4 blades propellers

[pmdec]

Hi,
Could somebody explain me how are made the 4 blades propellers (or point some dedicated site ?) : I can't imagine how are disposed the different layers ...
Sorry for my pour english,
PM

[dbahnvt]

Here's a picture from a Paragon catalog showing the construction principle of a 3 blade propeller, which they felt had a much stronger hub than a 4 blade.

http://pics.woodenpropeller.com/threeblade.jpg

Most of the 4 blades I've seen have had a similar type of arrangement, using a square step-cut instead of the tapered cut shown above. The 4 blade hub does have some inherent weakness, however.

[pmdec]

Thank you for your answer (and sorry for the delay of this !)
PM