wossname

I'm building a hovercraft and I need to design the rudder assembly.

I need 2 vertical rudders which are fed by a 9 inch prop which is about 7 inches away from the rudders.

I will be mounting them onto a plain flat area of 6mm plywood (pretty sturdy!). There will be plenty of space to put the servo.
The problem is, I have never tried to make rudders before so I need a few pointers please.

Should they be aerofoil shaped or will flat panels work? I'd like to have them attached at their base only. the top ends should be free How can I achieve this?

BMatthews

It can be done but you'll need a couple of very strong hinge posts mounted to the base to serve as mounts for the rudders to withstand the blast and vibration. Something like 3/16 or 1/4 round steel rod would work. If you need it lighter then carbon fiber rod or thick wall tubbing could be used. It'll need to be secured in a properley supportive base block as well. The rudders could then be made up with an aluminium tube at the 25% chord point so that they slip down over the posts. The simple way to make them would be just glue some sheet balsa onto either side side of the tubing and sand to some decent shape. Or you could add some ribs and bend some 1/32 plywood over it all. Whatever fits your tastes. For a simple air director such as this anything that sort of looks semi streamlined will be fine. Even simple slabs would work but not quite as efficiently nor would they look as "finished".

The strength will definetley need to be in the mounting of the hinge posts. There's going to be a lot of force and vibration on those posts from the air blast and they need to be stiff enough to not flex or the hinging will tend to bind and load the servo.