Monday, April 20, 2015

Galley Work

Back in October, I re-designed the curtain tracks on two of our aft ports in order to allow them to open more completely.  The results were so nice and professional looking that the remaining six ports just begged to be upgraded too.  So I ordered more curtain track from Sailrite.

This last weekend I got around to making the installations.  But because there were six to do, a little manufacturing engineering came into play. 


First, at home I cut and trimmed the track with my trusty hacksaw and vice. Then I set up a work station at the galley sink for drilling - the sink traps the drill swarf and keeps it off the floor where it would damage the finish. Above, you can see that I have marked where the holes go on the tracks and am busy drilling them with a 5/32" bit.

After finishing the manufacture of the tracks, the work fell naturally (that is, unplanned...) into four workstations, each with its own dedicated tools:
  • Station 1:  At the current port.  Tools here were a #2 Phillips screwdriver, a 3/8" box wrench, a small flat blade screwdriver, and a small #1 Phillips screwdriver.
  • Station 2:  The galley sink. Tools here were the drill, water and a sponge
  • Station 3:  The saloon table.  Tools here were Meguires plastic cleaner, Meguires plastic polish, and some rags
  • Station 4:  The saloon settee.  Tools here were a #2 Phillips screwdriver and a 5/16" nut driver.
And so the work went like this...
  • At Station 1:
    • Remove the existing curtain track and curtains from the rusty spring clips and set aside
    • Using the #2 Phillips and the 3/8" wrench, remove the nuts and screws holding the port hinges together.
    • Remove the port lens.
  • At Station 2:
    • Carefully wash the port lens using water and the sponge.
    • Transfer the hole locations from the track to the port lens and mark with a Sharpie.
    • Drill two 5/32" holes.
  • At Station 3:
    • Apply polish to the inside of the lens and turn it over
    • Apply cleaner to the outside and rub vigorously to remove the oxidized lexan.
    • Remove the cleaner with a rag and apply polish to the outside of the lens
    • Buff the outside of the lens.
    • Buff the inside of the lens.
  • At Station 4:
    • Now that the lens is clean, it won't dirty the settee cushion, and it needs protection.  Working on the settee is perfect.  Install the track to the lens with two 6-32 screws and nylock nuts, using the #2 Phillips and the nut driver.
  • Back at Station 1:
    • Insert the lens hinge plates into the hinge plates on the port frame.  
    • Use the small Phillips screwdriver to align the holes.  It is perfect for this - the shaft is exactly the right diameter and the tapered tip allows easier alignment.  I struggled mightily with this step before I stumbled across the use of the screwdriver.
    • Insert the screws into the hinges and add the nuts.
    • Using the small flat blade screwdriver, remove the stop screws from the ends of the old track.
    • Remove the curtains from the old track.
    • Install the curtains into the new track.
    • Install the stop screws in the ends of the new track.

And then move on to the next port...

Tho having these four stations pretty much occupied the whole boat during the work, it completely eliminated all movement of tools except for the small handful used at Station 1.  For me this is a huge advantage, since otherwise I am always looking for one tool or another.

It took all afternoon, but only one beer.




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Monday, April 13, 2015

I wonder if you knew

Say you have a boat, and say that the gelcoat has some flaws in it (but I repeat myself).  These might be caused by, say a dock that approached too quickly, or a wayward buoy.  Never fear... you don't have to live with those flaws.

Gelcoat is simply polyester resin with pigment and some flow modifiers added to it - there is nothing magic in it.  The magic *is*, however, in getting the right mix of pigments so that it matches the gelcoat on your boat.  You can do this (I have), but it is a truly tedious process and, for me anyway, very very challenging.  Instead, I have an alternative for you.

I wonder if you knew that Fiberlay will make up a quart (minimum size) of gelcoat to match your sample.  They scan the sample using not one, but three different light sources, take the average of those three results, and use that as a starting point for a manual match.  You even get a custom label!

(Pay no attention to the gelcoat smeared on the outside of the can, and don't let the can fall out of your car onto the pavement - the lid will probably come off)
The cost is surprisingly reasonable:  $73 tax included.  That compares to a quart of off-the-shelf Interlux Brightsides urethane paint which pushes $50 pretty hard.  Not bad at all.

Now, here's the tricky part - how do you get them a sample to scan?  If you have something that can be taken off your boat that has representative gelcoat on it (a lazarette hatch for example), then you are in good shape.  If not, then I hope you have saved all those plugs you cut out when installing instruments, etc. 

Always save those plugs
But even failing that, for an additional charge, Fiberlay will send a technician to your boat to do the scan - but I expect that the additional charge is not necessarily trivial, skilled labor being the most expensive commodity in today's world.

Next, you will have a choice to have the gelcoat mixed up with or without wax.

Wax?  Why wax?

You see, oxygen is a chain stopper for the polymerization reaction  that turns liquid polyester resin into solid polyester resin.  That means that the surface of a gelcoat application will not cure where it is exposed to air.  When you are making a boat in a female mold, this is a good thing, insuring that the next layer to be applied will bond chemically with the uncured surface of the gelcoat.  When patching this can be handy too, especially since gelcoat shrinks some while curing, and thus will likely require more than one application to a given patch.

PVA
But eventually, you will want the final layer to cure.  That's where the wax comes in.  If the gelcoat has wax mixed into it, the wax migrates to the surface as the cure progresses, sealing off the surface from the air and making a complete cure.  This is what you would want if, for example, you were spraying gelcoat onto a finished lamination on a male mold.  Or if you were willing to scrupulously dewax the surface before applying another layer of gelcoat.

I chose to have the wax left out.  And I bought a small bottle of PVA (polyvinyl alcohol).  This is a water soluble plastic that can be painted over the final layer of gelcoat to exclude air from the surface.  A simple water rinse removes it.

I will post some before/after pictures later... after the weather gets nice enough to spend time out on deck in the sun.


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Monday, April 6, 2015

When Stainless Isn't


That's our right-hand sink drain. The side of the sink that the tell-tale for the refrigeration pump discharges into, discharges salt water into that is.  And that is not just staining...  it is rust.

Simplistically, stainless steel is an alloy of iron, chromium, nickel and carbon.  There are over 150 alloys called "stainless steel", each optimized for a particular set of properties.  The alloys typically found on a boat are SAE 304 (AKA "18-8", 18-20% chromium and 8-10.5% nickel), and 316 (AKA "surgical stainless", 16-18% chromium, 10-14% nickel and 2-3% molybdenum).  Between these two, 304 is the stronger and 316 is the more corrosion resistant.

But when you are buying plumbing fittings, you are not typically provided any choice of alloy (or even, usually, an alloy description).  The single exception to this is the sink, where sometimes an alloy description may be given.  All stainless alloys are somewhat attracted to a magnet, but 316 is attracted a lot less than 304.  But you would really have to have samples of both to be able to make a valid comparison.  To confuse matters more, the amount of cold work that the piece of metal has received will affect its magnetic properties - a lot.  And finally, we don't have any loose magnets aboard Eolian, for obvious reasons, so magnetic testing of the new drain fittings is not going to happen. 

It is clear that whatever the alloys of the sink and the drain fittings, the drain fittings have the least corrosion resistance.  Still, I installed those drain fittings over 15 years ago, when I replaced the original severely corroded chrome-plated brass ones.

So I guess I am good for another 15 years now.

I hope.






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Monday, March 30, 2015

How much is it?

I just did a post which talked about establishing what the right amount of glycol in a holding plate solution was.  Well, OK, now that we know what we want to have in there, how do we determine what we actually have?  I suppose one possibility would be to simply empty the holding plate and refill it with a solution of known concentration, one that we just made up by careful measuring.  Yeah, that would work.

But what if we just want to add a little water or glycol to what we already have?  For that we would need to be able to measure the concentration in the solution. 

Hand-held refractometer
This is the tool for that:  It is a refractometer - it measures the refractive index of a liquid.

What is that?

All transparent substances slow the passage of light thru them somewhat - some more than others.  The refractive index is the ratio of the speed of light in a vacuum compared to the speed of light in the transparent substance.  So, if I tell you that the refractive index of a particular glass is 1.33, that means that, yes, light travels thru that glass only 3/4 as fast as in a vacuum.  You have witnessed refractive index differences when you, for example, mixed water and vodka, or dove in a place where fresh water and salt water are mixing (at Shilshole, for example).

But for our purposes, it is enough to know that the refractive index of a water/propylene glycol mixture changes in a predictable way with the concentration of glycol.  We don't even have to know the details of that change because the manufacturer has taken that into account in the preparation of the scale inside the instrument. 

All that remains is for us to obtain a drop or two of the solution and put it onto the prism covered by the clear plastic flap, and look thru the lens at the other end of the instrument, for a view like this:

Approximately 33% propylene glycol shown
But there is a catch (isn't there always?).  Before I sample the holding tank solution, I have to completely defrost the freezer.  If I don't, some unknown quantity of the water in the system will be frozen out, which would skew the results in the direction of increasing concentration.  So the refractometer stands ready for duty, waiting for a freezer defrost event.

Who knows when that will be?



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