Latest News: Forums Technical Mk1 – various queries

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  • #3817

    I have just bought a grp mk1 on which I need to carry out various upgrades, modifications and repairs. If anyone can help with the following queries it would be much appreciated – bound to be more to follow over the course of the winter.

    1. Bilge rail protection. What is the correct proceedure for attaching bilge rail protection? I assume a brass strip is the preferred method, plastic being cheaper but probably not up to the job?

    2. Gelcoat colour. Any ideas how on the best way to match up grey gelcoat? I realise I am not going to get a perfect match. My boat is Bourne Plastics, ca 1972.

    3. Does anyone recommend adding any additional bouyancy – maybe under the sidedeck – or are the bow and stern tanks adequate?

    Thanks in advance for any help.

    Jonathan

    #7452
    Anonymous
    Inactive

    @Jonathan Jenkins wrote:


    3. Does anyone recommend adding any additional bouyancy – maybe under the sidedeck – or are the bow and stern tanks adequate?

    One of the great strengths of the MK1 is that it is fairly easy to right and doesn’t have a great tendency to invert. If you put buoyancy under the side decks you will make the hull float too high when capsized, which will make it much harder to right and more likely to invert.

    The front and rear tanks should have foam blocks in them which are theoretically sufficient to prevent the boat from sinking even if the tanks flood. If you want to improve the buoyancy you could add more sealed buoyancy within the tanks, but perhaps the most useful thing of all is to ensure that the tank hatches seal properly and do a full buoyancy test as per the class regs. If both tanks are properly watertight then there isn’t really much to worry about.

    #7458

    Thanks for the comments, I shall definitely check the tank seals and look into the bouyancy test. I probably will add more sealed bouyancy into the tanks as well.

    Thanks
    Jonathan

    #7460
    Bob Harland
    Participant

    @Jonathan Jenkins wrote:

    1. Bilge rail protection. What is the correct proceedure for attaching bilge rail protection? I assume a brass strip is the preferred method, plastic being cheaper but probably not up to the job?

    Here is the relevant piece from the class rules:
    11.4 Keel band.
    (a) Shall be fitted the entire length of keel and stem to stemhead or stemhead fitting, and on both sides of the centreboard slot.
    (b) Material. Durable corrosion resistant metal.
    (c) Thickness. 7 (1⁄4”) maximum.
    (d) Width. 20 (3⁄4”) maximum.
    (e) Additional keel bands. May be fitted, but their weight shall not be included in the hull weight (Rule 25) and they shall comply
    with Rules 11.4 (b), (c) and (d).

    Attaching the band is usually done with short self tappers, There is a possibility that you will need to beef up the grp for the fasteners – but you will find that out when you drill the pilot holes. If so some epoxy filler. If the grp is sound then some sealant will be sufficient.

    @Jonathan Jenkins wrote:

    3. Does anyone recommend adding any additional bouyancy – maybe under the sidedeck – or are the bow and stern tanks adequate?

    The bow and stern tanks are indeed adequate – as long as they are reasonably watertight. Some leakage is permissable under class rules. So a buoyancy test is strongly recommended.
    The catches for the hatch covers can be troublesome if not well maintained, if you were to lose the rear (or front) hatch in a capsize the boat would be impossible to right without beaching. So that is the main thing to guard against.

    bob
    W7658

    #7461

    Bob

    Many thanks for your comments.

    I’m assuming that the bilge rails are wooden strips incorporated within the hull moulding – is this correct? – and that adding some sealant to the screw holes is just to stop water getting into them.

    Both my hatches have attachment points on the inside so I will ensure they are secured to the boat.

    Jonathan

    #7464
    Bob Harland
    Participant

    I am guessing that there will be some wood strips, but if so they may not be in very good condition – hence the epoxy suggestion.
    The main purpose of the sealant is to keep water from ingressing the screw hole into the GRP laminate as well as a wood strip.

    It’s good practice to have a lanyard particularly on the aft hatch – GRP does not float.
    It is important that the catches are secure – if the hatch comes loose during a capsize the aft tank will flood and the boat will be impossible to recover.

    #7465
    Swiebertje
    Participant

    @Bob Harland wrote:

    It’s good practice to have a lanyard particularly on the aft hatch – GRP does not float.

    While cruising you often need to unhook the lanyard to get at the food or to take the sleeping bags out. The hatch cover is then at risk again. I simply glued some Tempex foam to the inside of the hatch cover. That makes the cover float when it should accidentally slide of the boat. You could of course still use a lanyard with this foam solution, I just don’t bother.

    #7484
    RoryD
    Member

    @Jonathan Jenkins wrote:

    I’m assuming that the bilge rails are wooden strips incorporated within the hull moulding – is this correct? – and that adding some sealant to the screw holes is just to stop water getting into them. Jonathan

    Our Mk1 GRP (No. 2590) has no wood in the bilge rails – they are simply hollow tunnels of GRP matting shaped properly on the outside by the gelcoat. They are “attached” to the main hull structure, rather than being integral to the main hull matting. So could be issue in attaching strips with screws as they’re not substantial structures ……. and you cannot access the inside either for bolting. Maybe rivet/epoxy them on ? A good idea to protect them though.

    – Rory

    PS I’m pretty sure our rear hatch lid is double skinned GRP with an air gap in between, so it should float OK – haven’t tried it though.

    #7576

    I’m still going all round the houses on bilge rail protection. Latest consideration is plastic strips which can be glued on (according to sailboats.co.uk)

    http://www.sailboats.co.uk/Product~Plastic_Keelband_Betastrip_Per_Metre_577200.html

    I am tempted to try this as it would avoid drilling into the rails and having to add sealant into every hole to prevent water getting in – to me this seems a big advantage.

    The worst case scenario would be if the strips didn’t stay stuck on for very long – as the cost is (relatively) inexpensive that wouldn’t be a major disaster, just have to try something else. Even if they worked for a while and then had to be re-done this still has the advantage of not drilling into the rails.

    So my questions are – has anyone got any experience of this? and is there anything I might have missed here?

    Thanks
    Jonathan
    W2312

    #7581
    Colin Parkstone
    Participant

    Jonathan,

    I used to work for a boatbuilder who used Beta strip all the time, very good product. Think the glue was a Bostick type.

    Prep the boat well by masking off the area to be glued,abrade the gell with sandpaper and remove dust.

    Put glue on both surfaces and leave to almost dry.

    Start at the bow if doing the keel and have a helper to hold the band away from the boat while you place it onto the glued surface.

    Hold down band with duck tape or a very good tape that sticks to gell.

    When you get the Strip, cut to length and shape the ends with sandpaper, then put in hot water to soften,dry and pull out straight till cool.

    C P 🙂

    #7595

    Colin

    Mant thanks for your encouraging and informative reply – I am now even more tempted to give this a go.

    Cheers
    Jonathan
    W2312

    #7600
    PeterW3035
    Member

    The bilge rails on W3035 were damaged at the front and when the soft matting underneath was cut back I also found them to be hollow. Although they were of substantial thickness and seemed to have been laid up with the main hull.

    To give a solid base for the repair and reduce the risk on water getting trapped in the hull I filled them with expanding foam. Then I repaired the fibreglass on top.

    As the hull had never been fitted with rubbing strips, I didn’t consider fitting any but just decided to avoid sailing up the beach and to keep a careful eye on any damage before it got through the gelcoat & fibreglass.

    PeterW3035

    “there is nothing – absolutely nothing- half so much worth doing as simply messing about in boats.”
    Kenneth Grahame
    The Wind inthe Willows

    #8070
    Colin Parkstone
    Participant

    Jonathan, how did you get on with the bilge keel protection ??

    C P 🙂

    #8071

    Colin – that really is spooky timing as I’ve just done it a few days ago! So far I am very pleased with them. I took your advice about putting the strips in hot water before pulling out straight which certainly helped but getting them straight was the only difficult bit. I had them hanging off the underside of the garage roof for a while with G clamps as weights on the ends which was quite effective. Glueing them on was pretty easy and I then used duck tape – as you suggested – across them to hold them in place whilst the glue dried. They seem to be attached pretty firmly and have survived the first test sail. As I said previously time will tell, but so far very happy not to have drilled any holes.

    Thanks again for your advice.

    Jonathan
    W2312

    #8073
    Colin Parkstone
    Participant

    Jonathan,

    Glad to have helped !!!

    Iv been called Scary but Spooky is a new one.

    No drill holes is one of the reasons I like glue on keel bands,especially for the older boats with hollow bilge keels.

    Happy Sailing,

    C P 😀

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