I am in need of some technical information.....

[RCoulter52]

I have noticed that the propeller blades on the F7F fire bombers are squared off while the original and restored 'Cats have rounded tips.

Was this just a newer model of propeller and, if so, why did the contractors go with the square tipped blade model? As noted, the restorations all seem to have gone back to the original style blades.

Thanks to all for any and all information.

Randie Coulter

[sdennison]

Trust me, I don't know squat but it may be that they are taking an existing prop blade that is longer than required and cutting it down. I have seen this with other applications I once messed with. It was cheaper than to tool for the original version and quite acceptable, performance wise.

Now I'll wait to be flogged for my misinformation.

Last edited by sdennison on Tue Mar 31, 2009 10:03 pm, edited 2 times in total.

[RCoulter52]

Someone else had suggested that that might be the case.

I know that they changed the propellers out on the F-15 Reporter fire bomber because of performance issues and I was wondering if that might not have been the case with the F7F's as well.

[steve dickey]

Now I could be totally wrong but there is some truth to the matter.
Cut down props are like cutting the wings down on a racer, gives a little more performance.
Why none now do since most survivers were fire bombers, don't know?
I would say that owners din't like em and were able to find original blades?
I too would like to know a little about this.

[RCoulter52]

Well, at least I got the pot stirred up a little on this. Gonna sit back and see what happens.

[John Dupre]

I have noticed that the propeller blades on the F7F fire bombers are squared off while the original and restored 'Cats have rounded tips.

Was this just a newer model of propeller and, if so, why did the contractors go with the square tipped blade model? As noted, the restorations all seem to have gone back to the original style blades.

Thanks to all for any and all information.

Randie Coulter

I don't know for sure but would think that later versions of the props may have had squared tips. I have a photograph of one of the last C-123s in service and it had one propeller with rounded tips and one with square tips. There was a lot of research done on propellers during and after the war and one of the results is that pre war most props had rounded tips and post war most have squared tips. My guess is that rounded tips did not add to efficiency and squared tips either were more efficient or did not detract and were easier to manufacture.

[RCoulter52]

Alright. We're getting some interesting takes on this. Let's keep it going until we get a definitive answer. All, so far, seem logical.

[b29flteng]

C-130 props have square tips yet the P-3 has round tips with the same engine. I asked a Hamilton Standard prop tech rep and he said the difference is the square tips provide better heavy lift while the round tips are better for cruising.

[hahnej]

The B-26K-model Invader had different R2800s and square-tip props than the earlier models, wonder if the fire bomber Tcats used that prop and maybe engine combination...? From the same era....

[RCoulter52]

C-130 props have square tips yet the P-3 has round tips with the same engine. I asked a Hamilton Standard prop tech rep and he said the difference is the square tips provide better heavy lift while the round tips are better for cruising.

Now we're getting somewhere.

Thank all of you guys for the input. But, don't stop now! It's getting fun and educational!!

[RCoulter52]

The B-26K-model Invader had different R2800s and square-tip props than the earlier models, wonder if the fire bomber Tcats used that prop and maybe engine combination...? From the same era....

This, too, is a possibility as they were from the same time frame. Something else to ponder.

[RCoulter52]

Just wanna keep this on the front page in case somebody else has a different explanation.

[The Inspector]

I was told by an old timey P-3/C-130 F.E. that square tips=power props and round=speed props

[RCoulter52]

One more bump and then I'll let her die.

I think we may have the answer, though. The little 'Cats were lifting quite a bit more than when they were at their 'fighting weight' so the the 'square tips=power props and round=speed props' makes sense to me.

[Old SAR pilot]

Ref the round tips on the P-3. Interesting to note that the L-188 Super Electra had square tips. One would think an airline would opt for speed props vs power props. And it looks like Aero Union (IIRC) is using speed props on its firefighting P-3s rather than power props.