Saturday, June 11, 2011

Nesting Dingy Construction

The construction plans were for the CHAMELEON, a design by Danny Greene of Offshore Design Ltd in Bermuda.  (Offshore Design Ltd., PO Box GE 213, St. George's, Bermuda GEBX  Email:
It's a multi-purpose nesting dinghy ... and can be constructed with a sprit sailing rig and/or outriggers and rolling seat  and can be fit with a small outboard.  But the foredeck of  my Fuji 32 Ketch, VALHALLA, would not accomodate  the designed nested length of 5'4" so I did a linear reduction of the plans by 11% to get a nested length of  4'9".  This gave an overall length of 8 1/2 feet.   The sailing rig would also be too much gear to stow onboard so my project was for a basic rowing and motoring version.
The math involved with all of the plan dimensions, which are given in feet-inches-eighths, was easily handled by an Excel spreadsheet conversion of dimensions to metric equivalents, then the application of a percentage reduction.  The 11% reduction gave the desired final dimensions.  Here's a sample of the spreadsheet I used:
Dimension Conversion
Construction is a 'stitch and glue' (or 'tack and tape') project.  The selection of marine grade plywood in the southern Philippines isn't all that great so the best I could come up with was 3/16" thickness instead of the desired 1/4" ply.  So it was planned from the outset that glassing of surfaces inside and out would be required.

The layout and cutout  went smoothly and copper wire was used primarily for holding the pieces together while fillets and glass taping was done.
tack and tape

 The basic hull is shown below after filleting and taping.
 The next stage consisted  of fabricating and installing the bow locker, seats, and aft buoyancy tanks.

It was now time to separate the hulls by cutting between the mating bulkheads.

Fabrication continued with the installation of skegs, corner fillets and reinforcing for the outboard and rowlocks. Two coats of epoxy primer were sprayed using SCUBA tanks in lieu of an air compressor.
The nested package ready for launching.
A companion project was to fabricate a pair of 7 foot oars after the design of Pete Culler.  Here's the result:
Not able to wait for final painting I gave GECKO a trial row.
Though she rowed like a dream I discovered that the reduced freeboard placed the rowlocks too low ... my hands would touch my legs on the rowing downstroke.   The low freeboard also gave me some stability concerns ... something that Danny Greene cautioned against when I told him of my approach to this project.
The solution was to add some freeboard by adding a higher gunwale.  New mounts for the rowlocks gave the desired increased height.

With the gunwale completed it was time to determine the exact waterline before painting the outside.  An in-the-water test was done with some loading to simulate "normal" conditions.  The resulting mark from the dirty water in the boatyard was easily visible on the primed surface.


The 'topsides' were painted to match the topsides on VALHALLA and a vinyl rub rail affixed around the gunwale.  A coat of antifouling on the bottom completed the project.
Oh !  you wanted to see the finished product?  Then you must  click here.

Friday, June 10, 2011

Swim Ladder

The swim ladder on VALHALLA is a Platform Mount Ladder from West Marine (Model # 518985), modified to fit the curvature of the vessel sides.  The ladder is strong enough and the bottom step deep enough in the water for an easy climb while coming aboard.

Two pairs of mounting brackets (Model #519355) are installed to allow a 'quick connect/disconnect' feature.

The bottom two mounting brackets are bolted through the hull with backing plates and without modification.  Access to the nuts inside the hull was surprisingly easy through the furniture.

The top two mounting brackets were modified to give clearance on the inboard side for the bottom bolts which pass through the toe rail just above the deck.  In retrospect, the top bolt holes did not need modification.  The bolt heads were ground off to fit next to the raised portion of the mounting bracket.  A backing plate was also installed on each top bracket as shown below.

The modification of the top section required cutting off the lower stand offs and welding them back in place at the correct angle to fit the hull curvature.

This shows the fully extended ladder with a new lower section, which was a disappointment.
After four months of use the original lower section of the ladder developed, on one side, corrosion cracks at the point where it was bent 90 degrees (the small radius deformed the tubing at these bends).  After one year it was rusted through and required replacement.  That fabrication, done in the Philippines, was without bends (no bending machine) but lasted only two years due to poor welding.  It was replaced in Malaysia with a well constructed item using prefabricated 90 degree bends and TIG welding.
For simplicity the original flattened tubing and plastic rungs were eliminated on the lower section with no great loss of comfort when climbing.

When not in use the lower section folds up neatly.  A retaining clip on the upper section was discarded after it suffered UV deterioration (not surprisingly, replacements are available from West Marine.  Do you suppose they know?).  Instead, a small line is now used to secure it in place when required.

Thursday, June 9, 2011

Cruising with LPG / Propane

Here is sv Valhalla's solution to the LPG problem that so many cruisers find around the world. LPG is dangerous and you shouldn't undertake this if you have any doubts as to safety. Please read carefully and consult with others who have done this before, before undertaking the LPG transfer.

One of the problems cruising in different parts of the world is the difference in fittings for liquid petroleum gas (LPG) in either propane or butane tanks.
In the USA the standard fitting is POL (reverse thread).
In Europe and Asia there are different connectors and fittings.
On VALHALLA we find it necessary to decant the compressed liquid (propane or butane) from a 'local' tank into our vessel tanks which will fit in the custom spaces for use and storage. 
In Micronesia we found compatible fittings but only large local tanks so decanting was necessary there as well.  Prior to leaving Hawaii I had a POL to POL transfer hose fabricated at a propane supply store.
In Asia we again find large tanks (50kg) with the POL fitting ... much too large for use on the boat.  The smaller (12-14kg) tanks use a snap-on fitting, either separate or combined with a tank regulator. For these tanks a transfer hose has been fabricated as shown.  The local tank fitting (without a regulator) and shut off valve are normally available at hardware or stove stores along with reinforced hose.  I originally used clear reinforced plastic hose, as shown in the photo, but found that the gas caused the hose to become brittle.  I now use rubber hose designed for auto air conditioning.  The shut off valve is handy since as soon as the local fitting is attached to the tank the gas begins to flow.  The male POL fitting was fabricated at a machine shop using my POL-POL transfer hose fitting as a sample.
The method of transfer is to invert and elevate the local tank and have it warmed by the sun.  The vessel tank is kept in the shade and covered with a wet towel (not shown for clarity).  The temperature differential creates a pressure differential which assists the liquid transfer.
The vessel tank is hung from a hand scale to measure the weight as it is being filled.  I weighed a tank that was filled at a commercial plant and use that as the target weight.  It is important to NOT OVERFILL the tank.  The correct amount is 80% of the volume of the tank to account for expansion from a cold to hot tank.
As the tank is being filled I open the relief valve to reduce the pressure in the vessel tank and further assist in filling.  A clear vapor will be exhausted.  I do this periodically during filling and, as the tank weight approaches the target weight I look for it to 'spit' a stream of white liquid.  At this point I consider the tank to be full and close all valves.
A safety consideration in this operation is the fact that butane and propane are heavier than air and will flow 'downhill'.  Close all openings into the interior of the boat (port lights, ventilators, hatches, companionway boards, etc.) and ensure your gas detector is functioning.

Wednesday, June 8, 2011

Alternator Controller

The Balmar MC-612 is a fully automatic alternator regulator that has served the svVALHALLA well for many years.  There are times, however, when I find it desirable to either turn the alternator off or reduce the output power, in this case to reduce wear on bearings and belts when powering for extended periods and do not need a quick initial charge.  Typically, when weighing anchor with the windlass, its one horsepower motor will draw the batteries down considerably and this puts a large load on the engine while maneuvering to get underway.  This is an ideal time to reduce the charging load.
The regulator uses a field wire (brown) to energize the alternator when connected to battery voltage.  A switch in this wire controls when the alternator is operating.
The alternator temperature sensor (an optional item) switches the regulator into the 'small engine' mode when heating causes the temperature sensor to short out and reduces alternator output by approximately 50%.  Manually shorting this input simulates the overheated condition regardless of whether a sensor is connected or not.
This is the schematic of the project.

This project involved wiring two switches, two LEDs and two resistors into a small plastic box.
  I used small switches which required a 6 mm hole for the switch and a 2 mm hole for the retaining washer.

The LEDs require a 5 mm hole for a snug fit.

Before installing wiring the box was assembled and drilled for wiring entry.

The underside of the box is shown here.  Not yet connected are the field wires which go to the switch in the upper left hand corner and which come through the upper access hole.

With completion of the wiring I tested the switches using a direct connection to the temperature sensor terminals.
This was to ensure that there was no interference from the sensor.

Satisfied that things were working properly I completed the wiring with connectors to permit double connection to the temperature sensor terminals.

Now to find a label maker . . .!

Tuesday, June 7, 2011

Anchor Lights

The sailing vessel Valhalla has some interesting ideas for those anchor lights we like to put lower down on our sail boats. He writes...
VALHALLA, like most cruising boats, has an anchor light at the top of the main mast.  Though in full compliance with the Colregs, it is NOT the best situation for two important reasons:

1.  The bulb consumes 20 watts which, at 12 VDC, draws 1.67 amps ... an excessive amount of power.
2.  The light is too high for easy recognition by small boats moving around an anchorage, and can be mistaken for a star or planet due to the elevation!
There are now low powered LED navigation lights on the market which range in price from US$ 100-250.  A bit pricey for the budget. 
My first solution was to use a utility light (Davis Utility Mega-Light)  hung on the flag halyard, below the spreaders. This light has a photocell switch and, with the most efficient of two supplied bulbs, reduced the amperage draw to 0.11 amps.  A further reduction in power was to build a new bulb using the base of a burned out one.  Four white LED's (which have a drop of 3 volts at 20 ma) were soldered in series and positioned to face 90 degrees apart.  The leads were secured inside the bulb with a small amount of epoxy putty.  The current of 0.02 amps was negligible while giving sufficient brightness at a cost of US$0.50.

The Davis utility lights have a short (6 -9 months) life span due to UV deterioration of the plastic housing which soon cracks and allows water to flood the unit and short out the circuitry.  That is unless the photo cell circuit quits working first, which also happens.
To build my own, I salvaged the fresnel lens from the failed unit, built a photo cell circuit (again with 4 white LEDs) and, with a plastic cover (it is the retaining knob for a household fan!), used silicone to seal everything.
So far it has outlasted the Davis lights ($39.99)!

While cruising in Malaysian waters we noticed that numerous fishing boats used flashing lights ... of many different colors.  Their nets were sometimes marked with flashing lights as well, though not often enough for our satisfaction.  Browsing the fishing supply stores we found numerous models of small flashing lights, both incandescent, strobe, and LED.  These lights are powered with either one or two flashlight batteries and incorporate a photocell switch.  After trying several brands I found one that has blue LEDs, runs on two batteries and last about three weeks.  The price we paid was RM18 (US$ 4.75). 
Here's one undergoing 'trials' along with my 'home brew' white anchor light.

The markings on this light are:
Yang Cheng
Made in China

The colored dot indicates the light color, in this case blue.

To avoid the use of flashlight batteries I constructed a simple voltage reducing circuit (one IC 7805 and three diodes 1N4001) to reduce 12 VDC to 3.2 VDC.  The circuit board and components fit inside the light housing with a power lead to the boat's batteries.  The low power consumption obviates the need for a heat sink.

The blue flashing light is now mounted just beneath the white one.  If we were to make an addition to the navigation light memory phrases, such as 'red over red the captain is dead' for a vessel not under command, ours would be 'blue under white that's our boat all right'!  Very useful after an evening ashore while finding your own boat in a dark and crowded anchorage !!!!!

Monday, June 6, 2011

Smooth out those transmission vibrations

The yacht Valhalla  has this installation of an anti vibration device. The picture say's it all.
aquadrive™  Installation  

Through the help of a friend I obtained an aquadrive that was in the estate of a yacht owner who died before the installation was done.  Follow the link for a complete description of this system but basically it is a double CV (universal) joint unit located between the engine transmission and a thrust bulkhead further connected to the propeller shaft.  The thrust bulkhead takes the force of the propeller instead of this force being transmitted to the engine mounts.
This is the completed installation:

Motor mounts: Soft motor mounts from Aquadrive provide freedom for the engine to vibrate without transmitting the vibration (and noise) to the vessel. The ones provided by Drivelines NW are exactly one-half the height of the Yanmar mounts for my 3GM30F engine. I had 'risers' fabricated locally to fill the space, which also allowed me to use the bolt hole spacings for the Yanmar mounts which are slightly longer than the Aquadrive mounts.

Adapter Plate: The one provided with the system I obtained was for another engine. I had an adapter place fabricated locally.

Thrust Bulkhead: This was the most critical piece of engineering and installation. The bulkhead must be installed a critical distance  behind the adapter plate, the rubber bushings between the aquadrive unit and the bulkhead must be at 15 mm under compression, and the thrust bearing (after end of the unit) must be in perfect alignment with the shaft going through the water (cutlass) bearing. The scarred area on the hull under the shaft is where a temporary bulkhead was installed to hold the shaft in alignment while the thrust bulkhead was fabricated and installed. The thrust bulkhead was fabricated from 1/2" King Starboard with 8 layers of fiberglass on each side for a total thickness of 3/4 ". As an aside, I had the help of a 5 foot tall Filipino fiberglass technician for this installation ... I COULD NOT have done it myself in the small space under the cockpit.

Shaft: My old shaft was pitted and in poor condition but I was lucky to obtain a used one from a friend who had upgraded from a 1 1/4" shaft to a 2" shaft. Although it was 35 years old it was in excellent condition and long enough to permit machining the ends to fit the coupling and the Autostream feathering propeller.

Permanent Shaft Seal (PSS): I opted to install a new PSS which is normally for a high speed vessel since it has a feed for water to be injected, in my case from the salt water drain of the heat exchanger. This ensures lubrication of the water bearing.

Sea trials have not been conducted other than moving from a nearby boatyard to our berth at the Subic Bay Yacht Club.  When interior varnishing is completed we will then have a chance to check out the expected improvements.