restoration: adhering over old resorcinol

[dkruitz]

Hi all - I'm new here and am looking into doing a small plywood speedboat restoration for someone. The sides and deck need to be redone - apparently not owing to rot. I've been told it was built with resorcinol glue and galvanized ring shank nails over 40 years ago. I'm assuming I'll have to cut the nails off flush in order to avoid damaging the frames from trying to pull the nails out.
What will stick to old resorcinol glue - what do you recommend?
Should I sand/scrape it down to bare wood, and will epoxy or 5200 stick? Could I re-glue with resorcinol over the old? I'd probably use silicon bronze ring shank nails to secure the new planking.

Any thoughts/comments are welcomed.

Thanks,
Dan Kruitz
my hobby site: www.KruitzKraft.com

[Bob Smalser]

Both marine epoxy and 3M 5200 stick to resorcinol residue. Look at my examples to insure that's what you are dealing with. Resorcinol has a distinctive purple to black color.

The nail stubs will sweat and rust, shortening the life of the frames, a tradeoff between removal damage now or rot damage later. If you leave them in, seal them well.

http://www.woodenboat.com/forum/showthread.php?t=6799

[dkruitz]

Thanks for the tips Bob! I hadn't thought of the nails swelling - I'll have to see about sealing it then.

[Thorne]

Ah, ring-nails! Quick-n-dirty for the builder, absolute hell for the restorers years later...yet you still see folks using them. The bronze ones avoid the iron-sickness issues but still tear things up when you need to remove them during a restoration.

If you see much damage around the nails, you may need to drill at least some of them out, then fill the holes with either dowels or thickened epoxy.

Iron and steel can cause "iron sickness" where the wood around the fastener is damaged, turns black and loses strength -- could this be the problem with the boat currently, if it isn't "rot"????

Search this Forum for many threads on that topic, and the Internet as well -

from - http://209.85.173.132/search?q=cache:GXBLHoYhEuoJ:www.doc.govt.nz/upload/documents/conservation/historic/topics/stop-the-rot/ch11-stop-the-rot.pdf+%22iron+sickness%22+wood&hl=en&ct=clnk&cd=11&gl=us&client=firefox-a
The phenomenon is
referred to by shipwrights as ‘iron sickness’ or ‘nail sickness’ It is particularly
serious on oak and teak-hulled vessels (e.g., the Edwin Fox in Picton). The
chemical interactions between ferrous metals and timber are complex and not
well understood. There are all sorts of factors involved, including the possibility
of galvanic cells being set up between one end of a fastener embedded in wood
and the other end exposed to the atmosphere, especially when chloride ions
are present. Acid timbers (e.g., teak) are more prone than neutral timbers (e.g.,
kauri). For some inexplicable reason the less susceptible a timber is to fungal rot
the more likely it is to suffer from iron rot. Rot fungi seem to have an inhibiting
effect on iron rot. There is only one way to control iron sickness, and that is to
stop the iron corrosion. Either remove the offending fixtures and fasteners, or
coat them with some corrosion-inhibiting substance.