Does anyone have any pointers on measuring the above with a view to painting?

I normally do the bottom 4 planks on each side.

Did you do your hoop with a track in the end?

The only technical solution I have ever seen described (not used) is to set the boat up level bow to stern and side to side, and then use a straight edge or taut rope and a light to cast a shadow onto the hull.

Alternatively I suppose you could lower the boat into a very large tank of the appropriate paint.

Bill is right its the only way, Set the yot up level and measure across from a level line, except these days one can use one of the lazer levels obtainable from most DIY store. Another point if you are painting the yot upside down mark the Waterline with masking tape paint the bottom, when dry cut along the edge with a knife before removing tape, them paint top sides UP to the cut line which will A. fill the cut line and B. give you a smoooth join! If for some reason you think the MR is a keelboat and the hull is right way up then vive versa! Good luck the lands on clinker hulls are buggers which is why I guess people have made a fashion thingy out of just paintin planks personally I think it looks hideous but each to his own!I am a traditionalist but not a luddite.

Heaven Sent along with many others has the bottom 3 or 4 planks (3 I think) painted white with the join along the plank lands.  It would be very difficult to get the join to go across the planks neatly though some older boats do have varnish above and white below - however the Proctor IX and similar have more rocker and more planks per side.  If you wanted to do this Bill's method is the only practical one.  Merlins have bow and stern on the waterline - good luck!

Do a wavy line - go on!

But if you think about it the water line changes between beating and reaching, so its best just to stick to planks. or just do the whole dam boat!!!

Thank you for the advice, going to tackle it but not sure which way yet!

Jon, I have got the bits for the traveller, ie: the harken track and car but we have not been sailing the boat much due to injury. Therefore it is another job I have to do in the near future.

By the way there is enough track for two merlin travellers if anyone else is thinking of doing the same.