Repairs, Tips and Techniques

I noticed my Victory had gelcoat cracks on both side right below the toe rail on the bow and stern. These appear to be caused by improper slinging.

If your sling is not set to hold the sling open on top with a spreader, the weight of the boat will cause the sling to bend to toe rail inward and fracture the gelcoat if not the fiberglass of the hull.

Prepare surface for repainting by washing it three times with hot, soapy water and then giving the entire surface a thorough cleaning with with a solvent based desiliconizer such as “Prep-Sol” to remove wax, oils and silicone residues.

Starting at the bow and working to the stern, use one way strokes and turn the rag often.

This prevents simply moving the residues from one place to another rather than removing them.

Even after sanding these residues can remain on the hull surface. You may actually still have traces of the mold release from your boat’s original manufacture.

In fact, if you are preparing above water line surfaces to be painted, you should use the desiliconizer prior to sanding; otherwise, you may actually end up with residue in the sanding scratches which is then even more difficult to remove. You can’t get the surface too clean!

Gelgoat below the water line at this point is ready to apply the new paint. Any bare metals or fiberglass must be primed with VC No-Sand.

This is an extremely unfriendly material in terms of being breathed so make sure you have plenty of ventilation!

The materials you choose to coat your boat’s bottom with depend partially upon whether or not you will be trailering it.

Many anti-fouling paints have a very short life span out of the water. For this reason, I recommend using a “hard” paint such as Micron CSC Extra.

A barrier coat can be applied to prevent blistering. I used Interlux 3000/3001 which is a two part epoxy paint.

Both types of bottom paint were applied with a 10 inch roller. I used a high quality resin core dacron roller.

Some people apply the paint from bow to stern to make any lines parallel to the flow of water over the hull.

I left my hull with a rough finish, but many people will sand their hulls to a smooth finish. Richard Strasia recommends sanding and polishing to 1500 grit.

Personally, I don’t know if it makes any difference, but I do know that a dimply golf ball travels farther than a smooth one because lower wind resistance, so maybe a dimply finished boat will have lower water resistance for the same reason.

Ed’s Rebuttal to My Dimply Hull Theory

I’ve heard similar speculations along these “lines” before, and I have often wondered myself if this would work. So when I saw your theory I sat down and worked it out. The numbers are probably not exactly right, because I had to make several assumptions (size, shape, and location of the roughness for instance), but the gist of the analysis should hold true.

Here goes nothin’:

Although in principle this would work for what fluid engineers refer to as a “bluff body”, such as a cylinder or a golf ball, it shouldn’t apply to a “streamlined section”, such as a sailboat hull.

Even if you consider the hull a bluff body (and I’ve seen some production hulls that come pretty close), the drag coefficient is only lowered within a certain range of velocities.

For a golf ball in air (a small object in a fluid that isn’t very viscous) the drag coefficient is lowered between about 20 m/s (meters/second) and 80 m/s (about 40 to 160 mph).

For a Victory in normal salt water (a much larger object in a much more viscous fluid; of course, the water in GSL is even more viscous) the drag is only lowered between about 0.01 and 0.04 m/s (about 0.02 kts and 0.08 kts).

More importantly, above 0.04 m/s dimpling will _increase_ the drag coefficient. At about 2 kts the drag coefficient will be about doubled. Of course, this is assuming that the hull is acting as a bluff body, which it really isn’t.

For a streamlined section roughness will _always_ increase the drag coefficient of the hull at all but the very slowest speeds (for a Victory, speeds below about 0.3 kts). Therefore, when dealing with boat hulls, its always prferable to have as smooth a surface as possible.

Note that the roughness of roller or brush marks in paint isn’t exactly what engineers refer to when making these sorts of analyses, it is actually much “smoother”. Therefore, the increase in drag coefficient at higher speeds is probably not as great as my calculations would indicate.

One thought that came to mind is that dimpling the mast might lower its drag coefficient during high winds (i.e., it would act something like a golf ball). Dimpling would lower the drag coefficient of a 15 cm thick mast in air between about 8 kts and about 30 kts. But above 30 kts dimpling would increase the drag (right when one wants as little drag as possible), so I guess that that wouldn’t work either. 🙁

On the other hand, if we wanted to sail really fast boats, we wouldn’t be sailing a 40 year-old design. 🙂

Bottom line question then is this: How much wind velocity is it going to take to get a Victory to maximum theoretical hull speed? I’ve never heard of one planing, and mine never has…

Ed Postulates Further

Much trickier question, at least if you want to figure out the answer from _theory_!

The main problem is that it is very difficult to predict what the coefficient of drag is going to be without doing some empirical work (hence, all of the tank testing that is done by marine architects).It also depends upon such things as the point of sail, the sea conditions, etc. I doubt that it would be possible to get a Victory to really plane (the hull just isn’t the right shape; i.e., no large flat areas).

However, I am able to get my boat well past hull speed without too much trouble.

Here I am “surfing” rather than “planing”, the distinction being that I can go fast enough so that the stern wake in just beyond the stern of the boat, but the boat isn’t really “skipping” across the water.

Theoretical hull speed for a Victory is about 5.2 – 5.3 kts (the over-hanging stern could add almost a half a knot to that), but on several occasions I have had my boat up to 6.8 – 7 kts, according to my GPS. Even if one assumes that the GPS readings were a bit off (due to currents, selective availability, plain old error, etc.), it’s been obvious from the shape and position of the wake that I was well past hull speed.

Without too much chop on the water you should be able to get past hull speed in a 20 kts wind. Saturday the Pteropod was surfing rather nicely, at about 6.5 to 6.8 kts, on a close reach in about 15 to 25 kts of wind.

When we turned downwind for the run back to the marina, she still did 5.5 to 6 kts in bursts, but it was a bit harder to keep her surfing as the wind was starting to die.

If you do get your boat to surf, you can really feel the difference when she settles back into acting like a true displacement hull. It feels like someone put the brakes on for a few seconds, and then the “hole in the water” made by your wake seems much deeper.

Greg Anderson, Convair Sailing Club Race Chief and curator of Victory 21 #647, writes:

The order of finishing in handicap racing is determined by corrected time. The winner is the boat having the earliest corrected time.

Handicap ratings are given in seconds per mile and are multiplied by the race distance to determine a correction that is to be applied to the actual finish time for each boat.

The process for determining race results goes like this:

First, the race committee records the actual time that each boat finishes, then the corrected time for each boat is calculated by using the following equation: corrected time C equals the actual finish time A minus that boat’s rating R multiplied by the handicap distance for the race D.
In algebra:

C = A – R x D

Note that if a boat has a negative number for a rating, that boat’s corrected time will be later than it’s actual finish time because subtracting a negative number is the same as adding a positive number.

Once the race committee has calculated the corrected times for all the entrants, the corrected times are ordered from earliest to latest, and the boat having the earliest time wins.

The process of formulating a handicap rating for a given boat is a bit more nebulous. It is done by a handicapping committee who first decides on the average wind blowing over the area where the racing is to be conducted.

Then the committee decides, hopefully by comparing the polars for the boat in question to the polars for some of the other boats it will be racing against, how much longer, if any, that boat will take to cover a nautical mile than boats whose ratings have already been decided on.

No matter how good of a job the committee does at this, the result is going to be just an educated guess at best.

The committee may adjust the rating later if, over a period of time the boat doesn’t appear to be correcting out like it should relative to the other boats it was racing against.

These adjustments and proposals for them are the subject of discussion, sometimes heated, at future committee meetings.

All lists of PHRF for the Victory 21 I have seen show the rating as 276.