hi
i'm looking at sanding the bulkhead back to bare timber and varnishing. I am not sure which would be the best varnish to use. International have; Woodskin, Schooner, Schooner Gold, Compass and Original !
This is an example of the ply used;

For interior work it is not really necessary to go to a marine brand. Just an excuse to double the price.

Wattyl Estapol Satin is a single pack oil based finish. Satin allows multi coating without sanding between coats. If you add about 5 to 10% linseed oil for final coats you will get a rich deep gloss that is not glassy and is quite tough against abrasion scuffing. Clean up or thin with turps.

Another great product is Cabots CFP. This is a water soluble/based polyurethane designed for timber floors. It cures very hard but remains very tough. Clean up with water, thinning not recommended. Minimal odours, recoatable after an hour or two (get the job done in one day).

Both the above finishes are easily spot repairable without having to sand the whole lot.

If you have panels that are removeable and therefore have exposed end grain, two or three coats of Wattyl Timber Preserver (a thinned out epoxy two pack product also known as Everdure) is highly recommended. This will densify and permanently seal the timber.

It then needs to be sanded and overcoated (it is UV sensitive and will break down with exposure) with either of the above products.

If you use the Cabots CFP, you could eliminate using the Timber Preserver as the CFP does the same thing while also being a finish product.

Happy dibbing and dabbing.

Just to bring this topic up again.

What is best way to remove the old varnish from these bulkheads. I know you can use chemical strippers, but can these dry the timber out and make it look lifeless.
Or should sanding be used, what grades of paper at what stages would be required.
Any advice welcome.

From the above advise it will just use an Estapol Satin

Pull scraper then smooth with a fine oxide paper. No need to remove all the varnish unless its flaking. Don't use anything coarser than 240. I like International Schooner, I like the smell. Estapol is fine but its not quite clear like a real varnish. Just remember that teak is probably just a thin veneer so sand carefully.