TonyOD's Spitfire questions: wear to wooden prop blades?

[TonyOD]

So I’ve just embarked on a long-term project to build a hangarload of Spitfires and Seafires in 1/48. Inevitably questions will arise that referring to my small reference library (Price, Morgan & Shacklady etc.) and Googling on the interweb won’t be able to answer. I’m aware of the “all the Spitfire questions” thread but so I have everything in one place I’m going to indulge myself with a thread for my occasional questions. 

First up: two of my current builds had (I believe) wooden propeller blades: a Seafire IIc with a four-blade prop and a Spitfire IIa with a three-blade Rotol. Both airframes were in fairly intensive combat situations so a bit of weathering will be appropriate, but obviously prop leading-edge chipping with a metallic paint won’t. Anyone got any suggestions as to what a battle-hardened wooden prop would have looked like? I have pics of both airframes, the Seafire’s prop appears to have a fair amount of wear on the leading edges of the prop blades, but I don’t suppose it can be metallic; the pic of the Spit IIa shows the prop side-on so it’s less clear, but (possibility of a prop change apart) the aircraft was 16 months old at the time I’m depicting it so some wear and tear was likely. Would there have been visible primer? Bare wood? Any thoughts?
 

Thanks

Tony

Edited February 23, 2023 by TonyOD

[Kari Lumppio]

Hi!

My experience is from 180 hp glider tow plane wood propellers.

 

I would expect every ww2 wooden propeller have a metal sheathing on blade leading edge. At least the Finnish ones by VL did have. Brass or steel.

 

Sand and other debris do hit on the blade thrust side and leading edge. Thrust side is the back side which is almost straigt with the common propeller airfoils Clark Y and RAF 6.

 

Thrust side was where I did small repairs with epoxy and paint. Seldom (never?) there was any noticeable on the front side of blades.

 

Don't know if this is of any help.

 

Cheers,

Kari

 

 

[Work In Progress]

Everything Kari says is right.

Some pics here of leading-edge sheathing showing the way the metal shows through due to erosion.

However: you might not want to overdo it. While naval aircraft do generally have a fairly hard time, especially if stored on deck, the usual sources of prop erosion aren't really present in the same way as for land-based aircraft. You aren't taxiing around through the dust, sand and grit that airfields in various geographies tend to feature, and you don't have long take-off and landing runs. 

One of the biggest factors taking paint off the leading edges of prop blades is flight through rain, and I doubt that was so much of a factor for point defence of carrier group as it was for long range intruder missions in Europe or other types and locations of operation. Nevertheless, if your Seafire photo shows significant exposure of the metal sheathing, I'll bet you that's what caused it. Combat itself is not an issue, except for the more extreme erosion caused by enemy fire!

Edited February 23, 2023 by Work In Progress

[spitfire]

More info here.

 

 

Cheers

 

Dennis

[ilj]

I tried to simulate this with a few swipes of a gold metallic Prismacolour pencil along the leading edges of the prop blades

 

https://www.amazon.com/Prismacolor-Premier-Colored-Pencil-Metallic/dp/B0033PTKL4

 

[TonyOD]

Thanks, @Kari Lumppio, @Work In Progress, @spitfire It makes perfect sense that a wooden propeller blade would have a metal sheath to the leading edge. I did some further digging and the metal used for a Rotol blade of that period was most likely brass, I guess at least in part for its malleability in shaping round the edge.

 

However as regards my particular airframes:

 

Rotol* props on Mk IIa Spitfires were initially magnesium alloy-bladed, but apparently they were changed to wooden blades at some point during the production of the marque. IIa’s were built at the Castle Bromwich factory between June 1940 and April 1941. My IIa, P7308, was delivered to 24 Maintenance Unit at the end of July 1940, which makes it a pretty early example. I’m therefore going to go with MA and wear accordingly.

 

I think my Seafire IIc, on the other hand, had a wooden propeller. I seem to remember reading somewhere that trials were carried out with wooden and metal propellers, and given the Seafire’s propensity for nosing forward and “pecking” the carrier deck, wood was considered safer for deck crew from the point of view of blades or fragment of blades flying around the deck. I’m thinking brass for the leading edge sheath. In the one good photo of the prop that I have from the front the blade leading edges, or at least the one nearest the camera, look very worn indeed.

 

2 hours ago, ilj said:

I tried to simulate this with a few swipes of a gold metallic Prismacolour pencil along the leading edges of the prop blades

 

I like that effect a lot. Maybe a few more pennies finding their way into the Bezos bank account from my direction.

 

* I just learned that Rotol was founded as a joint venture between engine manufacturers Rolls Royce and Bristol. Every day's a school day!

 

 

 

Edited February 23, 2023 by TonyOD

[wmcgill]

The only photo I have seen of Spitfire Mk.IIa P7308 was taken in August 1941, at which time it was at 71 Squadron and had a Rotol RX5/3 Jablo wooden bladed propeller. 

 

Edited February 23, 2023 by wmcgill
added photo

[TonyOD]

That’s the same pic I’ve seen as it happens @wmcgill. Mind if I ask how you know it’s a wooden prop?

cheers

[wmcgill]

47 minutes ago, TonyOD said:

That’s the same pic I’ve seen as it happens @wmcgill. Mind if I ask how you know it’s a wooden prop?

cheers

The shapes of the RX5/3 spinner and Jablo propeller blades are different from the RX5/1's spinner and magnesium propeller blades.

[Troy Smith]

3 hours ago, TonyOD said:

I did some further digging and the metal used for a Rotol blade of that period was most likely brass,

 

Yes, and you are likely overthinking the weathering, the image below is a desert Spitfire.   I'd suggest some grey chalk pastels in direction of airflow, more at tip ONLY on rear. 

 

More brass

Spitfire XIVE by Etienne du Plessis, on Flickr

 

 

you need to look at these very closely to see the brass

 

Spitfire maintenance by Etienne du Plessis, on Flickr

 

Merlin service, 1944 by Etienne du Plessis, on Flickr

 

Spitfire Mk.IXC      1945 by Etienne du Plessis, on Flickr

 

3 hours ago, TonyOD said:

Rotol* props on Mk IIa Spitfires were initially magnesium alloy-bladed, but apparently they were changed to wooden blades at some point during the production of the marque. IIa’s were built at the Castle Bromwich factory between June 1940 and April 1941. My IIa, P7308, was delivered to 24 Maintenance Unit at the end of July 1940, which makes it a pretty early example. I’m therefore going to go with MA and wear accordingly.

Source?  

AFAIK only the very very few 54 Sq Spitfires in April 1940 that had Rotol units had metal blades,

example 

http://www.spitfireperformance.com/klo.jpg

 

There are more images of a crashed at Dunkirk metal prop Spitfire here

https://www.britmodeller.com/forums/index.php?/topic/234981609-dunkirk-spitfires/

 

in particular

https://www.britmodeller.com/forums/index.php?/topic/234981609-dunkirk-spitfires/page/2/#elControls_1991649_menu

 

NOTE if browsing on a computer, if you right clikc and 'open image in a new tab'  you can see photobucked images without their logo, though they

only now save as WEBP file. 

OK this will display

Rotol prop, metal blades

54 Squadron 01 by Сергей Кривицкий, on Flickr

 

 

after that they all had the compressed wood. 

 this is a very early Spitfire II of 19 Sq

19 Squadron 45 by Сергей Кривицкий, on Flickr

 

 

 

I also doubt the early Rotol wood blades has metal sheething, 

AFAIK these are the same props and blades on BoB Hurricanes, and shattered blades do not show any bit's of metal

eg

 

here's a IIC in 1945

 

 

 

 

The chap for prop blades is @V Line   who maybe able too correct any errors above.

 

HTH

 

[Julien]

9 hours ago, TonyOD said:

So I’ve just embarked on a long-term project to build a hangarload of Spitfires and Seafires in 1/48. Inevitably questions will arise that referring to my small reference library (Price, Morgan & Shacklady etc.) and Googling on the interweb won’t be able to answer. I’m aware of the “all the Spitfire questions” thread but so I have everything in one place I’m going to indulge myself with a thread for my occasional questions. 
 

Thanks

Tony

Is there a reason you have started a new thread for this when there is already an "All the Spitfire questions thread?

 

 

[TonyOD]

3 hours ago, wmcgill said:

The shapes of the RX5/3 spinner and Jablo propeller blades are different from the RX5/1's spinner and magnesium propeller blades.

 

There are two different shapes of Rotol in the Eduard kit, @Troy Smith has already alluded to a difference that I really can't see, maybe I need to look a bit more closely!

 

2 hours ago, Troy Smith said:

Yes, and you are likely overthinking the weathering,

 

I overthink everything - it's in my nature! 😁 Thanks for the further info, thorough as ever.

 

2 hours ago, Troy Smith said:

Source?  

 

Read it on a thread elsewhere in BM I think. I was on a different computer so don't have it to hand in the memory.

 

1 hour ago, Julien said:

Is there a reason you have started a new thread for this when there is already an "All the Spitfire questions thread?

 

As I said I specialise in Spitfires, I just fancied a thread where I'd have all my queries in one place at the end of one browser shortcut. I'm aware of the "all the Spitfire questions" thread, I've asked questions there in the past, but also plenty outside the thread, as have many others. Not sure I see any harm.

Edited February 23, 2023 by TonyOD

[Zephyr91]

6 hours ago, TonyOD said:

.......somewhere that trials were carried out with wooden and metal propellers, and given the Seafire’s propensity for nosing forward and “pecking” the carrier deck, wood was considered safer for deck crew from the point of view of blades or fragment of blades flying around the deck.

Couple of thoughts for background info (but doesn't help how it looks for a model I'm afraid)

1. Any pictures I've seen with bent metal propellers seem to have the blades intact but horribly bent.  Wooden blades seem to have tended to shear off after ground strike

2. The wooden blades shearing off would probably be better from an engine health point of view because they wouldn't stop the engine.  Whereas the metal blades would tend to stop the engine almost dead, with attendant shock loading and potential internal damage to the engine - worst case needing new engine rather than just a new set of blades.   I don't know that for certain but would seem logical. I remember that when the PRXIX was restored at Warton in the late 1980's/early1990's(?) they had just such an incident of "pecking" whilst taxiing.  There was much relief that the prop blades had been wooden and not metal for that reason.

 

cheers

 

Rob

 

[TonyOD]

All that would seem to make absolute sense, @Zephyr91. 

 

[Zephyr91]

That's an amazing photo.  Still from a video?

 

Many moons ago when gainfully employed, I spent some time calculating and simulating loads on aircraft landing gear.  A photo like that would be very useful as part of the evidence for verification of the numerical modelling (providing other info was available too).  As well as the flight of the broken blade, I  notice that at the instant of the photo there is very little weight on the wheels (aircraft in in mid-bounce?) and the elevator is clearly in a position that would impart a nose-down attitude.  This possibly due to the inertial movement of the pilot during the unconventional "arresting" with his weight shoving the stick forward, even if he wasn't intending to.  I know he'd be strapped in but his arms can move.   The port side seems to have got the canon under the wire indicating either the wire was not horizontal or the aircraft was one wing down at point of engagement.    Again, not very useful from a modelling point of view.  I mean, what colours was it all .......?         Apologies for rambling.

 

Rob

[TonyOD]

Just now, Zephyr91 said:

That's an amazing photo.  Still from a video?

 

Possibly from a film originally, just a still I found on t'internet.

 

1 minute ago, Zephyr91 said:

Apologies for rambling.

 

Not at all. Plenty to think about there. This pic captures a fraction of a fraction of a secod, I imagine!

[wmcgill]

58 minutes ago, TonyOD said:

 

There are two different shapes of Rotol in the Eduard kit, @Troy Smith has already alluded to a difference that I really can't see, maybe I need to look a bit more closely!

 

I think if you can't tell the difference between the RX5/1 & RX5/3 it's because they look so similar almost no one can.

 

If you/no one can tell the difference then the only way this really affects you is whether you treat/paint/weather your propeller blades as metal or wood. 

[825]

16 minutes ago, Zephyr91 said:

That's an amazing photo.  Still from a video?

 

Many moons ago when gainfully employed, I spent some time calculating and simulating loads on aircraft landing gear.  A photo like that would be very useful as part of the evidence for verification of the numerical modelling (providing other info was available too).  As well as the flight of the broken blade, I  notice that at the instant of the photo there is very little weight on the wheels (aircraft in in mid-bounce?) and the elevator is clearly in a position that would impart a nose-down attitude.  This possibly due to the inertial movement of the pilot during the unconventional "arresting" with his weight shoving the stick forward, even if he wasn't intending to.  I know he'd be strapped in but his arms can move.   The port side seems to have got the canon under the wire indicating either the wire was not horizontal or the aircraft was one wing down at point of engagement.    Again, not very useful from a modelling point of view.  I mean, what colours was it all .......?         Apologies for rambling.

 

Rob

Are the wires part of the arresting gear or the barriers to stop aircraft that have missed the wires. I think it might be the latter as there is another strung across in front of the aircraft as well as the fact the set the aircraft is already engaged with are high and has at least two strands. What do others think?

[Zephyr91]

I agree.

[malpaso]

The laminated timber blades had a metal (brass) leading edge and were then covered with a fabric sheath which would then be doped/painted.

BBMF etc new prop blades of this type come from a German company!  Here's the company.  Their modern blades are sheathed in modern materials, not sure if that's the case for the vintage ones or if they replicate the older method.

Hoffmann note another benefit of timber blades being that the construction absorbs vibration etc, stressing the engine less than metal types in use.

[Kari Lumppio]

Hi!

 

Separated from my sources few hundred kilometres, but from memory it was German method  used already in 1930's! Schwartz-method was in use for the British and American WW2 era wooden propellers.

 

NACA and/or Forest Products Laboratory (FPL) in USA did quite a lot of good research on Compeg-wood. Which is the material of the center "spar" of that type of wooden blade. I've studied them because of my work. BTW Soviet delta-wood is the exact same thing. Somehow they think it is something unique (Russian nyeanalog syndrome).

 

Cheers,

Kari

[Graham Boak]

Resin impregnated compressed wood may well have been a German invention.  Schwarz propellers were among those considered for the Spitfire prewar.  Presumably there was a British licence-holder.

 

I think the Russian widespread use of birch shpon was perhaps unique in being used for aircraft structures and covering, certainly on the wide scale seen in the Soviet Union in the early 40s.  It would be interesting to know how the Japanese intended using wood on their emergency types (e.g Ki.106).  My understanding is that the Mosquito used laminations of standard woods.

[Kari Lumppio]

Hi!

 

Lockheed manufactured wooden monocoque fuselages already in late  1920's

https://en.wikipedia.org/wiki/Lockheed_Vega 

 

Shpon means veneer. It is not at all the same as delta wood. Plywood is lamination of veneers.

 

I am pretty sure Lockheed manufactured fuselages and certainly at least experimented making double curvature fairings from cross laminated veneers in 1930's. The linked wiki article writes only aboit plywood sheets. Not sure it is correct.

 

Quite a lot of of technologies were transferred from USA to Soviet Union in late 1920's to early 1930's (Ford et al).

 

Cheers, 

Kari

[TonyOD]

“Shpon” is my new favourite word 😁

[Work In Progress]

13 hours ago, 825 said:

Are the wires part of the arresting gear or the barriers to stop aircraft that have missed the wires. I think it might be the latter as there is another strung across in front of the aircraft as well as the fact the set the aircraft is already engaged with are high and has at least two strands. What do others think?

Yes, that is in the barrier, having failed to engage any of the arrestor wires