Welcome to my Robin Blog.

It was suggested to me that I start a Blog on my ultralight project the "Robin". I have been working on this project for 4 years. On one of my first days at Vought aircraft, a stress man and future friend named Kenny Andersen walked up to me and said, "Aren't you the Mark Calder that designed the Wren Ultralight" Why yes I am I said. "well what have you done lately?" That was the genesis of the Robin design. The first 2.5 have been spent in the design phase. Actual construction started 1.5 years ago and has actually progressed smoothly. There have been a number of changes from the onset, but for the most part it is following my original concept. I will eventually sell plans for the Robin and make available all molded parts, fittings and welded assemblies. The Robin is designed to FAA part 103 and as such requires no pilots license to fly, although I think its a good idea to actually learn how to fly!! The actual name "Robin" was my Daughter Jamie's idea, I asked her to name the design based on my "cute little bird" theme (Wren)



Every good aircraft design has a "Mission" in mind before the actual design is started. A good designer will refer back to this mission every time a design decision must be made. Good design after all is just a series of good design decisions. On my first Ultralight design the Wren, the mission was to design a high performance low powered aircraft. The reduction of drag was the prime concern. I had been flying powered Hang gliders prior to this and because of this experience, I placed a high priority on climb performance. While most designers chose bigger engines, I chose lower drag and high aspect ratio (low span loading) wings. The Wren could out climb conventional Ultralight with up to 65 hp. The Robin follows this philosophy, but tries to improve on the performance of the Wren. Ultralight are not built by "rich" people, they offer an inexpensive means to enjoy one of the greatest experiences of my life, low speed soaring and flying.



Design Concept



The cost of an aircraft is directly proportional to its weight. , if low drag can be achieved then lighter and cheaper engines can be used. The Robin expands on the design mission of the Wren by using a longer span (40') wing and using a low speed laminar flow airfoil, (Wortmann FX 170) The leading edge of the wing on the prototype is molded fiber glass. The spar has been placed at 33% of the wing chord because the chosen airfoil is laminar over the first 32%. The aft covering is light weight Dacron Fabric. The leading edge of this fabric is purposely pinked and placed at the 32% chord point to facilitate laminar transition and elimination of separation bubbles. The main difference between the original design of the Robin and the current final design is the elimination of the single mono wheel retractable landing gear. Part 103 does not allow for a retractable landing gear. Which is really unfortunate because I spent a long time designing a really neat mechanism!!

In the course of the 4 years I have worked on the Robin, the structural design concept has evolved radically. Originally I was going to draw on the design of the Wren and use essential the same construction concepts. The original design of the Wren was heavily influenced by my Friend Steve Wood's Sky Pup design. I lived in Wichita Kansas and worked at Cessna Aircraft along with Steve. I watched his progress on the Pup and was very impressed with his concepts. I adapted the concept of using Styrofoam sheeting as the shear panels for the fuselage and the wing ribs. I did not however use the foam for the shear webs of the wing as Steve did. I originally wanted to build the fuselage of the Robin in a similar manner. Weight and the desire to not use foam for the basic structure due to the danger of fuel leaking eventually drove me to a all wood fuselage design. The wings were designed to take advantage of the Graphlite carbon pultruded material pioneered for the experimental aircraft by Jim Marske. I was familiar with this product from my experience at Bell Helicopter where it was considered in the construction of the V-22 wing.









Progress, Squawk list burn down!!

My good friend Mike Lafrance and his wife Audrey flew out from San Diego for the week end. Mike and his Dad Neal are old friends from Wichita. I first met Neal at my first engineering job ever at Boeing Military Aircraft in Wichita Kansas. Neal was a designer on a very cool 'Black" program that eventually was made public and called "Pave Tiger" My involvement was packaging a tuned resonant exhaust chamber. Neal is one of the original founding members of the EAA, he was in the Wisconsin National Guard with Paul Poberezny when the idea for the Experimental Aviation Association was born. Neal has an award winning Wittman tailwind. he also built a Wittman V-Witt racer and actually raced against Steve Wittman in his final race. I owe Neal a great deal for all his support during the design and building of my old Wren and  years later when I had a chance to repay his kindness I volunteered to design and build his cowl on his beautiful Culver STF (Steel Tube Fuselage).
Mike and Neal Flying the Cadet

 His son Mike is also quite an accomplished pilot, home builder and restorer. His Luscombe 8A and his 11A sedan are works of art!! it was sure good of Mike to burn his vacation helping me work on the Robin. The following pictures are a collage of our progress. We completed the rig of the rudder pedals, completed the reattachment of the fuel tank fairing and started adding the tip caps of the vert fin and rudder.
Mike assures me he is a better Pilot with a few beers in him LOL!!
The Canopy in this picture is in the process of being finished for final paint.
I think Mike is drinking a Becks in this picture!!
This actually was a test , Mike is 6'3" and the tallest person to sit in the cockpit. The rudder pedals easily adjusted to him, but we found that two tunnels need to be built into the instrument panel to allow for knee clearance. The final panel will have a 'T" layout.
Adding the rudder cable anchors.
We learned a little lesson here, after the cables were rigged and the turnbuckles safety wired, I tried out the pedals and discovered they were canted too far aft. Mike came up with the solution of lengthening the Cable anchors. This had the effect of rotating the top of the pedal aft. The idea is that your heel needs to rest close to the pedal pivot.










FWD attach hinge
The FWD Fairing was reattached using two Piano hinges. The hinges easily withdraw and once done, the fairing readily releases.
The White material on the firewall is the Ceramic fiberfrax paper






Rear attach hinge
Later Mike added the plywood scallops. the purpose of these scallops is to smoothly transition the fabric from the stringers to the round bulkhead.





The happy builder!!
I told Mike I never get tired of staring at the cowl and fuselage lines. He told me that the reason I will finish this project. I'm not loosing interest as I go!!  Because I was travelling so much for the last 3 years, I never used my Vacation. I now "need" to take off the whole month of December or I will lose my vacation (Bummer!!)
I plan of doing all the cover and finish during that time. First flight will follow shortly afterward.






Me and Boo
We decided to do a little photo shoot. Good ole Boo, he is always near me wherever I go. Always protecting me from those nasty Sheep, Cows and flying frisbees!!







Soaring eye view
I learned a long time ago not to design for skinny people!!  They usually don't have any Money!! LOL!! The width across the shoulders bottom and is 24" Compare this to the 18" in 1-26 sailplane. The need for the instrument tunnels is apparent in this picture



Foot position on the rudder pedals
This is a very comfortable seat and rudder combination.  The pedals are mid adjustment for me, they still have one more inch to go for Mike in the FWD position and can still adjust rearward another 9 inches. This pedal adjust works beautifully.

Rudder Foam block
Work started on the Tip Caps for the Vertical Fin and Rudder. I am not making molds right away forr these parts. I am thinking I will need more Rudder. This is the technique a builder would use everywhere I have a compound molded part. The rudder was blocked in with some foam and then the edges were sanded parallel to the rudder surfaces.
Vert fin foam added

I traced the curve of the rudder foam and then cut out the vert fin foam and then bonded it to the vert fin. The foam was then sanded parallel to the vert fin surface. I then locked the rudder in place and started profiling the foam in the side view with the sanding block


Final profile
Scrap foam is used to sand the foam until the final finish is achieved. the rudder was separated and two layers of glass were added. a coat of micro balloon and epoxy was squeegeed onto the surface. This is very important, the foam is an open cell structure and if its not sealed, the resin laid on the glass will leech into the foam and cause a dry laminate.

I will follow up with the finished parts in the next entry








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