Best way to mark the top of a new boot top?

Ian_Edwards

Ian_Edwards

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Eynhallow was treated with CopperCoat last winter and on haul out yesterday, she just had a light coating of a green slime which jet washed of easily.
However, the boat has no boot top and there was a growth of green slime on the gelcoat to about 50mm above the water line which was much more difficult to remove. So I'm going to extend the CopperCoat by about 50mm, to where a conventional boot top would be.
What's the best way of marking the top of the new boot top?
Obviously, I can simply measure 50mm near the bow where the topsides are almost vertical. But how do I get a fair line as I move towards the stern where the topsides are nearer horizontal?
 
Boot tops are a pain to measure as they are not the same width along their length. TBH I would be inclined to get a professional in to paint it on (depending on cost). I doubt it's easy to correct a mistake with copperCoat!
 
Thanks for the replies so far, I've got a simple laser leveler, but that assumes that the boat is sitting level on her chocks and it still leaves the problem of curving the line up towards the bow and stern.

I'm not aware of a professional boat painter working out of Inverness Marina, so I was assuming that I'd have to do it myself, if anyone knows of a good painter who could help out in Inverness, I'd certainly look at that option.
 
No, no. Parallel is a nasty modern trick which spoils the line of your sheer. Don't believe me, believe the sainted Tom Cunliffe.
 
I've a vague, possibly imagined, recollection that St Tom's suggestion was to go for a fixed percentage of the freeboard along the length of the boat.

Assuming you're out of the water, I'd make a boot top out of tape, and play with it until it looks right.

If you're afloat, you could still do it, albeit at the risk of providing some shadenfreude for onlookers, but use plastic tape, not masking tape, especially not the cheap cream-coloured stuff.
 
pvb said:
I think he was probably quite keen on 4hp engines and kapok lifejackets, but times change. ;)
Click to expand...

I don't think he was keen on either.

When he had a 4hp Stuart-Turner engine in Wanderer III he was disatisfied with yacht's performance under power and had Wanderer IV fitted with a 61hp Ford.

Quote (by Hiscock): " The cork or kapok Board of Trade is too bulky to to stow in a small craft ..."

Anyway, the point of having an upward curve in the boot topping line is to improve the appearance. A horizontal line on the side of a yacht looks ugly.
 
Ian_Edwards said:
Thanks for the replies so far, I've got a simple laser leveler, but that assumes that the boat is sitting level on her chocks and it still leaves the problem of curving the line up towards the bow and stern.
.
Click to expand...
I went through this recently and whilst not easy you can get a fairly good approximation with a laser level. You need to fix the level so that it isn't always trying to produce a horizontal line (most have a locking switch for this) then mount it on a tripod and play around with height and angle until you get it visually right. Mark a point fore, mid and aft with masking tape or similar that is 50mm above your existing coppercoat and play with the laser until it passes through all three.
 
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PBO November 2010 No 528 - 'Reader's Tip' article on exactly this subject of marking/extending (or reducing) a boot-top line.Using a simple 'jig' of a couple of blocks of wood and a small spirit level - costs nothing and it works (I've used the method a couple of times now). I don't want to reproduce the article here but if you don't have (can't get) a copy, PM me and I could possibly send a copy to you.
 
IMHO it would have been betteer to mark the extent of the fouling before you removed it and use that as the line for boot topping. ie let the water make the mark.
In any case next time you lift her out of the water after you increase the boot topping this time you will probably need a bit more correction. good luck olewill
 
Thanks again for the replies, it's too late to use the scum line, the yard pressure washed that off, although it's a good idea.

I'll attempt the St Tom method of using a fixed percentage of the topside, but I'll measure from a style strip which picks up the line of the hull ports, and follows the shear line, as the datum. I'll combine that with a, "does it look right" test. I plan to use short lengths of Black PVC tape to mark the edge of the top of the boot top, and then run masking tape along the top of the black tape markers.

The lower edge of the boot top doesn't need marking, I'll just run the new CopperCoat into the existing CopperCoat.
 
This upper edge of this boot-top is swept upwards towards the ends of the boat. If it wasn't it would appear to droop at the ends. (As does the lower edge)
 
Check the athwartship angle of the boat on the hard with a spirit level. They are seldom exactly level. Then chock up a pole at the bow across the hull and level this the same as the hull. Tape a string-line to the required position of the top of the line at the stern and drop the other end over the pole with a weight on it. Move the line outwards so that it is just touching the hull at the stern and tape it to the hull with a bit of masking tape. Move the line in slightly so it again touches the hull about 6 inches forward of the first mark. Tape the line in place. Continue doing this until you have reached the bow. (The bits of tape stop the line sliding down the hull). Mark the position of the line along the hull and then mask the full length ready for painting. This ensures a perfectly straight line on the curved hull no matter how the boat is laying.
 
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