well folks i am trying to make an agtractor cropduster from scratch. i have three views and dimensions. what i need to know is if it will fly when i get done! i am doin it in 1"=1'
the wingspan will be 58" but the cord will only be a lil over 6" it has a flat bottom wing and i just don't know enough about airfoils to know if this will work. also i need to decide on the airfoil to use. i want to make it slow and maneuverable just like the real ones are. yes i am goin to try to build a sprayer for it too! here is a top view of it as its shown on their website

thanx
john

It will be difficult to make a plane that small fly "slow and manuverable". The wing loading will be kinda high.
For the airfoil anyway, take a standard Clark-Y, and make it about 15 to18% thick. It's normally 11%.

Geez, that's only 350 sq inches. If you want it to be slow and maneuverable much like a glider or Old Timer then you won't want the loading to go much above 12 to 13 oz per sq foot. That means the model weight will have to come in at around 32 or less oz. That's not going to be easy. We are talking totally built up with formers and sticks or very thin sheet and small engine and radio stuff to keep it under control.

Even if you relax the slow flight requirement and boost the loading to 15 oz/sq ft and cheat up the chord to 8 inches you still need to keep the weight down to no more than 3 pounds. Now that's doable with care if you have done any light weight design stuff in your past but if not then it won't be easy.

You sure know how to pick the hard ones don't you....

somebody has to do the hard ones i guess huh! thanx for the replies

john

add lightness everywhere, 58" by 6" looking at the pic that just doesn't look right, you can add a bit of chord without it looking wrong unless you want scale. but at that higher ratio it won't be zipping around the patch funfly style.
going with a fairly thick section should give more lift, and slow it down, giving it the right feel, but using the right gear and engine you might just get it right.

my tips... micro gear, and forget the D box, on flat section you can go to an italic D, the top spar is in the normal posistion, the lower is further forward. first benifit is less sheeting hence lower weight, i think i had shear webbs, forget now, too long ago, but the wing was super strong and didn't warp at all. any design i did now with flat bottom would inculde this feature.

think light, enjoy the build and flying, however it turns out.

id be worried about that thin chord twisting while you fly. the dimentions sound about right if you conside the whole wing as 50+ inches and the chord as 6 not just half the wing.

The span is too short, lengthening it will not hurt.

The airfoil I recommend is the NACA-2412. It is what the Cessna 150, a very venerable aircraft uses. Also, it is the airfoil being used on the RP4 Rensselaer composite bushplane. I can send you pictures of the scale R/C model, if you'd like. Another way to reduce weight is with compsites. They're very easy to make, especially for flat fueslage panels.

Lastly, I am designing a "water bomber" for the AIAA's Design/Build/Fly competition. I can help you with sprayers and such.

But my first recommendation is to lengthen the span and add a 2 or 3 degree dihedral. This will give you the stability you need.


Ed Gorcenski
Aeronautical Engineering
Rensselaer Polytechnic Institute