No. 70 - December 1986

 

STABILITY

The October 15th 1985 [Volume 11, #20) issue of Practical Sailor has an interesting article headed "Will She Capsize in Heavy Weather? A calculated Answer". The Society of Naval and Marine Architects and the US Yacht Racing Union have come out with what they call a screening formula to determine a boats susceptibility to capsize in heavy weather. A simple formula but you'll need a calculator that does cube roots.

If you want to know how this formula was arrived at and how to use it you'll have to get a copy of that issue. Of interest to Tanzer 22 sailors - how well does the Tanzer 22 do? Practical Sailor calculated the "Screen Value" of 102 boats including the Tanzer 22. The cut off number for offshore racers is 2.0. Boats that rate over 2.0 are considered unsuitable for offshore racing and those below indicate suitability.

Although the Tanzer 22 rates just over the magic figure - at 2.17 - it still does better than any other 22 footer as well as many other larger boats. Like the J's, Merit's, Capri and so on. By and large it is the heavy displacement boats like the Bayfields, Vega 27 and Sabers that rate below 2.0.

 

For those of you unfamiliar with the "Practical Sailor", it is published twice a month, accepts no advertising and devotes its efforts to the testing and evaluating boats and marine equipment. Their address: P.O.Box 971, Farmingdale. NY 11737

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GELCOAT REPAIRS

Gelcoat is the pigmented layer of polyester resin that forms the outer skin of all molded Fiberglas components of your boat. To repair minor scratches, chips and abrasions in this gelcoat, the procedure is:

1. Ideally, all such repairs should be carried out in dry conditions with the air temperature between 65 & 70 degrees F.

2. Thoroughly sand the damaged area with #80 dry sandpaper

3. Clean with acetone. This is highly flammable and usually obtainable from a drug store. It should be used and stored with appropriate caution.

4. Place an appropriate quantity of gel coat on a clean piece of wood or cardboard. Catalyst should then be added. A teaspoonful of gelcoat requires 3-4 drops of catalyst to effect a reasonably rapid cure. Mix together until it is apparent that the gelcoat is thickening.

5. The gelcoat should then be laid into the scratch or chip and smoothed. The surface of the repair should be slightly higher than the surrounding gelcoat. This should be left to cure until it is quite hard. If a clean piece of polyethylene is laid over wet gelcoat to exclude air, this will hasten the curing. In the case of deep scratches, it may be necessary to build up suc­cessive layers of gelcoat. If working on a vertical surface, allow the gelcoat to thicken sufficiently to prevent running before applying.

6. When completely cured, the repaired, raised surface should be sanded initially with #100 dry sandpaper using a sanding block until it is almost level with the surrounding gelcoat.  It should then be sanded with #400 wet or dry sandpaper using plenty of water until it is level. Great care should be taken not to rub away the gelcoat around the repair.

 

7. When all is level, sand again with #600 wet or dry sandpaper and plenty of water.

8. The repaired area should then be buffed with a fine rubbing compound. When buffing, apply considerable pressure. Polishing with a Fiberglas wax such as Boat Armor will produce a high gloss.

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BY THE SEAT OF YOUR PANTS

by John Charters #1000

There are two kinds of navigation, theoretical and practical. And sometimes they don't agree!

Now please-don't misunderstand me. There is no, I repeat, no substitute for knowledge. Marine navigation is extensive and complex. The more theory and background you have, the better navigator you will be. So, please join the Power Squadron - enrol in a correspondence course - read books on navigation - and practice. Then, put to use some of the wrinkles I'm about to discuss.

Navigation IS easy on the kitchen table. The light is good, it is large enough to take the biggest marine chart unfolded and it does not move. Even the most difficult piloting exercise can be easily done. Most of us, though, do not have large kitchen tables on our small sailboats. What was a relatively simple problem at home, becomes a nightmare, as our boat lurches every which way, pencils roll into the bilge, erasers get lost and so on. So how does one simplify things?

Let us start with the navigational aids we need on the boat. When you are tired, wet, cold and scared, it is no time to be fooling around with compass deviation. So, forget all about that "True Virgins Make Dull Company" they teach you. The trick here is to mount your compass where there is no deviation. On most Fiberglas boats this may not be too difficult. The following method is not very scientific but does work surprisingly well. Pick a day when there is no wind nor wave action and tie your boat up to a dock in such a way that its heading or bearing is constant. Now, place your compass at various locations, lubber line properly lined up. Hopefully, most locations will give the same heading. Discard those that don't. Check the accuracy by stepping off the boat, with hand bearing compass line up the forestay or backstay with the center of the mast. This should give you a good cross check. Try a different heading. Several different headings, the more the better. You'll eventually end up with a number of places where the compass will read the same for each heading. If you have a surface mounted compass, your work is over. Mount it at any of those locations, where it is most convenient. If you have a flush mounted compass, beware! Once, having decided on a perfect location, on the cockpit sole of my Tanzer 22- Red Baron III, I cut a four inch hole, lowered the compass into it and picked up a 10 degree error. Before you mount it permanently, you may wish to check it with a few ranges from your chart. Don't forget, measure these ranges using the inner (magnetic] rose on the chart. With a bit of luck you will end up with your compass mounted where there is little or no deviation. Very few of us can steer a course closer than a degree or two anyway, so a minor deviation of a degree can be disregarded.

Believe me, this works! Most of our cruising is on the Maine coast, where fog is often a way of life. As long as I trust my compass, we get where we want to go.

So much for the compass, what is next? Marine charts of the area you expect to cover. For without a chart a compass is not of too much use. Despite their high cost, I still prefer govern­ment charts, to the "Chart Kit" books. These Chart Kits do have the convenience of having suggested courses pre-printed, along with the magnetic heading and distance. However, I find it much easier to work with the proper charts. Most reproductions in the Chart Kit I have use a slightly reduced scale. For example, an original chart with a scale of 1:40,000 is reduced to 1:47,000, and even this slight reduction makes it a little harder to read. The main disadvantage to me is that I find it more difficult to get the overall view of an area, when it is split into three or four pages.

 

One thing I do not do is to buy charts every year! To start with I can't afford to. Secondly, even the latest chart is not always up to date. The Coast Guard in its wisdom is busy re­numbering all its buoys. One year in a fit of conscience, I did buy a new chart of my home cruising area, complete with all the new buoy numbers. Trouble was, the Coast Guard did not get around to changing the numbers on the buoys for almost three months. I pity any stranger trying to match up the chart with the buoys! Fortunately, the Coast Guard has not found a way to change the land and bottom features.

To further complicate things, starting in 1983 the Canadian Buoyage System is being altered to conform to the IALA Maritime Buoyage System, Region B. This is expected to take several years. When it is finally complete, I may break down and buy some new charts. Perhaps the thing to do, is to buy a new Chart Kit every year, to keep one up to date on changes, and hold on to the old charts for plotting.

Whether you have old or new charts, you will need some method of measuring angles and distance. For years I've used a portable drafting board, which use to be available from Weems & Plath. This is a first class item and yet I've never seen another one in use. It is so simple and works so well I cannot for the life of me understand why I've never seen one in a store or a catalogue.

Another handy little gadget I use is a "Sea-rule". Just like an ordinary tape measure except graduated in nautical miles, to the scales of 1:20,000, 1:40,000 and 1:80,000. So much simpler than dividers, just lay the tape along your course line and read the distance directly. And like the Weems & Plath Draftette, an item I've never run across in any store. As a back up I carry a conventional protractor and a pair of dividers.

For many of us, that is all the navigational equipment we'll have. For most situations that is all we'll need. This article is not for those with Loran C, Satnav, etc., anyway,

 

Let's put these tools to work. First and foremost, I do all my plotting before I leave where I am. In the relative peace of a mooring or anchorage, I draw in all my course lines to where I want to go and to where I may have to go. The latter is most im­portant, in an emergency it is so nice to be able to change course without further calculations. I then measure the magnetic direction of each and write that bearing above the course line. I try to pick a spot on the chart where I won't cover up some feature I may wish to read at a later date. If I don't find a spot above the line, I enter it below the line. Despite what the experts say, I am the one that has to read the chart. Even on a clear day, I try to plan my route to take me, wherever possible, from buoy to buoy. This may take me a little way off the direct route to my final destination, but if the fog rolls in, I have a much better idea of where I am. A wise old salt once gave me the following advice on fog sailing. "Nothing' to it, just head for the audibles," I must have looked a little bland, for he went on to explain, "Lay your course out, from bell buoy to bell buoy, measure the distance and angle carefully and trust your compass." I have followed this good advice ever since.

Most authorities require you to enter your speed below the course line. I personally find it far easier to forget about speed and concentrate on distance. Unless one is under power, speed fluctuates so much as to be almost useless. It is far eas­ier to measure distance than to average out speed. Given a choice, install a log, rather than a knot meter.

I have used two different types of logs. The first was the VDO Sumlog. A superb instrument, simple, accurate and in addit­ion to its regular log, has a resettable or trip log. It is also a knot meter. It is entirely mechanical. The impeller drives a flexible cable [just like your car's speedometer] and does not require electrical power to function. Unfortunately it has one bad habit. The impeller attracts weeds like a magnet! Even the smallest weed will render it inoperative. To run properly, the impeller must be located in undisturbed water. Translated that means it will need to be mounted close to your yachts center line and as deep into the water as possible. This makes weed removal awkward or even impossible. If weeds [particularly the floating kind] are not prevalent in your cruising area, by all means consider the Sumlog.

The other type I have used is the electronic paddle wheel type [EMS]. Not nearly as prone to pick up weeds and if one does, one can rotate the paddle wheel 180 degrees in its socket and the weeds should run off. If worst comes to worst, you can remove the paddle from the inside of the boat and clean it off. Mind you, no matter how fast you move, you'll get a couple of quarts of water into the bilge. [These paddle wheels come with a dummy plug you can use, or even easier, just hold the palm of your hand over the socket.] One slight disadvantage, these logs require a 12 volt power supply to operate. However the power requirements are minimal, so should not be a cause for concern. But boy, is the adjustment ever sensitive! Just the slightest turn makes a substantial change in the log.

If you don't have a log, try the following. Every six minutes you will cover one tenth of your speed. You will have to guess your speed, with practice you might become pretty good. On my boat, a comfortable cruising speed under power is five knots. So every six minutes I'll cover a half a mile. Yes, I know there is a nice formula for working out distance, when given speed and time. But by working in six minute increments I can do it in my head, with far less chance of error.

However, I do not keep a DR plot as such. Having drawn all my course line ahead of time, I now merely mark a little cross on the course line, any time I'm reasonably sure of my position, labelled with the time and my log reading. If for any reason I'm sailing a compass course, other than the one shown on my original work, then this new course is also entered beside that little cross. Minor course corrections to allow for drift or leeway are not drawn in, merely noted. Major corrections, of course, are drawn in, along with the new course and distance. Unless absolutely necessary, I avoid any route that takes us directly up wind. Particularly under conditions of limited visibility. When sailing in fog it is vital to steer a straight course, difficult to do when thrashing to windward. Therefore I plan a route enough off the wind, to enable me to steer a compass course. If this is not possible, we motor!

 

You will have noticed, I always refer to magnetic headings and courses. I could never understand why anyone would want to work with True bearings. Not for the kind of coastal navigation we're talking about, anyway.  Like deviation, variation is just one more calculation that can go wrong. So why complicate things? Sailing is complex enough, without having to work back­wards from True bearings, through magnetic to a compass course to steer. Having eliminated compass error, magnetic and compass are now the same.

One of the items not yet discussed is current. Not of concern to many inland sailors, but certainly a factor where you have a tide. For some areas tidal charts are available, but not any of the places I've cruised. So we use lobster buoys. There must be tens of thousands of lobster buoys along the Maine coast. The marine weather forecasts give the time of high and low tide, so I've a pretty good idea when the ebb and flood occur. By observing the current flow by those lobster buoys, I get some idea of not only the set, but how much correction needed. With a little practice, one gets pretty good at it.

This is not intended to be a complete course in coastal navigation. Heaven knows, enough books have been written on the subject. But I do have one last thought. Beware of landfalls! It is so easy to make what you see fit what you want to see. If what you see doesn't match the chart, stop and re-check your work  before you head off to where you hope is where you want to go. At the end of a long passage when you are probably tired it is easy to go wrong. You have been warned!

By the way. I do know how to navigate "by the book". I was trained rather extensively by the R.C.A.F. as a Coastal Command Navigator. So I do have a reasonably complete background in the theory of things. Perhaps it is this background that enables me to do most of my navigation by the seat of my pants.

 

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SMOOTHING OF A ROUGH BOTTOM

by Bill Hansen

 

The Tanzer 22 cast iron keel is great when ramming stray rocks but when blossoms of rust start blooming then the question of boat performance makes us wonder about means of improvement. My keel was worse than most and after the success of the Austral­ian keel experiment I embarked on a couple of experiments of my own. Two items were obvious for improvement. [1] The keel flare was recessed beyond the flush line of the hull and [2] rust patches, particularly on the port side kept coming back with in­creasing vigour.

In the spring of 1985 we tackled the first item by sealing the vertical joint between the keel and hull and filling in the recessed area using Fiberglas body filler. To make sure that a strong joint was made, we slotted the adjoining surface to a depth of about one inch ensuring that the cast iron received most of the grinding. For this we used a small 1/8" abrasive disc fitted in our electric drill. The keel was ground to shiny metal about four inches wide along the tip flare. Immediately after grinding, the surfaces were washed with acetone and color tinted auto body filler firmly pressed into the slot. Then a liberal layer was applied to blend in the mismatches and to feather out the build-up along the keel flare. The body filler set up in about a half hour and then the job was roughed to shape with a curved rasp. For final smoothing mastic was used followed by sanding.

There was some doubt that the fix would stay as we were uncertain if any flexing was taking place along the joints. How­ever, when the boat was pulled out in the fall there were no cracks. We speculate that the body filler may absorb any flex­ing.

Encouraged by last year’s success, we decided to go at item number two. This became a major production and delayed spring launch by about a month, partly due to the size of the job, but primarily due to wet, cold weekends. We had decided that we would cover the keel with epoxy, hoping that by completely sealing it, we would prevent rust from forming again. For maximum bond strength we decided to grind the surfaces down to shiny metal, using an electric hand grinder with a five inch grinding wheel. Although this was easier said than done we were, after much gouging of pits and heavy removal of casting slag on the port side, finally down to sound metal. For the epoxy job we consulted our marine vessel cladding people at International Paint Co., and we followed their recommendations as follows.

Step 1. Immediately after grinding and wiping with a lint free cloth we applied Interlux Prime wash. Two parts: Base #2353 and Accelerator #0354. The Primewash dries in about a half hour and is followed immediately by Step 2.

Step 2. Building up the surfaces with repeated layers of Interlux BarrierKote. This consists of three parts: Base #404, Epoxy Reactor #414 plus a smidge of #2333 Reducing Solvent.

Each coat dries in about 12 hours and in total we applied SIX coats. Between coats one and two, we filled the depressions and pits with International Epoxy Surfacing and Fairing Compound #0417 and #0414. After coat number five we faired the depressions using #0417 and #0414.

Step 3. Anti-fouling paint, Tri-Lux TBTF. We used red at the top and white at the lower portion.

When the boat was pulled out this fall we found no rust.

However the keel was covered with small, water filled blisters each about 1/4" in diameter, but it appears that the entire depth of the blisters involves the anti-fouling and a single layer of BarrierKote only. A variety of opinions as to the cause and cure have been voiced. They all involve sanding out the blisters and applying an epoxy which will not permit water penetration. This will be our keel improvement project for 1987.

"More Smoothing of a Rough Bottom"

 

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