Interesting weathering patterns on the Boomerang

[Kahunaminor]

Hello all,

During my research into the CA12 Boomerang, I was sent this photo:

which has been blown up from the original. I am interested in the weathering patterns on the inboard wing walkways. It would appear to be lines of rivets, the paint worn away from the bootmarks of the crew. The question is how to replicate it? It would appear to be rows of raised rivets but it appears from other photos the rivets in this area were flush?

I should have looked at this before I got to the stage I am in building. I have thought of the following methods:

HGW raised silver rivets

RB Rivet tool

Light grey water soluble pencil

all followed by wash and another coat of Dullcote. Or should I say "Next time?" I know what the answer will probably be for me as I cannot leave well enough alone but your thoughts are invited.

Regards,

Kent

[Wez]

Don't know how to replicate it but, the rivets would be more solid than the skin they attach to the structure, the skin would flex slightly under the continued boot pressure, the rivets and it's underlying structure would resist it.

This would lead to the skin away from the rivets stretching ever so slightly and the rivets would ceased to be perfectly flush however, they would either be slightly depressed or slightly proud in 1:1 scale, factor that down by your chosen scale and you can appreciate how minute the the effect would be.

Good luck with your project and thanks for posting an interesting photo.

Wez

Edited February 24, 2015 by Wez

[Kahunaminor]

Thanks for the informative answer Wez, I appreciate you taking the time.

Regards,

Kent

[Edgar]

Are you sure they're rivets? It wasn't normal for there to be so many, so close together, and in such a small area. To me, it looks more like a slightly ribbed, possibly non-slip surface (from which side did the pilot gain access to the cockpit?)

If the aircraft was like the P-51, in which pilots were not supposed to get access via the trailing edges, but climbed over the wings' leading edges, then walked down to the cockpit, it might explain the wear ahead of the cockpit on both sides.

[Kahunaminor]

From my discussions elsewhere, I think we can discount them being rivets. The pilot boarded from the port side. As I now understand it there is ribbing underneath and the constant wear and tear, weight if you like of the crew has caused the supported areas to wear and the unsupported to distress or sag. A similar theory to Wez without the rivets.

Regards,

Kent

[Wez]

From my discussions elsewhere, I think we can discount them being rivets. The pilot boarded from the port side. As I now understand it there is ribbing underneath and the constant wear and tear, weight if you like of the crew has caused the supported areas to wear and the unsupported to distress or sag. A similar theory to Wez without the rivets.

Regards,

Kent

Not being familiar with the construction of the Boomerang in that area, are those spot welds to hold the skin to the structure? They'd put up a bit more resistance than the skin which would sag around them.

If you look on the port wing aft and outboard but inboard to the fairing you can see the same effect there, it's faint but it's there - that area's too far outboard for a non-slip area.

Wez

[mhaselden]

One of my all-time favourite air-to-air pics showing Flt Lt AWB 'Alf' Clare in the cockpit of Boomer A46-126, 'BF-S', "Sinbad II" of 5 Sqn RAAF.

Alf Clare became a credited ace flying Buffalos with 453 Sqn over Malaya and Singapore and is one of the many unsung heroes from that conflict.

[Dave Fleming]

Have a look at the internal structure:

http://www.aussiemodeller.com.au/Images/History/Harvey/boomerang/Wings008%28VS%29.jpg

and how this wears even on a restored airframe

http://www.grubbyfingersshop.com/walkaround_galleries/CAC_CA-12_Boomerang_A46-30_RAAF_Museum_walkaround/content/CAC_CA-12_Boomerang_A46-30_RAAF_Museum_walkaround_027_large.html

[ben_m]

It looks like the right side (as we look at the photo) has no dot wear where the walkway paint/coating is, and the left side the walkway looks like it stops only after a little way towards the nose.

Leaving aside why the marks are there, you can replicate them with lines of dots of paint applied with a fine brush. Grey paint, or grey mixed with a little of the topside colour. There is a photo of a worn Typhoon that inspired me to try:

and the other side, more subtle:

[Kahunaminor]

Thanks all,

Dave that photo (as they say) speaks a thousand words! Many thanks!

Regards,

Kent

[Vanroon]

Having utilised the centre-section of the Wirraway, on which contemporary photos show similar wear. My father tells me that 'blinds' of timber with canvas strips were laid on the wings during servicing to alleviate 'oil-canning' of the wing root area. The pressure of the timber strips would seem to be the cause of the paint damage in that photo.

Also of note is the oil staining of fading paintwork.

What a great photo of the little fighter. I have another from the same session on the wall at home.

edit, a photo of Dad after his 2 Beauforts had left for the day.

http://pic20.picturetrail.com/VOL1620/1548565/22690966/377459270.jpg

G

[Kahunaminor]

Having utilised the centre-section of the Wirraway, on which contemporary photos show similar wear. My father tells me that 'blinds' of timber with canvas strips were laid on the wings during servicing to alleviate 'oil-canning' of the wing root area. The pressure of the timber strips would seem to be the cause of the paint damage in that photo.

Also of note is the oil staining of fading paintwork.

What a great photo of the little fighter. I have another from the same session on the wall at home.

edit, a photo of Dad after his 2 Beauforts had left for the day.

http://pic20.picturetrail.com/VOL1620/1548565/22690966/377459270.jpg

G

So the damage would primarily appear to be abrasive in nature. No rivets or distressed skin?

Now that is an interesting piece of information. Thanks for that.

Regards,

Kent

[Magpie22]

Thanks all,

Dave that photo (as they say) speaks a thousand words! Many thanks!

Regards,

Kent

K

Edited April 26, 2015 by Magpie22

[gingerbob]

A flat aluminium sheet was fitted over the outside of the corrugated skin to maintain a smooth airfoil shape. It was not structurally load bearing.

I believe that what you are seeing in your photo is wear above the top of each corrugation.

~~~~~~~~

This shot is of the CA-14, so structure is not exactly the same, but it shows the type of wear pattern, Note how the paint has been worn down over the top of the corrugations and that there are no rivets in that area.

Wouldn't those (more or less) evenly spaced circles (some more evident from abraded paint than others) be rivets?

I'm sure you know more about Boomerang structure than I do, but I'd be surprised if the skin wasn't riveted to the underlying corrugated sheet. And if so, then the outer skin becomes structural, too, much as both the corrugated center and the smooth outer layers combine to make cardboard "stiff". (I don't see that your excerpt specifically says that the outer skin is NOT fastened/structural.)

I suggest that we're all approximately right- the rivets themselves are "solid" (and the act of riveting may have caused a very slight "proudness"), they are over (or through) underlying structure, thus stiffer than the surrounding skin that is NOT directly against other structure, and the firmer the particular spot, the more the paint would be abraded.

Some excellent illustrations in this thread!

bob

[Nick Millman]

Was there a primer coat on the Boomerang? In that last photo the wing root seems to show a three-tone of camo, something under the camo and bare metal - or was the brown applied overall first. That will have a bearing on weathering a model.

[Magpie22]

Was there a primer coat on the Boomerang? In that last photo the wing root seems to show a three-tone of camo, something under the camo and bare metal - or was the brown applied overall first. That will have a bearing on weathering a model.

Yes.

Edited April 26, 2015 by Magpie22

[Magpie22]

Wouldn't those (more or less) evenly spaced circles (some more evident from abraded paint than others) be rivets?

I'm sure you know more about Boomerang structure than I do, but I'd be surprised if the skin wasn't riveted to the underlying corrugated sheet. And if so, then the outer skin becomes structural, too, much as both the corrugated center and the smooth outer layers combine to make cardboard "stiff". (I don't see that your excerpt specifically says that the outer skin is NOT fastened/structural.)

I suggest that we're all approximately right- the rivets themselves are "solid" (and the act of riveting may have caused a very slight "proudness"), they are over (or through) underlying structure, thus stiffer than the surrounding skin that is NOT directly against other structure, and the firmer the particular spot, the more the paint would be abraded.

Some excellent illustrations in this thread!

bob

B

Edited April 26, 2015 by Magpie22

[Nick Millman]

Yes.

The attached Finishing Department Bulletin, dated November 1941, refers to the Wirraway with Aluminium undersides. It also applied to the Boomer, but with undersides amended to Sky Blue, as with later Wirras also.

Section 1 covers the primer coat.

Section 3 covers application of camouflage colours. They were free sprayed, two coats of each colour. Each colour was applied in its own specified area: the brown was not applied overall first.

Magpie22

Thanks for the confirmation!

Nick

[Kahunaminor]

Wow Gents,

Thanks so much for the information. It has cerainly been a learning curve! Magpie 22 those photos are great and valuable assistance. I appreciate your assistance and references!

I note there is a specific warning about avoiding the rivets on page 2 of the painting instructions!

Regards,

Kent

[A30_737_AEW&C]

Magpie22,

Thanks for sharing the information you have about the Boomerang's wing construction. Very enlightening, but also not surprising when you understand the engineering design approaches and fabrication methods of that time.

I 'chewed the cud' with Kent on this matter via another avenue in parallel and wasn't too far off the mark.

I 'rescued' some material from CAC/HDHV before what remained in the 'archives' was disposed of. 'Criminally negligent' was that disposal action IMHO.

gingerbob,

Your insight is also appreciated. Structures engineering is my 'forte' as an engineer. Good work !

mhaselden,

I appreciate your info regarding Alf Clare and 453 SQN Buffalos. I am planning a 453 SQN Buffalo build and this information might give me a better focus on the specific aircraft I may elect to build.

Kent,

A final acknowledgement to you for 'bringing' this all together !