We have had a few questions about the Horan Star Fin and about winglets added perpendicular to the fin foils. Here’s an article from the Daily Sail on how International 14s are utilizing a variation on this concept on their rudders and how it affects the trim of their boats. Check it out: Foils At present no one seems to have taken the development of daggerboard foils further, but current thinking suggests that you are nowhere unless your 14ft beast has some form of T-foil arrangement on the rudder. Following on from Bieker’s experiments at past World Championships, there was some home-grown development mostly using the skegs from windsurfers. Today, as with hull development, foil technology mostly falls into the Beiker or Morrison (more accurately Richard Woof) camps. T-foils - Variations on a theme… The Morrison arrangement last year had the T-foil at the bottom of the rudder, the theory being that this provided an endplate effect for the rudder. However on this year’s incarnation it has moved half way up the rudder like the Beiker arrangement. “We’ve stopped using them at the bottom because the boat is narrow and you do sail it at angle of heel occasionally. With the foils at the bottom they tend to capsize the boat. They are just further down and have a bigger lever arm to work on,” explains Richard Woof. The standard foil shapes are slightly different. The latest Morrison ones have a bigger span and narrower cord, while the Biekers tend to have a slightly greater cord and come in symmetrical sections or a smart looking asymmetric type, vaguely ressembling the shape of a whale tail. Above: Chris Turner’s Bieker T-foil Most significant of the differences between the two types is the mechanism used to alter the pitch of the T-foil. On the Bieker the T-foil moves relative to the rudder thanks to two long rods that run down the inside of the rudder. One is spring loaded and attached to a lever at the top of the rudder. The spring mechanism keeps the foil in the neutral or negative position while cranking down on the lever applies positive pitch to the foil. A downhaul is attached to the end of the lever and this runs forward up the boat to a double ended purchase and from there out to the racks where the helm can trim the foil. The rods running down through the rudder have a thread and so can be wound in or out to fine tune the degree by which the foil operates. The latest Morrison/Woof system has a T-foil rigidly bonded to the rudder. The pitch of the T-foil is altered by pivoting the entire rudder blade relative to the boat using a type of slack gudgeon and pintle system. The advantage of this system says Richard Woof is that the foil is fixed to the rudder and no internal mechanism is required, hence foils with a thinner cord and therefore lower drag can be used. The rudder is kept in its default position by bungy running forward along the bottom of the cockpit. “The stock is rocked by the interference of a metal plunger in a socket on to the rudder axis which pushes it aft in a slot,” explains Woof of the detail of the inclining mechanism. “That’s operated by a small cascade in the floor of the boat through a flip-flop block. It is very simple and easy to graduate.” The latest Morrison foil is 1.1m wide, narrow and very thin. “There are practical limitations,” says Woof of the size of the foil. "The boat is quite narrow and there are certain points of sail where it is impossible to sail the boat flat. And at that angle of heel, the T-foil breaks surface. We’ve seen it looking back at us! T-foil arrangement on Andy Partington’s Morrison 11 “We’ve tried some innovations this year with an upside down Y foil. It was fantastically efficient but as soon you put any angle of heel on the boat it felt that there was somebody on the leeward rack trying to pull us in.” However he adds that the 11 is just an interim step and there is more development in the pipeline… Another variable is how much pitch can be applied to the foils. The amount required obviously depends upon the area of the foil and the larger area of the Morrison foils suggests they need less pitch. Richard Woof says their foils can be varied by around 5 degrees - 1.5-2 degrees of negative (ie pushing the stern down) and 3-3.5 of positive (ie providing lift). The Bieker foils can have as much as 10 degrees of pitch applied to them. Again the foils can be set to either lift or sink the stern, biased towards the former. How the foils are used Asking those sailing the 14s how they use their T-foils the answers vary greatly, although this is also due to the variation in the set-ups from boat to boat. In theory there is a maximum amount of lift you are ever likely to need. “You don’t increasingly want more of it,” confirms Richard Woof. “It is only 14ft long and you need to maintain a certain amount of equilibrium in the boat!” Considering that the lift generated by the foil increases as the boat goes faster then less foil should be needed in windier conditions. Equally somewhere at the bottom end of the wind range there should come a point when the foil will be creating more drag than lift and should be neutralised. In our brief poll of 14 sailors there seemed to be a small degree of “new toy - will use”. So the slab-handed are tending to wang it on most of the time, conditions be damned. Conversely “as it gets windier we use less of it,” says Zeb Elliott of his Bieker 4 foil. “In light winds we use it pretty much all the way round the track. When it’s full foam up we tend to ease it back. It’s really upwind that makes the difference.” “4 degrees - just to stop the pitching,” says POW winner Rob Greenhalgh of how he uses it on his Morrison. “We normally have it off downwind to stop us going down the mine!” Woof counters this saying that downwind in light conditions it is appropriate to use a small amount of T-foil lift to reduce the wetted surface area of the boat. Even if there are variations on how the T-foils are used, what is certain is that they have a definite effect and have improved performance. They dampen the boat’s pitching. This stabilises the air flow over the rig, increasing the efficiency of the sailplan. Adding stability also makes it easier for the helm to trapeze in awkward conditions and as mentioned yesterday they have made the narrower more slab-sided Biekers easier to sail. Most profound is how T-foils have dramatically altered the way 14s are sailed upwind. With the T-foil developing lift the crew now can trapeze from the back footstraps while sailing upwind with the boat sailing almost on its T-foil alone (see the photo at the bottom of this page). It moves! (If it doesn’t move - click to refresh) This is a variation on the Morrison theme For all their bonuses a side-effect of the foils is what happens to them when the boat heels. Generally heeling the boat causes the T-foil to increase the amount of helm. While this could be seen as a downside, Dave Spragg says that this accentuation of the helm gives the boat much more feel and makes it more obvious when you are not sailing it right. It is also felt that this feature has made it easier to get the boats to turn corners. Being relatively weight-less 14s are similar to catamarans in stopping dead during tacks. In our poll we didn’t speak to anyone who has applied negative lift to their foils, although all the foil arrangement seem set up to offer this. The only occasion it is felt you would want to sink the stern would be to help keep the bow out of the water blast reaching in big conditions. Aside from the bit in the water, future developments are in hand to improve the controlling mechanism for the T-foil. One neat development is the prospect of being able to control T-foil pitch using a motorcycle-style twist grip fitted to each tiller. Tomorrow we look at the latest developments above the deck and what lies in store for the International 14 class The most obvious effect of the T-foil is sailing upwind. See how far aft the Boy Wonders are…
Tom!..Thanks for taking the time out to copy that article. very interesting. much appreciated! T.
The Starfin’s winglets are not perpendicular to the main foil. Most aircraft winglets also have a slight angle. Interesting article though. Why doesn’t Red-X offer fins with winglets?
Rob, You might have missed the part about too much foil with either heel on or too much speed became inherantly unstable. I believe in lower speed applications that don’t get on rail you could realize some benifits. But, for on rail aggressive surfing the concept is going to need to be varaiable to be worth while.
I don’t think the I14’s rudder experience correlates well to the Starfin. Sailboats have mcuh different dynamics and this thing is a rudder fixed behing the stern. Much different than a simple surfboard skeg. Plus the foils are half-way up the rudder and on extreme “hiking” I can see how the extra plane can wildly effect handling. I don’t feel this on a Starfin on long or short-boards, at any speed, during any maneuver. However, I think the Red-X fin base or a revised FU fin box may help manage the stress the Starfin puts on the box. (I believe you mentioned something about added stress in the Surfer Design forum discussing double foided fins). -Rob Olliges This is NOT a surfboard! 
No it definitely is not a surfboard. And, yes Star fins are angled instead of perpendicular. But, you can draw some simularities from a planing hull skiff and a surfboard. One of the key problems the I14 people found was that when the T-foils were positioned at the bottom of the rudder, they got too much leverage and would wipe out. I believe that a Red X box would handle the loads better than any other system with a comparable schedule of laminate. But, I repeat, they will probably work better in single fin longboard applications for small to medium sized surf. Red X has been primarily focused on high performance applications. When we made O’Fish’l we spent alot of time and effort on longboard apps.
very interesting article… so the effects seem to be 1) produce lift in controllable amounts, which can 2) change the center of gravity & “angle of attack”, 3) dampen pitch changes, 4) increased stability, 5) increased helm… not all of that is applicable to surfboards - or at least not in a good way, I think. Most of these are control effects tied to the variable pitch, more than purely hydrodynamic drag-reduction… hard to picture using a variable-pitch wing on a fin while actually surfing…
My personal belief is that there are so many variables influencing the bottom of your board while surfing critical waves, that simple strong foils are the most efficient way to go. But, sometimes I start to go off on a what if tangent. What if you could induce some foil dynamics via disk in the center of your traction? The rider would twist his rear foot and vary either a trim tab or foil shape when desired.
certainly possible… as is microprocessors tied to sensors and servo motors – surf-by-wire… egads…
Tom and Rob, Fin dynamics are a constant curiousity. The notion that we may be able to articulate the fins on a surfboard is certainly not beyond the realm of possiblity. What different types of fins do by themselves and in combination is a facination thing to attempt to understand. It’s good to be along for the ride. Hey Tom do any of you’re rail fins have flex in them? How much? One thing I am fairly sure of and that is if you put the winglets on the tip of a fin at 60 degree angles off of vertical (Horan Starfin style) you have a fairly neutral effect on lift. What the fin to dampen the switch from rail to rail (the yawing affect) and it is also harder to break the tail free and the faster it goes the more locked in it becomes. When you put a fin like this toward the tail of the board it really is hard to turn it. Fins are the things on surfboards that are in the water most. They either give it performance or detract from it. Finlets, Finlets, where and how to put set them? Mahalo, Rich
Laird Hamilton: big waves; wake board; ski boots; foil at end of “fin.” But the really weird thing is that Phil Edwards mentioned this concept back in the 70’s during an interview published in Surfer. Takes a long time to advance. Try something new today. -Rob Olliges 
Rich, Different foil thicknesses have varying degrees of flex in our line. Also, we’ve tried some fins in different amounts of fiberglass fill. When people want fins with more flex we can provide them. But, We’ve found more demand in the “as little flex as possible” category. So, that’s where we are focused.
Foil Development: Paul Bieker (This foil was on the 2001 World Champion boat). The biggest limitation to the speed of a 14 upwind stems from the fact that it is a short boat with a sailing displacement to length ratio similar to that of performance keelboat. Even with its great power to weight ratio, the 14 spends a lot of time at transitional planing speeds upwind where wave drag is a large proportion of total resistance. Thinking about this, it struck me that, since the rudder on a 14 is aft of the boat in the approximate location of the stern wave crest when sailing upwindat moderate speeds, a hydrofoil could be used to “trick” the water into thinking the boat was longer. This was done by placing the foil in the middle of the rudder (closer to the free surface), giving it a positive angle of attack and a span approximately equal to the waterline breadth of the stern. The effect of the lift from the foil is to flatten the stern wave dramatically. It also significantly reduces pitching in a chop and allows the crew to stand further aft in the boat (thereby additionally easing the motion of the bow through waves). The angle of attack of the hydrofoil is adjustable from the rail so that it can be reduced at higher speeds upwind and neutralized (or made slightly negative) downwind. In twin wiring conditions the effect of the foil on upwind speed and pointing is significant, essentially allowing the boat to transcend some of the upwind limitations imposed by its length. The sailing conditions for the Worlds in Beer were generally too light for the foil to be effective. However, there was enough wind in the first three races for it to give the eventual winners (Chris Bundy and Jamie Hanseler) a marginal speed advantage. It was notable that the foil did not seem to slow them down significantly in light air. December 2001; (http://www.i14.org/boat/articles/bieker-rudder.html).