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CDL wings and ribs


Unkempt

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Mmm. Wings and ribs.

Anyway, I'm making a WW1 plane with clear doped wings for the first time in ages and I've been looking around at techniques. It looks like most modellers paint the linen colour then mask the ribs and shade around them, leaving lighter coloured ribs. It looks good but when I take a look at real pics - for example, Google image searching 'Bleriot' - the majority look like the ribs are darker than the rest of the wing. Am I missing something? Is it all just a trick of the light?

Edited by Unkempt
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It's a very good question.

Looking at photos of various aircraft of that era, I wonder if the darker lines are a result of the wood ribs showing, while white lines are more prominent when rib tapes are present, such as this camel?

Sopwith-Camel-moved-into-exhibition-spac

regards,

Jack

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Ah, that looks a lot more like the models I've been looking at. I think some of it is whether the top is clear or not, so there's more light shining through which would give more shadow - I assume that Camel has PC10 on the upper surface. You can still just see the roundel though. So maybe as the CDL is semi-transparent,

- clear upper surface, you can see the sunlight through so ribs look darker, but

- dark upper surface, you can see the darkness through the lower surface so the ribs look lighter?

One more question, did rib tapes get replaced at all? Could they be newer and cleaner than the rest of the surface?

Off to look at more photos.

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It could be partly that, translucent effect when CDL is coloured, or top surfaces are painted. The other factor are the rib tapes, which I believe are strips cut from the same fabric. Doped into place, they basically double up the thickness of the linen(?), thus producing a more opaque covering over the ribs, so the area appears lighter because the dark wood underneath isn't showing through. No idea if these had to be replaced periodically.

regards,

Jack

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It depends on a number of variables, since practices varied, and you should refer to your reference photos. Also, bear in mind, most reference photos show the underside of the wing, whereas your model will be seen from above, and obviously, lighting will be different above something vs. underneath it.

On wings that are fully CDL and see-through, the light shines through the wings,so from underneath, the structures will appear darker (in shadow, since light doesn't pass through wood). Wing ribs and other items that actually attach to the fabric skin will be relatively sharp; spars and other items that sit away from the fabric will look softer.

https://upload.wikimedia.org/wikipedia/en/f/fd/Bleriot_monoplane.jpg

On the top side, it's reversed. You're not going to get shadows from the skeleton, because you're above it. The fabric is translucent; since the rib tapes add more layers of fabric, they'll be more opaque and have a 'stronger' colour. Not necessarily darker, just more saturated. On some aircraft, you'll get a very subtle shadow between the ribs from the depth of the wing cavity.

In the case of the Bleriot, it's fabric was *very* translucent, so you'll see the dark brown of the ribs through the fabric, and the ribs will be *slightly* darker than the rest of the upper surfaces.

https://upload.wikimedia.org/wikipedia/commons/b/be/Bl%C3%A9riot_XI_Thulin_A_Mikael_Carlson_OTT_2013_04.jpg

In the case of, say, the Bristol Scout, the ribs are paler, and the wing cavities are slightly(!) darker. This is a great photo that lets you compare upper and lower wing shading directly; notice notice that the shadows under the upper wing are a lot darker than the cavities on top of the lower wing:

https://bristolscout.files.wordpress.com/2014/10/2014-10-23-bristol-scout-bbc-midlands-joanna-writtle.jpg

The Camel photo that Jack posted is quite different. Because the wing tops are painted (you can see the demarcation line in the full size photo), the light isn't behaving the same way. Since the wing tops are painted, and you're seeing them through the wing bottoms, the dark paint looks like a shadow. (notice the roundel showing through the wing as well) You're also getting the layered rib tape effect, so they appear more 'saturated' than the surrounding fabric. Net result looks like highlighted ribs and shadowy fabric.

The main lesson, though, is that you have to consider how the original wings were finished and tailor your shadowing effects to the subject at hand.

Edited by ICMF
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Thanks guys. Well, this is getting complicated. I'm making the Special Hobby Morane-Saulnier N and photos of the original are rare and not very helpful. It's CDL on both surfaces, so from the above I'm now thinking darker ribs for the underside and lighter for the top.

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According to;

Bruce, J.M., 1996, Morane-Saulnier Types N,I,V, Windsock Datafile No. 58, Albatros Productions Ltd. Berkhampsted, Great Britain, ISBN. 0 948414 76 6, PP. 36.

Nearly all these airframes left the factory with the fabric areas of the airframe finished in a non-pigmented dope followed by a clear varnish that gave a light brown finish around Methuen 3B5-4B5.

One point to check, if you have a photograph of the airframe that you are building, is that some, (not all), had black painted cane batons tacked over the ribs.

Looking at the images that are available to me.

Upper wing; the wing ribs look saturated and much lighter than the surrounding inter-rib areas. This is especially noticeable where the black cane batons have been tacked on. The inter-rib area is a paler much less saturated tone that the rib. The two spars can occasionally just be made out as an indistinct darker blur.

Lower wing. Ribs, as above. Inter-rib area, as above but darker than above. Spars, as above but darker and slightly more defined.

In general there is more contrast in tone, as expected, underneath and less on top.

HTH!

Christian, exiled to africa

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Thanks, guys. It's the French boxing and I'm going for the black-nosed MS-391. I'm pretty sure it doesn't have the black batons but really I'm going by their painting instructions there.

Christian, thanks for all that - I'm pretty sure I now have information that exceeds my painting skill level :)

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No problem! Always happy to share the knowledge and to help.

Looking through the tome mentioned above there is a picture of MS 391, on page 12, It is taken from the four O'clock position and appears not to show the batons, therefore they were unpainted. Also the upper edge of the fin has a narrow dark, (most likely), black border and around the edge of the elevators.

Christian, exiled to africa

Edited by wyverns4
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Ooops, my mistake! :blush:

Thanks Vince for picking me up on that! Post #10 has been amended. ;)

Cheers,

Christian

Edited by wyverns4
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It seems to me to depend on the angle of the sunlight. When the sun is behind the wing the ribs show dark as shadows s they block the

Sunlight. When the sun is shining from over the viewers shoulder, so to speak, the tighter fabric over the ribs reflect more light back at the viewer so they appear lighter.

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