I have a Kyosho Cessna AgWagon crop duster; stock plane weighs 6lbs; span 69"; wing area 640 sg/in; wing loading 21 oz/sg/ft; engine YS53 fs; I have made significant Scale enhancements which includes actual working spray arms under the wings; this has brought the weight to 12lbs fully loaded with fuel and water for spraying; I have installed a larger engine a RCV 91CD fs; the dimensions of the wings are the same; my question is; will the stock wing loading/demensions be enough to lift this plane into flight with the increase in weight and utilizing a larger engine size; not looking at performing acrobatics just scale flight crop dusting. Thanks

If my calculations are correct, your wing loading has jumped up to 43.2oz/sq. ft. WOW! That is a bunch. However, it might fly just make sure you have plenty of airspeed at all times. Hope your project brings you much joy. Have a wonderful day.

In Christ,

Joel Chavez

Yes; That is what I calculated; the larger engine should provide the extra speed; any risk in the wings collapsing? or is that not a concern, the weight and loading is about double to that of stock values!

I would make sure that the area under the wing braces is strong.
Other than that, enjoy your plane.
Also remember, no negative "G" maneuvers

Flyability versus wing loading is an interesting topic. One would initially think that increasing the installed power in linear proportion to weight would do the job, but it doesn't. My calculations indicate that power must be increased far more, in fact, power should be increased to be proportional to the 2.5 power of weight, if flyability is to be kept constant. Ten percent more weight needs roughly 27 percent more power.

Some old Spitfire pilots claimed that the friendliest Spit was the Mark 1, simply because it was so much lighter than later versions. Double the power, and double the weight, makes for an airplane that is much more demanding to fly, mainly because recovering from too-low airspeed takes much longer, and thus produces much more altitude loss before the airplane is happy again.

I would be inclined to use a healthy 1.2 cubic inch, or larger, two-stroke at that weight and wing loading to get a pilot-friendly airplane; a four-stroke of similar capacity would be a reasonable compromise, for those who like four-strokes. Otherwise, it will tend to be an airplane that you fly once in a while, when you feel in the mood for a challenge.

I would also be very aware of high speed stall and a much greater sink rate when turning at higher bank angles or pulling out of a dive (as you would when you come in for a scale spray pass. Definitely keep your airspeed up. Mix some liquid fertilizer in with the water and fertilize your grass runway (might take a few passes)

Thanks for the advice; it was also suggested by some my fellow club members that I use a couple of degrees of aileron reflex(slight up flaps) to help with preventing stalls.

Good luck with that. I would love to see it. Do you have pics or could you make a video of your flight? That is one unique aircraft you have.

If it has flaps, use em! Most wings are way over engineered for scale flying, so you should be ok, if you don't horse it around too hard. If the added weight is in the wings, that helps too.

43 is a high wing loading for a 69" plane. I had a plane with numbers very close to those- notice the word "had."

The plane will be flyable, but it will have a high stall speed. Take-offs and landings will not look scale, and you will have to maintain a higher-than-scale looking speed in flight. I don't know about your structure, but I didn't have any troubles with mine, as I built it strong (one of the reasons for the high weight). Anyway, you might shy away from high-G maneuvers.

I lost mine (a Pica Cessna 182) when my engine quit on approach and I couldn't make the runway, because I stalled at around 30 mph.

dasintex,

with a few details about your wing I can tell you what its G limit is.

what spar and web (cross sectional dimensions and material) and how thick is your wing (inches) at the root?

(My father's written a useful program for calculating the max strength of wing spars)...

Yeah, with a handle like "destructiveTester", you can be sure of his calculation!

I can get those dimensions; when you say 'at the root' where is that on the wing, at the fuselage? Thanks.

Yeah the root is at the base of the wing, or the part by the fuselage. The tip is obviously at the tip of the wing.