HNSA Crest with photos of visitors at the ships.

Drydocking Primer

by Richard Pekelney

Below are some notes that are intended to help demystify the planning for drydocking of a museum ship. This list is not intended to be a complete check off list, but may be useful to introduce some of the what is needed for a successful drydocking. Every ship is different so some of what is in here may not be relevant to your ship, and of course this is not a complete list. Perhaps this could be considered as a source of questions for you to discuss with your local experts.

I would appreciate your sending me your corrections, suggestions for improvements, and requests for clarification to [email protected]

A rough listing of what needs to be done to plan for a drydocking:

* Get to know the local maritime community. Develop relationships with the shipyards, tow boat operators, marine surveyors, pilots, port commission, port administrators, regulators, etc. in your community. You will need their advice, services and donations.

If you do not have experienced maritime people in your crew, seek someone with experience that you can trust to guide you through the technical sides of the process. Although this is almost always a team effort to provide all the technical, legal, curatorial and business skills, a single individual must act as your owner's representative. Only one person should be authorized to sign work order changes and that person should be available every day in the shipyard. Your management team will need to balance between the museum standards for preservation and the realities of shipyard work. The curators will learn about shipyard practice and the shipyard will learn about preservation.

* Long lead time permits. Deposits of material often make the berths of museum ships shallow. The coatings (paint) are damaged at the interface of the mud and water. Since museum ships are generally moved infrequently, going to drydock is usually the best, or only, time when it is possible to dredge the mud out. In many ports a permit is needed to dredge. This can take anywhere from a couple of days to as much as 2 years. You must also determine who is responsible for dredging, for example, do you lease or own the berth? No matter who is responsible, the responsible party may have a long lead time to get permission so it should be determined early on and the process started.

* Locate/research needed reference documents. You will want a drydocking plan (showing where to support the ship in drydock), book of ships plans, detailed drawings of anything that might need repair or replacement, documentation from past drydockings, past towing and mooring plans, Tank Capacity Tables, General Information & Damage Control Books, up-to-date tank soundings, amount of oil or oily water aboard and its location, etc.

* Evaluate the adequacy of your mooring plan. Is it designed to survive the expected maximum storm without damage to the ship? What condition is the pier, pilings, bollards, chain, anchors, etc? Do you know how much each element can degrade and still be acceptable? This should be inspected early. If repairs are needed the planning for these might also be a long lead time item. Museums modifying their berths will now have to comply with the U.S. Navy's criteria for mooring a vessel to the 100 year weather event or to the most recent heavy weather event (hurricane, typhoon, etc.).

* Get a skilled marine surveyor preferably with some knowledge of your class of ship to survey as much as can be accessed while still in the water. Contact other museum ships of your class that have been in drydock to share their experience.

* Create a work list of required and optional work tasks to be completed in drydock. The more thorough a survey you do in preparation the fewer expensive surprises you will have later. Since funds are normally tight, prioritize your list. Start with the items that effect the safety and stability of the ship, follow these by the preservation items and only last the restoration items. Give higher rank to work that can only be done in drydock, for example anything below the waterline vs. items that are just easier to do in drydock. More on the list of work is in a separate section of this document below.

With the results of the survey, compile a 'Shipyard Specification Package' that spells out exactly what tasking you want the shipyard to accomplish. Ensure that each task is clearly spelled out with provisions for line-by-line not-to-exceed costs.

* Get a quote on the shipyard work. If you are lucky enough to have two drydocks close by that are capable of handling the work be sure both are invited to competitively bid. Have the yards visit and walk through the ship to make sure they understand the scope. Show photos from the previous drydocking of damage where possible. While in drydock be sure to document any work that will need to be done next time with photos, measurements, etc. If you do have more than one available shipyard, consider the cost/risks of getting to the various shipyards in your selection criteria.

* Seek quotes and/or donation on towing. Seek the help of an independent pilot approved by your insurance carrier. He works with the towing company to create/revise your towing plan. Some of the variables in towing costs/risks are: how long a tow, is there deep enough water, wide enough passage, any low bridges, open water (ocean) vs. closed (in port), seasonal weather, condition of your ship. Your ship should be inspected by the towing company. If the ship has structural damage, you may need to do some repairs before it can be safely towed.

Submit the towing and drydock blocking plans for approval to your insurance carrier. For US Navy donation ships, you must also submit your plan to NAVSEA 21, PMS 333, Navy Ship Donation Program.

* Seek the donation and/or prices quotes of products and services. If you have anchors or other in the water ground tackle, consider crane barge services to pull and overhaul the moorings while you are gone.
If your mooring system includes heavy chain or wire, consider shoreside crane services to remove/replace the lines.
Repairs to pilings/pier.
Towing to the drydock.
Pilot services. Coatings (paint). Most coatings companies will supply a technical representative to help in the design of the coatings system at no cost if asked.

* Contact your insurance carrier and plan who is covering the ship and crew during each phase of the process. Most underwriters will require that a marine surveyor conduct a 'Trip-in-Tow' survey to determine steps to be taken by the Museum to prepare the ship for tow. The underwriter will be most curious as to the requirements for a riding crew. These requirement for a riding crew will be determined by consultation between the owner and Surveyor as to the needs of the vessel for line handlers, length and duration of the tow and risk factors. The Underwriter (and Surveyor) will insist that the supervisors and riding crew members be trained in damage control and proper linehandling techniques. The names, ages and physical condition of the riding crew must be determined before the preparation of the Trip-in-Tow survey.

* At this point you know approximately the cost of the professional services (survey, pilot, owners rep), crane services if needed, towing, the shipyard, etc. Now you can raise money with a credible plan as to how it will be spent.

* Negotiate a contract with the shipyard. The contract must be very explicit in defining terms of work. Terms such as hull, superstructure, underwater hull, free food spaces, etc. all should be explicitly defined. Contract should anticipate miss-estimation of the area of underwater coatings that need to be blasted vs. washed. Quotes should be prepared by area for plate replacement and extended blasting even if you cannot determine this until the ship is out of the water. Include items in the contract to allow museum crew work on the ship while in drydock. Note this will commonly exclude work normally considered shipyard work. Include masking all exposed glass, bearings, brass, etc. before blasting. Do not forget services in drydock like power, water, telephone, portable head that your crew might need. Security, your crew or a 3rd party security company needs to be allowed in the drydock. Be clear on who is liable for damage during tow, while entering drydock, while in drydock, while exiting and during return tow. Be clear on both liability for damage and for injury. Lay days (time in drydock when work cannot be performed) not caused by you (including weather) should not be at your expense. The quality of work (best marine practice, and best museum practice) should be specified. Waste removal and disposal should be explicitly included. A requirement for all work order changes to be in writing is needed. Be clear about top-coat application specifications, for example a two color camouflage scheme may cost a bit more than a single color topcoat. Include provision for museum documentation of all phases of work. Require shipyard to document their work and that you own that documentation. Be sure to indicate that all removed material is to be saved or disposed based on your written instructions. Be sure no cutting or damage of historic fabric is done without the presence of a museum representative. Coatings specifications should be updated with coatings supplier and must be incorporated in the contract.

Below are some typical coating appendix elements:

- When applying multilayer coatings, the color of coatings shall be alternated.
- Coating manufacture's rep. should be present for quality control during all critical phases of coating application. Manufacturer's recommendations for storage and application of coatings shall be strictly followed. No coatings will be applied if it is raining or if temperature/humidity exceed manufacture's recommendations.
- Areas to be blasted or ground shall be cleaned of dust and coated the same day.
- New sections of shell plating and wasted seams shall be sandblasted to SPSS-SP10 printer to installation or welding. Weld slag and oxidation dust shall be mechanically removed prior to application of coatings.
- Supply the Navy numbers and commercial equivalents for the colors on all the topcoats. Period color matching charts available for sale (i.e. Snyder Enterprises).
- Areas where the primer has failed normally get blasted to SSPC-6. Work with the paint vendor to use the least abrasive possible.
- Where the coatings are still tight, a chemical wash may be acceptable as a prep. and will avoid blasting.
- Repair of interior paint disturbed by weldments. Hand ground to SSPC-SP6, edges feathered smooth to good paint, spray coated with one coat primer at 4 mils mdft, two coats of anti-corrosive at 8 mils mdft each.
- Repair of underwater hull. Cleaned to SSPC-SP6, edges feathered smooth to good paint, spray coated with two coats AC at 8 mils mdft, two coats AF at 4 mils mdft. AF coating to be applied within 6 hours while anti-corrosive coat is still tacky.
- Normal bottom where paint is tight AF overcoat of bottom. High pressure (300 psi) water blast, one coat prep wash, two coats AF at 4 mils mdft per coat.
- Interior of Sanitary Tanks - Blast to SSPC-SP6, one coat AC at 8 mils mdft, three coats of AC 6 at 8 mils mdft per coat, applied by brush to all knife edges and under sides of all angles, then one coat AC off white at 8 mils mdft.

SSPC-SP10 and SSPC-SP6 are standards for how the metal is prepared for coating. See for explanations of SSPC standards.
AC - Anti-corrosion coating that protects metal.
AF - Anti-fouling coating that prevents marine growth.
MDFT - Minimum Dry Film Thickness
mil - 1,000th of an inch

* Plan shoreside activities that will occur while the ship is gone. This is often a convenient time to overhaul the ticket booth, bookstore, brow, etc. Repair of the pier or wharf and offshore moorings are best done while the ship is out of the way. Note that you may still need to maintain 24 hour security coverage, but now in two locations, on the ship and at the museum.

* If you anticipate moving rudders, elevators, dive planes, shudder doors, boats etc. to expose paint surfaces, do as much research, repair, museum crew training, practice as you can to minimize delays in the drydock.

* Announce closing dates in advance to avoid disappointing public and to solicit contributions. Consider what kind of PR will be needed to keep the public informed about what's going on and how they can help?

What will be done when you are not able to provide tours to visitors during the drydocking period? Will the drydocking and maintenance work be interpreted in any way? (For example a panel with graphics and info about why the sub is not there and why maintenance is so important, maybe an apeal for funding.) How will you cope with the loss of revenue from tours, overnights, etc.?

* Prepare ship for movement. Sensitive artifacts are removed. Everything properly stowed for sea in anticipation of unexpected rolling. Bilges cleaned, sanitation tanks emptied, loose gear on deck or under superstructure removed or secured, etc. Find and have finding aids ready all drawings and microfilm of the ship in case there are unexpected repairs. Duplicate extra copies of the book of general plans and drydock plan. Crew of tugboat, small ship riding crew and shipyard crew should all briefed on safe belays to the ship, line handing, emergency procedure, communications procedure, etc.. Show everyone what is safe to secure to, and what is not. As a courtesy, inform the local Coast Guard. In the USA, if you are in a Vessel Traffic Services controlled area they appreciate advance notice of ship movement.

* Ship leaves for drydock. This may require a shoreside crane to remove brow and mooring chains from ship. Of course the tugboats, and pilot.

* Once at the drydock the ship is positioned, the forward blocks are set, a diver verifies the block position and the ship is lifted (or in graving dock the water pumped out). The ship is quickly powerwashed to remove marine growth. A detailed inspection and photography walk through then occurs. At this point decisions are made on areas to be blasted vs. cleaned, un-anticipated items, and optional items. Once this is negotiated, everything possible should be done to avoid further work order changes.

* While the ship is away, repairs at the home berth can progress. Removal, inspection and replacement of ground tackle, dredging, pier (pile, dolphin, etc.) repair.

* Ship returns. The process of leaving is reversed. Shoreside crew is ready to accept lines, crane (if needed) is standing by, etc.. Any ground tackle that was reset is carefully watched for some time to see if adjustment in the length of chain is needed. The need for an adjustment (and necessary crane use) may not be needed, but it should be planned for.

* Write down lessons learned for next drydocking.


Various Work Items to be Considered:

- Towing, pilot services.

- Docking, fleeting (changing block position), undocking.

- Lay days. You should be charged only for lay days that are your fault. The yard should be responsible for weather, equipment, crew, etc. delays.

- Services-Electricity, water, air, toilet, phone, etc. as needed.

- All underwater moorings, chain, etc. should be inspected every 2-5 years. The movement of the ship is an opportunity to pull, inspect and overhaul any underwater ground tackle. What amount of wastage is acceptable for mooring chain? For the Navy version of this see:, choose Design: Moorings ufc_4_152_03.pdf pages 59, 60, 120. ABS, American Petroleum Institute, and DIN all have standards in this area as well. Note these standards all assume the chain was properly sized when installed.

- Berth should be dredged if it has silted up.

- Replace existing zincs if an active cathotic protective system is not in use. Document location and weight on removed zincs so the information can used to plan the proper number for replacement. Include replacement of broken studs, drilling and shaping of zincs as needed. If this is your first drydocking consider replacing any weld on zincs with bolt on.

Onboard impressed cathodic system anodes should be inspected, cleaned and if need be, replaced at time of drydocking.

- All underwater coatings repaired and refreshed. Contract should anticipate movement of rudder to expose all areas. On ships that have them, movement of torpedo shutter doors, bow and stern planes, elevators, gangways, boats, etc.. Prepare to replace any gaskets below the waterline if needed (for example a torpedo tube door.) Contract should anticipate fleeting the ship to cover %100 of the bottom. Preparation and Coating schedule must be included in the contract and must be based on recommendations from coating vendor. They should balance the minimum abrasion possible to avoid wear on the historic fabric and the need to achieve good coating adhesion. Explicitly define free flood spaces, tanks, inside and outside of superstructure. The more clear you are in the contract about what areas are included or excluded the better. Experience has been that properly applied modern coatings in salt water with a good electrical system and cathotic protection will last 5-7 years.

Separately quote areas above the waterline from below the waterline.

- All sea chest and through hull valves should be cleaned and valves overhauled. If they are blanked and the blanks are in good condition the valves may not need to be overhauled. If they are not blanked, give serious consideration to blanking any through hulls. All submarine flood ports must be blanked. Heat exchangers. If the sea chests are not blanked, then test, clean and rezinc heat exchangers.

- All tanks should be emptied, cleaned and inspected periodically. (Note many of these can be done at lower cost pierside.) Entering a closed space requires properly trained and equipped crew (shipyard competent, confined space entry). Keep good records of when each tank has been inspected and its condition. All replacement ballast water should be fresh water and treated to maximize coating life. You should plan on what treatment you prefer in advance so it can be ready for use and its cost included in the refilling of the tank. Wherever possible the tank should be full or empty. No residual oil should be left in any tank. Some vessels have tanks that can only be accessed in drydock. These should be given high priority to be inspected when they are accessible.

- Open and inspect torpedo outer doors. Inspect rubber seals. Include cost of removing and replacing any strongbacks or other safety devices. Note that at least on Fleet submarines the seals are a unique shape that need to be ordered well in advance.

- Inspect shaft packing. Inspect and service tailshaft covers. Remove propellers if in place and plan for transportation and storage.

- Inspect all weld seams, esp. around blanks and doublers. Ultrasound test any areas that are pitted or otherwise degraded. Uninspected tanks may look fine from the outside, but be corroding from the inside.

- 24 hour coverage by crew should be planned.

- Consider inspecting and flood coating inside castings in the stem, rudder or dive planes, etc. as relevant to your ship.

- Unique to older submarines, the anchor chain is in a free flood locker. The chain should be removed from the chain locker. The iron in the chain interacts with the steel and bronze in the area accelerating corrosion and preventing access in drydock.

- Any large batteries should be checked for acid. The electrolyte should be removed and properly disposed.

- Major electrical projects are often best done during drydocking when there are no visitors aboard.

- Keep records of what areas that are know to be free of lead paint (for example, areas blasted to white metal) and those that have not been tested.

See also:

My thanks to Joe Lombardi, Ship Surveyor for his helpful comments.

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