Aluminium propellers will normally bend back into shape without trouble. If you have the facility, it's a good idea to anneal the blade before bending back to original shape. To do this the blade needs to be heated. Generally, 300 to 400 degrees celsius covers a range of alloys to produce sufficient stress relief. Fortunately there is a simple way of checking the temperature, rub some soap onto the blade and while heating the blade the soap will change colour - brown to black - you need brownish. After black there is no more change in colour but the blade will melt!
When you work the blade back into shape by hammering, it will reharden to some extent and it will continue to age harden after that - initially very quickly - so the following day it will have hardened sufficiently for you to use it.
Carefully tapping the blade back into shape is the way to do it, an anvil or a hard wooden block to hammer against would be good. Make sure the face of your hammer is in good condition or you will impart the hammer face pattern onto the propeller blade with every impact. Plainly, if the hammer face is polished, so will your propeller be polished! Use one of the good blades as a template. If they're all bent, guesstimate from the least bent blade using you new propeller as a guide.
Finish off by filing smooth followed by sanding and painting.
On the plus side, it's very much easier than it sounds. Give it a go, you know you want to!
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