Raising the waterline - what is the secret?

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Gerry

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I want to raise the antifouling a couple of inches next time we haul out. What is the secret of masking it evenly all the way around the hull? Obviously I can't just measure up two inches along from the current line because of the varying slope of the hull. I guess there must be some trick to it.
 
um, not that bad. use a wipeable marker or pencil to mark some points, to start. At 45 degree slopy bits its 1.414 times 2inches higher and so on using cosine of the angles of slope. This doesn't need to be too mentally exact, really, cept you need a calc to find a few cosines of angles first annd praps a rubbishg protractor to sort of guess the angle.

Then set a coloured tape which covers the bit you are going to paint with tope edge at those estimated points. This way you can eventually stand back and see if it "looks right" and correct by adding more tape higher over the top repositioning it a bit lower and so on.

Then, when all looking right, set the actual masking tape edge (up to which you will paint) exacerrly from the new top edge of the coloured tape. Then strip the colored tape off and that's your level for painting.

You could use fluid levels and clear tube to find 2 vertical inched higher but i reckon it would end up a right mess, and be a bit painfully slow, unless you're a physics teacher which er you obviously aren't :-).
 
Presumably your current waterline is straight when view from some distance. If so I'd use a laser level and align it with the current line then move it up to give the line in the right place. You can then mask directly or use a pencil to mask it later.

FWIW, I got a steel tape measure with a built in Laser level from Macro recently for change from a fiver. I still haven't figured out a use for it apart from giving paranoid neighbours a scare (little red dot over the heart... /forums/images/graemlins/smile.gif), but it was too cheap to miss.
 
Use a Water Sight Line. Here's how to make and use one....

Identify and mark two points on the hull - on your transom and bow - each one 2" higher than existing paint.
Take a plastic hosepipe, and insert tightly a see-through short 'sight-tube' at each end.
Secure both ends separately - e.g. with gaffer tape or free-standing ( people ) - to your transom and fill tube with water until visible meniscus in each sight-tube is level with your transom datum mark.

Leave one tube secured at transom, then move the other to your bow. Adjust bows up or down until the visible meniscus in the sight-tube is aligned with your mark, 2" above the bows boot-topping. The boat is now 'levelled' fore and aft.

Level the boat 'acrossways' by reference to e.g. the main halyard hanging freely aligned above the gooseneck. You can also use the 'sight -tube' as above. The boat is now 'levelled' acrossways - or athwartships, if you have a really old boat.

Now move the second sight-tube progressively around the hull, marking at - say - 1 foot intervals behind the visible meniscus level - which is always at the same level as the first one.

Join up the dots, mask with appropriate tape, and paint.

It's twice as hard with a catamaran, and three times.....
 
There are two ways that I have raised and put waterlines on 4 boats recently.

One is to use a laser with a flat line, and another is to use barrels, planks, and a chalk string.

For the laser way, level the boat up fore and aft and athwartships. Put the level laser line horizontal in all planes amidships, and mark along the line. Move the laser fore and aft as you need it, lining up with the midships start. This will take into account any bow and stern counter.

The other way I have done it is using the barrels and planks and two other people if you can get them. Again, ensure the boat is level fore, aft and athwartships. Place the barrels or anything to lay a plank on horizontally, at the bow and stern. Get a chalk string and with the fore and aft ends kept tight, move it in towards the midships area until you just touch. If it is too high or too low, move the planks up or down. Starting from midships, get your two helpers to move their ends in\out as you go along the hull pinging the string.

With either way, when it is marked, put tape along the top edge and get on with painting\antifouling.

I had to do this with one boat that had a waterline like a donkey's hind leg. The answer to that one was to put on a boot topping to level it all off.
 
Been thinking of doing the same. I'm fed up with scrubbing the stain off the boot top with the boat in the water.

I notice that a lot of more modern boats continue the antifoul way above the waterline. It seems to be a good trick to make the topsides appear lower than they really are as well. Or am I being cynical?
 
Gerry,

I play with lots of lasers at work & they aint cheap, but most if not all of the big hire companies have them. Again it aint cheap but you only need it for a days hire, and you can get a demo etc. in store.

The diy ones are ok but absolutly useless outside on a bright day.

good luck.

poter.
 
If you are sure your boat's previous antifouling was ok, and you just want to raise it 2 inches, then just dangle a plumbline marked at 2 inches, so the bob is level with the previous line. Line up the two inch mark by eye (or spirit level) to mark the new line every few inches along the hull. Join the dots with a straight edge and apply the masking tape. if the previous antifoul was crooked, then you'll have to use one of the complicated methods using a laser.
 
Hose pipe is the way to go.
Now here's the micky mouse way..On a nice calm morning sit in your dinghy with a length of 2inch polystyrene bobbing in the water along the waterline.Using a magicmarker make a series of horizontal dashes in line with the top of the 2inch polystyrene as you float it around the hull.
B.T.W You will need to dewax the hull before painting..acetone works . And very often after you have painted the 'perfect' line you may wish to curve it up at the ends,just as the Greeks used to put belly into their columns to make them APPEAR perfectly straight from afar..
 
I did exactly what you suggest to put a boot top on my last boat. I used the planks and string method with a special twist. I did it on my own. What a job!
Rather than planks I used the two parts of some extending alloy ladders.
You would be amazed how far out you need to move the strings to touch at only one point. Do not try to mark more than one spot with the string at a time as it will roll down the hull and give you a very wobbly line.
I put it 4" above the antifoul and used black gloss because it is scrubbable.In which case put the boot top on first and run your antifoul up over the bottom edge. Otherwise water will creep up behind the boot top and it will bubble.
I would use the laser method another time.
It stopped all that slime. Well didn't stop it, but disguised it well.

Antifoul02.jpg



Antifoul01.jpg
 
A beautiful job. Well done.

BTW, on another boat that had no antifoul, the barnacles and weed made a perfectly straight flat line of foul on the bottom. Before I pressure washed it all of, I marked the top of the fouling every 6 or so inches. I then got the boat level fore and aft, and athwartships on my own level drive, sawed a piece of wood two inches longer, and went around the boat and remarked, taped and AF'd. Admittedly, it was an 18ft speedboat - a bit easier than when I did the 22 and 26 footers.

The clinker 14 footer was a bit more of a challenge, though I did it the same way as the 18ft speedboat.

Didn't think of the water tube method for the boats, though I levelled off our utility room with one.

That makes three methods. No, four if you count the polystyrene method /forums/images/graemlins/wink.gif - good one.
 
Many thanks for all the advice. A key thing seems to be to get propped up the boat as level as possible on the hard.

Any idea what method most maufacturers use to mark a waterline ?
 
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