Mignet HM8 plans

For newcomers, a quick explanantion, the HM8 is not a Flying Flea. It is the first succesful homebuild of Henri Mignet. He wrote his first book about this small airplane. He flew it. And his experiences with this airplane inspired him to generate the Flying Flea concept.

Now i give the word to the planmaker and the builders.

If you speak French / Si tu parle Francais -> L' histoire de cette HM8

While travelling in France in June 2003 before the Montpezat gathering, we saw a beautiful HM-8 in Angers's museum and two more in Marennes inside Michel Monnereau’s hangar. My friends and I realize that, even though the HMS foundation in Brodhead had a wide range of Flying-Fleas from the 1934 HM-14 to the HM-293, 360, 1000 Balerit and to the latest Cordouan, there was nothing to evoke the years when Mignet still believed in the classical aircraft.

Some background for those readers who are not familiar with the history of the Flying Flea: Mignet, after designing and building 7 prototypes of various configurations had designed and flown a small monoseater, "une avionette", the HM-8. This occurred before he discovered the staggered-wing formula which should have revolutionized the aviation world, and hopefully one day will.

In 1929 he published a hand-written book describing his philosophy of flight and which contained the plans of the HM-8 with accurate building instructions.

About two hundred aviation fans, for which purchasing a factory-built airplane was financially impossible, built and flew their own HM-8. The machine flew quite well, but, as every classical aircraft, was not stall-proof. One day, Mignet crashed his HM-8, fortunately without injuring himself. This incident made him realize that the HM-8 would never be the totally safe airplane he was dreaming of and he burnt his own idol!

Henri Mignet went back to the drawing board, built a small wind tunnel, and carried out extensive research. 3 years later the first Flying Flea, a tailless plane using the slot effect between wings was flying. Consequently, the HM-8 is now almost forgotten, which is a pity; it was a very nice light plane, contemporary and comparable to the Heath Parasol and to the Pietenpol. It triggered the homebuilt movement in Europe in the late 20's and the early 30's.

The Mignet history would be incomplete without including the HM-8 and we were quite sorry not to have one to show to the many visitors of the HMS Pou collection.

Back home, I recall the woodworking workshops a few friends and I organized in Beloeil, near Montréal. A few years ago in André Létourneau's place and under his talented supervision, we built two ¾ scale Piper-Cubs. Would André agree to build a HM-8 replica for HMS?

I discussed of it with the HMS staff, who immediately accepted the idea and asked me to make the necessary contacts.

I got in touch with André Létourneau, who was very interested. He loves vintage aircraft and his own project, an amphibian Osprey II, was close to making its first flight after 14 years of meticulous construction.

I gave him a copy of the handwritten book "Comment j'ai construit mon avionette". I also gave one to Paul Fournier, another member of the Piper-Cub workshops team, an amateur builder and a talented draftsman who had already built a Zenair CH 250. We scheduled a meeting for the following Wednesday.

Both of them agreed to do the job, André Létourneau was going to do the woodworking and Paul Fournier was going to refresh and update the plans, build the ribs templates and fabricate the metal parts.

Why did we have to redraw the plans?

In the beginning, it was André Létourneau's request. He is from a family of organ builders and is accustomed to working with detailed plans that do not leave anything to the builder's initiative. The Osprey 2 and the Cubs he built also had detailed plans. The broad-brush approach Mignet had of building with long written explanations and artistic sketches, in his view, gave the builder too much initiative. He did not feel familiar enough with Mignet's spirit to interpret the drawings.

The second reason the plans were re-drawn was that, after long discussions with the HMS staff, we decided to build a HM-8 that could be displayed in flight. It is not really much more complicated to build a flying model than a static display replica; it is more rewarding for the builder and more interesting for the visitor. We have the examples of Old Rhinebeck in the United States and La-Ferté-Allais in France that clearly illustrate this point.

But, as we had to fly it, we had to make sure that the aircraft would be as safe as possible. Some details needed to be updated, which is not unusual for a 70-year-old design. The proper choice of wing airfoil is an important safety factor, and Henri Mignet left several possibilities to the builder.

Most of the original HM-8s had utilized sharp-nosed ribs, which is no longer considered an optimal solution. Mignet may have already had this feeling, as he mentions the possibility of using a round nose airfoil. We decided to use a Riblet airfoil, derived from a Göttingen airfoil contemporary to the HM-8 and very close to the airfoil that was used by Lérin, one of the most talented HM-8 builders. This airfoil is currently used on several light aircraft with excellent results.

Another example of the original design requiring updating: the ailerons. At the time, ailerons were very often activated by a single cable that was kept under tension by some kind of spring (Mignet speaks of a piece of saw blade). We could obviously not take the risk of using this method, even though it could work quite well. So we decided to use a very classical device with standard bellcranks. A differential control would eliminate the risk of adverse yaw.

Mignet also gave three possibilities of wing shapes, rectangular, rectangular with round tips and elliptic. He obviously had a preference for this third version, as most of the artistic drawings he made depicted elliptical wings. His preference pointed us the proper direction.

[Editor] There is more to the story. But you can read that in more detail and also the construction log in the first PDF in the list below.

HERE ARE THE PLANS (in french)

INTRODUCTION

WINGS

FUSELAGE