Wednesday, March 28

Product of the Month – VC-17m Extra

By Andrew Spaulding, Crowley’s Yacht Yard, Asst. Production Manger.

Last week I wrote about bottom paint application and I mentioned two of the bottom paint products that we see all the time around the yard at Crowley’s. One of them was VC-17m Extra and this week I am going to take some time to look at it more closely.

There are many types of bottom paint: modified epoxies, ablative, co-polymer, and thin film to name a few. There are multiple biocides: cuprous oxide, cuprous thiocyanate, Econea (a non-metallic organic compound developed by a pharmaceutical company) and others. Various paints have different concentrations of biocide and these days slime fighting additives are in vogue.

How is the discerning boat owner to wade through all of this and figure out what to put on his bottom? The best advice is to ask around. Different paints work better than others in particular areas. So if your dock neighbor uses “XYZ” paint and that paint’s characteristics work for you, by all means, use it. Be sure to seek out boat owners that use their boat the way you use yours. If you want to get to the fish fastest, ask the guys that get there first what they use. For racing sailboats, ask last year’s winner of the big regatta how they prep their bottom for the racing season.

Going fast in sailboats and powerboats starts with a clean, smooth, and fair bottom. This principle works for airplanes, automobiles and boats. Hard, smooth bottom paint is the best way to provide anti-fouling properties with a low-drag surface. Many of the best sailboat racers on Lake Michigan use VC-17m Extra to achieve this goal. Powerboaters don’t be afraid to take this page from the sailors…less drag means fuel savings for the same speed.

There have been several formulations of VC-17 over the years and Interlux’s current formula works great in freshwater and there is anecdotal evidence that it also works in low-growth salt water areas, so don’t worry about having VC-17 on the bottom if you have future plans to ship the boat out to the coast for an important regatta. However, if you do this be sure to have the bottom scrubbed weekly if you leave the boat unattended. Salt water hard shell organisms grow fast particularly in warm water and once their shells harden there is a lot of work to return the bottom to its pristine state.

Slime is the soft growth that occurs near the waterline. VC-17 has Biolux in it which pretty effectively controls slime. The slime along the water line is caused by different organisms than we’ve fought for years on the rest of the bottom, hence the need for new biocides. Since the demands of modern life keep us away from taking our boats out on the lake, waterline slime has become more of an issue. Biolux works ok, but don’t expect it to work wonders if you never take your boat out.

VC-17m Extra also has in it what Interlux is calling a “fluoro micro-additive”. “Fluoro” refers to the chemical prefix of a family of compounds, fluorocarbons, the most famous of which is Teflon, made by DuPont. The fluoro micro-additive works as advertised to reduce friction between the hull and the water.

Of course, even with fluorocarbons on your side, the only way to a smooth, fast, low-drag bottom is preparation. Last week I wrote about masking and taping the bottom for painting (if you missed the article, you can catch up below) and while that is important prepping the surface properly is the only way to get the fastest bottom possible. In the business, we look for a “fair” bottom. By fair, I mean a “streamlined” bottom. Smooth is great but removing high and low spots to make a “fair” surface is the ultimate goal. Making a boat move as fast as possible through the water is an in-depth topic that uses hydrodynamics and is outside of the scope of this article…perhaps we will discuss this further in a future newsletter.

VC-17m Extra uses a thin film technology so when it is applied it goes on the hull of the boat very thin. The paint is self-leveling as well which makes application a little different than typical paints. The paint also dries very quickly which doesn’t help if you are not used to applying it. One of the big benefits of using VC-17m Extra is the reapplication process. As long at the boat had a good powerwash in the fall, it shouldn’t need additional cleaning, but I would give it a wipe with Interlux Special Thinner 216 to remove any dirt and dust that accumulated over the winter. During the wipe down, check the bottom for any loose or flaking paint. Remove any such paint with a scraper or 320 grit sand paper. Smooth the entire area with 320 grit and wipe down the surface with the 216. Now you are ready for paint.

The trick to applying VC-17m Extra well is to roll the paint on quickly, in long strokes from the bottom (center seam of the boat) up to the waterline. Do not roll over the recently applied paint. The solvents in the roller will dissolve the partially dried paint peeling it off the hull. Since the paint evaporates so quickly, it is important to only put a roller’s worth in the pan at a time and make sure that the cover is on the can when not in use.

A typical problem people have applying VC-17m is not applying enough. The thin film technology works so well some owners are not putting enough paint on the boat. Interlux recommends using a short nap (3/16 or 1/4 inch) solvent resistant roller. How much paint to use:  length over all times the beam times 0.85 equals a good approximation of the wetted surface area of the boat in square feet. For VC-17m, make sure that you are applying a full quart over 85 square feet of bottom (other paints have different recommended coverage). For example, a Tartan Ten has a LOA of 33’ and a beam of 9.25’, so 33’ x 9.25’ x 0.85 = 259.4625 sq ft / 85 sq ft per quart = 3.05 quarts. Remember you will need more than this because a certain amount is left on the rollers, brushes, in the paint pan and can, and there will be some left on the drop cloth. Also, the paint dries very quickly so even an experienced applicator can use more on a hot day.

If you want to switch to VC-17m Extra from another bottom paint, the old paint needs to be fully removed. The only exceptions to this case are VC-Offshore and Baltoplate. Other vinyl anti-fouling paints may be ok, I would check with Interlux (great customer service at the toll-free number and online in the forums: to make sure. The best idea if you cannot 100% identify what is on the boat, is to remove it. Trust me; this will be much easier on your psyche than dealing with the mess that will result if you apply VC-17 over an unapproved paint.

In the case that you’ve purchased a new boat and the dealer has left the application of bottom paint up to you there is a procedure to follow. The new hull must be de-waxed. Straight from the factory, there will be traces of mold release wax on the hull that needs removal prior to bottom painting. Or, if the boat was in a showroom or at a boat show the bottom may have been waxed. Either way, start with soap and water and a stiff scrub brush. After a good scrubbing and fresh water rinse, wipe the hull down with Interlux Solvent Wash 202 to remove any residual wax.

Once the hull is de-waxed you will need to sand it to give the paint something to hang onto which brings up an issue. Most boat manufacturers say that sanding the bottom will void the hull warranty. The problem is that without sanding the bottom paint won’t stick. There are primers available that allow you skip the sanding, but in my experience they don’t work that well...even experienced applicators have failures from time to time. Depending on your manufacturer’s hull warranty and your personal feelings regarding hull warranties you may elect to have your dealer apply the bottom paint. If you decide to sand, go with 180 or 220 grit. After sanding, wipe the bottom down with the Solvent Wash 202 and you are ready for paint.

My favorite (and I think best way) to apply bottom paint to a new hull is to use Interlux InterProtect 2000E as a primer coat. This process has lots of its own methodology…keep your eye out for a future newsletter that deals with 2000E or send me a note and we can go over this individually.

As always, let me know if I can help you enjoy your boat more!

1 comment:

Eric said...

Thanks Andrew for the very informative article. I am going to the boat this week to paint the bottom with VC17m and it never hurts to refresh the procedures. I liked the tip of working from the bottom up. Thanks!