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[Illustration: THE MOST IMPORTANT "TOOL" IN THE BUILDING OF MODEL
AEROPLANES.

[_Illustration by permission from_ MESSRS. A. GALLENKAMP & CO'S.
CHEMICAL CATALOGUE.]]




    THE THEORY AND PRACTICE
    OF
    MODEL AEROPLANING

    BY
    V.E. JOHNSON, M.A.

    AUTHOR OF
    'THE BEST SHAPE FOR AN AIRSHIP,' 'SOARING FLIGHT,'
    'HOW TO ADVANCE THE SCIENCE OF AERONAUTICS,'
    'HOW TO BUILD A MODEL AEROPLANE,' ETC.

    "Model Aeroplaning is an Art in itself"

    [Illustration]

    London
    E. & F.N. SPON, LTD., 57 HAYMARKET

    New York
    SPON & CHAMBERLAIN, 123 LIBERTY STREET

    1910




PREFACE


The object of this little book is not to describe how to construct
some particular kind of aeroplane; this has been done elsewhere: but
to narrate in plain language the general practice and principles of
model aeroplaning.

There is a _science_ of model aeroplaning--just as there is a science
of model yachting and model steam and electric traction, and an
endeavour is made in the following pages to do in some measure for
model aeroplanes what has already been done for model yachts and
locomotives. To achieve the best results, theory and practice must go
hand in hand.

From a series of carefully conducted experiments empirical formulae can
be obtained which, combined later with mathematical induction and
deduction, may lead, not only to a more accurate and generalized law
than that contained in the empirical formula, but to valuable
deductions of a totally new type, embodying some general law hitherto
quite unknown by experimentalists, which in its turn may serve as a
foundation or stepping stone for suggesting other experiments and
empirical formulae which may be of especial importance, to be treated
in _their_ turn like their predecessor. By "especial importance," I
mean not only to "model," but "Aeroplaning" generally.

As to the value of experiments on or with models with respect to
full-sized machines, fifteen years ago I held the opinion that they
were a very doubtful factor. I have since considerably modified that
view, and now consider that experiments with models--if properly
carried out, and given due, not _undue_, weight--both can and will be
of as much use to the science of Aeronautics as they have already
proved themselves to be in that of marine engineering.

The subject of model propellers and motors has been somewhat fully
dealt with, as but little has been published (in book form, at any
rate) on these all-important departments. On similar grounds the
reasons why and how a model aeroplane flies have been practically
omitted, because these have been dealt with more or less in every book
on heavier-than-air machines.

Great care has been exercised in the selection of matter, and in the
various facts stated herein; in most cases I have personally verified
them; great pains have also been exercised to exclude not only
misleading, but also doubtful matter. I have no personal axe to grind
whatever, nor am I connected either directly or indirectly with any
firm of aeroplane builders, model or otherwise.

The statements contained in these pages are absolutely free from bias
of any kind, and for them I am prepared to accept full responsibility.

I have to thank Messrs. A.W. GAMAGE (Holborn) for the use of various
model parts for testing purposes, and also for the use of various
electros from their modern Aviation Catalogue; also Messrs. T.W.K.
CLARKE & CO., of Kingston-on-Thames. For the further use of electros,
and for permission to reproduce illustrations which have previously
appeared in their papers, I must express my acknowledgment and thanks
to the publishers of the "Model Engineer," "Flight," and the "Aero."
Corrections and suggestions of any kind will be gratefully received,
and duly acknowledged.

    V.E. JOHNSON.




CONTENTS


    INTRODUCTION.
                                                                   PAGE

    Sec.Sec. 1-5. The two classes of models--First requisite of a model
    aeroplane. Sec. 6. An art in itself. Sec. 7. The leading principle      1


    CHAPTER I.

    THE QUESTION OF WEIGHT.

    Sec.Sec. 1-2. Its primary importance both in rubber and
    power-driven models--Professor Langley's experiences. Sec.