Learning to Cope with a Sail Drive.

DJE

DJE

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The last boat was 3.7t and 29ft. The new one is 6.6t and 39ft so there is bound to be a bit of a learning curve. Under sail we have no problems apart from friction in the single line reef system (no problems doesn't do her credit the new boat is superb).

Under power the change from shaft drive and transom-hung rudder to sail drive and balanced spade rudder is taking a lot more getting used to. There is the best part of three metres from the prop to the rudder so the delay between opening the throttle and the wash hitting the blade is very noticeable. With helm over before putting her in gear the old boat would start to turn before she started moving forwards; the new one charges ahead and gathers considerable speed before she starts to turn. The bow thruster helps in light winds but isn't up to pushing the bow up into a decent breeze.

The biggest problem at the moment is getting back onto our berth (alongside a long mid-river pontoon) when the wind is blowing us off. I rig a spring from the midships cleat and drop it over the stern cleat on the pontoon then we motor against it. The trouble is that no amount of rudder will stop the bow turning in towards the pontoon. This is weird as I would expect the wind to blow the bow down. Increasing the revs just makes things worse. It seems that the turning couple of the prop thrust and the spring tension is always greater than that generated by the rudder. Perhaps the prop wash has become rather diffuse by the time it reaches the rudder.

I’m sure we will get the hang of it but I would be happy to hear from others who have already solved this one.
 
It will generally be the case that the rudder will only work with movement of the boat through the water. The rudder blade won't have the width to deflect the stream resulting from the prop. You'll have to be more accurate with your approach and quicker getting the lines on.
 
savageseadog said:
It will generally be the case that the rudder will only work with movement of the boat through the water.
Click to expand...

We don't find that with Ariam's saildrive.

If I want to move the stern sideways, with the boat stationary in the water, I give a brief burst of ahead. Lasting perhaps a second, and up to maybe 3/4 power (just a guess, I don't actually look at the revs, maybe it's more). Then straight back into neutral. There will then be a short delay as the lump of water travels from prop to rudder, followed by the stern lurching sideways vigorously enough to unsettle standing crew if they haven't been warned to hold on. The boat will pick up a little headway incidentally (can be checked by going into tickover astern) but it's not the headway over the rudder causing the turn.

We do have a great big Volvo three-bladed folding prop.

Pete
 
I use a midships spring. Needed to move it further aft using a karabiner on toe rail to avoid bow swinging in. Still tends to do it though and have put fat fender forward of shrouds to take the bump. So maybe the static pivot point amidships ddoesn't apply when moving forrard. Maybe you could experiment with temporary "cleat" and then install permanent one. I intended to do this but havent got around to it.
 
I find that provided I have 1/2 a knot of speed I can steer anywhere back or forwards. If I have come into a berth and my stern is stuck out to far or has blown off (so to speak!) I just place rudder hard over, burst forwards, slight delay, then she'll move over forwards and over. Then centre rudder and burst astern to stop. I have moved as little as two feet doing this.
 
try doing it with a saildrive and twin rudders before you complain! If I'm not moving, I'm not steering...
 
prv said:
We don't find that with Ariam's saildrive.

If I want to move the stern sideways, with the boat stationary in the water, I give a brief burst of ahead. Lasting perhaps a second, and up to maybe 3/4 power (just a guess, I don't actually look at the revs, maybe it's more). Then straight back into neutral. There will then be a short delay as the lump of water travels from prop to rudder, followed by the stern lurching sideways vigorously enough to unsettle standing crew if they haven't been warned to hold on. The boat will pick up a little headway incidentally (can be checked by going into tickover astern) but it's not the headway over the rudder causing the turn.

We do have a great big Volvo three-bladed folding prop.

Pete
Click to expand...

Ditto, except I have a two bladed folder. Maybe, Dave, you're too impatient?The water does take a while to get back to the rudder. Keep the engine going ahead while you wait for the turn to start and you will begin to make headway. Just give it a dollop of throttle and then go back to neutral, and you'll spin like a top without going forward (at least you will if the underwater profile doesn't impose too much turning resistance.)
 
Hi Dave
I'm seeing the same problem having sold my Sadler and now learning how to handle a sail drive must admit until reading this thread the distance from the prop to the rudder had not crossed my mind.

Hope you enjoy your new boat

Regards Derek (Ex Malgrat owner)
 
Glad to see I am not alone !

I too have moved from a boat with a shaft drive very close to the rudder, to a sail drive some feet from the rudder.

With the previous boat a very short blast of full power with the rudder over would spin the boat around the keel without moving - great for boosting the bows up into the wind in a tight corner.
Simply doesn't work with the new boat - yes will have a delayed reaction response, but boat will have moved forwards in that time - substantially forward if a significant burst of power.
And we have a good 3 bladed prop
 
As already said, short sharp bursts will kick the stern after a short delay. If turning to port, going idle astern until the bow stops swinging and another burst of ahead is required helps the turn by paddling the stern to starboard due to the propwalk. I can turn our 40' boat in her own length like this.

Having mentioned propwalk, whilst it's alleged to be minimal with saildrives, ours is quite pronounced. The way to overcome this and prevent the boat being pulled onto the pontoon when leaving a starboard to berth in astern or when needing to initiate a port turn rapidly when setting off astern is to give a BIG handful of throttle for a few seconds to get the boat moving well in short order, then go to neutral to eliminate the propwalk. Once the turn is initiated and the boat carrying a bit of sternway, astern can again be selected without a major pull to starboard.
 
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I went through a similar learning curve with our boat of a very similar size. The "kick" against the prop when scooting thrust against the rudder is delayed a bit but is still very effective, windage on a bigger boat is more of an issue. I don't have a bow thruster so have to plan manouvres carefully and if the bow bllows off I go with it rather than fight it. I've got a Bruntonton's variprop which reduces the prop kick in reverse considerably. Sometimes I wish I had that kick as it makes pivoting a lot easier ... but I like the prop feathered in light winds! Good luck and have fun!
 
Thanks all for the advice. More practice required and we will re-think our approach to the berth when it's fresh from the south west. Almost invariably it is Sue on the wheel and me handling the ropes. We put a black mark on the wheel to show when the rudder is centred and I've had a few shouts of "where's my black mark" at critical moments. She misses her tiller.

Derek, Looks like a good year for selling Sadlers!
 
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DJE said:
We put a black mark on the wheel to show when the rudder is centred and I've had a few shouts of "where's my black mark" at critical moments. She misses her tiller.
Click to expand...

Traditional, you put a fancy knot at top dead centre. Looks good and you can find it in the dark. As here...

knot.jpg
 
prv said:
We don't find that with Ariam's saildrive.

If I want to move the stern sideways, with the boat stationary in the water, I give a brief burst of ahead. Lasting perhaps a second, and up to maybe 3/4 power (just a guess, I don't actually look at the revs, maybe it's more). Then straight back into neutral. There will then be a short delay as the lump of water travels from prop to rudder, followed by the stern lurching sideways vigorously enough to unsettle standing crew if they haven't been warned to hold on. The boat will pick up a little headway incidentally (can be checked by going into tickover astern) but it's not the headway over the rudder causing the turn.

We do have a great big Volvo three-bladed folding prop.

Pete
Click to expand...
This, pretty much, but on my boat - 28hp Beta with standard 2 bladed prop. Extremely manoeuvrable even in restricted space once you get the hang of it
 
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