Surveying Wood Hulls

Introduction

PART 1: Materials and Causes of Problems 
(with 4 pictures)

PART 2:  How to Survey A Wood Hull

Appendix A - Hull Planking Types

Carvel Planked - Seam Battened - Double Planked - Double Diagonal - Plank on Plywood  - Bay Bottom - Cold Molded - Plywood - Strip Planked - Lapstrake 

Appendix B - Recommendations for Safety Equipment and Systems 
Water Tight Compartments - Bilge Pumping - Bilge Alarms  - Life Rafts - Heat Packs - Navigation Limits - Emergency Transmitters - About the Author

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. 

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)

First posted 5/25/97 at David Pascoe's site www.yachtsurvey.com.  Edited it for this site.