Hi,
I am designing a foil for my windsurfer and need a little help. My design is resulting a larger foil then I am finding in designs online. Am I missing something, do I have bad assumptions, or other errors? The kitefoil described here www.seabreeze.com.au/News/Kitesurfing/How-to-make-your-own-Hydrofoil_8649403.aspx has an approximate takeoff speed, for myself/board, of around 11 knots (assuming lift coefficient of 1.2) which is too fast. I can simply scale it up to get the speed down but quadrupling the size seems excessive. I have also looked at windfoils, such as AHD and Horue and they seem to be a lot smaller than what the math says I need to make a foil.
Below are some details:
-My kit and I weigh about 200 lbs (91 Kg)
-I am guessing that I can reduce weight by ~20-30lbs (9-13.5kg) by pulling the sail to windward to lift myself and the board a little requiring foil lift of ~170 lbs (77kg)
-I am looking a fairly cambered foil shape to get lift coefficient of 2 with a 7 degree angle of attack and this seems aggressive
-I am assuming that I can sink the tail to boost the lift coefficient temporarily
-This results in a takeoff speed of ~6 knots with a main foil that is ~2500 cm^2 vice the kitefoil from the link above that is ~600cm^2
Any thoughts on where I am going astray are much appreciated.
Thank you
Scott
Select to expand quoteScottD said..
Hi,
I am designing a foil for my windsurfer and need a little help. My design is resulting a larger foil then I am finding in designs online. Am I missing something, do I have bad assumptions, or other errors? The kitefoil described here www.seabreeze.com.au/News/Kitesurfing/How-to-make-your-own-Hydrofoil_8649403.aspx has an approximate takeoff speed, for myself/board, of around 11 knots (assuming lift coefficient of 1.2) which is too fast. I can simply scale it up to get the speed down but quadrupling the size seems excessive. I have also looked at windfoils, such as AHD and Horue and they seem to be a lot smaller than what the math says I need to make a foil.
Below are some details:
-My kit and I weigh about 200 lbs (91 Kg)
-I am guessing that I can reduce weight by ~20-30lbs (9-13.5kg) by pulling the sail to windward to lift myself and the board a little requiring foil lift of ~170 lbs (77kg)
-I am looking a fairly cambered foil shape to get lift coefficient of 2 with a 7 degree angle of attack and this seems aggressive
-I am assuming that I can sink the tail to boost the lift coefficient temporarily
-This results in a takeoff speed of ~6 knots with a main foil that is ~2500 cm^2 vice the kitefoil from the link above that is ~600cm^2
Any thoughts on where I am going astray are much appreciated.
Thank you
Scott
Don't even go there.. Apparently foiling with a sail board is old and no one likes it according to Mark. Missed the boat this time by the looks. I was interested too in putting a foil on my sail board, but no i got the red light from Mark who is apparently a sail board "expert".
Rob.
