I agree. I think the difference is that the added 'hull' would have to be such
a part of the original vessel as to contribute to its displacement.

Glenn Ashmore wrote:

I believe it would have to be rigidly attatched and fair to the hull to
improve hull speed. Hull speed is a function of a moving body
displacing water and the length of the wave it produces. Two bodies
make two waves. A dinghy being towed adds nothing but drag.

Parallax wrote:

For some reason, my post on this question this morn didnt get posted.


Does towing my hard shell dinghy effecively increase my waterline
length thereby increasing my hull speed?

Could you add a lightweight inflatable extension to the waterline of a
boat to increase its waterline length thereby increasing its hull
speed?