I was doing some caculations on my extra 260 today, and was wondering if a wingloading of 31 oz/sq ft is too high? or about normal?

The plane weighs about 10 pounds with everything installed, minus gas, and has 734 sq inches of wing area.

I think you posted something about calculating wing area a while back. The number "734" stuck in my mind.

Do the root ends of the wing panels touch each other, or are they spaced apart by the fuselage?

If they are spaced by, say 8", multiply that 8" by the root chord and you will have that much more "effective wing area", lowering your wing loading.

The fuselage part of the wing actually develops some lift too.

Ah, your right, forgot about the area between the wings. That would add another 137 sq inches, making it a total of 871.

This makes the wingloading at 26 -27 oz/sq ft. A number I can better live with.

I guess I am just paranoid for some reason.... well, thats what the voices tell me anyways

Rich - 31 oz/foot is not high at all if your plane has a 90" wing span!!! Hehehee ...

its actually 72"

For a 72" 26-27 oz is nice, 22-24 oz would be medium light. I think even 31 oz is still manageable. My little Global Raven 40 had a wing loading of about 30 oz. It was manageable, no real bad habits at all. It has a lot to do with set up I guess ... careful with the CG (slightly nose heavy) and elevator throws (not too radical) and some wash out for the ailerons (aids in landing, less chance of tip stalling).

My newest twin with 2 OS .46Ax's and a 51 inch span has a wing loading of 31oz/sq ft. You can definitely notice the higher sink rate on final unless you keep a little power on. Landings are a bit fast and I would not recommend a plane this heavy to a novice. 672 squares, 9 pounds.

There is really no right or wrong way for calculating wing area. There are various conventions common in the RC airplane industry. The most popular is, of course:

Overall wing span x average wing chord.

Wing span is easy: measure wing tip to tip - that's it! Average chord is more subjective. I personally prefer:

(Root chord + tip chord) / 2

This does take the area between the fuselage into account, but it is slightly different from what Dick described above.. Unless the wing is highly tapered, though, the results are close enough for estimating wing loading. I guess "estimating" is the key word. If we truly are calculating "Wing loading" then we really should calculate the wing panel ONLY. However, most of us are actually more interested in how the airplane behaves aerodynamically. Since the fuselage does act as a lifting body at most angles of attack, increasing the wing area to include the part between the fuse is good enough of an estimate to compensate for the added "lift" due to the fuselage body. Truth is, the added lift really depends as much on the fuselage shape as its width near the wing.

To answer the original question: 31 Oz/sq.ft. is just fine for the typically 72" aerobat. My GP 1/4 Giles 202 is almost exactly that, and my GSP Extra 300 and Yak 54, both 72", look like they will also finish out about the same.

So have I calculated correctly on the Goldberg Sukhoi that I just finished?
[ul][*] total finished weight is 11 lbs 1 oz (177.4 oz)[*] There are 949 square inches wing area[*] 26.81 oz per square foot wing loading
[/ul]

The plane is Saito 180 powered.

Cheech - spot on! That is one lovely plane to fly, seen my friend fly it with only a Surpass 120 and that was lovely. With your Saito 180 its gonna be a blast for sure.

Thanks tIANci. That's what I want to hear. I'm looking forward to flying it. We're in deep winter now, so it will be awhile.

No way! That is so easy ... just add skis!!!

ha.. skis and a sukhoi!!!!!!!! That'd be a sight to see

31 oz/sq ft is not too high. My little 53.5" span Bearcat has a wing loading of 34 oz/sq ft, but it still flies great. Landings are somewhat hot though.

Iowa - why not? I sure it snows in Russia!!! Hehehe ...

This is usually where Dick Hanson says something like, "Our planes have extremely low wing loading because we learned a long time ago that 15oz. loading is the absolute most you would want."

I'll say that the smaller the plane the lower the number needs to be and 26-28oz sounds OK for a 72" plane. It's easier to build bigger because once you get into 35% and up it's easier to keep the weight managable. You don't see a lot of smaller scale planes that are good at 3D, you usualy have to have a funfly with really big wings compared to an Extra or Edge to have good wing loading. 72" AND scale is a real in between size and will do aerobatics but is hardly ever a really good 3D plane.

Basin - again try to imagine a 72" aerobatic plane with 15 oz wing loading trying to fly IMAC pattern. It will be too floaty to fly. Guess, the wing loading has to be at the optimum for its purpose. If its 3D then a 17oz to 20 oz wing loading for a 72" would be very nice. I tried some really light 40 sized planes for non 3D flying and did not like it ... Ok ok ... I admit ... I cannot 3D!!! Hehehe ...

for me it's really bad news.
in a week I will do a maiden flight to my new GSP katana 72" with the new wing.
I think that I have real high wing loading...I hope it will be eazy to fly and land (and 3D [:'(])

Meeko - my pal flew one with the MVVS160 gasser ... was a little under powered, was enough to fly and a little hairy to do any good manouvers but it was not that hard to fly. I am sure you will be fine, if you are feeling a little edgy then use 2 channels for ailerons and then set flaps function for landing. Now let the flaps move the ailerons UP and NOT down. Let it go up about 1/8", this will create some washout and give you some additional margin before the plane will tip stall. Its your safety net while you get used to the plane for landing. Try it.