| Many of you have a 'favorite bladecalculator',a magic box that say you what to do,kind of oracle maybe.Well,everyone his religion,hope I don't hurt anyones in this matter.
I stole a picture from someones files,this is nothing personel,it's just a wonderfull illustration of what mean.The maker of this blades did a great job and I thank him many times for sharing his work.
At the moment I saw this blades I found them quite weird,and maybe I was not the only one.But no one of the commentators had real objections,No reason for that if the bladecalculators tell to do it like this.
But the image of these blades kept wandering in my head and it took quite a time before I found out what's wrong with it.
The profile of the airfoil is relatif to a circular movement,so the profile must be wrapped around a cilinder.
This is not of real importance at greater diams,but nearer the hub this is taking much importance.
Now,I won't say that there isn't any 'intelligent calculator'that take in account this complication.But the only way to know this is when the maker of the calculator explains how he is calculating.As long as he doesn't do this,the possibility that the maker of the calculator is more stupid than you are is real.
Calculating the angle off attac,anyone can learn it.Be the blades wide at the root and thin at the top,the inverse or equal width over all the length,can be a religious question,but a little understanding is worth more than a thousend calculators.
cheers,
jaap |
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