ON DECK
The next sub heading from the survey report covers sections 14-20.
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ON DECK |
14. Main companionway and other accesses to accommodation
15. Ports, windows etc
16. Pulpit, stanchions, pushpit, lifelines and jackstays
17. Rigging attachment points
18. Ground tackle and mooring arrangements
19. Other deck gear and fittings
20. Davits and boarding ladders
Some of the sections in this chapter are common sense and require little explanation, comment or illustration by report extracts.
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SECTION 14, MAIN COMPANIONWAY AND OTHER ACCESS TO ACCOMMODATION |
• Security and condition of main hatch. Plywood hatchboards sound? If the vessel is an offshore type are all hatches properly watertight and in a position so as not to allow premature downflooding?
• For offshore can the hatch be operated and secured from deck and below? Can hatch boards be secured in place independently of the sliding hatch? Many forehatches are now hinged on their aft edge (often due to the position of a babystay) and this is generally considered acceptable.
• Condition and type of all other hatches. Any perspex crazing? Hatches generally sound? If a hatch is clearly an escape route from that part of the vessel, is it actually large enough for this purpose?
• Hinges intact and secure method of closure provided?
• Gaskets intact, any signs of seepage from below?
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• Are the ports lying tight and fair to the coamings externally?
• Thousands of production boats have been built with aluminium framed ports fixed with stainless steel bolts and chrome plated brass dome nuts known as internuts. In use the aluminium frames and the internuts corrode.
• Random test any fastenings with a screwdriver.
• Many ports are now simply bonded in position and when the hull flexes these can become loose. So give them a tap with your clenched fist in the direction away from the bonding.
• If set in rubber of limited strength not suitable for offshore.
• Crazing to perspex? If surface mounted look for splits around the fastenings.
• If glass is it toughened?
• General condition plus gaskets if of opening type.
• Leaks from below?
REPORT EXTRACTS
Corroding window frames
All the ports are of aluminium framed toughened glass and some corrosion is present in the frames. This type of port utilises aluminium frames with stainless steel bolts and chromed brass dome nuts, (known as internuts), thus some corrosion is inevitable. Fastenings were sampled at random in the eight ports and were found to be holding well. The ports are currently considered satisfactory but some failure of fastenings and further corrosion to the frames over the next year or two is inevitable.
Crazed perspex windows
Vessel fitted with eight aluminium framed fixed perspex ports. Some crazing present and the worst crazed windows should be replaced for serious offshore use.
Some corrosion is present in the aluminium frames. This type of port utilises aluminium frames with stainless steel and chrome plated brass fastenings, thus corrosion is inevitable, but still considered secure and serviceable.
Failure of bonding
The polycarbonate lights are bonded in place and when gentle pressure was applied to that by the chart table it simply fell out.
Recommendation: Given the failure of the port close to the chart table all other ports that are bonded in place should be checked.
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SECTION 16, PULPIT, STANCHIONS, PUSHPIT, LIFELINES AND JACKSTAYS |
• Security and general condition. Aluminium bases very prone to vertical splitting due to build up of oxide in the socket. If any item has been wrenched check very carefully for any consequent damage to the deck and structure. Stanchions become very powerful levers when weight is applied. Where stanchions are attached to an aluminium toerail any wrenching could make the hull deck joint (bolted via the toerail bolts) leak. Wherever possible check the underside of fixings for seepage, corrosion and sufficient backing pads, reinforcing in the laminate etc.
• Always check plastic covered wire lifelines with a magnet. If magnetic they are galvanised wire and prone to rust unseen under the sheathing. Condemn them. Talurit type terminals are frequently found on lifelines and if the wire is stainless they must be of copper, or if galvanised wire they must be of aluminium, but occasionally one finds these mixed up, if so should be condemned.
• Security of all lashings, are they UV degraded?
• Are all jackstays and attachment points secure? Terylene webbing is very prone to UV degrading and chafe to the stitching where the eyes are formed each end. Carefully check this, someone’s life may depend on it. Are any shackles locked up with seizing wire or cable ties?
Fig 94 shows a typical wrenched pushpit foot and while the pushpit was still secure enough it didn’t end there. A long term leak via the fixing bolts had spread along the laminate, rotting the plywood backing pad incorporated into the moulding. The pad was a long piece of ply serving both the pushpit and aft mooring cleat which was severely weakened, with the bolts about to pull through the soft plywood. All this was only found because the plywood lining panel under the deckhead was damp and slightly stained and was thus removed.
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This is one of the most important areas in a sailing vessel and one where numerous defects are found.
• Check for any obvious movement, distorting to deck, stress cracks in fitting etc. Where U-bolts are used it is important that the bolts are following the line of the rigging attached to them in a nice fair line otherwise excess stress is placed on the fitting. One often sees vertical U-bolts with lower shrouds attached at an unfair angle.
• Access is often very restricted or impossible from inside the boat. Where this is the case use a moisture meter on linings etc looking for seepage. If this has been present long term, crevice corrosion may be present in the hidden stainless steel components. Recommend dismantling for full inspection.
• Test on deck with a long crowbar using a hardwood block as a pivot placed on a plywood pad to avoid damage to deck. Get as much leverage as possible and be brutal.
• Are fittings lying tight and fair to deck? If seepage is present and they are bolted to bulkheads these may be rotten particularly behind GRP bonding. Hammer sound and spike test.
• When heavy brown staining to the fixing nuts etc is present crevice corrosion is probably developing in the threads. The shanks of U-bolts are also very vulnerable where they pass through the deck. Tap all accessible internal nuts and bolts with a hammer and screwdriver.
• Where arrangements are in place to dissipate the stresses into other parts of the structure, i.e. tie rods or plates attached to knees etc bonded into the topsides check the topsides and adjacent structure externally for distortion. It is essential to state in all reports in this section whether the rig was set up hard or not (or obviously if mast unstepped). If the rigging is slack defects may become apparent when it is set up.
• Is the forestay fitting merely bolted to the deck or does it have a plate running down the stem or similar to transfer some of the loadings into the hull? Check all welds for stress cracks.
• If the rigging has been slacked off prior to survey ask yourself why and aggressively swig the shrouds etc.
Fig 96 shows a typical stress crack along a weld in a stemhead fitting to which the forestay attaches. The crack is travelling aft along the weld and the tang is severely weakened. This type of vertical tang welded to a base plate typically has two or three holes where the forestay attaches and the forward most hole is in use as was the case here. This forwardmost position is often forward of all the bolt fixings thus placing an unfair strain on the plate. So always check the position of the forestay attachment in use in relation to the bolt fastenings.
Fig 97 shows a stainless bolt removed from a conventional stainless steel chain plate bolted through the topsides of a bluewater yacht. The bolt is severely corroded immediately under the head and with the pitting established in the shank future corrosion would be quite rapid. Whatever claims are made for this material, and in spite of assurances from metallurgists, my experience has been that even the highest grades found in production boatbuilding are very unpredictable in the marine environment.
I am firmly convinced that the shanks of bolts like this sometimes pick up tiny scratches when they are first driven through their holes and this microscopic damage to the surface sustained when the boat was built creates the perfect conditions for crevice corrosion to start if moisture is introduced when seepage occurs. This is also true for rigging U-bolts where perhaps the pair of holes drilled through the deck do not quite line up with the shanks.
In fact it is a good idea to get this image fixed in your mind when inspecting parts of the vessel where stainless steel bolts are used.
Fig 98 shows the nut removed from the bolt in Fig 97. None of the corrosion evident on the back surface which could not be seen with the nut in position.
Another defect occasionally seen in nuts securing U-bolts is stress cracks in the wall. There are no other outward signs of deterioration in this nut (Fig 99) but the wall is cracked right through. Sometimes tapping the nuts inside the boat will cause them to disintegrate.
Fig 100 shows quite a common arrangement with a steel knee under the forestay fitting GRP bonded into the stem. Being in the anchor well this area is subject to damp with consequent corrosion. In Fig 100 it is obvious but less so is the fact that the stainless steel bolts pass through a plywood pad which will retain moisture and promote corrosion in the bolts when long term seepage occurs as has been the case here. Water will also run down the knee ending up at its base, causing heavy rusting and failure where it is bonded into the stem. A crowbar inserted behind the knee and used gently caused the base to pull out from the FRP bonding where it had disintegrated. Its function as a knee to transfer loadings away from the deck had long since ceased. Another worthwhile test.
Fig 101 shows a stainless steel nut on a rigging U-bolt where seepage has occurred over a long period. This is an extreme example of what can happen to stainless steel in this application but to get this picture it was necessary to remove linings inside the boat which had just returned from a 15 year circumnavigation. This is one of the U-bolts on the mizzen rigging of a ketch so it would be subject to severe loadings when the mizzen was used in heavy weather.
Although no ready access was possible inside the boat, applying the block and crowbar test to the U-bolt on deck immediately produced movement and water oozing out from under the deck plate, another example championing the value of a simple little test.
The nut is disintegrating and when the U-bolt was removed the shanks were found to be severely corroded. There has obviously been long term seepage here so it is essential to check that all deck plates etc which have a sealing function on deck are lying tight and fair to the deck. A feeler gauge is useful in this respect for pushing under fittings to find any gap, however small, where water might enter.
Obviously load bearing fittings such as this are always going to be subject to movement and seepage. Obviously when one component in a series of similar ones is found to be defective the recommendation is to dismantle them all for checking.
Fig 102 is an obvious example of a lifting chain plate but there is another sign here which should be recognised and appreciated. This is a load bearing fitting holding the rig up and the previous remedy for this serious problem has been to apply some filler around the plate. If this cavalier attitude to maintenance has been applied throughout the boat then the prudent surveyor or potential purchaser will be on high alert.
REPORT EXTRACTS
Severe crevice corrosion to rigging U-bolts shanks
All the other attachment points for both the main and mizzen masts consist of stainless steel U-bolts fitted through the deck or coachroof. Access was only possible to the following:
Mizzen port cap and aft lower shroud U-bolts accessible in port cockpit locker behind a wiring conduit. These are both partially GRP encapsulated and much staining and corrosion is evident (Fig 101). The photo shows the underside of one of the two nuts on the U-bolt and a good deal of corrosion is clearly present to the stainless steel. Under such conditions where oxygen is excluded but moisture is present due to seepage this type of corrosion is quite common, the threads inside the nuts and the shanks of the U-bolts where they pass through the deck being particularly vulnerable. The corresponding U-bolts on the stb side are entirely GRP encapsulated and no access was possible but aggressive non destructive testing on deck produced movement and evidence of seepage.
Recommendation: As described in the text good access inside the boat was only possible to three of the fourteen identical rigging attachment U-bolts. Having identified serious corrosion to one of these the remainder should be fully inspected. This will involve a good deal of dismantling to linings etc. (Subsequent dismantling revealed shanks of U-bolts near to failure.)
Severe crevice corrosion to rigging U-bolts fixing nuts.
Extensive brown staining is present to the underside of all the rigging U-bolts, backing plates and fixing nuts. When the nuts on the port capshroud U-bolt were gently tapped they broke into pieces.
Recommendation: All the rigging U-bolts should be removed for full inspection and replacement as required.
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• When inspecting areas such as this, do bear in mind that what may be elementary and obvious to you will not be so to a novice boat owner, or indeed a novice in charge of an experienced owner’s vessel. If an accident occurs you may find yourself being held liable if you have not identified obvious hazards etc.
• Adequate for vessel? If you do not lay out any chains for inspection link by link then record this limitation in the report. Check wear to any moving parts on anchors. Are any shackles used securely locked (moused) up to prevent the pins unwinding?
• For coastal and offshore the MCA harmonised code is useful for reference. If in the general preparation with the client you have established what kind of use he proposes for the vessel establish whether the ground tackle is adequate for that proposed use.
• Cleats, bollards etc secure? Adequate reinforcing in the laminate, backing pads etc? If of plywood beware of rot if the fixing bolts have been leaking.
• Provision to prevent chain jumping in heavy weather?
• Any winches secure and in working order? Electrics associated with any winch often located in damp anchor locker, any signs of corrosion?
• Common sense and observation should be sufficient here. Include more detail if client requires so, i.e. you have established a specific use for the vessel and have been asked to assess the vessel accordingly.
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• A common sense general appraisal is sufficient, the main criteria being security of all fittings and, for those with moving parts, mechanical wear.
• If highly stressed look for wear and fatigue cracks to stainless steel and aluminium components (particularly racing and blue water boats).
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• General condition and security. Working order?
• Does any folding ladder extend well below waterline to aid recovery of man overboard?
• Is the structure to which the above are attached strong enough? Look for stress cracks or fractures around davit feet, and adequate backing pads underneath.
