How best to apply the perfect waterline?

[Mark Baumgaertner]

So, I am nearing the completion of glassing my hull with fairing and sanding left to be done. I'm going to be applying a coating called Wetlander" to the bottom areas waterline down. The coating is a highly durable slippery compound used primarily on flat bottom boats that frequent the shallows of rivers and swamps. Enabling the watercraft to slide easily over sand and gravel bars. I'm hoping it will enable me to self launch my CS 20MK3 off of beaches etc.

 

My question is what is the best way to draw my waterline? Any suggestions would be helpful. 

[Mike Vacanti]

Here is a video that shows one way to do this. This channel has a lot of interesting boatbuilding videos.  Mark a waterline on a dinghy

[Jknight611]

Graham did a demonstration at the Messabout several years ago,  I am actively looking for the notes I took.  I used his technique on my CS20.3 and I like how it came out. Maybe Graham will join in.

[Joe Anderson]

There are numerous ways to draw your waterline. Carefully because it is one of the first things everyone will notice  at least for the first year.

This is some suggestions from some of the forums best. Though it is hard to go wrong watching Lou.

 

https://messing-about.com/forums/topic/9887-grahams-bootstripe/?tab=comments#comment-90417

[Steve W]

That method Graham shows is to get a variable waterline, which might be best for our light boats, whereas the video is to get a straight one. An alternative is to put the waterline a bit higher than normal. I think a waterline that is too low (right at or below the waterline) looks bad. I haven't done anything on Skeena but I'll be watching.......

[Reacher]

The masking tape method looks interesting and I might give it a try sometime.

 

I marked the waterline on a friend’s CS 17 using a laser level and it worked out well. The boat was blocked fore and aft so that the level registered to the design waterline marks on the bow and stern as taken from the plans. Then the boat was leveled side to side. The laser line was traced onto the boat. Then the laser level was raised 2.5 inches and the upper line was traced. The “as painted” line was wider at the transom and noticeably wider at the bow due to the slant of of the hull at those points. If you try this method it is important to trace the laser line onto the hull continuously or with a mark every two inches or less. Otherwise connecting the dots will not give a true curve. And I recommend a self leveling laser (Bosch has a good one for a reasonable price). The laser has a pendulum to compensate if it is set on an uneven surface.

 

As for waterlines in general. It is standard practice to mark the waterline and bootstripe higher than the actual waterline so the boat looks like it is floating high in the water. And, since the waterline stripe will naturally appear to rise toward the bow and stern (being farther from the eye) some builders actually paint the line closer to the water at the end points so it appears flat to the water. An example of this is building a strip canoe, in which the strips are bent downward slightly toward the ends so the canoe doesn’t look too “smiley” when viewed on the water.

 

That is my 2 cents. I did not put a waterline stripe on my boat. But every time I take the boat out of the industrial Menominee River I have to wash a waterline stripe off of the boat.
 

 

[Designer]

You cannot go wrong if you follow the waterline method that Alan illustrated for putting on the WL and boot top. It is one of the most critical cosmetic components you will add to the boat, get it wrong and the boat will look sad. The most common mistake that I see is that the boot top is measured up the slope of the hull instead of vertical. On boats that have flare forward at the wl or have a counter stern, it causes the boot top to look narrower at the ends giving the boat a frown rather than a big smile that says "look at me". If you do not get the boot top right, leave it off. On high sided boats it will make the boat look longer and sleeker. 

 

The proportions of the boot top have to be just right and are different for each type of boat and freeboard height. We give the dimensions on our boats as to where it should be. As Steve said do not put it too low . Small boats are almost never in perfect trim and the water is rarely flat. Small ripples will make the water appear higher on the boat than it is. If you put it exactly on the DWL, part of it will usually be underwater. I prefer the scum line to be on the bottom. 

 

I prefer to put the waterline on with the boat upright as there is always some sag or catenary in the string or tape and it could look hogged if it is put on upside down. A tiny bit of rocker in the WL always enhances any boat.

 

I long ago gave up on the string method because you have to do the job twice and best way to put the tape on fair is to pull the tape out a long way as you lay the tape on the hull, why not use the straight edge as a guide? As the illustration shows, put on the stern straight edge on first because you can measure it accurately at both chines to make it truly level to the boat athwartships. Remember to position the straight edge down by the width of the tape. Then position the forward straight edge at the right height forward and make sure that it is in plane with the aft one. It makes sense to do the boot top right after you mark the WL because you have the setup and it will be more accurate than trying to re setup later on.

 

 1" masking tape works great and it is easier to apply if you have help because the tape will slide down especially forward and you do not want that to happen. I put a step ladder or sawhorse etc to anchor the aft end of the tape positioned a foot or two beyond the stern so that I will have enough length as I pull the tape in to the stern. I want the tape pulled out for the whole length of the boat parallel to the boats CL with the lower edge kissing both straight edges and held vertical. I do the bow first and holding the roll out a couple of feet forward of the forward straight edge, start moving the tape inwards with the bottom kissing the straight edge while trying to keep some tension to reduce sag. As soon as tape touches the hull have your helper touch the top edge of the tape and continue touching the as you move inboard. When you go around the chine forward there will be a bridge where the tape will hit the bottom 6" to a foot forward of the chine, this is normal, keep going until you reach the bow. If it looks good you can pat the tape on to the hull pushing the bridge horizontal to keep it fair. While you are concentrating on three things at once it is easy to get the bow wrong by rotating the tape on the vertical axis causing the tape not to be straight. Just pull the tape back out for as far as you need and fix that section. Only after you are happy with the line should you pat the tape down to the hull.

 

Repeat for the stern half and do the other side. If you are going for the boot top follow the directions for setting up the short angled straight edges. 

 

Taping the boot top is identical to the Wl with one exception. For the WL you want the top edge of the tape to touch the hull first. On the boot top you want the bottom  edge of the tape the touch the hull first. This can be accomplished by holding the tape roll horizontally and rotate it as you move it along the straight edge so that it touches the hull with the bottom edge.

 

This sounds more complicated than it is. While a laser is a valid method and appeals to the gearhead, you still have to put on the tape smoothly and when you factor in where to remount the laser in space to get the right curve to the boot top and get it exactly right again for the other side of the boat is harder or less accurate where as the sloped straightedge method is mathematically correct.

 

Do not forget to really press down the tape edge that meets the paint or the paint will bleed under the tape messing up your beautiful work. I usually run the blade of a putty knife along the paint edge of the tape and run my thumb nail into any tape joins that will make a tiny bridge. Or you can spring for 3M's fine line tape.

[AmosSwogger]

I used the B&B technique and it worked very well.  The natural sag of the tape works to your benefit.

 

The B&B plans should have drawings and instructions how to do this.  It is a little confusing reading about it, but easy to do once you get started.

 

[Designer]

Amos,

 

We do, here is that link.

Edited March 21, 2020 by Designer
fix it

[Mark Baumgaertner]

Thanks everyone for your helpful suggestions on how best to strike a waterline on my hull. I think I will go with the B and B tape method.  I plan to flip my boat right side up and mark the waterline then flip it back upside down and paint the bottom.  Hopefully this method will give me the best looking waterline possible.