black staining on oregon dinghy mast

[peter c]

Hi all,
iI am just new to yhis forum and would like help ? I am preparing my sons dinghy for the sailing season and decided to sand back his oregon mast. I sanded with three diminishing grades of sandpaper and still have black stains on the timber i do not want to remove too much material in case i weaken the structure.Can anyone help should i continue sanding? or is their a chemical that will do the job?
Thanks and regards
Peter

[barnsey]

Hi Peter,

Welcome to the forum ;)

Made my first Sabot dinghy mast when I was 16 so my input might be a little dated :o

My recollections are that as with any timber that is exposed to weather, where there is any breakdown of the protective coating, moisture has the chance to get in. You do not say whether this blackening is where fittings were attached or whether it is other areas as well which might have copped a bump etc. My thinking is that it is. :confused:

Salt water does some amazing things even to lower grades of stainless - that tea staining effect!?! Oregon seems to react with that blackening. Generally it would not be a serious issue but that will depend on how long since it was last refinished, the nature of the fastenings used on it and how often & well it is rinsed after a days sailing. ;)

Having said all that if the blackening is not too serious and the timber is largely sound you will be OK. Any fastening/fitting point will affect the structural strength of the spar and there will come a point in time where that is below what you need and she'll go :eek: so you have to look at it with a watchful eye ;)

Hope this helps

Jamie

[bitingmidge]

Yep.

Unless you have a bit that's actually rotten, the stain should be easy enough to remove with a bit of Oxalic acid (sold as rust and stain remover).

If it's rot you are treating (pretty unlikely I would have thought), on a small spar, cut it out, and fill with epoxy bog.

If you want a really long lived tough finish, once you have sanded off the old varnish and give the spar a couple of coats of clear epoxy, then a few coats of spar varnish. Should last many many years of moderate use if stored under cover.

Cheers,

P

[peter c]

thanks for your assistance gents i think i will try oxalic acid first and if that does not work i will continue sanding.the black stains are not rot but possibly superficial? and by some strange means it is a sabot mast

thanks again

[graemet]

Peter,
The black stains are water damage as suggested and probably go fairly deep, specially if they are coming from fastenings (screws or bolts). After you bleach them out, ALWAYS dip your fastenings in varnish and/or fill the holes with varnish and screw them up while the paint is wet. This seals the hole so that the damage does not come back. Any varnish that overflows the holes will spread out under the fitting and provide further protection. It also helps to lock the screws so that they don't work loose as easily.
Graeme

[STEPHEN MILLER]

Black stains in timber can be removed with household bleach just have to sook the stuff in a bit and rinse well with clean water it might take a few goes but seems to work. I have done it on our keel boat to remove black stains from plywood in seats in cockpit where varnish has cracked and water has got in.
steve