covering plywood on carvel planking

I've worked in both inch and metric in tool and gauge making and while the division by 10 is inherently more sensible, i found that metric measuring instruments like mics and gauge blocks were more involved for me

metric measuring is slightly finer than inch as 1/50 mm is .00078"

 

I openly admit I'm not comfortable with the metric system and I rarely use cm, just mm and meters.

 

Every one can use the micrometer in inches, when the mm micrometer shows up, work goes to 1/3 speed, lots of ciphering and conferring goes on and results are suspect.

 

We had this completely senseless debate here several times.

http://www.boatdesign.net/forums/op...erial-poll-549.html?highlight=metric imperial

Of course metric is the more precise and far easier to use system. That is the reason it is worldwide agreed, and that is the reason why people never go back to imperial once they got familiar with metric.

But as clear is the fact, that someone who is familiar with imperial, and who has worked a whole lifetime with it, can not only get as fine and precise results as the metric guy, he has a natural problem to change his way of thinking.
The British are still not entirely landed in the metric world, after one generation.

Paul,

2 inch are 50mm or 5cm... you have not been too far away

 

Australia also has similar difficulties with the conversion.

 

well ausies have a problem with their blood rushing to their heads

 

The water swirls kittywampus too...gotta affect the thinking!

 

hell, that would confuse me

 

meanwhile,
the cabin top and sheer of Tetranora is not painted, it is vanished wood but this needs regular varnishing.
i want to sand there, paint with epoxy and polyurethane top coat. so this will go for five years.
what would you think about this.
i dont want to ruin the beauty but this will be a better way to protect it. and if i paint it to a nice colour maybe it will look beatiful.
which colour do you recommend?

cheers

 

two things you can do with a boat, sail it or keep it purty

 

so i will paint it. And keep enjoy sailing instaed of working hard to keep it purty.

 

I would NOT paint it.

This boat survived 50 years of extensive sailing due to one major fact.
She was always kept in her original condition and admirable appearance.

Cheap tricks and cutting corners will soon decrease her value.

You bought a masterpiece of boatbuilding skills, now go through the related pain to maintain it!
These gems are owned by all mankind, You only have the right to sail it for some years!

I doubt the cabin is Epoxy coated under the varnish, but you can find that out very easily.
If she was coated, she was so on the interior surfaces (roof) as well.
Sand down a small area inside just to remove all varnish, and try to penetrate the open wood surface with water. No ingress= epoxy treated

If so, sand down the old varnish (outside of course), apply one layer of neat epoxy, let cure and varnish then with a 2k PUR varnish which is UV protectant. (not resistant!!! Protectant)
Apply at least five coats. Then forget varnish for some 5 to 8 years.

If not Ep coated, sand down and apply a "open" varnish like "Le Tonkinois" in several coats. One touch up in spring, another in autumn, keeps her looking good.

Maybe PAR has a different recipe? Restoration is his minefield, not mine.

Regards
Richard

 

I see no reason to add epoxy to this boat and I find it difficult to believe that someone used epoxy on her. Epoxy will not make keeping the finishes any easier, in fact may make them a little harder. She appears to be a well kept original boat, so her best interests in mind, she should be kept in a similar fashion.

I don't think it's necessary to test for epoxy, you'll figure it out soon enough during finish up keep and repair. If the finish is bright, keep it in good shape, other wise you'll find out quickly if there's epoxy or not under them.

For the record, there is no varnish or polyurethane that is UV proof or a true UV protestant. Some brands are much better then others, but none completely protects the wood. If you can see the wood, it's UV protection is limited. Now with this said, if you keep a good quality clear finish, with high UV inhibitor count on the surface, also with sufficient film thickness, then you can expect UV damage to the wood below to be minimal, assuming you recoat in a timely fashion.

 

i neglect the varnishing job since i bought her(last winter) so the sun detorieted the old varnish, in some areas it is completely gone and you can see the bare wood.
i think it is not epoxy threated.
so what should i do now?
should i sand down all till bare wood?

 

Yes.

Then varnish again according to the advice given above.