FRP cracking – a problem ?

GP14 Sailing Forums Forum FRP cracking – a problem ?

This topic contains 15 replies, has 5 voices, and was last updated by  Oliver Shaw 9 months, 1 week ago.

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  • #18673


    I am new to sailing and considering buying a GP for club sailing / racing and family fun sailing.

    I have seen a FRP GP14 for sale but it is suffering from some cracking / crazing on the deck. Is this a worry ? Structural problem or purely cosmetic ? Is it fixable or does it not need it ?

    What should one look out for or consider for a first GP

    Thank you in advance for any advice offered


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  • #18675

    Oliver Shaw

    Although my primary expertise is in wood I do have at least some experience in GRP.

    That damage looks to me to be more than cosmetic,  and it certainly needs repair;   especially the region in the bottom of the photo just right of centre,  where it appears to me that there is a complete hole in the outer layer of the laminate,  exposing the core.    One must assume that the cracks covering the remainder of the photo are similarly deep,  at least until such time as it is proved otherwise.    Although that hole actually appears to be the result of very local damage to the gunwale,  and it may possibly be the case that the cracking elsewhere is unrelated to it,  until it has been thoroughly investigated I would assume the worst.

    In principle,  anything is fixable,  but this looks to be more than a trivial job.

    If I were tackling the job,  and I have done what I think are rather bigger jobs on my yacht,   I would grind away all the damaged material,  leaving a tapered edge (to provide what in woodwork one would call a scarf joint,  with a recommended gradient of 1 in 12).   Personally I prefer woven glass reinforcement,  whether mat or tape,  rather than chopped strand mat,  both because I think it is stronger and because I find it easier to ensure full penetration of the reinforcement by the resin.   Then coat with epoxy resin,  and lay up new epoxy GRP,  layer after layer,  tapering the repair to match the tapered hole,  until  you have built up to the original surface contour.    Use epoxy,  not polyester (it is stronger,  and adheres very much better),  and use a metal roller to achieve high packing density of the reinforcement in the resin.   Your choice whether to finish with gelcoat or with paint.

    Use hand protection and eye protection;   the latter is particularly important.    My information may now be out of date,  but back in the seventies (using polyester resin,  of course,  rather than epoxy,  and with the hardener in use at that time) there was serious concern that even the smallest speck of hardener in the eye would cause irreversible and progressive eye damage which could ultimately result in blindness.   I would hope that this no longer applies with today’s materials,  but I don’t know,  and better safe than sorry.

    If you are well used to large scale DIY repairs this is not desperately daunting,   but if not you may well find it daunting.

    The best and most authoritative manual on such repairs is probably the Gougeon Bros. one;

    However the considerable amount of work needed on this boat should be reflected in the price you are prepared to pay.   Conversely,  if the price is not tempting you may well be able to find a boat in better condition within your budget.

    Hope this is of some help.



  • #18676



    I would say that this isn’t structural actually (Sorry Oliver), but is certainly not a 5 minute job to put right if you were wanting to do it properly.

    This looks to me like classic UV/heat damage where the boat has either been left uncovered or sweating under a PV cover. There is an old repair in the middle of the photo, but this is not the root of the problem.

    To fix it you would need to remove all of the affected gelcoat and re-apply, or – significantly easier -paint the decks. There shouldn’t be any need to apply glass, this only affects the gelcoat.

    Does it need doing? No, not really

    Would it bother me? Yes.

    Would I buy this boat? No.

    Hope this helps 🙂

    • This reply was modified 10 months ago by  Chris.
    • This reply was modified 10 months ago by  Chris.
  • #18679

    Oliver Shaw

    Interesting that Chris and I have different takes on it;   I did say that my expertise is primarily in wood,  and I defer to Chris’s possibly greater experience of GRP boats,  but I also note that we are both working from just a single photo.

    I think that we are agreed that neither of us would buy that boat,  unless of course the price was very tempting and adequately reflected the work needed.

    I am reminded of an article that I read around forty years ago by Hugo de Plessis,  an expert yacht surveyor and one of the leading authorities on fibreglass construction,  who sadly died last year at the age of 94.     I was struck by one of his comments about stress cracks,  which I appreciate is not what we are seeing here,  but it nonetheless illustrates the difficulties of diagnosis.     He said that they  often tell a story,  and that actually seeing them clearly is a notoriously fickle exercise which is heavily dependent on lighting conditions.    He stated that it is not unusual for a fully competent surveyor to give a yacht a clean bill of health,  and then for another surveyor a few days later who sees her when the sun is in a different direction to condemn her outright!



  • #18693


    Many thanks for the comprehensive replies. I think I’ll pass on this boat.

    I wanted a FRP to try to avoid a lot of maintenance…

  • #18705


    FRP/GRP doesn’t necessarily mean low maintenance – just different maintenance.

    Even relatively new FRP boats have a lot of ply in them in key areas to add reinforcement for fitting attachment, local high stress etc. These can and do rot out (Poor coating) and can be quite expensive to put right. Look closely for signs of this, the through deck sheeted boats have a particularly awkward piece where the Genoa track sits under the deck and is a common failure.

    You will struggle to find an entry level series 2 FRP hull that doesn’t have some gelcoat damage similar (But not as extensive) to the one you’ve seen. GPs tend to be built with a thick gelcoat layer and polyester resins and gelcoats shrink over time which leads to cracking and star crazing especially on the decks. If you press the panel and its stiff this is nothing to worry about (And if you fix it it’ll probably come back weeks later) if its soft this is definately structural damage and will need to be sorted.

  • #18718



    I would back up the warnings from Chris – be very warry when buying a FRP boat that shows any signs of cracking.  I had a very bad experience with a Speed FRP boat No 13954 – the plywood reinforcements rotted and left me with some big bills to sort the boat out.  Areas where you need to check – under the thwarts front and back, under the decks for the plywood supports to the genoa cleats (if through deck sheeting), inside the transom the rudder pintle reinforcement rots, under the mast there is a block which supports the mast, on the sides of the boat are two pads each side one for the shroud plates and one for the genoa sheet turning block.  All the plywood in my boat was either rotten or well on the way to failing.

    Superficial gelcoat dings are par for the course and are easily repaired – also open up the forward hatch and look around the front buoyancy tank, if possible have a friend shine a light around the outside of the hull – you may see some thin areas in the lay up particularly along the keel, another stay away sign.

    Over a period of 12 months I had all these parts renewed by Steve Parker at a cost of about £2,000 before I decided to call it a day and bought a new boat from SP Boats.  I wrote an article about these problems which was published in the Spring 2018 Mainsail – some FRP boats seem to be OK but there are a number of boats with all or some of these problems.  Check carefully before buying.


    • #18719

      Oliver Shaw

      Steve reminds me of the utterly superb polyestermite hoax;   the discovery of a newly mutated gribble worm which devours glassfibre,  which feeds voraciously,  and which in particular eats glassfibre boats.

      After a comprehensive survey of the problem,  one of the articles about it ended with a comment to the effect that there is however one foolproof solution to the problem.   Expensive,  to be sure,  but 100% effective.   Sheath the boat in wood.

      Steve’s contribution represents yet another reason why I prefer wooden boats …



  • #18729


    Thank you all again for the pointers.

    How do I recognise the defective or rotten ply ?

    Colour ? Soft to touch ? Crumbling ?

    Is it easy to “see” all the likely suspect wood ?

    It is more of a minefield than I thought buying a GP 🙁

  • #18730

    Oliver Shaw

    Seriously,  don’t rule out buying a wooden one.   At least you can see what you are getting,  the performance is indistinguishable between wood or plastic,  and if you put in the TLC to put a wooden boat into top condition she will be a thing of beauty.

    The latter can be achieved with an elderly and cosmetically tired but still sound boat if you put in the TLC over a winter.



  • #18733


    To find the rotten ply can difficult as it is all hidden. The best way is to get your hands into these hidden areas and rotten ply will crumble when touched.  Access to these areas involves looking as:

    under the thwarts – check that the sheathing glass layer is intact – if not feel the ply under the thwart also look for cracks at point where the flat part of the thwart meets the side of the deck.

    under the decks when fitted with through deck sheeting, is the plywood to which the track is bolted secure

    Open the hatch cover in the transom knee and reach inside to the inside of the transom, check the piece of ply which runs up the centre of the transom

    open the hatch covers either side of the mast and reach in with a screwdriver and try to push into the block under the mast, if sound zero penetration

    But as Oliver says if you want a cheap GP 14  wooden series 1 boat with round transom scuppers is far easier to check for condition as you can see every thing the only hidden area will be the front buoyancy tank if fitted.  Only other check needed on an old boat is under the mast check that the keel/hog has not split due to having high rig loads applied.



  • #19001


    On our FRP club boats I’m struggling to find the ply reinforcement eg looking under the thwarts I can’t see any ply…

    I wanted to find it so I can familiarise myself with the reinforcing ply locations ready to check it on prospective purchases.

    Any advice or pictures welcomed to help finding the ply locations ?

  • #19014


    Hi sorry for slow reply but not been at home. If you email me I will send you a collection of horror pictures too many and bid for the forum email [email protected]

  • #19015


    Most ply in FRP boats is encapsulated. You will not find it by simply looking under the deck, but look for raised square or rectangular areas of reinforcement.


    A further issue with the cracking above, it looks to me like too thick a gelcoat on a flexible FRP hull. Gelcoats are quite stiff, if the glass beneath it flexes, it will eventually crack the more brittle surface above it.


    As for Oliver’s advice on wooden GPs.. ask him how many of the original 100 boats are still around and in use. My own was built in 1964 and what little rot I found was dry rot on the decks where the varnish had perished and exposed the ply to the weather while the boat was in storage for almost three decades

  • #19016

    Oliver Shaw

    How many of the first 100 GP14s still around and in use?

    An interesting question,  and unfortunately I don’t have access to the data while I am away cruising;  the relevant speadsheets folder on the tablet appears to be corrupted.   But it is an impressively large proportion,   provided you accept that for many of them their use will now be only occasional;   and these are seriously old boats,  dating from 1951,  so next year will be their 70th season.

    Legend has it that Jack Holt expected a new GP14 to last 25 years,  so these vintage boats are now approaching three times that figure.

    Famously,  Roy Nettleship,  while manning the Association stand at the boat show in 1969,  was asked how long a GP14 would last:     “I’ve no idea,  the design’s only 40 years old!”



    • #19017

      Oliver Shaw

      The tablet has now condescended to open the files correctly;   no idea what went wrong at the first attempt.

      So:  …

      Six out of the first ten boats are still around,  of which Quiver,  no. 3,  is not currently seaworthy and is in my possession awaiting my attention for a major restoration.   Sadly,  no. 10 was destroyed in a workshop fire at Don Marine some years ago.   That leaves 50% of the first 10 boats still around,  still believed to be seaworthy,  and still in occasional use.

      Of the first hundred boats,  I have records (not necessarily fully up to date) of the whereabouts of a further 12 of them,  and so far as I am aware they are all in occasional use.     There may well be more that I don’t know about.

      So that gives a total of at least 17 of the first hundred boats.    Not a bad preservation rate,  in my view.



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