| Written
by: Bryan Steele Foilfreaks.com |
More
options to dial-in for high performance foils… |
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When it comes to the new high-performance foils, there are more and more options to dial-in. This article will try to demystify these options, and help you dial-in your new hydrofoil to suit your riding style. In the beginning, foilers had to make some drastic changes and “tune” the original Air Chair in order to maximize the potential of the sit-down hydrofoil. Since Sky Ski was started in 1998, the need to actually “tune” your foil was much less of an issue and required much less work, since these foil incorporated all of the “tuning” modifications from the previous years. In the past few years, Sky Ski has improved manufacturing process and material of foils, i.e high-strength billet aluminum, CAD design, computer numeric controlled parts, metal extrusion. The new foils hardly need much tuning, but now we have different wing options, wing placement options, and strut lengths. This gives the rider more options to “dial-in” to suit their riding style and changing water conditions. So, remember that “tuning” deals with reshaping/changing the foil and “dialing-in” deals with setting the right options. These options include… 1)
Shimming – slightly changes the angle of attack
of a front or rear wing with a shim. To understand the basics of “dialing-in” a foil, please refer this article. This will help you understand what terms like quickness and lift mean, and the basics on how to adjust quickness and lift. http://www.foilfreaks.com/articles/lexdialing/LEXDialing.htm Now, let’s talk about the high performance options that have occurred in the last 3 years, and what effect they have when foiling. a)
Longer struts (B-39 & LE38) Longer Strut Lengths From a rider’s perspective, there is not much to dial-in when it comes to strut length. The B-39 is the only foil today that allows for adjustable strut length. What a rider needs to be concerned with when it comes to a longer strut length is that it may take a few rides to get used to the difference… Why should I get used to the difference? The benefits of the longer strut will first be apparent on the landings. Basically, it just gives you more time to regain control on a landing…the wings have a bit more time to clean off air pockets and regain flight before the board smacks, the rider has a bit more time to situation himself/herself to control the foil before it pops back out of the water, etc. The longer strut will also help get people in the air higher, because the foil has a more time to accelerate through the water before exiting, especially when you figure out how to time the take-off properly and start using more of the strut length during take-off. What is the difference? There are two main differences…swing weight and take-off timing. These foils are a little bit heavier, but that won’t take much to get figured out. The swing weight is in a slightly different place (further away), so it may take a few off-axis inverts to get it figured out, but it’s not a big deal. During the take-offs, you will need to be slightly more patient so that the foil has time to exit the water before starting into your maneuver. The foil is a bit longer, so you’ll want to start flying higher and start the dip from higher up to make good use of the extra inches. And…you’ll need to get used to more hang time, because it will put you in the air a bit higher. All of these things will be easy to adapt to after a few rides, and the benefits are positive…bigger air with more control. For the B39 foilers…which strut length setting is right? I’m not sure there is a definite answer to that. I’d recommend picking a strut length that feel comfortable, then dial-in your wings (more described below), and possibly tune up the foil (if necessary). After you get comfortable riding at a longer length (in general), try a different length setting… re-dial the foil and see if the length change is better or worse for you. Batwing Designs The batwing refers to a wing that has some of the trailing edge removed, when compared to the traditional straight trailing edge wing. Removing the trailing edge of a wing mainly adds quickness to the setup. Instead of sliding the wings closer together, you can remove the trailing edge of a wing and make the foil quicker. A smaller, secondary effect is that the foil will be a bit more loose feeling when leaning left and right, compared to a straight trailing edge wing. So adding a rear batwing will give a bit more quickness to the setup, which can result in a slightly steeper take-off. This will feel like the foil “pops” better out of the water. Most people prefer using a rear batwing. The front batwings (’03, ’05, and ’06) also have the trailing edges removed, but the ’06 mini-bat has a very small amount of trailing edge removed compared to the ‘03/’05. With less trailing edge removed, the wing will be less quick and have a bit tighter feeling when leaning left and right, compared to the ’03 and ’05. There is one more variable that the front batwings add. The batwings either have more material in the front of the wing, and/or the bolt holes are drilled in different places on the wing, compared to the tradition straight trailing edge front wing (the most popular front wing for the LEX). What this does is push the nose of these wings further forward over the front of the fuselage. We’ll talk about this effect next, since it ties into the multiple front wing placements on the front fuselage. Front Wing Placements The LEX with a straight trailing edge front wing has about 1 inch of the nose of the wing in front of the fuselage, and it offers no adjustability. The 2003 front batwing is about 2.5 inches in front of the fuselage on the LEX…again no adjustability. All of these measurements might not be exact, but it will give you a better idea of the concept. What happens when you move more of the front wing past the front of the fuselage? Two things… 1)
Increased Lift Both of these are usually good qualities, but too much of them can cause an unstable and difficult ride, which leads to a greater learning curve or a loss of riding potential. First, let’s talk about the lift, and this is another MAJOR point… Do not select a wing placement, just because of the way it affects lift. Again… Do not select a wing placement, just because of the way it affects lift. You could be sacrificing increased stability (greater riding consistency) just to get lift, which can be solved by the angle of attack of a wing (shimming). So if the front wing has really good lift in the forward position, realize that moving it to the back position will decrease lift. You will need to shim the rear wing to regain the lift that you like. Without doing this, you will not be fairly comparing the quickness, take-off, and overall stability of the wing placements. So what might you notice wing a front wing in the forward position versus the back position? A wing in the back position might feel a bit more stable and a bit more predictable on take-offs and landings. As you move the front wing forward, the center position (center of mass) of the ski actually changes a bit. It is kind of difficult to explain, but imagine just sliding your butt off the back of the seat a little bit when riding on a straight trailing edge front wing setup. You are sitting further away from the front wing (center of mass), so you either need to compensate by leaning forward or using foot pressure to keep stable – it’s not that the ski is too lifty, it is just a different way to ride. So moving the front wing in the forward position will make the ski feel a bit touchier versus the front wing being in the rear position. You may find yourself needing to use foot pressure more in order to control the actions of the ski. Having the front wing in the forward position (moving center of mass forward) the also makes skidders easier since you don’t need to slide your butt off the seat as much or push out with your feet as much. So with the front wing in the forward position, you’ll generally feel quicker and steeper take-offs (more pop) with less effort. The downfall is that the steeper take-offs might be a bit tougher to keep consistent (too quick-variations in steepness), and you may need to fight the foil from popping back up on the not-so-perfect landings. With the front wing in the back position (after you’ve re-shimmed the rear wing for proper lift), you’ll generally feel like you have to do a bit more work to get the foil go as steep as compared to the front position. The upside is that you may feel a bit more in control because you are doing more of the work versus the foil doing it for you. This could lead to more consistency on the take-offs, as well as the landings. In general, you will control the foil more with your upper body movements versus foot pressure, since you are sitting closer toward the center of gravity. Now, the different front wings have different amounts of material sticking out in front of the fuselage. Here are some examples of wing positions on the LE38 (measured from the tip of the fuselage to the front wing. 1 ¼ inches - Straight Trailing Edge
Wing (Back Position) So realize all of the different variables that are changing when you move the front wing forward/back and remove trailing edge material (straight, mini-bat, batwing)…lift, responsiveness, center of gravity, take-off steepness, take-off effort. Too much of any of these variables will cause instability, which causes more crashes, which causes less aggressiveness and confidence in your riding. Properly test all of the different placements until you find the right balance for your riding style! Quick Summary of Options: Remove Trailing Edge = Added quickness, looser feel left/right or side-side Front Wing Forward Position = Center of gravity moved forward, less effort to go steeper on take-off, more lift Front Wing Back Position = More stable center of gravity, more effort from the rider to go steeper on take-off, less lift Rear Wing Forward Position = More quickness (small lift amount may occur) Rear Wing Back Position = Less quickness (small lift amount may occur) Positive Lift Shimming = Pointing the leading edge of the rear wing down moves the leading edge of the front wing up for more lift Negative Lift Shimming = Pointing the leading edge of the rear wing up moves the leading edge of the front wing down for less left Final note about shimming… The great thing about shimming is that it is a really easy way dial in the lift of a foil when you are making wing changes or the water conditions change. The downfall of shimming is that you have to mess around removing the rear wing when you could be riding! Another downfall is that it does increase drag. Granted, the drag that you create by shimming is pretty minimal, but you REALLY notice drag if you greatly change the angle of the rear wing. You will most likely never run into a shim induced, major drag problem, unless you are designing experimental foils, but the fact is still there. If you get your setup dialed in and you would rather not have a shim in the rear wing, tuning the leading edge of front wing can increase or decrease lift by a small amount. It could be just enough that will eliminate the need for a shim in the water conditions that you mostly ride in. For more information on tuning, please refer to this tuning guide. |
| Written
by: Jason Pandolph |
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