Time for better blades

by Roderick Read in Airborne Windenergy Forum · · 4 Replies · View last reply Respond
Roderick Read
Roderick Read

I'm inspired by what you've done on the MAR project Christof.


I'm working on a similar design for daisy style. e.g. mounting a foam wing with a gen profile on rings instead of crossed spars.

Named Airfoil: fx63137sm Looks like a good generation profile... Where did your choice come from? Definitely prefer the idea of EPP over EPS.
Still very unsure of quite how I'm going to tackle this.... which is when I feel ready to start putting parts together

Roderick Read
Roderick Read

Going for super simple.

Will likely go for longer spans ~100cm made out of 2 joined sections.

I'll probably interface with the ring at around 2/3 span with 1 bridle to the outside @ around 20 - 24% and 1 inner bridle@ around 82.345%  will fix bridles through or around the spars

Might spread out the 2x holes for spars and spear the 2 spars through a block v close to the ring.

Time I got drawing, ordering and making instead of talking.


Christof Beaupoil Administrator
Christof Beaupoil

Hi Rod,

Can't believe you are going rigid :)

Have a look at the "Airfoil selection" paragraph of my "My Airborne Rotor 1 - Part 1: Design rationale" post. In short "It has been specifically designed for low Reynolds number applications on small wind turbines by the UIUC Applied Aerodynamics group as part of their Low-Speed Airfoil Test program." 

Let me know if you need any details!




Roderick Read
Roderick Read

Thanks for the link CB.

I know, I know, I know... well OK nobody seems to know, but.... Keeping a large radius with soft kites will be good for ring to ring tensile torque transfer... However...

The soft kites I tested so far (strictly speaking Semi-rigids with a leading edge spar) have only been running at very low TSR ... So alternately to rigids we could try and bump up the solidity by adding more semirigid kites around the same ring. 

Or we could try faster blades... Which can still be modularly arrayed... and by keeping the blades fairly small... their individual wing loading won't be too excessive, So they should do well across a large range of wind speeds (I fudgingly (new word) guess) and maybe even work on larger radius (and possibly soft) rings

Also I had a go of a single skin 2 line kite recently and wasn't as impressed with the low wind performance as I'd hoped.

But hey where's the fun if we don't keep experimenting with both?

Pierre Benhaïem
Pierre Benhaïem

Hi Rod,

I put the following link in another topic  https://infoscience.epfl.ch/record/207053/files/Costello_2015_JRSE_submission1.pdf, but It can be also useful here as you try to chose between rigid and flexible blades-wings. This paper indicates there is no obvious advantage for rigid wings in spite of their higher L/D ratio.