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.
