LadyInBed
Well-Known Member
Simple
How to avoid rounding up whilst sailing downwind
- Thread starter maxmonk
- Start date
jimi
Well-Known Member
If you're comfortable gybing with the boom fully out in wind thats too strong for comfort whilst singehanded.
Not something that would be at the top of my list of options!
Salty John
Well-Known Member
I think if you are running downwind in 15 kts, gusting 25 kts, and sense the boat is becoming unstable the last thing you want to do is try to scandalise the main - the inevitable result will be a chinese gybe and then you really will have your hands full. You need to kill the drive and retain balance - flatten the main, get the head sail off, by furling, dropping or blanketing it behind the main and then you will be back in control.
sighmoon
Well-Known Member
I would have said let it out further - so the boom is short of the shrouds rather than the sail short of the spreaders. This alone could make all the difference.
I say 'I would have said' because this is what I've always done, but I was recently on a course and the instructor said the sail shouldn't touch the rigging. Both the school boat and mine have fully battened main sails, if that makes any difference.
So does the forum have an opinion if the sail (fully battened or otherwise) should be allowed to touch the rigging or not?
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fergie_mac66
Well-Known Member
Hardening the main is def' not the the thing to do could be a bit hairy if the boat started to turn, she could be on her beam very fast if a wave coinsided with a sudden gust, hope you were on a short harness line! If the kicker had been on tight loosening it would have the the same effect as starting to scandalise as the boom would rise .However single handing would be very happy if the kicker and topping lift led back to the cockpit, guess on a Beny they would be , if not moving to the mast with an auto helm on would alter the balance of the boat and helm may become unstable so you would want to be v quick at the mast. working in the troughs and hanging ontight at the top of any waves !
Edit chineese gybe is a risk though but less likly if the boat is stongly rounding up.. best get a gunter rig on her or gaff then you can reef easily down wind but a chinees gybe then would give you real problems !
Edit chineese gybe is a risk though but less likly if the boat is stongly rounding up.. best get a gunter rig on her or gaff then you can reef easily down wind but a chinees gybe then would give you real problems !
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Salty John
Well-Known Member
The main should be up against the rigging - I know of no boat on which you could hold the main off the shrouds and still be running dead downwind.
With a flattened main with the boom hauled down tight, as the boat turns the wind will spill. with a baggy main it will fill and accelerate the turn.
But, what do I know? I wasn't there.
With a flattened main with the boom hauled down tight, as the boat turns the wind will spill. with a baggy main it will fill and accelerate the turn.
But, what do I know? I wasn't there.
onesea
Well-Known Member
The stopper not in my main sheet is always set so the boom stops before the rigging, if the sail is against the spreaders thats fine by me. Boom touching rigging I have always considered as bad, the boom touching the sail never been an issue...
There is a forumite on here who can testify this, jybing with running backstay''s and I did not release main sheet quick enough (I blame the beer the night before). I am not certain if I laughed when it happened, it was as controlled as such a maneuver can be
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fergie_mac66
Well-Known Member
The stopper not in my main sheet is always set so the boom stops before the rigging, if the sail is against the spreaders thats fine by me. Boom touching rigging I have always considered as bad, the boom touching the sail never been an issue...
There is a forumite on here who can testify this, jybing with running backstay''s and I did not release main sheet quick enough (I blame the beer the night before). I am not certain if I laughed when it happened, it was as controlled as such a maneuver can be
should have added ...... if the boat started to turn ,before you were ready ,
Simondjuk
Well-Known Member
I'd second, or is it third, the need to make small rudder inputs. When sailing on the edge of needing to reef, I tell people not so much to move the wheel/tiller as to apply a little more pressure. It often makes the difference between the flow remaining attached and sailing through the gust and the rudder stalling and things going boss eyed.
Interestingly, it's often novice females who are best at following this advice. Perhaps because they're less inclined to heave the steering about in a misguidedly manly fashion as is the tendency of many gents.
In fact, I'd go one further and say that very often females tend to make more natural helms than men.
Interestingly, it's often novice females who are best at following this advice. Perhaps because they're less inclined to heave the steering about in a misguidedly manly fashion as is the tendency of many gents.
In fact, I'd go one further and say that very often females tend to make more natural helms than men.
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dom
Well-Known Member
I agree with the consensus that you are probably just over-canvassed. Here’s what’s likely happening:
1. With full white sail and 25kts apparent you will be approaching hull speed, which has your boat trying to ride up over its bow wave. At the same time the centre of effort (CoE) is well outside the hull on a near run. When a gust hits, the resistance of the wave magnifies the rotational force from the outboard CoE and your boat starts to turn.
2. You react by starting to wind the rudder on as the boat starts to round into the wind and the heeling force increases. Your rudder loses traction with approximately the square of your drop in speed and the Pythagoras element from your boat being on its ear (the force form the rudder is partially trying to lift the boat’s stern into the air). Your rudder eventually stalls out and an Oops! moment ensues.
3. But there’s worse to come for a boat almost dead downwind where your sails are at around 90 degrees to the wind. This high angle of attack causes an unstable non-laminar flow, in particular on the lee of the sail where bubbles of turbulence develop. A wave, gust, or change in direction can cause these bubbles of turbulence to separate from the sail and the sail’s lift drops right off. Your boat begins to roll. The lift will then randomly reappear either on the leech, or luff as laminar flow is temporarily resumed. This can set up a harmonic motion, which turns into a roll and another Oops! moment ensues.
In these circumstances getting sail off is probably the best bet, but there are things you can do. As you bear away onto a reach keep an eye on the upper telltales on the leech of your main. If you don’t have them it’s worth attaching three. Now you can see when laminar flow is lost.
As soon as you get concerned that your boat is getting over-pressed, pull the traveller upwind and ease the main sheet to compensate. This puts more pressure on the kicker. Try easing the kicker a little bit to increase the twist in the sail. A more open leech is less likely to set up laminar flow starting at the leech which you don’t want. As a gust hits, ease the kicker sharply to create a sail shape that is a poor airfoil. This partially prevents #3 above (the harmonic roll) as the sail is inclined to remain permanently stalled, as opposed to alternatively picking up drive at the leech and the luff.
1. With full white sail and 25kts apparent you will be approaching hull speed, which has your boat trying to ride up over its bow wave. At the same time the centre of effort (CoE) is well outside the hull on a near run. When a gust hits, the resistance of the wave magnifies the rotational force from the outboard CoE and your boat starts to turn.
2. You react by starting to wind the rudder on as the boat starts to round into the wind and the heeling force increases. Your rudder loses traction with approximately the square of your drop in speed and the Pythagoras element from your boat being on its ear (the force form the rudder is partially trying to lift the boat’s stern into the air). Your rudder eventually stalls out and an Oops! moment ensues.
3. But there’s worse to come for a boat almost dead downwind where your sails are at around 90 degrees to the wind. This high angle of attack causes an unstable non-laminar flow, in particular on the lee of the sail where bubbles of turbulence develop. A wave, gust, or change in direction can cause these bubbles of turbulence to separate from the sail and the sail’s lift drops right off. Your boat begins to roll. The lift will then randomly reappear either on the leech, or luff as laminar flow is temporarily resumed. This can set up a harmonic motion, which turns into a roll and another Oops! moment ensues.
In these circumstances getting sail off is probably the best bet, but there are things you can do. As you bear away onto a reach keep an eye on the upper telltales on the leech of your main. If you don’t have them it’s worth attaching three. Now you can see when laminar flow is lost.
As soon as you get concerned that your boat is getting over-pressed, pull the traveller upwind and ease the main sheet to compensate. This puts more pressure on the kicker. Try easing the kicker a little bit to increase the twist in the sail. A more open leech is less likely to set up laminar flow starting at the leech which you don’t want. As a gust hits, ease the kicker sharply to create a sail shape that is a poor airfoil. This partially prevents #3 above (the harmonic roll) as the sail is inclined to remain permanently stalled, as opposed to alternatively picking up drive at the leech and the luff.
fergie_mac66
Well-Known Member
wonder how excelsior lost her mizzen
charles_reed
Well-Known Member
All boats vary - but I'd think a good place to start would be to put a reef in the main. You'd find little difference in speed.
MJWF
Active Member
Agreed, op needs to reef but first he needs control. . How about this for an idea (ive never tried it and it might be a bad plan but interested in views of panel)....
Put engine on in 3/4 ahead. Probably wont go any faster but will have more grip with the rudder giving better opportunity to control direction. Secondly as the boat leans moving the centre of effort outboard the engines power is doing the opposite side helping to keep the boat straight. Once you have control, turn smoothly into wind and get some sail in.
Thoughts???
Put engine on in 3/4 ahead. Probably wont go any faster but will have more grip with the rudder giving better opportunity to control direction. Secondly as the boat leans moving the centre of effort outboard the engines power is doing the opposite side helping to keep the boat straight. Once you have control, turn smoothly into wind and get some sail in.
Thoughts???
LadyInBed
Well-Known Member
I just can't think why anyone would want to use the Main when running.
Think Supermarket trolley - if you pull it from the front you have directional control, if you pull it from a stick near its middle it has a mind of its own.
Think Supermarket trolley - if you pull it from the front you have directional control, if you pull it from a stick near its middle it has a mind of its own.
MJWF
Active Member
Maybe. Although not sure the hydrodynamics of a boat are well modelled by a shopping trolley with wobbly wheels. On that logic why wouldnt boats have props near the front?
JumbleDuck
Well-Known Member
At which end of your boat is the propeller?
LadyInBed
Well-Known Member
A pull from one end isn't a lot dissimilar to push from the other when talking about the contact point of the force.
dunedin
Well-Known Member
I agree - if on a boat with a decent sized genoa, downwind under genoa only is fast and almost fail safe - self steering and no risk of a boom gybing.
(this is one of the big disadvantages of the current fashion for very small or worse self tacking jibs)
If caught out by a gust, like the OP, the only solution is often to anticipate the extra pressure and bear off before the gust hits, right down to a dead run - we often call "pressure coming.- bows down" as a warning to the helm.
All of this works to a large degree, but has its limits.
We got caught downwind with one reef when the wind built from 18 knots building steadily over a couple of minutes through 30 knots, getting bows fuly down no prob, through 40 knots, getting a bit iffy, 50 knots - this is going to end in tears - at 53 knots true we lost it and a huge spin out - fortunately with room to go round and rapidly put in a triple reef while pointing the wrong way
Twister_Ken
Well-Known Member
I'm guessing your objection to small jibs is just lack of area when used on their own, rather than anything inherently wrong with the system?
FWIW we once sailed a Swan 411 back across the channel, with just the number 4 genoa up - a rust stained old thing that normally didn't get an airing from one end of the season to the next. Wind was port quarter, 30kts apparent in the lulls, 40 in the gusts so probably close to 50kts true in the gusts. Drama free as far as sail handling and steering was concerned, but there was a fair bit of uncomfortable rolling and corkscrewing going on.
Did something not-quite-similar last year in my boat. Just the 109% fractional genoa up, from St Cast to Jersey, wind building to a F7. No problems, lots of control. Still got to St Helier too early for the cill.
john_morris_uk
Well-Known Member
May I humbly suggest that attaching the kicker to the toe rail is a terrible idea. Booms break.
The single handed isn't the issue, but sea room definitely is. You should be able to pole out the genoa, but use a spare sheet and fix the pole so that you can still sail upwind (with it sticking out sideways if necessary). I suggest that the pole needs a fore guy, after guy and up haul on it to be safe.