Keel construction question

[Sarah Fox]

Hi all,

We're moving White Wings (31' model) to a rather lightning-prone area and feel strongly that we need some sort of lightning protection. Among the options we may have is to bond the mast to the keel. However, I don't really know the construction of the keel. Is the lead of the keel encased in a fiberglass skin? Or is there a joint that's faired over? Is it attached by keel bolts? If so, I don't think I've ever seen them. How do you access them?

Thanks!
Sarah and Earline (and the spirit of Earl)
White Wings

[kei...@comcast.net]

Sarah,

Virtually all our Allmand 31's have an encapsulated keel consisting of a slurry made of steel scraps and concrete, supposedly poured to a weight of 4,300 lbs. There was an expensive option for a racing package which substituted lead ballast and added 2 feet to the height of the mast. It was a very rare option that I have never personally seen. You could order the tall mast by itself for much less money which is what I did.

Given the makeup of the ballast I know of no way to effectively bond it for lightning protection. You might try heavy duty cables clamped to the upper shrouds and hanging down into the water.

Good Luck,

Keith on Camelot

---

From: "Sarah Fox" <sa...@graphic-fusion.com>
To: all...@googlegroups.com
Sent: Saturday, June 20, 2015 12:03:41 PM
Subject: [Allmand] Keel construction question

--
--
You received this message because you are subscribed to the Google Groups "Allmand" group.
To post to this group, send email to All...@googlegroups.com
To unsubscribe from this group, send email to Allmand-u...@googlegroups.com
For more options, visit this group at http://groups.google.com/group/Allmand
Visit the Allmand Sail site at http://www.allmandsail.com
Allmand Files: https://docs.google.com/leaf?id=0B0KWQYvl2FcWMGM2NzgyMTYtNDE3Yi00YWU5LTgyMTUtMWU4YzlmODA0NzU3&hl=en

---
You received this message because you are subscribed to the Google Groups "Allmand" group.
To unsubscribe from this group and stop receiving emails from it, send an email to allmand+u...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.

[Sarah Fox]

Keith, I’ve seen that option (cables hanging into the water) discussed, and it sounds like a good option.  The only modification I would put on that design is a spark gap junction in the cable, to isolate the cable electrically from the stays and shrouds, thereby protecting from galvanic corrosion issues.  I was hoping for something simpler and tidier (grounding to the keel), but I guess that’s not an option.

 

Do we have to worry about the steel scraps rusting and busting up the concrete?  I suppose oxygen penetration is very slow, but it must still penetrate, right?

 

Thanks!

Sarah

[james holmes]

Sarah and Keith, I have T. Allmand's personal Tall rig boat, which is set up for racing and probably has lead ballast. The mast is grounded by heavy copper cable running down the mast support to a copper plate bolted to the side of the hull, 12" x 6" about. Fair winds to you, jim

James M. Holmes
Professor, Economics
University at Buffalo
431 Fronczak Hall, North Campus
Buffalo, New York  14260

Email: ecoh...@buffalo.edu
Voice: (716) 688-2461

[Sarah Fox]

How does your connection run from the inside of the boat to the side of the hull?  Is there a special through-hull fitting for that?  And is there any danger of the through-hull fitting blowing up with a big lightning strike?  I’ve considered a plate on the side of the keel.

[james holmes]

Sarah, 2 bolts hold the plate onto the hull, and the cables attach, via nuts, to them. I have no idea about the danger you are concerned about, the setup looks commercial. My boat was never hit by liightning, but the one right next to it was, for what it is worth.

[Ehornick Hornick]

Here's a new ground plate that went on Traveller this spring. I've wondered about that same issue if lightning hits what happens to that plate?
But I've also been on regular keel grounded boats racing with more than 100 boats nearby in dozens of lightning storms and I can't remember a single lightning hit over 30 years. Usually happens at a dock if at all.
I thought the plate was bronze?
Apparently there is only one size available because I tried to get a longer one. Also the bolts did not line up with the old one that met it's demise due to stray current last fall.
You should make sure your through hull fittings are grounded to that plate as well.
Thanks!
Eddie

[Sarah Fox]

Ah, I got it!  Thanks, Eddie and James!

[Sarah Fox]

The danger I’ve heard proposed (but have never heard has happened) is that a strong lightning bolt can vaporize the water, causing an explosion of steam that rips loose hardware and leaves a hole in the hull (e.g. an explosion of steam between the hull and the plate).

[TBoe...@aol.com]

There are many notions about lightning protection.  I will add my "2 cents".

 

The grounding plate and (other metal parts which protrude on the outside of the hull), serve to provide grounding to the earth-thru-the-water.   This can enhance your radio and radar systems, and also serve as a very important part of your lightning protection system. 

 The other very important part of the system is a rod, or other SHARP object at the tallest reach of your boat -- usually the mast head, and bonded electrically to the grounding system.

 

Lightning strikes when charges build up, and ionize the air, in a violent discharge.

 

The job of the lightning rod (thanks Ben Franklin!) is not to attract a lightning strike, but rather to prevent the strike, by offering an easy path to ground for pent-up electrical charges.  As charge builds, it intensifies at that sharp point -- charge-density (coulombs-divided-by surface -area) becomes very high at our sharp-pointed rod, leading to ionization of the air in a small region. In a highly-charged storm, this controlled discharge will sometimes emit a faint light.

 

Old-time sailors, near an electrical storm, would see glowing plasma around these discharges in the rigging.   They called it "St. Elmo's fire".  This was probably because their boats were not as well-grounded as we want ours to be. Or, they had too many sharps above the boat.

 

So... Sharp rod, bonded to ground, should provide a "cone of protection".  (Probably also will protect even your neighbor's boat, if shorter, at the slip!) On the boat, in a storm, I would also disconnect my mast-head radio antenna, and bond it to the grounding system.

 

We cast a finned-design  grounding plates here at our foundry shop -- these go to Dr. John, at Cruise email -- rope antenna.  They are cast from Manganese Bronze alloy.  Mount on outside of hull, with thru-bolting. 

 

Our Allmand 31 apparently had a similar plate installed a long time ago.  This seems to work well.  This boat has never been hit, to my knowledge.

 

If you get hit, even after all the planning and precautions, it would be important to inspect the hull as soon as possible.  If underway, check in the bilges for signs of new leakage.  Electronics should be reviewed also, once out of immediate danger.

 

Ted B.  (grad Eng, former Extra Class Ham, and wanna-be sailor)

s/v Kadiddle

 

In a message dated 6/22/2015 8:36:09 A.M. Eastern Daylight Time, ceho...@gmail.com writes:

Here's a new ground plate that went on Traveller this spring. I've wondered about that same issue if lightning hits what happens to that plate?
But I've also been on regular keel grounded boats racing with more than 100 boats nearby in dozens of lightning storms and I can't remember a single lightning hit over 30 years. Usually happens at a dock if at all.
I thought the plate was bronze?
Apparently there is only one size available because I tried to get a longer one. Also the bolts did not line up with the old one that met it's demise due to stray current last fall.
You should make sure your through hull fittings are grounded to that plate as well.
Thanks!
Eddie

On Jun 22, 2015 8:16 AM, "james holmes" <ecoh...@gmail.com> wrote:

[Beaufort Rob]

Hi Sarah, I had to grind out a delaminated area on the keel of Cadence about the size of a bread plate but pretty deep.  I ground to the cement in one small area and could see the concrete/scrap in the keel.  There was no rust and the metal looked like large stainless rivet heads.  Repair, 3 coats of barrier coat on hull and no issues 3+ years in.  I took a picture but can't find it right now.  Maybe I can scrounge it up.  I had a bronze grounding plate but followed the advise of a boatyard sage and removed it based on his theory that fewer holes below the water line is an improvement.  Every time I'm caught in an electrical storm I regret that decision but, then again, my bilge stay dry until I fill the ice box.

Good luck (Nigel Calder"s "Boatowner's Mechanical and Electrical Handbook" covers lightning protection options),

Rob

[Sarah Fox]

Thanks, Rob!  That would be something if we’re all ballasted with stainless steel!  LOL!

 

I think I’m leaning more and more towards the idea of a ground plate in the hull.  I’ll rig some cables off the shrouds and stays for temporary protection until our next big adventure on the hard (in the late fall – way too hot right now!).

 

Peace,

Sarah, Earline, and the spirit of Earl

White Wings

[Dave_E]

Hi Eddie,

Is "Traveller" your Allmand 31? My 31's name is "Traveler". Allmand 31, hull #15. The only grounding I have ever seen on mine is a bunch of size 8 green wires, bonding several of the through hull fittings together. I have removed most of them. I have a tall rig, but the only reason I would say I have a lead keel is simply because the sales brochures said so.

Dave
Everett, WA

[Ehornick Hornick]

Hi Dave,
Traveller is an '84 35 foot Tri Cabin but from what I have seen very similar to the 31.
I would find some articles by Nigel Calder on electrical grounding or his book "Boat owners Mechanical & Electrical Manual". Amazon has it.
I'm not sure which option Traveller came with as far as keel weight material but it is enclosed by fiberglass so even if it is lead it isn't a good ground source. That's why they have the ground plate on the hull. All of my seacocks and chain plates are grounded to it.
Hope this helps!
Eddie