Topic: Designing and building my very own plane.

Ok..so i had this thought..how hard can it be to design a plane.So thinks i..what does it need.

1. A fus
2.A wing
3.A rudder
4.Ailerons ( spelt wrong...spelt correctly...See me after class)
5.Elevators
6. wheels
7.A prop
8.An engine
 and all the gubbins that go inside it.

sooooooo..first step.

Fus. So thinks i... piece of paper..draw a long rectangle to start with.. now, looking around at all the planes dangling from the shed ceiling, on the racks on the wall, and stood up on the floor... the fus can be different shapes..thick at one end..thin at the other end..but where should it start to taper off thinks i?? No idea..so thought id ask you lot. Thats my first question.

Next i thought..the wing... they can be straight, curver underneath, curved on the top..flat..etc... but how do i calcuate the size of wing i need for the size of the fus?

thats my next question chaps!

Rudder... does it have to be a particular shape? a particular size? or can it just be how big i want it to be and how in proportion to the wing and fus does it need to be?

a few questions there..sorry.

( numbers 4 and 5)   they seem pretty straightforward... so i dont need to ask anything there.

The undercarraige... now, i have seen lots of different undercarraiges, but what exactly is the best material to make them from, and also, does the size of wheel play an important part?

The prop i know is in proportion to the engine..so again... that is self explanatory.

Engine..now this again, i believe is dependant on size of the plane.

I have been drawing some rough sketches of a fus... but obviously i would like it to be an individual plane, a bit out of the norm so to speak.

so chaps.. i have come to you far more experienced builders and flyers than me and are asking for all your help and good advice on how do i design and build my very own plane.

Many thanks for reading this very probably daft idea that i have, and i look forward to reading your replies.

Maz

It's not a daft idea at all! To me it is natural progression from flying, assembling ARTFs, building kits and from plans and it will help your understanding of flight!

Well, you could study this or I'd suggest starting by using this basic guide.

I think it gives good ideas for most of the questions.

Just remember that these are guidelines, not hard and fast rules, but the closer you stick to them the more likely it is to fly well!

HTH.

Richard

I think you should take up fishing.......

Blooming eck..that first link will take me a while to understand..the basic guide is ace..


umm...

whats wing chord


Fishing John??...wont catch me going near worms!!

I seem to recall the following information given to me at a club meeting many many years ago. Everything is as good as I can remember, so draw out the proportions and see how it looks, they may need slight adjustments!

All the model dimensions begin with the Wing Chord ( leading edge to trailing edge distance ), So for example, we'll choose a 10 inch wing chord.

Distance from Prop Driver to Wing Leading Edge = 7/8 chord ( example = 8.75in )

Distance from Wing Trailing Edge to Tailplane Leading Edge = 1.5 chord ( example = 15in )

Tailplane Chord = 1/2 chord ( example = 5in )

The Wing Span is a ratio of the Chord, approximately 5:1 to 6:1 ( example = 60in )

Wing Area is Chord x Span = 600 sq in

Aileron Area = 8-15% of Wing Area ( example at 15% = 90 sq in = 45 sq in each aileron )

Tail Area = 15-25% of Wing Area ( example at = 120 sq in )

Fin Area - 10-15% of Wing Area ( example at 10% = 60 sq in )

Elevator Area = 25-40% of Tail Area ( example at 25% = 30 sq in = 15 sq in each elevator )

Rudder Area = 30-50% of Fin Area ( example at 40% = 18 sq in )

After you have these basic sizes, you can fill in the aeroplane shape to suit your preferance, and choose and engine based on a similar sized model you know flies well.

There's much more to it than just this, as some planes have a very long tail ( ie pattern aerobatic ), and some bi-planes have quite a short tail. The shorter the tail length, the larger the tailplane needs to be to give the necessary pitching authority.

I'm sure there will be plenty of others who will chip in, but at least this is a start.

Steve

Slurp is now designing ailerons, rudder and elevator... In a previous life she had 'flappy bits attached to the wing/the upright thing and the bit that's flat at the tail'  Whatever it is, it'll fly,hopefully without bits of twig holding it in situ.  ...What about a slope soarer Marian?

Wasn't it the great R.J Mitchell who said 'you can read lots of things about aircraft design, most of it bo**ocks?' Or words to that effect?

For me, this is the most rewarding aspect of the hobby.

To see something take to the air and fly well, and know that you designed and built it gives tremendous satisfaction.


Theres many ways of doing an 'own design'. You can start by reading lots of books and trawling through pages and pages of t'internet, but most of it you will pick up through experience.
There are a few good books out there and i have a couple for pointers and picking the right aerofoil section, which can make or break a model (literally!)

A very technical method that i have used with great success on many own designs is known as TLAR, or That Looks About Right!


First you need to think what type of model it is that you want to design, fast or slow? sedate or aerobatic? what types of aerobatics? whats the engine you plan to use?

I usually start with seeing what engines i have spare and then this will decide the size of model i can build without having to buy another!

Then i would look at similar sized models, either in the model rags or look for inspiration on the 'net and try and work out rough dimensions for it (span, length, target weight etc).

Once i know the rough sizes of the thing, i can sit down with a roll of lining paper and my french curves (ooh la la) and sketch up some pleasing fuselage profiles. Sometimes it helps to layout your engine and  gear on the drawing to bring it to life and make sure everything will fit.

I draw a line straight through the middle of the fuz, from the tip of the spinner to the end of the tailplane in red marker (this is your Datum).

For most of my stuff the wings and tailplane are 0 0 incidence, with the engine having various amounts of downthrust depending on choice of wing section.

After i have drawn a nice fuz shape from the side, i do a drawing from the top (plan) and work out how thick it needs to be to fit the gear and how much taper etc.

Wing next, although this would have been considered whilst drawing the fuz up aswell.
I usually draw up an empty box of the wing planform (L.E, T.E, tips) accurately and then work out how best to build it afterwards.

Judging by the size of the wing i can then design the tailplane. Nothing technical, just whatever looks right. I dont use a rule of thumb.


When you have the shape of the model and you are happy with it, you need to work out how you are going to turn sheets of balsa into that shape youve just drawn.


Work out what thicknesses of balsa you want to go where, and how they are going to interact with the adjoining piece in a 3D sense.

Wings can be foam and sheeted if you can get someone to cut them for you, or built up (usually lighter) or a combination of the 2. Steer clear of Vac- bagging and other composite methods for this one!

Remember that weight is the enemy of the aeromodeller and that every piece of timber you cut needs to be strong enough for the job, without being over engineered (AKA heavy).

Dont be afraid to cut holes in things, but do take into account flight loads. You wouldnt want to cut massive holes bang in the middle of your tailplane, because it would probably fold in the air, but a few smaller ones nearer the tips wont hurt.
Ribs can be lightened if you are going the wooden wing route, and the same with fuselage formers.


After you have chosen your wing section and drawn it to the size you need, youll need to decide how many spars (depending on type of model) how much sheeting (just D-box, cap strips, T.E, or all over) etc. The you can draw all this out on your plan.


Typically, a common D-box style wing will have 2 main spars, one top, one bottom.
Ribs will be every 4" or so, with maybe more towards the middle or around a servo bay, U/C mounting etc.

It will have a L.E (leading edge) of some sort, this can be preformed stock, or shaped with a razor plane.
And it will have a T.E (trailing edge), this may be square or tapered, depending whether it has ailerons (flappy bits!) or not.

This will then be sheeted from the L.E back to the top spar, and also underneath back to the bottom spar. The T.E is also sheeted with usually about 2" of timber and the cap strips join it all together and make it look neat.

Vertical grain sheeting (known as shear webs) are also often used, mostly around the centre section, where the flight loads are at their highest. These are pieces of balsa usually the same thickness as the sheeting, and they are bonded to both the top and bottom spars, with the grain running vertically, between ribs.



The fuselage can be sheet sided to keep things simple, with formers made of liteply or ply.

Triangular stock is best added down the corners of the fuz, this makes things a lot stronger, and enables you to sand things nice and round, which also saves weight and looks better

Ply should be used for F1, which is where you will be attaching the engine mount (assuming not electric?).


As i said, i keep everything at zero to the big red line running down the middle of the fuz drawing. If you get this bit right, and your C/G is in the right area, you are likely to produce a model that flies.

the fus can be different shapes..thick at one end..thin at the other end..but where should it start to taper off thinks i?? No idea..so thought id ask you lot. Thats my first question.

The fuz can be any shape you fancy ( within reason!) as long as it holds the bits together at the right angles. They usually start to taper just behind the wing

Rudder... does it have to be a particular shape? a particular size? or can it just be how big i want it to be and how in proportion to the wing and fus does it need to be?

a few questions there..sorry.

Usually this gets drawn up when im drawing the fuz, depends totally on the type of flying the model is intended for and whether you need a movable rudder or just a fixed fin?
As for height and area of fin/rudder, whatever looks right. Better to have too much than too little.
If its too little, your model will be unstable and more likely to suffer from nasty spins and bad habits. It may not even fly at all!

Next i thought..the wing... they can be straight, curver underneath, curved on the top..flat..etc... but how do i calcuate the size of wing i need for the size of the fus?

thats my next question chaps

Again this depends what type of model, what type of flying etc etc.
A typical sport wing section is whats known as semi-symmetrical, and about 20% thick.

This means that if you have a wing chord of 300mm, your wing will be 60mm thick at about 33%, which is where your spars are likely to be, and also where your C/G will roughly be.

Wing chord, by the way, is the measurement from the very front of the wing, to the back. L.E to T.E
This varies with sweep and other constraints, but you will probably be building a 'constant chord' wing for your first go.



What style of model is it you want? What gear have you got, mini or standard servos? What engines do you have?

Lets get those answered first and we can help you get it right first time!




And i hope you enjoyed my longest post EVER!

Heres some of my recent stuff..........some finished, some still being finished. Theres lots more, some of the earlier ones didnt fly so well


.32 powered speedy aerobat

.50 size lightweight 3der, 199grams at this stage in the build

.12 size 3d aerobat

.10 size sporty pootler, designed and built in an afternoon, flown that evening!

Fishing John??...wont catch me going near worms!!

But you could get a bumper catch with the appropriate bait !

Blimey Dan what a monster post. I got through a whole  reading that.

Wow..i am impressed!!.Loads of information and very much appreciated.

Engine..I'm going to go with the Os 55 Max as i have one of those in my buddy and its an ace little engine.

What do i want it to do? Everything i ask of it.

My aim. Fly to music.

I know i could go out and buy yet another plane ( christ my fleet is growing.. now have a mini hype and im picking another plane up at the weekendish), But i'd like to design and build my own.As i have to admit, that i like working with wood almost as much as i like flying.

Repairing the plane i have, and will be repairing from those that have been offered to me... has given me a greater understanding of how they are built. But what i want to know and be able to do, is know why they are built the way they are.What makes one plane more aerobatic than another.what makes one slow and one fast. Hence why id like to do what i would like to try and do.Might be a long time in the making, but it doesnt hurt to research to get the know how.Plus i was thinking of making a prototype of what i would like it to look like..well..thats the theory anyway.

As a first attempt at rolling your own why not take an existing plan that is known to fly OK and draw your own design round it keeping similar sections and proportions as the original.   

My aim. Fly to music.

1812 overture..... see if you can crash in tune to the cannon fire...

1812 overture..... see if you can crash in tune to the cannon fire...

Shes saving that for the Gremlins at Binham, you will need to look out!!!

J

re the link put on by RGN -ive used the guidelines from the same website - and they work well, but then why shouldnt they. give you plenty of scope to play around as well. first one i did was based around a wing i inherited and used them to create a lovely flyer. the satisfaction when you see your own creation fly is great -best of luck with it - do we have a budding female Boddo

Shes saving that for the Gremlins at Binham, you will need to look out!!!

J

...gulp, better get on with that spare gremmy then.....

Blimey Dan what a monster post. I got through a whole  reading that.

Thanks, i hope you could all understand my laymans approach!

Engine..I'm going to go with the Os 55 Max

So start looking around at .50 size airframes and take notes of the wingspans, wing chords, tailplane sizes and moments.
In aero terms, the moment arm is the distance between the back of the wing and the front of the tailplane.
A model with a short moment arm is generally twitchier in pitch than the same model with a longer one, other factors do affect this though.

If, as you say, you want it to do EVERYTHING, then you are looking at a fairly capable aerobat. You say you have a minihype? Is that the sort of style you want to be using?

Why not start off with something a little bit simpler to cut your teeth on like a .50 size funfly (limbo dancer type of thing)

These have a nice flat bottom wing which is easy to build, a box fuz and sheet tail parts and ailerons. They are also constant chord, which means you only need one rib template.

You will be able to add your own design quirks with the fuz shape, tailplane and fin shape, and funky wingtips and ailerons.


If you want some size ideas and a basic layout and aerofoil, and then you can decide how you want to join it all together and how it will look.

Thanks, i hope you could all understand my laymans approach!

In this case shouldnt it be laywomans approach ??

...gulp, better get on with that spare gremmy then.....

So you're only wanting two flights then? She's a complete nutter with a Gremlin, you guys started it, you've been warned. All the members at our club land immediately and then run for cover when she craks the Gremlin up, pink has never intimidated grown men as much as this before. Be afraid, BE VERY AFRAID 

J

[quote ]
Why not start off with something a little bit simpler to cut your teeth on like a .50 size funfly (limbo dancer type of thing)

These have a nice flat bottom wing which is easy to build, a box fuz and sheet tail parts and ailerons. They are also constant chord, which means you only need one rib template.

[/quote]

In principle, I quite agree, but would point out the Limbo Dancer has an almost symmetrical wing (I'm just building my second), but it is dead easy to assemble.

You'll find almost anything will fly, the question really is "does it fly the way you wanted it to?"

One of my early designs was christened "The Plough" as it spent most of its time churning up parts of Yorkshire, but being EPP foam, correx and some bits of glass-fibre board, it survived everything until I decided enough ploughing was enough and scrapped it. Flight characteristics were those of a dolphin on speed crossed with a kangaroo, and with the glide characteristic of a breeze-block.

Good luck. It is great to see your own creation winging through the air.

Yes Pooh, flat bottom and semi symmetrical. It is a high lift section, and more commonly known as the 'clark Y'.

My point was that with this type of airfoil, theres no need to be messing around with rib-tabs or packers etc.

The cougar on the other hand is fully symmetrical in section, but is very different in flight.

Pete miller did a series of articles in one of the magazines either ami or rcme as i recall

RCM&E.  It's the only mag I get now and I'm about three months "behind" in reading it.  Currently half-way through the March issue (which probably arrived not long after the New Year!) and that has the second part of his series in it.

Yes Pooh, flat bottom and semi symmetrical. It is a high lift section, and more commonly known as the 'clark Y'.

My point was that with this type of airfoil, theres no need to be messing around with rib-tabs or packers etc.

The cougar on the other hand is fully symmetrical in section, but is very different in flight.

I stand corrected 

and you can almost build it without a flat surface, and certainly without using lots of clamps, blocks etc. This time around I have used a few pins, a bit of masking tape and a sheet of MF to assemble the wing, a few judicious tacks with cyano and hey presto, a straight, complete  wing in about two hours.

So to Slurp, do a simple design first, as suggested with a parallel chord wing and simple box fuz. Incidentally a useful and cost-effective tool is a balsa stripper (no, not that kind  ) so you can cut any width of balsa, any thickness up to 1/2". Much cheaper than buying ready-cut strip and you'll usually have some off-cuts that can be efficiently used up.

Incidentally a useful and cost-effective tool is a balsa stripper

Ill second that, its probably the one tool that has saved me the most money over the years.
I have the Master Airscrew stripper and its ace, uses a no 10A scalpel blade every 6 months and means ive never had to buy strip stock at 3 times the price, plus you can get all the 'custom' sizes cut!

(no, not that kind    )

whatever gives you wood

Peter Miller has written some excellent books on designing from scratch and basic aerodynamics.

A balsa stripper eh.. ..sounds like a good tool to have..shall look into that next time i go to leeds.

Loads of info here lads, and all very much appreciated.. need to do a lot of reading me thinks so i understand it all.

And whilst im thinking and planning...i shall arrange to pick up the repair jobs and do them!.

So you're only wanting two flights then? She's a complete nutter with a Gremlin, you guys started it, you've been warned. All the members at our club land immediately and then run for cover when she craks the Gremlin up, pink has never intimidated grown men as much as this before. Be afraid, BE VERY AFRAID 

J

Dearie me..you make me sound like a hooligan!!    I'm a lady dont ya know!! Ok.... i've never claimed to be a lady.... but my gremmy sure as heck eats the air and she can do rolling ciruits and get thrown about..and she can land on hedges in a perfect landing   and she makes an awesome noise when she zoooooooooooms past on full chat doing a low pass.

Anyway.....the lads dont run for cover... they dive whilst keeping a watchful eye out to see where gremmys heading

I'll be taking two or three to binham...just in case mind.... as you never know when a gremmy might bite

But you could get a bumper catch with the appropriate bait !

Charm and wit.....

Dearie me..you make me sound like a hooligan!!   

Now then,  what was it that nice Mr. Whittaker wrote in RCM&E a couple of months ago?

"Amongst all these savages a lone lady flyer, Marian Ainsworth, totally unfazed, also flew like a hooligan.... "

And we believe everything we read in RCM&E. 

Should never believe everything that you read...

Now then,  what was it that nice Mr. Whittaker wrote in RCM&E a couple of months ago?

"Amongst all these savages a lone lady flyer, Marian Ainsworth, totally unfazed, also flew like a hooligan.... "

And we believe everything we read in RCM&E. 

He was being kind and generous, in fact there are no words to describe what happens when Maz and the Gremlin become one. I think Binham and surrounding areas should board up their windows and hide their children for that weekend.

J

He was being kind and generous, in fact there are no words to describe what happens when Maz and the Gremlin become one. I think Binham and surrounding areas should board up their windows and hide their children for that weekend.

J

awwwwww  ayyyyyy!! I'll end up flying on me todd at this rate!!

In all reality, i am a most sedate, considerate, calm, flyer.. I don't stand there with a manic grin on my face or whooping and holloring that its ace..nor do i ask who was it that just dived under the van in terror... Im a nice flyer i am!

In all reality, i am a most sedate, considerate, calm, flyer.. I don't stand there with a manic grin on my face or whooping and holloring that its ace..nor do i ask who was it that just dived under the van in terror... Im a nice flyer i am!

sniff....... sniff....... yep....... no doubt about it........

BULLSH1T![/color]

sniff....... sniff....... yep....... no doubt about it........

BULLSH1T![/color]

Hmph.....

Enyway...... i have been working on this evening, on various sketches... just seeing what kind of shape i would like it to be.

All I'd offer Marion is that the more detail you think things through in, the easier it'll be to successfully build the model.

Watching with interest 

Well put Jamie. And very true.

Quick question... i installed Autocad on me lappy last night, had it on my pc but never used it and when my pc was going t1ts up i backed everything up onto here..so i installed it from my pc back up.

anyway..Autocad, can i use that to design a plane?? umm..if so...how?

I thought all the best designers used the back of a fag packet   

I thought all the best designers used the back of a fag packet   

I need to take up smoking - I use wallpaper!