ply finishing

sheppo · 18 March 2009, 05:43 PM

A new question I think for those playing with the real thing.

Last night I did some work on the inside of the tail skins, just a coat of warmed epoxy directly to the skin where it wont be seen.
Obviously the coat is a little grainy and needs a sand before I put a second on but my question is more about altering the tones of my finishes.

The hoop pine is not as "warm" in colour as the birch and I want to replicate the exterior of the original Albatros.

I was planning to use everdure for sealing the interior before an overcoat of west system epoxy. Has anyone played with this combo on ply before and how does it change with exposure to light over time should i decide to use this method on the exterior?

I did my ply floor (shed) in polyeurethane and that has taken a nice warm straw colour after the last year, without any addition of additional colourisers etc

What are the thoughts and experiences from the forumites regards this subject?

Epoxy only.
Everdure with epoxy coat over the top
everdure with polyeurethane
etc

Chris

Der Grüne Flieger · 18 March 2009, 06:28 PM

Chris,

I have no firsthand experience with your request for help. It is a fairly pointed question and it might be tough to find the answer here. Luckly, I may have a bit of help for you. Sawmill Creek is a forum that is specific to woodworkers. They have given me a great deal of help and it seems there are a great deal of "old hands" on that forum who have done almost everything related to wood.

The link is Sawmill Creek - Powered by vBulletin

Regards,
P

'14-'18aviationcollector · 18 March 2009, 06:52 PM

Hi Chris,

Don't forget that when the plywood was new and newly varnished, it would have been, in my opinion at least, much lighter and whiter than you might think. I know that our modern varnishes would be a lot clearer than the varnishes they would have had back then, but I still tend to think that the combination of (presumably) new plywood with fresh varnish would have been quite light and a whitish colour. Even clear doped linen is much whiter when it is new. The familiar yellowish colour found on CDL and varnished plywood is due more to aging than anything else. I remember reading the NASM Albatros book, and they said with hindsight they would have added some tint to the varnish, but they more I think about it, they are probably very close to the correct colour, for a new airframe at least. Of course it is impossible to know for sure, and it really depends on whether you are trying to achieve a new or slightly weathered look. I have always been of the opinion that re producing a new colour scheme is the most sensible option, since if you start with weathered colours, they will weather naturally when you start flying, and when the aeroplane starts to age.

I have a camera phone now, which I was given recently, so I will see if I can get some decent photos.

Cheers mate,

David.

sheppo · 18 March 2009, 07:02 PM

There are a few images I have of the areas the AWM used the laser on and the ply was not really so dissimilar in colour to the hoop. Perhaps a little "greyer" but not much. I will pick up some spar varnish and have a play with it over the everdure. I think I may take the resulting test bits to canberra and do some comparisons.

Chris

sheppo · 18 March 2009, 07:55 PM

Heres a couple of comparison images from the original and my fuselage. Ignoring the image conditions, lighting etc the new plywood doesnt look that dissimilar to me...

Chris

'14-'18aviationcollector · 18 March 2009, 11:46 PM

Thanks for the photos Chris. It's easy to forget that a lot of what we have for the purposes of research, such as 5390/'17 has been subjected to years of weathering and dirtying. Where the paint has been stripped, your photo shows the relatively newish appearance of the plywood where it has been covered by paint most of the time, in contrast with the weathered and dirtied varnishished plywood right next to it. As you alluded to, I don't think that the hoop pine is too dissimilar to the birch either. I know what birch looks like, and it is not exactly the same as hoop pine of course, but it certainly is not too dissimilar.

Cheers mate,

David.

Flug Werke · 19 March 2009, 02:14 AM

Chris, the top shot you have with the silver headed nail shows a section where the varnish has been laser stripped (as has any corrosion from the nailhead).

This is raw timber, not the straw colour you'd get from varnish over the timber.

In my opinion, your best guess is a finish as it currently appears on the exterior of 5390 (don't take your datum from up front where there is some discolouration due to oil staining, look at how it appears on the sides of the fuselage further back)

sheppo · 19 March 2009, 02:53 PM

This is raw timber, not the straw colour you'd get from varnish over the timber.

Yep, it isnt far off the mark to my mind. Ive done some hunting for birch ply images and the colours vary a good deal, the light butter colour of the Hoop isnt a bad match for many including the AWM

In my opinion, your best guess is a finish as it currently appears on the exterior of 5390 (don't take your datum from up front where there is some discolouration due to oil staining, look at how it appears on the sides of the fuselage further back)

Im pretty set on everdure 3 coats (thinned less and less as I go) with about 7-8 coats of spar varnish for my exterior finish. I'll begin a sample panel tonight so I can assess how it performs for colour and indeed for exterior use.

Chris