Tuesday, 19 February 2013

In Again

Spray is back in the water again, resting comfortably in home port.  We got a good signal from the new depth transducer and there were no blub-blub-blub noises coming from the through-hull fitting seals, so we're declaring a victory.

New epoxy, paint, and wax.


Home, Sweet Home.
Yesterday, less than 24 hours before launch, was a good day to try out a number of desperate last-minute tricks, like trying to set gel-coat repairs with a hair dryer (12° C outside but dry), and touching up white scratches in blue gel-coat with a blue felt-tipped marker. Laugh if you will - it looks pretty good !  This morning, the gel coat was dry, if not hard, and the ink …well, I’ll let you know how that fares after she gets wet. 

The biggest novelty for us was a new way of mounting the anode on the propeller shaft. 

I learned the term “sacrificial anode” as a child in introductory science classes, but I’m beginning to suspect that, when applied to boats, this term implies that one must perform sacrificial rituals to get the damn things to work, or rather, to stay in place.

Last August, we dutifully clamped a new 25 mm anode on to the propeller shaft before we launched the boat.  We tightened the screws as hard as we could and put a liberal dose of sikaflex on them.  It couldn’t possibly move.

What we did not realize at the time is that when anodes corrode, they often corrode on the side touching the metal to be protected, which is to say, from the inside out.  That perfectly fitted 25mm hole of the anode clamped around the 25mm propeller shaft in August corroded away over 4 months, leaving the anode free to slide along the propeller shaft. 

If you’re lucky, this situation will simply lead to some strange noises and vibrations, but the anode will stay in the same general area.  If you’re unlucky (as we always seem to be), the anode will start moving up and down along the propeller shaft until it causes real problems.  Ours somehow defied gravity and got lodged at the upper end of the shaft and carved out a place for itself in the fibreglass when we put the motor in gear ! 

Bad anode mounting.
This time, armed with advice from several friends and forums, we tightened the anode screws, pounded the two anode halves together with a hammer and then retightened the screws.  We did this repeatedly until it wouldn’t budge anymore.  Next, we put some tie-wraps on the shaft on either side of the anode so that even if it got loose, it couldn’t slide.  To finish the job, we put sikaflex in the screw holes, along the edges of the two halves and around the shaft to prevent as much water from entering as possible.  We hope this will lead to an immobile anode that will corrode from the outside. 

Good anode mounting ... ?

Posted on Tuesday, February 19, 2013 | Categories:

Friday, 15 February 2013

Naked Again

We’ve stripped off all the old anti-fouling paint (but honestly, is 4 months really “old”?) and have prepped the epoxy layer for new bottom paint… the good stuff this time. 

Removing the last of the "old" bottom paint.
Apparently, you can’t (or shouldn’t) put just any anti-fouling paint on your new epoxy layer.  We had followed the advice of a few friends who recommended putting on the cheapest stuff we could find, since you always have to re-paint every year anyway.  I think you can probably get away with that if you’ve got 20 years of build-up between the hull and the cheap paint layer, but for the first layer on new epoxy, we’ve found out the hard way that you really need something that will hold.  We’re using Soromap AFC Performance Hard Matrix this time, which we’re told will match up nicely with the Soromap epoxy layer below.  And yes, it’s 3 times the price we paid for the cheap stuff.

Hull, before and after.

The next debate is whether it is necessary to put on 2 layers of bottom paint, or just one.  Another friend told us that he has tested the 2-layer hypothesis by putting down just one layer and then making a test patch with a 2nd layer to see if there is any difference one year later, and reports that there is not.  I suspect we will let fate decide.  If it doesn’t look like we’ll have enough paint for 2 coats, we may just put a 2nd coat around the water line and use that as our “test patch”.  Otherwise, I’m pushing for a full 2 coats.

Keel, before and after.

Which brings me to our latest frustration: no 2 people agree on the best way to do something.  We are bombarded with advice, all conflicting.  For newbies, this is a very frustrating situation.  I met up with a friend in the boatyard yesterday who was pulling his hair out over an electrical problem.  These kinds of problems really drive me crazy because I don’t understand anything about electricity.”  WELCOME TO OUR WORLD, I thought !  We aren’t comfortable with ANY of it: electricity, plumbing, epoxies, silicones, hull work, instruments… all of it is bewildering to us.  He then told me that our problem is that we’re perfectionists and that we have to learn to distinguish between what problems you can just live with and what problems you really have to attend to without delay.  I suppose it’s like running:  you have to learn what little pains and discomforts you can run through, and which ones you really should stop and take care of.  But the only way you learn that is by pushing through all of them and getting injured.  Is that where we are?  As it is, we now have LESS confidence in the boat than we did in the beginning, since it seems that every time we go out, something breaks, sometimes with spectacular and stressful consequences.  When will that end?  We’ve definitely got the boatyard blues right now. 
Posted on Friday, February 15, 2013 | Categories:

Tuesday, 12 February 2013

NASA Clipper Duet Depth Transducer, Part 2

Hint: top cap screws off (with heat and a hammer).
We ran into a couple of new “knowledge gaps” with the removal of the old transducer and installation of the new one.  A guy from the boatyard told us to dig out the old seals around the through-hull fitting and remove the whole thing.  After puzzling over this for awhile, Patrick called the NASA Marine Instruments guys, who said, “whatever you do, don’t remove the through-hull fitting.”  The fitting is made to go in once, and if you need to change the transducer, you simply unscrew the top black cap and remove the transducer.   

Sounds simple, but the black cap had also been sealed down and was not going to come off without a struggle.  After several muscle-straining attempts, Patrick came up with the brilliant idea of heating the cap with a hairdryer and gently tapping the sides of the cap with a hammer.  That did the trick.

Now the question was how to put it all back together again, where the biggest mystery was what kind of sealant to use.  Boating forum searches and a call to Guru Bob suggested that two types of sealant would be needed: one that makes a water-tight seal but without bonding pieces together for eternity, and one that bonds for eternity or until you have a go at it with an ice-pick.  Those two sealants are, respectively, mastic silicone and sikaflex 291.  The diagram shows a cross-section of the through-hull fitting with the transducer inside (gray) and where we applied the sealants.

Cross-section of transducer in through-hull fitting.

Old transducer out; Clean through-hull cap for re-use.
After the old transducer was removed, all traces of the old sealant were removed from the through-hull fitting and everything was cleaned.  The sides of the new transducer head were then loaded with mastic silicone.  Patrick opted for a tight spiral pattern, squeezing out mastic like toothpaste around and around until the surface was covered.  The transducer was then passed through the through-hull fitting FROM THE OUTSIDE.  There seems to be some debate about this, but we chose this method because it makes more sense to have any excess on the outside (water side) than on the inside.  When you do this, the excess oozes out around the transducer sides, but once it dries, you just remove the excess with a cutter.  This gives a water-tight bond between the transducer head and the through-hull fitting.

New transducer in place and excess mastic silicone cut away.
For good measure, Patrick added a small bead of Sika 291 to bond the top of the transducer head to the bottom through-hull cap.  In principle, this can be removed with a razor or scraper.  If we ever need to change the transducer again, I anticipate lots of swearing and perhaps a bit of blood-loss as a result of this step.

Next, the top cap of the through-hull fitting was screwed down onto the bottom cap.  Patrick chose not to put any mastic silicone on the threads as our predecessors had done, but instead put a layer around the outside (clear) to fill the gap between the top and bottom through-hull caps.  That should be easier to scrape off later if needed.  Finally, a new bead of 291 (white) was run around the bottom of the cap to reinforce the bond between the hull and through-hull fitting.  The final touch (a special feature for spatially-challenged Patrick) was to add a red arrow to indicate the direction for unscrewing.

New transducer in through-hull fitting.
After re-running and connecting the cables, Patrick had the courage to test it again to make sure it was clicking, and proudly reported that it was.  He reported all these steps to me while I was lounging around on a white sand beach in the 84° F / 29° C Florida sun, reminding myself of why I wanted to live on a sailboat in the first place.
Posted on Tuesday, February 12, 2013 | Categories: