Sunday, December 31, 2017

Lightning Protection

It's not 'lightning prevention', it's lightning protection.

BoatUS published an article in 2015 identifying the probability of lightning strikes as a function of type of boat and size of boat.
Table 1. The probability of a lightning strike by type of boat, 2003–2013 
Type of Boat                                          Chances per 1,000
Multihull Sailboat                                   6.9
Monohull Sailboat                                  3.8
Trawler/Motoryacht                               1.5
All – Overall Average                            0.9
Bass Boat, Runabout, Pontoon Boat    0.1
 

Table 2. The probability of a lightning strike by size of boat, 2003–2013
Type of Boat Chances per 1,000
0-15 Feet         0
16–25 Feet 0.2
26–39 Feet 2.1
40–64 Feet 6
The same article also identifies what to do if you are caught out on the water when there is lightning:
What To Do If You're Caught Out On The Water 
"When thunder roars, go indoors." If there is time, return to shore and take shelter in an enclosed building (not open-sided) or your car. They are not impervious to lightning, but the lightning is less likely to do damage.
But if lightning has already begun, getting closer to shore may bring you close to trees and other objects that could be lightning targets. In that case, stay on the boat and do the following:

  • Go indoors — go down below. Stay in the center of the cabin if the boat is so designed. If no enclosure (cabin) is available, stay low in the boat. Don't turn yourself into a lightning rod! 

  • Keep arms and legs in the boat. Do not dangle them in the water. 

  • Discontinue fishing, water skiing, scuba diving, swimming, or other water activity when there is lightning or even when weather conditions look threatening. The first lightning strike can be a mile or more in front of an approaching thunderstorm cloud 

  • Disconnect and do not use or touch major electronic equipment, including the radio, throughout the duration of the storm. 

  • Lower, remove, or tie down the radio antenna and other protruding devices if they are not part of the lightning protection system. 

  • To the degree possible, avoid making contact with any portion of the boat connected to the lightning protection system 

  • On larger boats with an oven or microwave, putting electronics inside should prevent them from being damaged as the oven or microwave will act as a Farraday cage, allowing the charge to pass harmlessly through the metal around the devices."
From University of Florida's "Boating-Lightning Protection" by William Becker


Another article worth reading is Lightning-Proof Your Boat. Note especially the damage done to the electronics through “electromagnetic induction” and “side flashing”… scary stuff.

An article in BoatUS provides more information. The author is James Coté “…an electrical engineer, ABYC Master Technician, Fire Investigator and Marine Investigator. He operates a marine electric and corrosion control consulting firm located in Florida. For more information, go to: www.cotemarine.net” 



Following are excerpts from DWFORUM in April 2017 in which contributors shared their personal experience in dealing with lightning: 
"I have relied on the stainless stays on the sides with a 2’ square of copper sheeting mounted below the water line and a flattened 1/2” pipe to carry the stay anchor point over the edge to the plate. I’m not sure how effective it is at the top relative to the radio mast, but the connection to the water should be fine. I’ve never known it to be tested, however!"
Tom 
Schultz Apr 3, 2017
"My Paradox does have lightning protection as per plan.  It consists of a copper strap which leads from the top of the mast directly through the boat to the water."Andre-Francois Apr 3, 2017
"The static wicks on an airplane are only meant to dissipate the static charges that build up from the friction of air rushing over the skin.They do nothing against lightning. The skin of the aircraft is your protection, as electricity only travels on the outside of a metal object. Composite aircraft get a layer of metal mesh like window screen to provide this protection. In a boat, just like on land, a metal cage or can is your safest place in a lightning storm.So carry a metal garbage can you fit into on the boat, or build a cage of wires into the cabin for crew safety. A cable from the mast to the water will keep the hull from damage."Josh (Rowerwet) Apr 5, 2017
"...that's what we did on Dad's Wharram. He had a permanent rod off the backstay coming off above an insulator and running down under water and a pair of thick jumpers we'd deploy off the shrouds if we were out in dicey conditions."
Michael Burwell 4/11/17




Sunday, December 17, 2017

Yawls

"Yawl" – from the Dutch “jol”
"Yawl" – a two-masted sailboat in which the rearmost mast (mizzenmast) is aft of the rudder post… a classic example is Olin Stephens' Dorade

Olin Stevens' Yawl Dorade (52' [15.9 m] by 10' 3" [3.2 m])

(Canoe) "Yawl" – a two-masted large canoe-shaped sailboat popular in the late 19th century such as the Iris


Yawl Canoe Iris...

Iris lines...

...and Specs.

(Source for Iris information above -- scroll to bottom of this linked page.)


"Yawl" – a four or six oared small boat used as a tender for large sailing vessels (A small ships boat, usually rowed by four or six oars. (Webster's dictionary 1828))

HMS Victory Yawl Boat



The term “yawl” (in rowing craft) is rather loose in modern usage, often interchanged with Wherries  and Whitehalls. Rowing versions of “yawls” are typically characterized by ‘round’ bottom lapstrake hulls with ‘wine-glass’ transoms and vertical stems. Given the wide meaning of the term “yawl”, following are some examples of various yawls that could be oar cruisers.

Modern Adaptations:

CLC’s Chester Yawl
"Boats like the Chester Yawl were used as working craft in 19th-century.  Efficiency was critical in these human powered craft, so they evolved easily driven hull shapes.  Working watermen weren’t immune to good looks, either, so these “livery boats” were often beautiful.  The most famous of the type, the “Whitehall” boats of New England, are still considered a touchstone of small craft elegance.  The Chester Yawl is based on the Whitehall and adopts its distinctive plumb bow and “wineglass” transom." (From CLC writeup)

Chester Yawl from CLC: 15' (4.6 m) by 42" (1067 mm)

This would be a very effective and beautiful kit-boat oar cruiser… I’d add SOF decks fore and aft and provide for temporary shelter such as these.

Selway-Fisher's Dronheim Yawl

This is a large ‘yawl’ for at least two rowers.

Selway-Fisher's Drontheim Yawl Lines

Specifications...

  • LOA 21'8" (6.6 m)
  • Beam 6' (1.8 m)
  • Hull Mid Depth 2'1" (0.64 m)

Commentary from the write-up...
The Drontheim Yawl was designed for the Causeway Coast Kayak Assoc. - this is a traditional Irish open yawl and we have been asked to model her on the computer and develop the 9 hull planks for stitch and tape construction plus frame shapes only - guidance is available for those who need construction details, or we can draw up plans to suit.



The following are not true 'oar cruisers', but rather sail boats using oars as auxiliary power. (For purposes of this blog, we define an 'oar cruiser' an oar powered boat with (optional) sails as auxiliary power.)

Selway-Fisher Canoe Yawls


Selway-Fisher has two ‘canoe yawl’designs. The first is the 15’ (4.6 m) Lillie  The second is an 18’4” (5.6 m) version of Lillie called Jim Canoe Yawl.

Description of Lillie from Selway-Fisher
This lovely craft was commissioned by Tom Dunderdale after reading the series of articles in the Classic Boat magazine on the 13’ strip planked canoe yawl Ethel. The idea was to produce a canoe yawl of similar style to those of the last century used by Baden Powell and MacGregor and which formed the basis of modern canoeing today but using modern ply/epoxy construction methods with computer generated plank shapes. Her length is based upon the maximum length of plank that you can get out of 2 sheets of ply and we have increased the beam a little over the original Ethel design which allows more extensive cruising and even the ability to sleep on board. She uses 6 sheets of 6 mm and one of 9 mm ply in her construction. The standard set of plans show details for stitch and epoxy construction using 7 planks per side to give a beautiful round bottom hull shape and details are given for her to be fitted out in classic style with a lug yawl rig. The plans include mould shapes and construction details for her to be made using the strip plank method. Tom reports that up to a force 2 she will sail herself both before and into the wind hands off allowing the helmsman to drink his beer  in comfort. Above that, she handles herself with grace and she rows very well with excellent tracking.

Specifications...

LOA 14'11" 4.53 m
Beam 4'8" 1.43 m
Hull Mid Depth 1' 5" 0.43 m
Draft 8"/2'1" 0.2/0.63 m
Sail Area 106 sq.ft 9.84 sq.m
Approx. Dry Weight 353 lbs 160 kg

Selway-Fisher's Lillie lines...

...and Sailing

Iain Oughtred’s Caledonia Yawl 

(Click on Catalog>>Double Ended Beachboats>>Caledonia)

Specifications...

  • LOA:        19' 6" (5.95 m)
  • Beam:       6' 2" (1.88 m)
  • Sail Area: 170.01 sqf (15.8 sq m)
  • Weight:     330 lbs (150 Kg)


Description of Caledonia Yawl from Iain’s website…
I first saw one of these sailing with the gunter yawl rig in Tasmania about 8 years ago. It was a very cold, windy day, white topped waves whipping down the Derwent toward Constitution Dock. The Caledonia Yawl, with it's crew of five, looked very at ease in the unwelcoming Derwent, and I had the feeling that they could have taken much more. 

Iain Oughred's Caledonia Yawl...

...and Profile.



Yawls are beautiful boats and in smaller sizes, make outstanding row boats that are fast and seaworthy.