Friday, January 25, 2013

Surveyor Guide Notes for Wooden Vessels Survey

We are still occasionally receiving requests for surveys on such craft, usually for yachts, harbor tour boats, tugs or barges. The following material on such surveys is therefore provided for your reference.
Surveyors should be reminded that if the vessel is classed with no geographical or other service limitations, it must be surveyed as for full ocean service, even though the vessel may be only engaged in some restricted usage such as harbor tourist service at the time of the survey.

Further, where wood rot, worm damage, or manifestations of aging deterioration are being dealt with on a progressive basis as it advances (i.e. from survey to survey), this must be so noted in each survey report covering the area in question with a suitable notation for the future re-examinations.
1. Types of Deteriorations
The primary deficiencies that the Surveyor must look for are as follows:

a. Decay or dry rot.
b. Marine borers: Teredos and shipworms.
c. Fastener failure: corrosion, loosening, or breakage.
d. Caulking rot, shrinkage, or ejection.
e. Wood cracks, breaks and checks.
f. Wear and tear, abrasion.

2. Rot or decay may often be determined first by sounding the wood with a hammer, however one of the mast effective means is by probing with a long sharp probe such as an ice pick, supplemented with drilling or coring as necessary to establish the extent of deterioration. These holes of course should be properly plugged on completion and if internal. They should be treated with a fungicide in order to prevent access for spread of rot.

Rot is a breakdown of the structure or the wood caused by a fungus which thrives in areas where rainwater leakage or condensate (i.e. freshwater) can collect, and where ventilation and drainage is poor, such as internally at the lower part of the stem, sternpost or transom; at the top ends of the side frames, al the edge of the deck, under bulwarks, around overboard discharges, in and alongside the keel and keelsons, in the garboard strakes and turn-of-the-bilge areas, al butts of planking and framing, alongside engine bearers, and in any other internal areas where drainage or drying is restricted by horizontal internal members, plugged or inadequate limbers, or where end-grain is accessible to moisture.
In addition to probing or boring, selective sections of interior lining or ceiling should be removed lo examine the framing and planking inner surface, particularly alongside the keel, at the bilge margin, and at the lower areas of the stern post or transom and stem.

3. Marine borers such as Teredos and shipworms often leave no obvious exterior signs of entry and must be located by judicious probing and hammer testing of the exterior underwater areas, particularly where the bottom painting (or sheathing) has bare spots or is worn bare from abrasion, such as along the keel.
It should be noted that damage from marine borers can proceed very rapidly, therefore repairs and preventative measures should not be unduly postponed.

4. Fasteners - screws, nails, bolts or rivets - may fail due to galvanic action, salt water corrosion, chemical (acid) corrosion from the wood, or by simple mechanical failure due lo overloading or fatigue. Their effectiveness may also be lost due to loosening from the working of the hull or from decay of the wood around the fastener.
Fastener failure may be first indicated by the planking butts and seams showing sign of movement or “Working” with resultant disturbance of the caulking or paint. Also, the planking butts may show signs of lifting above the level of the adjacent planking, or the fasteners may start ejecting the plugs or filler putty covering their heads. Hammer testing may also indicate loose fastenings by vibrating when struck.
In order to check the condition of the fasteners, any questionable specimens should be removed far close examination and possible testing. This would also apply to treenails (wooden pegs locked in with end wedges). Usually the only remedy for loose fasteners is renewal, tightening up (except for clenched rivets) is rarely successful.

5. Caulking fails by rot or shrinkage. It may also be ejected or lost due to the “working” of the hull or washing out after breakdown of the caulking compound.
Caulking should be checked at random locations or where there are obvious signs of ejection, deterioration or leakage, and renewed as necessary. (Yard pea pie unfamiliar with wood vessel seam work should be cautioned against excessive driving-in of new caulking as this can spread the planking and loosen the fastenings).

6. Wood cracking and breaks are usually obvious damage defects that require renewal work. Seasoning “checks” or splits along the grain are normally of no significance except as an entry access for decay or borers so should be plugged. Care should be taken that renewal sections of planking or framing are properly installed to fully replace the original strength. Replacement planking sections should span at least six frames and splices lo the existing planking should be made by butt blocks between the frames. Bulls of adjacent replacement planking sections should be staggered. Partial replacements of keel and stem usually necessitate angled splicing. Cracked frames should be cropped and part or all renewed, or may be sufficiently compensated by “sister frame” sections alongside.

7. Wear and tear often results from the vessel riding or ranging against pier fenders (side and comers), from touching bottom (keel and bottom), or from contacting other vessels (sides and corners). Where the strength of the vessel may be affected, full or partial renewals in these areas may be required.

8. Wood vessels are not eligible for Year of Grace for completion of Special Periodical Survey or for Underwater Inspection (by divers) in lieu of Dry-docking Survey.

9. Wood vessels are normally classed subject to “Annual Survey”. This means that a comprehensive examination including a Dry- docking Survey is required annually. Al the end of the fourth year this survey is somewhat expanded and credited as the Special Periodical Survey of Hull.
The surveys should comply with the applicable requirements of the Class Society Rules, plus additional examinations as appropriate for wood construction. Noted below for guidance are typical examinations for the aforementioned surveys.

Special Annual Survey: Underwater body including keel, bottom and side planking, stem. stem post or transom, rudder and bearings; weather decks, bulwarks, hatchways and covers, guardrails, ladders, mast and standing rigging; anchors, chain and windlass; ventilator coamings, portlights, skylights, steering arrangements, internal structure and enclosed spaces as accessible or where suspect.

Special Periodical Survey: All the above plus internal examination of the entire hull structure including keel, keelsons, framing, beams, knees, stem, and transom or stern post. Ceiling, Sheathing or lining to be removed, fastenings and keel bolts drawn, and borings lo be taken as deemed necessary by the Surveyor.

Reference: US. Coast Guard NVIC 1-63 CH-1: “Notes on Inspection and Repair of Wooden Hulls”.