The SAAF Forum

Irfanview is my favourite also - but this particular drawing stubbornly refuses opening by anything. I think it may be one of those peculiar CADS that came out in the eighties that produced alleged .dwgs but were in reality a format unique to the program that made them. Date on the file is 1992. I have it in a collection of odd drawings - including one of the shuttle - and they may have been given to me by somebody, I've forgotten. Half never worked.

Just downloaded a number of drawings from:
http://plans.am.free.fr/
which is still running after all of these years!

None are too exciting but the MkIX one is not too bad.

Okay this is how we do it when designing microlights:

Hopefully you have an accurate set of scale plans. What you do is take a plan view of the wings and because it is not an elliptical wing, you draw a bisecting line from wingtip to wingtip at the widest point. Now divide the wing into spanwise rectangles, say ten of them (or use the ribs as the rectangles) and calculate each blocks area, L x B, those above the horizontal bisecting line as well as those below it and then add them up. Multiply this total by 2.2 to get the area in square feet or square metres. Repeat this exercise with the horizontal stab as well as the vertical stab and add their total areas together with the wing area labelling as Wing tot. Do as many rectangles as you can to get a more accurate area.

Take a side view as well as a plan or top view of the fuselage, drawing rectangles along from the nose to tail with one in each contour change so that you get as many blocks as you can. Add the top view rectangle areas and label as Atop. Do the same with the side view, naming this total as Aside. Calculate the total area with the following formula:

Sfus= 3.4(Atop+Aside/2)

Now add this total to that of Wing tot and hopefully you will have a good guesstimate of the total surface area.

Mac

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You'll probably need Autocad to open them.

Mac

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Oh wow! Really?

As opposed to whatever CADS is.

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CADS. Hmmm. Tough one that. I have on my machine AutoCADS, TurboCADS, VisualCADS and CADS.
Wonder that they do and why I have them.

@m4rek: Okay after using lots of spookpiss i finally got my trommel open and have what I was looking for, an article on calculating irregular shaped areas, i'll pm it to you. It uses Simpsons rule for irregular area calculation.

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A zoologist I know once had to measure the wing areas of dozens of bats - she traced their outline onto standard printer paper, cut out the shapes then weighed them. Apparently the 80g/sqm "thickness specification" of standard office paper is remarkably precise.

Interesting technique. I like it.

I am willing to bet that the final figure arrived at will be close to 90 square metres. Maybe a little less but probably more.

What're we betting with, as I want to bet lower... Plus the smaller it really is the less it costs and the less work it is

From Raymer (http://www.aircraftdesign.com/)

fuselage wetted area estimation.

S(wet) = K (A(top) + A(side))/2

S(wet) is the wetted surface area
A(top) is the area profile as viewed from above
A(side) is the area profile as viewed from the side
K is pi for an elliptical fuselage
and 4 for a square fuselage... typically value is 3.4

for the wing(s)...

if t/c < 0.05
S(wet) = 2.003 S(exposed)
if t/c > 0.05
S(wet) = S(exposed)(1.977 + .52 t/c)
the S(exposed) is the planform area as viewed from above

Plug the numbers in and tell us what your answers are.

If I eliminate the spinner, the radiator, the exhaust stubs and the canopy structure, the aerial mast and all glass on the actual aeroplane (non-canopy glass) I can get it down to just over 81 square metres. Even then my calculations only get 44.95 sq metre for the wing while in actual fact they are 45.34 sq metres.

Could this error come from the u/c bays?

Also I realised a gaping hole in my theory... I need to overestimate at any rate, as I'll lose material from cutting curves out of it...

Do you think I can call it 85 sqm for estimation purposes? I will of course need to do a more accurate examination before I can give a final figure, but for estimation alone...