Chapter I: 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 formulæ 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 formulæ 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

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

CHAPTER I.

THE QUESTION OF WEIGHT.

§§ 1-2. Its primary importance both in rubber and
power-driven models--Professor Langley's experiences. § 3.
Theoretical aspect of the question. § 4. Means whereby more
weight can be carried--How to obtain maximum strength with
minimum weight. § 5. Heavy models versus light ones 4

CHAPTER II.

THE QUESTION OF RESISTANCE.

§ 1. The chief function of a model in the medium in which it
travels. § 2. Resistance considered as load percentage. § 3.
How made up. § 4. The shape of minimum resistance. § 5. The
case of rubber-driven models. § 6. The aerofoil
surface--Shape and material as affecting this question. § 7.
Skin friction--Its coefficient. § 8. Experimental proofs of
its existence and importance 7

CHAPTER III.

THE QUESTION OF BALANCE.

§ 1. automatic stability essential in a flying model. § 2.
theoretical researches on this question. §§ 3-6. a brief
summary of the chief conclusions arrived at--remarks on and
deductions from the same--conditions for automatic stability.
§ 7. theory and practice--stringfellow--pénaud--tatin--the
question of fins--clarke's models--some further
considerations. § 8. longitudinal stability. § 9. transverse
stability. § 10. the dihedral angle. § 11. different forms of
the latter. § 12. the "upturned" tip. § 13. the most
efficient section 13

CHAPTER IV.

THE MOTIVE POWER.