Light air, big waves

[Geoff K]

Two days ago we set out for a pleasant sail in 8-10 knot winds hoping to practice the trim directions in Don's book. Turning into the south channel leaving St. Louis Bay (West end of Lake Superior) we were struck with 3-4 foot waves with a very short period. Though the wind was light/moderate, there had been stronger east winds for 3 days. We proceeded into the lake a couple hundred yards hoping the waves would smooth out. They didn't. The boat was hobby horsing something fierce and very uncomfortable. We turned around and sailed in the protected bay with minimal waves. We had a good practice session there.

My question is how could we have trimmed sails for these conditions. The only time we've been in large waves (4-6 feet) before was in strong winds. I recalled getting only 2 knots of speed and the sails flopping in and out of stall with each wave on a close reach. Is there a way to trim sails to minimize the hobby horsing and maximize the sail function? The boat is a Pearson 323, 32', 13,000#, long chord fin keel, and skegged rudder. The bow water tank was empty and we have a light anchor/rode but neither of these factors can be changed on the spur of the moment.

Geoff

 

[Don Guillette]

Geoff: Thank you for purchasing my products. 8 to 10 knots of wind is not light air and if your sailing in strong winds and your sails are flopping around your trim is wrong.

Now that we got that out of the way let's talk about how we have to adjust "the 4 elements of sail trim" for choppy conditions. The 4 elements are draft depth, draft position, twist and angle of attack and those elements are the ONLY things ALL the sail trim controls for the main and jib are adjusting - see chapter one. Always take your SAIL TRIM CHART and especially your QUICK REFERENCE that came with your sail trim chart when you're practicing. After a few practice sessions you won't need then anymore as you'll know WHY you're making a particular sail trim adjustment. The WHY of sail trim is EVERYTHING. In other words, you've got to know WHY you are making a particular sail trim adjustment or you're just guessing.

I'm going to make this overly simple because it really is.

We need all the POWER we can get to sail through chop so lets take the elements one at a time. You need your DRAFT POSITION to be forward. The more the wind pipes up it pushes the DP aft and you have to use the sail trim controls I've outlined for the main and jib to move it forward.

You need about 20% DRAFT DEPTH (belly) in both the main and jib. A flat sail has no power. DD is your power source. Use the controls outlined on your QUICK REFERENCE to dial in the power you need to get through the chop.

You need to eliminate as much TWIST is your main and jib as you can. The more the top of both sails "twist off" the more power you've lost. Again, use the adjustment controls outlined on your quick reference.

The ANGLE OF ATTACK is your accelerator. Adjust the angle of attack for your main and jib for max power. In other words, you want the boom close to the center line and the jib tight mirroring the main. If you slack off on the angle of attack you'll reduce your power.

Now, wasn't that simple!! Pretty soon, with a little practice, you'll get to know the settings for your jib and main that you need to make for every point of sail and wind condition.

Now, for your homework assignment, tell me the main and jib settings for the 4 elements of sail trim that you'd need you'd need to sail closehauled in say 5 knots of wind? Soon you won't need to look them up - you'll just KNOW what they are. When you get to that point you'll know more about sail trim than 75% of the sailors worldwide. If you don't believe me just start this question with your dock neighbors!!

Anyone can chime in on the above question.

 

[tomgrigsby]

So Geoff shoud ease the outhaul as needed and tighten the cunningham to get belly and move DP to about the 45% position. Move the traveller to windward to eliminate main twist. Move the jib sheet block forward to remove twist from the jib. Tighten jib cunningham (if you have one) or tension the halyard to get DP forward.

 

[Stu Jackson]

The hobby horsing is also from not having that power that don mentions, so the slow boat is more affected by the waves, instead of moving smartly and starting to cut through them. 8-10 knots is a nice breeze for a good sized genoa or jib and a full main.

 

[Geoff K]

You're right, as I read your explanation, it is simple. After I've done it on the water a few times it should stick.

I should mention, I did not sail in the chop 2 days ago, went back inside the bay to smooth waters. I had sailed in big waves/big chop 8 years ago without any good knowledge about trim (or much else about sailing) but there has been a hiatus in my sailing since. We're re-learning now. I'll work on the assignment.

Geoff

 

[RichH]

Sailing into oncoming short period and HIGH waves successfully (to lessen hobby-horsing) is more dependent on STEERING (boat handling) than sail shape.

Sailing/beating into HIGH STEEP chop is probably the WORST condition for a sailor, especially if the wind has dropped! Without the energy from the wind to keep the boat 'moving', such 'chop' causes the boat to rapidly accelerate/decelerate ... especially if one attempts to steer a STRAIGHT course through the chop.

Steering a STRAIGHT course will cause the boat to almost 'launch' itself off the top of a wave only to have its bow plunge deeply into the trough of the oncoming wave. A bow thats buried into an oncoming wave will tend to STOP the boat, and the bow will get 'knocked to the side of the wave a bit'. The reaction of buoyancy will then LIFT the bow ... and (maximum) 'lift of buoyancy' will occur just at the time that the crest of the next oncoming wave passes under the bow tending to 'launch' the bow free of the water .... and the whole cycle repeats itself for every wave .... plunge then 'launch', plunge then 'launch', .... deceleration then acceleration. During the acceleration -deceleration the apparent wind changes back and forth (due to the change of boat speed), the boat struggles to accelerate, etc. etc. etc.

The solution is to steer a continually 'scalloped' course so that you are going as fast as possible, keeps your 'momentum' and doesnt 'bury the bow' into the bottom of the next oncoming wave as much. A 'scalloped' course will have the boat crossing the trough at a 'broader angle' to the oncoming wave which lessens the 'plunge' or burying of the bow INTO the wave, followed by steering at a steeper angle 'up' the wave until the bow reaches the next crest, just before the crest then one 'bears off' to keep the boat IN the water and then quickly 'hardens up' again to go down the backside until starting to get into the trough where once again you slightly 'bear off' to lessen the 'plunge'. Typically a 'scalloping' course will involve moving the 'wheel'/tiller about 90++ degrees back and forth TWICE for each wave. The hobby-horsing will lessen, the boat will keep 'driving' with less 'sudden stops', etc.

For such wave conditions you need to reshape your sails into a POWER shape to aid and maximize the acceleration, this is not a time to have FLAT sails- flat sails are for speed not accelerating. You want your sails 'shaped' for 'second gear' or if the seas are 'immense and short period' down into 'first gear'.
1. Tighten the halyards ... causes the luff sections to become more 'rounded' which is more 'forgiving' to constantly varying 'angle of attack'
2. Ease the mainsail outhaul - to increase the draft (power), move the jib fairlead cars FORWARD a 'notch or two' (for more power). How much 'easing' the outhaul? .... ease until you get maximum boat speed going 'up' a wave face.
3. Set the Twist so that the sail is 'normal' during the 'going up' & 'coming down' phases ... in the troughs and on the crests the top of the mast/sails can be 'moving backwards to the oncoming wind .... so, forget about what the twist looks like on the crests and in the troughs, only when going up or down the faces.
3. Drop the traveller a bit ... POWER UP.
3a. or better yet - open the traveller at the crests and just before troughs as you 'foot off' and then quickly return the traveller to 'normal' for going 'up' and 'down' the wave faces - leave the mainsheet alone. This 'playing the traveller' constantly can be very tiring but is very effective in steep short period 'chop'. Caution: dont bring the traveller IN to the degree that causes an increase in apparent 'weather helm'.
4. Look at your charts and sail towards DEEPER WATER ... deeper water will have less wave heights and longer wave periods.
5. Set/trim your sails so that the tell tales are streaming well when on the 'faces' of the waves, forget about what they look like when in the troughs and crests.

Sailin/beating into high steep chop while holding a 'straight course' will result in whats called "the Caribbean Two Step" ... one step forward, one step to the side. 'Scalloping' will artificially lengthen the wave period, give TIME for the acceleration, lessen the 'plunge', lessen the 'launch' .... and result in a 'higher' overall course sailed.

Shape the sails into a POWER shape (according to max. value shown on the SPEEDO) and then PLAY the traveller.

If scalloping seems to be 'too much work', then simply bear off onto a high close reach and bear off slightly in the deep troughs.

 

[Don Guillette]

Tom: Just one quick comment. The traveler is not used to adjust twist. Mainsail twist is adjusted by using primarily the boom vang or secondarly the mainsheet.

Think of the traveler this way. Picture your screen door with a pin in the corner that rides in a groove in the floor. When you open and close the screen door does the shape of the screen change? Nope, it doesn't. Neither does the shape of the main when you move the traveler. The travelers only function is to adjust angle of attack. A great function of the traveler is when you are hit with a gust and the boat heels over. Lots of sailors then release the mainsheet to get the boat back on its feet. That action tends to change the shape of the sail. Their first reaction should be to drop the traveler. When the boat gets back on its feet you merely move the traveler back to its original position an sail off on your way without any change to the shape of the sail.

 

[Stu Jackson]

Don, I also don't understand folks who dump their mainsheets instead of dumping their travelers. It's so much harder to get the mainsheet back in than it is pulling the traveler back up (unless, of course, they don't have an easily adjustable traveler).

Yours is good advice.

 

[ffaubert]

I seem to be missing something here. Is your mainsheet connected to the traveler?

I have a smaller boat that has the mainsheet on the end of the boom and then a traveler arrangement about the middle of the boom. I haven't used the traveler because the mainsheet seems to do the same thing. The only difference that I can see is that the mainsheet arrangement doesn't interfere with going in and out of the cabin.

 

[Geoff K]

Thanks, everyone. This is helpful. I've got 3 threads going at once and learning from all of them. That, of course, means I've got a lot to learn. In fact, I've short enough of the basics that it will be a while before I try my skills on the big waves. I'll save this thread for future reference and, at least in my head, have a better idea of what I'm working toward.

We're basically lazy sailors, not in it for the adrenalin rush. But we do want to cruise Lake Superior and know we will be in some "work" days of sailing at times. And there's something addicting about getting just a little more out of the boat, even for us older folks.

Thanks much

Geoff

 

[Joe]

Geoff... here's another 2 cents worth... and that is to pay close attention to Rich's post... steering technique is the most important thing to master in choppy or steep wave conditions... the scallop or "S" pattern is most effective... so you might steer straight up the face but turn down the backside. The goal is to keep your air from spilling by minimizing the hobby horse action. It's much easier to manage this with the tiller than trying to play the traveller. I agree about keeping the sails powered up, one reason is it keeps the boom from bouncing, but you really don't want to keep spilling your air with excessive twist, the boat's motion will see to that.

So get the leech fairly straight, get some power in the sails to help push through the lulls and steer an "S" shaped course........... it's like skiing moguls.

 

[Joe]

I seem to be missing something here. Is your mainsheet connected to the traveler?

I have a smaller boat that has the mainsheet on the end of the boom and then a traveler arrangement about the middle of the boom. I haven't used the traveler because the mainsheet seems to do the same thing. The only difference that I can see is that the mainsheet arrangement doesn't interfere with going in and out of the cabin.

If you have a traveller, your mainsheet tackle will be attached the the traveller car/slider which is mount on an athwartship track ... if you don't have a traveller, use the vang to control twist. If you don't have a vang, get one. Many small boats don't have travellers, but they all have vangs.