2020-01-28, 01:02 AM
I also considered sheet to tiller electric autopilot hybrid ideas.
For regular sheet to tiller using elastic I have a few concerns:
1) More chafe on the rigging especially downwind depending on sea state.
2) efficiency, both steering straight and limiting sail combinations that are otherwise faster but not very balanced
3) need to adjust as wind speed changes and change the arrangement completely depending on wind angle.
Now obviously some boats are much more balanced than others, and with crabclaw and other rigs, it has been shown there are arrangements that mitigate adjustments for wind speed changes. On these boats, using a sheet to tiller arrangement the above issues are minimized but never really fully eliminated. Even wind vane suffer from the above compared to a sufficiently strong autopilot, but tiller pilots are generally fairly weak compared to a wind vane in terms of power.
The idea of using an electronic tension meter on the sheet to aid the autopilot is probably a good one, but the measurement from this is overlapping with other measurements already available like wind direction or compass heading. It could potentially provide valuable input but utilizing this in the best way probably needs an automatic tuning or learning algorithm.
One idea for a sheet to tiller hybrid is to have a very small motor with a large gear reduction that adjusts the bungee tension. The idea here is the autopilot would react to changing conditions rather than course changes. It might also react to very large course errors to help the system steer straighter. This would help the situation but is really not enough since you can also adjust where the sheet attaches (near or far from rudder shaft) as well as the strength of the bungee, not just the tension. To have the best setup might require several small motor to adjust these.
The same system could be used on a windvane/autopilot hybrid. Rather than driving the oar with a motor, the motor would rotate the air vane, and another motor could adjust the helm (offset between pendulum oar and main rudder) These motors also could be tiny, something like geared down rc servos.
The filter might need to be a lot lower and the power consumption would be minimal.
For regular sheet to tiller using elastic I have a few concerns:
1) More chafe on the rigging especially downwind depending on sea state.
2) efficiency, both steering straight and limiting sail combinations that are otherwise faster but not very balanced
3) need to adjust as wind speed changes and change the arrangement completely depending on wind angle.
Now obviously some boats are much more balanced than others, and with crabclaw and other rigs, it has been shown there are arrangements that mitigate adjustments for wind speed changes. On these boats, using a sheet to tiller arrangement the above issues are minimized but never really fully eliminated. Even wind vane suffer from the above compared to a sufficiently strong autopilot, but tiller pilots are generally fairly weak compared to a wind vane in terms of power.
The idea of using an electronic tension meter on the sheet to aid the autopilot is probably a good one, but the measurement from this is overlapping with other measurements already available like wind direction or compass heading. It could potentially provide valuable input but utilizing this in the best way probably needs an automatic tuning or learning algorithm.
One idea for a sheet to tiller hybrid is to have a very small motor with a large gear reduction that adjusts the bungee tension. The idea here is the autopilot would react to changing conditions rather than course changes. It might also react to very large course errors to help the system steer straighter. This would help the situation but is really not enough since you can also adjust where the sheet attaches (near or far from rudder shaft) as well as the strength of the bungee, not just the tension. To have the best setup might require several small motor to adjust these.
The same system could be used on a windvane/autopilot hybrid. Rather than driving the oar with a motor, the motor would rotate the air vane, and another motor could adjust the helm (offset between pendulum oar and main rudder) These motors also could be tiny, something like geared down rc servos.
The filter might need to be a lot lower and the power consumption would be minimal.