hi gang
i am going to be putting on a waterline, on my new boat. now most of my boats have been painted. but all one colour. black ,blue, red and white.
my new boat i want to paint it navy blue. but where the boat meets the water . i want to paint it white. but i am not sure how to 1) mark it. and 2 ) paint it. just wondering how you do it. and if you have any tips
cougar
Hi Cougar,
I am presuming that you are building an IOM from the posts on this and other forums over a period. If so, if you presume that the waterline just touches the bottom of the transom and just touches the toe of the bow, then set up the hull, inverted, on a smooth flat table top, with a dressed wood batten under the aft deck to ensure it is level transversly and packing to suit under the foredeck to ensure the proposed waterline is level longitudinally. Acquire a piece of 1/4" plywood, another piece of the dressed wood batten and a sharp hex sectioned graphite pencil. Be prepared to sacrifice the pencil. With cyano, glue the plywood to the wood so that the assembly can be slid along the table top with the plywood sitting vertically and the wood batton acts as a base to support it. Offer up the assembly to near the transom, making sure that the plywood is at least more than half of the beam of the hull away from it. Hold the pencil against the plywood so that it points slightly downwards towards the hull and cyano it to the plywood so that the pencil point is touching the transom just at the level that you want the waterline. Hey Presto! you have manufactured a height marking gauge!! Carefully run the gauge around the hull, gently marking the waterline. Use fine edge masking tape, there is a 3M product used in the auto spray business that is very good. A roll will line out an 11m yacht twice over and the rest. Gives a good sharp edge and can go round gentle curves, which is important.
Sorry if all that was very pedantic, but I am not sure how to add a sketch to this forum.
Cheers
Ralph Knowles
Ralph indicates a preference to do the hull upside down. This photo illustrates the way to hold/scribe with pencil. The main issue is to assure the bow and stern are level. You can spread talc on water and place boat in talc which will adhere to hull. Remove from water and place marks along the talc line, tape and paint.
Or as suggested by Ralph, you can use a method similar to this.
Another method similar to talc method above:
HOW TO PUT A WATER LINE ON A NEW BOAT
by Geoffrey Moore Langdon
- Fill the bathtub up to the top (stuffing towels) in the overflow if necessary to get the appropriate depth.
- Put a few drops of vegetable oil in the water.
- When you take the boat out carefully, the oil sheen should still be visible for a while, marking where the line should go.
- Use very thin 1/32 inch architectural black line tape to follow above the oil mark (masking tape only if you really cannot find the better tape). This is only temporary, as you would want neither the weight nor the turbulence of a tape waterline bulging out.
- Once the tape is in place, go all the way around the boat placing two or more tapes packed right next to each other below the first tape.
- Carefully peel off the middle tape.
- Paint the hull in the exposed area masked off by the two remaining tapes. This assures a uniform thickness to the painted line.
- Peel off the two remaining tapes and you are done.
another method is to use a water level. Tape a piece of clear plastic tube much longer than the boat to the hull at the forward waterline ending. Fill the tube reasonably full with water. Use the water level to adjust the height of the stern to give the correct position of the aft waterline ending. With another similar tube, ensure that the boat is vertical by measuring the amidships sheer heights on the two sides. Now take the hex pencil and tape suggested by Ralph. Go round the boat with the water level and mrk tye waterline with as many points as you think you need. Mark the waterline with tape and paint.
Note: this method CAN give awful results because of harmonic oscillation in the water level. The answer is to use a central ‘tank’ of capacity a couple of litres as a damper. Easily made from clear tibe, a big plastic fruit juice container and some sticky tape.
dick, what is that?
As I said in my disertation about marking a waterline, I presumed that Couger is painting an IOM (International One Metre) This has a draft of 420mm, and to mark the waterline accurately you need a steady boat with ballast at the proper weight and position, not only to represent the keel and fin but also the full rig, electronics and batteries. To float test it for waterline is best done fully fitted out, with all correction ballast, but at the stage of painting, usually the hull is nowhere near fully fitted out. At 420mm draft, my bathroom floor would be very wet as the bath is only 369mm deep. I am fortunate in that I have access to a measurement tank that we as a club use to check IOM’s, over and above the fundamental measurement, as per the rules, and I would be a bit miffed if it was contaminated by talcum or baby oil. To mark it up the right way up,it would be much more difficult to get the hull level. No bilge keels on an IOM. As for the water level tubes and reservoir, that may be OK for a fishing boat or a cargo ship (fullsize) but too testicle (eh! technical?) for a One Metre. Been there, done that, on the inclination test and lightweight survey of a semi-submersible oil production rig. At such a small scale as envisaged, the miniscus at the water surface would lead to inaccuracies. A steel rule measuring up from the table top is far more accurate.
Regards
As I said in my disertation about marking a waterline, I presumed that Couger is painting an IOM (International One Metre) This has a draft of 420mm, and to mark the waterline accurately whilst afloat, you need a steady boat with ballast at the proper weight and position, not only to represent the keel and fin but also the full rig, electronics and batteries. To float test it for waterline is best done fully fitted out, with all correction ballast, but at the stage of painting, usually the hull is nowhere near fully fitted out. At 420mm draft, my bathroom floor would be very wet as the bath is only 369mm deep. I am fortunate in that I have access to a measurement tank that we as a club use to check IOM’s, over and above the fundamental measurement, as per the rules, and I would be a bit miffed if it was contaminated by talcum or baby oil. To mark it up the right way up,it would be much more difficult to get the hull level. No bilge keels on an IOM. As for the water level tubes and reservoir, that may be OK for a fishing boat or a cargo ship (fullsize) but too testicle (eh! technical?) for a One Metre. Been there, done that, on the inclination test and lightweight survey of a semi-submersible oil production rig. At such a small scale as envisaged, the miniscus at the water surface would lead to inaccuracies. A steel rule measuring up from the table top is far more accurate.
Regards
Ralph
You can mix and match. The biggest advantage of the water level methof is that it is easy to get the boat level fore-and-aft and transverly.
Maybe I should have said in my first post that the hull be level (parrallel) with the table top both transversly and longetudinally. Just being ‘level’ is not enough when gauge marking from a fixed surface.
Ralph
This is YORKSHIREMAN - a British Salvage Tug (from early 1990’s). Has been renamed and is now in Portugal with different paint, etc.
Available through Modelslipway.com http://www.modelslipway.com/york.htm
A bit of history about the original “real” boat at this site, plus ordering info. Was pressed into service by UK (along with sistership “IRISHMAN”) during Falklands War.
Model is not mine though - kind of thought about building one, but that would lead to another and another. Rigged out a bit non-scale and it could make a great boat to retrieve a sailboat from middle of the pond. 
actualy this is for a 3r. but i will also be adding it to my new IOM. i never thought of the pencil idea. this is a good one. but what if you have overhangs? the IOM will have the waterline stem to stern. but the 3r has almost 8 inchs off the stern and 6 inch off the bow? i think the pencil idea will sitll work.
what i was thinking was filling the bath tube with water. then putting a cup of cooking oil in. wait untill it spreads. and then load the hull up. and place in the water. the oil would stick the the waterline? would it not. if this does not work. could you place the boat in first. wait untill it settles then pour the water?
:graduate:
all good ideas though
cougar
Dick has it right. Use the tub. I have done this more times than I can count and it works better than any other method. Anything that will collect on the hull will work fine. I would hesitate to use oil because you would have to get it off your hull afterwards… and this is about to become a painted surface… oil would not be my choice. Technically… dirt and dust are about as good as anything else. If you pencil sharpener shavings etc… it works great and rinses off fast and clean. You don’t need an agent, the static cling will work more than enough and is just that much easier to clean afterwards.
Set the hull in gently, and let it come to a complete rest, and lift it out the same way. Just being careful/cautious is good enough to get a perfect line.
Mark it with a pencil, tape it off and you have it nailed. I have tried the marker sliding around the hull trick, and if anything moves… the boat, the pencil either one, at any point… .if something gets underneath the pencil holder, if the surface is not perfect… your line is off, and that is all predicated that you can mount the hull exactly parrallel in plane.