Originally Posted by guitarguy56
OK... understand the pitch principal on the thrust for the trolling side... I am a propulsion engineer with decades of jet turbine experience... that said... we used 'variable pitch vanes' to alter the compression and exhaust of gases to achieve maximum performance in the engines, we also tried variable pitch compressor/turbine blades, they are also used in variable pitch props on aircraft... well if the maker/inventor of the unit you devise in your last paragraph can incorporate the 'variable' part of the prop in such a way... then in the thrust mode it would operate like any regular trolling motor... push a button and it changes the pitch of the blades to the generator mode... then it might be reasonable product and many might/will be sold... the problem is the unit will look like the rotor of a helicopter to vary the pitch of the blades... very complex, expensive materials, and the loads on the the hardware would be tremendous and not make this a viable product... plus any little piece of debris on the rotor would disable it's functionality and then it's just another piece of 'crap'...
Excellent points, Nick. In the other thread, we discussed the possibility of using variable props like the MaxProp for generating. More and more sailors are opting for the expense and complexity of these things anyhow, and they do hold some attraction for hydro-gen use -- esp. as part of a hybrid driveline. The racing version of the Watt&Sea
has a hydraulic variable-pitch prop to maximize output/drag ratio across the wide speed range of 'Open' Class boats. It costs around $7500 IIRC.
Truth is, with solar PV down to ~$1US per watt and improvements in flexible films, power density, and shading compensation, that is increasingly the most attractive RE solution for boaters. As hellosailor noted, people have been trying hydro-gens for five decades without much traction. Now, as we get the boat speeds, rare-earth magnets, and composite materials that make good ones feasible, better PV has made them irrelevant. Their time may have gone before it has come.