Bonding trim on stained or painted wood surfaces

[JohnB40]

Greetings to all,

A question concerning my Confederacy build...What effect will a stained or painted hull have on the bonding strength of adding wood trim and brass PE parts? I have finally milled some pear planks which I would like to use in their natural colour for the wales,these would have to bond to the basswood stained hull. Searching on the forum and on line I get conflicting views. I would think using a water based stain would give a better adhesion surface than oil based,but I prefer oil based as water based is far more opaque and tends to lift the grain. Any advise on types of stains,adhesive and techniques would be greatly appreciated.

John

[Jaager]

PVA bonds by long chains going into pores and irregularities on the two mating wood surfaces.  If there are no pores, there is no attachment places for the chains.  A purpose for a sealer or filler is to block the pores and provide a smooth surface.   Since two part epoxy is used to bond metal to metal or metal to wood,  its method of bonding is different.  The sealed surface should bond - to a point.  The strength then depends on the attachment of the sealer to the wood.  Epoxy tends to be kind of messy when compared to PVA for wood to wood.  CA is not a tool that I use, but again, if used on a sealed surface, the strength devolves to that of the sealer to the wood.  If you have ever seen paint or clear finish flaking from a surface, then you know this bond is not reliable on a planet with an oxygen atmosphere and water vapor also present.    A tedious resolution is to plan ahead and use a masking agent to protect the bonding surface from any sealer or paint.  After the fact, a solution would be to protect the sealed or painted surface with a masking agent and abrade the sealer from the bonding surface using a file or sanding stick or sand paper or scraper.

Edited February 12, 2020 by Jaager

[reklein]

I will say that the area that you need to bond toneeds to be roughed up. Perhaps one of those diamond rifflers that you can get from Micr-Mark will do the job. They can just do a narrow area if that's all you need. Might wanna mask off the area to be glued to. Just use titebond or similar PVA.

[JohnB40]

Thank you Jaager and Bill for your replies and advise.

After posting, I tried bonding with PVA the pear trim to basswood scraps with acrylic painted and stained finish,as well as oil based stain. All finishes had been cured for months. I left all clamped for 24 hours .The oil based stain had the worst adhesion,I could pick it apart with light pressure from my finger nail. The acrylic paint and stain samples adhered a bit better,but the bond was still not that strong. The answer is as you suggested. I will have to cut blue masking tape to 1/16" wide strips and mask the hull where the trim is needed to be placed. I will deal with the photo etched parts when I get to that point.

The M.S. Confederacy supplied wood is all basswood,which really needs stain and paint. I have never run into this before as all my previous kits were supplied with much nicer wood that just needed a finish coat of poly when all assembly was finished.

John

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Edited February 14, 2020 by JohnB40

[Bob Cleek]

There is a sound reason why the commissioned model construction standards for most all major museums in the world require all parts on a model to be mechanically fastened and not just glued in place. Mechanical fastenings are far stronger than glue alone. Tiny wooden pegs joining the pieces and ("trunnels") set in glue or shellac will hold well for a long, long time. Adhesives alone, not so much.

Edited May 10, 2020 by Bob Cleek