Monthly Archives: October 2015

boatbuilding

The Birth of “Gordalita”

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She was conceived by Richard Woods, and born on a picnic table in our garage.

Richard Woods is the real deal. He is a lifelong designer, sailor and builder who has forgotten more than most of us will ever know of the esoteric world of designing, building and sailing boats.

We needed a smaller lighter tender, that can be hoisted by hand, up onto the new aft platform being installed on the big boat. The idea is to avoid towing the thing around, which presents obvious problems. A decent dingy needs to be able to carry a load, meaning at least three people and their gear, and needs to be light, but must be stable and row comfortably. Richard Woods “Crayfish” design (ours is to be named Gordalita ) seems to fit the bill, as she weighs in at about 50 lbs., and is only 8 ft. long. A little plump no doubt- hence the name, but still quite graceful. I think she is beautemous!

Gordalita will replace Caddywhampus, which has been a delight to row, and a generally good all round workhorse, with a nice figure to boot. When the time comes that you have to row out an anchor to kedge off when on the beach or aground, you really appreciate something that is maneuverable and sturdy . She was Designed by Dave Gerr , as a “nester”, which is a type of boat that is built in two parts that can be unbolted and nested, one piece inside the other, in order to save storage space. In the old days, they used nesting dorys ,which had the same idea. Whalers and cod-fishermen simply stacked one inside the other when stored on the schooner deck. Anyway, Caddywhampus has her place but she is a still bit too large for most of our purposes.

Both tenders are built with the simple “stitch and glue” method, which entails cutting panels for the sides, bottom, and transoms, and lacing them together with wires that are threaded through holes cut along the edges of the seams. As the wires are tightened, the boat comes into shape. Then they are permanently joined by adding epoxy “filets”, which is just a bead of thickened goo, that is coved out with a popsicle stick or a tongue depressor and overlaid with epoxy saturated cloth for reinforcement. This design would be a great starter boat for someone that wanted to get their feet wet. In just a couple of days a complete novice could have a nice functional tender or creek boat. You could also power her up with an electric trolling motor or a 2 hp kicker if you want.

To build one, first, panel dimensions are taken off the plans and drawn out on the plywood (4mm marine, okume ply)
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The plywood panels are cut out and faired so they are exactly the same on each side of the boat
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Panels are then simply wired together at the seams. For this one I used 14 gauge household wire. Zoom in and you can see how the wires are twist tied. I just leave the wires in and epoxy over them. The pigtails are later cut off flush when the boat is flipped over for glassing the outside seams.
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The boat magically takes shape when the wires are tightened at all the seams. Use a temporary brace to get the correct distance across at the gunnels.
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You can use anything for the seats. The lighter the better. I used two inch thick foam from home depot, sandwiched and glued between pieces of 4mm ply leftovers. It is stronger if the panel face-grain runs athwartships. Also, foam gives positive floatation and when located at the seat level- up high, the floatation will tend to keep the boat in a stable posture if she is ever swamped.
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Laminated gunnels are sprung into place and all glued up
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It only takes two or three sessions to get to this point. According to the bathroom scales she weighs 60 lbs. Not too bad, but a couple of pounds more than I had hoped. I think I will skip the paint for now, and see how things go.
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Comfortable to carry
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I was able to lift her up on deck from the dock without problems. Very encouraging. If anyone wants to build one of these let me know. It would be fun, and less expensive, to do a “workshop” and turn out several.

geekery

True Virgins Make Dull Company add Whiskey

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If your boat driver’s license has expired “beyond grace”. That means that in order to renew it, you must go back to square one and re- submit all the paperwork, and re-take the dreaded exam. Some folks say it has gotten harder since I took it last century. Anyway, I have been installing a compass in the boat, which prompted some of the schooling from my earlier years to bubble back up. I guess it would be a good thing to write some of it out for practice, since I will be re-taking the test. One thing I learned at sea school and did not forget:

“True Virgins Make Dull Company add Whiskey”

As Father Guido Sarducci, of Saturday Night Live fame would say, “and that’s all-a you need-a to know about-a that”.

OK, but if you are curious or masochistic, read on.

The nautical chart shows True north and Magnetic North on a thing called the “compass rose” (see above photo). It is a circular pattern with the degrees of a circle and a few other things marked on it. Compass roses are put there to help you figure out which way to steer the boat. They are scattered about on the chart in convenient places for quick reference. First, you have to realize there is a difference between true headings and magnetic headings. You might know one, but need to know the other. The Compass Rose shows both.

The North Pole, is located at the axis of the Earth’s rotation, on top of the world. Its direction is known as True North

The Magnetic North Pole, is a different thing entirely, and is located several hundred miles away from the North Pole. At present it lies somewhere inside the arctic circle. A magnetic compass only points to the magnetic north Pole.

The Variation is the the difference in degrees between True North’s bearing from an observer, say a sea traveler, and what a magnetic compass would point to- the Magnetic North Pole. My brain hurts already.

A Magnetic compass will always point to whichever direction the magnetic pole is in. However, it will only point towards True North, if and only when the North Pole happens to line up with the Magnetic North Pole. It could even point to a southerly direction. For instance, If a traveling person was way up in the arctic, and happened to be exactly between the North Pole and the Magnetic Pole, his magnetic compass would point to the Magnetic Pole- due South! You can see this with an orange or a tennis ball or something, and a couple of pins. The Variation for the travelers location in that rare case would be 180 degrees. To find true north, he would add 180 degrees, (the variation) to his magnetic compass heading.

The Variation of a given area on the chart, is printed on the chart inside the compass rose. It also “varies”, depending on where you happen to be on the Earths surface, in relation to these two poles. To make matters even more complex, the variation changes from year to year, in small increments, because the magnetic north pole and the magnetic field of the earth wanders around. The Magnetic North Pole is at the axis of the earths magnetic field, where it exits the Earth in the Northern Hemisphere, and it is not fixed in one place like the True North Pole (the axis of the earth’s rotation) is. The magnetic pole is affected by the Iron composition of the Earth’s interior, which moves around because the Earth’s core is liquid below and the Earths crust floats on top of it. In geologic history, the magnetic poles have even flipped. That would be a real calamity if that happened again, which it probably will ( and if it does, Virgins will no longer be dull company).

So, for example, the compass rose on your chart might have something printed in it like “Variation 3 deg West, annual increase 5’, 1999’ “ . The annual increase is the amount of change, measured in degrees, based on past history, of the actual physical location on the Earth of the Magnetic North Pole, each year, since 1999. Now, this is where the “add whiskey” comes in.

True Variation Magnetic Deviation Compass add Westerly

So, moving left to right, TVMDC, just like it reads, you always add (+) westerly. If the Variation is 3 deg W, you add that to the true heading to find the magnetic heading, OR, now get this, if you are reading it right to left, i.e. Magnetic to True, you would SUBTRACT the westerly variation, so if your magnetic reading is, say, 000 deg., and you want to know where true North is, then subtracting 3 deg, would give you 357 deg- the bearing of True North.

Stated differently, the “Variation”, is a number that is applied to the True heading to find the magnetic heading, or applied to the magnetic heading to find the true heading. If you know two, you can find the third with this formula. Add westerly variation going left to right, subtract Easterly variation, going left to right. OR subtract westerly variation going right to left, ADD easterly variation going right to left. The annual increase of the Variation mentioned above should also be tallied up and applied to the number. If the annual increase is 5’ when the chart was printed in 1999 and it is the year 2001, then add 10’ (two years). Year 2005, add 30’, etc. Needless to say it gets trickier and more important as you go north because the relative positions to the observer of the two poles (the Variation) can become more and more pronounced as one gets closer to them.

This stuff is often inconsequential in the real world, but it depends on where you are, and how much the variation is, and how accurate you need to be. A half degree (30’), is negligible in most circumstances on a small boat. You couldn’t physically steer with nearly that much accuracy. A steering error of one degree will put you one mile off course after about 57 miles.

Ready for some whiskey?

Not so fast. What about Deviation?

So, Variation then, is a corrective number applied between True North and Magnetic North, that is used to find the bearing of the other. Using the formula above, all you need are two values and you can calculate the other. Just remember to ADD Westerly, or Subtract Easterly, when moving left to right.,or vice-versa moving right to left in the equation.
The Deviation, is the same kind of number, between the Magnetic and the actual Compass bearing, (TVMDC), that is applied to one, to find the value of the other.

Magnetic compasses are affected by all things ferrous, whether it is the earths iron ore deposits or a sack of nuts and bolts left carelessly on the bridge deck, and also by all things electrical, since electrical fields are really the same as magnetic fields. Depending on the amount of Iron on the boat, and electronics, and their proximity to the compass, any of these can have a disastrous effect on the accuracy of the instrument. In a perfect world, without any local interference, a Magnetic Compass would give a bearing from an observer to the Magnetic North Pole. End of story. But every Boat is different. The distribution of iron implements, fasteners, rigging, chain, radios, etc will uniquely affect the compass. So, just as Variation must be applied to compensate for difference between True North and Magnetic North, Deviation must be applied to compensate for the difference between Magnetic North, i.e., where the compass should be pointing- Magnetic-and where it actually is pointing- Compass due to local interference, or stuff on the boat.

A Deviation table is printed up on a Compass Card, by a compass adjuster, who “swings” the instrument, after it is installed, by tweaking the adjustment screws found on the compass. The screws are supposed to allow the adjuster to calibrate for Deviation, which he usually can do, but sometimes he cannot, and so he prints up a card that shows how much to add or subtract from any given heading. Usually it is divided up into the different points of the compass. It might say for instance, N,+2, NNE-1, NE-0, ENE+1, etc. The closest relevant Deviation number, taken from the Compass card, supplied by the compass adjuster, then is also plugged into the equation TVMDC, and the same rules apply- ADD westerly going left to right SUBTRACT westerly going right to left.SUBTRACT easterly going left to right, ADD easterly going right to left.

Cheers.

update Jan 2019

 

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Voices

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Tenderly, he looked into the rushing water, into the transparent green, into the crystal lines of its drawing, so rich in secrets. Bright pearls he saw rising from the deep, quiet bubbles of air floating on the reflecting surface, the blue of the sky being depicted in it. With a thousand eyes, the river looked at him, with green ones, with white ones, with crystal ones, with sky-blue ones. How did he love this water, how did it delight him, how grateful was he to it! In his heart he heard the voice talking, which was newly awaking, and it told him: Love this water! Stay near it! Learn from it! Oh yes, he wanted to learn from it, he wanted to listen to it. He who would understand this water and its secrets, so it seemed to him, would also understand many other things, many secrets, all secrets.
But out of all secrets of the river, he today only saw one, this one touched his soul. He saw: this water ran and ran, incessantly it ran, and was nevertheless always there, was always at all times the same and yet new in every moment! Great be he who would grasp this, understand this! He understood and grasped it not, only felt some idea of it stirring, a distant memory, divine voices.

Siddhartha