the
bottom wing skin mold in the background (April 28, 2010).

After finishing the layup of the top skin mold. we removed both molds from the plug. We now concentrated on the finishing of the bottom wing skin mold. First we needed to attach a wood extension to the leading edge flange. This would allow the fiberglass of the leading edge to be supported. We would then trim most of that away. Here is what the extension looks like:

Here is the mold with the wooden extension screwed into place. The mold has been coated
with 3 layers of wax.

Before we tried to make our first lower wing skin, we made two test parts that were only 10" wide. From the tests, we concluded that we would do the skin in two separate vacuum bagged layups. The first would consist of the two outer layers of fiberglass and the 1/4 foam core. After curing, we would then do a second layup in which we apply the single inside layer of glass. It would be a bit more work and would use more materials (peel-ply, release/cauls and polyester fiberfill bleeder), but would give us more consistant results.

Vacuum bagging the first bottom wing skin. This was actually the second lay-up
where we have applied the inside glass layer over the foam. The wet fiber glass
is then covered with Dacron polyester cloth (peel-ply) followed by perforated butcher
paper ("release/caul"). Polyester fiberfill ("bleeder") is then added on top in order to
absorb the excess resin. The entire mold was then enclosed in a polyethylene bag
and vacuum applied. You can see some of the resin being squeesed out along the
edge nearest you in this picture.

The first look at our wing skin! The release/caul and polyester fiberfill bleeder have been
peeled back to expose the peel-ply and inner skin. The peel-ply is fairly easy to remove
leaving a nice clean surface which is ready to be bonded to the ribs and spars (June 8, 2010).

Here is the first lower wing skin sitting on its mold. It is starting to look like a wing!
(June 8, 2010)

Back to airplane building in our new location

2009-11-18T14:33:00Z

All moved into the Hangar and building our airplane!
Since the mid-October we have been in our new Hanger at Livermore Airport (KLVK). Our first order of business was to get everything stowed away and organized. Here is a picture of our hanger now that we are all moved in.

Our hanger is located on the extreme northeast corner of the airport. Right
now it is pretty noisy since there is a lot of construction going on with the
building of a new freeway on ramp for Hwy 84!

As you can see above, we have done a pretty good job of filling the hanger. It is hard to believe that most of that stuff was in my garage. The big work table is set up on the left side of the picture just behind the Harley. The hangar came with a nice loft which we are using to store our completed parts, foam blocks and molds.

Now we are working on making the wings. We completed the main wing spars earlier this year (see the July 31st entry below) and last month our friend and fellow EAA 663 member Jack Burke used his home made computer controlled mill to cut out a bunch of wooden ribs for making a wing section plug. Chuck designed the parts and sent the drawing files to Jack. He then used the drawings to program his mill. Here is a picture of the mill in action:
(need pic of mill IMG_4774)

Within a day or two of moving in we got to work gluing the plug's ribs and longerons together.

The plug is glued together and ready to have thin plywood skins added.

On October 22 we took the plywood skin for the top surface and soaked a 10" wide leading edge in water and ammonia to make it soft enough to bend around the leading edge. Other than a small mishap where the trough had a major leak, the technique worked out pretty well. Here is a picture of the plywood soaking in the water/ammonia trough.

Top plywood skin for the plug soaking overnight in water and ammonia to
make it bend better for the leading edge.

The next day we bonded the top plywood skin to the plug frame.

Straps holding wooden top skin in place while the epoxy sets.

We discovered afterward that we might have been better off if we had done the top skin in two stages. Trying to bend the leading edge and entire top surface was a handful, and there were some small bulges in the top surface. We ended up making two length-wise cuts in the top skin so that we could re glue the high spots.

Reworking the top skin. We turned the plug over and added 3/4 x 3/4 strips
of wood to the underside skin and clamped the skin down well.

By November 12th we had finished reworking and sanding the top skin and were now ready to glue on the bottom skin.

The plug is upside-down with the bottom skin glued into place.

The next step on the plug will be to add one or two layers of fiberglass. We will need to sand the skin to a very smooth surface so that we can make molds for the top and bottom wing skins.

In the meantime, we fabricated the seatback bulkhead this week. Here are a couple of pictures of that assembly.

Seatback bulkhead foam. Two areas have been machined down and will
be where openings will be cut out for access to the luggage area.

The front surface had been wetted with resin and micro and the first layer
of bi-directional fiberglass is being applied.

The second layer of bi-directional fiberglass has been applied and squeegeed.

Sikorsky engine nacelles

2009-09-20T04:19:00Z

Our slight detour: more work on Walter Treadwell's Sikorsky S-38 project.

Last month we made some new parts for Walter Treadwell's Sikorsky S-38 amphibian project. As you may remember, we made four fuel tanks back in the beginning of the year. This time we made engine nacelles which form a streamlined area behind each radial engine. Walter provided us with a nacelle "plug" for us to make a mold. Since he has two engines, his project requires 4 nacelle halves. Chuck and I made a few minor modifications to his plug and made a trim fixture and a mold from it.

Here is a picture of the engine nacelle plug. This is formed into the shape
of the final part. The plug is used to make the mold for making more parts.

In order to make a mold from a plug, you first have to apply 3 or 4 layers of wax to its surface. I use Minwax, which is easy to apply and buff out by hand. After the wax has been buffed, a smooth and even coating of PVA (polyvinyl alcohol) is sprayed onto the plug surface. The PVA is a mold releasing agent, which makes it easier to remove the mold from the plug, after the part has fully cured.

While forming the mold off the plug , we learned how to make a "gel coat" surface. We made our own gel coat by mixing a type of glass powder called "cab-o-sil" into the epoxy resin. The resulting mixture makes a very thick slurry of resin which does not run or drip when applied to the plug. After the gel coat had a chance to "set up" and thicken for a couple of hours, we then began adding pieces of fiberglass cloth. We used quite a few layers and several different types of cloth that we had on hand so that a fairly thick and stiff mold was produced. After allowing it to completely cure, I was able to pop it off the plug fairly easily. Here is a picture of the new mold:

Brand new mold mounted on sawhorses. Note the smooth shiny gel coat
surface.

We also made a trimming fixture which was formed off the plug as well, but unlike the mold, we did not need to use a gel coat.

This is the trim fixture. As you may be able to see, it still needs to be trimmed.

As of the week ending Friday, September 18, we have completed 3 of the four nacelle halves. Two of them were trimmed and delivered to Walter. After test fitting he determined that the trim line needed to moved 1/2 to 5/8" on each longitudinal edge. Because of this 3 more nacelle halves were made (total of 6 parts made).

Here is one of the 6 completed nacelle halves.

Here is a picture of one nacelle being test fitted onto the Sikorsky.

On October 12th, the last part was molded for the Sikorsky engine nacelles. We are now ready to move to the new hanger and start working on our project 100 percent!

Big News!

2009-09-20T00:38:00Z

RB Aero is moving!

After 3 and a half years on a waiting list, we have a hangar! We will begin
renting a hangar at Livermore Airport on September 26th. Needless to say,
both Chuck and I are pretty excited.

Future home of RB Aero!

This represents a new stage for us and the timing is pretty good. We are assembling
a 6 foot long wooden wing section which will serve as a "plug" for making the wing molds.

This 6 foot long wing section will be covered with a thin birch plywood skin. It will be
covered with a single layer of fiberglass and then finshed to mirror smoothness (well almost!).
This part will serve as a "plug" from which the top and bottom wing skin molds will be created.

My garage, "Center Street Hangar" was getting a bit tight since the parts we are now
making are getting bigger and pretty soon we were going to have to put the pieces
together. We figured that we could complete the wings in my garage, but after that we
were going to have problems. Now we will be able to make the wings and forward
fuselage in a real hanger.

Another advantage will be having the help and expertise from our hanger neighbors,
most of which are EAA 663 (Livermore's local Experimental Aircraft Association
chapter) members. So we think that the timing couldn't be much better!

New Introduction

2009-07-31T17:34:00Z

Chuck and Darryl's
Experimental
Aircraft Project

Welcome to RB Aero's blog. This project is a partnership
between two brothers: Chuck and Darryl Ray. We are
building a prototype composite airplane to meet the FAA's
Light Sport Aircraft specifications. Chuck has designed the
aircraft and the two of us are building it.

Here is what our design looks like (excuse the missing nose wheel
and right side landing gear!)

We hope that you will enjoy our building blog. Here is our most
recent update:

July 31, 2009

2009-07-31T08:30:00Z

Welcome back

July 31, 2009

Here is an update on our aircraft building project. I have been a bit delayed getting this report out because my hard drive on my laptop died last week. Luckily, a local computer tech was able to retrieve (I hope) all my files and pictures!

Flash! My new laptop arrived today! I will miss my trusty old Dell Latitude but it was over 10 years old and couldn't handle high speed internet very well. I am very relieved that I can now go online without using a dial-up modem.

So here is what has been happening:

I am happy to say that we have been very productive over the past few months. As of last week we have completed the 4 main wing spars for our project.

We made two outer main spars (one for the port wing and one for the starboard wing), and two center main spars. The reason we have two center main spars is because the two spars will be bonded together to make an extra strong double spar for mounting the two wings. These parts have been the most challenging and complex layups of our entire project.

Here is a diagram of what the main outer spar looks like. Note that it has a
"C" shape. The two bent sides facing away from you are the spar caps containing
carbon fiber pultrusions which make the spar extremely stiff and strong.

In this picture, you can see where the port main spar goes in the wing.

We had to make two molds to make these parts. One 12 foot mold was created for making the two outer main spars. This mold was made using two aluminum L-brackets for the sides (spar caps) mounted to a smooth fiberboard base. The mold, and the resulting outer spars are very straight. We used carbon fiber pultrusions in the spar caps to make the resulting spars very stiff and strong. Since the forces become less as you go out towards the wing tip, the carbon pultrusions were cut to various lengths so as to reduce the amount of carbon the farther out you go. Over 6 layers of glass cloth were used on the inner 1/3rd of each outer spar and 3 layers on the outer 2/3rds.

Here is a picture of the mold for the outer spars. Note the aluminum rails which
form the spar caps.

Here I am (Darryl) holding the first outer spar for the whole world to see. (No one noticed)

Here is a picture of the port and starboard spars on the living room floor.
This type of storage requires a very patient wife!

Next we made a mold for the two center main spars. The mold is curved so that the center spars would bend upwards at a three degree angle, producing dihedral wings. Putting dihedral into our wings makes the aircraft more stable. Because of the curve in these parts, we decided to bend and epoxy-coat our carbon pultrusions into bundles before doing the actual spar layup. We used a flat board and inserted nails to make a bend jig.

Here is a picture of the carbon pultrusion bundles in the bending jig.

Unlike the outer spars, the carbon pultrusions in the center spars run the full length of the parts.The top carbon pultrusions were about 1/2" shorter than the bottom ones however. The bundles turned out great, holding their shape and turning out to be very stiff. After fabricating the 4 bundles, we then used them to make the spar caps for the front and rear main spars. After trimming, Darryl cut out matching holes so that the aileron, elevator and flap linkages can pass through the spars.

Here is a picture of Chuck standing behind the two center main spars. Note the
upward curve which produces the 3 degree dihedral in the wings.

Finally, Chuck has been using a friend's mill to machine the aluminum brackets that will be used to attach the outer spars to the center spars. This will be the main point for attaching the wings to the airplane.

Here is Chuck at the mill machining a mounting bracket.

Well, that is a quick overview of our progress on the four main wing spars. We hope to make more wing parts in the next few months. I hope to be a bit more timely in my reports since things are beginning to move much more quickly now. Please feel free to comment on our blog.

July through December Project Update

2009-01-07T00:58:00Z

6 Month Overview
It has been over 6 months since I last updated the RB Aero blog. After giving an
advance composite workshop with Zeke Smith at the GoldenWest Fly-in (which
was in mid-June) progress on our project has been pretty slow. Chuck did a lot
of design and stress analysis work on the area of the fuselage where the wing
and landing gear are attached as well as on the engine mount. We also have
been working on some fuel tanks for another airplane builder in our Experimental
Aircraft Association Chapter group (EAA Chapter 663). In October, our nephew
Brian Ray paid us a visit. Now that the new year is here Chuck and I are both very
anxious to get going on our project.

Project highlights for the second half of 2008:

We did complete the fabrication of one important set of
parts after our GoldenWest trip: We made our two ailerons.
Chuck made a lot of progress in analysis and design
details for the engine mount, the nose gear and the
fuselage where the wing and main landing gear attach.
We have settled on a new design for our ruddar pedals.

Brian and Chuck standing in my garage, aka "Center Street Hangar".

Ailerons
In the last week of June we cut out the two aileron foam cores. There is something very
satisfying in a creating a completed core out of a block of foam in less than one minute!
Below is a series of images documenting the use of the large hot wire tool to cut out
one of the ailerons:

In the series of photos above, Chuck (in the background) and Darryl (in the foreground)
work together to cut the foam with a hot wire tool. Note that the wire follows a white
template that determines the shape of the part. Once we have cut all around the template,
we can slide out the completed core (last large image).

We took the month of July off, but got back to work finishing the ailerons in August. Here are
some pictures of the ailerons being built:

We used the Dremel tool to inlet areas where each backing plate will go. Next we used
5-minute epoxy to attach the two ailerons to the sides of our work table. We embedded
the long steel rod counterweights to each leading edge using microspheres and epoxy
("micro"). We also embedded the 6 backing plates.

First layer applied to the lower surface of starboard aileron. The fiberglass cloth started from
the trailing edge, around and over the counter weights,leading edge and ending about 1 inch
past the hinge backing plates on the top surface.

Starboard and port ailerons looking at the inboard ends.

Rudder Pedal Design Change
One day in early August we were visiting another builder's hanger and liked the way his rudder pedals were designed. Chuck realized that it was a better configuration than he had been planning so he went back home and redesigned our pedals. Here are before and after views.

OLD DESIGN NEW DESIGN

With the old design on the left, the assembly is mounted to the floor while the new design on the right has the pedal assembly hanging down from the side. This new design is lighter and can handle the forces better.

Engine Mount and Nose Gear
Chuck has worked on the details for our engine mount as well as a new design for the nose gear. Here is a view of the front fuselage showing how the nose gear and engine mount attach to the firewall:

On the left is the nose gear which will mount directly onto the firewall. The yellow tubing in a
star-like pattern is the new engine mount.

Stress Analysis of Fuselage where Landing Gear and Wing Mount.
As I mentioned before, Chuck has also been working on the design and stresses of the area where the wing and main gear attach to the fuselage. This has to be the strongest part of the aircraft because some pretty strong forces interact here.

This is an example of what one of Chuck's stress analysis or finite element analysis (F.E.A.) outputs look like. This image is a cutaway view from the right rear looking forward towards the pilot's seatback. The reddish areas are zones of the higher stress. From this type of analysis, Chuck was able to modify the design to reduce the stresses on the fuselage to acceptable levels.

Sikorsky S-38 Fuel Tanks
Chuck and I volunteered to help out another EAA Chapter 663 builder on his project. We fabricated 3 fuel tanks for Walter Treadwell's Sikorsky S-38 flying boat project.

This is a painting of a Sikorsky S-38 flying boat as it would look in the late 1930s. The project that we are building the fuel tanks for is a 65% scale replica. It will be a two seat aircraft powered by two 150 horsepower radial engines. We began work on the Sikorsky fuel tanks in September. First off we needed to make some modifications to the mold for the lower tank half. The main modification was to improve the draft of the lower mold's short ends. We did this to make it easier to pull the cured part out of the mold.

Adding inserts to the ends of the mold. In the first image, the inserts are in foreground and mold in the back. The second picture shows Chuck fitting one foam insert in preparation for bonding and covering with fiberglass.

The two foam inserts were bonded into place and covered with a layer of fiberglass. After curing, the inside surface of the mold was sanded smooth. We finally made our first tank-half on October 2nd. We waxed the inside of the mold first and then sprayed on a good coat of mold-release. Next we applied 4 layers of fiberglass to the mold and finished by vacuum bagging the part.

Vacuum bagging our first tank half.

After fully curing the parts, we removed the mold from the vacuum bag and peeled off the release-caul and bleeder. With a bit of effort we were able to pull the part out of the mold.

Our first fuel tank half!

By the end of the second week in November, We finished making the 6 fuel tank halves.

This picture shows the three pairs of fuel tank halves sitting on a work table.

There is still more work to be done on the fuel tanks. We will need to trim them, add internal baffle/stiffeners, add vents and fuel line connectors, and last but not least, bond the two halves together. We hope to accomplish these tasks before the end of January. (Famous last words!).

For those who want to see what we accomplished each week, below is my weekly summary:

Week ending Friday, January 2, 2009
Chuck came over this past Wednesday. We worked a bit on the Sikorsky fuel tanks. We also discussed our game plan for the next couple of weeks. We are ready to really make progress in 2009!

Week ending Friday, December 26, 2008
No physical work performed on the project this week.

Week ending Friday, December 19, 2008
No physical work performed on the project this week.

Week ending Friday, December 12, 2008
On Saturday the 6th, Darryl cut out the fuel tank rib/baffles. Began to dremel bevels in the foam. Next step is to put dry micro in the scalloped cutouts.

Week ending Friday, December 5, 2008
No physical work performed on the project this week.

Week ending, Friday, November 28, 2008
Walter had given us the internal ribs/baffles to go inside the fuel tanks. Most of the parts had not been cut out and needed to be glassed on one side. Darryl did a vacuum bag layup to apply glass to the blank part.

Week ending Friday, November 21, 2008
Did not get together to work on project. Chuck trying to finish Jack Burke' engine mount FEA. Chuck updated our schedule. If we work like mad, we might start flight test in mid 2010.

Week ending Friday, November 14, 2008
On Tuesday Darryl cut glass and prepped for making 2 top fuel tank halves. Wednesday, Chuck came over and we made top half number 2. The next morning we molded the last top half. We now have finished forming the parts for 3 Sikorsky fuel tanks! Chuck trimmed one pair to the proper dimensions.

Week ending Friday, November 7, 2008
Did not get together to work on project. Chuck began to revisit the wing spar design. We are approaching the point when we will begin making the wing spars and need to finalize the spar/fuselage mounting, landing gear mounting, flap and aileron actuation designs.

Week ending Friday October 31, 2008
Sanded and prepped the top mold. I ended up grinding out a air void in one corner and filling it with micro. On Thursday, we molded our first top part. Chuck studying our design's expected electrical demands. Day VFR --4.7amps, Night VFR --7.0 amp with 13.75 when landing lights on (not use often). Chuck is thinking that we will use an Odyssey 680 battery which weighs 15.4 lbs, with day VFR could run 3 hours and night VFR for 2 hours without a generator. That should give a reasonable safety margin if lost the generator.

Week ending Friday October 24, 2008
On Thursday we molded our 3rd (and last) bottom fuel tank part. Chuck continued on nose gear design. Did weight comparison of several design concepts. The Zenith design (mounted to firewall) with shock cord looks promising with a 6 lbs savings over our original design.

Week ending Friday October 17, 2008
Saturday (October 11) Chuck and I flew N9396Hotel Cessna 172 to Cloverdale for the Zenith open house. Bruce Cruishank and his wife were there, and Bob Farnam flew in with his wife as well. Great flight going and returning. We were both glad that we practiced the crosswind takeoffs and landings the day before. Chuck had cataract surgery this week so we did not get together. Chuck worked on nose gear design.

Week ending Friday October 10, 2008
Tuesday Chuck was here. We went to Livermore airport to show Walter our first part. On Wednesday we prepped and molded our second part. Another success! Friday Chuck and I rented Niner six Hotel and did some touch & gos at Byron and Livermore. Since the weather report was for gusty winds both today and tomorrow we wanted to get some cross wind practice for our flight up to Cloverdale. It was fun and we both felt much more comfortable after the practice.

Week ending Friday October 3, 2008
On Saturday Chuck and I went to the EAA663 barbecue at the Livermore airport. Earlier in the day we picked up two compressors and a paint sprayer from Ken Coe. Ken gave us one of the compressors which was an old one that he had found while "dumpster diving" at the airport. Ken says he has found a lot of great stuff that way! While the tank had a leak, the compressor worked great. We will probably buy a new tank from Granger, but with a free compressor we got a great deal.

On Thursday, Chuck measured the engine to document it so that he can design the engine mount. We filled some depressions in the lower mold as well as the cut line with micro and used a hot box to cure. On Friday we prepared and vacuum bagged the first part. Came out great.

Week ending Friday September 26, 2008
Went to Livermore airport open house. Chuck volunteered to help out the EAA663 group and Darryl loaned them his portable awning. It was a fun event. Chuck worked on Jack Burke's engine mount FEA. Chuck started to worked on engine ring mount design.

Week ending, Friday September 19, 2008
Sanded entire lower mold surface and micro filled corners of new ends. Finished gluing and shaping foam between outside wooden mold stiffeners.

Week ending, Friday September 12, 2008
This week we modified both short ends of the lower mold to improve the draft of the mold sides. We used a pieces of blue foam, dry micro and one layer of glass.

Week ending, Friday September 6, 2008
We began working on a new project for another experimental aircraft project. Walter Treadwell is a member of our EAA group at Livermore Airport. He is building a 65% scale amphibian aircraft based on the Sikorsky S-38 flying boat originally built in 1928. See August 1st entry. We agreed to fabricate 3 fuel tanks for him. Walter already made the molds for the top and bottom halves of the fuel tank and had made one set earlier, but because of a epoxy allergy that he has developed, he was looking for someone else to make the rest of the tanks. We picked up Walter's molds and his first fuel tank halves. Chuck and I spent several hours inspecting the molds and discussing how we would tackle the project. We rounded and smoothed the edges and corners so that when we vacuum bagged the molds, we would not puncture the plastic bag. Darryl added foam to the outside of the lower mold.

Week ending, Friday August 29, 2008
Worked on Ailerons. Trimmed and sanded the trailing edges and cut them to their final (66.25") length.

Week ending, Friday August 22, 2008
in July, Chuck and I started to get back in the groove. Actually, Chuck has been pretty busy doing his stress analysis on the fuselage area where the wing spars and landing gear attach.

Week ending, Friday August 15, 2008
This week we made a lot of progress on the ailerons. On Monday, I worked on the aileron pushrod brackets. These two aluminum brackets will be riveted to the inboard end of each aileron.

Tuesday I worked on the 6 hinges for the ailerons.

Wednesday, Chuck came over and we worked on finishing the pushrod brackets and removing foam on the inboard ends of the ailerons where the brackets will be attached. We sanded all surfaces. We again attached the two ailerons to the side of the table. We took special care to make sure that the starboard aileron was straight as we attached it to the table with several dabs of 5-minute epoxy. The first layer we applied covered the lower surface from the trailing edge, around and over the counter weights, over the leading edge and ending about 1 inch past the hinge backing plates on the top surface.

Thursday morning, we came out early and inspected yesterday's work. Looked great. We removed the parts from the work table and laid them bottom-side-up on the table. We trimmed the trailing edges with the Fein Multitool. Next, we then painted the trough on the trailing edge with resin, then filled with a fairly dry micro. We finished this step at 10:00AM. We took a two hour break and then wrapped the ailerons in black polyethylene sheets and put in the sun to heat cure for one hour. This made the micro on the trailing edge hard enough to sand. We also carved off the excess foam from the top side of the tailing edge and also removed the peel ply so that we would get a good bond. Finally, we sanded the top foam surface flat.Next we added some dry micro to patch some of the areas where foam had been lost such as where the 5-minute epoxy was attached and also near the trim lines. After that, we put the ailerons in black bags to heat treat. After the micro was cured, we attached the ailerons to the table with 5-minute epoxy, and made sure that the starbord aileron had no twist. We applied one layer of fiberglass to the top surface. We were done by 7:30PM (about a 10 hour day!). We ended up doing 3 separate resin operations on the same part. This is the advantage of a long, warm summer day.

On Friday we removed the ailerons from the table and razor blade trimmed the trailing edges. The parts looked very nice. There were a few bubbles which we filled with dry micro. One bubble we pressed down with a weight. Again we heat treated the parts for about an hour and a half. We carved out the inside end of the starboard aileron and checked the fit of the pushrod brackets.

Week ending Friday, August 8, 2008
I worked alone this week. Sanded the aileron surfaces and cleaned up the micro residue. Also drilled out the holes on the backing plates so that we can add flox when we put the fiberglass skins on. Chuck has been working on finite element analysis and design modifications on the area where the landing gear, wing spars and fuselage all come together. He is considering the stresses created when the plane lands on both main gear as well as on only one wheel. It is the second case that puts the most strain on the aircraft. Chuck has had to make a few, relatively minor changes and now feels confident in the strength of the design.

Week ending Friday, August 1, 2008
This was the first time since we started our project that we did not attend Oshkosh. We were both pretty sad about it, but we both agreed that we couldn't afford it this year. Tuesday, Chuck and I met with another experimental homebuilder, Walter Treadwell at his hanger at Livermore Airport. Walter is building a 55% scale replica based on the Sikorsly S-38 amphibian. Chuck and I have volunteered to make 3 fuel tanks for his project. He has already made the molds and fabricated one tank. We will vacuum bag the rest of the tanks. We are looking forward to using our vacuum bag skills again, our only concern is that this will take some time away from our project. One great benefit of visiting Walter's project was seeing his rudder pedals. It turns out that they are made by Van's for several of their aircraft including the RV-6. The best news is that we can buy them complete from Vans!The price is reasonable so we won't have to make our own.

On Wednesday we worked on the backing plates for the two ailerons. We used the dremel tool to inlet the areas where each backing plates will go. Next we used 5-minute epoxy to attach the two ailerons to the sides of our work table. We embeded the long steel rod counterweights to each leading edge using microspheres and epoxy ("micro"). We also embedded the 6 backing plates.

Week ending Friday July 25, 2008
No physical work performed on the project this week.

Week ending Friday, July 18, 2008
No physical work performed on the project this week.

Week ending Friday, July 11, 2008
Chuck and Sharon on vacation. No activity

Week ending Friday, July 4, 2008
No physical work performed on the project this week.

Week ending Friday, June 27, 2008
This week I did some practice tig welding steel. Also worked on the 8 number CS132 and the two CS135 elevator hinge brackets. Chuck and I cut out the two Ailerons using the hot wire. The starboard aileron foam core ended up with a twist. We will be able to staighten it out when we put the skins on.

Week ending Friday, June 20, 2008

2008-06-21T05:36:00Z

Chuck has been the busy one this week. He has been working out the details on all the metal parts needed to finish and mount the elevators to the horizontal stabilizer. Mechanically, this is our most complex assembly to date.

This figure shows the left (port) stabilizer on top with the two mounting brackets and the center bearing assembly in place. The parts are shown separate with arrows to give a clearer view. Finally, on the bottom are larger models so that you can get a better view of each part. A mounting bracket is on the left and the center bearing assembly is on the right.

Chuck also worked on a list of parts to order from Aircraft Spruce as well as finalizing the aileron design so that we can begin cutting them next week.

Week ending Friday, June 13, 2008

2008-06-21T00:30:00Z

Saturday and Sunday Chuck and I gave two advanced composite workshops with Zeke Smith at the Golden West Fly-in at Marysville Airport. Renee complained that the last blog entry did not show a very good picture of our tent, so here is a picture that shows it clearly!

Our tent is the small misshapened tent in the foreground. Obviously, we were more interested
in aircraft than tentcraft!

We also had time to look at airplanes! Below is a picture of Jack Burke's "GoldWing Canard" composite aircraft. It is a modified Kato Kit canard. Jack is a member of our local (Livermore, CA) EAA Chapter 663. He is currently working on a 65% scale P-51 Mustang. We really enjoyed having a chance to get to know him better.

Darryl standing next to Jack Burke's Kato Goldwing Canard at Marysville Airport. This is a single
place open-cockpit ultralight aircraft.

We also looked at some of the new sLSA aircraft. These are certified aircraft that meet the LSA rules. They are not homebuilts like our project, but are ready-to-fly aircraft. While there were 18 aircraft of this type available in February 2006, that number jumped to 36 in February of 2007 and 55 aircraft this past February! (Kitplanes Magazine Feb 2007 and Feb 2008). It will be interesting to see what will happen in the next few years with fuel prices and competition increasing.

Here is one of the very nice sLSAs we saw at the show. The Skyleader 500-LSA is a all-metal
aircraft made in the Czech Republic. It had several cool features. One that caught our eye
was the trailing edge step to assist getting into the airplane (see below).

A flip down wing step for getting onto the wing. Since it is hinged, when the aircraft is flying,
the step swings up horizontally, reducing air resistance. Very cool.

By the way, sLSA aircraft that resemble our design (2 seat side-by-side, enclosed cockpit, conventional looking and flying aircraft) cost from $80,000 to $120,000 to buy.That is one of the reasons we are building our own. We are hoping that our airplane will cost under (hopefully well under) $35,000. Only time will tell if we will meet this goal.

One fun thing about getting away from our project and getting exposed to a lot of interesting folks and aircraft are the ideas we get. One such idea was the wing step shown above. We have been thinking about a step for the wing for several years now. Originally we were planning to put a step attached to the fuselage just in front of the wing, but decided that it could cause the fuel tank to rip apart in an emergency landing...not a pleasant thought. For that reason, we decided to put the step behind the wing. That is until we saw the trailing edge hanging step on the Skyleader 500-LSA. Chuck did some quick calculations and decided that the trailing edge could be made plenty strong for attaching a step.

On top is our first version of our step where it is placed in front of the wing. Below that is our newest
(borrowed) step idea, with it hinged to the wing's trailing edge.

Another idea we have been kicking around for a year or so is whether or not we could sling some hammocks under our wings. One of our early concerns was that we would have to get in and out of our hammocks at the same time. If either one of us needed to get out during the night (a not unreasonable idea) would the airplane tip over? Well, luckily, Chuck determined that if Darryl got out of his hammock, Chuck's behind would not hit the ground! Chucked also looked at the shear stresses on the wing if a 200+ body was slung beneath it, and concluded that there was strength to spare. The only question remaining will be if there will be enough ground clearance under the wing to allow us to get comfy without touching the ground. There is still much more to consider, so stay tuned.

After we arrived home from Golden West, we did not do a lot more on the project. Between recovering from the trip and Chuck having cataract surgery on his right eye the following Tuesday, we took some much needed "R&R". Chuck's surgery went great; he was really amazed at the difference!

Week ending Friday June 6, 2008

2008-06-19T21:36:00Z

This week I made the cuts on the elevator for the hinge brackets, and then prepared for our composite workshop that we were performing at the GoldenWest Fly-in at the Marysville airport.

Here are the two elevators with cutouts where the hinge brackets will be attached.

Thursday, I loaded up the jeep with our vertical fin, rudder, an elevator and most of our gear for our composite workshop at the Golden West Fly-in at the Marysville airport. That evening I drove to Chuck's house so that we could get a early start on Friday.We got to Marysville around 1:00 in the afternoon and pitched our tent in the vendor campground area.

Our tent is on the far left and the airport tower is in the background.
If you look carefully you can see Darryl talking with Martin Hollmann.
Martin is another aircraft designer and builder. Chuck took a finite
element analysis (FEA) workshop from Martin in 2006.

Chuck applying flox to a demo part during our composite workshop.

Darryl looking on as Zeke Smith does his vacuum infusion demonstration.

We ended up doing about 6 hours of demonstration/workshops duing our two days at Golden West. As usual, we had a great time and got to talk to a number of aviation and aircraft homebuilding enthusiasts.We hope that the 20 or so participants of our workshops enjoyed the experience as much as we did.

Week ending Friday May 30, 2008

2008-06-04T19:57:00Z

The micro on the bottom trailing edge was well cured by Tuesday when I began removing the excess Styrofoam from the top trailing edge. Removing the foam exposed the peel ply (Dacron fabric that is used to create a good bonding surface on fiberglass once it is peeled off, hence the name "peel ply"). With lots of elbow grease, I was able to pull off the peel ply from the trailing edge. Next I used a large sanding block to remove and shape the top foam surface. The trick is to make sure that the airfoil is very flat with no dips or bumps. The two elevators looked terrific

Edge-on view of one elevator showing the trailing edge on the the right. The blue
Styrofoam on top will be removed, see next image.

This is the elevator after the excess Styrofoam and peelply have been removed.
This elevator needs a bit more sanding of the foam in order to be ready for the
next fiberglass layer.

Chuck was over on Wednesday. Before he arrived, I put both elevators under black plastic and set them out under the sun to cure for 2 hours. The temperature reached 113.4 degrees F. This really helps cure and stiffen the fiberglass.

Heat curing the parts using black polyethylene plastic and the sun. We call this our
"black bag cure" technique.

We used a combination of 5-minute epoxy and Bondo to glue the two elevators to the side of our worktable. This allowed us to have access to 3 sides of the parts. We cut out all the glass cloth we would need for surfacing the top surfaces and followed the same "prepreg sandwich technique" that we used last week on the lower surfaces. We began mixing resin 5:30 PM and finished the lay-up two hours later.

Thursday morning we attached the leading edges to the two elevators. These had been cut out from the original foam cores back on May 10th. We used a thick micro slurry to bond the leading edge onto the flat forward surface of the elevators. This area is technically a spar web, the "backbone" of the elevator, and very strong. We used cotton/resin flox to bond the inboard torque tube tunnel to the spar web in the same bonding operation.

Applying micro to elevator where leading edge will be attached.

Leading edge in place with weights to get good contact.

We let the resin cure for 3 hours, during which Chuck prepared fiberglass for the leading edge. Next Chuck began applying one and one half layers of fiberglass over the leading edges. The elevators were now fully covered and had their final shape. We were very pleased with the results. Chuck headed home.

Leading edges with fiberglass.

Friday, Darryl removed the elevators from the worktable. He spent nearly an hour removing duct tape and excess fiberglass from the two parts. The tailing edges were also smoothed using sandpaper. Once again the parts were put outside under black polyethylene sheeting and allowed to cure for 4 hours. This time the temperature reached 136.9 degrees! We got a really great cure on the parts.

Chief assisting in black bag curing the two elevators.

Later in the afternoon, Darryl cut out the first of three cutouts on the leading edge where one hinge bracket will go.

Week ending Friday, May 23, 2008

2008-05-22T23:25:43Z

This week we made great progress on our (second generation) elevators. As I mentioned before, we made the first set of elevators back in October, but discovered that not only were they very difficult to mount onto the horizontal stabilizer, but there was a problem with the leading edges bumping into the stabilizer when the elevators were deflected downward. We either had to build a new horizontal stabilizer, or redesign and make two new elevators. We chose to re-make the elevators. Although the new design is a bit more complex, it is easier to attach to the stabilizer and should function better than the first design.

This past Saturday, I filled the holes in the 6 aluminum backing plates with flox (epoxy resin with cotton fibers). The flox ensures that the backing plates are very firmly anchored to the foam and fiberglass skins of the elevators.

Backing plate with flox. The flox fills the holes in the plates and
helps anchor them to the foam.

It was not until Tuesday that I got back to work on the elevators. By then the flox was as hard a a rock. It took me a day's work to grind off the excess using a wire wheel on a dremmel tool. It was very time consuming but the results were worth it.

Chuck came over on Wednesday. I cut out the servo cover and cover backup plates out of aluminum sheet. I then drilled the screw holes in both parts to match. Next I positioned 8 nutplates under each hole on the backup plate and drilled holes for the rivets. Finally, I riveted each nutplate into place. I added beeswax to the nutplate holes and embedded the backup plate into the starboard elevator.

In the meantime Chuck cut out two foam pieces for mounting the tail light on the rudder (we made the rudder several weeks ago).

Two foam pieces will form the fairing for the tail light that will be
mounted on the rudder. I will go into more detail in a few weeks.

On Thursday we finished cleaning up the backup plates and then cut out the fiberglass for the top skins of the elevators. Next we vacuum the part to remove any dust .

Before we wet out the glass cloth, we painted resin onto the foam surface. Next we added micro and worked it well into the foam surface using a squeegee tool.

Chuck spreading a slurry of micro (glass microspheres and resin)
onto the surface of the foam. This ensures that the fiberglass
bonds really well to the foam.

Next we applied epoxy resin to the fiberglass cloth. We used the "prepreg sandwich technique" to wet out the cloth. This is a technique where we draw the exact final shape of the fiberglass on the bottom of a piece of polyethylene sheet. We then place a slightly oversized piece of fiberglass cloth on top of the polyethylene and fold the rest of the plastic over the fabric forming a "sandwich". The next step is to wet the fiberglass sandwich with epoxy resin. We do this by folding back the top sheet and then pouriing the resin on top of the fiberglass cloth. After re-folding the plastic back onto the cloth, we use squeegee tools to work the resin into the fiberglass. After the glass is throughly impregnated with the resin, we cut out the fiberglass sandwich along the lines drawn on the bottom sheet. We peel off one layer of the plastic, and apply the fiberglass and attached polyethylene backing layer to the elevator. Having a backing layer of polyethylene film makes it much easier to handle and position the epoxy empregnated fiberglass cloth. See the drawing below:

Here are two fiberglass sandwiches ready to for resin. The long
piece in the foreground will cover the entire length of an elevator.
The shorter piece in the background will cover only the inboard
half.

Next, we use the squeegee tool to press the glass tight against the foam. Once we have the glass positioned well, we can remove the plastic film. We spent 15 minutes with a paintbrush to get all the airbubbles worked out between the fiberglass and foam. We applied fiberglass to both elevator's upper skins.

Chuck cut out a thin piece of plywood to make a mounting plate for the servo. We painted one side with epoxy resin and embedded 4 screws to act as posts for the servo.

The servo is upsidedown on the bottom. Next is a layer of poly-
ethylene to protect the servo. Finally, a thin piece of plywood is
mounted to the servo using 4 screws. The wood is coated with
resin and flox (cotton fibers and resin) are covering the screwheads.

Friday, Darryl trimmed off the excess glass off the two elevators. He also filled the trailing edge trough with micro. The micro makes the trailing edge stiffer and stronger.


Micro slurry is applied to the trailing edge.    Trailing edge after micro has be smoothed
                                                                       into place.

That is a wrap for the week!