Sizing electric motor for airboat / flying boat

Found these on the internet the other day

http://www.youtube.com/watch?v=Ogp9VgKejSY

From what I have found they use anywhere from 55hp motors (gas??) up to 105hp (two stroke) and 65knts max

http://www.flying-boat.com/engines.php

I found an electric trike (w/o the boat) it is much lighter and only one seat. They are using a 18HP 90% eff. electric motor that with a 53" prop and direct drive produces 140lbs of max thrust. A 63" prop using reduction drive to 1800rpm produces 155lbs.

http://www.electraflyer.com/trike.php

When looking at literature from electric propulsion companies (i.e. solomon) they generally claim that you only need about 1/4 the hp of diesel for a prop in water. Does the same apply out of the water in the less dense air???

Note: max thrust #'s were not given for the "boat" using the 102hp two stroke so I can't compare.

Please disregard the energy storage issue at this point.

Thanks in adv.

 

solomon claims are nonsense.

In some variable output situations electric has benefits over ICE but shaft power is shaft power no matter who or what is spinning it.

So if you have correctly sized prop ICE hp is exactly same as electric hp.

however 1kwh in batteries weighs quite a bit more than 1kh in diesel fuel....