Hi,

I want to built an airplane model capable of carrying a payload of seeds and dropping it during flight. The problem is that I don't know how the center of gravity will be affected by this.

How real airplanes are designed so they can carry stuff and drop it (say, like the Canadair CL-215) without becoming unstable after they drop the payload? Is it a function of the tailsize, to allow for a bigger CG range?

They carry the droppable payload arranged on the CG, so there is minimal CG change when the payload is dropped. The water bomber has the tank's centre of mass centred on the CG, and I imagine it is designed to drain so that the CG is maintained.

The stab is fairly large to allow a reasonable CG range, and have the power to handle the moment changes form the big flaps, scooping water, etc.

Kevin

Just make sure the CG of the cargo mass is placed within the flyable CG range of the cargo model.
Then you can drop the cargo inflight and maintain a flyable CG location.

If you have plenty of horizontal tail area far enough behind the wing, the flyable range of CG will be rather broad, allowing for a broader range of cargo location while maintaining a flyable CG.

biber