I sailed dinghies in my youth (I'm 43) and have just inherited a mirror from a neighbour and intend to take my sons out. Can't wait.
The dinghy's sound and water tight. I've given the top a good couple of coats of varnish.
In the winter I intend to do some 'proper' restoration but wanted some advice on temporary hull repairs to just keep her going over the summer.There's quite a few paint blisters and peels on the hull, and I suspect some filler. I intend to rub these down but wondered what was best to treat the then exposed ply before repainting - ie, do I varnish the ply, then repaint, then varnish the whole hull over the paint?
Yes, rub down to remove blistered and peeling paint. Then you need to apply enough paint or varnish to keep the ply in good condition until the end of the season. In the past I would have recommended using International Paints
Universal Clear Primer as priming coat. This product can be used as a primer for both one-pack (i.e. normal paint) and two-pack (i.e. paint which needs a hardener mixed with it) systems. However, International have replaced this with a 2-pack alternative which I've not had a chance to use. So I suggest you thin some varnish by 10% or so and use this to prime the bare ply (look at the manufacturers instructions). Then one coat of un-thinned varnish on these areas, then a couple of coats of gloss paint, or one coat undercoat and one coat gloss. You would probably get away with just one coat of gloss (but might not cover the underlying colour very well). Don't forget to gently rub down between coats with say 240, 320 or 400 grit sandpaper (again, follow manufacturs instructions as this may not be necessary if coats are applyed shortly after each other)
If the remaining paint is sound, it should last the season OK.
You could thin paint down and use that as a primer (again, follow manufacturers instructions regarding the % of thinner to use), but I prefer to use varnish as you can see if you have nearly rubbed down through the paint film. Also, if a future owner wants to remove paint and varnish an area (recently done this on one of my boats), it's a lot easier to do that if the area was primed with varnish rather than a metallic primer or thinned paint.