Amazing photo of P47 with damaged prop.

Maybe then, just maybe, if you hit a hollow Curtiss-type blade centrally, the edges which are essentially two steel ‘angles’ will be rigid enough to hold the thing together while the centre ‘explodes’ spectacularly? Of course we may not be seeing the hundreds of non-central strikes, with blade outers twisted off and a subsequent catastrophic effect? Just the three lucky ones that caught the blade centrally? And I guess it might only work like this with these Curtiss hollow blades – forged alloy solid blades might well react differently – hence the predominance of P-47 examples? Maybe I was too cynical initially.

And for comparison, what looks like B-17 prop damage.
3.03

20mm

Yes, Curtiss 836 blades, made from two curved sheets welded along the seams, and hollow.

That’s a very interesting hole in that propeller blade!

Now that hole has got to have been formed by a high-explosive cannon-shell, I’d say a 20mm round, but it is interesting that the ‘petals’ around the hole on each side of the blade are bent in the same direction, and there is a huge difference in size between the two holes. Presumably the round was travelling from the rear, through the blade, towards the front so the smaller hole was formed first. So what were the mechanics of that explosion?

It seems as if the expanding pressure-wave caused by the exploding cannon-shell was travelling forward (at considerable speed) so burst the smaller hole from outside the blade and then burst the larger hole from inside the blade but somehow didn’t burst ‘backwards’ enlarging the first hole and bursting the petals out towards the rear!

Hi CD

Presumably the damage was caused upon the cannon shell exploding upon first contact with the prop blade ie upon hitting its rear surface.

I have no idea as to the construction of such blades (are they hollow, or solid, or filled with some other material between metal outer skins?) but if the blades are aerofoil shaped they would look something like this: () in cross-section?

As such, the explosion would be hitting the rear skin of the prop as a convex surface but would pass through and hit the front skin (from behind) as a concave surface.

I am simply taking a guess with all this but maybe the different shapes of the two faces of the blade (relative to the shell-strike) would account for the difference in the ‘petals’?

And if the blade wasn’t just hollow then maybe any material inside would have been blown forward by the explosion thus creating even more damage when it contacted and burst through the front skin?

Just a thought.

Ian

..and another one – from here – http://collections.si.edu/search/results.htm?q=record_ID%3Asiris_arc_370855&repo=DPLA – but apparently taken by Curtiss Wright themselves (the blade manufacturer)…

[ATTACH=CONFIG]244572[/ATTACH]

Slight roughness, my xrse.

Remarkably similar damage!

It would seem to be a P-47 thing, then! Would have been a LOT of vibration due to the massive imbalance. Unless the blade wasn’t turning. Those scratches appear to be going in the wrong direction? At least for a RH turning prop (anticlockwise from the viewer).

/P-47N Pilot Lt. Ellis Wallenberg Of A 7Th Aaf Fighter Squadron In The Ryukyu Retto Was Hit By A Jap 20 mm

So you suspect that the holes were deliberately blown in the blade for the publicity (propaganda) value of the photograph and that the aircraft never flew with the blade in that condition?

I did marvel somewhat that the blade had held together; not so much that it withstood the radial forces but that it didn’t fold forward under the pressure of the air!

I wonder.. he was already known as the guy who’d been hit by flak and survived six times. I wonder how.. ahem.. ‘organised’ this PR photo was?

Had instantly the same impression…

I wonder.. he was already known as the guy who’d been hit by flak and survived six times. I wonder how.. ahem.. ‘organised’ this PR photo was?

That’s a very interesting hole in that propeller blade!

Now that hole has got to have been formed by a high-explosive cannon-shell, I’d say a 20mm round, but it is interesting that the ‘petals’ around the hole on each side of the blade are bent in the same direction, and there is a huge difference in size between the two holes. Presumably the round was travelling from the rear, through the blade, towards the front so the smaller hole was formed first. So what were the mechanics of that explosion?

It seems as if the expanding pressure-wave caused by the exploding cannon-shell was travelling forward (at considerable speed) so burst the smaller hole from outside the blade and then burst the larger hole from inside the blade but somehow didn’t burst ‘backwards’ enlarging the first hole and bursting the petals out towards the rear!