Re: Seaplane Design: (was: Boeing B-314)

Date:         30 Nov 98 03:07:56 
From:         "David Fielding" <>
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Well...just from a few observations...

The sponsons supposedly offered less drag, and maybe even a little lift.
Boeing found in testing the 314 that the angle of attack of the stub-wings
had to be increased, which had to reduce cruise speed by a few knots. They
also found that the sponsons did a poor job of keeping the wingtips out of
the water, which was a problem on the 314s throughout their service lives.

I would guess sponsons would have less tendency to yaw the 'boat sharply if
they dug into the water. On the other hand, I have heard of flying boat
pilots dipping one tip float into the water to help in gentle turns at taxi
speeds. Wing-mounted floats are in a better position to provide leverage
against the rolling of the 'boat, having a longer moment arm; so I guess
they could be smaller, offsetting the drag disadvantage of the struts
necessary to mount them.

It seems that as the design of large flying boats progressed, the sponsons
disappeared in favor of floats below the wings. Darwin would say that
wing-mounted floats were the fittest solution to the problem, which of
course was no longer necessary to solve once the whole species became

David Fielding
"Anything is possible, except skiing through a revolving door"