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Boat Handling Under Engine, Part 2 – “She doesn’t DO reverse!”

by | Jan 29, 2020 | Archived News (Live), Skills School

In the last Skills School we discussed ways to extract ourselves from our alongside berth without undue drama. But still we’ve got to work our way out to the fairway buoy before we can stow our fenders with confidence. Continuing our series on handling long-keel boats under engine, let us begin to look at some techniques that will see us out to sea with the minimum of fuss, beginning with that nemesis of all long-keel boat skippers; reversing.

If ever you feel the need to hear some entertaining stories of daring do and lucky escapes just mention the “R” word to a group of traditional boat skippers. (What is the collective noun for that I wonder? An “argument of skippers” maybe?). A common feature of these tales will be the idea that unpredictability is the only predictable response to engaging reverse gear.

In truth I suspect that we find it harder to predict the outcome of throwing our engines into astern mainly because we spend so little time doing it and so have less experience of how the forces acting upon the boat will cause her to react. This problem is exacerbated by our boats being designed to go forwards and their propulsion and steering systems being set up with this in mind.

Amelie Rose doing what she was designed to do – pushing forwards under a press of canvas.

My reversing epiphany was somewhat forced upon me when Amelie Rose and I found ourselves in Rye whilst filming The Hungry Sailors for ITV. With the channel barely wider than her bowsprit is long and the TV cameras recording every move I found myself required to reverse her for the best part of a cable in order to get parked up in the soon to be mud of Rye Town Quay. Until then I had been firmly of the opinion that “she doesn’t do reverse” and yet with a light breeze on her starboard bow she proceeded to head aft, as straight as an arrow and as mannerly as any Lady to the manor born.

Since then, experimentation with a range of boats has revealed that whilst most long-keel vessels are certainly recalcitrant in reverse and will tend to over-react to the mildest of imperfect circumstances they are certainly not as unpredictable as we generally convince ourselves.
Before we dive in to the practical let’s have a think about the various forces acting on our lady and how they change when we sling her into reverse:

Where is she going to end up? With all of these forces acting on our vessel in reverse it’s no wonder she may seem a little erratic!

Propeller:
As noted in the last article a centre-line propeller running in reverse will tend to “paddle-wheel”, forcing more water down one side of the keel than the other and resulting in an opposing “prop-kick” that will push the stern sideways through the water. This effect is proportional to the engine revs and is strongest when the boat is stationary in the water, decreasing as water flow builds over the keel and rudder. In reverse the propeller will also be pulling the boat along, rather than pushing it and in the case of a fixed bladed prop will be working less effectively as the blades are designed to push water backwards not forwards.

Wind:
The vast majority of traditional sailing boats will have more draft at the aft end of the keel than at the forward end. Indeed many will have a rounded or cut-away stem further reducing their grip on the water at the bow (which is also why the pivot-point is closer to the stern on these boats). Combine this with the action of dragging the boat backwards through the water and the bow will tend to blow off quite rapidly, continuing to do so until it is directly downwind of the propelling force. This effect is known as “stern-seeking” and can either be incredibly useful or astoundingly annoying depending on the direction of the wind and where you’re trying to get to.

Amelie Rose showing off her fairly typical long keel shape – much deeper at the stern than at the forefoot.

A little sidebar here; if ever you need to hold the boat in position for a while (say whilst waiting for a bridge lift) then slinging her stern into the wind with a touch of aft engine as required will make for an easy life. Trying to hold a boat head to wind in a tight space is a job for bored helms who don’t like to enjoy a nice cup of tea and a chocolate biscuit.

Rudder:
The relative positions of the rudder and propeller in a typical long-keel vessel mean that in reverse we have no ability to divert the flow of water coming from the prop (see “prop-wash” in the last article). This steals a key element of control from us when travelling backwards. The rudder on traditional designs also tends to be quite massive for the length of boat. The pressure on the tiller caused by pushing this whole thing backwards through the water can catch out the unwary helm – especially due to the increased speed required in order to grant the boat steerage in reverse.

Tide:
As noted in the previous article on “the getaway” the action of the tide flowing past our rudder and keel can either give us control with minimal movement across the ground or require us to be travelling at breakneck speeds in order to win steerage. It’s a brave skipper indeed who chooses to reverse with both wind and tide on the bow and thought should always be given to where the tide will be taking us whilst we fight to establish control over our direction.

A simple reverse unaffected by wind or tide. 1) Starting with an angle to offset the prop-kick 2) As the speed increases the prop kick diminishes and steering improves 3) Steerage achieved, though a little tiller may help to keep any remaining kick at bay as we engage tick-over reverse.

Putting it all together – reversing successfully
Taking all of the above into account our first thought before heading backward is centred on what the tide will do with us whilst we’re manoeuvring. With that discounted (or approved of) we can then turn our focus to maintaining control of the bow. A little breeze on the opposing bow to our prop kick may actually serve us well as it will tend to somewhat counteract the effects of the kick. Wind on the same bow as the kick however and we’ll almost certainly abandon the idea as we will struggle to keep the boat from stern seeking. If the wind is abaft us it’s time to praise the gods and move on to the next conundrum.

Next we consider our prop-kick. How much a boat will kick before control is established is something that only experience can fathom. Some boats (especially those with offset props) may never quite straighten up (at least until they hit suicidal speeds). Amelie Rose will kick through about 15-20 degrees and, if the effect is useful, can be encouraged to do more by pulsing the throttle (maximising the kick whilst minimising acceleration). Altering the boat’s initial angle to account for the kick is what we’re aiming for so that as she establishes her grip on the water she’s heading in the direction we’re after. As mentioned above, it’s possible to exacerbate the effect of the kick so overcooking the initial angle is often better than leaving it raw.

The effects of wind on the opposing bow to her Prop kick. 1) There’s no need for angle to start as the wind stops her from pivoting 2) She may crab sideways a little though as she picks up speed 3) Soon she’ll be yours to command.

Once we’re all set it’s time to hit the power. An observation here is that “fortune favours the brave”. The most common mistake that I see whilst teaching is that of being tentative with the power. Far from being “careful” this results in the boat taking longer to gain steerage which maximises the effects of prop-kick and may even result in her never attaining steerage at all. The objective is to get the boat up to her minimum steerage speed as rapidly as possible. On Amelie Rose in reverse this is somewhere between 2 and 3 knots – a speed which feels positively frightening – and which requires the helm to be very well braced indeed should they decide to deflect the rudder from amidships. It’s also possible that putting the rudder on full lock against the prop-kick may help negate the effects faster, but again this will vary from boat to boat.

Once a good steerage speed is attained it’s time to kill the power and then steer to safety, bearing in mind that if you undercooked the initial angle she may now be heading towards an incident. Killing the power kills the prop-kick, and providing you have your maths right on steerage speed should now put you in control of her direction. Once you have established that she’s answering the helm you may find that popping the engine back into tick-over reverse will keep the way on without causing excessive kick-derived deviations to your course. If she just won’t answer then you have a choice; pile on the revs again to get more speed (assuming that the fresh dose of prop-kick won’t drag her into more danger) or use a burst of forward to stop her and then return her to the starting position for another try.

With no wind to speak of but tide from aft. 1) No attempt made to offset the prop kick 2) The tide assists her in gathering steerage 3) She’ll now steer but will be ferry-gliding backwards and will need to address the tide directly

If she reacts to the helm then you can proceed, remembering that the boat is now being “pulled” along and will tend to take a wider arc around corners than she would if driving forwards (as you have no prop-wash to encourage her into a turn, and the hull is just trailing along behind you rather than cutting a groove for you to follow). Remember too that any breeze on the bow (for instance as you come around a corner) is going to have much more of an effect than expected and may even steal steerage back from you. My advice, for what it’s worth, is to get her turned around as quickly as possible.

With the wind on the same side as her Prop Kick she will almost certainly “Stern Seek” – fine as long as you have the room. 1) Prop kick pulls her stern around and the wind starts to blow the bow away 2) As she gathers way the bow continues to be blown off 3) With little bow now visible to the wind and plenty of way on she should answer nicely.

Practice makes perfect:
A last piece of advice: Learn to do this now; don’t wait until you have to do it in a tricky spot with the entire harbour watching you! Next time it’s a fairly calm day with a slack tide and you’re in no hurry to get anywhere why not try it out? Find fairly quiet patch of water with a trot of moorings or something down the side so that you can measure her progress and see whether she’s heading straight to where you ask. Stop the boat with your “guessed at” angle to negate the kick. Give it as much throttle as you dare and get her up to speed. Kill the throttle and establish steerage. Now re-engage tick-over and (if you’re lucky) show all those folks who say our boats don’t go in reverse how wrong they are.

Next time we’ll take a look at ways to turn our little ships around – without needing the width of a football pitch in which to do so.

Unless there’s endless room this is why we don’t reverse when the wind and tide are both on the bow. 1) As the manoeuvre starts the prop kick will show the bow to the wind 2) As the wind blows the bow off tide is now working on the whole of the keel – accelerating us sideways with virtually no control 3) We’ll be very lucky to attain steerage speeds before the wind and tide carry us into danger

1 Comment

  1. Vernon Needham

    Very, very thorough, and interesting. Thank you, Nick.
    At least Amelie Rose has a centre line, and in line, prop….. unlike Overlord, in which the prop shaft is both offset AND angled!

    Reply

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