That helps a lot...anyway I am not new on airfoils and I know that the one describes in Piggotts book is far away from optimum. If you have time, one can start with rounding both sides of the leading edge in order to reduce stall and carve a little sagging on the front side...but those are Thinks that take time...for a few % of efficiency and for most folks it would be easier to just make the prop a few centimeters lager to compensate for that.
Over there in the US, people carve blades like hell. Over here they are scared of doing that as they feel it might be to complicated...Germans are strange when it comes to precission. It has to be perfect, not just close and they feel they cannot do this by hand...so they do not give it a try at all...
I personally like building props from wood, it is relatively cheap and looks nice and if something breaks, it can easily be fixed with epoxy or you just carve a new blade an thats it.
We do offer Hughs book and had it translated into german by greenstep.
Fpr people that are scared of making laser parts just like magnet discs and welding parts like the chasis, we offer cheap parts for that and also for the blades we would like to give some help. We do not want to offer completed blades. People want to have the feeling that it was them having made the blades :-) We just want to give some help on the critical parts.
A simplification by having the highest points of the airfoils on the same level (but of course keeping the angles right) and precut the the front section of the blade with a cnc machine will help those guys a lot.
I aleays remember when I made my first set of blades. I had an experienced guy teaching me and giving hints, Fritzblitz. He is also a member of this discussion bord, living in the middle of nowhere in the mountains of spain. I am not sure it would have worked out that well without his help. Some thinks you can read again and again and I would not understand it until I did it.
Precutting the with waterjet and moving the highest points of the lee side to the same level already deterines all the measurements needed. All there is left to do is to go don from that highest point towards the trailing an leading edge without having to meassure anything anymore. Everybody should be able to get a straight line done on the trailing edge and round the leading edge according to the right airfoil shape.
I feel that if precut sets were offered, many more people would give it a try.
The pre machining must not have do be complicated! In this case we would laminate the wood and precut it to the desired shape, then have it waterjet cut which is only needed on one side so that it is not nessessary to turn the piece over during process. It then can be made on a cheap 2 Axis machine.
It needs one single cut for the drop section on the front side and then the cuts that give the shape of the profile when viewed from the top. This really goes fast and should not be too expensive but it saves a lot of time and helps unexperienced guys.
Do not get me wrong here, we are not a commercial site: kleinwindanlagen.de
We are a discussion bord like this one with some specials that cost a lot of money. We opended a web shop to support these costs and the money does not go into private pockets- we do it in our free time after working to help people with their constructions.
I am saying this becaus we do not feel that we will sell hundrets of sets of blades. I already thought about building one of those machines and I have finished the plans as well....http://www.youtube.com/watch?v=LmtMQeoKCu8&feature=related
But I the realised that the efford is enormous and that there are easier ways...
I want people to have it easy finishing the blades with a minimum option of getting someting wrong but not to get a finished product.
I now have already build some blades and for really experienced people like Fritz who have built something like 50 Blades, it takes him about 6 hours to carve a complete set of 3 blades for a 10 feet turbine that then only needs paint to be finished. It would probably take me 2 days although I have experience...but it only takes me about halve an our per blade to do what is left after having it pre machined the way I suggested with a minimum risc left to fv(k it up ;-)
Thats how I approach it...