Waterline.

[Tom Javor]

Having been a wooden boat owner in the past, the waterline was always safely scribed in the planking along with the upper edge of the boot. If I go ahead full and strip the boat, what's the best way for me to maintain, or reestablish, my waterline? Not sure what I'll do about the boot, the existing is too wide to my eye.

I haven't come up with any info on a search of the site - since I probably have missed it, a link would be great.

As always, thanks for the assistance.

[Oscar]

The easy way is to make sure the boat is blocked with the waterline level..... Then you measure down from a known point somewhere to establish a starting point for the new line. Then you either use a clear hose with water (food coloring makes it easier to see) or if you want to get fancy a dot laser, or ultimo fancy a spinning laser which projects a line to tape the new waterline and use the above to mark a level line.......

There is also an old old technique that involves putting up a string, parallel to the boat from bow to stern, and then a lamp midships about 10-15 feet away, and using the shadow as the mark. You need a BIG lamp, like one of those work lights they sell at the home improvement house of worship. I know this will work if the waterline is level, I don't know if it can solve for the boat not being level....(and adjusting the string accordingly).

Any of these techniques can be setup and calibrated before you take the line off. Then you recreate the exact setup and it should reproduce the location.

Finally, some waterlines rise in the rear and at the bow to more or less follow the sheer trend and fool the eye into seeing a reduced freeboard, iow in the vertical plane it is not a straight line.....if that's the case I'm not sure what the answer is. Measuring every foot and then smoothing the best you can?

[Quetzalsailor]

I was lucky when I raised the waterline on our Morgan 27; the original was scribed into the fiberglass and was visible after I sanded the old boottop and the top bit of bottom paint off. I simply eyeballed and taped an offset on one side for both edges of the boottop and duplicated it by multiple measurements for the other side.

You should be able to rent a surveyor's level. Presuming the boat is blocked level side to side, you can set the level to match the water plane fore and aft. Clearly, the fancy laser levels that ceiling installers use would make the work less tedious and you'd need fewer friends. Setting the level an adequate distance from the boat will be very useful. These levels put a usable signal out 100' or so. An 1/8' or 3/16" dot/stripe at distance is plenty good for a ceiling; a little rough for masking tape on a sloping surface.

Of course, the more vertical the hull is where you're working/marking makes for a less questionable 'tic'. It's a problem aft where the bottom tends to be flatter as it comes out of the water.

There are two '80s Catalinas in our marina whose multiple-stripe boottops are far higher amidships than at the ends, maybe 3" too high on the 36' boat. Really ugly; how is it possible that the mfr would get something so important so wrong?

[Rachel]

Quetzal, I'm just curious, do the levels you speak of need a level floor to ride on (i.e. not only does the boat have to be level, but also the surface surrounding the boat), or are they somehow different and do not have that requirement?

Rachel

[Oscar]

I think he's talking about a transit..... On a tripod, set at the waterline height, with a bubble level on the instrument. Swing it around and see the level in the cross hairs....

[Quetzalsailor]

No, indeed; I'm talking about surveyor's levels. I'm home in the dining room; if if I turn around and crane my neck just a little, I'll see three surveyor's levels: two from the 1860s and one from about 1910. Just so you know I'm totally up to date!

A surveyor's level can be set level on its tripod so that it can be used to measure angles and compare heights, using its 'instrument height' as a plane: like from a known, or arbitrary, benchmark to an unknown height somewhere else. A surveyor's transit can be set level on its tripod so that it can be used to measure horizontal angles and compare heights, like a level. But it can also measure vertical angles any direction around the 360 degrees. There are also levels which can be dipped out of their plane but which cannot measure how far they're dipped; useful when the guy on the stick moves out of vertical range or you're only interested in the horizontal angles (like for property).

So, Rachel, you can set a hull level side to side, set the instrument preferably at amidships out some distance from the hull. None of us live so well so that the instrument height is the same as the waterline height! (Surveyor's tripods can level the instrument but cannot raise or lower the instrument like a camera tripod.) Measure the distance up or down to the desired waterline, with the instrument leveled. Then purposefully reset the level so that both bow and stern measure the same from the plane that the level describes as it's rotated. It will be level over to your original point amidships but the plane of the level will match the boat, however it sits fore and aft. Clearly, cranking a level to an arbitrary plane is lots less work, and less worrisome than cranking the jackstands to level several tons of boat!! I don't know that you could fool a 'self levelling' modern instrument into setting to an arbitrary plane.

I used to teach surveying 4 decades ago, at McGill, but all we had to do was have the budding engineers and architects run 'level loops' around parts of Mount Royal. We used transits to measure the height of Mount Royal: more trigonometry than I'd care to expound upon now!

[Oscar]

Like so?



Yes indeed, modern self leveling devices cannot be forced into any other plane than level......

After thinking about this some more, it would then follow that one could easily make a sighting board with two nails and a piece of fine filament tied between them...... Adjust until the ends of the waterline are in plane and then have a helper mark every few inches....

And for three hours the marina was filled with the words "Up, up, down, down, no little more, no too much there, no you lost it....." And so on and so forth.....

[Quetzalsailor]

Yes, that's a lovely old level. It's functionally similar to my circa 1910 Keystone Bluepaper Co, Phila, level but has a more elaborate telescope and a dandy little device to finely set horizontal position, but it cannot measure horizontal angle (no azimuth ring).

Stylistically, it looks very like my 1860s Curley, Troy NY, but sold by Young in Philly. I still have repair tags in the varnished mahogany box that one is supposed to tie to the instrument when it's sent back to Young for repair. I have all the tools and attachments, plumb, except for the magnifier that one would use to read the vernier scale on the azimuth ring; and I have the matching tripod. It's a very beautiful, elaborate instrument with compass, gorgeous machining; a symphony in polished brass and polished nickel plate. The scope will dip but there's no altitude ring for vertical angles.

My third instrument is a Young, and is to my taste rather useless; it will only do quick and dirty angle measuring, and that only if you can add or subtract. It does not have the baseplate with four thumbscrews for leveling, rather its tripod has a ball joint with a clamping ring; one has to level it using the small bubble levels on the compass. The scope will dip but there's no level on it and no clamp. The compass is marked out only to a half degree. I have the box and tools, complete with a magnifier with a tortise shell case. The plumb is not original to this instrument (it does not fit in the box neatly).

I think of old goodies like these whenever I see 'Made in (red) China' on everything in the US today. Infuriating!