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Does It Make Sense to Use a Radio Controlled Backstay And/Or Vang?

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Does It Make Sense to Use a Radio Controlled Backstay And/Or Vang? Does it make sense to use a radio controlled backstay and/or vang? I can't speak for "most top skippers" but would totally agree that "Good starts, staying in phase, and sailing a clean race are way more important than adjusting a vang or jib flipper". The IOM class strictly limits the number of channels and functions controlled by radio, to 2. On the other hand, you will see many 2 channel boat skippers making changes to the tune of their boats between races. This is particularly true at events using heats where the off-the-water time can be extended and changes in wind and water conditions are easily seen, can be significant and are responded to through adjusting tune prior to launching for the next heat. The rise in popularity of “swing rigs” was due, in some small but significant part, to the need to quickly change rigs prior to the start of a race, often within the last minute. Lots of thought has been given to developing an ability to get the right rig onto the boat in the very shottest time possible. You can see this intent in the design of some of the systems for attaching sheets and shrouds etc. So it would appear that most skippers, top or otherwise, understand the need to get the right rig on the boat and get the right shore-side tune prior to the start of the next race. But what about once the boats are on the water? An important factor to consider is the average duration of a heat or race. Most people would accept that an average duration of a heat or race would be between 10 to 15 minutes. (e.g. with 5 heats per race at a world championship regatta with 84 boats competing, an average heat time exceeding 15 minutes would result in fewer than optimum races being sailed). Very important factors to consider are 1) the extent and frequency of changes in wind and water conditions that you may experience once you have launched your boat 2) tactical performance considerations during the final countdown, the start, the sailing of the course and the finish of the race. So, On to the Vang and Backstay… Let’s look an example and make some assumptions… Assumption 1: The average duration of the race is 15 minutes Assumption 2: we have 3 top skippers (and the rest of the fleet) and the top skippers are all at the same skill level and capable of “Good starts, staying in phase, and sailing a clean” and do so regularly. Assumption 3: Each of the 3 top skippers are sailing nearly identical boats... the same hull (let’s say a hull016) with sails from the same sail maker, same foils and lead bulb. The only differences are: o Skipper 1 has RC control of rudder and winch only (the lightest boat – just 2 channels) o Skipper 2 controls rudder, winch and backstay (and additional 0.84 ounces) o Skipper 3 controls rudder, winch, backstay and vang (an additional 1/68 ounces) o There was a skipper 4 but he is hung over) Assumption 4: let’s assume that the average wind is 8 knots and the frequency of lulls is twice that of gusts and the cycle between the average wind speed and a gust OR a lull is 3 minutes. So there will be 5 cycles in a 15 minute race. Assumption 5: All three boats a nicely tuned to the average wind speed of 8 knots. So, on to the race! Handling Gusts and Lulls… We start the race with the average wind speed, 8 knots. True to form, our heroes, the top skippers, get off to a great start, ahead of the fleet and separated enough that all are in clear air and essentially on an equal footing. And all else being equal, they have had a “good start, stayed in phase, and have sailed cleanly”. 1. Now, at +1 minute into the race each of our top 3 boats experience a gust, the same gust, the wind increases from 8 knots to 10 knots. QUESTION: How much has the force of the wind increased? The force increases by 10/8 squared, or 1.56 more force available to power or heel or propel the boat. More than 1 ½ times the force available just seconds ago. So how will each Skipper handle the gust? Skipper 1 has RC control of rudder and winch only so he: a. luffs up a bit to counter the increased healing forces b. or he eases the sheets to align the forces on the rig in a more forward direction c. or he carries on with increased heel. The first 2 options have their own reasons for being good under the circumstances but the increased heel is probably accompanied with increased leeway and that is not good But there are other potential problems too. Along with the increase in side-force, there are a number of nasty things that could still happen, including: Increased jib stay sag which definitely affects pointing An initial “stagger” when the gust hit, with increased leeway, as the boat may not have been headed up early enough ahead of the gust because to do so in advance would be pinching and the boat would slow down. When the boat staggers it sends a boat sideways a little more and increases leeway Weather helm, with the boat rounding up quite violently (the CE and Lateral Resistance couple definitely shift when we sail in varying winds – you know that because most of us use the common practice of shifting the center of effort of the sail plan forward or aft (repositioning the rig ahead or at least raking the mast forward (or aft if lighter winds)) to counter weather helm in heavier winds and lee helm in light winds) Additional drag in countering weather helm - we have all, at one time or another had to fight weather helm by increasing the deflection of the rudder… this increase drag a lot. There are other challenges our two channel skipper has but the above is enough to make the point. Skipper 2 controls rudder, winch AND backstay. Skipper 2 is a bit better off because: backstay control can be used, in response to the gust, to tighten the jib stay to limit sag with a fractional rig, the back stay can be used to bend the mast, flatten the main and twist off the top of the main leech. the preceding will help to reduce heeling, reduce the resultant leeway and in fact reduce weather helm because of the flatter twisted main. the flatter twisted main leech also has the effect of moving the effective CE forward. Other than what the backstay offers, this skipper can also luff up a bit to counter the increased healing force available and ease the sheets to align the forces on the rig in a more forward direction, just like Skipper 1 did. Skipper 3 controls rudder, winch, backstay and vang. Note: We have been talking about an average wind speed of 8 knots. Generally, a boat with more ballast will be able to carry the #1 or A rig a little longer than a more lightly ballasted boat. Perhaps most would agree, 8 knots is probably the top end of a #1/A rig. Boats like the Venom are intended to be sailed with their B rig in all but the lightest winds. So Skipper 3 is confronted with the same gust, increasing from 8 to 10 knots. Skipper 3 has the largest scope of options. Skipper 3 can head up and/or ease the sheets like skipper 1 or additionally tighten the backstay like Skipper 2 would but then: Skipper 3 can use an even larger range of backstay adjustment because, even if the amount of backstay required to flatten the main was such that the main leech had too much twist, the leech can be tightened to remove the excessive twist with the radio controlled vang. Some would argue that you can tighten the mainsail leach with mainsheet. The problem with that is you are bringing the main boom back to the centerline and increasing the side force and heeling of the boat. The Vang allows the leech to be controlled independently, no matter what the sheeting angle is. So, Back to the Race! This is where it really counts! 2. At +4 minutes, the gust dissipates and we head into a lull at say 6 knots. The force available at 6 knots, as compared to 8 knots, is 0.562 or roughly ½ the force that was available at 8 knots. The winds further drop to 3 knots (it happens – that is about 15% of the force that was available at 8 knots) Skipper 1 can’t really adjust the sails from what was accomplished during the shore-tune for the average wind of 8 knots. Some skippers have excellent skills in developing flexible rigs that, in some ways, automatically adjust in gusts, it most often not the optimum but works with reasonable effectiveness. Nothing can be done about the lulls however if you don’t have radio control functions to deal with the lulls. (Above design wind requires flexibility and below design wind things are a bit stiffer) Skipper 2 is in a little better shape. Moving back to 8 knots, he can power up the main a little by easing the backstay. This also eases tension on the jib stay and creates a little more shape.
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