Monday, October 9, 2017


Looking up at things

For several years now, Eolian has sustained a small yet nagging intermittent leak at the mast partners - where the mast penetrates the deck.  After several failed attempts to locate the leak or to pre-emptively stop it, I removed the interior trim and examined things from below, while it was raining.  And leaking.

I was relieved to see that the water was...
  • not coming down the mast, which would indicate a leak at the top of the boot - one of the places I have very carefully examined several times, and
  • not coming out of the foam deck coring, which would mean a wet deck.  Whew!
Instead, the water was appearing at the joint between the deck ring and the deck.  Tho I have repeatedly attempted to seal between the deck ring and the deck externally, it has never been rebedded.

Removal of the mast wedges

So I pulled up the boot and started the removal of the deck ring. I had thought it was a complete ring, but soon found out it was two half-rings, each held in place with three screws.  Well, not quite.

Half the deck ring is off
On the port side, the ring was less than a half, by about 1/2".  Apparently the end of the ring broke off, either in fabrication or during installation.  The pieces were cut from a teak plank - they were not laminated.  At the ends, the grain runs across them, and it is easy to see how an end could have been broken off.  What is a little more difficult to understand is that the installer solved the problem of the missing 1/2" of deck ring by simply filling the gap with what, I surmise, was a giant blob of polysulphide.  Now, after 39 years, it was as hard as a rock.

And so was the sealant that was between the ring pieces and the deck.  I had not given much thought to this, but the mast wedges driven in do bear somewhat on the deck ring.  And as a consequence, the rock-hard "sealant" broke loose from the deck instead of flexing.

Thus leakage.

Add a strip of 1/8" thick white butyl tape
After everything was dried out, I wiped things down with paint thinner and allowed it to evaporate off.  Then I applied strips of 1/8" thick white butyl rubber tape to the underside of the ring pieces.  I then screwed things back in place.  A couple of revisitations to the screws were required as the butyl continued to squeeze out of the joint.
Gap filled
The problem of the missing 1/2" of teak I solved by trimming down one of the wedge pieces and driving it into the gap (lined with butyl tape), and cutting it off flush.

Handy stuff

The final step was to line the complete outside of the ring with some self-adhesive aluminum-backed insulating foam tape, meant for preventing condensation in air conditioners, etc.  On the sides, where the boot hose clamp has little clamping pressure (the mast cross section is rectangular with rounded ends), I applied multiple layers so that the hose clamp would have something to bear against.

Does it leak?
Never thought I'd say this... waiting for rain.  To see if it leaks...



Steve Hulsizer said...

I am surprised that the ring held as long is has. It is an awfully small area to withstand the side, fwd and aft loads as the mast moves.

On our boat we have a flanged aluminum collar bolted to the deck. It stands about 1 1/2" high. Instead of wedges I use a high durometer rubber belt about 1 "thick x 2" wide which I press into the collar, leaving about 1/2" standing above the collar. I have to use the sheet winches and the anchor windlass to move the mast to help get the belt in. A heavier hammer and a drift helps. Then I use a large hose clamp to anchor the rubber.

Additionally, I take mast boot is rolled over at the top, which makes it easier to seal with silicone sealant and hides the hose clamp on the mast.

Good luck, Steve

Robert Salnick said...

Hi Steve -

The mast wedges are supposed to bear against the hole in the deck - it was incidental but critical that they were touching the deck ring.

No, the boot is not rolled over at the top, and I refuse to use silicone on Eolian. Instead, the top edge of the boot is sealed to the mast with wide adhesive-backed aluminum tape, and physically held in place with the hose clamp visible in the pictures. See this post for more info.

Also, I should add that Eolian's mast section is the largest that LeFiel (the spar maker) makes - it is quite stiff. Consequently, there is significantly less tendency for movement at the partners, compared with what might be experienced with a weaker, more bendy mast.


Steve Hulsizer said...

Bob, I don't like silicone sealant particularly, either, but it has its place. Bomar hatches for one, the acrylic sealed to the aluminum,last sealed in 1991 with 3M black silicone. I use the clear for the rolled over mast boot because it remains flexible even after a few mast extractions.

Is it hard to remove? Yes, many times yes. But I have found a product, AutoTech. available through Prism Graphics. Designed to remove vinyl graphics from painted trucks, it does a credible job softening old silicone sealant. It still takes a bit of Norwegian Steam to complete the job, but it gets it all off so it can be painted if desired. It does not damage paint or fiberglass, water soluble but not necessarily biodegradable.

Use the 3M product, not hardware store paintable silicone.


Robert Salnick said...

And Steve I can highly recommend DSR-5 as a silicone remover. But best not to use it in the first place, unless by manufacturer requirement.


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