Finding the waterline.

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Ed
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Finding the waterline.

Post by Ed » Sun Jun 28, 2009 10:57 pm

I feel the need for some far more basic and normal things to discuss.....like boats and boat maintenance.

I am just getting closer to thinking about painting the hull of J3.

When I got her, she had like most painted Jollyboats of the time, a two-tone paint scheme with a different colour under the waterline and above. Was this common just to somehow look like you had anti-foul like a big boat?

So a couple of questions:

Why don't we see this so much these days?

I havn't done it in the past as I just didn't like it somehow. Everyone I have suggested it too has said 'don't'. Which of course just makes me consider it more, just being so board of normal colour schemes.

Do you advise a lighter or darker colour below the waterline? J3 was lighter, but J332 was darker.

If you don't have any idea of where the line should be.....how do you go about working it out....and accurately marking it?

Any suggestions of floating the boat and going around with a marker pen, or tape will be treated with the derision they so rightly deserve :P

I have presumed that if I guesstimate the point on bow and transom, that I could use a laser level to join them up....Would this work? Any ideas on how you estimate the bow and transom levels? Should line be just below water?

So, any thoughts?

cheers

eib
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Re: Finding the waterline.

Post by JimC » Sun Jun 28, 2009 11:26 pm

Ed wrote:If you don't have any idea of where the line should be.....how do you go about working it out....and accurately marking it? ... I have presumed that if I guesstimate the point on bow and transom, that I could use a laser level to join them up....Would this work?
I guess the laser level thing ought to work... There must have been a way of doing it back in the day though that was reliable... Bearing in mind no dinghy is ever trimmed exactly to its marks anyway for most classics I would have thought that from the knuckle of the bow to the hog at the transom would be a reasonable approximation.

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Re: Finding the waterline.

Post by Ancient Geek » Mon Jun 29, 2009 8:17 am

There has been a ghastly modern trend espicially in Merlin Rockets of two tone hulls that bear no relation to water lines but follow plank lands. On the other side an equalt off fashion in Dragons for single colour hulls, I think ALL boats large and small benefit at least from a waterline (Boot toping if you prefer!) and better from a different underwater colour. The OLD way was to prop the hull up level with the bow and stern waterline line points level and to (By various means - laser good?) extrapolate that onto the hull at various and join it up to form a smooth line with the waterline at the bow raised a bit, (In clinker hulls you have to jigle round the lands but it looks good if you do it.) (It looks better.) mask it and paint down, that is to say weather inverted or right way up the lowest bit (As you are working.) is the last to be done, to put it another way paint UP to the line not down to it.
Simples.

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Re: Finding the waterline.

Post by chris » Mon Jun 29, 2009 9:03 am

I've had two boats with paint below the water line, but only one that I repainted. As AG says level the boat up first. I made the assumption the waterline would be just a little way up the stem and coincide with the keel/transome intersection but not going up the transome, but I doubt if it looks wrong if it goes an inch or two up. Work on a true flat floor. Leave the boat on the trolly and chock the trolly so that the floor to bottom edge of transome equals floor to a couple of inches up the stem ( or whatever you choose ). All I used was a block of wood cut to that height with a pencil stuck horizontally on it. and worked my way around the hull.

This was on the old Nat 12 I had for a while. It had been painted along a plank for the waterline and this really looked wrong. The two tone colour scheme had a 1" blue line difineing the water line further and although it wasn't my choice work perfectly well .

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Re: Finding the waterline.

Post by chris » Mon Jun 29, 2009 9:05 am

Should have checked spelling etc first! Sorry

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Re: Finding the waterline.

Post by Rupert » Mon Jun 29, 2009 9:09 am

Chris's way is pretty much what they taught me in college (I've not used it since!) but with the boat upside down.
If you assume bow and transom just kiss the water, you won't be far out.
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Re: Finding the waterline.

Post by ACB » Mon Jun 29, 2009 11:47 am

(this post has been edited in order to be less dogmatic) :)

To be honest my method is not scientific - I just take a stab at it, but it seems to work well.

An Uffa Fox dinghy is going to sit at rest with her stem just kissing the water and her transom just clear of it, so that means we have the ends of the waterline defined.

Uffa will have marked off the waterline on the Lines Plan, because he always did. So we can plot where the waterline is at each station, both by using a tape meaure and in relation to visible features of the boat, such as the c/b slot ends, the chainplates, the mast step and any deck fittings. Stick an inch of tape on these to mark them.

Get some expensive blue masking tape and run it round one side touching the reference marks. The reason for using blue tape is that you will want to pull it off and fiddle with it a good few times. When you are happy, do the other side to match.

Incidentally a waterline should be level and straight - a boot top line should follow the sheer at the upper edge but should be considerably flatter than the sheer, so that the boot top is thinnest at the low point of the sheer, sweeping upwards forwards and aft.
Last edited by ACB on Mon Jun 29, 2009 1:03 pm, edited 2 times in total.

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Re: Finding the waterline.

Post by Rupert » Mon Jun 29, 2009 12:31 pm

ACB wrote:I detest boats painted along plank lands and single colour hulls - if the boat is varnished and sits ashore that's OK but any painted hull should have a proper waterline.
Thats a bit dogmatic, isn't it? If all boats were painted the same, a boat park would lack something, wouldn't it?
Rupert

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Re: Finding the waterline.

Post by JimC » Mon Jun 29, 2009 1:05 pm

Rupert wrote:
ACB wrote:I detest boats painted along plank lands and single colour hulls - if the boat is varnished and sits ashore that's OK but any painted hull should have a proper waterline.
Thats a bit dogmatic, isn't it? If all boats were painted the same, a boat park would lack something, wouldn't it?
I would say so, yes, Personally I think that waterlines crossing planks on clinker hulls look nasty: at almost every viewing angle you have all these jumps and discontinuities... And waterlines on hard chine hulls where the waterline crosses the chine look quite bizarre... but that's only my opinion (and I've been known to paint my boats with spots and all sorts. I'm certainly not bothered if anyone else likes their boats done differently...

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Re: Finding the waterline.

Post by Pat » Mon Jun 29, 2009 1:45 pm

Just remember which way up the boat is when you apply the paint... remembering Keith's red/green Pegasus :lol:

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neil
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Re: Finding the waterline.

Post by neil » Mon Jun 29, 2009 3:01 pm

Try Alan W's unique way of finding the waterline.

1. Cover hull completely in diesel oil/tar/road salt.
2. Go sailing.
3. Waterline should appear by magic :wink:
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Re: Finding the waterline.

Post by Ancient Geek » Mon Jun 29, 2009 3:09 pm

I guess ACB and I favour the traditional result, I am indebted to him for adding the bit about boot top.
Simples.

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Re: Finding the waterline.

Post by jpa_wfsc » Mon Jun 29, 2009 5:46 pm

Did you here about the two lads who went fishing with a pot of paint and a brush? Why - surely not to paint the waterline whilst afloat?? Nope - to mark the place where the fish were biting....



(sorry!!)

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Re: Finding the waterline.

Post by DavidC » Mon Jun 29, 2009 7:29 pm

The Merlin has a slight advantage over most Clinker boats in that the plank runs are very flay giving at least a pseudo waterline.

Do not bother with lasers, (beams not boats :D :D ). having put many waterlines on boats they can give very strange results as they cannot cope with the hull changing shape from the sides to underneath.

Once you have decided the waterline fore and aft by any of the methods including floating the boat, level the hull fore and aft on these points and of course level the boat athwartships. The most accurate method is to use a surveyors level (sometimes called a dumpy level) and having established the datum mark it off around the hull. A water level will also work but care needs to be taken for consistency with the meniscus. Both these methods require two people.

To do it single handed, put a level batten athwartships at the for and aft ends of the waterline using what ever supports or structure is needed. Then use a string with weights (whipping twine is ideal) to ensure it is tight and keep moving them at angles to touch the hull and mark points. The string must only touch in one place.

Once you have enough points marked on the hull then the blue masking tape comes into play and the artists eye to connect them with a fair curve!

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Re: Finding the waterline.

Post by alan williams » Fri Jul 03, 2009 4:15 pm

Hi All
The one traditional way to do this is to float the boat in a dry dock, wait for all water movement to cease. Then pour a small amout of thinned paint, leave to spread out to an even film across water surface. Lift boat out carefully if small or slowly drain dock. Paint line left on hull is waterline. Bit difficult today to find a suitable dock but polluted water will give a good waterline. Try Plymouth Sound on a calm day to see the effect. My other method outlined by Neil Also produces a very slippery finish.
Cheers Al finn 424 etc.

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