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After some considerable effort, we've completed the removal of many layers of bottom paint and barrier coating. What I failed to realize was that in the process, we were obliterating the original water line . I've got a few references where it used to be, but connecting the dots is not going to be pretty nor accurate in my opinion.
H E L P !
1. Does anyone have an idea by which we can reconstruct the waterline scientifically - without putting the boat in the water and going around with a crayon??? Is there a scantling diagram somewhere
2. Would anyone (who's boat is on the hard) be willing and able to measure the distance from their rubrail to the waterline at, say one foot intervals?
I'm sure that there are many ways to reestablish the waterline on your boat. I'll mention one of the ways that worked for me in the past. This method works when your boat is on the hard, especially when a few waterline reference points remain.
You have to level your hull in both x-x and y-y modes. This can be done by jacking and shimming lengthwise, and by rolling the hull with the adjustable pads, or poppets.
Beam level can be established by laying a straight, true 2"x4" or maybe a piece of aluminum across the coamings. Lay a spirit level on the straightedge and adjust the hull until the bubble is dead center.
The bottom of your keel, if not exactly, is very close to being parallel with your waterline. If your boat is on a trailer, it can be made level lengthwise by adjusting the tongue jack up or down. If the boat isn't on a trailer, you can jack and shim the hull from either end until level lengthwise. I use pads at the pressure points.
I use a rotating or swiveling laser level. This is mounted on a level table, platform or an adjustable tripod, somewhere about midship. The laser level is elevated to the point where the ruby dot is at the remaining old waterline, top or bottom. As you pivot the level along the hull, with earlier diligence in leveling, the waterline should be transposed along the entire hull.
If you are marking the top of the waterline, lower the laser level as much as the width of the desired waterline. This will enable you to increase the width where the hull contour rolls under at the bow and stern.
This may sound complicated, but once you get into the actual job, it's not really that big a deal.
I went to my friendly neighborhood hardware store and bought about 30 or 40 feet of clear plastic tubing which I then filled with water. Bearing in mind that the water free-surface at both ends of the tubing seeks the same elevation, the tubing can be used as a level. The small diameter tubing is quite inexpensive.
That tubing technique might help to set up the boat level and laser level and at the correct elevation w/ respect to the boat.
You can use the clear plastic tubing technique by yourself, but it helps if you have an assistant.
With Tod's water level you do not need a laser or much space. It is extremely cheap and accurate. A couple of tips; make sure there are no bubbles in the tubing. Get a piece of tubing longer than you need so you don't spill any water out of the other end while you are walking around. Hold both ends of the tubing together and raise or lower them untill the water level is where you want it. You could easily do the job by yourself if you duct tape the fixed end to the hull once you set the level. To speed things up a bit hold your thumb over the end of the tube untill it is close to the right level. This dampens the "wave" action in your tube. You can do all the way around the boat without a clear sight line or resetting a laser. It would be much faster and more accurate than working from someone elses measurements no matter how much time both of you spent taking and making them. Think of it like floating the boat in a tiny little tube, steve.
Thanks for all the input my friends. The boat is sort of on a trailer, but the trailer is not level, nor is the boat perfectly level on it. I removed the bunks and installed hull jacks, to facilitate the removal of more paint. I guess I can wait until I get it back settled properly on the trailer before worrying about the waterline. Meanwhile I am going to start the barrier coat on the keel and most of the way up the hull.
O J, somehow I knew you'd have something good for me, and I'm glad to see you back on the site! I hadn't thought about the laser level. Great idea. I have one that does dotted lines, solid lines and a single dot. From 20 feet away I can probably get a good reference point to start from.
Wombat - I sent you an e-mail, thanks for the numbers. If nothing else I'll have pencil marks that I can double check with the laser level.
. I've got a few references where it used to be, but connecting the dots is not going to be pretty nor accurate in my opinion. 
