Report KD 698 has been added at the menu KD-reports. The tittle of this report is: “The Gö 227 airfoil for use in windmill rotor blades”. This airfoil has a lower side which is partly convex and partly concave and manufacture of windmill blades with this airfoil therefore requires special skills. However, the airfoil has special qualities.
Report R-443-D has been added at the bottom of the menu KD-reports. This report is written by André Hageman in 1980 when he was working at the Wind Energy Group of the University of Technology Eindhoven where I was working too at that time. The report is no longer available but someone has sent me a copy of a scanned version of it which is now available on my website. The tittle of this report is: Catalogue of Aerodynamic Characteristics of Airfoils in the Reynolds number range 10^4 – 10^6. This is an important report as it contains aerodynamic characteristic of a large number of airfoils.
Originally, the manuals of the VIRYA-1.04, the VIRYA-1.36 and the VIRYA-1.81 were divided into part 1 and part 2. This was done because the file of a complete manual was too large to put it on the website. However, at this moment, a new version of WordPress is used which allows files of 25 Mb. So now the complete manual is given in one file.
A new chapter 7 has been added to report KD 532 about the VIRYA-3.1 rotor. In chapter 7, the starting torque coefficient has been calculated more accurately using formula 3 out of KD 697.
Report KD 697 has been added to the menu KD-reports. The tittle of this report is: “Determination of the starting torque coefficient Cqstart for constant chord and tapered blades”. The starting torque coefficient for a tapered blade appears to be about a factor two higher than for a constant chord blade for rotors with the same design tip speed ratio. This report replaces the note “Comparing starting torques – – -” which was written earlier about this subject.
Report KD 696 can be copied for free from my website at the menu KD-reports. The tittle of this report is: “Summary of the most relevant wind tunnel measurements presented in report R 408 S from 1979, performed on a scale model of the CWD 2740 rotor”.
The note: “Comparing starting torques of constant chord and tapered blades” has been added at the bottom of the menu KD-reports. It appears to be true that rotors with constant chord blades have a somewhat lower starting torque coefficient than rotors with tapered blades if both have the same design tip speed ratio. However, constant chord blades use much less material and are much easier to manufacture.
This note has been cancelled and replaced by report KD 697.
Report KD 97 from 2002, in which Cq is determined for low values of lambda, has been reviewed. Typing errors have been removed and some references have been changed to more recent KD-reports.
Report KD 652 and KD 653 about the VIRYA-3.6 and the Polycord transmission have been replaced by report KD 693. The tittle of KD 693 is: Calculations executed for the 4-bladed rotor of the VIRYA-3.5 windmill (lambda design = 4, stainless steel blades) meant to drive a centrifugal pump through a Polycord transmission with an accelerating gear ratio 2.5 : 1 and a vertical shaft in the tower.
Report KD 285 about the Gö 711 airfoils has been reviewed. A new chapter 4 has been added in which the moment coefficient Cmh is given around point H which is lying at 0.3 * c from the airfoil nose and half way the blade thickness.