Clipper's Vera Cruise Build

Clipper's Vera Cruise Build

Sunday, March 20, 2016

Preparing For Bottom Paint

Two tasks remain before I can flip the boat. Building a dolly / rollover structure and painting the bottom of the boat. I have the dolly / rollover structure designed on paper (rough sketches) and will be starting on that soon. However, the first thing that needs to be done is getting the bottom painted. I want the paint to have maximum time to cure before I place the cradle on it and flip the boat over. So the sooner I can get the paint on, the better.

However, before starting on that, I needed to figure out how to determine where the waterline is. The plans show a measured waterline at 18 1/2 inches from a baseline reference which is a specific distance from the bottom of the hull. Since this baseline is in the air above the boat, I had to come up with some way to identify that line, so that I could then measure down from it, the correct distance to the hull, in order to get the correct location for the waterline.

I had two measurements on the plans to work with. One at the bow is 59 inches from the sheer line. The other is 19 inches from the top of the building form (under the boat). I thought about this for some time before I came up with an approach. Here's what I did.

At the transom, I attached a vertical stick to the building form and centered it on the transom. On the wall in by the bow of the boat, I attached another vertical stick. This stick rested on the building form pad under the sheer line at the bow.

On this bow end vertical stick, I determined how far below the sheer line the end of the stick was and measured back up to get a point on the stick where the sheer line is. This is approximately 3 5/8 inches. Then from that point I measured up another 59 inches (per the plans) and struck a mark.

Next, at each frame location, I measured from the top of the build form, down to the floor and wrote down the measurement. This was performed on each frame on each side of the boat. Thankfully, the trouble I went to getting the building form level athwartship (side to side) several years ago paid off here and the measurements were the same on both sides of each frame.

Then, using the jig I created several months ago, for determining the center line of the boat (for the skeg), I placed a cross bar horizontally across the boat. Initially, this was set at an arbitrary distance from the bottom of the boat. I made sure the vertical legs were 90 degrees from horizontal using a level. They were also lined up with the centerline of the frames on each side of the boat.

The next thing was to set up a laser level to adjust the height of the cross bar. I used the 59 inch mark at the bow as a reference and shot the laser. Some of these pictures are poor quality because I was taking them in a dark garage and the camera was very slow in processing the shot. But you can see what I did.

The horizontal cross bar on the jig was adjusted so that its bottom edge lined up with the laser. At the aft vertical stick, I also made a mark where the laser crossed it. Then taking the measurements I made at each frame location, (from the building form to the floor), I measured up from the floor on the outside of the boat the distance back to the top of the building form plus the extra 19 inches to the baseline reference. It came out nearly identical to where the cross bar lower edge was set by the laser. This gave me confidence that I was establishing the baseline correctly. (I have an idea on how to improve this which I will relate in a future post when I finish the application of the blue paint).

Next, using a 90 degree square and a pre-measured stick (measured to 18 1/2 inches), I aligned the square on the cross bar until it just touched the surface of the hull. At that point I made a pencil mark. This entire process of measuring and checking and then marking the hull was repeated on the other side of the hull and at each frame location as well as at the transom.

Finally, to see how it looked, I adjusted the laser level to hit the pencil marks and shot the laser. Again, the photo is poor but you get the idea.

Then I taped off the hull a distance below where this waterline mark was located. This would be the extent of the primer I was applying first. I also taped off the transom.

I had to wait a few days while the weather improved before I could paint. During that time, I was having doubts about the waterline location. It seemed far too low on the boat and I wasn't sure I did everything right. I also wanted the blue bottom to come up the side further (see my drawing at the top of this page).

This morning, the weather had improved enough to paint, so I went out to the garage and started looking over the plans again. It was then that I discovered another measurement that I had previously missed. This measurement added 3 1/2 inches to the designed waterline at the transom and 1 1/2 inches at the bow and represented the painted waterline. Aha!

Since my taped off masking was too high for this, I had to rip of the paper and tape and re-mask. However, I decided that since I was going to have to re-measure the waterline marks after primering the hull, that I would go ahead and primer the hull immediately and leave the measuring for another day. I moved the masking line down a sufficient distance to allow for the additional measurement and re-masked the hull. 

Finally, I opened the primer I purchased and prepared it according to the instructions on the can. The paint is the Supermarine brand from Top Secret Coatings. I went with this brand for several reasons. 

First, I wanted to apply a blue to the bottom of the boat, but because this boat is a trailer boat, I did not want to use anti-fouling bottom paint. Supermarine paint was one of the two brands that stated that their paint was okay for bottom paint. The other brand, Interlux VC Performance was also suitable for this use. However, I wanted to paint the bottom blue and the Interlux brand is only available in white.

I contacted Top Secret Coatings and obtained a color chart which had the colors I was looking for and then purchased a sufficient quantity for the bottom. They also confirmed that the paint could be rolled and tipped in addition to spraying. This was important to me as I did not want to attempt spraying these very nasty two part polyurethane paints and I could not afford to have the hull professionally painted. Having it painted also went against my desire to do as much of the boat myself as possible.

Here is a shot of the hull after the first coat of primer. It rolled on fine. Like any paint, the first coat didn't cover completely, however a second coat will accomplish that. There will be some additional sanding as well. I'll cover the remainder of the painting in the next post.

A final note. I made mention of this already, but this two part polyurethane is extremely nasty and I made sure to wear appropriate safety equipment. It is a very durable paint, but anyone considering using it should take the necessary precautions. That's it for now. Take care.

Click Here To Comment:

  1. Nice work on the waterline, Carl! I'm looking forward to seeing it painted. She's going to be an incredible boat!

    1. Thank Michael,

      It's been a long time coming. This is definitely one of the coolest things I have ever done.


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