I agree that saildrive and harryproa may be problematic combination. I have thought about it but found no satisfactory solution. Plenty of less than satisfactory solutions I have figured though :)
Regarding the servoprop the boat at the show had one. Owner said that the only problems with the system had been teething problems with the servoprop. With the previous folding propeller he had no problems at all. And the system is smaller and lighter than the diesel option. The 22 kwh battery takes the same space and about the same weight than the diesel tank of the boat. Oceanvolt motor is significantly smaller and lighter (about 45 kg full weight) than the diesel so about 150-200 kg weight saving. Adding a small diesel generator still lets you go with less weight in the system. And also you can build the system so that the boat house battery is for other power loads is only one lithium battery charged from the main traction battery you will save some additional weight.
If you think of the weights:
The 22 kwh battery equals the diesel tank of about 150 litres.
House battery one 15 kg lithium battery instead of 100 kg of AMG (equals about 400 Ah AMG).
Electric saildrive 45 kg instead of diesel with starting battery at about 250 kg.
Weight saving of 290 kg. Installing light generator and you still have saved about 150-200 kg.
Arto
On Friday, August 30, 2019, 02:05:47 AM GMT+3, zangy.zing@gmail.com [harryproa] <harryproa@yahoogroups.com.au> wrote:
I'm definitely a fan of the oceanvolt installations that I've seen and believe it could be a great option for a harryproa. Their ServoProp actively controls the pitch of the propeller blades which improves regeneration efficiency, prevents runaway damage at high sailing speeds, makes reversing much more efficient (possibly a fixed direction installation could be effective for motor sailing in both directions), and also gives the option of setting the blades neutral for minimal drag while sailing even with the prop always in the water.
The question becomes how do you mount a saildrive unit on a flat bottom proa without requiring beaching keels. Could you put the whole unit on a swinging leg mount on the beam? A sort of well under the lw hull? Leave it fixed and keep very large tires to protect it while beaching and a small skeg to protect it shallow waters?
Does anyone know how efficient the OV ServoProp regeneration is in reverse? I could imagine that regen in reverse may actually exceed regen in forward operation due to the prop curve being optimized for forward propulsion.