This topic on lift is the holy grail of windsurfing. The sail generates a bit of vertical lift (vector) as well.thats why l like to match my fin size for what ever sail l rig.from what l understand is the fin generates vertical & horizontal lift. The windsurfing term is simply called the vertically uplifting force.
I bought a 15/ 20 year old 36 cm carbon B4 Leading Edge fin from Windsurf Perth for 80 dollars.
Tried it out a few days ago with my 7m and my 65 cm wide 100 litre board but it felt too big and slow.
Felt like I was on a hydrofoil actually 
Lots and lots of lift but disappointing top end.
More lift usually means less speed.
Today,in 12-18 knots I put it on my 71cm wide 116 litre Manta with a 7.5m.
For the first hour I had the same issues - in the gusts I was getting lifted upright and therefore had average top end and my back leg was feeling it trying to harness the power of the fin and sail.
I came in and gave the sail a lot more downhaul,like I'd normally rig it were the wind upwards of 20 knots.
Bingo, I was able to stay down in the harness in the gusts and my top end improved heaps.
Older fins generally have thicker foils so produce more lift.
Do not really buy the belief that flexy fins produce more lift though. The Leading Edge fin is stiff as and it produces a ton of lift.
A fin that is wide at the base will aid control,sucking the board down. It wil also make the board less free - sort of keeping it on more of a straight path, almost like a railway line!
A fin with a narrow base will increase the lift and the board will be a lot looser to sail. Just my experiences with testing various fins.
Select to expand quotepetermac33 said.. >>>>> Do not really buy the belief that flexy fins produce more lift though. The Leading Edge fin is stiff as and it produces a ton of lift. >>>
Pete, I don't think anybody's said flexi fins produce more lift. It's just that because of the bend under load, there's an element of vertical lift from a flexi fin
Ok so if the fin flexes, in stead of the straight on in the diagram. It will bend towards the sailor at the tip, this will add a certain percentage of vertical lift, depending how much it bends and the angle of attack.
Select to expand quotejoe windsurf said..
Units? lbs and inches? I'd think 106 inches (2.7 metres) for the centre of effort of the sail above the centre of effort of the fin is on the high side?
I once posted about Fins.
Being heavy I asked for early planing , is it better to have a stiff or flexy fin , sizes being equal.
Stiff and something hard to push against or flexy mabee producing more lift ?
It went round and round in circles with no difinitive answer.
Mabee it's more complex and a preference thing.
I thought mabee the more fins I own will help.
It did and it didn't . It got more confusing but It did show the fins I didn't like.
There are soooo many variables , especially my skill.
I've come down to :
Big and flexy for light wind,
Medium and swept back for rough ,
Medium and stiff for every thing else ,
and a home made shallow fin for shallow and speed.
There is so much more for me to learn.
^^^ I think probably because it is too hard to answer - nobody makes identical fins in glass, G10 and pure carbon which people have then tried side by side with empirical evidence as to planing threshold.
The flex is a feel preference thing, but what is known is that stiff works way better once u r over about 30cm in freeride/ race etc fins..... and once you get into 40cm plus the flex in standard glass or G10 can be just horrid. IMHO as a poor freerider....
I'd like to see a moulded glass fin with 2 or 3 hollow carbon tubes down the guts, to make it a stiff fin like carbon layup, but at 1/3 the price...........
As I recall, top riders in formula prefer softer, flexing fins rather than stiff ones, as they give more control. If a flexing fin gives more lift, that seems to contradict the control issue. I have three 70cm formula fins, a Drake, a Curtis and a Deboichet. All are several years old, but the softest of the three, the Deboichet is by far the most controllable.
Rather than ... What is lift? .. the more important question is .... WHY is lift?
The existential view holds that we WILL our boards to both point higher and sit higher in the water. Hence our being is the sole reason that lift is created.
The materialistic view is that since we just forked out $350 for a new fin, we should now obviously generate more lift, whenever we want. This lift will only diminish when a new fin is released.
The quantum view is that lift is created from small particles called "Levitons". These are in abundance throughout the universe, yet always paired with equally powerful "Dragitons". We cannot create not destroy these particles, only steer them about.
Lastly, the creationist view. It was lift that both parted the waters and moved the stone. It also lifted water into wine. Lift is a gift from above that helps us to ascend!!!
Any other views????
I had some great lift last week. Too big a board, sail and fin in a big gust and I got "lifted" about 2 feet in the air and weather vaned. Now I know what lift is!!!
Select to expand quotepowersloshin said..
sometimes a picture is worth a 1000 words... 
Chief, how do i get in? Where are you n 99? Hmmm is this the entrance to KAOS HQ?
