I am just finishing up a scale bird (FW 190) that has come out on the heavy side. I am concerned about wing loading. What is the general rule of thumb about wing loading, i.e., what is considered a safe oz. per sq. ft.

My airplane has a wing area of 841.6 square inches which equals 5.84 sq feet. The airplane weighs 13 lbs (208 oz.) That gives me a wing loading of 35.62 oz. per square foot.

The aircraft is powered by a Saito 1.30 twin.

I'm afraid to try to fly this thing until I get some comfort that the power is sufficient for the heavy weight, etc. I realize she's gonna land a bit hot but just so she'll fly OK.

I'm entering the airplane in a scale event in one week and would really appreciate some opinions or expert advice!

No, there's no way to lighten it!

36 oz/sq ft is gonna be a handful. Definitely need flaps for a reasonable landing speed. You didn't say which manufacturer or plans you used, so I don't know how prone your model will be to snap rolling if you stall her-some are worse than others. If you'll identify the plane, there will be folks here who can give you first-hand info. Don't rush the lift-off, and mentally review your spin recovery technique, just in case. There's a great article on this site under "techniques" , I think, on scale flying. Might be worth a look.
Good Luck,
John

Thanks! That's what I was afraid of. The aircraft is from Giant Scale Planes. It's an ARF but an unusual one. It has a fg fuse and sheeted foam wings. I used fixed gear. The only real weight I added was a scale cockpit and pilot. The 'advertised' weight of the airplane has a top end of 10 lbs! I thought by using the twin on the nose I'd avoid a bunch of extra nose weight but it still took almost a pound up there to balance it.

Flying off our grass field certainly isn't going to help the accelleration on takeoff either. I do have flaps on it and intend to use them. As far as snapping...I'll just have to keep my fingers crossed. Definately will balance a 'tad' on the nose heavy side for initial flights!

I'll check out the other forum! Thanks again!!!

Jim

If a plane has a wing loading of 35 oz/sqft, it has to fly 20% faster than a plane with a loading of 25. Otherwise it flies the same. If you are used to landing at say 20 ft/sec with a loading of 25 then you need to up it to 24 fps with a loading of 35, not a big thing. But you must fly it faster - it is not an option and it feels different for a while.
The heavy loading doesn't affect the tendency to snap other than the speed at which it occurs. As a wing slows the angle of attack required to generate enough lift to hold the plane up increases until it exceeds the stall angle, then down it comes. Heavy planes hit harder and usually break more.

Thanks for the info. It certainly makes perfectly good sense. The airplane in question also has flaps. I guess some flap deployment would help with the landing speed (?).

I ran a couple of tanks through the Saito 1.30 Twin today. It seems to have plenty of thrust to fly the airplane just fine. I'm going to 'lose' the dowel rod elevator and rudder pushrods today and change them out to 3/8" square balsa. That should help the tail heaviness a little bit and therefore require less additional nose weight. The Saito tends to go really 'wet' at idle and one of the cylinders wants to 'blow out' (glow plug) if you let it idle for more than a few seconds. Since I need nose weight anyway, and the only onboard ignitions I have are for single cylinder engines, I'm going to mount a "D" cell alkaline as far forward in the fuse as possible and simply put an on-off switch on it to keep the plugs hot at all times.

After going to the field today and talking to two of our members that fly in Top Gun, I am more encouraged. They said they saw no reason why she won't fly alright but would be hot on landing as you said.

I have attached a pic of the airplane.

Thanks Again!!!
Jim

Jack is exactly right; an airfoil doesn't know how much the plane it's attached to weighs. Airspeed and angle of attack are the only things that matter to it. A wing, however, often has what is called wash out- which means that the angle of incidence relative to the fuselage is smaller at the wing tip than at the root. This ensures that the local angle of attack at the tip is less and therefore any stalling will begin at the root and progress out to the tip. This is good for a number of reasons. If the ailerons are outboard, as with most scale airplanes, you can detect the stall while you still have some aileron authority left and can recover before you loose control. Tip stalls are nasty because your first indication is usually a flash of adrenalin as your plane departs from controlled flight. I mentioned snap rolls because they're a common consequence of a wing without washout that gets stalled. Some models don't have any- don't know about the GSP.
Easytiger has some chilling stories about his Marutaka Raiden which had a similar high wing load. Don't remember the thread, though you could search on Raiden.
If you know all this stuff already, please forgive my pontification-- I'm an old IP, and we are forever explaining how to build clocks to people who just want to know what time it is---just ask my wife!
John

Haha. No problem about the clock John! I do know about washout. Unfortunately the GSP FW-190 doesn't have any. It sure would help in this case!

Thanks so much for the reply. ALL advice is welcome. I've been flying R/C since 1962 but there's always something new to learn!

Jim

Sounds like we're the same vintage! My first RC was a Jr Falcon with a bang-bang rubber band escapement and a one-tube receiver. Passing taxi cabs would shoot it down!
Let us know how she flies.
John

Pretty close. My first R/C was a rubber band wound escapement. Push button once for right and twice for left rudder...as I recall. I don't remember what kind of receiver it was. I went to galloping ghost from there (which I could never make work right!). I then broke down and got a used Kraft 4 channel for some outrageous price! I bypassed the reeds era altogether.

I'll let everyone know how the FW-190 flies....or doesn't ;-)

Jim