Surveying Wood Hulls
Part 3: Appendix
by David H. Pascoe , Marine Surveyor
Introduction - Part I - Part II - Part III
Appendix A - Hull Planking Types
Carvel Planked
Planks butted edgewise with beveled & fitted edges. No other method of
sealing other than caulking. The primary means of sealing is swelling of
the wood. With age, very prone to leakage and fastener corrosion, to which
all areas of the bottom are subject. Required great deal of construction
skill to make a leak free hull.
Seam Battened
Utilizes a batten over seams on inside. A very effective and strong method
of construction, used mainly by Chris Craft.
Double Planked
Same as carvel only uses light inner layer with heavier outer layer,
parallel longitudinal. Vastly superior to single carvel. Much less prone
to leaking, working and fastener failure.
Double Diagonal
Most often seen on PT boats and minesweepers and Huckins Yachts. If
heavily fastened, this method very strong and long lasting. Both edges and
centers of planks need to fastened to prevent warpage. If not heavily
fastened, planks subject to cupping because of thinness of planks.
followed by water leakage transmitted in the void spaces formed by the
warped planks. In that case, were highly prone to deterioration and
fastener failure. Warped planks spell big trouble.
Plank on Plywood
Another very effective method that is very good at keeping fasteners dry.
Used mainly by Chris Craft. Very strong, long lasting.
Bay Bottom
This method utilizes longitudinal hull side planking and transverse bottom
planking. Vessels built mainly for fishing in protected waters of
Chesapeake Bay and Carolina sounds. A cost saving method that greatly
compromises vessel strength. Often steel nailed. Not meant for ocean use,
short-lived.
Cold Molded
Usually three plies of thin planks in di or triagonal laid up with
resorcinol glue and small nails of monel, copper alloy or bronze. Smaller
boats used staples. Makes for very strong hull but subject to the same
warpage and water ingress problems as double diagonal. Because of molded
nature, fastener problems are usually not relevant but hull shell
deterioration is.
Plywood
This material has gained a bad reputation because of a great deal of bad
design and poor quality plywood. Good quality plywood is little different
than cold molded material, and is superior in that it doesn't warp. Marine
grade ply using mahogany or fir is extremely expensive and not often used.
In recent years, plywood hulls built with.
epoxy glues and resins have proved capable of producing hulls with 30+
year life spans, but only if done right. Lydia of Florida and several
other head boat builders have produced some noteworthy examples. The
prevention of leakage and sealing of panel edges is critical. Larger boats
with double layers are very strong.
Strip Planked
Appears in a variety of forms including edge nailed and the West System.
Usually the strip planks are glued on edges and nailed. Produces a very
strong, long-lasting hull, not prone to leakage. West System uses large
amounts of epoxy glue and is highly rot resistant. Both these types tend
to be monolithic and will tolerate a great deal of fastener failure before
structural failures will occur.
Lapstrake
Longitudinal planking with edges overlapped. Produces a hull prone to
wracking and leaking seams and therefore fastener failure. Not many of
these around anymore.
Appendix B - Recommendations for Safety Equipment and Systems
CFR 46, Subchapter T requirements for safety and life
saving equipment are woefully inadequate. Many private yachts voluntarily
have better safety equipment than what Subchapter T requires.
Water Tight
Compartments Regulated vessels should be required to have no less than
three water tight compartments, designed so that should any one
compartment be completely flooded, the other two are capable of
maintaining the vessel afloat. This is easy to achieve and usually
involves little additional cost.
Bilge Pumping
Bilge pumping requirements are completely inadequate. Most yachts have
better pumping systems than inspected vessels. A standard needs to be
developed that addresses the numerous factors that go into making up an
effective system. Inspected vessels should have both primary and emergency
pumping systems, as do many yachts. Adequate information is available and
retrofitting costs would not be excessive.
Bilge Alarms
Marine surveyors are routinely recommending of the installation of bilge
high water alarm systems in yachts. Many yacht builders provide them as
standard equipment. Such systems can be installed at very low cost and
should be mandatory.
Life Rafts
It is criminal that CFR 46 does not require life raft capacity for the
total passenger carrying capacity of the vessel. It should. Further, life
rafts must be capable of keeping victims out of the water, meaning no
bottomless life rafts. The high cost of immersion suits can be avoided if
sensible life raft requirements are adopted, combined with a requirement
for water resistant wind chill protection such as water resistant
"panchos" or blankets.
Heat Packs
The Japanese have developed very effective, small chemical heat packets.
These are about the size of post card, designed to be placed in clothing
pockets, and are very inexpensive. They last 4-6 hours and combined with
wind chill protection, would go a long way toward reducing deaths
associated with extreme loss of body heat and hypothermia.
Navigation Limits
The EL TORO victims were in the water for as long as 80 minutes even
though the vessel sank within 15 miles of one of the highest
concentrations of marine search and rescue agencies, stations and
equipment. Had this accident occurred in a more remote area, or out on the
open ocean, it is entirely possible that there would have been no
survivors. By no stretch of imagination did the vessel operator act
responsibly by taking the passengers out in the face of posted gale
warnings. All necessary weather information was readily available and the
tragedy would not have occurred had the operator heeded the warnings.
A huge body of data exists linking vessel design and construction to sea
capability and survivability. The designation "small craft" needs to be
further defined and vessel capability linked to predicted weather
conditions.
Emergency Transmitters
Known as E.P.I.R.B.'s - Emergency Position Indicator Radio Beacons, these
devices are voluntarily carried by most offshore yachts and should be
mandatory on public conveyances. Their value is not only in allowing
rescuers to locate offshore vessels quickly, but permitting more rapid
location in fog, rain and other low visibility conditions. These should be
mandatory for every life raft.
About the Author
Dave Pascoe began his surveying career in the heyday of wood boat
building, the early 1960's when the very first mass produced fiberglass
hulls were being built. He started his career on the Great Lakes and moved
to Florida in 1972 so that he has experience in both fresh and sea water
vessels, cold and tropical climates. He has traveled extensively and
conducted surveys and accident investigations for marine insurers in North
and South America, the Caribbean, Mississippi River, Great Lakes, Pacific
Northwest, Europe and a number of Pacific Islands. In addition to having
many years experience on the international yacht racing circuit (even back
in the days of wooden yachts), he has training in yacht design and has
attended numerous seminars and training courses on topics such as
metallurgy, welding, marine engines, failure analysis, fire
investigations, corrosion, electrical systems, maritime law, marine
insurance and so on. He has been a guest lecturer on the subject of marine
surveying at Florida International University and several private schools,
as well general lectures to government bodies such as the Japan Ministry
of Industry and Trade and Nippon Ocean Racing Committee. He is the author
of numerous articles on marine related subjects. During his career he has
conducted nearly 3,600 surveys of vessels of all types, and than 500
marine accident investigations of all types. (PREVIOUS)
- Introduction
- PART 1: Materials and Causes of Problems
(with 4 pictures)
Materials: Wood - Metals, Corrosion: Electrolysis - Galvanism - Stray Current - Oxygen Starvation, Other Factors: Climate - Hull Stress - Wood and Water - PART 2: How to Survey A Wood Hull
Opening Up - Planks & Frames - Weepage - Chine Areas - Forefoot - Transom - Keel, Bolts, Keelson, Clamps and Stringers - Inaccessible Areas - Fuel & Water Tanks - The Exterior - The Bottom Survey - Steel Fasteners - Screw Fastened Vessels - Acceptable Degree of Wastage - Summary of Structural Strength - PART 3: Appendix
[A] Hull Planking Types
[B]Recommendations for Safety Equipment and Systems
First posted 5/25/97 at David Pascoe's site www.yachtsurvey.com. Edited it for this site.
Professional Marine Surveys
- Hull Design Defects - Part I
- Hull Design Defects - Part II
- Surveying Boats With Molded Integral Grid Systems
- Surveying Wood Hulls
- Avoiding the Blister Blues
- Sinking of EL TORO II
- Storm Damaged Boats
- Insurance Surveys and Reports
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