water level for marking waterline

[Guest]

Last Saturday I spent several hours jacking my boat to get it dead level for applying a new boot top . I used a water level for this operation. It was simply clear 1/2 inch garden hose. It was only coming towards the end of the task that I realised -water does not find it's own level!!! It appears that small air bubbles got trapped along the hose leading to marginally different weights in each of the hose legs. Has anybody had a similar experience and solved the problem?- perhaps using an additive to reduce surface tension and hence loosen the trapped bubbles?

 

[Guest]

Another way is to set up a lamp to the side, at water level and far enough away as to shine on a good portion of the side. Set up a level blanking piece ( strip of wood, cardboard why )so that the shaddow is at w/l or boot top level then mark your lines. It is best done at dusk or dawn. Hope it helps.

 

[Guest]

That's amazing with 1/2" hose (not doubting you) - wonder if adding detergent'd help bubbles to rise out - it'd lessen the "surface" tension of the bubbles. You didn't have a hose substantially longer than the boat, did you? - if there were coils, they'd trap air very effectively. How long's your boat? Bows in a different pressure system from stern?

 

[Guest]

But how do you know if it will float "dead level"?

Usually they use a larger diameter tube so I assume the percentage effect from the bubbles is minor. If you can apply a partial vacuum to the hose, that should enlarge the bubbles so they float off.

 

[Guest]

I did exactly as you describe using quite thin tube without (I believe) problems with bubbles. I added some antifreeze to the water to give a colour dye and sucked the mixture into the tube from a bucket. No bubbles, just don't suck too much or you get a mouth full, hence the benefit of the colour dye. We have used water levels in the construction industry for years.

 

[Guest]

I did exactly as you describe using quite thin tube without (I believe) problems with bubbles. I added some antifreeze to the water to give a colour dye and sucked the mixture into the tube from a bucket. No bubbles, just don't suck too much or you get a mouth full, hence the benefit of the colour dye. We have used water levels in the construction industry for years.

 

[Guest]

Re: But how do you know if it will float "dead level"?

I would have advised a smaller diam. hose ....

For Commercial work on determining draft on vessels alongside quays .... the draft that we cannot read ....

Read the side that can be read. Lay the pipe across the deck and stand both ends at similar points on the deck and measure difference in height. It has been tried with large bore pipe, but a) it was unwieldy, b)subject to bubbles as posted here, c)solved by using narrow gauge about 1/4 OD clear with Red Food dye added to the water to eally make it stand out.

Why would we want absolutely accurate draft .... we use it to determine weight loaded by Draft Survey on Dry Bulk Cargo .... but thats another story !

There is another way to mark w/lines ..... When you lift the boat out for winter ..... etch the 'dirty marked w/line' into the boat, measuring down from toe-rail each side to get symmetrical line. Cleaning / work then will NOT remove your reference AND it will be in line with the actual floating characteristic of your boat. I would also advise to add 1" to that line to ensure you are well covered. Maybe in contrasting colour to make a w/line stripe ?

 

[Guest]

If you have a long enough flight of stairs ........

Fill tube with water. Seal one end - anchor open end in bucket of water walk up stairs to over 10 metres (33 feet in old money) and you will see water break away from top of tube as it starts to pull a complete vacuum. Air bubbles will come out of water and float up to top of tube to fill vacuum. Walk further up the stairs (water will stay at same level) and more air (mainly oxygen incidentally) will be released. Leave overnight. Next morning tap tube all the way up to release oxygen trapped on walls of tube and when they have all floated to the surface run back down the stairs with the sealed end and cut it open before all the oxygen reabsorbs itself into the water.

Alternatively - you could use boiled water (which has already had the oxygen removed) with a tad of car windscreen wash to reduce the surface tension.

Best regards ;o)

Ian D

 

[Guest]

Water level marking made easy

Consider giving the water trick away, find a builders Dumpy level.
No need to level the boat fore and aft only side to side. Place level so can see fore and aft ends, place a stick (off cut) under or above your proposed water line at the bow or stern, make a mark on the stick and take it to the other end, adjust the tilt on the level so that you can pick up the mark at both ends, this may take a couple of adjustments, then you can put the stick at any point anong the hull, sight the mark and draw a line.
I have used both methods and the builders level is faster, less work and more accurate.
I hope this will help.
Old Salt.

 

[Guest]

Re: Water level marking made easy

Many thanks for all the tips . On this occassion I used a basic builder's level -for which I had to level the boat completely. Next time will look for a 'dumpy' level to avoid this work or may try using the thin tube with antifreeze mix sucked into it .

 

[Guest]

a laser is the biz

i splashed out £80 on a builder's laser level as i had to do a lot of levelling while building my cat. i've never had success with water levels and this is the business. you probably don't want to spend that sort of money but you could hire one.