The album of Ariel #422

[CapnK]

*Not* including a tabernacle - that is just something I have been considering, and this guy does really good work. His welds are really nice, and I am getting exactly what I design.

Though I do like the SS Ballinger (?) hinged mast step, I think a tabernacle is a better way to go for me. Ideally, I would like to be able to lower the mast by myself as easily as possible, if/when need be. It looks like to me that a tabernacle offers some better options than just a hinged base. It can be designed so that the spar can clear the cabintop step, for instance, as well as giving me stronger connection to the deck due to having a larger base (that I design that way).

So that means I have to come up with a different mast base solution, especially considering that I am not screwing/bolting thru-deck into a wooden beam any longer. Ideally, I want to not directly mechanically (or therefore electrically) bind the mast to the aluminum support inside. Cuts down on corrosion, and helps keep lightning out of the inside of the boat*, that way.

And I don't really have to design a tabernacle, really - I just have to adapt an age-old design to this particular boat. Right now, I am considering through-bolting it to the aforementioned 'ribs' on either side of the aluminum mast support.

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An ebbdendum (if I can coin a phrase ) to the above: there is a lot of uncertainty about lightning, except for three things that I can see:

1) It can cause a lot of property (and personal) damage.
2) It is not at all predictable.
3) That it *does* like to go to ground along the most direct path, is about the only thing scientists seem to know for sure.

The most direct route OFF of the boat from the masthead (the most likely place to take a strike) is: the backstay.

Backstays make no turns on the way down, and terminate closer to 'earth' than the forestay. On our boats, they also have the added bonus of having the most physical separation from belowdecks. OK, only by a little bit, but that might be enough. So it seems to me that they are the best way to attempt to route lightning, or at least to give it a good, easy path to ground. I have some ideas about that, for down the road...

Might not be much of a concern for a lot of you, but lightning here is fairly frequent, year-round, and darn near a plague in summer. There's that, and a couple too-close experiences with it, so I am keeping it in mind as I do all this.

[ebb]

Hey Kurt,
1, 2, 3 exactly.
Once we discussed that here - and I took seriously an internet lightning expert's recommendation to connect the chainplates and the mast plate inside the boat to fat naked copper wires in big radius curves to a couple big bronze bolts that go through the hull and clamp a bodacious chunk of bronze to the bottom - as so-called 'ground'. I remember the plate for some reason had to have SQUARE EDGES - couldn't be faired to the hull or slanted.

Until I remembered the irrationality of 10 million volts of lightning which might just go ahead blow out the bottom of the boat.

And why the hell would you invite that mother inside?

Somebody came up with a poorman's solution that I've never heard better.

When lightning threatens: clip a battery cable to each stay and shroud and drop the end in the water. We'd have an octopus of eight convenient grounds the enemy could choose. One or every leg.

Enhancements might include a lashing for the clips to keep them secure to the turnbuckles. A flat metal plate soldered to the ends, maybe 4"X4", in the water.
And a canvas bag to keep them ready in the locker.

[CapnK]

Reason for the square edges: the 'point' where sharp edges meet will allow lightning a quick, clean exit from whatever it is running over. Lightning travels along the surface of things, and doesn't like to turn - so it's like Wile E. Coyote on a cliffs edge when it comes to a square turn, and off into 'ground' it'll go.

At least, that's what I've read/"they" think...

One company markets a ridiculously expensive copper pipe thingy that has points and sharp edges all over/inside of it. They claim that it has, for the diameter of a relatively small pipe, some huge amount of surface area thus exposed to ground. More hydrodynamic that a plate. Seems like you could get the same result with one of those "static dissipating" brushes, stuck in the water instead of at the top of the mast.

I've thought to devise a folding or telescoping arm(s) that just flips down into the water behind the boat from off the backstay(s), try to keep edges and surface disruptions on it to a minimum, see if I can't make it a nice "off ramp". The other thing is the external chainplates; my uppers are going to terminate close enough to the water that if I am heeled, it'll be a short jump there, too.

Of course, keeping a battery jumper cable coiled in a accessible box is another easy layer of (hopeful, isn't it all?) protection.

I'm with you, Ebb - our boats are too small inside, to be sharing it with gazilabazillions of volts. And I don't want to live with large diameter cable/wire artfully looped all throughout the cabin. Because it would have to be intrusive, to make that kind of ground system effective, IMHO.

Wandering farther afield: The idea of the new synthetic rigging tickles my noggin; being able to keep a supply of small diameter line aboard instead of a big coil of SS wire for rigging repairs/replacement makes more storage sense. But I wonder at the ability of the miracle fiber to handle the temps of a lightning strike. And having the mast held up solely by 'rope' means any lightning which comes has only one conductive path down - and that's straight to the cabintop.

Might be a good thing for emergencies, though...

Contemplating using something like this FRP rod for the 'core' of my 'ribs':

http://www.trippplastics.com/product...s.asp?catID=22

It looks like the Pearson factory used a side grinder disk to trim the edges of the cabintop liner, because I can see where the under skin was penetrated by just such a device. I'm going to need to remove 3-4" of the liner, in order to bond directly to the underside of the deck. Trying to think of how best to do that, what tool to use. Dremel comes to mind, but I wish I could find something more along the lines of a "nibbler" like sheet metal workers use...

[ebb]

I know the liner in 338 isn't very thick.
It may be made with only matt, no cloth, and cuts like parmesan.
Played with it when the cabin windows were filled.
Chopped out the dodger's window rabbets with a DREMEL CARBORUNDUM DISK very easy. A bit tedious but it's a lite and accurate tool. Not exactly the same material as gelcoat and matt but it wasn't fazed by the thicker glass fabrics. The disk is a mm thick, 1.25" D. They mount to an arbor supplied by Dremel.

Have access to a Fein Tool? It oscillates rather than spins. One of their thin cutting blades would slice the liner in no time. They have a thin metal spatula shaped cutter that you could run along a batten propped (or double-stick carpet taped) in place. No brainer. And it has a funky vac attachment that helps collect the dust. But it produces less dust than spinners.

[When I look at some of the hefty backing plates some have used for winches and clutches on the roof, I can see propping a plate against the liner, using the FeinTool blade to cut the liner using it for the pattern, and then rubber mount the winch's backing plate directly to the underside of the coach roof. Wooden plates would definitely appear smaller/thinner and custom. If yer worried about the liner being loose, or you want to flatten a bulge, or have an even neater look, use a slightly smaller pattern to cut the liner hole and rabbet the backing block so that it laps over and supports the liner it is going thru.]

No cut approach.
Can you glue the liner to the roof - then glue your strongback to the liner?
Would work if you include some thru fasteners too. Trouble is the cabin liner was laid-up upside down in a mold and the finish layer of matt and polyester might have had wax in it to get it to set hard. That wax might still be there on the roof AND on the liner. I'd probably use LifeSeal after dewaxing and abrading to install. I used thickened epoxy which is perhaps TOO rigid.

I feel the bulkhead and any support going across the roof inside has to be immobilized by frp tabbing or glue or adhesive (or all of these), especially if the bridge is not going to be fastened thru the roof. imco

In the '60s right angle grinders swung 6" and larger disks and weighed 10#. We have those 4" Makita's now.
Seldom use mine inside anymore because the tool high speeds dust into EVERY nook and cranny all over the boat. It uses a thicker carborundom disk making ten times the mess of any other tool. I wouldn't use it!

I had the bulkhead end of the liner exposed when the strongback was removed. Liner was crooked. 338's liner was put in crooked! Clamped in place by the woodtrim and windows it caused stress bumps and hollows and bulging edges under the deck that are still evident. You'd think that after 337 cabin liners the guys at Pearson would have had it down by the time they got to Little Gull
- without having to crap it in place or cut it to fit!!!
Dang farmers!


Success in your endeavor , sir!

[Commander227]

Here is what it looked like when my Ensign was hit by lightning. She was sitting at her mooring amid taller masts when she got it...poor girl. The Ensign has the chainplates grounded to the bronze through hull which is suppose to dissipate the load... it didn't quite carry all the load as the lightning found 28 other places to disembark.