This technical brief attempts to set out the basic construction techniques as well as the material, equipment, infrastructure, skills and labour requirements necessary to build fibreglass fishing crafts suitable for use in Sri Lanka’s coastal fisheries industry. As a material for boat building, fibreglass has gained in popularity over wood and metal in both developed and developing countries, mainly because of the relative simplicity of construction, the ability to produce many identical hulls from a single mould, and the ease of maintenance of the boats themselves. Disadvantages of fibreglass stem from the health risks associated with inhalation of fibre dust during construction, and the fact that the boats are slow to degrade and disposal at the end of their life is difficult. Fibreglass is a term used to describe Fibre Reinforced Plastic (FRP), a material consisting of glass fibre impregnated with resin. The key to producing high quality boats is a good mould - a mirror image of the finished hull, which is also a fibreglass construction cast from either a plug, which is wooden replica of a hull, or the hull of an existing boat.
The continuous filament is held together with a binder to form a continuous sheet of chopped strand mat of variable thickness. The laminating resin (a translucent liquid of pale colour) provides the medium within which the fibreglass mat is bedded. This material is used as filler, or for bedding deck fittings or filling internal corners on joints which require bonding.
If accelerator is purchased separately, a purple liquid (Cobalt Naphthanate) is usually used with Methyl Ethyl Ketone Peroxide (MEKP) catalyst. The drum in use will be laid horizontally off the ground on a steel cradle (see figure) with a removable brass tap screwed into the drum lid.
Accelerator can be added during the preparation stage and mix well with a clean, disposable wooden stick. In the case of gel coat, a colour pigment will have been added to uncoloured gel coat according to supplier's mixing ratios.
The task of storing and cutting the mat may be allocated to one labourer who then becomes skilled at this task.
For cutting curves, a felt tip pen or chalked line can be drawn for guidance and the cut made freehand whilst allowing a 10 cm margin.
To begin, place the plug (or existing hull being used to create to mould) upside down on a level floor, and make sure the plug is absolutely level using a spirit level or transparent flexible tube filled with water. This especially formulated gel coat is the beginning of the coating, which will eventually give the polished surface from which the mould will be lifted. Finally, polish with rubbing paste and then with 5–7 coats of non-silicone wax to give a brilliant sheen, before applying a coat of PVA release agent, which is the last step before the mould itself is begun.
If the shape of the hull is such that the mould has acute release angles, a split mould, rather than a one-piece mould, is necessary. To build the mould, first, a uniform layer of gel coat should be applied to the plug, using paint brushes with unpainted wooden handles or a high-pressure spray gun. For best results, panels of surfacing mat should then be laid down to create a smooth skin. After the fibreglass laminate has been completed, and has cured beyond the gel stage, bond the stiffening to the outside before release from the plug.
To release the mould from the plug, gently hammer small wooden wedges between the mould and plug. Plugs and moulds for deck and interior can be made using sheets of hardboard, or plywood covered with Formica, as a plug, to provide large flat areas of decks and bulkheads with a uniform surface.
After the mould has been cleaned, waxed and polished, the first step in laying up a new hull is the application of gel coat with paint rollers or paint brushes, or by spraying. Any areas that have become too dry because of overcure can be lightly washed with styrene to regain some stickiness. The mat now needs to be laid in either a fore and aft (forward and back) direction or transversely (across). A keel is formed by laminating additional material along the centreline of the hull extending forward to the stemhead and aft to the transom boundary, to form a structural backbone. Topsides are increased in thickness to form a strong sheer in powered vessels and further increased in areas that will take mast rigging or equipment loads. The stiffener former is placed in position on the gelled laminate and the reinforcement is built up layer by layer as a continuous process.
Hollow cores are plastic, cardboard or a single layer of Fibreglass from a hat shape mould, which can be cut to allow a fit to hull curves. The strength and stiffness of the section can be varied by adjusting the section depth and retaining a constant lay-up or by increasing the lay-up where the stiffener depth cannot be increased. In addition to separating compartments, bulkheads are essential in providing the rigidity necessary for maintaining the shape of the flexible fibreglass hull. Material incompatibility is one problem that may lead to de-lamination and the seepage of water.
Wood should be roughened, dry, dust free, unpainted and given as big a contact area as possible. Brass or bronze fittings should be coated with epoxy resin before being overlaid with any structural resin.
Glass, polythene, formica, aluminium and the like will not bond and can be used to mould flat panels of Fibreglass. The easiest stage to trim is just after the resin has set, when the moulding is rubbery and can be cut with a sharp knife. All Fibreglass working will leave a rough, shattered edge where water can penetrate and eventually cause de-lamination.
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Apart from their expertise when it comes to repairs, Rob and Tony also provide expert boat custom refits and modification services. With over 60 years of combined experience, Tony and Rob are experts in the art of custom boat refits and modifications and can also build bait tanks, fibreglass hard tops and gun racks. They also custom make fibreglass wave breakers for Haines Hunter 17R and 17L, high and low. Location: Australia Some photos of the hull cleaned up and ready for the stringers.
Also the photo of the slit where the previous person almost cuts through actually held water in the boat for over 24hrs and only wept but ill still glass over it and put a little matting on it. I have made custom sub boxes for a friends car a bit ago and helped a friend make a fiber box so have a fairly good understanding about glassing and how it goes.
Im not doing any glassing till probably end of next week and we have 2 days nextweek of 30+c so it should dryout nicely. When i put a long straight edge under the boat and the top is seems to look sort of ok, but the traider skids seem to be about 40mm away from touching it? I will clean up around the hole as you mentioned about 100mm and glass a new strip over it. I will take some pick of it when i get home with the straight edge on it so you can give your opinion too.
Quick look and see loads of strands of glass that never been rolled down when the boat was sprayed with a chopper gun . In your case for sticking things in and coving the corners TALC and AEROSILL mix is completely ok .
The consistancy is best when you can turn the container on its side and it just starts to move but dosent slump or try to runout of the container !! After you make the bog let it sit for a couple of hours before you use it just the make sure both ingreadiance are 100% saturated with resin you will notice its stiffer than when you first mixed it When you put a blob on the surface and then remove it and the surface should have a damp or wet looking patch where the resin is on the surface . After you have cut and fitted the stringers and its ready to be stuck in make sure you have lots bracing to hold them secure in place lift the stringer out and brush a coat of catalysed resin all over the wood and let it soak in!! When its hardened a second coat specially the ends and the edges that were cut and shaped . Ok i think i got what you was saying and when get home will digest it and repeat back for your confirmation. I will try a chisel out the old filler over the weekend and also need to go over all the hull with the grinder to prep it for the new glass to bond. Im hoping to have this done for xmas, i have all the wood and glass now so just the case of getting it all put together. I do have a 200 yammy to go on the back too, the boat was recommended for a 180hp but the old transom was 15mm and imm replacing with a 18mm so 200 should be fine.
Cut the timber for the stringers and by then i will have a revised layup for you stringer system . Location: East of Atlanta Ga Tunnels, I have a question (still on my learning curve here) the bog recipe you mentioned, I understand the 2 to1 mix of talc and aerosill, then mix the resin in and let it sit in a covered container, hardener is mixed in just as you are about to use it correct ?

Originally Posted by wooky30014 Tunnels, I have a question (still on my learning curve here) the bog recipe you mentioned, I understand the 2 to1 mix of talc and aerosill, then mix the resin in and let it sit in a covered container, hardener is mixed in just as you are about to use it correct ?
Use a smaller conainer big baked bean tin or simular to measure the talc and aerosill into the resin as you are slowly stirring with the paint stirrer !! Its easyer to use some of the premix you just made in another plastic container then add the catalyst and t thoroughly mix ,you will notice it changes color slightly so all needs to be the same colour. I was thinking about the tank of making a cut out in the keel stringer to leave about 70mm thick and about 1.2m long so i can make a box shape in the floor for the tank to fit in, that way the floor is supporting the tank and not the stringers and i can also access it if any problems.
The hull wall is 6mm thick and i will put a 18mm ply + 15mm ply, im guessing that will be more than enough for the motor.
I still need a little info for the joining of stringers as i read that scarf joints at crap and a think of the past and now a sister joint is better? Under the stringers where they were and the new ones will be placed they sat inside the strakes !!
Strakes are a weak part of any hull bottom and a place that has 3 corners on each strake ,, they bend and work and always get cracks and the glass layers separate and the first place you go looking if the boat has a leak !! I have drawn the extra layers of glass using double bias glass as 100% of the strands will work for you right to the line where it finishs , 200mm each side of the stringers both sides full length , No woven roving should not be used !! Like i said before this post ,coat all the wood with resin and when it hard second coat again specially any end grain .
Dont make the resin go hard to quickly as its needs to soak in and thats what the glass will stick to !! The glass panels between the strakes and the keel are the ones that take all the pounding and stress when the boat is going . I hope you took note of the transom thickness i recomeneded and it should have knees down onto the stringers !! The bigger boats we have we always glass in extra glass then fill with high density foam and glass over and then carry on with the rest of the hull .
Location: East of Atlanta Ga Tunnels, the bog recipe makes perfect sense now, I knew about the adding a little talc and aerosil at a time and yes absolutely a plastic container.
On my boat it looks like I'll have to put a second set of stringers on the outer strakes and a keel board (didn't have them there before nor a keel board).
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Location: Port Moody, Canada Restoring 32 and 36 foot ChrisCraft plywood plank boats I am beginning to restore two ChrisCraft plywood plank Hull boats, 36 foot and 32 foot.
Location: ohio boatnut plz tell me how you get on, I am looking a t a 57 ft CC connie right now that looks to have a few back planks, if you could post the cost of the wood and time it tokk to replace them I would be grateful. Originally Posted by boatnut007 I am beginning to restore two ChrisCraft plywood plank Hull boats, 36 foot and 32 foot. Location: Kingston, Ontario, Canada I myself am having some planking problems with my 32' Chris Sedan, found in field with minor dry rot, previous owner cut hole in side for a tube slide for his kids AHHH! Typically, a hardwearing surface is created with the use of a gel coat, strengthened by layers of fibreglass mat impregnated with resin. The thickness of the cloth or mat varies with the weight of the glass in grams per square metre.
WR has a high tensile strength and also gives a higher glass per unit volume ratio than CSM, which means less resin is needed, and therefore is cheaper to use. It is used to support a thick gel coat or to produce a smooth finish on the innermost layer of a laminate.
The usual shelf life for resin is given as 6–12 months, but it can be used as long as it is liquid.
When cured, the gel coat forms the shiny, smooth, weather resistant outer surface of the hull. Since it is composed mostly of a filler powder, which is water absorbent, it should not be used on underwater surfaces unless based on an epoxy resin. The amount of accelerator added will be determined based on the weather conditions (humidity). Standard white pre-pigmented resin is widely available as it is the most popular hull and superstructure colour.
For preparation, a cutting table is needed (see picture) with a vertical rack for the rolls of different types of reinforcement from which appropriate lengths can be drawn and cut and then re-rolled and labelled with a felt tip pen to indicate to the laminators what it is for. Lengths up to 10 m can be prepared on a shorter cutting table by folding the reinforcement. At the deck edge, which is in this case near the floor, attach a plywood flange so that later during the moulding process, gelled Fibreglass can be trimmed back to leave a solid laminate with a clean cut edge. Repeat this process of hand finishing until the plug is smooth enough to receive a layer of hard tooling gel coat. Five workers would take at least a week for the final preparation of a plug for a 10 m hull. Ideally the thickness of the mould should be at least twice that of the hulls to be made using the mould. This backbone can be maintained at the midwidth throughout the length or be reduced in weight towards the ends. The boundary of the transom should be increased to support and stiffen the sides, bottom and transom laminates. Frames are usually a solid or hollow core former covered with several layers of fibreglass mat forming a closed box or semicircular section when combined with the hull laminate.
The last layer of hull laminate can be timed to cover the framing to give a more finished appearance. A collision bulkhead should be installed forward and machinery space bulkheads should be watertight. Polyester resins are not good adhesives so the resin must have a physical grip on the adjacent material.
Resin thinned with 10% styrene or 5% acetone will allow a keying coat to better penetrate a wood surface.
Cardboard, hardboard, cement, and canvas all have rough porous surfaces and will give some degree of bonding.
Fibreglass can be drilled, filed, sawn and polished but not hammered or bent and not easily punched or sheared. Wherever possible drill from the smooth face towards the rough side as this prevents chipping the resin-rich gel coat.
Special care should be taken with catalyst, as it will cause burns to skin and possibly blindness if in contact with the eye. If your vessel needs some attention, speak to the experts at A1 Custom Fibreglass in Newcastle.
With years of experience in the industry, they can modify your vessel requirements and your budget perfectly. What would be the leniency for the hook or rocker and what problems does this cause later if its too bad? Dont mix the resin so it goes hard quickly beause you are defeating the object if wanting it to soak in to the wood !!. The resin coats are to seal and help preserve the wood so it will last for long time AND give a good bonding surface for the glass and bog to stick to as you can see from the old bog thats still there its was a sad atempt at sticking the wood down . I am new at this and welcome any professional advice regarding finishing the hull above and below water line, repairing wood beams that are rotten, how to finish new marine grade plywood decks, where to find materials and equipment etc. For most of your maintaince needs, any good marine dealer with a large inventory will have most of what you need in stock. The required strength is achieved either by using several layers of mat or by using a thicker gauge of mat. Once the mould is created, it can be used to build hundreds of boats, which will have precisely the same shape as the original boat or plug used to create the mould. Laminates for larger hull are best made of alternate layers of CSM and WR with extra CSM near the outside. The resin is usually supplied in 200-litre drums, but can also be bought in smaller quantities from retail suppliers. Pre-accelerated resin is recommended because the supplier is able to make a more thorough mix; and it is one less step for the user.
Accelerator and catalyst must never be mixed directly together as this could cause an explosion. Between the tap and the tray will be enough room to place a 5–10 L plastic bucket, which can be filled with resin for use by a laminator. Catalyst is only added at the very last moment before laminating begins, when everything else is ready.

To create the flange, a pattern of it has to be made on the plug on each side of the joint line. In tropical countries this mixture will set hard in 20-40 minutes, so only the amount required for the immediate job at hand should be prepared. If a brush is being used to impregnate the fibreglass mat, short jabbing motions of the brush should be used. The reinforcement stiffening can be of wood, foam or rolled newspaper, which are placed against the outer surface of the mould and covered with a layer of fibreglass to form a box section. Once the plug has been removed, inspect the mould for flaws and damage and make any repairs necessary before sanding with water sandpaper of increasingly finer grades, and polishing with 5–7 coats of wax to finish.
Have a follow-up bucket of resin ready for use as soon as the first is emptied, to achieve a good bond between the two separately mixed batches.
A sequence should be worked out so that the binder is dissolving in CSM laid in one part of the mould, while previously laid CSM with now dissolved binder is being consolidated in another part. Around the joint line a scarphed laminate should be made with succeeding layers 25 mm shorter than the preceding layer. A typical boundary lay-up is formed by overlapping the side and bottom with the transom reinforcements, but as with the backbone the increase can also be achieved by the addition of strips of material laid around the boundary.
Wood or exterior-grade plywood is usually used for bulkheads and should be fitted while the hull is still in the mould. Any wood that has been treated with preservative should not be used, but if unavoidable then a joint using screws or bolts should be substituted.
All metals should be de-greased before use, even finger marks or sweat from a hand can make the bond ineffective. The basic shape cannot be altered and the resin component shows a tendency to fracture and chip. Masking tape or a punched mark will help prevent scratch marks from skidding drills if a hole has to be drilled from the gel coat side. Heavy-duty electric jigsaws with metal cutting blades or diamond wheel compressed air cutters are the most effective.
On edges, the cutting stroke should be in the direction away from the gel coat once again to avoid chipping.
Every five to ten cycles, the mould should be thoroughly checked and any repairs carried out to wear on flange boltholes, or damage caused by hammering during release.
Fire extinguishers of the correct type, patent eyewash and a First Aid Kit should be readily available.
Robert Brown and Tony Smith are passionate about boats and have the knowledge and the experience to quickly assess and correct any damage to your vessel.
To get that amount of bog id use a plascit bag and partly fill with the catalsed bog and use it like a icing bag the cake decoraters use and pip the bog in a even and consistant thickness so it ooozes out from under the wood all the way along both sides then use that and more bog to cove the corner bothsides from end to end .
With smaller boats when they sit on the trailer the rollers or bunks are where the strakes are most times ! Therefore, it is very important that a good boat with the perfect hull shape is selected for this purpose. Reinforcement materials are supplied in rolls sealed in polythene bags inside cardboard boxes. Every two days, the drum should be rotated by 1800 and the tap removed and cleaned with acetone, to prevent blockage.
Both these additives are supplied in 20 or 5 L plastic drums (not in steel containers because resin reacts with rust) and are used to refill 1 L plastic bottles fitted with a graduated pourer for final mixing. A sharp knife is needed for cutting and since glass reinforcement blunts steel blades very quickly, they should be sharpened often.
This layer can then be filled where necessary with resin putty to remove the shallow indentations, which will show up once the fibreglass skin is consolidated. The more time that is spent hand sanding the plug with wet and dry sandpaper, the better the plug will be. Once the resin has been applied, it can be spread using a washer-type or treaded roller, which helps to spread the resin out evenly and prevent air bubbles from getting trapped between the mat and the resin. The plywood should have a roughened border to improve adhesion of the resin when the bulkhead is bonded into the hull.
Oily hardwoods such as teak should be degreased with acetone and the moisture content of all woods checked before use. For large holes use a tank cutter or hole saw or drill perforations around the circumference of a large hole with a drill bit wide enough to accept a jigsaw blade, then saw it out. Wax can build up in some areas to form a thick layer, which gives a dull gel coat, this should be washed or polished off.
Facemasks must be worn when laminating in confined areas and when grinding or sanding cured laminates.
Whether it is a cosmetic problem or major structural issue, Rob and Tony from A1 Custom Fibreglass can provide affordable and effective repair services. Coving and being able to roll you glass into a radused corner add a lot of strength to what you are doing . If you not taking the stringers to there max height to lay the floors onto its ok but remember you have to support and hold the floor up one way or another !.
A shock load is like a really hard slap one when the boat jumps and spray goes out the side a long way .
After the pics were taken I cut the tops off the stringers to remove all the rotten wood in them. Outside the resin room should be a two separate store cupboards for catalyst and for accelerator.
After applying the gel coat, further filling with resin putty and sanding may be necessary for a good finish. This will provide a very accurate joint and will allow boltholes to be through drilled in situ before release.
This allows application of resin and reinforcement, consolidating and curing to take place in rotation.
De-bonding of Fibreglass angles securing structural members, such as bulkheads and frames, is a common problem. It is best to avoid metal to wet resin joints, because if the metal corrodes, it may cause delamination and leaks.
Any bucket of resin producing smoke should be immediately taken outside the moulding shop and filled with water.
Like I said before I'm still in the planning stages of this since putting the project on hold. For larger vessels the plug and mould building is repeated for the deck and interior moulds. In some cases the gel coat layer on the plug is omitted and only cataloy paste is used to fill imperfections. Leave the whole assembly for up to 3 weeks to become fully cured before releasing the mould. De-lamination through resin contamination or movement caused by wood shrinkage will make the joint useless. After checking, the rolls, they should be re-sealed to prevent contamination by high humidity. Usually, one layer of satin mat and then CSM is laid up for 1 or 2 layers next to the gel coat. These subsequent layers may be strengthened by the inclusion of a cloth or WR layer which can be laid in the mould at the same time as CSM and which are consolidated together. This saves time and achieves a better bond since both layers of reinforcement are using the same batch of resin. If there are large dry patches, more resin can be applied before the WR is laid on as better impregnation is achieved if the resin is drawn up rather than forced down through the reinforcement.
It is important that the opposite side of the hull should be moulded in sequence with the first side. Light sanding and cleaning may sometimes be required between layers to remove any protruding pieces of resin and glass, which may prevent a smooth bond with the next layer.

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