Author Topic: LIGHT AIR DOWNWIND PERFORMANCE  (Read 2167 times)

Ed "Buttons" Padin, Class Administrator

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« on: September 03, 2015, 11:38:35 AM »
By Peter Beardsley and David Owen, Viper 222 “Ghost Panda”

Light air can be frustrating to a lot of teams, but since Vipers can ghost along and race in conditions that keep other classes ashore, mastering "the super light" is an essential skill.  Sailing in the summer in Larchmont has given us a fair amount of light air practice over the years and we've figured some things out, even on days when we're sailing 4-up versus lighter teams. 

We think there are 4 downwind modes in Vipers:

1. Super light air (sub 5 kts)
2. Light air 5-9 kts
2. Marginal planing (9-13 kts)
3. Planing (13+ kts)

Each mode requires different techniques.  For this article, let's just focus on Mode 1.  It's not a fun mode but massive gains and losses can be made in these conditions.

A Viper has fairly neutral helm upwind, even in big breeze.  The tradeoff is that downwind, especially in very light air, that configuration can generate a lot of lee helm.  To counteract that and balance the helm, you need to create a few degrees of leeward heel.  To do this, and to reduce wetted surface, our team's weight is positioned as follows:

- Driver sitting on cockpit floor, legs stretched out to leeward for maximum comfort and also to get the weight of your legs off the windward side of the boat, entire body forward of mainsheet bridle to get weight out of stern.
- Middle crew sitting on cockpit floor in same position forward of driver, almost at shrouds.
- Forward crew standing on foredeck to leeward holding mast, high enough to see puffs and mobile enough to move to weather quickly to flatten or otherwise promote course changes without rudder

If you're not in this position as a starting point, you may have lee helm from time to time, and will end up sailing too high or using too much rudder, or both.  The "downside" to having your weight mostly along centerline downwind is that the boat will be overly responsive in a puff, which while a blessing upwind, means you'll need quicker reaction time downwind to keep the boat tracking properly.  The key person here is the forward crew, who because he or she is standing on the foredeck, is in a mobile position to step to windward to flatten the boat as a puff hits, allowing the driver to maintain neutral helm and help the boat carve down to a lower course to take advantage of the puff.  The middle crew should also position his feet against the leeward foot chocks so that if a puff hits, he's in a position to straighten his legs and quickly and smoothly extend his body over the windward rail to promote steering and neutralize the helm. 

NEXT: slot
Next time you're out on a light air downwind day, go to leeward as the driver and see how close the leech of the kite gets to the mainsail.  You'll be surprised / mortified.  The kite can close the slot very quickly, especially in light air.  Most people don't think about the slot downwind, but it is crucial - if you ever see ANY backwind on the main on a Viper downwind, you have a serious flow (and consequently, speed) problem.  In very light conditions, we frequently sail with the main almost centerlined, and certainly no further out than the boom on inside of the leeward tank.  The driver will trim the main from above the ratchet to be able to feel puffs in time with the kite trimmer and the kite trimmer will let everyone know about kite eases so that we can also ease the main to open things up when possible.

NEXT: turns
As in, don't do 'em.  In very light air, we need an EXCELLENT reason to gybe vs. sending it to the corner and just doing a single gybe.  Even the best light air gybes are slow -- even worse than light air tacks.  The boat basically stops and you have to sail very high on the new gybe to rebuild speed. 

If you do have to gybe, you need to roll the snot out of the boat.  We roll into the turn to use our weight to steer the boat.  Everyone stays down on the old windward side artificially long to allow gravity to assist in getting the kite to the new side and also to give you something to flatten against - no matter how much you think a Viper can resemble a dinghy sometimes, a Viper always weighs more than the people sailing it and you need to be physical if your weight will make a meaningful difference when tacking or gybing.   Take care to finish the turn and be close to your optimum exit angle before flattening, which is usually slightly higher than 90 degrees from your prior course in very light air. We will usually not try to float the kite around since it's going to collapse and invert anyway in very light conditions -- in less than 5 knots, it is very difficult to do a "blow-through gybe" in a Viper since there's not enough pressure to blow the kite around the jib (usually start having a chance to blow through in 6-7 kts with practice, and 8 kts more comfortably), and the cloth will just hang up and make a slow maneuver even worse.  When we don't do a blow-through, we do what we call a "drop and go.”  This gybe is named because we literally just drop the working sheet and start hauling the new sheet around, with the kite trimmer positioned with one foot on the new leeward tank to enhance the roll and to give himself a springboard to get to windward.  Everyone should roll as hard as possible within the confines of class rules and Rule 42 -- remember that Class Rule 10.8 says you cannot use the mast or shrouds to promote tacking or gybing.  That said, the class rule does NOT say that all crew must be in the cockpit for a gybe, so if the forward crew is on the foredeck for the gybe and wants to hold onto the mast during the gybe (a good practice for safety purposes if nothing else), consider ensuring that your arms are bent - if you fully extend your arms as a forward crew on the foredeck during a gybe while holding the mast, you're probably on the wrong side of Class Rule 10.8.  The driver should be the first one to flatten out of the gybe - the guy with the tiller needs to be able to steer.  The kite trimmer should be next, though only as much as needed.  The forward crew controls the balance - is able to flatten if needed or stay low if the rest of the team is about to over-flatten and spill wind from the sails. 

That said, there's no reason to blindly send it to the wrong corner or stop sniffing around for crucial puffs just because gybing is slow in light air - we will chase better pressure high in light air to reach a puff sooner since it may increase your boat speed by 2-3 knots in a Viper once you hit the puff in those conditions.  In the absence of a puff, we remember an article US Sailing Team coach Luther Carpenter wrote about sailing Vanguard 15s years ago - if you find yourself sailing higher, consider gybing.  You're either sailing higher because you're lifted (in which case, there will be a header on the new gybe), or because you're in a lull, in which case there could very well be better breeze on the other gybe.  However, look before you leap to ensure you're not compounding a problem or gybing away from what is about to be a great puff.   The driver is in the best position to keep half an eye on the compass downwind and should tell the team from time to time (or have a crewmember ask if your driver is "in the zone" and not checking the compass every 60 seconds or so) to determine whether your heading has changed.

FINALLY: straight-line speed
When in sub 5 mode, you're just trying to keep the bus moving, sailing artificially hot to do so.  Be very conscious of waves and heeling the boat a bit extra going into a wave to reduce wetted surface and to promote steering to the extent you need to head up to change the angle of the bow vs. the wave.  Sail hot for the momentum early, and sometimes even easing a few inches of kite halyard into a wave to keep the sail full. The kite trimmer may feel pressure to overtrim a bit in a wave to keep the kite stable, but it's a fine line since if you stop the boat heading into a wave, your apparent wind angle will move aft, so be careful not to overdo it. There's almost no chance to take a puff low in super light conditions, though we do still talk about pressure, but usually we're more focused on going fast and going forward than we are in soaking.  That of course changes once you're in 5-9 kts and in Mode 2.  Finally, depending on the cut of your kite, you may find yourself needing to pay more attention to the upper part of your luff for a curl - everyone has been taught that seeing a little bit of curl is fast, but with an asymmetrical spinnaker, that's only just to know that you're close to proper trim.  If you see a curl, it still means the sail is luffing, so we try to be laser focused on our upper luff panels where our kite tends to curl first and develop a mind meld with those panels - we only want to see a hint of a flicker sometimes, and want to trim that out ever so slightly so that the sail is in optimum trim, generating as much power as possible with no curl, while being ever cautious to want to know that if we eased another inch, we'd see that tiniest bit of curl. 

A corollary to straight line speed: jib up or jib down?  A lot of people start dropping jibs in very light conditions.  We don't have consensus on this move.  We think that if you find yourself caught in conditions that are borderline unraceable (i.e., 2 knots or less), the jib will start interfering with the kite and we typically drop it.  We used to drop the jib in less than 6 knots almost reflexively, but recently have not found that to be fast. The most important things to think about with the jib are not to overtrim it - it's a small sail compared to the main and kite – get the other sails right first.  Overtrimming the jib is worse than undertrimming it since overtrimming the jib throws wind back into the slot and can cause the other sails to stall.  And if you think the kite is not drawing as much as it could be, then consider dropping the jib, but we recommend hoisting the jib prior to gybing to minimize the odds of putting the kite through the foretriangle.

No one loves sailing in super light air mode, but we're lucky to own a boat that makes painful conditions less awful, and if you incorporate these tips into your sailing, you'll get through the next light air run faster and can start rehydrating and hoping the wind picks up for the next race.
Ed "Buttons" Padin
Viper 640 Class Administrator
erpadin [at] padesta [dot] com

Tim Carter

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« Reply #1 on: September 03, 2015, 12:00:07 PM »
All good stuff guys and right on the mark.  When we decide to drop the jib, we only lower it about 6'..  seem to allow the kite to breathe and I convince myself the top of the jib is still working..
Lt Coast Gov