Oddly painted P-47 Prop

[Django]

Ever seen one painted like this before? Why did they do that?



from http://www.littlefriends.co.uk/

[Django]

That seems reasonable.

[CWBuff]

The pilot in the photo is Dick Hewitt, 82nd FS, 78th FG. If I recall a conversation we had correctly, he said it had something to do with weld lines, although he didn't expound much on it. I'm thinking maybe the marks were there to aid in spotting any potential failure in the welds? I dunno... perhaps someone in the know will chime in here...


Fade to Black...

[slinky]

I sent the pic around to all my armchair historian friends and here's what one had to say....makes sense!

The bare stripe on each prop blade is a weld line that has been ground flush or smooth for aerodynamic purposes. Curtiss Electric sent out field teams to the ETO to increase the performance of their 13'1" diameter propeller blades at high altitudes by welding a segment to the existing blade that increased the chord. The photo shows the weld line ground flush, but not yet refinished with black paint. This was explained to me years ago by Lt. Chuck Olmstead, a 354th FG pilot.
HTH,
Mike

[mlenoch]

That sounds reasonable.
Somewhere might there be a set of spec's or such for this 'field' installation?
Thx,
VL

[51fixer]

I sent the pic around to all my armchair historian friends and here's what one had to say....makes sense!

The bare stripe on each prop blade is a weld line that has been ground flush or smooth for aerodynamic purposes. Curtiss Electric sent out field teams to the ETO to increase the performance of their 13'1" diameter propeller blades at high altitudes by welding a segment to the existing blade that increased the chord. The photo shows the weld line ground flush, but not yet refinished with black paint. This was explained to me years ago by Lt. Chuck Olmstead, a 354th FG pilot.
HTH,
Mike

If you look close the yellow paint on the tip is in the same condition on both sides of the line. ie worn and chipped. There isn't any new portion attached to this prop. The way the hollow steel props were built IIRC is that the front and rear portions are brazed together. This process is done under high heat and typically in a furnace or even a vacuum furnace. One can't weld over a braze with too good of results. The weld will be contaminated and the braze filler will melt out of the brazed area.
i believe this shows the difference between the original and the wide chord blades. Other thing I considered was an area that needed some kind of inspection but why cover what you need to inspect with such a big mark.
Rich

[marine air]

Propellor blades arc, flex, twist, and stretch in flight. I can't believe it would be possible to weld anything onto blades like that. The slightest imbalances in weight would be magnified on the blades. I have seen people put another coat of paint on their prop tips and that alone get them so out of balance that they have to strip the paint completely off.
Remember the P-51 racer "Precious Metal"? it once had a spinner that was 24 carat gold plated. It had to be replaced as the Whittington brothers couldn't get the prop to balance and it had severe vibrations at high power settings.

[bipe215]

I balance my wood props with the last coat of flat black paint on the rear face. You can spray one tip heavy and watch that tip come up as the paint evaporates. Pretty critical even on little Lycomings.


Steve G

[retroaviation]

Propellor blades arc, flex, twist, and stretch in flight. I can't believe it would be possible to weld anything onto blades like that. The slightest imbalances in weight would be magnified on the blades. I have seen people put another coat of paint on their prop tips and that alone get them so out of balance that they have to strip the paint completely off.
Remember the P-51 racer "Precious Metal"? it once had a spinner that was 24 carat gold plated. It had to be replaced as the Whittington brothers couldn't get the prop to balance and it had severe vibrations at high power settings.

Every Aeroproducts prop out there has welded together blades, and I'm sure the Curtiss Electric stuff was the same way. We used to cut the cuff off of Skyraider blades and then weld the trailing edges back up to make "race props" for a certain couple of racers out there. Never really made that much of a difference, but it was a neat effort.

Gary

Gary

[Speedy]

Remember the P-51 racer "Precious Metal"? it once had a spinner that was 24 carat gold plated. It had to be replaced as the Whittington brothers couldn't get the prop to balance and it had severe vibrations at high power settings.

See, I never really bought the excuse for this. When Ralph Payne built that airplane up for Gary Levitz they decided to make that special spinner. It was not gold plated...it was actually 24K gold leaf that was rubbed on by hand. They found that the first time they ran it in the rain, it started coming off.

HOWEVER.

Gary raced that plane three times (Mojave 75, Reno 75, and Mojave 76) with that gold leaf spinner, and both Gary and Ralph did some serious testing of that plane in the spring of '76 at some serious power-settings for long periods of time...and not once did either one of them detect any kind of vibration that were out of the normal for a Merlin running at around 100 inches of Manifold Pressure.

They sold the plane to Don in July of '76 and ran it at Reno that fall at record speeds...with that gold spinner.

It wasn't until the following year, when the Brothers started doing their 'own stuff' to Precious Metal, that the story of the 'out of balance spinner' came to the surface.

Also remember, the 'race' prop they were using was a very, very thin profile 'experimental' Hamilton Standard blade, developed as part of the H-model test program. There were two sets made. One set was installed on the Beguine and destroyed in the crash at Cleveland in 1949. The other set was used by Joe DeBona on Thunderbird when he won the Bendix in 49. I've heard stories that the blades were so thin that during power run-ups on the ground, the blades would bend forward to the point that 'sponsor' Jimmy Stewart couldn't watch.

Ralph bought those blades and installed them on Precious Metal.

Other people have claimed that they were Northstar blades, or something of the sort similar to what Miss Candace/Jeannie ran in the 70's and 80's, but these were truly two-of-a-kind props...and the only one left of the pair.

That prop, of course, was destroyed when it was taxied into the back of a Datsun at Reno 77.

I tend to believe that, given my discussions with the primaries involved in building the plane, the vibrations may have had more to do with that prop and it's idiosyncracies that nobody else had 'felt' before than a layer of gold leaf on a spinner.

But hey...I wasn't there, wasn't flying it..and have no idea what kind of 'vibration' Don felt. All I know was when I asked Ralph about the spinner causing a vibration, his comment was "bullsh*t!"

Brad