Has anyone on the forum had any experience of straightening bent prop blades.
I have acquired a prop blade that is made out of some sort of Aluminum alloy, unfortunately as a crash recovered blade it has a slight bend in it.
Do you know if there is recommended way of straightening the blade or will it just snap, if it were a Steel blade I would try warming it up, but being an alloy of some kind i wasn’t sure if this would help in any way.
All advice will be gratefully received.
Septic.
By: dhfan - 27th September 2005 at 07:03
A valid point John but don’t forget the initial bend work-hardens the immediate area. Bending it back again will harden it even more. I have nowhere near enough technical knowledge to know at what point or degree of bend it would have to be annealed.
I imagine there was once an official repair manual or the like which would probably state what severity of bend could be straightened cold.
There’s probably also a difference between what’s OK to hang on a wall and what’s safe for flight.
By: steve_p - 27th September 2005 at 07:02
A few months ago I was reading about a WW2 UK repair unit that specialised in straightening the prop blades from crashed aircraft. Unfortunately, I’ve forgotten the name and loacation of the place. 😮
Best wishes
Steve P
By: setter - 27th September 2005 at 06:53
Hi Guys
Well think about it – they bent in the first place – thats why you need to straighten them so it should be possible to straighten them out . I have seen a lot of crashed blades but seldom seen snapped ones.
Regards
John P
By: dhfan - 27th September 2005 at 06:14
I’m glad it worked. I know forgings are relatively tolerant to bending and straightening but I don’t know how tolerant. 🙂
By: Septic - 26th September 2005 at 23:35
[QUOTE=dhfan] However, it should be a forging so if it’s a only a slight bend it should be possible to straighten it cold.
Spot on dhfan,
I took the blade to an engineer I know this evening who confirmed its construction as a forged alloy, after a certain amount of deliberation he managed to straighten it in an old hydraulic press after applying tons of pressure to the relevant spot albeit in a measured way. I now have a rather nice ME109 VDM prop blade in my collection.
Anyone got a spare hub!
PS Thanks Cees, I must admit the forged alloy blades are more flexible than they first appear, I half expected it to snap. Must get up to Elvinton soon.
Septic.
By: HP57 - 26th September 2005 at 18:57
All I can add is that Tony Agar straightened his pair of De Havilland props, which came from a crash site and were severly bent. They didn’t break obviously looking at his magnificent Mosquito NF II restoration at Elvington.
Perhaps you can contact him for more information. Having met him I can tell you he is a great bloke.
HTH
Cheers
Cees
By: dhfan - 26th September 2005 at 16:31
I don’t know anything about prop blades but I do know a bit about aluminium alloys.
I suspect the original, and correct, repair method would be to anneal it, straighten and then re-heat treat it. However, it should be a forging so if it’s a only a slight bend it should be possible to straighten it cold.
I suppose it’s possible it’s cast but I wouldn’t think a casting would be suitable for the job. Somebody will no doubt now inform me that manufacturer X has used cast blades since Moses was a lad. 🙂
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September 26, 2005 at 9:37 am