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Delaminating Bilge Board

Started by RogerH, August 14, 2021, 07:12:11 PM

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Hello all,

after a long period of incapacity I'm finally back to being mobile enough to start looking at the boat and getting her ready for sailing. The poor thing has been sitting on the front garden having been used a total of twice, four years ago, before my health and mobility went south. As a result she's a bit forlorn!

I've got the trailer well in hand - new bearings and brake shoes - probably at least one new brake cable as well.

While crawling around underneath I saw that the starboard bilge plate has delaminated to an alarming degree. I have not looked yet as to whether or not the boards are removable - my boat is Jenyatan, no.37, so it's a 50:50 chance I think.

From other forum posts it seems the boards are made of glass-sheathed ply with metal inserts - is there any resource I might access for how to repair or build a new one?

Many thanks,

Roger Harris

David Bone

Hello Roger,
I know WB#37, 'Jenya Tan' from Colin & Jayne Firth's ownership.
She has the original glass fibre boards, swivelled on a pin moulded into the casings within the hull.
Removal and repair/replacement is going to involve cutting away a section of the side bunk sections for access to the pin.
From previous 'forum' entries, I suggest David Cawston, WB#15, has the best knowledge with which to advise you in this respect.


Thanks David.

I?ve read David?s post on repairing the housings and am assuming the work to get at the pins will be similar.

Best dig out the angle grinder and Dremel…

I hope David sees this and can advise on how to remove and re-fix the board.

I used to work with boats so, although a little daunted, I have a good idea of what to do. Once I’ve freed and repaired the board (or made a new one) it would seem sensible to re-install with an eye to subsequent further removal in the event of damage - and to modify the other board at the same time. I’m thinking waterproof access hatches.

I’m wondering if anyone has done that hefore?




Hi Roger,
Very worrying photos of your bilge plates.  I have never seen any of the early grp plates with even a hint of delaminating.  The plates on Markie are 34 years old and are as good as new.  But Markie does spend most of her time on a trailer (unfortunately) in our back garden.  I do not know of the internal composition of the plates, I assumed they were just grp, but I suppose there could be a steel insert that has got rusty, swollen and 'blown' the grp.  Looks like a case of getting the plates out and taking to your local grp fabricator, or having plywood/steel shoe (or grp/stainless steel equivalent) plates as fitted to later WBs or aluminium plates made up.
The grp type plates are not designed to be easily removed, so to get the plates out, you will either have to access the bilge plate housings as per my method of cutting the interior moulding, so you can get at the glassed in pins, or somehow from underneath make a vertical slot up to the pivot pin, in the raised plates, like the later plywood/steel shoe type have.  That could be tricky if there is a steel insert. To remove the later type plates I believe you have to pivot the plates so they are vertical and can then be slid off the pins.
Good luck.


Hi Dave,

Thanks for the reply.

Yes the plate doesn't look good, lol! But many years ago I worked for Prout Catamarans and am not worried about doing glasswork.

I also spent some time in the yacht charter trade and have a good working knowledge of the systems, repair and construction of grp boats.

All the above to let you know I'm happy to have a go at it, but also happy to take as much advice as is on offer!

As a start, I'm thinking about cutting an access panel at least to see how the land lies - my first thought is to cut the top out of one of the starboard side berths - as far from any potential water ingress as possible - where to cut fore-and-aft andathwartships is an issue. I can measure it, but if you know the location of the pins, realtive to the interior mouldings, it would help a bit!

I' thinking that if i can locate the pin it might be possible to grind the glass off and drive the pin out or perhaps lift the pivot end of the board and get at the pin more easily?

Of course, if it's necessary to remove the inner mouldings I'll happily do that, but the more up heaval I can avoid the better.

Any advice welcome :-)



David Bone

Good luck Roger, you may be the first to tackle this job but are unlikely to be the last.
Sounds like your skills are well up to the task and you will probably end up with a better job than original.

John Burton

Good luck Roger, I hope it goes well. If your plates cannot be saved and you decide to copy the later plywood plates with the iron shoe at the end, then you will end up with plates significantly lighter than the earlier ones like you have. I copied David Bone?s method of routing out recesses in the board to accommodate an extra 8 kg of lead, I think David added a little more than that. I then glassed over the whole structure. This transforms plates that actually have positive buoyancy ( when one of mine came adrift it floated to the surface ) to heavier ones that make the boat much more stable. I looked longingly at Gerold?s beautifully crafted aluminium plates until I realised the cost involved!
Keep us all posted with your progress, I hope it goes well.


Thanks gents. For now the plan is to just get the board out and see if I can effect a repair which will last to the end of the season. Technically I hope to go sailing in September!

Then the winter job will be to get both boards out and replace with something heavier - perhaps adding some floors to take the sideways forces. When this occurs I'll probably take the inner mouding out in 3 pieces and re-do the glass joint round the board casings.

I'm open to any advice or input. If Dave Cawston is still looking - do you have any experience of the glassed-in ones? Is it a feasible idea to grind the glass away from the upper side of the pins and remove them?

First thing will be to cut an access/viewing hole in the saloon seat - I'm not sure how close to the centreline the boards are - or to put it another way, how far outboard they are from the inner face of the saloon seats.

Hopefully someone on here will know otherwise I'm going to have to measure-and-guess!

Then I'll be able to see how to drop the board. Once out, a grinder plus a lot of CSM, followed by a lot of sanding...



I've had a good look around outside and inside - I think the pin will be under the area highlighted in the photo.

The plan is to cut out an opening similar to that marked, leaving enough lip to fasten flanges underneath so the cutout will fit back on them.

The area is filled with expanding foam by the looks of it.

Does anyone have any experience removing this material? Looks like a hacksaw blade (or maybe a bread knife) and lots of mess to me, lol! The plan is to remove it piecemeal and expose the pin, with enough room to work.

Any thoughts or comments?




Looks like a good plan.  Yes removing that section will reveal the glassed in pins once the foam is removed.  If I remember correctly, the foam was just loose blocks packed in, so it should be an easy job to remove.

David Bone

On WB107, the board casings are sited close to the inboard edges of the bunk housings, angled slightly inwards towards the top.   See: 'The Hull,' Page 2, 'Day Boat Centre Board Jammed,' Reply #6, for illustration.


Thanks for the continuing help gents.

David Bone - thanks for the steer there. It looks to me as if the board casings are very close to the inboard face of the seats - this might make it difficult or impossible to get a grinder or other tool in between the board casing and the seat-front to remove the glass holding the pin in place.

Dave Cawston - do you have any recollection of how big this gap is? Long time ago now, I realise :-)

For the benefit of anyone else following this post I've attached the photo from the "Day Boat Centreboard Jammed" post as mentioned by David Bone in the previous post here. You can see from the photo that the rods installed come out very close to the front of the seat, suggesting if I only take the top off the seat I will have very little room to work in.

I'm still loath to take the entire mouldings out - they will add significantly to the stiffness of the hull - so I'm still toying with the idea of cutting out a panel. The other photo here shows my current thinking. Firstly, to cut out an L-shaped piece extra art shown in blue) to allow better access to the inboard side of the pin. But that might not give full access if the pin extends inboard under the floor, so perhaps I might need to extend it across the floor a little - extra shown in green.

This is getting a bit more nvolved than simply cutting an access panel in the top - but unless I take out the entire moulding I can see no other way.

It all rests on whether or not the glassing to retain the pin extends under the floor - Dave Cawston can you remember?

Any further thoughts, David, Dave or anyone else?



EDIT - also, how far aft are the pins from the end of the vee-berth? It may be I don't have to cut right back to the locker recess?


Once again for the benefit of anyone following the post, I?ve managed to answer at least one f my queries.

The bottom edge of the board is somewhere between 12? and 13? from the centreline. Allowing for the fact that they are angled off vertical I estimate the top edge could be 2? - 4? inboard of that, so between 11? and 8? from the centreline.

The inboard side of the saloon seat is about 6? from the centreline at the approximate location of the pin. This means I?ll have somewhere between 5? and 2? clearance with which to work between the board casing and the seat front 

Depending on how the pin is retained, 5? or a bit less could be enough - if it?s glassed over either end like a Drascombe. So the current plan is to cut a round access hatch over the area and probe through the foam to find the top of the board casing. With luck that?ll tell me what size of cutout I need to make.

Fingers crossed!


I cut the access hole and was pleased to see the top of the board casing is pretty-much where I expected it to be.

Even better, the pin is retained by glass patches over the ends of it, so removal of those patches will be (relatively) easy and I'll be able to expose the pin.

Driving it out might be an issue - I intend to support the weight of the board from underneath the boat and drive the pin out from the side. I'll need to cut a further access hole on the seat-front, but it's looking promising.The inboard side of the retaining pin is visible as a glassed-over lump on the inboard of the casing - I need to remove the foam on the outboard side to check it's the same - I see no reason why it wouldn't be.

Photos will show what I mean, I hope!


Well it?s taken me a couple of days but I got the board out ? well, almost (see later)

I cut another access hatch this time in the side of the saloon berth ? giving direct access to the board retaining pin. This hatch was far more difficult to cut as I couldn?t get any kind of saw into the small space between the hole and the floor (and the hole and the aft end of the Vee berth) to cut. I got the jigsaw in from 9 o?clock to 3 o?clock but after that it was chain drilling and a Chinese rasp.

I was then able to get my power file into the hole and dig around for the pin. A bit of guesstimation ended up nice and accurate and I exposed the inboard side of the pin at my first try! Chuffed.

Further measuring and guessing bore equally satisfying fruit and I got the outboard end of the pin exposed in quick time.

I went back outside and supported the board  at the pin end ? I have no idea how much it weighs and I didn?t want it dropping out of the casing wioth the pin partially removed, potentially deforming the pivot hole in the board or the holes in the casing. I also made register marks on the board and hull so I would be able to line it up to re-mount it.