Robin
Well-Known Member
To add to Vyv's comments, our 'inherited' Brunton, which is one of the older ones with open bearings, performs very well in reverse. It is said that you can crash stop from 6kts in a boat length which I could believe but don't wish to test!
One benefit is that because the prop self pitches, it first starts whether in ahead or astern at a fine pitch setting. This means that when you engage gear at tickover everything happens gently and there is little tendency for propwalk, for example when reversing out of a berth. Once the revs build then it has serious bite and if you want the propwalk back then it is available, just give it some real welly for a few seconds then back off to what you need because this will have set the pitch coarser.
However, aside from the greatly reduced drag from the feathered prop under sail the motoring benefits are also significant in my book. On ours on a 41 footer with a 44hp Yanmar (max 3,600rpm) we get 6.5kts in a flat calm at 2,000rpm. Put the smallest amount of wind assistance even with no sail up and 2,000rpm gives 7kts because Mr Brunton pitches up into overdrive! Conversely if there is a head sea and headwind then speed will of course drop at the same revs because the prop has dropped down a gear to finer pitch, just increase the revs to regain the speed. This allows if needed the full engine HP (44hp at 3,600 in our case) to be achievable even in severe conditions when with a fixed prop it would not.
Comments about out of balance blades because of fouling would apply to any prop with moveable blades surely. In our case we bright polish our prop rather than antifoul it and we have never had any problem with fouling other than a very very few barnacles around the hub or blade roots on spring liftout, but that is after 4 months of inactivity afloat over the winter.
See pic below of the prop at rest out of the water. In the water with flow under sail, each blade self aligns to give the minimum resitance or drag.
One benefit is that because the prop self pitches, it first starts whether in ahead or astern at a fine pitch setting. This means that when you engage gear at tickover everything happens gently and there is little tendency for propwalk, for example when reversing out of a berth. Once the revs build then it has serious bite and if you want the propwalk back then it is available, just give it some real welly for a few seconds then back off to what you need because this will have set the pitch coarser.
However, aside from the greatly reduced drag from the feathered prop under sail the motoring benefits are also significant in my book. On ours on a 41 footer with a 44hp Yanmar (max 3,600rpm) we get 6.5kts in a flat calm at 2,000rpm. Put the smallest amount of wind assistance even with no sail up and 2,000rpm gives 7kts because Mr Brunton pitches up into overdrive! Conversely if there is a head sea and headwind then speed will of course drop at the same revs because the prop has dropped down a gear to finer pitch, just increase the revs to regain the speed. This allows if needed the full engine HP (44hp at 3,600 in our case) to be achievable even in severe conditions when with a fixed prop it would not.
Comments about out of balance blades because of fouling would apply to any prop with moveable blades surely. In our case we bright polish our prop rather than antifoul it and we have never had any problem with fouling other than a very very few barnacles around the hub or blade roots on spring liftout, but that is after 4 months of inactivity afloat over the winter.
See pic below of the prop at rest out of the water. In the water with flow under sail, each blade self aligns to give the minimum resitance or drag.
