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.









Instrument panel, canopy and tail fairing

all of my parts have come back from paint. In the time I was waiting for them, I finished calibrating the fuel tank gauge and tested out all of the instrument. I laid out a wiring schematic and I found a 12 pin power cable plug/socket combination that will serve as a quick disconnect between the fuselage and the Canopy. I want to be able to quickly remove the canopy because I will be hanging the robin from the rafters of my friends hanger. Under me will be 4 sailplanes.  
canopy Frame and Yarmulke

The fwd hinge of the canopy is actually an open hook. The canopy will have to be rotated beyond 90 degrees to release it. there will be two side latches that have yet to be fabricated, that lock the canopy down. The next job I have to work on is modifying the instrument panel bulkhead to add the knee relief we saw that I needed when my friend Mike was sitting in it.








Instrument Panel
Its pretty obvious in this view the modification that needs to be done to the panel Bulkhead. Beneath the canopy is a horizontal foam and glass shear panel. this too will be cut back to the intermediate foam rib shown in the previous picture. The instruments for the first flight will be a combination  CHT/EGT temp gauge, fuel gauge, inclinometer, airspeed and AGL altimeter. Later I will install an Audio Vario in the upper left. The lower middle will be used for a Velcro mount of my I Phone and  Hand held VHF radio.  





Rear fairing being bonded in place
After I trimmed the rear fairing to accommodate the elevator travel, I realized the fairing would be quite narrow and prone to damage if the whole fairing was left on the Horizontal. S i carefully cut the fairing in two and waxed the inside of the lower fairing. I then set the upper and lower fairing back into the mold and laid up a flange that is bonded to the upper fairing only. This will make a nice clean break and keep the fairing halves bonded to their mating structure.




Vert Fin tip cap

pretty self explanatory!!!
















Rudder Tip cap
Same with the rudder, looks like my thumb was covering the lens of my I-phone.















In addition to working on the previous components, I cleaned the Shop and re arranged the equipment to clear the wing tips. The only problem is when i reinstall the wings, I cannot get around in the shop. So I have decided to construct a center set of saw horses to elevate the fuselage 3 feet, I will also build two supports for the wings. I am not very happy with my wing attach design, because I will be redesigning the wings to reduce weight, I have also decided to make a fixed center section and have an external joint. The new design will allow for rapid installation of the wings and automatic disconnect for the ailerons.
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