Wing Area + Weight = Thrust (How Much?)

[flyheavy]

Can someone tell me the minimum amount of thrust I will need to fly a twin engine sea plane (Widgeon G-44 1/5 scale) having a wing area of about 1100 square inches and weighing about 30 to 35 pounds. A good rounded up estimate will be sufficient, and maybe an engine suggestion....

[nmasters]

It actually depends on the lift to drag ratio but generally the minimum static thrust needed to climb is ¼ the weight of the airplane. That's what full size airplanes usually use because certified engines are so expensive. It'll work for a model but performance would pretty insipid so models usually have from ½ to 1/1

[adam_one]

Can someone tell me the minimum amount of thrust I will need to fly a twin engine sea plane (Widgeon G-44 1/5 scale) having a wing area of about 1100 square inches and weighing about 30 to 35 pounds. A good rounded up estimate will be sufficient, and maybe an engine suggestion....
Besides a minimum thrust it's also important to take into account the stall speed.
For a sports plane, the prop pitch speed should be > 2.5*stall speed.
Based on your figures, the stall speed of your Widgeon G-44 may be around 40 mph.

[BMatthews]

I'm not up on my Giant Scale stuff but when I run these numbers through Foilsim I get that 1100 sq inches wants to stall at around 35 to 38 mph even at 30 lbs. That strikes me as rather high which sort of confirms my thoughts that this model is heavy even by giant scale standards.

Any chance you can keep it down closer to 20 lbs for a 30'ish mph stall speed?

[vintage1]

Heavy it certainly is, I'd hope for no more than 10-16lbs at that sort of wing area for a scale subject.

But I can't think that its as high as 38mph surely..oh..it is too. I checked.

So its gonna be a bloody racing hydroplane to get off the water at all. Probably not safe to lift at much under 45mph.

I can't help thinking there is no right answer to this one. Waterplanes need a huge amount of thrust to lift off. Far more than they need to fly..that usually leads to a nasty amount of excess power just to get off, and then an ill matched prop for the cruise.

There is something fundamentally wrong with the whole design.

It ought to be around 10lb or so, TOPS not 30lb.

That would get takeoff speeds sub 30mph.