15/08/2021 at 8:47 am #22271
I believe I have a Mk2 GRP GP14 with a plywood centreboard and was wondering if anyone could provide some inside whether it’s a bottom or top removal and whether there’s any suppliers that could replace the centreboard given mine broke/split yesterday afternoon?
15/08/2021 at 12:40 pm #22273
I would expect that removal and replacement is similar to the Series 1 wooden boats; remove the pivot bolt (accessible from inside the boat) and then put the boat on her side, and withdraw the board from either above or below (whichever is the more convenient).
However the GRP boats are not my sphere of expertise, and my real reason for responding is the replacement board.
First, avoid plywood like the plague. At one time it was popular for centreboards, primarily because it is a (relatively) cheap and very easy way to make one; but the material is fundamentally unsuitable, which is why it breaks. Plywood is specifically designed to be equally strong both along the board and across it; but the crossed ply construction effectively does that by averaging, so it is not as strong along the board as plain board of a suitable wood would be. And nearly all the load on a centreboard is in the one direction, along the board; there is no great need for strength across the board.
For many years now, whenever I have heard of a centreboard breaking in use I have asked whether it was a plywood one – and thus far I have scored 100% !!
The best construction for a wooden centreboard (or rudder blade) is solid wood, laminated out of strips a few inches wide, and laid side by side. These strips should all be cut from a single length, and alternate ones turned end for end, to eliminate any tendency to warping.
I am reasonably sure than any of our registered GP14 builders can supply a new centreboard, and Milanes specialise in making foils for a number of classes http://www.milanesfoils.co.uk. Speed Sails (no longer trading) used to produce glassfibre foils, but you may find another builder producing them. But be prepared for the price to be eye-watering, whether wood or glassfibre; there is actually a fair amount of work involved in producing something that may superficially look quite simple; think £400 – £600 as a ball park range. If you do order new, be very sure that your chosen supplier knows that yours is the early pattern centreboard; the current (Series 2) version is not the same, and I am not certain that it will fit.
Alternatively you can keep an eye on eBay; I have the impression that they do come up from time to time, although there is nothing listed there currently.
If you have good woodworking skills you can make your own, using epoxy to laminate the strips together. Any specialist marine timber supplier (e.g. Robbins, Stones, Sykes) will supply suitable timber, machined to size, and Robbins certainly will deliver nationwide; I suspect that they all will.
After the woodwork is finished you may wish to sheathe the board in a single layer of fibreglass for protection (using woven mat, and epoxy). If so, remember to allow for the thickness of this (on both sides) in making the board. You may wish to do a test on a small piece of scrap wood before you order the timber, to ascertain the thickness of the sheathing.
Hope this helps,
16/08/2021 at 9:24 am #22274
Thank you for providing all this insightful information. I will certainly be able to get to work and will explore the marine timber suppliers as well. Having checked for replacement centreboards, a wooden replacement is £390 and a Milanes Foils one is £520 so will look to create my own replacement.
Many thanks again for responding.
16/08/2021 at 9:44 am #22275IanParticipant
For removal/refitting… Tip the boat on her side, put the centreboard fully down and mark where it sits. When you replace, just line up the marks and the holes should all align. However… if you’re going to sand it down and re-varnish, these marks will be lost, so…
After removing the bolt, and before removing the centreboard, put a long piece of strong thread through all the holes. and tie it in a big loop. Take out the centreboard and pull the thread through. Cut the thread and tape it in place. When you come to refit the centreboard, tie the thread through the bolt hole on the centreboard. It will already be through the bolt holes on the centreboard housing. Then when you guide the centreboard into place, simply keep pulling on the thread and you will end up with all the holes aligned and the thread running free. It’s MUCH easier to drop the bolt in at this stage and avoids any frustrating “Hunt and peck” techniques. 😉
16/08/2021 at 10:34 am #22276
That’s an excellent tip and most certainly will put that to use by using the thread method.
16/08/2021 at 4:55 pm #22294sw13644Participant
Raoul, If you’re making one yourself, you may want to make one from the plans as there’s no guarantee that the one that you have is the right shape. You can get the plans from the GP14 Class Association.
The pictures are of a Utile/Redwood laminated centreboard finished to 18mm with 1mm each side of epoxy laminated glass, varnished to protect the epoxy from UV.
16/08/2021 at 5:19 pm #22299
Good to see you coming in on this.
As our resident early GRP guru, am I right in my initial comment that “I would expect that removal and replacement is similar to the Series 1 wooden boats; remove the pivot bolt (accessible from inside the boat) and then put the boat on her side, and withdraw the board from either above or below (whichever is the more convenient)”?
16/08/2021 at 6:30 pm #22309sw13644Participant
Oliver, as with so many things, it depends… because people have made many legitimate modifications to their GP14s. Some owners have glassed the centreboard pivot into their boat to stop the pivot from leaking, and changed the method of installation to the way that the later models fit the centreboard. (1)
Either the pivot comes out, or the centreboard has a fillet which is accessed through the slot. See the picture below.
As for whether the centreboard comes out from below or above, the decision can be made easily if the centreboard has door-stops as a handle, because it’s then easier to get the centreboard out above. As for the string trick earlier in the posting – I fully agree that this is a good way of settling a replacement in the right place. – Steve
(1) and one owner glassed the pivot in, and had not changed the centreboard mounting method, and it was not possible to remove the broken centreboard without resorting to a grinder 🙂
17/08/2021 at 9:16 am #22322
Thank you Steve/Oliver for all the insights and sharing your experiences.
Thankfully my pivot bolt is not glassed in so this will help the removal and the thread method sounds like a winner.
I won’t have time to remove the centreboard prior to my holiday next week but will keep you posted on my return and when I’ve got the centreboard out.
17/08/2021 at 9:50 am #22323
Just a further thought about the thread method, which I agree sounds like a winner.
If you are making your own replacement centreboard there may possibly be a significant interval of time between taking the broken one out and having the finished replacement ready to fit. In that scenario, despite all care there is the risk that the thread may get displaced. We hope it won’t be needed, but if needed I can see a possible method of re-threading, based on the method which I have seen Speed Sails (as was) use for threading the main halliard down a new mast.
Make up a wooden batten with a hook on the end, put the replacement thread straight through the two bolt holes (using an improvised wire “needle” if needed), with a good long length of thread protruding on each side, then use your hooked batten to pull out a loop through either top or bottom of the casing.
19/09/2021 at 9:00 am #22514
As promised I’d keep you informed of the progress on the centre board. It turned out to be a laminated centre board (not a marine plywood as mentioned in an earlier post) and it was a clean split from one of the laminated planks.
Thankfully, a good friend of mine who was with me sailing when it happened is a DT teacher and he said he could fix that easily when the board was out.
The 3rd picture is the centre board in the school’s workshop and he’s fitted 3 biscuit joints and glued it back together using 4 sash clamps to hold it together.
It’s back now and ready to be sanded and varnished and ready to be put back hopefully in time for an end of Sep/end of season sail.
Thank you for all your suggestions and advise which is really appreciated.
19/09/2021 at 10:00 am #22518
The right construction, fundamentally strong, and the split was due only to the failure of one of the glued joints and is easily repaired.
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