Kindof a basic question here. Is “foil” the bottom contours between the rails? Like say, nose concave or V in the tail? Thanks, and sorry if my elementary questions are a bother.
Alex - Picture a cross section of an airplane wing. The thickness curve starts with a down-turned egg-like apex at the leading edge that flows back staying relatively flat on the bottom side and domed on the top. The thickest part is approximately 1/3 of the way back. The rear 2/3 of the cross section tapers to a thin trailing edge. That thickness curve transition is “foil.” In surfboards, “foil” refers to the thickness transition in the cross section of a fin or rail contours from nose to tail. The term also applies to propeller blades, sails, etc. Not really elementary - a key element of surfboard performance that I wish I understood better.
If you were to remove the stringer from a shaped blank and lay it flat, you would have a great view of that boards thickness from nose to tail, and that would be it’s foil.
Thanks alot guys. I must say, I have learned more than I ever thought I could from this site, I can’t thank you guys enough.
Kindof a basic question here. Is “foil” the bottom contours > between the rails? Like say, nose concave or V in the tail? Thanks, and > sorry if my elementary questions are a bother. Curses foiled again! Some on! I don’t want to start watching TV Get this thing up!
Here’s my understanding of foil, it might be false or incomplete : To me, foil refers to how thickness along the stringer spreads out lengthwise, how the board gets gradually thinner towards nose and tail. Overall, more thickness means to me more flotation (easier to paddle, harder to sink) and more strength (I think I’ve read something like 1/2 inch more thickness means twice stronger). However, by increasing thickness you also give up sensitivity and thin rails (a compromise might be to use a domed deck). Foil usually goes as follow : - max thickness near chest area, for easier paddling - very thin towards the nose, to get low volume to make duckdiving easier and low weight for radical moves - very thin toward the tail, for greater sensitivity and down hard rails. On traditional clark foam/polyester boards, thinner ends might have something to do with flex (less with EPS/epoxy boards that act more like a shell than a core). Thinner ends (along with pointed nose) also make boards look sharp and cool in the shop. My opinion is that today’s board are too thin for the average surfer like me. As in many sports (take sailing, for instance …), design follow trends/fashions according to what professionnals ride rather than what most people need … Then my reasoning goes as follow. I ride longboards and large eggs, nose rides, tube riding and smooth carving. I want paddling power and like to play with hollow sucky waves (board snappers…). 1. I want a strong board, therefore thicker nose and tail would help 2. I don’t ride shortboarts, I don’t really need flex that much 3. Do I need a thin nose if I’m not going to duckdive the board anyhow and neither will go into radical, vertical splashy surf. 4. A tail a bit thicker could help a lot in catching waves (watching surf movies with underwater images, I’ve noticed how sunk tails are when paddling) Am I reasoning wrong in preaching towards less foil ? Wouldn’t it be better for a lot of surfers ? Then why nobody else seems to think that way, could it be because it wouldn’t look as sexy or maybe because close tolerance blanks can’t allow these shapes ?
Curses foiled again! Some on! I don’t want to start watching TV Get this > thing up! Along with the above definition of foil, there is also lateral foil which is from rail to rail at any given point.
I guess it could be said that technically, the foil changes from nose to tail as you progress from the stringer to the rail edge. If you sliced a board from nose to tail at the stringer, then moved out say 1/2" and sliced, then another 1/2" and so on… each slice would reveal a different foil. So what happens is that the overall thickness along the stringer represents one foil and the outer rail contours would be quite different (and maybe more important since that is the blade that slices through the water while turning and trimming.) I tend to believe that the fine tuning that goes into thickness proportions and rail foiling plays a huge role in how a board rides. Obviously, you can’t ignore rocker, template, bottom curves and fins but foil… mucho importanto!