I ran this question through here about a year ago. Most everyone mentioned that wing area includes the area through the fuselage. ..... except for rubber powered A/C.

Have yet another question regarding this again. I may ahve come upon yet another exception.

I have a A/C design from Russia. I have tried this way and that to make the stated wing area match what is determined via Autocad. I get real close iffn' I subtract out the area within the fuselage, and measure the area just underneath the wing-dihedral included. This hits the same for main wing and for Hoz-stab areas. The rear Hoz-stab has a healthy amount of dihedral.

This A/C is an F.A.I. competition design. Is it a Russian routine to indicate wing area as per projection or is it some competition ruling?



Wm.

FAI looks at a plan-view projection.. includes the area in the fuselage.

That's right. It's projected area so the span is forshortened in the panels with significant dihedral. If you do the area based on the flat plan it'll be too large.

Bruce.....

You are misunderstanding.

I have already measured the wing area, and if I subtract out the area involved in the fuselage, and then just the area underneath the wing when at dihedral (NOT flat), then my estimate and that shown on the plan coincides near exactly. This sort of like the older Wakefield rubber powered formulae.

Is this typical of Russian designs?

The other Russian A/C that I have do not an area cited on the plan.

Wm.

Not sure if it's typical or not but it sure sounds like the way this one designer does it.

I believe that you'll find that what Paul said about the rule book including the fuselage area is the case.

As for the plans and the designer it's possible that when he did his wing area calculation he did not use CAD and instead estimated the area of the odd shaped areas like the tips and did not include the fuselage for some reason. Your AutoCAD measurement is likely far more accurate.

Well, as mentioned, the designer did not hit my number exactly. I think he either used a planimiter or calculated it via DMD.

There is a few dimensions which run out, past the wingtip. The tips are rounded. The area comes a bit closer extending to the estimate cited on the plan if this dead area is taken into account.

I think they have a different way of measuring area.


Wm.

A planimeter? ... A PLANIMETER?! Gee wiz, I don't think 2 people in a thousand know what one of those is, much less what it is for or how to use it! That said, you are probably right. We drafter, engineer types had a lot of tools available to us that have long since been replaced by the computer. A pitty. I've got mine stored somewhere with my sliderule. I think I will take it out and knock the dust off just for fun. For those who don't know, it is a tool for measuring the area of an irregular shape by tracing the nifty machine around the parimeter.

Wing area conventions are just that, conventions. They are a bit more useful than government gas mileage stickers on new cars, but serve the same purpose. Good for comparison to that which we know works.

All the best of luck to you on your project.

BP

If you are building the airplane for FAI competition, the first worry is to see that it fits the FAI rules regardless of what the designer thought.