Effect of rider weight on wing size

Hi Guys

I've decided to have a go at building a foil, thanks for all the good advice on here. I've been following the design guideline posted by Franckite for his foil (Eppler 817 profiles for wing and stabiliser, 66cm wingspan, 12.5cm wide on the centreline ) but was wondering what compensation if any I needed to make for rider weight, as I'm close to a 100kg and most other riders on here seem to be around 60-70kg? My initial googling seems to indicate that lift is proportional to wing area and should be scaled up proportionately to rider weight?

My current wing design has a projected area of 650cm^2.

Also, it wasn't quite clear whether the stabiliser profile was placed upside down (reverse of the main wing)?

Thanks in advance for any help

Regards
Mark

Hi Mark - Chris Middleton here, the average SA of the front wing is between 650cm squ and 580cm squ. Obviously the smaller the SA the faster you have to travel to get the foil into motion & flying.
I'm circa 100kg and 580 works fine for me in fact the faster you go the less SA you need so it's a fine line between going large on the front wing or smaller depending upon the conditions. I think your projected size may be too large - as I said previously it depends if you're planning on sailing in super light winds and then switching to a TT or directional board?

The original AirChair and Carafino's inverse the rear wing (Intrados : flat non concave side facing to the top but a profiled foil on both sides provides a sweeter glide through the water. You'll need about 1.5° of negative AoA on the rear wing. This is something you will need to try and modify to suit your riding style and weight - one foil set up will not suit everyone. As you rightly stated weight, wing strength, riding style and water conditions all contribute to your foil set up - it's a bit of suck it and see, try and test to get it dialled.

Hope that helps a little ;-)

Thanks Chris, that helps heaps.

I don't want to spend a fortune on carbon for something that won't work!

Cheers

My foil is coming on well, front wing complete-came out pretty good.  I have a question for the foil experts-the front wing came out about 3mm thicker than the design profile due to excess material not allowing the mould to close-should I attempt to sand this down or can I live with this?  Also, how "sharp" should I go on the trailing edge-currently about 1-2mm thick at trailing edge?

Photos of progress below - Foil design based on the Franck blueprints

Thanks

Hi phezulu1 !

If your wing is thicker finally 3mm only and you want to use it at "normal ridind speed" (not for beating speed records), you can keep it like this, since the profile is almost respected.
You can sand it later if you feel that you need more speed.

Thank you JMB- that's very useful information. For now I'll be very happy if it works and stays in one piece and I can ride it-I'll chase the speed records later  

Nice front wing phezulu1 !

Here are a few questions.
Have you CNCed your core ? Which material ? Have you used some vacuum technique ? If so, which values ?
How many carbon layers ? Which CAD sw have you used ?

You need to be more precise when you'll make your stab (back wing) since thickness is much more important... (needs to be 10mm max) with a good inverted profile and the right angle of attack, that fits well with your front wing.
I remember you Franckite24's method :
Front wing angle = 0° then tune stab angle from 0°, -1, 2°... since you have a good "front-back balance" on your foiler.

Thanks JMB that is incredibly useful information, I'm busy with the stabiliser rear wing this weekend-I'll make sure I get it more accurate-the foam blanks are very light and thin relative to the front wing.

MIC29 I used hot wire cut foam shapes for the wing plugs which are then pulled over a curved "rocker table" and then used to make the female moulds (this method is well covered in the French section). I used Autodesk inventor (have it at work) -you can generate your airfoil profiles here: http://airfoiltools.com/ and then download the CSV file (an excel file with co-ordinates for points). You bring the CSV file into CAD and then put a spline through the points- and there's your wing airfoil profile. You can then extrude, loft or sweep this to get the 3D shape.

Thanks for all the help guys-it's a bit of puzzle to put all the bits of information together.