The Ever-Settling Waterline (Page 3)
This page was last updated on 9 October 2002.

Striking the New Waterline, 1" Above the Actual Load Waterline

Later, I continued work on the new waterline.  After setting the strings up on both sides at the new height (1" above the existing waterline), I eyed things from several angles to ensure that it looked basically right before I continued, satisfied as much as I could be given the visual limitations of the string system.

tapemarksmidship.JPG (163208 bytes)

I followed the same procedure as I used to mark my test waterline earlier (see page 2).  I began amidships, bringing the string in at a predetermined and equal point on each side of the boat, and taped the string where it touched the hull.  Because the black marker wouldn't show up on the dark blue hull in this area, I marked the string height with a short piece of tape, applying the tape just below the string.  Later, as the string entered the white old boottop, I returned to using the marker.  

stringatnewheight.JPG (148988 bytes) stringbowstb.JPG (155924 bytes)

I marked the forward half of the boat first, following the same procedure as before--pull the string in towards center till it touched the boat 4" - 6" away from the last mark, then tape it place, mark the line, and repeat until the string touched the stem.

Sorry, no picture of this!  Oops!

To make it a little easier to mark the complicated curves of the boat beneath the counter, I found that it helped to remove the tape holding the string into the bow sections, leaving it taped only amidships at maximum beam, and bringing the forward end of the string further outboard on the horizontal support to ease the tension on the string as I pulled it in beneath the counter.

tapeinplacestb.JPG (179075 bytes) tapeinplaceport.JPG (173353 bytes)

When I had one side completely marked with the string, I removed it and applied masking tape to the hull, following the top edge of the pen and tape marks.  I faired the line by eye as I applied the tape, and didn't try to hit every mark exactly, concentrating instead on every other mark or so.  When I was satisfied that the line was right on the first side, I repeated the entire process above on the other side of the boat.  The silver tape I used is 3M #225, a 30-day release tape that I really like for virtually everything.  It never leaves adhesive behind, stretches nicely, is strong, and allows for a fine paint line too.  It's pricey as anything, but well worth it.

counterstb.JPG (155329 bytes)

The counter is by far the most challenging to mark and tape.  The string, when pulled in and taped as described above, was fairly accurate, but this tape line still required much fairing by eye, checking it  from several different angles and eye-heights, particularly with the eye on the same plane as the line.  I used blue tape for this because it's cheaper to pull off and start over, and I only had a limited amount of the silver tape on hand.  The height of the camera is a bit off in this photo, but it attempts to capture the apparent straightness of the tape line under the counter.  Of course, looking at it from beneath shows all the various curves required to get this optical straightness.

bowview.JPG (194496 bytes) sternview.JPG (162008 bytes)

Here are the new tape lines (in which the new height of the antifouling paint will be brought to the bottom of the tape) seen from the bow and stern.  The port side beneath the counter is still a little off to my eye, but I'll correct that on another day.  In visualizing the new line, it's important to ignore the old boottop and bottom lines, which are irrelevant to the new line.  Still, their presence tends to lead the eye astray and fool it into thinking the new line is funky.

bownew-old.JPG (174322 bytes) sternnew-old.JPG (164007 bytes)

Because of the difficulty in properly visualizing whether the new line is "right" or not, I needed some additional confirmation.  After eyeing the thing from left, right, backwards and forwards, I decided to compare it to the original, as-designed waterline mark--the lower scribe mark, now mostly covered with bottom paint.  There was enough of it visible, however, for me to run tape lines along it on both sides. 

stbnew-old2.JPG (180405 bytes) stbnew-old3.JPG (154947 bytes) sternnew-old.JPG (164007 bytes)

In doing this, and wasting 65' of tape, I wanted to confirm two things:  that the original designed waterline was indeed planar, like my new one will be; and that my new line appeared to be parallel to this original one, 5" beneath.  I was happy to see that my new line did indeed parallel the original designed waterline (DWL).

plimsolmark.JPG (180684 bytes) I call this photo the "Plimsoll Mark" because the multiple tape marks and heights resemble the loading marks that all cargo ships have on their sides to show their proper loaded depth.  This photo shows the drastic changes that are happening here.  The new, planar waterline being struck is about 5" above the ridiculously low original DWL, designated by the lowermost tape mark.  The labels drawn on the tape should be self-explanatory.
portnew-old1.JPG (176216 bytes) This photo shows the old and new tape marks on the port side, and also provides a placement reference for the detail photo shown directly above.

From here, I've reached the point of no return:  the next step is to begin sanding off the Awlgrip beneath my new tape line in preparation for the new bottom paint.  The Awlgrip should be completely removed because it is not designed to be submerged, and will ultimately fail beneath the antifouling paint, which of course will lead to antifouling paint failure as a result.  Needless to say, I shall check and double check my lines, and be sure everything is absolutely right before I take this next irreversible step.

To recap, again, in case my descriptions are at all confusing:

  • The BOTTOM SCRIBE mark (what one might term the original Designed WaterLine, or DWL) is straight and planar.

  • The UPPER SCRIBE mark (the upper edge of the original boottop, and the point to which I raised the antifouling paint when I repainted the hull) is NOT straight and planar; rather, it incorporates a curve, or sheer, which is proper for an upper boottop edge, but not for the waterline.  This upper scribe mark is also the bottom edge of my current boottop; the fact that it is not planar leads in large part to the strange waterline we had when the boat was fully loaded this season.

  • The TOP OF MY CURRENT BOOTTOP is also curved, or sheered.

  • Finally, what I am trying to accomplish is to have the new waterline (edge of the bottom paint) parallel to the water, and straight and planar--and more reflective of where the boat actually floats.  This will give the new boottop a straight lower edge also, and I will curve, or sheer, the top edge for an attractive look.

Please click here to continue.  


Glissando, Pearson  Triton #381

We recommend viewing this site with your screen resolution set to 1024 x 768 or larger.  Problems?  Email the webmaster.

1999-2014 by Timothy C. Lackey.  All rights reserved.  No duplication of any portion of this website allowed without express permission.  Permission may be obtained by emailing the webmaster.