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These FAQs are designed to help you understand some of the issues involved with marine surveying, but there is no substitute for contracting a surveyor to see the specific boat that you are interested in. Neither the YDSA nor its members can be held liable for any of the statements contained in these FAQs.
To raise another query with our panel of expert surveyors, please email info@ybdsa.co.uk.
I am buying a new boat. Should I engage a marine surveyor?
How do I choose the surveyor I need?
I am buying a boat. What type of survey do I need?
Do all surveys give a valuation of the craft?
My broker has recommended a surveyor: is he the one to use?
My boat of choice has a Boat Safety Certificate, so I don’t need a survey.
I’ve found a boat that I love but the vendor is reluctant to dock the boat for survey.
What documentation should I expect to see?
How do I decide which marine surveyor to use?
My boat has been damaged in an accident. Do I need a marine surveyor?
I am unhappy with my boat yard. How should I proceed?
I have just bought a boat which needs quite a substantial refit. My yard cannot provide a quotation. How should I proceed?
We have a boat owned by a syndicate. Should a surveyor be engaged by the syndicate or the individuals?
How do I check that the surveyor has professional indemnity insurance?
What is different about an YDSA surveyor?
What is an ‘AFFILIATE’ YDSA Surveyor?
What is an ‘ASSOCIATE’ YDSA surveyor?
What is a ‘FULL MEMBER’ YDSA surveyor?
What is a ‘FELLOW’ YDSA Surveyor?
Can I attend the survey?
What preparations should I make for the survey?
I need to get my yacht surveyed but the marina can only lift the boat for an hour.
I need to get a narrow boat surveyed but the only available slipway in the area has a flat-bed trolley and the surveyor will not be able to get underneath all of the boat. Will this be a problem?
One of your members is booked to survey a boat for me next week but he is telling me that the report may not be ready until three days later. Do you have a member who could give me an instant verbal report so that I can complete on the boat that day if all is well?
Will a pre-purchase condition survey include a check on propeller shaft alignment?
I am proposing to buy a 1920’s Dutch barge. There are no suitable docking facilities in the area. Could the hull survey be undertaken by a diver?
What can I expect from a condition survey?
How do I proceed when I have decided that I would like to buy a boat?
What is osmosis?
I want to import a boat from abroad; does it need to comply with the Recreational Craft Directive?
I’m buying a narrowboat which has been fitted out by the owner. Where does it stand in respect of RCD compliance?
I am buying a new boat. Should I engage a marine surveyor?
There are two types of new boat purchase, the bespoke craft built to customer order and specification and the ‘off the peg’ craft which is a standard craft with some different specification options.
A marine surveyor can often be usefully retained as an owner’s representative to monitor a bespoke new build and can often also give a professional insight with regard to working practices and the quality of installations, and assist in problem resolution during the build, often relying on a wider technical experience to assist both the builder and the buyer to reduce the compromises often accepted by the buyer. The surveyor may also be able to draw on a wide experience of on-board equipment and offer guidance on the equipment type and manufacturers which you should specify.
Whether the purchase is a bespoke craft or one which has a standard specification it may well be particularly useful to engage a marine surveyor to carry out a pre-delivery inspection or snagging prior to handover.
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How do I choose the surveyor I need?
Clearly you are on the right course since you are reading this. YDSA surveyors are encouraged and trained to provide an unbiased, factual and true opinion on a boat’s condition, and its valuation if asked.
All our members are listed in the membership list on this website, together with their grades of membership, which are representative of their experience.
You should always use this list, or the listing in our free year book, to choose your shortlist of surveyors. Location should play a part in the selection of your surveyor, but it should not be the main factor. Different craft types and different materials require different surveying techniques, equipment and experience, so be sure to discuss the craft with any surveyor that you contact and ask them about their experience with that craft type and construction material. Then talk to the chosen few and establish which has the best approach for your needs, and with whom you can establish the best rapport. Remember that differences in fees pale into insignificance compared with the quality and value of the advice that you are likely to achieve, and probably the value of the boat.
If you are buying through a yacht or boat broker, be aware that the broker’s priority is to sell the boat for his client and earn his commission. Do not rely on a broker’s list of surveyors. The list may or may not be compiled on the basis of which surveyors give the broker the easiest ride to his commission, which might not be in your best interests. Look at all the alternatives on the YDSA listings and don’t be frightened to talk to several surveyors, especially if your proposed purchase is old or of unusual construction.
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I am buying a boat, what type of survey do I need?
Before Buying - If you are intending to buy a boat, new or old, then a Full Condition Survey is probably the most appropriate survey, which is often known as a Pre-Purchase survey. If you are intending to obtain finance against the craft then you may need to also have a valuation of the craft completed as a part of this survey.
Some surveyors, but not all, also offer a limited scope survey which may be external hull inspections, an osmosis check on GRP craft, an engine survey or a mechanical and systems survey.
Although limited scope surveys may be less expensive than a more comprehensive survey it is very important that the commissioner understands that they are limited scope and that if additional surveys are then commissioned the cost of the separate surveys will exceed the cost of a full condition survey conducted as one instruction.
It is also advisable to explore the costs and terms of craft insurance as the survey requirements of insurers can differ and to find you need additions to the survey you have already had completed can involve additional costs.
For Insurers – It is normal for craft insurers to require a craft to be surveyed in order to establish its condition before they will write cover. These surveys can range from full condition to hull only and in some cases can be a survey of repairs after a craft has been repaired following damage.
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Do all surveys give a valuation of the craft?
Many surveyors treat the subject of valuation in many different ways. It is unlikely that a survey will automatically include a valuation unless you have specifically requested one and the surveyor has agreed that he is happy and able to supply one, in which case valuations are generally given as an approximation or estimate.
Some surveyors will charge an additional fee for giving a valuation and others may include it within their standard survey fees.
The “Value” both for purchase and insurance purposes is the price that a willing buyer will pay a willing seller. It follows therefore that a keen buyer who has researched the market thoroughly will have perhaps the most up to date knowledge of likely value in the particular sector involved, but a surveyor will also be able to offer worthwhile input, with more access to comparables and links to other colleagues, both surveyors and brokers.
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My broker has recommended a surveyor: is he the one to use?
Brokers will be well aware of the surveyors in their area, and out-of-area specialists, and may supply a list, but it should be your choice when selecting a surveyor. Bear in mind that an out-of-area surveyor may manage to be more independent than one whose office is on the marina.
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My boat of choice has a Boat Safety Certificate, so I don’t need a survey.
Wrong. The Boat Safety Scheme is intended to protect the interests of Third Parties, i.e. walkers, anglers, gongoozlers and other boaters. The inspection does not cover hull condition, skin fittings, bilge pumps, stern gear, steering gear or structural condition in general. The scheme majors on matters of perceived duty of care on the part of the navigation authorities, namely fire, explosion and pollution risk. Be aware also that many certificates are issued by individuals with little professional marine experience or training and no affiliation to respected maritime organisations.
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I’ve found a boat that I love but the vendor is reluctant to dock the boat for survey.
For a boat of any age a survey is really essential. It may major on hull condition, or compliance with standards. A professional surveyor will know where to concentrate his efforts.
If your vendor is reluctant to permit a survey, or imposes obstacles, you have to ask yourself why. Does he want to sell, or what is he hiding?
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What documentation should I expect to see?
This is a complex subject and certainly for higher value vessels a suitably experienced solicitor should be involved. YDSA has Subscriber Member specialist marine legal firms that can be highly recommended and we will be pleased to supply a choice of names.
It must be understood that under maritime law a vessel takes its debts with it. If you buy the boat with an unsuitable Bill of Sale then you could find yourself liable for previous finance debts, mooring and repair bills and so on.
It is essential to establish that the vendor has proper title to sell. A UK Part 1 registered vessel carries some degree of guarantee as to title and liens, but many vessels are not Part 1 registered. Small Ships Registry or Navigation Authority registrations are not the same and offer no statement as to title.
If you are dealing through an ABYA broker then the broker will cope with the legalities and ensure that the vessel is transferred free from debts and encumbrances. Non – ABYA brokers rarely offer this service commitment. If you are not dealing through an ABYA broker then you or your solicitor will have to do it. In the case of an unregistered vessel the most you can do will be to obtain possession of the best possible paper trail linking the vendor to the boat, meaning previous bills of sale, mooring and insurance receipts, repair receipts and so on. You have to convince yourself that the vendor has title to sell.
A YDSA surveyor will not usually be qualified to offer legal advice, but will usually be able to spot the alarm signals.
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How do I decide which marine surveyor to use?
Because there is nothing to stop anybody describing themselves as a ‘Marine Surveyor’, membership of a genuine long established professional association such as YDSA is very important.
All YDSA surveyors are required to demonstrate competence and experience in the industry, to achieve a minimum level of Continuous Professional Development and to carry a specified level of Professional Indemnity insurance. All applications for entry and upgrading are carefully vetted by the surveyor’s peers. Disciplinary procedures are in place in the case of any alleged failure in professional conduct.
There are very many different types of craft and build materials each of which requires a different surveying technique and specialist experience and equipment, so it is important to ensure that the surveyor has the appropriate experience or expertise.
Although the location of the surveyor to the craft to be surveyed should be considered as a cost factor it is often better to consider the surveyor’s expertise and pay the right surveyor to travel to get the depth of survey that you require. Travel costs may be a factor, but the availability of the right experience will almost certainly outweigh cost disadvantages. It is also worth considering where the craft is likely to be based, especially with regard to pre-purchase surveys, for example if the craft is to based in Scotland but is lying on brokerage in Southampton there may be merit in selecting a suitable surveyor from near to the intended home berth, which will reduce future costs if a continuity of survey is to be required for future surveys for insurance, or assistance with repairs.
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My boat has been damaged in an accident; do I need a marine surveyor?
If your craft is covered by insurance then your insurance company is likely to instruct an independent marine surveyor to obtain details of the incident and to asses the extent of any damage to a craft. Though independent in this situation the surveyor’s client is the insurer, to whom he must report. If you think that that there is a need, or if you are not comprehensively insured and you think that a third party may be responsible for the incident or damage, then you might want to consider engaging an independent surveyor in order to look after your own interests.
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I am unhappy with my boat yard’s performance. How should I proceed?
If you have any concerns about the work being done you should engage an independent professional surveyor as soon as possible. A lot will depend upon your agreement with the yard, viz. contracts, estimates, quotations and variations, but an independent surveyor may well be able to help significantly, particularly if there has been a breakdown in relations and emotion has crossed swords with business. YDSA office staff know all their members and will be able to suggest a choice of suitable names to help you.
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I have just bought a boat which needs quite a substantial refit. My yard will not provide a quotation. How should I proceed?
Be very wary. The yard may not be able to assess the exact extent of works necessary since, in the case of an older boat, there may well be other deficiencies in the boat which were not discoverable under survey and only become apparent when structures are opened up. It is not unfair therefore for the yard to be reticent about committing to a price. What you must do is obtain base line figures, such as labour rates and background expenses such as hard standing. Ensure that the yard keeps you fully informed of any new discoveries, and maintains a variations notice on a weekly basis, to be signed off by you, so that you can keep track of the costs involved in additional works or changes to the specification. You may be well advised to retain a local surveyor to keep an eye on the works and the costs. Be aware also that costs can escalate if the boat is not worked on continuously. “Hospital Jobs” often end up costing more.
It is vital that a written specification is agreed, and priced as far as possible. If certain areas can be priced then that sets a benchmark for the other areas, and the unforeseens that cannot be priced in advance.
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We have a boat owned by a syndicate. Should a surveyor be engaged by the syndicate or the individuals?
It would very much depend on the nature or arrangements of the syndicate. However the engagement of an independent marine surveyor by the syndicate as ‘Craft Superintendent’ may well be of value to the syndicate members as individuals and as a whole. The role of the surveyor can be to assess the craft at regular prearranged intervals and deliver the syndicate with ongoing maintenance recommendations, and observe that they have been completed to an appropriate standard to keep the craft in the desired condition.
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How do I check that the surveyor has professional indemnity insurance?
You should only use surveyors who have Professional Indemnity (PI) insurance, so it may seem sensible to ask them, but most surveyors will be wary if this is your first question! It is normally a clause in PI policies that its existence is not disclosed or discussed by the holder. However all YDSA surveyors must have suitable PI cover as a requirement of membership.
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What is different about a YDSA surveyor?
Membership of some surveyor organisations is automatic after distance learning courses or academic achievement only. YDSA surveyors usually have a background in boat building, design or repair and have learnt their profession over many years of hands-on experience. The stringent application assessment includes a formal examination in most cases. Every applicant has to provide a number of references from respected peers or industry figures and their surveying work is assessed by a membership panel of senior surveyors, often followed by an interview. We value down to earth practical experience more than paper “Diplomas.” Membership standards are at such a highly respected level that many applications are not successful first time and some Mentoring or further training assistance is offered. Most insurers and legal firms will only use YDSA members.
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What is an ‘AFFILIATE’ YDSA Surveyor?
The normal entry level to surveyor membership is that of ‘Affiliate’. An Affiliate Member is not allowed to advertise their membership of the association and, whilst already a practising surveyor, an Affiliate will generally be a less experienced surveyor than would be included in the upper grades of membership.
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What is an ‘ASSOCIATE’ YDSA surveyor?
An Associate Member is an experienced surveyor, producing good work and with suitable expertise and qualifications, such that the Association is happy for that person to advertise their membership.
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What is a ‘FULL MEMBER’ YDSA surveyor?
A Full Member is likely to be a person with a lifetime experience in the industry, highly qualified through sheer experience or academic achievement or both, with a high reputation and very significant expertise. It is the highest grade of membership awarded on the basis of professional experience, expertise and merit.
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What is a ‘FELLOW’ YDSA Surveyor?
YDSA Fellow surveyor status is an award in recognition of services to the Association. It is unusual for a Fellowship to be awarded to a member who has not already achieved the status of Full member. Whilst not awarded on the basis of professional merit the grade does reflect the fact that management experience within the Association is generally mind broadening in respect of the practicalities of the profession.
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Can I attend the survey?
Individual surveyors have different policies, but in general it is best to leave the surveyor to get on with his job undistracted. Most surveyors will be happy to discuss the principle findings on completion of the inspection but the purchase should not proceed until the full and considered written report has been received and read, and any concerns discussed with the surveyor.
The presence of the vendor can also be received with varying degrees of enthusiasm. The vendor may be able to help with technical and systems information, but can also be a distraction.
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What preparations should I make for the survey?
Ensure that the boat is going to be presented in accessible condition. It almost certainly needs to be out of the water and should be securely propped or supported ashore or in dock in such a way that access is available to as much as possible of the hull. Surveyors, by dint of experience and thus age, may not be athletes and humane access will produce the best possible job. Safety is also an issue now, and access and security must be addressed by the yard.
The interior should be cleared as far as possible of effects to allow access into lockers, around the engine etc. Sails should be spread out, anchor cables ranged and systems should be presented in commission if you wish the surveyor to check these. The boat should be presented in a clean and hygienic condition respecting the health of the surveyor.
These preparations are really in the province of the vendor or broker. Don’t be afraid to press the vendor to make the necessary preparations, presuming they want to sell.
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I need to get a yacht surveyed but the marina can only lift the boat for an hour.
It will depend to some extent on the boat but a one hour time limit is very often not adequate. Your surveyor needs to be able to expend whatever time is necessary in assessing your boat and the imposition of time limits does not encourage careful contemplation or in many cases allow a thorough job.
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I need to get a narrow boat surveyed but the only available slipway in the area has a flat-bed trolley and the surveyor will not be able to get underneath all of the boat. Will this be a problem?
For the best possible survey the boat should be presented in such a way that a surveyor can physically get underneath the boat in reasonable working conditions, and gain access to as much of the underwater plating as possible. Even in the most ideal conditions there will always be some areas that cannot be inspected, such as where the boat is sitting on dock baulks, trolley support, props or hanging in slings. It is a fact however that many inland boatyard slipways and dry docks are simply not designed or built to provide proper access to the bottom plate. In the old working boat days this was still often the case but if the bottom needed repairs the boat would be jacked up and tipped over at a 45 degree angle. That is hardly possible for a modern narrow boat where somebody is living on board with all their worldly possessions!
The adequacy of many of the facilities available depends a lot on the type and age of the narrow boat. If it is a relatively recent build (say within the last ten years) and has been built with the now normal and generous 10mm thick bottom then significant corrosive deterioration of the plating is very unlikely, although moderate pitting will almost certainly have occurred. The most likely bottom plating deterioration will be wear at the chines, and even with no access underneath, or if sitting on a flat-bed trolley, the surveyor will usually be able to see whether significant wear has occurred. Inboard of the chines significant wear is unlikely, although that situation could be less certain if the boat has been a hire boat for any length of time.
You may well ask whether in the case of a boat of this age and build whether an out-of-water survey is worthwhile. It almost certainly is because the surveyor will be able to inspect the sterngear and propeller, rudder and skeg. He will be able to make an assessment of anode condition and offer an opinion on the levels of active galvanic or electrolytic corrosion. He will also be able to accurately measure the beam of the boat, and it is amazing how many are over width.
If the boat is an older boat and has a 6mm bottom then it becomes quite important to see the bottom. If for example the boat is on a flat bed trolley then it may be the case that the bottom at the ends of the boat can be inspected, but not the middle section. Providing that key areas, (such as that immediately forward of the after cabin bulkhead where water can lay trapped and cause significant internal corrosion) can be assessed then on the basis of what can be seen at the ends it might be reasonable for the surveyor to hazard an opinion on the probable condition of the hidden area, but of course there can be no guarantee. There remains the risk that enhanced corrosion in areas such as under the shower may remain undetected. A better dock or slipway facility should be considered if the option is available.
In the case of a vee-bottomed boat such as a Springer access to the bottom along the centreline is essential. Water can lay trapped in this area and cause significant corrosion from the inside. Good access is essential and a survey conducted with the boat on a flat bed trolley, or in a shallow dock, will not be an adequate job.
All the above presumes that the boat in question is from a known and proprietary builder. If the boat is of unknown pedigree then good access may again prove essential for a proper job to be carried out.
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One of your members is booked to survey a boat for me next week but he is telling me that the report may not be ready until three days later. Do you have a member who could give me an instant verbal report so that I can complete on the boat that day if all is well?
We would not wish any of our members to operate in that way. A survey is often a physically and mentally arduous job, at the end of which your surveyor has every right to feel exhausted and brain dead. He will not necessarily be in any condition to reflect on all his findings and advise you in comprehensive and considered fashion. Quite often “pennies drop” as the surveyor drives home or prepares his report. Two or three symptoms that might initially have seemed unrelated might transpire to be linked and significant. He may want to revisit the boat. Any verbal résumé will depend upon the surveyor’s judgement of your priorities, and something that may be particularly important to you may not therefore be mentioned, whereas the full story will appear in the report. Your surveyor may also need to make further enquiries or seek another opinion on particular matters. If a Valuation is involved he will often need to check his database, research comparables and score his findings.
A reputable broker should allow a reasonable time for the report to be considered and composed, and for you to read and consider that report and raise any necessary questions with the surveyor. If you are being pushed to complete you need to ask “why.” If on the other hand you have compelling personal reasons to complete on the day then that must be at your own risk.
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Will a pre-purchase condition survey include a check on propeller shaft alignment?
A normal pre-purchase survey is a non-invasive, non-destructive inspection of the vessel. With the exception of moisture meters and ultrasonic plating thickness meters most surveys major on a careful visual inspection. Most vendors will not permit their boats to be taken apart. You do of course have the option of asking your surveyor to carry out specific tasks, and, with the permission of the vendor and subject to the attendance of a shipwright or engineer to carry out any necessary opening up, then these wishes can usually be accommodated. This does however fall outside the scope of the most normal pre-purchase survey.
In respect of the particular question of propeller shaft alignment it must also be appreciated that in many case it is simply not possible to check the alignment readily. Many flexible couplings do not permit a proper alignment check to be made without suitably accurate dummy solid couplings being available. An alignment check with the boat ashore is worthless. If there is any wear in the shaft bearings then an alignment check will be worthless.
Presuming that the boat can be inspected in the water as well as ashore then your surveyor will be able to run the engine(s) up or sea trial the boat and, as part of his overall assessment of running characteristics, he should be able to observe whether any of the symptoms of misalignment or bend in the shaft are evident, for example overheating of the stuffing boxes or eccentricity in the shafts. This is about as far as it is reasonably practical to go without drawing the shaft(s).
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I am proposing to buy a 1920’s Dutch barge. There are no suitable docking facilities in the area. Could the hull survey be undertaken by a diver?
In the case of a relatively modern welded steel or aluminium vessel it is often possible to carry out a reasonably adequate survey of the hull plating, anodes, sterngear etc. with the vessel in the water subject to suitable conditions being available, i.e. still clear water, minimal sediments etc. Point ultrasonic measurements can be taken and a visual and tactile examination for pitting will be possible. It will not be reasonable however to remove coatings since these cannot be reinstated, so the level of pitting and active corrosion cannot be assessed. Hammer soundings will not be possible. It also becomes much more essential for there to be good internal access to most, if not all, of the internal plating and framing surfaces since localised internal corrosion deficiencies that could be detected by external hammer soundings with the boat out of the water may not be discovered with the vessel afloat except perhaps by chance. The conditions will never be as good as if the vessel were presented out of the water. The survey cannot therefore be as comprehensive and will be intrinsically less reliable. An in water survey of any vessel should only be treated as a last resort where an out of water inspection is totally unviable or impossible.
A 1920’s Dutch barge will be of riveted construction and the older metal is likely to be rather incompatible with ultrasonic thickness meters, which are designed for modern, homogeneous mild steel. Ultrasonic measurements often need interpretation using hammer soundings (which are not possible afloat). A proper visual inspection is far more important. The hull is much more likely, on grounds of age alone, to be suffering localised deficiencies which a general and necessarily random ultrasonic thicknessing exercise is unlikely to reveal. Again extensive internal access will be necessary and all the other limitations described above will apply.
We cannot therefore recommend in-water hull surveys unless there are very compelling reasons, and the potential severe limitations in the accuracy of the survey must be respected.
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What can I expect from a condition survey?
The full condition report will give brief details to identify the craft – name, type of construction, year of build, registration number if applicable and will outline the extent or limitation of the inspection. This is followed by a full description in itemised form of the defects together with recommendations for remedial action and generally includes the following main areas:
Hull underwater
Machinery
Keel
Skin fittings
Rudder
Deck fittings
Sterngear
Mast, Boom and Rig
Topsides
Gas Installation
Deck, coachroof and cockpit
Water
Steering
Fuel
Hull internal
Electrical Installation
Bilge
Anchoring and Mooring
Hatches and Doors
Sails
Windows and Portlights
As the title implies the Full Condition Survey is intended to identify all defects and deficiencies which might be discernible by a competent surveyor i.e. a YDSA Surveyor.
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How do I proceed when I have decided that I would like to buy a boat?
The following format is usual when purchasing a vessel.
Contract to Purchase - An offer is made subject to survey and a deposit paid to the broker or vendor after which the surveyor is instructed.
Contract with the Surveyor - The purchaser should take personal responsibility for selecting and instructing the surveyor. Do not allow the vendor or broker to choose or instruct the surveyor. It is advisable to discuss fully with the surveyor any particular concerns or special requirements that you may have before the surveyor inspects the vessel. Ensure that the surveyor is competent for the type of vessel involved. Talk to the YDSA office in doubt. Our staff know all the members and will be able to offer discrete advice.
The vessel must be out of the water for a condition survey to be carried out. All boatyard and other costs in connection with the survey are in addition to the surveyor’s fees and expenses and are the responsibility of the purchaser.
The Inspection - The surveyor will carry out his inspection of the vessel as presented and in this respect the purchaser can assist the surveyor and help to procure a more complete report by arranging the best possible access to the vessel. It is not the surveyor’s responsibility to carry out a de-storing and tidying exercise. In a vessel lined with an internal moulding, preventing access, then clearly no internal defects of the hull shell can be identified and any problems could only be identified by external inspection.
The Survey Report - This will list the defects found in the survey together with recommendations and suggestions for repair and remedial work. The written report may be used to negotiate final purchase arrangements. Survey reports issued by YDSA surveyors are recognised by leading insurers, marine finance companies and banks.
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What is osmosis?
The problems start to occur when the water molecules migrating into the GRP encounter other chemicals inside the laminate, primarily water-soluble materials (WSMs) such as the the emulsion binders used to hold the glass mat together before it is moulded, or pockets of uncured or only partly cured resins in the moulding. The water molecules can then have a chemical reaction with these substances, forming larger molecules of a new chemical, often acidic - which unlike the original small water molecules, cannot carry on passing through the GRP. These larger molecules are then trapped. This is the point at which osmosis actually starts.
The important parts are that the hull is not waterproof (it is a semi-permeable material), and that osmosis causes a low concentration fluid (water) to pass through the hull to join the higher concentration fluid (the chemical mix formed by the water plus WSM) inside the laminate).
Pressure is thus built up inside the laminate. If this process takes place in a solid part of the laminate, there is usually no problem as the structure is strong enough to contain the pressure. If however it takes place on the boundary of a small air-bubble in the moulding, or at a point where layers of GRP are poorly bonded, the resultant new chemical compound or compounds slowly fill up the bubbles or the minute gaps between layers with liquid. Almost all mouldings have these air bubbles and small areas of poor bonding, although they should not. Ideally the resin should totally fill the gaps between the glass strands, and every layer should perfectly bond to the next. In practice, however, this is extremely difficult to achieve with conventional moulding techniques. The process of osmosis in GRP is however very slow, unless the moulding is appallingly badly made, and no matter how long it remains in water a typical GRP laminate cannot absorb more than about 2-3% of it’s own weight of water.
If this osmosis (using the term in it’s correct manner for once) was all that happened, it would be a very minor problem. Even completely saturated with water molecules, a GRP laminate still retains most of it’s strength, although it does become slightly more flexible. Racers who want stiff hulls with the absolute minimum weight already mostly keep their boats ashore when not sailing, and for any properly built cruising boat 2% or so extra weight and a trace more flexibility in the structure should not be a problem.
Once again, if the air bubble simply filled with this acidic compound, the problem would still be relatively minor. However the nature of the osmosis process is that water molecules keep osmosing through the laminate, and join the chemicals in the bubble, steadily building up hydraulic pressure. Eventually this causes the surface of the moulding to blister.
These blisters are the typical sign of what boat-owners usually refer to as ‘osmosis’. When pierced these blisters will give off a small amount of chemical-smelling (usually vinegary) liquid - which is the juice built up inside the pressure-raised blisters. The term ‘blister juice’ is often used. This ‘blister juice’, which is usually acid, can break down the polyester. This breakdown process is known as hydrolysis, and causes a reduction in strength of the laminate. This is however normally very localised, and the moulding as a whole will still retain most of it’s strength despite blistering. Only if the blisters are very large, or very deep-seated, is this generally a problem
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I want to import a boat from abroad, does it need to comply with the Recreational Craft Directive?
The short answer is ‘YES’ if the craft is being imported from a country outside the European Economic Union. Any craft first put into service or on the market after June 1996 as a recreational craft within the EU must be compliant with the Recreational Craft Directive.
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I’m buying a narrowboat which has been fitted out by the owner. Where does it stand in respect of RCD compliance?
A vessel that has been supplied as a shell, or a “sailaway,” or indeed built from scratch by a home builder, can be exempted from the certification and documentation requirements of the Recreational Craft Directive provided that the builder retains ownership of the vessel for at least five years from the date that the vessel was first “placed into service,” meaning the point at which the boat was capable of performing its designed function. In most cases this would mean completion to the extent that the boat could be cruised, with berths, cooking and sanitation facilities.
Any home builder selling within the statutory five year period would be committing a criminal offence. A knowing buyer could be accused of aiding and abetting the offence, although this is unlikely. The real point is that the vessel’s documentation would be incomplete, which could be a problem when selling on.
If contemplating buying a home completed vessel which may not have been completed more than five years ago some form of proof should be sought. Home builders would be well advised to instruct a surveyor to provide a completion certificate once they have completed their project, since that is when the clock starts ticking.
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