Daylight On Dreamships Part 1, 2 & 3

DAYLIGHT ON DREAMSHIPS (Part 1)

By Fred Lindsley

(This article is from SAAA's "Airsport" magazine November/December 1987 edition)

Airsport publishes this first of a series intended to assist SAAA members who have asked for guidance on how to go about drawing their own dreamships. There appears to be very little published today which adequately covers the preliminary requirements, because most books assume a good deal of prior specialised knowledge with which intending amateur builders may not be conversant. This introductory article by Fred Lindsley is an attempt to bridge the gap.

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Fred Lindsley has been a contributor to Airsport for some years and is currently SAAA Technical Co-ordinator. He admits to being a bit younger in this 1934 pho­tograph. The aircraft, no dreamship, was the one and only Napier Rapier Courier which featured two crankshafts, sixteen air-cooled cylinders, and also a number of educational opportunities for removing engine cowlings.

From Dreamtime to Drawing the Line Somewhere

“And by a sleep we end the heart-ache
And the thousand natural shocks…
Perchance to dream…
And lose the name of action.”

This extract, from a long-established soap opera, with overall audiences possibly exceed­ing those of ‘Dallas’ or ‘Dynasty’, arouses the speculation that it was quoted by an early amateur aircraft builder. That it was written just 80 years after Leonardo da Vinci (1452-1519) ceased to embellish notebooks with his famous designs for flying machines and helicopters gives substance to this surmise.

The cold fact that ancient castles in Denmark are unlikely to promote good glue adhesion, or provide suitable doping facilities, strengthens the theory. That Hamlet, if not provably the first -amateur aircraft builder, was almost certainly the first to entertain ideas, perchance, about dreamships. Of course he had his problems too, but demonstrated acute perception when he observed that dreaming does tend to put the handbrake on action.

In this, and some succeeding articles, an attempt will be made to help the reader towards converting sketched dreamships into an interesting recreational activity. Of course they may never fly, but at least you should get to the stage where you could be confident that it would fly, and safely fulfil your dreams, if you ever got around to building it. The project we are about to embark upon will not involve expenditure in very sophist­icated drawing boards or a financially ruinous collection of textbooks full of funny double integral signs. Nor will you need a computer because the mathematics will be school-kid stuff. And, as far as possible, the words will be made so simple that even the mythical Sunshiners will show a slight glimmer of comprehension.

This writer reserves the right to add a bit of colour here and there because any formal explanation of essentially tech­nical subjects can make very dreary reading. You may also have an encouraging incen­tive. J.W. Dunne was eminent for his serious research into dreams. His books ‘An Exper­iment in Time” and ‘The Serial Universe’ enjoyed some fame at a time when Albert Einstein’s theories were gaining wider acceptance. A few decades earlier this researcher had built a number of tailless biplanes and monoplanes, and flown them, culminating in the Dunne D9 of 1914.

In this introductory article we will deal with some layout basics. Scheduled for the future will be sections covering performance prediction, materials, engine and equipment installations, landing gear considerations and very elementary aspects of structural strength. If there is any feedback from readers the order will be changed to suit any majority requests and maybe amplify the series as required.

Dreams at Dawn

In our sports aviation context we have to face up to an acceptance that the term ‘Dreamships’, long established and as popul­arly understood, is actually a contradiction in terms. Dreams are intangible things. No matter how vivid and colourful, there is as yet no method of recording them, not even with the most advanced modem electronic encep­halograph apparatus which detects alpha and associated brainwaves, or by investigation into the subtle electro-chemical processes accompanying brain activity. So, for practical purposes, dreams have no reality.

On the other hand, dreamships do have some reality before you even sharpen the pencil. There, before you, is the proverbial back of the envelope where, by repute although almost entirely false, every famous aeroplane in aviation history is claimed have to have originated.

Thus, by a most ingenious paradox which Gilbert and Sullivan would have be proud, what has no reality has been transformed into something which is real.

A paradox like defying gravity which, on temporary basis, is the nature of aviation and, for more finite periods, the aero-space industry’s contribution to those radio transmitting devices currently travelling to the outer planets.

Having accepted reality as fundament to the dreamship deal, it is not too difficult to take the subject a bit further than the usual sideview on the back of that envelope. Those racy lines, the so streamlined moulded canopy sketched without regard for the tooling costs, and the inevitable propeller spinner which almost exactly duplicates the nose of those bombs developed for altering the architecture of 10 metre thick concrete submarine shelters. My grandchildren can do that. They can do the snazzy colour schemes too. When they grow up and become SAAA members it is to be hoped that they have progressed further than this slightly juvenile approach to dreamships.

The true and most satisfying dreamships are those which you are fairly certain would fly in the manner and style you intended. If you could only find the time to finish the drawings, or the time to build it.

In other words, your dreamship is something you think might fulfil the need of something you want. Not one of those aircraft from the hundreds of sets of different drawings which have been marketed over the last 50 years. Not even one of the over 80 types currently approved for amateur construction in Australia (there are five gliders on the list too… the present grand total is 88). Not even a pirated copy of something appearing as a coloured photo you just saw in an oversee magazine. None of these. Just your very own design to perform exactly as you want.

Exactly what you want is the operative clause. This is where your dreamship starts. So, for the time being, just put aside the back of the envelope and get a bit of rule paper. Thoughtfully suck the end of your pencil and decide what you want you dreamship to do. As each decision is made write the requirement down on the rule paper.

Ideas like the following may cross your mind:—

a) Indisputably you will want the aircraft to carry you aloft. Maybe Mum and the kids too.

b) You will want it to fly a certain distance which may vary from a quick circuit to non-stop between Brisbane and Perth. Also at a selected speed.

c) You will need enough fuel to fly this distance unless the chosen geography gives you an unlimited supply of thermals.

d) A decision has to be made on whether you are going to restrict your take-offs to the local international airport, or shorter, and the ability to alight on an ant-hill or a measurably longer landing run.

e) There may be dimensional restrictions because your workshop is only so big.

f) It has to have an engine and unless you are very lucky or rich you might, today, have to look a bit down-market in the power bracket.

g) You will require more on the instrument panel than just the reflection of your happy, beaming face. Just in case such vanity results in your failing to maintain a sharp lookout, which might precipitate a mid-air event, the law requires a mini­mum quantity of certain instruments, all cunningly designed so that not one of them is big enough to initiate lengthy distractions with reflections of your smil­ing image.

So the dreamship starts with decisions… decisions, but is certainly not going to give you a nightmare. Here you are in total command of the situation. All of the decisions are yours alone and you can be sure that, whatever your faults, being wrong is not one of them. Agreed that by the time you get the list finalised the temptation to use your lawn mower engine may have moderated, and the embodiment of an inertial navigation unit repositioned in the priority scheme of things.

In reviewing your list, while chewing the end of the pencil again, the conclusion may be reached that everything has a numerate value. There is the weight of what you want to carry and the weight of what has to do the carrying; the good news is that there is a fairly reliable ratio between these two weights, which will be amplified later in this series. Then there are dimensions and, a bit further along, things like area and wing loadings which will help you to make a quick but near-enough first estimate of the stalling and maximum speeds. (How about three minutes to do both speeds? Stick with this series and you’ll find that you can do it).

This is exactly the point where the dream begins to fade. It is wake-up time and you have to go to work. Nobody is going to give you your stalling speed as a free gift and, if they do, how do you know that they’re not lying through their teeth? You are now right in there with the pioneers, the Wright broth­ers, A.V. Roe, Donald Douglas and the rest. Figures. Those accursed figures!

Of course you have a choice. If you are disinclined to work, don’t want or don’t need to cam a living, you can doze off again. To that pleasant dreamy state where you can, for ever and ever, continue to sketch side views on the backs of envelopes. This has been described as intellectual masturbation and they do say that it is no substitute for the real thing, even more so if there should be entertained prospects of a viable concept.

So, as the pearly fingers of dawn start to direct light on your dreamship, in real time it’s probably nearer the hour when you have to put the cat out and lock up. Now that your dreamship is just starting to take shape the chances are that your dreams might improve too.

What You Need To Have

Not very much. No elaborate drawing machines or rolls of dye-line paper. No liquid nitrogen cooled computers with coloured graphic display. No sagging book shelves loaded with massive volumes crammed with algebraic formulae.

In the early part of this century a famous aeronautical pioneer, Professor Lanchester (a practical man, he made the first automatic gearbox for motorcars as well) said that 99 per cent of engineering was done with school­boy mathematics. He was, and still is, correct.

Dreamship drawing requirements are modest and you can get by with the following:—

Paper. Minimum A4 size. Preferably plain. If you use graph paper you may be stuck with an inconvenient scale. Moreover the final sketch doesn’t look so impressive.

A ruler with inches in decimals, and millimetres. If you can get a scale rule, preferably metric, so much the better, but these are now far too expensive for what they are. You can work to all sorts of different scales if you use a pocket calculator memory button and say ‘12 inches or 1 foot on my dreamship is going to be 6 millimetres on the rule’ (or whatever scale you decide on). In this example you will be drawing at a scale of about 1:50 and a 30 foot span dreamship will measure 180 mm (or 7.08 inches) on your drawing.

A cheap set of school drawing instruments, obtainable at any stationers or supermarket. These contain a 30 degrees and 45 degrees setsquare, a 180 degrees protractor and a compass. If you scratch a fine line down the middle of the 45 degrees plastic setsquare, from the long side to the point of the blunt 90 degrees angle, it is ideal for marking off lines which are dead square to others. So you don’t need a drawing board and tee-square.

A circle drawing template is worth its weight in gold. Far better than trying to use a compass except for big radii. The Staedtler 977-5 10, 2 mm to 50 mm. is an ideal type, but any similar template will do as good a job. Some cheap French curves. They usually come in sets of three but, for the initial sizes of drawings we are talking about, the smaller the size the better. Do not be bamboozled by the so-called adjustable curves which can be bent by hand and look like a dead caterpillar. You will find, in practice, that they are exasperating.

Some 2H or H hardness pencils. Softer pencils need constant sharpening and tend to smudge drawings.

A good pencil sharpener. The little al­uminium extrusion ones where you can screw on replacement blades are the best value for money.

A good eraser. Preferably the type with a sharp edge. The eraser looking like a felt pen but holding a rubber about 8 mm diameter which can be extended bit by bit is most useful. You will find that erasers get a lot more use than you initially expected.

If you need to, stick your paper down on a suitable smooth board with bits of masking tape at the corners. Drawings which move when you are trying to draw a firm line produce language unsuited to the domestic scene. Avoid using scotch tape which often perversely tears the corners off a completed drawing.

A simple calculator. The very cheapest providing it has a square root function which, later, is going to save you a lifetime of guesswork. Before we get very far into this dreamship series you may find yourself using the calculator more than any other drawing instrument. And wondering why the hell you hadn’t made this discovery before. If you have, or can borrow, a scientific calculator with all the whistles and bells you may get around to using very few of these facilities. Just the trig functions (sine, cosine and tangent) and then only much later in the piece when the dreamship might look eligible for graduation to a bigger drawing board. These functions are just enormous time savers. In the days of slide rules it was usually quicker, and much more accurate, to look up the trig tables, which are still available at second hand book shops.

Reference books. The sad fact is that today you cannot buy, at any price, a useful begin­ners book. Hence the idea of this series. Even the books written prior to 1945. which are the only ones of much use for the sort of aircraft we have in mind, assume previous and specialised knowledge which the average keen enthusiast may not have. There is perhaps one single book which can be recom­mended, now out of print, but it covers a wide field in readable language. This is ‘Man Powered Flight’ by Sherwin. (There is a USA book of the same title, by a different author, which is unlikely to offer you the sort of assistance you are hoping for).

The best sort of information is free. Librar­ies. Particularly State Libraries which have an interstate lending service. Browse into books. Photocopy the bits that interest you or you think you can cope with. Quite quickly, for your dreamship, you will be compiling your very own manual on how to do-it-yourself. This demonstrates the Wright outlook.

As Misty Dawn Steals into Glorious Day

Steals is the go-word here. You must become an accomplished thief. As has been observed, ‘Stealing one person’s idea is pla­giarism. but stealing ideas from a lot of people is research’.

So an essential first step for your dreamship is the amassing of as much data as you can get on aircraft in the same category. Extracts from magazines, photocopies from the lib­rary, and so on. List their dimensions, wing areas, weights, engine power and performan­ce. Work out some averages. If you have a cautious mind, plot some of the data on graphs and you might see whose claims are suspicious or aerodynamically impossible. You would be surprised how often this happens, notably in the ultralight field).

Recognise that you are a beginner. That in a first attempt your chances of doing better than X or Y or Z are somewhat slender. At the same time be confident that, if you tackle your dreamship in a methodical way, you are unlikely to do so very much worse.

By this time your drawing should be taking shape. If it begins to look promising, always take it to the standard three views side, plan, and front. You will usually find that an adjustment in one of these views entails a corresponding manipulation in at least one of the other two views.

Imagine that you want to make a scale model of your dreamship and you will soon get tuned in to the desirability of three separate views. Bear in mind that the drawing is meaningless until it has a certain minimum of data added. These might be wing span, loaded weight, proposed engine and power, and the scale of the drawing (which is also meaningless if the drawing is not reproduced at full size, or some measurable dimension is quoted). One thing is sure, the added data will be figures. Never any escape, is there?

If any readers would like to send copies of their dreamship drawings direct to Airsport at SAAA Headquarters address we might get something going which will stimulate member into trying their hand. We will try and work some of them into future articles. Anonymity guaranteed, if requested, and there will be no rude awakenings if some have not yet fully emerged from the dream world.

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DAYLIGHT ON DREAMSHIPS (Part 2)

By Fred Lindsley

(This article is from SAAA's "Airsport" magazine January/February 1988 edition)

In this second part of a series Fred Lindsley continues an outline of preliminary guidance for SAAA members who would like to sketch their dreamships on the backs of envelopes. In this article weights and initial performance estimates are looked at, these being essential to promote confidence that your dreamship, if ever converted to hardware, will align with something a bit further down the track in this series — the flight envelope.

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At Mangalorc ‘84. Thc ‘Yellow Witch’ Olympia sailplane built in Melbourne by Arthur Harding just after World War II, with Keith Nolan (left) and Fred Lindsley who was on the Olympia design team. Keith is being congratulated after his encouraging demonstration that a vintage amateur built wooden aircraft was continuing to perform aerobatics nearly forty years after Fred did the original drawings. The Olympia retained only the external aerodynamic form of the pre-war DFS ‘Meise’ (Tomtit). Everything else was redesigned right down to riblets, mainly for production reasons, but there was a substantial strengthening of the wing structure to comply with the revised ARB gust requirements introduced in 1945.

Introduction

First the good news. We are going to use Imperial units and, in essence, there will be no Metrics. Metrification laws notwithstand­ing, there are two good reasons for this.

Firstly, in international aviation speeds are in knots, height is in feet. and runway lengths are in metres. So the Imperial outnumbers the Metric by two to one.

Secondly, 99 per cent of the books you might eventually (actually inevitably) have to delve into use Imperial units. The very few in English using metric units are, in most cases, not very useful for the simple light aircraft we are concerned with here.

Now, not exactly bad news but a note of caution. Should it come to my attention that any readers are using this series as a basis for full size design, without doing any further reading, they will rapidly find themselves qualifying for diplomas in the Sunshiner’s Hall of Infamy. Each exhibit will be identified as a Sunshiner’s Trophy: Ultimate Pernicious Ineptitude Diploma, or STUPID for short. This ‘Daylight on Dreamships’ series is intended to assist only, as an introductory to the many and varied textbooks on subject. It is shallow end of the pool stuff, but it’s exactly the same water as would immerse you if, having gained confidence by getting your feet wet, you immediately dived off the highest board at the pool. Just as it is exactly the same air and aerodynamics applying to dreamships and real aircraft.

Some Very Essential Basics

Due to technical difficulties in typesetting, the square root sign had to be substituted with a check + sign. (Ed.)

This will be a guide to a little fundamental mathematics and those conversant with the subject can skip this section.

It has been this writer’s observation, and very probably one of the factors preventing SAAA from accomplishing more over the years than it has done, that much of the ill-founded belief that aviation technicalities can best be done on a rule of thumb basis by self-avowed Real Practical Men, stem from the probability that quite a number of these people vehemently rubbish figuring because actually they do not understand the, basics but are unwilling, or too shy, to admit the fact, or to do anything about it.

More often than is desirable, people are seen looking at a square root sign with much the same degree of comprehension as I would apply to a treatise in Japanese on the vocal chords of jellyfish. Nor does it seem to occur to these people that for about a quarter of the price of a video cassette, they could get some secondhand school books and, in very few evenings, give themselves a fair grasp of’ the subject which differentiates between engineering and bending horseshoes at the anvil. The fact is that you CAN NOT weigh the smallest aeroplane and work out the operational centre of gravity limits without applying a teeny-weeny bit of algebra,

Those who think otherwise have, for too long, done the whole of the Amateur Built Aircraft Movement a gross disservice, be­cause they indecently expose themselves as aeronautical clowns to the people who do know. The latter include a number of charac­ters who may create and rigorously apply regulations which control the building and operation of amateur aircraft.

But here we are not going to deal with algebra, because there is a book called ‘Teach Yourself Algebra’ and, if you can’t buy that or get it out of the library, the truth is that you are wasting your time (and probably that of your admiring viewers) in doodling about with dreamships.

The foregoing paragraphs are just as essen­tial as the part now appended.

A square root sign as in √25 means you have to find a number which multiplied by itself gives 25. So √25 is 5. and √49 is 7, and √100 is 10. There are lots and lots of square root signs around in all sorts of engineering. When working with formula it is important to note how much of the top bar covers numbers.

For instance, √25 x 4 means 5 x 4 = 20, but √(25 x 4) means √100 = 10. Similarly, with fractions, note the height of the front leg which will indicate whether you just get the square root of the top bit and then divide that by the bottom of the fraction, or you work out the whole fraction and then find the square root of that result. There can be an enormous difference, so always look very carefully at the front and top lines of root signs.

There are also cube roots as in 3√27 where a number has to be multiplied by itself three times, the answer in this case being 3. The cube root is an essential part of aircraft power because propellers on aircraft (and boats) follow a cube law. Unlike a motor car, you can’t look at an engine HP curve and say “1 see that at 90 per cent of the maximum revs we are still getting about 95 per cent of the maximum HP”, because at 90 percent of maximum revs a propeller will absorb only about 73 per cent of the maximum HP. Truly aircraft are different and you had better believe it. Fifth roots 5√ are also used in propeller design.

The other essential is the exponential, also known as the ‘index’ or ‘power’. This is a little number perched higher and to the right of another number (or symbolic letter such as ‘y’). If the ‘power’ is 2 it means that the first number has to be ‘squared’ or multiplied by itself. If the ‘power’ is 3 it means the first number has to be ‘cubed’ or multiplied by itself three times.

Examples are:- 112 = 11 x 11 = 121 43 = 4 x 4 x 4 = 64

And that’s it. Not much is there? Makes you wonder why the Real Practical Men go on at such length for so many years about all this theoretical bullshit. For dreamships you can get by with very few formula, but what you CAN NOT do is make any realistic prediction of performance without using square roots. The most important and most used formula, involves solving a square root to get your airspeed. We are coming to that a bit further down the page.

Weight Estimation

Aircraft being gravity defying mechanisms. it is fairly obvious that the airborne weight deserves the closest attention. For our dreamship we shall assume that MTOW (Maximum Take Off Weight) and AUW (All Up Weight) are the same thing and, for the sake of brevity, stick to AUW.

AUW controls performance including stall­ing speed and rate of climb. It also controls strength and you can not properly begin to stress any man-carrying aircraft, including hang-gliders, until you have made a reason­able estimate for the wing weight, which includes half the weight of the struts in a braced monoplane like the Piper Cub. This is why aircraft companies had substantial Weight Control Departments estimating weights. Even to the weight of paint on small components before the prototype was built. Just ½ per cent up on a Lancaster Bomber empty weight, was 185 lb or 26 Imperial Gallons less fuel to get home with.

In the first part of this series it was recommended that the first step was an assessment of what you wanted to carry in the way of occupants, luggage, fuel, oil and extras like Loran-C receivers. For average purposes, an occupant weighs 170 lb. but bear in mind that two 200 lb occupants are not unusual, so be prepared to sacrifice luggage or fuel. Exceeding any certified AUW reduces performance and the strength factors on the structure. Broken aircraft are more common than broke insurance com­panies!

Fuel weight can be taken at 7.2 lb per Imperial Gallon (4.54 litres) and oil at 9 lb per Imperial Gallon. Extra equipment weighs whatever the catalogues say, plus. usually, more weight of wiring or antenna attachments than you had reckoned on.

As there is no substitute for doing detail design and working out the weights (unless you have a lifetime store of comparative data) for dreamships, one can only generalize in a very broad way. If we say that a small single seater will have an empty weight of 54 per cent AUW, this latter figure becomes com­plete nonsense if you decide to also fit a starter, altemator, battery and the whistles and bells of a Wurlitzer organ.

So, to generalize, you can initially apply the following which is based on an analysis of 36 Amateur Built types, excluding biplanes and amphibians.

Single seaters: Empty weight varies from 52.9 per cent for a top speed of 85 knots, to 68.1 per cent at a top speed of 160 knots. Unlike the two-seaters below, on single seaters %AUW tends to go up with speed because the very fast ones usually have a racing heritage where bigger and heavier engines are put into not very much changed airframes. Two and multi-seaters: Empty weight varies from 60.3 per cent at 85 knots top speed to 55.3 per cent at 160 knots top speed.

There is little evidence that different constructional materials have any notable effect, despite various claims. On a small aircraft, no matter how you cut the cookie, an awful lot of what goes on the scales is non-composite engine, non-wooden wheels, non-steel tube tyres, safety harness, cushions, instruments and odds and sods which are common to all aircraft. Plus white paint which is heavy, and ‘featherfill’ which is heavy-heavy. (You don’t believe? I know “what Merv sez”. Have you ever done a before and after weight check on this material?)

As an example, you have a dreamship with a disposable load, occupants, fuel, oil and luggage of 550 lb. At the top speed you hope for say the empty weight looks like 57.8 per cent AUW. So the disposable load is 42.2 per cent AUW. So AUW = 550 lb ÷ 42.2 × 100 = 1303 lb. Say 1300 lb or 590 Kg AUW.

There is more to weight of course. Later you have to do a component break-down i.e. wing, fuselage, tail assembly, engine installa­tion etc, weights in order to fix the empty centre of gravity position. Note that retracting undercarriages. even on small aircraft like the KR2, can move the CG by a dimension not aligning with eyeball opinion. Without the empty CG you can not start the invariable juggling of movable loads to ensure that the flying CG fore and aft limits are not exceeded. There are more dreamship shortcut methods for this too and we will come to them in a later article. In the meantime reference to Airsport issues of July/August and Septem­ber/October 1983, might give interested readers a preview of the subject.

Preliminary Performance Estimates

At the risk of breaking a few automotive hearts, which will cause this writer no distress whatsoever, it must be pointed out that the speed of aircraft is not related to engine power. If it were, gliders and steerable par­achutes would be at a very poor stage of development.

Because aircraft speed (and, yes thank you, I can hear those crankcase polishers getting cranky. but powerplants are scheduled as a future attraction) has everything to do with the Lift Coefficient - that little symbol CL which keeps on popping up in the formulae. If you have some old books or aerofoil curves which refer to it as KL. take care, because a KL is half a CL and the speeds you work out might be only 141.4 per cent of what they ought to be.

The speed of an aircraft is fixed by the formula: -

V in feet per second_= √(W÷(A× 0.00118 × CL))

Where W = Aircraft weight in lb.

A = Wing area in square feet.

CL = Lift coefficient of wing aerofoil.

0.00118 applies to air at sea level and Intem­ationaL Standard Atmosphere at fifteen degrees Celsius.

In most books it appears as the symbol ‘ρ/2’ because the value decreases with alti­tude and the 0.00118 is down to 0.00054 at 20,000 ft.

The ‘ρ’ is actually the Greek letter “rho”.

Aircraft, like canaries in cages, stay in flight by pushing their own weight of air down­wards, thus neutralizing gravity. A cubic foot of air weighs 0.076 lb. Divide this by 2G (64.4 ft per second per second) and, Eureka! we get 0.00118 (at sea level).

Note that the velocity (speed) V comes out in feet per second which, multiplied by 0.592, converts into knots.

Don’t knock this formula. Using a different figure than 0.00118 to allow for water, the same formula is used for hydrofoils, hard chine boats, water skis, sailboards (above and below the waterline would you believe?) and the rudders of 500,000 ton ships. It also has relevance to propellers and the fans in motor cars. It has one great thing going for it. It works. One of its secondary advantages is that it is a most efficient lie detector.

At top speed in level flight CL values will vary from about 0.4 on an aircraft well-endowed with built-in headwinds like the Breezy, to 0.2 for out and out racers. The DH88 Comet racer seen at Mangalore ‘86, had 0.207. (Note: The expression ‘top speed’ has been used instead of ‘maximum speed’ to avoid confusion with CL max which applies only to minimum or stalling speed.)

For an example, take the 1300 lb AUW aircraft we nutted out in an earlier paragraph and say we give it a wing area of 102 sq. ft. and a likely CL of 0.3.

V in fps = √(1300÷(102×0.00118×0.3))

= √36003

= 189.7fps

Top speed @189.7 feet per second

@112.3 knots.

This example is just to initiate familiarity in using the standard formula. If you change the CL value to the maximum you can get out of the aerofoil you use (with or without flaps), you get the stalling speed of the aircraft. Have care here too, because there are aircraft around which have a minimum controllable speed well above the theoretical stalling speed. Operation of aircraft at CG limits can sometimes alter stalling character­istics too.

The obvious difficulty lies in selecting a near enough correct CL for top speed, a difference of 0.01 resulting in about 2 knots change. Fortunately at the slow end, a CL difference of 0.01 alters stalling speed by only around 0.2 knots.

In normal practice it is done properly with CL increments of 0.1 through the whole range, ether with the relevant figures for the profile, induced and parasite drag coeffic­ients, but for dreamships we can take a shortcut by juggling with the same formula. (A juggling which applies algebraic principles without actually using any algebra).

Look around for some data on two or three aircraft of fairly similar configuration to your dreamship, eg. monoplane or biplane, fixed tricycle gear or otherwise, etc. Record their AUW, wing area and top speed. Convert the top speed to V in feet per second. (V fps = MPH× l.467or Knots × 1.689).

Then CL at top speed =W ÷ (A × 0.00118 × V2)

Note that we no longer have any square root sign and that V is squared in the bottom line. If you use a calculator, it is easier to reckon it as V x V and divide by V twice.

Supposing we check this out on a Minicab which has an AUW of 1235 lb, wing area of 107 sq. ft. and top speed of 124mph -181.9 fps.

Then top speed CL = 1235 lb ÷ (107sq. ft. × 0.00118 × 181.92)

= 0.295

Check a few more aircraft of the same type. Anybody who is getting less than CL 0.25 is possibly telling lies about the top speed, or has temporarily blanked off the cooling air inlet to the engine which is respon­sible for much more of the aircraft total drag at high speeds than is usually realised.

Stalling Speed

This is fairly straight forward and can be done by analysing similar aircraft, with simi­lar flap proportions where applicable and using the same formula as used to find CL at top speed, except that you will use a quoted stalling speed to find the CL at the stall. The convention is to use the symbol Vs for stalling speed (in fps of course) and CLmax for the CL at the stall.

There is a quicker way providing you have a reliable CL for top speed and the windtun­nel test curves, which give you CLmax for the aerofoil you intend using. For the same AUW at the same atmospheric condition, the ratio between top and stalling speeds will always be:

√(CLmax ÷ CL at top speed)

Supposing we select an aerofoil with a CL maximum of 1.5 and a CL at top speed of 0.3.

Then the speed ratio is √(1.5 ÷ 0.3) = √5 = 2.236

Take the sample aircraft for which we got a top speed of 112.3 knots. Divide this by 2.236 and we get a stalling speed of 50.2 knots. No kidding! Don’t believe what anybody TELLS you. They always say they flew their aircraft alongside another one and the ASIs were absolutely identical, so the ASI must be spot on. True no doubt. But do they have the same pitot and static position error at the stall? Ah! Stick with the figures for your dreamship. In an endeavour to reduce stalling speeds, try not to be too enthusiastic about the CLmax you hope to get from the wing on a small aircraft, where the fuselage occupies a fairly large amount of the gross wing area.

Airliners with complicated flap and slat systems (and. with long chords, high Rey­nolds Numbers) achieve high CL values. Published figures for CLmax are 2.91 for the Boeing 737-300, 2.98 for the DC9-30, and a remarkable 3.46 for the BA 146 operating in Western Australia and seen at Mangalore ‘86. Smaller aircraft do less well. A STOL aircraft like the Pilatus Porter gets 2.28, the Beech Queenair 1.88 and 1.86 for the Cessna 177.

Four points are of importance in connection with stalling speeds:

ONE: They are the basis of the flight envelope on which the strength of the aircraft depends, so they had better be authentic right from the beginning.

TWO: Stalling speeds are also the funda­mental factor in most design requirements for landing gear strength and energy absorp­tion. So realistic speeds are again preferable to carefree optimism.

THREE: Far too many published stalling speeds and notably in the Ultralight field, appear to have been recorded on a very hot day by a dwarf doing an emergency landing with completely dry fuel tanks. Just apply cold logic with the calculator so you will soon learn to separate the sheep from the goats and, where well-evidenced, also devel­op a detached impartiality about some quoted top speeds and rates of climb.

FOUR: For Amateur Built aircraft coming under ANO 101.28. particularly with non-certified engines, the subject of stalling speeds can make all the difference between accep­tance or rejection for type approval. Just read the ANO and you may find that half a knot too much could give you problems.

So, to accelerate your dreamship just half a knot faster towards reality, we just have to work in a bit of elementary aerodynamics involving the dreaded Reynolds Number.

On most aerofoils the maximum lift coefficient decreases with decreasing Reyn­olds Number (RN for short). There are a few exceptions where the reverse applies, but those aerofoils have some other snags. The graph I have drawn explains what the RN is and how it affects CLmax characteristics on three different aerofoils. While we nor­mally assume that RN varies due to changes in speed, there can be significant variations at the same airspeed as a result of wing taper. This gave problems in the very early days of sailplanes when, to reduce wing weight, taper ratios of up to 5:1 were tried, thus condemning the wingtip aerofoil to life imprisonment at an RN only one fifth of the RN at the wingroot. In turns, getting towards the low end of the speed range, the inside wingtips just fell out of the sky and initiated spins.

Let us revert to the dreamship which had an AUW of 1300 lb and a wing area of 102 sq. ft. Imagine yourself dreaming about an aerobatic category, so you opt for a four feet wing chord and the NACA 0012 symmetrical aerofoil. You look up the standard aerofoil curves and see that 0012 has a CLmax of 1.56. Beauty! Ignore the small print which states that the test was done at an RN of around 3.200,000.

Using the first formula given above, the stalling speed works out at 83.2 fps or 49.3 knots. But at 83.2 fps a four feet wing chord is operating at the smaller RN of 2,123,000 and my ‘dreamship’ graph indicates that the CLmax on this aerofoil has slumped to 1.46. Calculating again with this value, we get a revised stalling speed of 86.01 fps or 50.9 knots. The ghost of Professor Osborne Reynolds (who started all this nonsense in 1883), has malignantly reached out and pushed up your stalling speed by 1.6 knots.

The moral is not to accept as gospel the CLmax values seen at the peak of the CL curves, for any of the hundreds of aerofoil tests which have been recorded in the litera­ture. (Only a handful of them are likely to be of any use on our dreamship.) Check the RN at which an aerofoil was tested and adopt a stay on the safe side’ philosophy.

Not that the Reynolds Number is any big deal, although its effect is much more significant when aircraft drag estimation requires more sophistication than applies to dream-ships. The purpose of this exercise is merely to demonstrate how it functions, and how it can matter if you are trying to manipulate a border-line case into compliance with ANO 101 .28 and you can’t get much more practical than that. Perhaps RN can bear thinking about on some modem aircraft with rather small wing chords towards the tips or canard fore-planes.

When it comes to flaps, exercise extreme caution. Much published data applies to full-span flaps on wings devoid of a rivet head, let alone a fuselage. Small aircraft prefer ailerons for roll control, so full-span flaps aren’t in the picture and the overall loss of CL on the wing, is usually more than can be calculated by simply proportioning flap area, because there is a quite big vortex at each of the outboard ends of the lowered flaps. The answer to this problem is what this series is all about. Do more reading.

In the next instalment we will continue performance with rate of climb and here, very definitely, there will be recognition of the power supplied by engines and propellers.

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DAYLIGHT on DREAMSHIPS (Part 3)

By Fred Lindsley

(This article is from SAAA's "Airsport" magazine March/Aprial 1988 edition)

Continuing this series for doodlers on the backs of envelopes, in the hope that a less random mode might be introduced to the point of the pencil, Fred Lindsley in this third article looks at the application of power to performance.

Power, from Paper to Propeller

To begin with the writer would like to thank those readers who have said and written kind words about the first Daylight on Dreamships article. It is very satisfying to discover. In this day and age, that there are still people around who acknowledge that what they are getting from Airsport is something they are unlikely to get from sitting down and gazing at all the other media channels for the rest of their lives.

In the previous article the statement was made that the speed of an aircraft was, strictly speaking, a function of lift coefficient and not of engine power. This caused some consternation among the myth happy Sunshiners. Cohorts of cane toad couriers brought messages of indignation and scaled down protest placards with admonishing words like ‘High Treason’ and Get Detonated Extremely interesting, because we now have proof that cane toads can spell.

So, to open out our dreamship perspective and on the basis of a certain amount of hands-on experience with power plants, this writer is forced to admit that engines do contribute to the flight of powered aircraft. Engines and propellers accelerate aircraft forward, which normally gets them into the air. Engines also accelerate aircraft upwards, so you can climb over that tree at the end of the strip, so malevolently seeded by the wind about a hundred years ago.

To accomplish this, ie. get airborne and climb above the tree, not only requires power. It requires a certain minimum of power. If there isn’t enough urge, you will merely taxi at very high speed into the bottom of the tree trunk, thereby spoiling that part of the tree as a substitute for spruce. Although kilowatts are all the go, we are going to continue with horsepower (HP) because, for aircraft, that is what most of the books and power curves deal in.

There are all sorts of horsepower around. Such as Indicated HP, Friction HP. Brake HP and Shaft HP. The latter is the one we are basically interested in and, for aircraft, is usually the same as Brake HP.

Now it is time to ring a little warning bell, particularly if your experience of power has been confined to a family sedan automotive or power boat background. Even at the ‘this is the end where the real work comes out’ of an engine, there are all sorts of different Shaft HP. A very well-established four cylin­der diesel, much used in boats, industrial equipment, and vehicles, has 58 HP by the USA SAE rating, 46 HP by the recognised testing methods of one European country, and 47 HP in another European country where the engine is actually manufactured.

When the published figures differ by 26 per cent, even the most starry-eyed dream-ship enthusiast might suspect that SAE rat­ings are not always what they appear to be. The USA OBC ratings for outboard engines are also somewhat on the side of undue optimism. If you are thinking of lifting your outboard off the transom, hooking up a radiator and sticking the concoction into a dreamship, you would be well advised to read some books about aero-engines, and notably their cooling, before you get to the ‘Lets open the throttle’ stage.

Manufacturers of certificated aircraft engi­nes adhere to the truth much more closely. They know that aircraft designers dislike having their brain-children converted into runway-extending bulldozers: and pilots may even express their dislike in somewhat stronger terms.

Consequently, with a certificated engine, you get some curves which very nearly tell you what you want to know, such as what you can expect to get out of the business end at maximum permitted RPM, for a certain period of minutes, sucking in air at a specified temperature, humidity and barometric pressure.

All the latter can affect engine power output. Such power variations (for better or worse) are easily calculated by anyone not devoted to the sacred mystery of ‘tuning for power’ car or motorcycle engines and saying “Gee, don’t it sound great”. Vroom, vroom, and it is on the road (or track) to sooner or later destruction.

In the above paragraph and re-certificated engines, ‘nearly’ is the word to give you pause. What was the exhaust back pressure on test’? Did the engine on test have an air filter or a weird maze of metal work cobbled up as a carburettor heater box? Did it have any of the accessories designed to rob Peter, at the propeller end, by paying power to Paul elsewhere in driving fuel pumps, altern­ators, vacuum pumps and Gold Lotto select­ion drums? All of which steal go-power away from that which the certificated engine manufacturer (and the Department) virtually guar­antee to supply you with IF, and only IF, you read the small print.

Having got the power we want where we want it, it’s still not going to do us much good until we devise a complicated transmis­sion system to rotate the nosewheel or the main wheels. And that is not going to be a lot of use either. Having rotated the wheels fast enough to get into the air, the engine is in danger of over speeding until your dreamship sinks back on to the ground and rips a bit more rubber off the power driven wheels.

No good? Agreed. In conventional pow­ered aircraft, unlike vehicles, Shaft HP is of no use until it is converted into Thrust HP. The best machinery for doing this is the simple one-piece of (usually) wood which is (usually) stuck on the front of the aircraft. The propeller. The deceptive simplicity of which can induce considerable misunder­standing of its complicated function. Even small fixed pitch propellers combine a com­plex mixture of aerodynamic, bending, twist­ing, splitting, centrifugal and gyroscopic char­acteristics. Engine cooling is frequently part of this technical stew pot too. Propeller design can be a bit more complicated and tedious than that of some monoplane wings. The professional experts, for any new air­frame/engine/propeller combination, seldom get it right first time.

Propellers are the prima donnas of aero­dynamics. If you try to understand their whimsies you may get a good performance. Ignore them, or their interpretation of the operatic score, and the applauding audience might be scarce after the first appearance. Plus the distinct possibility that you may have done your investment dough.

Power, from Prop to Performance

The accepted figure for one horsepower is 33,000 foot lb per minute or 550 foot lb per second. To lift 550 lb one foot in one second, or 55 lb 10 feet in 1 second, or 275 lb 20 feet in 10 seconds, will all require exactly one horsepower. That is what is needed to do the actual work.

Invariably however, the associated lifting mechanisms, such as a block and tackle or a screw jack, develop friction which absorbs some power, so you have to put more power into the lifting mechanism than what you get out in useful work. The ratio of what you get out to what you put in, is the efficiency of the mechanism. Roller chains are very good, over 99 per cent. Screw jacks are terrible, about 16 per cent being regarded as pretty good although, of course, the expensive ones using recirculating balls like some screw jacks on big aircraft, are a lot better. Vee belts and toothed belts are not as efficient as you might believe (just try to find this information in most belt catalogues!) and, notably with Vee belts, efficiency tends to vary with the periph­eral speed of the belt.

A word of timely advice on belt drives, as everyone who knows the difference between a De Dion Bouton and a Porsche has the promising idea that belting car engines to propeller shafts is so easy that even I could do it. Just ruthlessly ignore the recommendations of anyone who has not tried their hand at the necessary calculations. These characters usually say “My mate Menv, beyond the Black Stump, used just a little bit of koala urine when he sliced his toothed belt down to a smaller width and after that his ultralight climbed like a homesick flying saucer etc. etc…”

It seems that all these sagas of witch doctoring folklore frequently align with a standard formula sequence:-­

1. The miracle worker is always some distance away.

2. He is a Real Practical Man with an awe-inspiring reputation for having out­smarted, and exposed as technical idiots, everyone in the business from Avro to Zenith.

3. The miracle cure usually involves some ingredient easily found in a rain forest or a car scrap yard.

4. My informant personally knows this miracle worker, and is subtly telling me that I do not.

Dreamship doodlers, beware of such blandishments. Don’t take candy from strange sources.

Since a propeller is a mechanism invisibly converting input Shaft HP to output drag-you-through-the-air Thrust HP, it too fails to achieve 100 per cent efficiency.

Propeller efficiencies over 80 per cent are rare and usually associated with fairly slow revving props such as those on man-powered aircraft, or those intended for special applica­tion such as record breaking. Small direct drive fast revving props may have efficiencies down to around 33 per cent at 6000 RPM. Reduction gearing bringing prop RPM down to 2500-and of course a bigger prop diameter may improve prop efficiency to 75 per cent. With a 50 HP engine the small fast prop will give 50 x .33 = 16.5 Thrust HP. but the larger slower prop will produce 50 x .75 = 37.5 Thrust HP, more than twice as much thrust from the same engine.

This focuses attention on the importance of the propeller as the essential link between fuel tank and flight. Furthermore, with fixed pitch props, where you can’t change the blade angle in flight, the efficiency varies with the airspeed. These propellers can be designed to give their best efficiency for short take-off, best climb, optimum cruise or maximum speed. Whichever condition you select for best efficiency, the other conditions will have a lower efficiency.

For dreamship purposes, it is unlikely that a better efficiency than 75 per cent can be achieved in practice and, down among the direct drive VWs, 70 per cent might be an occasion for pride. If somebody is claiming better in this bailiwick, I don’t want to hear about it. I just want to see the figures and tests which prove it. This is no digression because 5 per cent loss in efficiency, from 75 per cent to 70 per cent in a propeller, is chucking away 6.7 per cent of your fuel and, in the case of marginally climbing aircraft like some early ultralights, could prevent them from climbing out of ground effect after take-off.

Mentioning climb brings us hack to per­formance which was initially discussed in the previous article. To apply power via propellers to the rate of climb in aircraft, brings us to the next section.

A Bit of A Drag Can Weigh You Down

The Shaft HP of an engine is converted to a smaller amount of Thrust HP. How much smaller depends on the propeller efficiency which varies at different airspeeds and also, although very slightly, varies due to yaw, which includes vertical yaw as when the aircraft is flying at a higher angle of attack. Unlike motor cars, which generally go where they are pointed, powered aircraft hardly ever travel in the direction in which they appear to be pointed. The difference in angle changes all the time as fuel is used, or changes in airspeed occur. In certain cases this differ­ence in angle can (and has) cause propeller vibration varying from the nuisance to the serious category.

At maximum power in level flight, all the Thrust HP will be used for balancing the total drag from wings, body, tail, landing gear if exposed, each little excrescence like radio aerials and, far from least, the cooling drag of the engine which also means the radiator for liquid cooled engines. When all this drag exactly equates with the Thrust HP. the aircraft has reached its maximum speed in level flight.

At lower level flights speeds you require less Thrust HP. so you can throttle back a bit. But because the aircraft still weighs much the same, it can only sustain itself in the air at the lower airspeed by grabbing itself a higher lift coefficient. Which means a higher angle of attack for the wing. Which means more drag from the wing. The paradoxes come thick and fast (that’s aviation folks!) and it is not really so confusing as it might sound, but what it does mean is that there are no instant miracle methods of getting the proper answer. Except for our dream­ships, where we will short-cut like crazy, just to demonstrate that you can get pretty fair estimates if you work to the methods outlined below.

At any speed where less Thrust HP than the maximum is required, there is always some in reserve if you open the throttle. This is the Excess Thrust HP and is available for climb. Putting the cart before the horse in this explanation, we will first look into Rate of Climb in feet per minute. (Not fps which has been used in all previous formulas).

Rate of Climb (in FPM) = THPex * 33000 ÷ W

Where:

THPex = Excess Thrust HP

33,000 = Foot lb per minute for one HP

W = Weight of. aircraft in lb.

Now, although not quite true, for dreamships you can reasonably assume that the best rate of climb occurs at an airspeed which, in level flight, only requires half the engine’s maximum power. Therefore the other hall is excess and available for climb.

Take as an example the 1300 lb AUW dreamship we worked out in the previous article. Somebody has benevolently left a foundling Continental 0-200 engine on our doorstep, complete with logbook and all the makers’ literature. We can dream, can’t we? Looking up the 0-200 data, and promising not to get too smart-arse with fancy exhaust and induction systems, we can rely on this engine producing 100 Shaft H P at the shiny bit sticking out of one end.

Our friendly local propeller man swears blind that he has a carefully disguised boomerang which will give 75 per cent efficiency on the climb. He will specially varnish it and polish it to make sure.

100 Shaft HP at 75 per cent efficiency gives us 75 Thrust HP. Half of this keeps the aircraft level in the air at climbing airspeed, and the other half, 37.5 Thrust HP if the throttle is opened, can be turned into climb.

So here we go. No flight plan, no met report, no fuel costs and this is our lucky day no air navigation charges. Just a calculator or, in this Bicentennial year, a slate and a piece of chalk.

Rate of Climb (In FPM) = ( 37.5 HPex x 33000 ) ÷ 1300 lb

So Rate of Climb = 952 feet per minute.

Considering we started with short-cut assumptions, it doesn’t look too far off the mark either. (Note: In actual practice, at the climbing airspeed the engine may not produce its maximum RPM and so will not develop its full power. How much less means back to the engine data and a lengthier dollop of dreariness. Here we are short-cutting to make it easier for the readers to familiarize themselves with the basics. It’s no good just reading about it. You have to do it in order to learn. You can read a hundred books about riding pushbikes. but you learn most from the first ride in the saddle).

Now do the above rate of climb again, but overload the aircraft by 200 lb. Let’s make it legal and say we have redesigned our dreamship as a long range special at a 1500 lb AUW. And then again after dumping from the 1300 lb AUW aircraft a 180 lb not very bright passenger who objects to all this theoretical fiddle-faddle. No you will be able to work out rates of climb for ever and ever.

The same formula applies to the climb of a snail up a garden plant. If you weigh the snail, measure the vertical distance travelled and the time taken (in minutes), you can work backwards and get the Tractive HP of the snail. Similarly, railway trains on up gradients. the hoisting speed of cranes unloading container ships and your car overtaking a semi-trailer up a hill, they all relate to exactly the same formula that we have used for rate of climb on our dreamship. So think carefully before rubbishing this formula.

If the aircraft has too much drag, in the shape of struts, open cockpits (the original aeronautical handbrake), large fixed tricycle gear and so on, it will have less top speed land (and a higher lift coefficient) at maximum Thrust HP than if it were a sleek streamlined job. Also at any lower speed the draggier aircraft will use more of its Thrust HP for sustained level flight. So there will be less Excess Thrust HP available when the throttle is opened, and rate of climb will deteriorate. Hence this section’s heading, a bit of drag can begin to weigh you down.

Up at the Top End

You can begin to relax. But first we have to introduce the last formulas, for the time being, because they are associated with horsepower and its manipulation into dream-ships.

At any given steady airspeed the following formula applies:-

HP required = ( D x V ) ÷ 550

Where

D = Drag in lb.

V = Velocity (speed) in feet per second. (We are back fps now)
550 = 550 ft lb per second for one HP.

For powered aircraft the HP required is Thrust HP, what the propeller is producing at its established efficiency for the particular condition of flight. Gliders get it in an elegant roundabout fashion by using gravity, well known for its reliability and freedom from ignition problems, carburettor icing, or out of track propeller vibration. The introduction of another much used and necessary term is also required. This is the Lift to Drag Ratio, usually abbreviated to L/D. This also varies with airspeed, and with type of aircraft. Sailplanes with their high aspect ratio wings get L/Ds of over 40.

At the moment we are only concerned with the L/D at the top end of the speed scale, as a useful research tool for dream-ships. Here we will be battling to get L/Ds of more than seven which, if you follow the recommended homework practice, you should be able to confirm.

Later in these articles we shall take a more comprehensive look at L/D ratios but, for now, we will go back to our 1300 lb AUW dreamship to keep everything cosily in the same family. At top speed I’m going to suggest an L/D of 5.7. Our friendly local prop carver again swears blind that the same climb prop, still looking like a souvenir from the demolition of an Ancient Order of Buffaloe’s hall, will at top speed excel itself with an efficiency of no less than 78 per cent. So our 100 Shaft HP engine can be relied on (we hope) for 78 Thrust HP, Juggling algebraically with our D x V ÷ 550 formula, we can re-write it as:-

V (in fps) = ( THP x 550 ) ÷ D

The drag will be 1300 lb divided by 5.7 (the L/D ratio) giving Drag = 228 lb

The THP is 78.

So V (in fps) = ( 78 x 550 ) ÷ 228

V = 188 fps = 111.4 knots.

This is not too far off the 112.3 knots we got in the previous article, so we must be doing something right. We are. We’re working with formula that have stood the test of time since balloons were interceptor fighters. But we are also taking some rather daring tight-rope walking short-cuts in getting to this dizzy pinnacle of achievement. Just enjoy your triumphant sense of accomplishment. You are now getting better views quicker than all those well meaning enthusiasts who sniff at ‘not practical’ theory and, from observed evidence, cheerfully spend years and years and years not completing relatively simple aircraft. Must be a lesson there somewhere,

The homework is to use the D x V ÷ 550 formula on the quoted top speeds, AUW and engine powers of piston engined aircraft (jets are another ballgame), and extract likely figures for L/D and/or propeller efficiency. In a few hours you will have a stash of data you can use as a basis for any reasonable dreamship. You will also have segregated quite a few where the published performance figures might have a historical association with Ananias.

What About All Those Curved Components?

A whole article supposed to be about dreamships? With not one mention of the fascinating choice in vertical tail surfaces between the round one of the Pitts, the angular one of the KR-2, or the all-moving one of the VP-IA? There are two good reasons for this, Firstly, I don’t know the answer. Secondly, any attempt to outline the standard stability background would, quite rightly. ensure that Airsport readers and typesetters would co-operate in forming a lynching party. Eyeballing is OK for dreamships, unless you are so way out that you’ve schemed up something which isn’t a copy of what has been done scores of times before. Also reflect on the number of aircraft which, over the years, have exhibited change between Oshkosh and the marketing of drawings.

This series is about dreamships, but it isn’t about pretty pictures. You can rent those at the video shop. Will someone please send me some dreamship drawings to add an air of artistic verisimilitude to these otherwise bald and unconvincing narratives (which are narrowly missing reference to Mikado locomotives here). This series is condensed down to about one tenth of what any book would occupy, if there were any books of a similar introductory nature.

Dreamships have to be taken seriously. That is where our future amateur built aircraft are going to originate. The subject is too important to be trivialized by over simplification. There are no parts in these articles, even what may appear as digressions, which are not aimed at safe and satisfactory dreamship development.

There’s a fair bit to go yet. There is also an African proverb which says you eat an elephant one bite at a time. What is more, they say, that is the only way to eat an elephant.

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