Boat inspection are crucial for ensuring a vessel’s safety, performance, and compliance with maritime regulations. During an inspection, key areas such as the hull, engine, electrical systems, and safety equipment are thoroughly examined. Inspectors check for structural integrity, signs of damage or wear, and proper functionality of mechanical and electrical components. This process includes assessing the hull for cracks, the engine for leaks and proper operation, and safety equipment like life jackets and fire extinguishers to ensure they are in good condition and up to date.
Additionally, a boat inspection often involves a sea trial, where the vessel is taken out on the water to evaluate its handling, engine performance, and overall seaworthiness. For sailboats, the inspection includes checking sails, rigging, and winches. Regular inspections help maintain a boat’s value and ensure it remains safe for passengers and crew, reducing the risk of accidents or costly repairs.
UNLESS YOU’RE IN the market for buying a second hand boat, it’s not usually good news when you have to call in a surveyor. They may be brought in to assess damage to your boat after an accident, or the insurance company might demand a survey when your boat reaches a certain age (usually around ten years) just to be sure about its condition. When you are buying second hand you certainly want a survey done before you commit. So the surveyor’s job, whether it is a purchase or insurance survey, is to use his specialist experience and skill to go through the boat with a fine-tooth comb, find any problems and propose solutions. For a damage survey the motivation is obvious but the surveyor will also assess the general condition in case that falls below what might be considered to be an insurable standard.
To a certain extent the surveyor is a bit like a detective. He will crawl round inside and outside the boat inspecting the fittings, fixtures and the hull itself to find the clues that will determine whether the boat is in sound condition or where any problems lie. It can be a difficult job at times because these clues are sometimes quite small and apparently insignificant, and it is only by putting them all together that the surveyor can assess the condition of the boat. He will use sight, feel, often smell and sometimes instruments to determine what may be wrong. It can be a challenging but fascinating job and, like so many jobs of this nature, it’s a constant learning curve, as construction methods and materials for boats develop.
When damage has occurred or when the insurance or finance company has demanded a survey, you will want to use a professional surveyor. You will probably also want to employ a surveyor to give you a report before you make a final decision on your next boat, but a good quality survey does not come cheap. If you’re considering several boats before finally deciding on the one you want, you could run up a considerable bill. Owners will want to carry out their own survey to avoid such costs where possible.
Carrying out Professional Advice Consultations on the Marine Boat Surveya survey on a boat has always been something of a mysterious art and there is no doubt that skill and experience is required. However if you are prepared to get a boiler suit on and enter the normally unseen parts of a boat you can carry out a survey yourself. You may not have the professional experience but there are usually plenty of clues to help you pinpoint areas of concern.
This article is aimed at the owner or potential owner who wants to be able to carry out a basic survey. It should help you find potential problems in your own boat and get them fixed before they become serious.
And if you’re buying, it should guide you through the survey process with enough information to decide whether to go ahead with the purchase and get the professional in (or walk on to the next boat on your list).
The buyer’s survey
WHEN YOU ARE buying a second hand boat there is no reason why you should not do your own preliminary survey. You may not discover all the problems that a professional would but at least you should be able to spot areas of concern that may convince you to avoid a certain boat.
By discovering problems at this early stage of the buying process you can rule out some of your potential purchases yourself, and save a great deal of money on professional surveys before you find a boat that looks to be in a suitable and reasonable condition and warrants a professional opinion (both to reassure yourself and possibly your finance company and insurer).
There will rarely be time for you to do a full survey when you are assessing potential purchases; the yacht broker or the owner isn’t likely to want you to spend hours crawling around their boats. If you want to look at several boats before deciding, you need to be able to do a sort of preliminary survey, one that should throw up any major faults or at least give you an idea of how the boat has been maintained over the years.
The tools to do this will be covered in future articles. Professional surveyors may throw up their hands in horror at this approach but it is a pragmatic solution to what could be quite a difficult problem for potential purchasers. It is no substitute for a much more detailed survey, either by you or a professional, but it should enable you to decide whether to take a more detailed look at a boat or walk away.
If you have done your own survey on a boat and identified faults that you are reasonably comfortable with and willing to accept when you make the purchase, you will also have a yardstick to judge the quality of the professional surveyor’s report. Hopefully he will have noted all the things that you found wrong and probably a few more besides, but you are now in a position to make a judgement about the quality of his survey if he doesn’t uncover some of the issues that you found. It has been known.
The owner’s survey
IF YOU ARE already the proud owner of a boat then being able to carry out a survey yourself can be very rewarding. This could be something that you do on an annual basis, perhaps just before you lay it up for the winter. You will probably already have a list of things that need attention but this will develop from what you see and learn from operating the boat.
If you spend a morning doing your own survey, not only will you be able to put together a more comprehensive list of things that need fixing but you’ll also have a lot more confidence in your boat the next season. Furthermore, not only will you get to know what makes your boat tick, but this detailed knowledge will stand you in good stead should you experience an emergency out at sea. If you find the water levels rising inside the boat in lively seas you’ll have a much better idea of where to look for trouble, how to get access quickly and where the seacocks and the piping are.
Everybody should know their boat in this detailed way but in practice very few do. When you have an emergency on your hands and quick action is needed, the last thing you want to be doing is getting the manual out and flicking through its pages.
Of course, if you do a survey you should be less at risk of having an emergency at sea in the first place.
Getting access
WHEN YOU’RE CARRYING out a survey you can only examine what you can see. This may sound like stating the obvious, but a professional surveyor’s report itemises the areas where examinations have been carried out and where lack of access has made this impossible. He does this to cover himself because you cannot give a blanket assurance that all is well unless you have inspected every single part of the boat, and in most cases this is just not possible because of the way it has been put together.
Modern yachts tend to be assembled for the convenience of the builder rather than to give the owner or surveyor access: the trend is to fit an inner moulding inside the main hull moulding, so unless you cut sections out there is simply no way to inspect the hidden areas inside. The professional surveyor covers himself by using phrases in his report such as «the hull was in sound condition where examined».
You have to do much the same when it comes to undertaking your own examination. Obviously, open up all the hatches and access panels as far as you can and if you find that the bits you can see are sound, you can be reasonably comfortable that the hidden areas are sound too. It’s not a 100 percent guarantee but it’s the best you can do short of ripping the boat apart. To overcome some of the access problems the professional can use mirrors and/or cameras. A mirror on a stick, rather like an overgrown dentist’s mirror, allows the surveyor to see into many hidden areas. Using it, and getting light into the area, does take some skill but it does help to open up areas that would otherwise be hidden.
I used this technique once when there was a leak from a generator exhaust pipe hidden behind the fuel tank, and the camera showed up the salt encrustation that was a sure sign of a leak. While it didn’t provide the cure, at least we knew what the problem was.
You can also do a survey when a boat is afloat, but you won’t be able to do a full job. Bear in mind that your survey is aimed at checking the areas of the boat that you don’t normally see. This includes the underwater areas, and as fittings such as the propeller and the rudder can be vital to your safety these should be a priority in any survey.
You’ll need to get a close look at how fair the hull shape is so that any distortions are apparent. On a sailboat you also need to be able to inspect the keel or centreboard. This is where wear and tear can occur without you being immediately aware of it, so get the boat on dry land, preferably on a hard standing and securely chocked up, because you will be crawling underneath it.
Surveying skills
WHAT SKILLS DO you need to carry out your own survey? first you need to be reasonably agile, because you’ll be crawling in and out of tight spaces. Most boats were never designed with easy access to the hidden parts in mind – when I was surveying, I often found it relatively easy to get inside a compartment but much trickier to get out again! – so you have to make the best access provisions that you can and, again, you can only survey what you can see.
You need to use all your senses on the survey, except perhaps taste, but the most important attribute is having the patience to carry out such close examination. Of course experience counts when doing a survey, but what it mainly does is allow you to quickly find the source of a problem. A professional surveyor develops the instinct to anticipate certain faults, but those new to surveying need to go slow; it is all too easy to give areas of the hull a cursory glance and think that you have checked them out but this won’t catch the often tiny clues: minute cracks or discolouration that should make you stop and explore the area in a bit more detail.
When you are surveying your own boat you may find it harder to be objective. At the back of your mind is the thought that you don’t really want to find any problems because you’ll then have to deal with them, and that’s likely to cost you money. But you should resist the temptation to gloss over areas and, believe me, it can be quite tricky. It’s so easy to pretend that there isn’t a problem when you don’t want to see it, and I have come across owners who have even installed new fittings onto sections of the boat that were deteriorating.
When you do come across something you don’t understand or which looks like it may require a significant repair, it’s time to call in the experts, maybe an independent surveyor who can give his opinion or a boatyard you want to approach about the repair. I would like to think that the boatyard opinion, as well as being free, would be unbiased but they may be keen to get the work, so they’re not always completely objective. You will have to pay for an independent view from a surveyor and, like most things in life, you get what you pay for. If you spot a problem on a boat that you are considering buying, the simple solution is to walk away and continue your search elsewhere.
This is the pessimistic view and there is every chance your own survey won’t throw up any major problems. Instead it should give you the confidence that you know how everything works and operates and that your boat is sound for another season. A boat is a very personal thing and carrying out a detailed survey will enhance your relationship with it.
The Tools of the Trade
THE TOOLS YOU need for carrying out your own survey are very simple and the chances are you’ll already have most of them. You might see the professional surveyor carrying a hefty tool box around with him but he has to cater for every possible requirement, and your survey will follow a more simple route. Before we look at the actual physical tools it is worth reiterating that some of the most important assets for assessing the condition of a boat are your five senses, so let’s have a quick look at how you use them.
Using your senses
OF ALL THE senses, touch is probably the most important to the surveyor. Run your fingers lightly over a hull or deck surface and you’ll quickly become aware of imperfections, roughness or distortions. You may be able to feel an area of slight change or rise in the surface where a repair has been carried out on a composite hull and the old and new material joins. You will certainly be able to feel chips and scratches. When you’re checking out the wire rigging on a sailboat (wearing a pair of good leather gloves) you’re running your hands up and down the wire to try and find any broken wires.
Sight is probably as critical as touch when it comes to first detecting then analysing any problems. A professional surveyor’s first step may be to simply stand and look at the boat, and with experience you may also learn where to look for trouble spots without even getting close to the boat. Look for tiny cracks, changes in colour or other imperfections. A magnifying glass helps, especially when examining the reinforcing material below the gel coat on a composite hull, so make it part of your tool kit. Binoculars also help you to get a closer look at difficult areas such as the top of the mast, if this is erected during the survey. You might also want to use mirrors in one form or another (see here). Sight is also your first line of defence if there is a distortion in the hull: do both sides look the same and is the rudder in line with the keel? anything that seems a bit out of kilter should be suspect (it is easy to overlook such major discrepancies when focusing on the finer points of a boat’s structure).
Sound comes into play as you assess the hull and fittings because you can use light taps with a hammer (or even your knuckles) to identify areas with a different composition (such as «sandwich» construction) and possible deterioration: good condition material should «ring», while suspect material gives off a softer, duller sound. This simple technique works on many parts of a boat, including the hulls and decks of composite boats, keels and keel bolts and in fact most parts of the structure that should be rigid and taut. Even a wooden hull should have that same sort of «ringing» sound if it’s in good condition.
Every boat has a unique smell, which may be compounded by water in the bilges, styrene in the laminate of a composite moulding (although this is only likely in newer boats), rot in a wooden hull, leaking toilets and other outlets, engine and diesel oil, and many other causes. You need experience to successfully exploit your sense of smell during a survey, but once you’ve seen dry rot, you’ll remember what it smells like for a long time! So don’t ignore your nose; even if at first you can’t identify the smell, take the trouble to try and pin down the cause because in most cases a bad or noxious smell indicates some form of defect – there was a time when boats would smell of the materials used in their construction, such as pitch and tar, but apart from the styrene smell, a new boat should be free from significant odours.Using your sense of taste is something you want to do with considerable care, and only to differentiate between fresh and salt water to help determine where a leak is coming from. However, any water on board can be contaminated so tasting it should be a last resort. Certainly if we were to exclude one of the senses from the investigative process, this is the one, so use it at your own discretion.
There can also be a sort of sixth sense, a «gut feeling» that indicates potential trouble ahead for a particular boat. It may be hard to put your finger on just what it is, but don’t ignore the warning signs – they’re usually right.
Tools
NOW IT’S TIME to turn our attention to the hardware a surveyor might use. The aim of any survey is to assess the condition of the boat without causing further damage, so bear this in mind when choosing the right tools for the job.
A light hammer, perhaps one used for knocking in tacks, is great for non-destructive testing because you can tap your way around the boat and get a good feel for its condition with relative ease. Some surveyors use a brass or a hard plastic hammer to reduce the chance of damage, but not only are these difficult to find, I don’t think they offer much over a normal steel hammer. You only need to tap lightly to get the right kind of feedback: let the hammer bounce on the hull surface or on a bolt head and listen to the «ring» (or otherwise). If you are surveying a steel hull you may need to chip away rust; a hammer with a «chipping head» will do the job.
Some sort of spike or pricker can be useful for exploring the depths of a crack in composite gel coat, perhaps, or for checking wooden structures for soft areas that may indicate rot. Again, you don’t need anything big and heavy: I use a bradawl with a point about 2 cm (0,8 in) long. A small screwdriver would do, provided it has a decent sized handle, but you could also grind down the end of a larger screwdriver, both of which will enable you to poke around in tight areas. Because you’ll be using both the hammer and spike frequently during surveys, fit them with comfortable handles.
A scraper can be useful for removing marine growth on the hull or stern gear, or perhaps for exposing the actual hull surface beneath the antifouling paint on the underwater part of the hull. Again, it doesn’t need to be large; a small paint scraper will do the job, but make sure it’s not a three-pointed «triangular» scraper designed for pull scraping rather than pushing, as this can easily scratch the hull. Supplement the scraper with a small brush with stiff nylon bristles, which is useful for cleaning surfaces you want to inspect more closely.
A ruler or measuring tape helps when sizing up areas of damage or decay, or to pinpoint problems for further expert assessment. Unless you are diligent and write down everything as you find it, you might want to have some sort of narrow masking tape to mark off problem areas. If you can write on the tape, even better – I’ve found the masking tape supplied to decorators for edge painting works well; it sticks to most surfaces and is easily removed without damage. It can also be useful for dividing the hull surface into small sections, meaning you’ll be far less likely to miss a spot.
As we have already discussed, getting as much access as possible to the inside of the hull, especially engine and steering compartments and hidden bilge areas, is an important part of any survey. Be sure to get permission from the owner or broker before you start unscrewing panels – you don’t want to be accused of damage to any part of the boat. Where there is no visible access, other than by a hand or arm, there are two options. The first is a mirror mounted on a stick, and you can purchase these in various forms or rig one up yourself. The second is a camera. While the mirror allows you to see hidden areas and make your assessment on the spot, a modern digital camera is more compact, and can provide vital illumination and a permanent record of any damage you discover. A camera with a moveable angle viewing screen is even better, as it allows you to assess the «hidden» area from different angles.
While a digital camera offers some light, it is not enough to undertake a thorough survey, so a torch is a must. I use one with LED bulbs, which give a good white light, and the brighter the better. Other elements to consider include the ability to adjust the light from wide angle to pinpoint, and a free-standing or head-mount option to free up both hands should you need to tend to a problem. Of course, if there is a mains supply of electricity on board, you can use a wandering lead to give a brighter light.
If you are surveying a stainless steel boat you may need a magnet to test hull quality. Good quality stainless steel should be non-magnetic, although there are still some good grades that are slightly magnetic, meaning it’s not a completely sound test (see below for more information on stainless steel hulls).
Moisture Meters – Pros and Cons
Many surveyors have taken to using moisture meters to help them determine whether any water has been absorbed into the hull laminate. Water absorption can be a major problem for hull and deck laminates, particularly those that feature a core between the inner and outer layers, the so-called «sandwich construction». If water gets into this core the laminate starts to break down, with the core separating from the outer skins and the hull or deck structure becoming weaker and less rigid, which could lead to costly repairs or even the scrapping of the boat as the only cure. This nightmare scenario has plagued the boat industry for years, and is largely down to the poor construction methods and materials of the past. But a moisture meter may help you to detect if there is a problem of this nature.
Note the emphases – using a moisture meter to get a reliable reading can be a bit of a minefield and is something usually best left to the professionals. However, if you are determined to try it, there are several requirements that need to be met before you run the test. First, there are many moisture meters on the market, most of them designed for use on buildings rather than boats. You obviously want to purchase a meter that is specifically designed for boats, and they’re not cheap. Next, the hull should be out of the water and must be given time to dry out (the planking on a wooden hull is unlikely to fully dry out, making a moisture meter reading less meaningful, although on a cold-moulded wooden hull the wood should be impervious to water uptake). Don’t be tempted to take the reading from the outside of the boat – you will get a more reliable reading from the inside, so be sure that it is also dry and free of water stains, which suggest water has been lying in the bilge. Moreover, rain or even a damp atmosphere can distort results, so take the weather conditions into account before attempting a reading. Finally, you need a good dose of experience to perform a reliable test and interpret the results. Get all this right and annual moisture tests (in comparable atmospheric conditions and after the same period of drying time) can be a good indication of any deterioration in the laminate.
However, moisture meters are often more trouble than they’re worth and even the professionals struggle with them. On this basis it’s probably wise to steer clear of them when conducting a personal survey and instead concentrate on the more obvious signs of water ingress into the laminate, such as staining (we will look at this in more detail in chapter below).
Finally, since you will be spending a lot of time on your knees, crawling through the nether regions of a boat, you might want to wear suitable clothing such as a boiler suit and possibly a pair of knee pads to ease stresses and strains.
So now you have your basic tool kit, the survey can begin.
Keeping a record
RECORD YOUR FINDINGS as soon as possible – it’s easy to forget the various defects in just one compartment, and even harder to keep it all straight in your head if you’re surveying several boats in one day. We have already discussed the use of a digital camera, but it is also imperative to keep a list. Some surveyors use an electronic recorder and transcribe their findings after they’ve completed the survey, but I like pen and paper because you tend to remember things better once you’ve written them down, plus there is also the possibility that your notes will include clues that will aid your investigation (for example, you might spot a defect on the outside of the boat that needs checking from the inside; your notes won’t let you forget it!). It’s not always easy to fiddle about with a pen when you have greasy or wet hands, so consider using a personal shorthand to speed things up (as long as you remember what the shorthand means!).
Access
As we have discussed, the more access you have to a boat the better the survey. A ladder or steps will allow you to get up close and personal with the surfaces you’re inspecting. With smaller boats up to 10 metres it may be possible to access the topsides from the ground, but you will still need to examine the deck and carry out your hammer «tap testing», so climb aboard.
Getting under the boat is of equal importance and, since you’ll be spending a large portion of your time beneath the hull, you want to be sure that the boat is securely supported. Sailboats are often cradled on an adjustable metal stand and provided that all of the bolts and fittings are in place, it should be secure because the keel will actually be sitting on part of the framework. Take a critical eye to boats supported by baulks of timber and wedges or even old oil drums, which could come loose as you work.
A sailboat with a fixed keel should sit well off the ground with easy access to those parts of the hull normally below the waterline. Even so, you might have to lie on the ground to see the bottom of the keel or the rudder. With a motorboat it will usually be resting on its keel, perhaps on blocks of wood, and so you’ll need to crawl under the boat to inspect the underwater parts of the hull, not a pleasant experience on a wet day but that is one of the «joys» of surveying!
These are the areas that need close scrutiny so you do need to get right under there if you are going to feel comfortable that you’ve found all possible problems.
The Hull
THE HULL IS obviously the most vital component of a boat. Any failure here can lead to catastrophic consequences, and any necessary repair work can be both expensive and sometimes very difficult to carry out, so it should be your main focus in a survey.
The hull can take a lot of punishment both at sea and in harbour, and the designer and builder have to tread a narrow line between making the structure strong enough to withstand wear and tear while also keeping it as light as possible (the weight of a hull can be critical on planing powerboats or performance sailboats). The designer should always err on the side of safety and augment strength, just to be sure. This is good news for an owner, since hull strength can reduce with age. You’ll need to decide how extensive the deterioration is and how much it has affected hull strength overall, which is somewhat problematic as many of the signs can be well hidden at first sight, meaning a subtle approach is required.
Stresses on the hull structure
TO HELP YOU understand the hull structure and how it is designed, think about the stresses the hull has to withstand. On a planing motorboat the bottom of the hull can suffer very high impact loadings as it pounds through waves, which causes flexing of the bottom panels. There is also considerable stress on the transom or stern areas, which have to accommodate the considerable thrust of the propellers. Displacement motorboats face much less stress and weight is less critical in this Recommendations for Choosing the Type of Boattype of boat, so there shouldn’t be any problems relating to structural strength, although the fastenings on a wooden boat can be a weak point.
While in sailboats some stress originates from wave impact, it is the rigging that imposes the main stresses on the hull. The shrouds pull upwards on both sides of the hull at the attachment points and there are similar strains at the bow and stern where the forestay and backstays try to pull the ends of the boat upwards. At the same time, the mast is pressing down in the centre, meaning the hull has to act something like a rigid girder to take the strain. The keel can add further stress as its weight hangs down to balance some of the force generated by the wind in the sails.
By visualising these stresses, it is somewhat easier to understand the risk attached to any defects you may find in the hull structure. A failure of some sort around the area of the shroud attachments, for example, could be quite serious, while small areas of osmosis (see below) on the hull surface might look bad at first but are quickly resolved with cosmetic attention.
Hull construction materials
IF YOU’RE NOT the owner of the boat, one of the first things you’ll need to determine in any survey is the type of hull you’re dealing with, and it’s not always obvious. There are three main types of hull construction materials:
- composite;
- wood;
- and metal.
Within these main types there are subdivisions. Examples of composite hulls include:
- sandwich construction;
- solid laminate;
- vacuum infusion and hulls with internal liners.
Wooden hulls include:
- traditional plank on frame constructions;
- plywood panels;
- triple diagonal planking;
- cold moulded hulls and clinker planking, all in a wide variety of woods.
There are essentially two metals – steel and aluminium – used to construct metal hulls, and these certainly have different corrosion characteristics. Metal hulls are generally welded but you may come across older riveted hulls where thin aluminium is present. (There are hulls constructed from ferro-cement, but these are virtually impossible to survey since you’d have to cut out a section of the hull to assess its construction quality, and then you’d only be assessing one section. However, if rust from the metal armature is showing on the surface, walk away.)
If you’re struggling to identify the material of the hull, seek out the boat builders or search for boat reviews or brochures on the internet: you’ll need to know what you’re looking at as the surveying techniques are very different for each material, which you’ll discover when you read on.
Common features
Distortion
Before we look at the techniques for surveying different types of hull, let’s look at their common features. The first thing you should consider is the fairness of the hull, so before you even get up close to the boat have a good look at it from a distance. From the end of a sailboat, are the mast, hull and keel, and rudder in line? Do both sides of the boat look even? from the side, do the lines of the chines and deck – and on powered craft, the keel – run in smooth, flowing curves?
Signs of distortion on a wooden boat suggest it hasn’t been supported adequately when out of the water, while distortion in a metal hull is more likely to be a construction problem.
Composite hulls are less prone to distortion, so if anything is out of line it could be the result of damage or poor moulding techniques, more common on older craft but still present in modern craft that have been built down in price rather than up in quality. If the mast is out of line with the hull this could influence the adjustment of the rigging screws on each side.
Keel
One of the more important areas to examine on the outside of sailboats is the keel attachment. Today most keels are made from cast steel and they don’t always sit comfortably with the hull, meaning you may see a line of corrosion or even a small gap where the two meet. This would be a cause for concern because it suggests that water has got between the hull and the keel and the expansion caused by the corrosion could put pressure on the keel bolts. The only way to be sure is to lower the keel and check what is happening in the gap. The corrosion could extend to the keel bolts themselves, but much would depend on the metal they are made from. Modern yachts mainly use stainless steel bolts, which should not corrode provided the right sort of stainless steel is used. Bronze and galvanised steel bolts featured in the past and certainly the latter can corrode, perhaps through electrolytic action, if the galvanising wears off.
If you see such signs of corrosion emanating from the joint between the keel and the hull it could also signal that there is corrosion on the top surface of the steel keel; I’d suggest lowering or removing the keel to get to the root cause. If the keel bolts are accessible from the inside of the hull, tap them with your hammer: you should get a hard ring if they’re in sound condition, although there are no guarantees with this test when you’re assessing a lead keel, which can deaden the sound.
There are many different types of keels on sailboats, including fin, drop and bulb keels, and these all have different methods of attachment.
Since this is an area that is critical to safety you don’t want to take chances here. Go over the attachments and the joints with an eagle eye to ensure there are no signs of movement or corrosion, either inside or out.
Signs of Grounding
The keel is also the first part of the boat to touch bottom in the event of a grounding so look for signs of abrasion or gouging around its bottom. Grounding can put a very heavy stress on the keel/hull joint and its attachment and this could be the reason for that corrosion in the attachment joint.
If you’re surveying a motorboat you also want to be looking for similar signs of past grounding, but in the stern area, which is usually the deepest part of the hull when the boat is afloat. Propellers and rudders can often be the first point of contact on a planing boat, while on a displacement hull it will usually be the keel towards the stern.
Displacement motorboats often have a skeg along the bottom of the hull, which takes the impact of any grounding and protects the hull itself. If a metal shoe is fitted to the skeg look for signs of distortion or strain in the attachment bolts and general abrasion and if you find them, it’s time for a closer look.
The metal shoes are usually made from steel and it’s not unusual to see the attachment bolts that pass through the moulded hull work loose, which could allow water into the laminate. If the metal shoe extends aft to form the bottom support for the rudder, check that this extension hasn’t bent in a grounding, which could strain the rudder bearings.
There will almost certainly be corrosion in a metal shoe made from steel, so check whether the corrosion is just skin deep or more extensive – does it extend to the fastening bolts? A metal shoe is there to take the wear and tear, and it’s quite easy to replace, but you want to be confident it’s doing its job properly.
If and when you discover signs of grounding you may want to check the boat’s history; it could well have been kept on a mooring at the harbour where it took the ground at low water, and any boat that has been at a grounding mooring will have been under additional stress, so look for signs of damage to the hull bottom, the rudders and propellers and of course the keel(s).
Look for cracking or crazing in the gel coat of a composite hull, denting in a metal hull and wear in the planking and timbers of a wooden hull.
Check sailboats with twin keels carefully for these signs. Other hulls that have taken the ground at a mooring may have the giveaway holes in the hull sides amidships where «legs» have been attached to keep the boat upright when it takes the ground.
Checking composite hulls
FOR MANY OWNERS a composite hull is a mystery and potential owners go in fear of the dreaded osmosis (see below). The first thing to do when surveying a composite hull is to establish what the laminate consists of, so ask the broker, builder or take to the internet. It could be a solid laminate that has been built up with a hand lay-up system, during which each glass mat layer is placed manually into the hull and impregnated with the resin.
Some modern types of lay-up use a similar system, but the resin is introduced under vacuum once the dry mat has been laid in the mould. A third system introduces a foam or balsa core into the laminate to create what is known as sandwich construction, and this might cover the whole of the hull structure or just parts, the rest being solid laminate.
The hull may be stiffened with additional internal frames and stringers, which are added into the mould, or in a more modern system an internal lining is added, which is a separate moulding that fits inside the hull moulding and serves both to stiffen the hull moulding as well as introduce some of the internal divisions and structures of the yacht interior.
If you can get this «deep level» construction information, you’ll have a much better chance of knowing what to look for.
Osmosis
Osmosis is mainly caused by water permeating the gel coat and creating bubbles between the laminate and the coating when it expands. It will usually present in a series of hard «bubbles» on the surface of the gel coat. Small bubbles in localised areas don’t pose a particularly serious problem, but they do need to be ground out and filled with resin and then smoothed down to restore the finish.
You’ll probably require a paint job to fully restore the topsides. Osmosis can also occur in the underwater surfaces that are constantly submerged; you should be able to detect gel coat bubbles by touch, unless there are several layers of antifouling paint that have built up, in which case you may want to scratch some off to investigate. More extensive areas of osmosis bubbles may require areas to be ground off and extensive re-coating with proprietary systems. For yachts that are perhaps less than five years old the risk from osmosis should be small because of advances in the materials and methods of construction, but it’s still worth checking.
Osmosis bubbles may be small, so you’ll need more than just a quick glance at the surface; go over the whole hull surface in detail, both looking and touching. Mark sections on the hull with your tape to be sure you don’t miss a spot.
Chips, Cracks and Scratches
While you’re looking for bubbles, also check for scratches, chips and cracks in the gel coat. Scratches are often shallow and feathered and you may be able to feel their roughness rather than see it. They tend to be more of a cosmetic problem and can often be polished out. Of course, deeper scratches and/or chips that penetrate the laminate need more attention. Both deep scratches and chips should be ground out and filled with new gel coating, then smoothed down to prevent water entering the laminate.
Because cracks will normally extend down to the laminate under the gel coat they tend to fill with dirt, which can make them more visible. Cracks need to be taken more seriously because apart from possibly letting water into the laminate, they’re usually a sign that the hull has been under some sort of stress. Those that radiate from a single point may indicate impact damage while longer cracks could indicate undue flexing of the hull, perhaps caused by coming alongside too hard.
Cracking of the gel coat can occur around fittings that have been under stress. If you find this kind of damage, you need to turn your attention to the inside of the hull because the impact or flexing that caused the cracks in the gel coat may have been serious enough to stress the internal stiffening of the hull, to the point that it can detach from the main hull moulding.
Because this internal stiffening is normally added after completion of the main hull moulding, the bonding between hull and stiffening may be weak and any impact to or flexing of the hull moulding could cause the bond to break. You can see this defect fairly easily: if the edge of the stiffener is lifting away slightly from the hull moulding, the problem is serious. The stiffener won’t be doing its job properly and may let water into the gap, which the foam former will absorb in turn, leading to further deterioration. Do as much as you can to examine the attachment of the internal hull stiffeners, although access to these internal areas is rarely possible without dismantling half of the interior.
Often the stiffening takes the form of rigid plywood bulkheads that are bonded into the hull and these may create hard points where the slight flexing of the hull moulding comes into contact with the rigid bulkhead, which could lead to delamination. Do take the trouble to examine the attachment of the engine bearers in the engine compartment, which can be a high stress area – the base of the bearers at least should be accessible in most cases.
It is easy to examine the topsides of the hull for scratches, chips and cracks, since the gel coat is exposed, but below the waterline the hull will have been painted with antifouling so that cracks and other defects are not likely to show up so well. This is a dilemma for any surveyor, so it can pay to scrape off the antifouling in selected areas to check what is going on underneath, provided you have permission to do so. You would be justified in doing this if you had found problems in the topside examination that might extend below. Otherwise, selected areas might be at the turn of the bilge on a sailboat or at the chine on the motorboat. On planing motorboats you’ll want to check along the sharp edges of the chines and spray rails because it can be difficult to lay up the laminate into these depressions so there may be voids that could show up later as chip-like marks in the gel coat. Composite structures in general do not take kindly to sharp edges and corners so that these can be the first areas to show signs of trouble. When there is no fendering, transom corners are especially vulnerable to chips and scratches.
In areas where you can’t remove the antifouling paint below the waterline at least try to feel the surface. Look along the surface for any slight distortion that may indicate a past repair.
On planing motorboat hulls the laminate comes under considerable pressure when the boat is running at speed in waves. Obviously the hull laminate and structure should have been designed to cope with this and it is normal to see the hull skin supported by longitudinal stringers which reduce the hard spots and reduce the chance of corrugations developing.
However, there can be considerable flexing of the hull panels so look for cracking of the gel coat around those panels that join to stiffer areas, such as around the keel and the chines. Check also for signs of delamination in the frames and stringers, particularly around bulkhead edges. It’s not unknown for a plywood bulkhead to crack horizontally if it can’t accommodate the flexing. This especially would suggest that this planing boat has had a hard life and you’ll want to take a closer look, and certainly if it has sandwich construction.
Sandwich Construction
Sandwich construction hulls can pose particular problems for surveyors. There was a time when sandwich construction was in vogue, because it created a stiffer laminate that required less internal framing and added sound and heat insulation. However, having the inner and outer layers of laminate separated by a foam or end grain balsa layer a centimetre or two in thickness has been the cause of many failures.
The major problem with sandwich construction is that the bonding between the three layers can become detached due to flexing of the structure in a seaway, allowing water in. Sandwich construction relies on good bonding between the layers for its structural strength so if the bonding fails there is only the relatively thin outer layer keeping the water out and failure can occur. If the bonding fails, the three layers may be moving independently of one another which breaks up the middle softer layer of semi-rigid foam and tends to invite water into the gap. Water may enter through cracks in the laminate or poorly sealed fastenings in the hull, such as seacock inlets, chain plates or other hull fittings, and even if there is no water entry the overall strength of the laminate will be weakened.
You may find sandwich construction through the entire hull but it’s more likely to be found in the topsides only, particularly on a planing motorboat where the pounding of the hull in waves at speed can be detrimental to sandwich construction if it starts to flex. Therefore, if you suspect sandwich construction in the hull you’re surveying, try to establish which sections have solid and which have sandwich construction. You may have access to the hull specification but if you don’t, use your hammer to «tap it out». The sandwich sections «absorb» the sound, and you should be especially suspicious of a «dull» sound, since it could indicate delamination or the presence of water in the sandwich. Check fixtures and fittings in the area, but remember that these are usually made from solid laminate or plywood inserts in the sandwich.
In fact, your suspicions should be raised if you come across any sign of cracking or impact on the gel coat of a sandwich hull, as this could be a route for water to enter the laminate. If a boat (of either solid or sandwich construction) has been outside in the winter months and water has entered the laminate, there is a possibility that the trapped water will have frozen and expanded so that a gradual process of delamination occurs. If you suspect that a sandwich hull is not sound, it’s probably wise to walk away from the purchase. If it is your own boat, you could use a moisture meter (see higher) to assess the moisture levels in the hull, although these are tricky to operate. In this instance, I’d probably recommend calling in a surveyor for a professional diagnosis.
Dealing with Painted Surfaces
While owners tend to take great care of the outside of the hull the inside is much more likely to be left to its own devices. Look for lifting edges where the hull framing and stringers have been faired in and examine areas that have a fresh coat of paint, as this may have been applied to cover up a repair or damage. Poke around with your spike to ensure that everything is firmly attached, particularly around the engine beds and bulkheads where the stresses can be higher. There should be adequate access to all the skin fittings on the inside, so check carefully around the edges of these and the securing bolts for any signs of weeping, perhaps indicating a poor seal or water in the laminate.
On some older composite boats you may find that the hull, and at least the topsides, have been painted, which should ring alarm bells. It could be that the topsides needed a «freshen up» but equally the paint could be covering restoration work, undertaken to cure osmosis or other topside damage. If the paint job was for cosmetic reasons, it’s likely that the owner or broker will admit to this, otherwise you should delve a little deeper.
A professional paint job may be hard to detect because it will look like the original gel coat, but you may be able to scrape away some of the antifouling to check the hull condition underneath.
If you can see brush marks, indicating a poor paint job, you’ll have a major job on your hands to restore the hull to a good finish, in which case I’d recommend you walk away.
Checking wooden hulls
WHEN SURVEYING a wooden hull you are looking for a range of ailments affecting the wood and the structure of the boat. What that is will be determined to a certain extent by the construction method used for the hull, the wood type and the finish on the timber. The most common construction system is planking laid up on the frames and timbers that give the hull its shape, and this is usually quite easy to identify because the seams between the planks will almost certainly show somewhere, unless the boat has had a very recent paint job. Wood is always on the move, expanding when wet and tending to contract as it dries out. This puts pressure on the caulking- or spline-sealed seams.
Drying Out: Caulking and Splines
Traditionally caulking was oakum hammered into the seam to seal it and then covered with tar or a proprietary caulking material. Wooden splines – finely tapered cross-section strips of wood hammered in to seal the gap – were less common. Both traditional systems are still used on many wooden fishing and work boats, but yacht builders tend to use either modern caulking compounds or splines, both of which allow a better finish to be retained on the topsides. Therefore, you’re looking for any sign that the caulking is coming loose or is damaged. You want to look carefully around the stem and the stern where the planking ends are sealed to the timbers because this is where you’re most likely to detect any movement or shrinking that could dislodge the caulking.
The planking at the bow is under stress because it was bent in a curve to generate the right shape, and it is the fastenings at the stem or stern that hold the planking in place. If you do find that caulking has dislodged it may be possible to hammer it back into position, but the timbers may have been allowed to dry out, thus widening the gap. If drying out has been the cause you may see some longitudinal splits in the timbers at the bow and stern because these timbers will often slip when drying out. Unless it looks serious this should not be a major problem because the wood will swell back to its original shape when it gets wet again, but serious drying out can distort the timbers and planking beyond any hope of restoration.
If planking has warped (curved across the grain), it can signal drying out or poor quality wood. Warping places a strain on both the fastening and seams, so look for signs of corrosion – a green coloured stain if the fastenings are copper or rust stains if they are steel.
The galvanised fastenings often used on fishing boats can have a characteristic whitish stain, a result of the reaction between the zinc and the acidity of the wood. You’ll find this mainly around bolts used to connect hull timbers and framing, since acidic oak is often used here. Small amounts close to the fastening may not be serious but if it has become more extensive it can soften the wood so that the whole structure becomes weakened. as a minimum step the fastening should be withdrawn for examination and this should reveal not only any corrosion but also the extent of the soft timber. Poke around with your spike or bradawl to reveal the state of the timber without dismantling.
You don’t want to be sticking the sharp point of your pricker into the pristine finish of the topsides, but if you see any signs of rot or damage you may want to explore further.
A slight wrinkling or split in the paint finish usually signals some sort of disturbance underneath, so give it a gentle tap with your hammer; a sound wooden hull should have a nice clear «ring» when tapped, so start exploring further if you don’t get this response.
Wet Rot, Dry Rot and Wood Pests
Inside the hull you should have much more freedom to explore with your spike, which is good because this is where you’re likely to find trouble on a wooden hull. Before you start pricking the timbers, sniff the air: both wet and dry rot have their characteristic smells, dry rot tending to smell «dry» because it is a form of fungus while wet rot has a damper smell to it. Dry rot is also usually visible in the white cobweb-like fungus that spreads across and into the wood and by cracking across the grain, and it is extremely difficult to cure short of stripping out the infected wood. I recommend you walk away from any wooden yacht infected with dry rot. If you already own the boat, you need to deal with dry rot head on, so contact a professional surveyor.
Wet rot, as its name suggests, is caused when timbers are constantly wet and don’t receive adequate ventilation, the sort of conditions that often exist inside a boat. If it lies under a painted surface you’ll see it in the cracking and splitting of the painted surface. Unfinished wood tends to show cracks across the grain and the wood has a sponge-like texture. For wet rot to form it usually needs a combination of damp and stale air so if you can change the atmosphere in the area, you can possibly dry out the contaminated area and treat it with wood preservative if it affects only a small region. Larger areas and rot in frames and timbers may require replacement or doubling timbers, so seek expert advice.
Once cured, wet rot should not return if adequate ventilation of the area is put in place. However, I would hesitate to go ahead with the Ownership and Financial Side of Yacht Purchasingpurchase of a boat where wet rot has been detected unless you can be sure of its extent and are prepared to carry out the required restoration work.
Now we come to the bugs that like to chew wood. Woodworm – the same type found in a house – is the most common, although it is less likely to infect boats because it prefers dry wood and the harder woods used in boat building are less prone to infection. However, it can infect the internal fittings and fixtures. Woodworm is detected by tiny holes and a timber coloured dust on the surface, which is the residue left by the worms as they bore their way into the wood. Once established, you can cure woodworm with proprietary solutions but you need to be certain you have detected all the woodworm-infected areas on board.
More serious among timber boring pests is the gribble, a larger creature that bores a hole perhaps 2 or 3 mm in diameter. A gribble worm bores along the grain and doesn’t usually come to the surface until it has damaged much of the interior of the wood, so it can seriously weaken a timber without there being much external evidence besides the entry holes. If water gets into the bore holes it can start wet rot, which may be the first signs of a gribble worm problem, but also check areas where you can see the end grain of the wood, such as inside a hole cut for a seacock; modern antifouling paints have had an impact on gribble but any areas such as this where the paint does not reach can provide the entry point. A soft hammer tap sound could indicate trouble that would demand a closer inspection by an expert.
Signs of rot and worm in a timber hull may not always be apparent from the outside so you need to get as much access to the interior as possible. Interior access on wooden hulls is usually easier than with composite hulls as they tend to be one-off buildings without complex interior linings. The obvious place to start your interior inspection is in the bilges where water may lie or may have been lying. Unless it is a very smart construction you shouldn’t have a problem poking around with your pricker in these interior timbers. Look carefully at points where the frames and timbers meet the planking, places where water might have been trapped and the rotting process has started. If the wood has been left bare, you might be able to identify the problem areas by discolouration of the wood, and certainly any discolouration should be examined closely. It might just be an oil stain or possibly an area where water has been lying in the past, but it’s better to be safe than sorry. While you are doing this internal examination also check any visible fastenings in the same way. It can be a good idea to draw some of the fastenings if you do see or hear signs of trouble, otherwise they are best left alone.
Other Types of Wooden Construction
Plywood has been widely used in boat building both for hull construction and internal partitions and panelling. Good quality marine plywood is a very durable material that isn’t likely to be prone to rot or worm unless there are exposed edges. These exposed edges can absorb water and if that water should freeze, it can start to force the layers of wood in the plywood apart, which could start the rotting process. In general, take the same approach for checking a plywood hull as you would a timber and frame hull.
Read also: Maintaining and Modifying Your Sailboat
If the hull is constructed from plywood panels, you need to check it for any signs of rippling in the surface and along the edges, which can indicate delamination. The likely construction method would see the plywood panels attached to the hull with both glue and screws or bolts. If screws have been used, any movement in the hull might pull these screws, so any screw heads standing proud should be a cause for concern.
Cold moulded hull construction should be very durable because in many ways it is similar to a laminate hull. In cold moulded construction the glass of the laminate is replaced by thin strips of wood that are laid up in the desired shape and secured with stainless steel staples and epoxy glues. Once the epoxy has cured, the wood should be fully sealed against water ingress. Look for signs of discolouration, which would indicate that water has got into the wood. There may also be areas of wet rot in some of the internal timbers where water has been lying in contact with the wood.
Checking metal hulls
Steel Hulls
Let’s look at steel hulls first because they tend to be more common than aluminium. When corrosion is present in steel there is a very obvious giveaway sign and that is rust. If there is rust on the steel, it will fight its way through any paint finish to the surface quite quickly, certainly before the corrosion gets to the point where it can be serious. During a survey, therefore, you’re on the look out for the very distinctive signs of rust, which are very obvious on a light coloured hull. The most obvious places to look are on the welded seams of the hull, which tend to provide a good source of rust potential because the welding has been laid down under intense heat.
Access to the interior is important: you’re much more likely to find rust here, along the welding that links the frames with the hull plating, and a damp atmosphere can create the breeding ground for rust to form.
Having found signs of rust the next step is to determine how serious it is. Light rust on the surface of the steel isn’t usually a problem, provided that the rust is removed and the area properly painted. What you are looking for here are the signs of deeper pockets of rust, that which is serious enough to have eroded the surface of the steel and reduced the thickness of plating or frames. Strangely enough the evidence of this deeper form of corrosion is likely to be shown by a rise in the steel surface. This is because when steel is converted into rust, which is a form of iron oxide, it absorbs oxygen and this increases the volume of the rust compared with that of the original steel.
In terms of its thickness then, a patch of rust may look very threatening if you assumed that the amount of rust was equal to the amount of steel that had been eroded away, but in fact the volume of rust will be something in the order of ten times the amount of fixed steel. This doesn’t mean you should ignore it, because rust is always going to get worse; the slightly porous nature of rust means that it can hold water even when the surrounding area is dry.
You’ll also want to find out what has caused the rust in the first place. Perhaps it was water dripping from above, a poor paint job that hasn’t effectively sealed the surface or an impurity in the original steel that has set up a little galvanic cell. Modern steel hulls have usually been sandblasted after construction and painted with epoxy paints, which provide excellent corrosion protection but even with such a hull you want to check the surface for scratches or scrapes that may have damaged the coating. These will need treating before the rust gets in and starts its nasty work. I have come across small areas of steel where corrosion has started for no apparent reason and it has eroded away perhaps half the thickness of the steel in a very local area. This could come from an impurity in the steel or it might be down to something as minor as a coin being dropped into the bilge, the two dissimilar metals reacting in the presence of water.
Whenever you find corrosion both inside and outside the hull you must chip away the rust to find out the extent of the corrosion. Get permission from the owner or broker before you do this because not everybody likes having their lovely steel hull chipped away, but you do need to find out how much of the steel has been eroded away.
On a yacht the steel plating might be quite thin, perhaps just 4-6 mm, so any reduction in this thickness through corrosion could impact upon the integrity of the hull. It can be quite easy to repair corroded areas by cutting out the affected portions and welding in a new piece, but it does mean getting access both inside and out.
As with a composite hull you need to go over every inch of the hull as far as possible because corrosion can be very localised. If you find the corrosion is extensive, it’s probably a good idea to walk away from the boat. However, fishing and workboats with heavy scantlings can still function with quite extensive corrosion, as long as it is not deep pitting. Sharp edges and corners will be most prone to this type of damage. When you find rust spots and have chipped out the rust down to the hard steel below hold a straight edge across the area to see how deep the pitting is; anything over a quarter of the thickness of the plate should be cause for concern.
Of course, you’ll also want to check a steel hull for any damage or distortion that may have been caused by collision. Allowing for the distortion that welding can create, a modern steel yacht hull should still come out relatively fair and smooth.
Aluminium Hulls
Aluminium boats are actually quite rare these days and along with it being a difficult material to survey adequately, the chances of getting involved with aluminium are slim. However, there may be aluminium fittings on other boats so it pays to have some knowledge of its qualities.
Unlike steel hulls, you won’t find rust on an aluminium hull. However, you’re more likely to find corrosion of a different type: electrolysis. This is caused when two dissimilar metals are connected, setting up what is in effect a battery between them, which leads to corrosion. Being the «lighter» metal, aluminium is usually the one that suffers. Builders of aluminium boats should take care to prevent contact between different metals by insulating them, but over time the insulation may have broken down. You can also get corrosion resulting from action between a bronze propeller or bronze skin fittings, but anodes, which are made of an even lighter metal than aluminium, should take care of that. Sailboats with an aluminium hull and an iron keel are also cause for concern, but again they should be insulated or at least anode protected.
Therefore, if you’re surveying an aluminium boat you’ll need to examine the hull both inside and out for the tell-tale white corrosion powder which shows that all is not well. Broken wires, later additions of metal fittings, even the wrong type of antifouling paint can cause problems on an aluminium hull, so if you find corrosion, you’ll need to call in a specialist to determine the cause.
Some boats combine a steel or composite hull with an aluminium superstructure. Composite and aluminium are quite compatible, but steel and aluminium have to be carefully insulated from each other to survive. Check the insulation carefully where possible.
Stainless Steel
Stainless steel is a steel alloy with a minimum of 10,5 percent chromium content by mass. The stainless normally used in the marine environment is 316, which works pretty well as far as combining strength, corrosion resistance and shaping abilities. However, 316 stainless is also more expensive, so you can find cheaper alternatives, and there are a large number of these, and there is no easy way to assess which type has been used.
Even high quality stainless steel can be subject to rust streaks if a tiny bit of the steel is exposed, and you are much more likely to get these when the stainless has a matte or a machined surface, i. e. on the threads of a rigging screw. You are far less likely to see rust streaks on highly polished stainless, such as handrails and some other fittings. Besides, you don’t need to be too concerned about rust streaks on stainless steel as it’s unlikely to be anything more than skin deep, so it should just be a matter of polishing it off.
All hull inspections take time and patience and you need to have all your senses on high alert, because the clues to any potential issues can often be quite small and easily bypassed, especially since it is not unknown for sellers to temporarily cover them up. Buying a yacht can be an emotional business and it’s easy to convince yourself that any problems are not serious, but hull problems are generally the hardest or most expensive to cure. Keep reminding yourself that the hull is the only thing between you and the water; you don’t want to take any chances with your life.