SVMOP:

SVMOP:Tech: Hydrography pages complete, but can be beautified

Sun, 02 Nov 2008 11:30:00 EDT

I have written and uploaded my discussion of the hydrographic work that I did with Mother of Perl, and the tools that I used to do that work. The source code is part of the page set. I still need to document my tide work and my data acquisition software. The URL is http://www.maperl.com/Hydrography

SVMOP:Tech: Hydrography Pages

Tue, 21 Oct 2008 00:37:00 EDT

The pages describing hydrographic work on Mother of Perl are progressing, slowly.

SVMOP:Tech: A shell script to post blog file

Mon, 13 Oct 2008 16:29:00 EDT

Here is a little script to facilitate posting my blogs:

#!/bin/bash
file="$1"
pwd=`pwd`
category=`echo $pwd | sed 's/^.*\///'`
destbase="Wroninhouse@copper.mv.com:Journal/"
echo -n "Category? [$category] "
read response
if [ ${#response} -gt 0 ]
	then	command="scp $file $destbase$response"
	else	command="scp $file $destbase$category"
fi
exec $command

SVMOP:Sail: The Broken Sails Were Trailing in the Angry Sea

Mon, 13 Oct 2008 07:01:00 EDT

The trip from Virgin Gorda, BVIs to Portsmouth, New Hampshire wasn't without a bit of adventure. We were, after all, doing this at the begining of huricane season, first of August, 2008.

There were three of us: Capt. Ben (me), Bill T., and Sally K. The crew had sailed on Mother of Perl before; Sally for nearly a month, island hopping from Tortola, BVI down to St. Lucia with extended stay in Dominica. We all knew what is was like to live and sail this rugged boat.

The plan was to leave the mooring in Trellis Bay, Beef Island/Tortola the morning after everyone was in the BVIs, motor upwind to Spanish Town, Virgin Gorda (about one hour), fuel and provision, then the next day depart due north to Bermuda, provided that there were no storms threatening. We expected the passage to take about a week, which it did. We ran with 4-hour watches. The captain was on call 24-hours, so he had the morning and evening watches.

We started out with a good strong wind on the starboard quarter, but it settled down by the end of the first day. We motorsailed at night and sometimes during the day when there wasn't enough wind to get us going four knots. The wind and seas picked up the day before we arrived in Bermuda, but the timing for a direct approach would have brought us in near midnight, so we tacked far to the northeast and back to the northwest to make our arrival at daybreak.

Radio Bermuda, the coast guard VHF radio station, was extremely helpful getting us in through the Town Cut and to the Customs and Immigration dock. The formalities took only a few minutes and we moved to the town dock where we spent that night. During the next day, we shopped and did laundery. The next day, we fueled up and filled our water tanks and were underway before the cruise ships had crowded the harbor.

As with the exit from the BVIs, we left Bermuda with a good stiff breeze of 20 knots, but it died off to less than ten knots by the end of the first day. We had barely gotten 150 miles north of Bermuda by nightfall of the second. The forecast had our hopes up, however: "15 to 20 knots from the southwest." Sure enough, the wind very gradually rose to 15 knots as the day came to an end. By 2300 (11PM), we were moving along well with jib, main, and mizzen. Because it was night time sailing, we took the precaution of having two reefs in th main. My watch ended at 2300, so I went to bed. (We had shifted the watches when we left Bermuda.)

I woke at 0300 and immediately noticed the boat motion felt like we were surfing. In fact, we were. The boat speed was over ten knots. (The maximum displacement speed is nine knots.) Within minutes, there was a load crack followed by deafening flapping of sail. We started the engine as an emergency response. Bill T., who was on watch, and I made our way up on deck and found that the clew of jib had ripped away. We dropped the jib (no roller furling made this easy) and gatthered the sail onto deck. The wind was more than thirty knots and gusting to forty.

Without the jib, the sail plan was severely out of balance with power shifted aft. But the wind was still over the quarter so the consequence was not significant until the wind shifted. Nonetheless, we atempted to drop the mizzen, a foolish plan considering the strength of the wind. It jammed in the shrouds. We could neither drop it nor bring it back up, and had to leave it billowing in the shrouds.

Since the jib had blown out, we were motorsailing and doing 1-hour watches, the three of us. Around 0600, we heard another crack. This time it was the rivits holding the pad-eye for the mainsails second reef. The reef was blown and this sail was bilowing in its shrouds. The wind was in the forties gusting into the fifties, too dangerous on deck to do any work to prevent any more damage to the sails. It was more important to stay safe below, out of the wind and now heavy seas.

Within a few hours, the wind had clocked around to northwest, our rhumb line course. The wind had dropped back into the thirties, still enough to build seas, now there were 15 foot seas from stern, 8 foot seas on the bow, and an occasional wave directly on the beam. The later was the most dangerous. The first danger is roll, but Mother of Perl is so beamy and has so much ballast in her full keel, that she rolled a maximum of 45 degrees, and usually no more than twenty degrees. The second danger comes from when she isn't rolled when the beam sea hits. The majority of the hull is vertical and flat. When a sea hits this surface, it is like a seawall, the water shoots straight up and comes crashing down on deck, covering the deck with half a foot of green water for the few moments before it drains away. The dorads (vents) are designed for only two inches of water. The result is water in through the vent pipes of the dorads, not much, but enough to make a mess. One hatch, as well, had trouble holding back that much water. When got around to cleaning up after the storm, it didn't amount to more than ten gallons, total.

By noon, the winds had subsided to twenty-five knots, and the seas had become more regular. But before that happened, the vessel motion was so choatic the the GPS couldn't give us a course or fix, nor could the autopilot steer. Our velocity was down to one knot, at best. There were times when we actually were going backwards in relation to the bottom, but forwards through the seas. We were steering by hand and by magnetic compass. Thank goodness for dampening the compass. In reality, the seas governed our course more than the compass.

Once the autopilot and GPS had reestablished themselves, Sally K. and I went on deck to try to tidey things up and assest the damage while Bill T. stood watch and kept us from being washed away by seas. Using tethers on our harnesses to keep us secured, we relashed the jib, which had come loose, secured the main to the boom, and did the same with the mizzen, which had torn across near the top and was trailing along with various sheets in the seas by the boat. We also discovered that the dinghy had been destoyed and was hanging by a single fall from the davits. The outboard had smashed against the stern of the boat in the process. They were of little salvage value and dangerous to recover, so I cut the dinghy free to drift off to the Azores or Africa.

There had been considerable damage to sails, and the loss of the dinghy left us without any emergency liferaft as well as just being financially a pain, but we and Mother of Perl were in fine shape, save a few bruises. She proved herself as an incredibly strong and safe boat. Now the question was how we were going to get home. We were 200 miles or more from Bermuda and 400 miles from the nearest port in the USA. All we had was our little 80hp diesel engine.

By 1600, the wind was down to less than twenty and seas were flattening out, relatively speaking, so we returned to our regular four hour watches. I sounded the fuel tanks and found we had about 500 liters (150 gallons) left. At 2000 RPM, the engine uses roughly 5 liters and pushes the boat 5 nautical miles in ideal wind and seas. That works out to one liter per nautical mile. If we could avoid any more adverse wind and seas, we should have plenty of fuel to motor to our destination of Portsmouth, NH. If not, Nantucket and Cape Cod were closer. We would at least be within radio range of fishing boats when we ran out. To be sure that we got the most distance from the fuel that we had, we kept the engine at 1800 RPM.

For the next two days, the wind was less than ten knots, on the nose, but light, and the ocean flattened out. We relaxed, ate and slept well again, and remained patient about our arrival, despite a certain urgency for Bill T. to get back in time for an important real estate meeting on his new house. I sounded the tanks each day. We were getting at least a nautical mile per liter.

On the afternoon of the third day, we had reached George's Bank, a prime commercial fishing ground. We wouldn't be able to pull in to Nantucket or a Cape Cod port during the day, but we had plenty of fuel. We were able to call the US Coast Guard on the radio and pass on the information that we would be a day late in arrival. They would call our families.

The next day brought us close enough to Cape Ann that our cell phones worked and we called and confirmed our arrival for that afternoon. We didn't mention what condition the sails were in. We arrived at the New Castle pier at 1600 and were greeted by our wives. Sally would have to wait another day for her sweetheart to arrive from Oregon, a big surprise visit.

Mother of Perl now sits in Portsmouth. Her sails are at the sailmaker. The teak bowsprit decking which had been destroyed by the waves is replaced with fiberglass reinforced plastic grating. She has her own mooring thanks to the purchase of share by a local mariner with a seldom used mooring.

All is well, but none of us are quite ready to go out in the deep blue sea.

SVMOP:VSTP: Lessons learned (so far) from this project

Fri, 10 Oct 2008 07:13:00 EDT

Since I still am very green as a Python programmer and still think in Perl, I have been learned from pain the differences in concept. For one, the concept and implementation of global variables is different.

In Perl, the concept is that the language is more likely to be used for utilities rather than applications, therefore everythink is global if not otherwise declared. Global to the namespace (module/package) that is. Python, however, assumes everything is private unless otherwise declared. This brings up the question of when is it appropriate to use globals in Python.

I asked Kurt, whom I regard as a seasoned Python programmer, when he used globals. His answer: "never!" Where do I use globals? When variables (usually application configuration settings and things like file pointers/objects) are used in many of the subroutines/functions. Rather than continually passing these variables as argument to the call, I just make them global.

Here is another wierdness abouth Python globals: the calling function declares them as global rather than the block enclosing the functions (as in Perl when they are explicitly declared global).

I'll get used to it.

Other things that take some getting used to are split, join, and string formatting. They are just enough different that I am having to correct myself often.

I all, I really like Python for application development. I still want to use Perl for utility programming, but I know I won't learn Python unless I use it for utilities as well as applications. It is not likely I will completely forget Perl in the process, at least not until so few of my brain neurons are firing that it does make any difference.

SVMOP:VSTP: rsync - doesn't seem to work on the web server

Wed, 08 Oct 2008 06:28:00 EDT

This is a test to see if rsync works on mv.com. I don't think it is installed, so I'm hoping that the rsh/rcp method works. Let's see. Nope.. but rcp/scp does work. So I'll make a little script or alias to shorten the call.

SVMOP:VSTP: SQLite experiences

Tue, 07 Oct 2008 23:03:00 EDT

Dropping down to pysqlite from SQLalchemy wasn't too difficult. But the last few details took an experienced pysqlite programmer (Kurt Schwehr) to get things working. The issues were:

Be sure that there is a connection.commit() on a regular basis
Be sure that proper parameter format is used in the INSERT

There are five different ways of specifying parameters. I still need to find the one that works the best for me. Some do automatic value casting.

SVMOP:VSTP: RDBMS and SQL -- the next phase for ShipTracking

Mon, 06 Oct 2008 22:09:00 EDT

The VOS (Voluntary Observation Ship) Tracking project has taken on a new phase. The data will be read into a relational database as well as the original XML format. For the application user, there is little change. The major difference is the specification for the database fields. Compare the SQL output specification to the XML specification:

 <?xml version='1.0' encoding='iso-8859-1'?>
 <config>

  <inputDescr filetype="ASCII">
    <field name="year"		start="1"   	stop="4" 	type="INT"/>
    <field name="month"		start="5"   	stop="6" 	type="INT"/>
    <field name="day"		start="7"   	stop="8" 	type="INT"/>
    <field name="hour"		start="9"   	stop="12" 	type="FLOAT"/>
    <field name="lat"		start="13"  	stop="17" 	type="FLOAT"/>
    <field name="lon"		start="18"   	stop="23" 	type="FLOAT"/>
    <field name="callSign"	start="35"   	stop="44" 	type="STR"/>
  </inputDescr>

  <outputDescr filetype="XML" >
    <field name="year" format="%d" value="year" />
    <field name="month" format="%d" value="month" />
    <field name="day" format="%d" value="day" />
    <field name="hour" format="%0.4d" value="hour" />
    <field name="hrs" format="%.2f" value="float(int( hour /100) + ( hour /100.00 - int( hour /100))/.6)" />
    <field name="latitude" format="%0.2f" value="lat / 100" />
    <field name="longitude" format="%0.2f" value="lon / 100" />
    <field name="callSign" format="%s" value="trim( callSign )" />
  </outputDescr>

  <outputDescr filetype="SQL">
    <field name="sqltime" datatype="TEXT" format="%s" 
	   value = "SQLtimeStr(year,month,day,0)" />
    <field name="latitude" datatype="REAL" format="%0.2f" 
	   value="lat / 100" />
    <field name="longitude" datatype="REAL" format="%0.2f" 
	   value="lon / 100" />
    <field name="wkt_geographic" datatype="TEXT" format="%s"
	   value="wkt(lat,lon)" />
    <field name="callSign" datatype="TEXT" 
	   format="%s" value="trim( callSign )" />
  </outputDescr>

 </config>

Internally, there are some serious additions for the database specification parsing and record insertion. However, the hard part was deciding which Python modules to use and non use. After looking at SQLalchemy, we have decided to keep it simple and just use pysqlite. (SQLite is the database engine we have picked.)

SVMOP:Sail: Keeping busy

Tue, 22 Jan 2008 07:41:00 EDT

Ah, life on a boat, even in the Caribbean, is a lot of work when you have to do it all and pay for it all.

I have a worklist, some fifteen or more items long. Some of the items are not critical, such as: install the remote microphone for the VHF radio. Others are very critical; for example, stop the leak from the main engine sea water pump so that it doesn't fill the bilge to alarming levels every time I run the engine for more than an hour. Or, how about, the fact that the dinghy is coming apart at the seams, or the forestay (for the jib and a major structural elment of the mast is untwisted at mast top threatening to part.

As Kristen, my stepdaughter, is so good at reminding me: take a deep breath. Put order and priorities to what can be done when and what it immediately necessary (water in bilge). And.. don't wince when you have to pay the bills in boat units. One boat unit is $1000 USD.

SVMOP:Sail: St. Lucia to Trellis Bay, Tortola, BVI

Tue, 22 Jan 2008 07:39:00 EDT

Thanks to the hard work of my crew, Kristen and Pete,

we were able to launch Mother of Perl in St. Lucia in less than a week. Two days later, we had our sails on, provisioned and under way for 350 nm passage to Tortola.</p>

The first day was great. Seventeen knots of wind on the beam. We able to get our hoped for 7 knots velocity made good. If we could keep this up, we would reach the Virgin Islands in 48 hours, 9 AM on Frisday. But that wasn't to be. The wind dropped to five knots in the middle of the night. We began motor-sailing slowly, assuming that we arrive in

three days instead of two.

It qas nor meant to be. On the second afteroon, some 80 miles from the narrow reef bordered passage into the BVI's, the wind completely died and cross seas built. The seas were expected at the northern most Windwards, but the trade winds should have been 15 or 20, with sails preventing rolling.

We have a chartplotter and decent radar. I knew where we were going (Round Rock Passage) and could do visuals using the lights of the islands beyond to be sure we had Round Rock on our right. Rather than wallow in rough seas (and incure both the fatigue and stress on the rigging), we pushed the throttle up to 80% and drove on to island. We approached Round Rock at 1AM (0100hrs). Time drop all the sails. But no, the roller reefing jib was jammed. As we were fast approaching the passage, Pete braved it on the bowsprit in the dark, and unfouled the roller sheet.

Since we had to check in the BVIs the next morning we headed for mooring field outside Spanish Town. After making quite a din motoring around and shouting out to a late night dinghy rider, we discovered there were no moorings available. So on to Trellis Bay, about an hour away. No problem now that we were inside the protected waters of the BVIs. In fact, there were several free moorings. It was a familiar place. Bruce and Carole bought a mooring here for Mother of Perl. It was not to be trusted without daylight inspection, but we took an empty Moor Secure mooring right next to it. Next morning, the private mooring was brought back into service and we had moved to our old spot. Halleuia!