Tuesday, July 26, 2016

What is it about dark gel coat?

Cleaner/wax application half done on the sheer stripe

What is it about dark gelcoat colors?  They seem to oxidize so much more quickly than the white.  Red is the worst, for some reason.  Dark blue is a close follower.

Could it be that their color absorbs infrared (heat) radiation more readily, making them hotter?  (Chemical reactions double in rate, roughly, for every 10° rise in temperature.)

Could it be that the white pigment (almost assuredly titanium dioxide) does a better job of protecting the interior resin from UV than the pigments used for the dark colors?

Or could it simply be that oxidation on white doesn't show because it is, well, white?  Actually, having rubbed out Eolian's entire hull several times during our ownership, I'd have to say that the oxidized layer on the white is definitely thinner than that on the green.

So I kind of think there is something special going on with the dark colors.  It is that way for automotive paint too...  the dark colors, and especially red, fail first.


Share/Bookmark

Monday, July 25, 2016

The Third Shoe Has Dropped

Finally, I have completed the last of the three cockpit bimini canvas pieces:  the center section.  This panel is zipped to each of the forward and aft roof panels, meaning that its size is completely dependent on the placement of those two panels; they had to be completed first.

But because the old center panel had to continue in service until the new one was fabricated, the forward and aft panels had to be properly located.  In other words, because I did this work in sections instead of all at once, the new roof duplicated the old completely...

Because the old center panel fit perfectly, rather than pattern the center panel with DuraSkrim I chose to simply roll out some Sunbrella and trace the outline of the old center onto it.  The size is not terribly critical; instead it is the zipper placement that is crucial.  That being the case, I did a lot of measuring and annotating on the old center panel:


Again, placement of the zippers is what controls the fit here.  So I measured outside-tooth to outside-tooth at perhaps a dozen stations along the old panel.  Then, when applying the zippers to the new panel, I duplicated the station locations and ensured that the zippers conformed to the measurements.

I have learned thru this project that zipper position in a lengthwise direction is also critical, especially when there are pairs spanning the length.  To make this work out properly, I followed these steps:
  • Locate the centers of both the old and new panels by folding in half, and mark them.
  • Install the old center panel, and transfer the center markings to the forward and aft panels.
  • Work on one edge at a time, I started with the aft edge.  Install one of the new zipper halves to the aft panel zipper.
  • Hold up the new panel, matching the center marks.
  • While continuing to hold the panel in place (you may need help here), make match marks on the new zipper half and the center panel an inch or three away from the center.
  • Remove the new zipper half from the aft panel.
  • Position the new zipper half on the new panel using SeamStick basting tape, matching up the match marks.  Note:  at this point, with no other reference it is not possible to exactly locate the zipper width-wise.  Instead, using another new zipper half on the opposite edge, simply ensure that zipper placement will allow both zippers to fall approximately equally on the fabric.  Exact spacing at the measurement stations will be established when the opposite zipper half is installed.
  • After sewing the first zipper half, take the panel out to the cockpit again and zip it up.  Install another new zipper half on the other aft panel zipper.
  • Pull the panel firm athwartship, and make match marks on the new zipper half.
  • Following the steps above, install the second zipper half.
At this point, zipper installation is half done, with the attachment to the aft panel complete.  Complete the forward zippers in a similar fashion, with these two modifications:
  • When establishing the position of the first zipper half, match up the centerline marks as before.  But this time, slide the panel a little port and starboard, watching for wrinkles to form and dissipate.  You are looking for that placement where there are no wrinkles - it may fall when the centerlines are not quite matched up.  Match mark the zipper half and the new panel.
  • When sticking the zippers in place with SeamStick, be very, very careful to get the outside-tooth to outside-tooth spacing at the measurement stations the same as on the old panel.



Ta DAAA!

Previous post in this series

Share/Bookmark

Monday, July 18, 2016

Mooring Repair


While we were involuntarily moored in Friday Harbor, this unusual work boat (the aluminum one with the I-beam supported above the foredeck, not the white one behind it) dropped anchor near us.  On board were a diver, a man, and woman: the crew.  And two hefty gentlemen who did not participate in operations except to look over the side.   With nowhere to go, we speculated what they were up to...

As we watched, a diver went down with a heavy line.  When the diver returned to the surface, the woman used a heavy windlass (not visible below the bulwarks) and routing the line over a block on the bow she hoisted up...  a concrete block some 6 or 7 feet square and perhaps 18 - 24" thick.  Trust me, this was HEAVY - the bow of the boat dipped a lot.  Obviously a quite substantial mooring anchor.

With the concrete hanging from the bow, the man attached a brand new pennant line, looking like at least 1-1/2", to the anchor block (with a chafe guard of course!).  He then manoeuvred to a good spot and she lowered the anchor to the bottom.  He then attached a (very) used buoy to the pennant, and they all went home.

Conclusion?

The old mooring pennant had parted, releasing the buoy, which apparently fetched up on shore somewhere in Friday Harbor and was retrieved.  The action we witnessed was the reattachment of the buoy to the anchor on behalf of one or both of the observers, using a new pennant.

Conclusion #2?

That boat was ideally designed for mooring installation and maintenance.  We witnessed the maintenance part.  For a new installation, the new anchor would be placed in the bow, and then once transported to the desired location a hoist rolling along the I-beam would be used to retrieve it from the foredeck, roll it out forward above the water, and then lower it to the sea bottom.  Pretty clever design.
Share/Bookmark

Monday, July 11, 2016

Lexan vs. Plexiglass

If you are replacing fixed ports on your boat, you will be faced (or should be faced) with the choice between Lexan (a trade name for polycarbonate) and Plexiglass (a trade name for polymethylmethacrylate, aka acrylic).  Here are some features of each which might help you decide which to use:
  • Plexiglass is transparent to UV radiation.  That means that anything inside the boat will be subject to UV degradation if the sun shines thru the window.  That also means that UV radiation passes harmlessly thru Plexiglass without having any effect on it.
  • Lexan is opaque to UV radiation.  This means that it protects the boat interior from the ravages of UV.  But because the UV radiation is stopped by the Lexan, that means the Lexan is subject to the damage that it is preventing on the interior.  UV damage to Lexan causes it to turn yellowish brown and craze (millions of tiny surface cracks).  The effect is that your view eventually is destroyed:
    Lexan window after 7 years
  • Plexiglass eventually crazes too...  But after a much longer time period.  However it does not turn brown or discolor.
    This Plexiglass port is 38 years old.
  • Lexan is often touted as the "bullet-proof plastic":

    PropertyUnitPolycarbonateAcrylic
    Tensile strength σΜ at 23°CMPa 60-70 80
    Flexural strength σbB MPa 90 115
    Impact strength acU (Charpy) kJ/m2 35 15
    Sources:
    • Lexan 9030 Sheet Product Datasheet
    • Plexiglas GS Product Description

    In tensile strength and flexural strength Plexiglass is stronger than Lexan.  Plexiglass is weaker than Lexan only in impact strength (resistance to penetration by a quickly moving sharp object). 

    These comparisons are made on virgin material in both cases.  I have no data, but all that surface crazing has to act as stress risers and therefore crack starters - much earlier for Lexan than for Plexiglass.
  • Lexan is two to three times more expensive than Plexiglass.
  • Lexan is less scratch-resistant than Plexiglass
So, as in many things in life, the choice is not as clear (pun unintentional) as it might seem at first blush.  As the midway carny says, "You pays your money and you takes your chances."

I will say tho, that for Eolian, we have chosen Plexiglass whenever it was available.




Share/Bookmark

Sunday, July 3, 2016

Best Garlic Press. Ever.


We've tried a lot of different kitchen tools for slicing and dicing garlic aboard Eolian.  But this little jewel that Jane found at the Ace Hardware in Friday Harbor takes first prize, running away.


Here's the business end.  You open the top and place your peeled clove on the grid.  Closing the top pushes it thru; all those little green fingers on the lid make sure that every delicious morsel is pushed all the way thru.


And for neat handling, the diced garlic goes into this little drawer, which you can then just pull out.  I'd say it holds 3-4 tablespoons, which ought to be enough for most meals.  Maybe.  But I suppose you could dump it and come back for more.  (Yes, we like garlic aboard Eolian.  You have been warned.)


For cleaning, the grid snaps out...


And the the gray plastic sweeper (what would YOU call it?) sweeps any garlic goodness that may be trapped between the fingers.  It's a clever design.


Finally, if you'd prefer sliced garlic instead of diced, there is a slicing grid stored in the very bottom.

They come in several colors, for about $10-13.  Now we are going to have to get one of these for the house.



Share/Bookmark
Related Posts Plugin for WordPress, Blogger...