"averaging 700-900 watts"
nicobie said:Impressive filament for a hobbiest looking for strength. Pretty darn pricey though.
patrickza said:After going through the whole thread I'm getting more and more excited about my catamaran conversion. The extruded aluminium mounting is such e brilliant way to put things together. I'll be at my boat next week to do the measurements, but I'm fairly confident it'll be perfect for my boat, even if it means adding an additional motor mount, or getting slightly longer shafts. I'll be at my boat again in 3 weeks, so I'll be able to do all the measurements then.
Two motors at lower power should give me great efficiency, and maneuverability too. The catamaran is 30 feet long and probably weighs between 4 and 5 tons, so two of the 47mm stator motors should be plenty. I'm planning on 3200w of solar, I think I'll be able to move along quite well just on solar power, possibly even marginally charging the battery bank at the same time!
My interest is in converting a 34' monohull. Rather than day trips, the goal is "off-grid bluewater" sailing. The major thing restricting me is the cost of (lithium) batteries. With the increase in output/reduction in cost, of solar panels, together with your direct drive REGEN motor I think it should be possible to size a battery bank at a more affordable level.
Convensional wisdom is that hull speeds around 6kts (with a 9" prop) are required to make regen viable. Your videos seemed to suggest reasonable figures could be achieved at around 4kts (have I got this right?)
The next piece in the puzzle, I think, is the efficiency of the propeller. Cracking this element would reduce the energy requirement (and hence required battery size) to power the boat when there is no wind, whist also boosting regen vrs hull speed.
You've mentioned your ability of producing prototype aluminum props, and with your load cell/torque measurement, you have an excellent "development platform". I wonder if you have considered the toroidal propellers "designed" by MIT. These seem to show significant efficiency over conversional designs. I know people are DIY 3d printing props for drones with tremendous success. Sharrow marine are also producing props (mostly for power boats, I think). The difficulty is in getting accurate figures as to their effciency - I guess your setup may be ideal, here.
Sharrow propellers are expensive, but given the potential saving in lithium batteries, this might not be prohibitive. The (potentially) improved efficiency and (hopefully) regen at lower hull speeds, could be very interesting.