IMCA Forum

Doug:

Jon and I have thrown around a few ideas so far and the following has come to light:

The whole point of the wing is less drag and more lift.

# Yep.

The extra lift comes throught the 2 elements and the slot effect.

# The two also form a cambered shape (think main foil with flap down generating more lift) but the slot also plays a large part in the performance of the wingsail

The wing needs to be easily twisted and cambered so that it is working at an optimum all the way up.

# Correct. thats what the "arms" that stick out of the aft element control. this is linked to a series of controls on the boom by ropes.

It need to be light and strong enough!?

# Oh yeah. especially given that this project will be adopted by home builders this is a big (the biggest?) problem to overcome

It needs to be totally controlable so the shape and twist can be adjusted.

# the control shapes at the bottom are critical here

Minimum drag is achived throught choise or the right sections, quality of build and control settings.

#We have found a "standard" set of cross sections that has worked on the c class cats effectively and propose this as a starting point until we get an aerodynamicist on board

It has a front structural leading edge that is designed to twist.

#This was my first thought but now I believe it is incorrect. We will need a mast tube from the step to the hounds. this will take the bending loads for the wing and the leading edge will resist the torsion. the webs of the leading element rotate about the tube to generate the twist.

It has bulkheads to keep the shape.

#Yup. Propose we call these webs as they will have lightening holes etc... bulkheads are solid (sorry this is a really pedantic interpretation)

#The aft sail is thinner and less strong but is basically the same as the front mast (sail) bit.

The aft sail (element?) is a different section as it is operating in a different flow field due to the acceleration of the air in the slot.

The required controls are:
Twist of the 2 elements. This means 3 or 2 positions where twist is limited (induced)?
Slot gap size. #Adjustable on water?? or should this be set and forget?
Angle of the 2 elements to each other and their position. - c#ontrol arms
Angle of attach of the whole wing to the wind. - #mainsheet

What am i missing here? Not much mate!

I'll try to work out how to link the pdf of the Patient Lady control systems PDF. That explains a lot!

Cheers

Colin