Painting lines on clinker built hull

[MASH]

How to go about painting a waterline on a clinker built dinghy?

How does one mark a "straight" line onto a clinker hull?

Is there a technique for masking, or is it just careful freehand work with a small brush?

 

[Adamastor]

I've seen a laser-level used to great effect painting a boot-top onto a GRP clinker-look boat- the marking is a bit of a schlep- each plank face has to be marked off- all the laser gives is the location of the start and end of the line at the plank edges.
I'm going to wait in eager anticip....
...ation! Surely there's a better easier way than this, or even dropping the boat into a pool of antifouling, pulling it out and letting it drip-dry?

 

[DownWest]

since I havn't noticed any large tanks of AF with cranes handy, I will use a laser when the time comes. Just need to chock the boat level to it's design water line, then two passes with the laser for the anti-foul and boot top. I already use a couple of lasers for the build, one super accurate for levels and a cheapy for lining up verticals.
A

 

[reeac]

A friend of mine who built a boat said that he simply put it in the water for long enough to get some marine fouling along the waterline and then hauled it out and used the line of fouling as his guide.

 

[cliffordpope]

That's what I am doing. The water line when I launched her last year was a bit of a guess, so I only did a rough free-hand paint job. Now she's out for the winter the line of weed is easy to see, so I'm aiming for a fixed distance of say 4" above the weed line..
But scraping off the weed does then leave parts where the exact line is in doubt. I join these up with a strip of tape, stretched tight, not trying to follow along the entire plank surface. The bits where the tape stands proud just have to be done carefully by eye with a small brush.

I think the traditional way is to set up a series of planks on trestles alongside the hull, and then project with a short straight edge and make marks on the planks.

 

[KenMcCulloch]

I hav a similar problem, needing to adjust the waterline on a clinker folkboat. In this case the problem is compounded by the shape of the keel, max draft is the aft end of the keel so she sits slightly bow-down in her cradle. However once 2 points on the waterline are identified it's easy to tap in a series of tacks in a straight line by sighting along the first two to line up the next. Easier with two people.

 

[MASH]

Thank you all so much - the expertise on this forum is truly remarkable.

Nothing easy then, as I had feared. I'd considered the bath of antifoul but discarded it as impractical given the price of bitumen paint, and thought of a laser but reckoned the plank marking to ba a tedious chore.

So tedious chore it is.

Mr Jeremy Fisher will be very grateful.

Thanks all!