|
The Canadian HM-8 Replica Project by NEW PLANS FOR A VINTAGE
AIRCRAFT. 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 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. ANOTHER HM-8. Looking one day at the American Flying-Flea
web page, on the chapter dedicated to the HM-8, I was extremely surprised to
discover that the HM-8 drawings, which I had so often looked at without really
seeing them, were different from the classical HM-8 plans shown in Mignet's
book. I could not believe my eyes and enlarged the drawings. No confusion was
possible. The drawing figured the HM-8 D, a late and apparently unknown
version which was not shown on the book. I asked the web page editor where these
sketches (and the corresponding text) were coming from and he referred me to
one of the booklet published by Raymond Buckland, who for years worked
tirelessly to spread the good word about the Mignet formula. That gave me a
perfect opportunity to renew contact with Buck and I was pleased to hear that
he was OK and busier than ever with his writing. Buck informed me that he had
picked up the text and drawings from an old issue of the EAA Experimenter.
With his usual cheerful kindness, he mailed a copy to me. The text was a translation of a French
magazine dated 1932 "L'Almanach de l'Aviation" and it became more
and more obvious to me that the HM-8D was the missing link between the
conventional HM-8 and the first Flying-Flea, the triplane HM-11. The front
part of the fuselage and the shape of the wingtips were already very close to
what Mignet designed for the Pou-du-Ciel. I told Pierre Mignet about my conclusion and I
must say that he was very surprised, as he did not remember anything about a
last version of the HM-8. He suspected some kind of fraud and when I asked him
if we should build a replica of the HM-8D, he persuaded us not to do it. We
were quite sure that he was wrong and that the drawings were authentic, but,
after discussion, we decided that we could not go against his advice and we
started working on the classical HM-8, as per the book. Nevertheless, I continued my investigation and
called M. Ravel, the director of the http://perso.wanadoo.fr/aircollection/campagne_hm8.htm Daniel was very interested in my research. To the best of his recollection, there was no HM-8 D version. However, he started to pore through his documentation and finally unburied the original article published in the "Almanach de l'aviation". He selected the principal drawings and published them in our behalf in a new web page: http://perso.wanadoo.fr/aircollection/hm8d.htm That was the proof we needed to convince Pierre Mignet. I printed this page and mailed it to Pierre. His reply was immediate: "I was
wrong" he said, "the HM-8D really existed. I am now convinced and it
is the model you have to build!" Meanwhile, Daniel told me to get in
touch with another collector, Maurice Garsault, who confirmed the existence of
the HM-8D. He sent me more info, in particular an article by Henri Mignet in
the Magazine "Les Ailes" that pointed out that about 50 HM-8 D had
been built. By the way, he also gave me previously completely unknown
information about the first flights of the HM-11 Flying-Flea, opening new
horizons of wisdom. Unfortunately, for the HM-8D, it was too late
for us, as a part of the ribs of the standard HM-8 had already been built by
André Létourneau, and as Paul Fournier was already well advanced in the his
drawing efforts. We consoled ourselves by reasoning that the model we were
going to build was the one built most widely, nearly 200 aircraft. And the
elliptical wing is so beautiful! I have decided to build a scaled replica of
the model D, which does not deserve to sink into oblivion. My friend Chris
Frank, from (Page 2 of 14) |