Hi,

i have replaced several panels on various GPs.  Is your boat a Series 1 boat with buoyancy bags? Up to hull number about 13200 or a newer Series 2 boat with buoyancy under the floor?  First I would buy a set of the construction plans from the Association office, for which ever type of boat you have, this will let you see how the bottom panels and the keel are constructed.

The keel piece is fitted after the bottom panels are fitted, so to remove then one would normally remove a section of the keel so that the ply can be removed and the new ply fitted to the hog ( the inner part of the keel).  The ply can be replaced between any of the frames I would normally identify the position of the frame and cut through the ply along the middle of the frame so that the existing ply panel and the new ply are supported on the frame, you could also try a half joint where you taper the old and new ply over a length of about 50 to 75mm over a frame.  All new ply and joints should be made using SP epoxy 106 resin and fillers and all new wood coated with epoxy to ensure no further rotting. After fitting the new bottom panels refit the keel .

what you are planning is not an easy job but is not impossible providing you have a good work space under cover if possible.

Good luck and let us know how you go.

Matt,

i have dug out my copy of the plans and on Sheet 3 of 4 the keel to hog bottom ply detail shows the ply under the keel but there should be enough width in the hog, the inner part to clean off the bottom panel and fit it to the hog without removing the keel.  I would check the width of the hog along the part you want to replace to see how much of the hog you will have as the landing for your new ply.  You will also need to remove the bilge keels, these screw through into the frames.  Along the chine the bottom ply is screw glued to the inner chine stringer and the outer chine piece sits in a notch and is planed down to match the bottom ply.  You may need to replace part of the outer chine piece just depends on how cleanly you can remove the old ply, it may be best to cut into the inner chine stringer and refinish the outer chine piece to match the new ply.

if you get stuck for buying a set of plans I do have a set of my own which I could trace the details for you, email me at scorbet@btinternet.com if that helps

Steve

1) Use something hard for your bilge keels. Obeche is too soft.

2) You’ll want to fillet your joints, glass tape can trap moisture which then cant escape. fillets are stronger.

3) it might be worth drilling some holes into the keel to see what the core sample is like. If its dry and doesn’t want to come off leave well alone. if its wet then its worth encouraging it to come off. Wet and rotten are not the same thing, the front 3ft of keel on mine was absolutely saturated with water. I took it off, dried it, and replaced the same wood. I then plugged the holes with some mahogany. Its. better safe than sorry here as water can bleed down the ply and degrade the glue joints to the structural frames. Epoxy is better, but it still happens and you’d be surprised at how much cascamite is used in boats that you’d automatically assume are epoxy throughout.

Mast step conversion;   if you  have it,  the mast step will be a metal track,  with pins across it to determine the fore-and-aft location,  and the foot of the mast will be a tenon which fits into the track.   The track sits on a longitudinal member which is raised above the hog,  and which is tenoned into the centreboard case;    the purpose of this redesign is to spread the load over a greater length of the hog.    Although it won’t be obvious without actual measurement,  the mast is also 12 cm shorter,  to take account of the raised position of the step.

If you don’t have the mast step conversion the step is a square mortise in a wooden block which sits directly on the hog,  and the foot of the mast is square,  rather than having a (rectangular) tenon).

Oliver

ash and obeche are not dissimilar in colour once aged a bit, both are a paleish yellow. Ash has a more obvious grain pattern. The stringers *might* I suppose be ash, its not especially heavy and a GP is a heavy boat but I’ve yet to see a 12xxx numbered hull with anything other than obeche stringers.

Obeche is also significantly more prone to rot, so I’d say if they’re rotten they’re almost certainly obeche. We had a similar quandary with the stem on my boat which was very rotten and we couldn’t decide between the two – Alistair confirmed it was obeche.

I think the simplest joint,  and perfectly acceptable,  would be a butt joint with a ply backing piece.

A good reference source,  indeed the standard reference book (so far as there is such a thing),  for all epoxy work is the Gougeon Bros. manual;   https://www.westsystem.com/the-gougeon-brothers-on-boat-construction/

Oliver

Yes,  you can safely use paint stripper.

Some are better than others.   My own favourite is one of the oldest,  and probably the most aggressive,  Nitromors Original.   Be aware that it is pretty ferocious stuff,  so use with all proper care.    Apply it to only a small initial area;   Ian Proctor recommended just one square foot if I remember correctly (in his 1950s book Racing Dinghy Maintenance),  allow it perhaps 5-10 minutes to soak in (Proctor recommends using this time to re-sharpen your scraper),  then paint a different small area,  and then scrape the first area.     Keep going in a sequence like this.

Allow about 5 minutes to soak in,  perhaps 10 minutes at maximum;    certainly not the 20 minutes sometimes recommended;   the stripper will evaporate if left that long!

Your scraper needs to be seriously sharp at all times.   If you use a conventional scraper you will need to re-sharpen it every few minutes,  and there is a technique to getting it sharp enough.    However that need has been overtaken by modern technology;    use instead a scraper with a modern tungsten carbide blade,  and then you won’t need to re-sharpen it after every few minutes’ use,  (and with that material for the blade you won’t be able to sharpen it anyway),   so you could now work a sequence of three or even four areas all on the go at the same time,  each at a different stage of the sequence  –  always provided you can keep track of where each patch is up to.

Nitromors nowadays offer several different formulations,  designed for different substrates,  so that they can be sure not to damage more delicate substrates.   However the gentler ones are correspondingly less effective at removing paint.    Personally I always use the toughest of the lot,   their Original,   and work on the principle that if there is a substantial thickness of paint it won’t penetrate right through with the first application;     and once you get down to the level where it will penetrate right through it will have been fairly weakened by attacking the paint,  and it won’t remain in contact with the epoxy long enough to do it any serious damage.   However you are welcome to take a more cautious approach,  using a gentler paint stripper;   but the job will take significantly longer,  and will be significantly more work.

-o0o-                    -o0o-                    -o0o-

Adding pictures;   I think you have already found the mechanism,  but you need to re-size your photos first.  A box between the typing pane and the “Choose file” button states that the maximum file size allowed is 512 kB.    That is quite small if your photos are originally taken at high resolution intended for printing,  or for projection onto a large screen;   but it is in fact amply good enough for the size that will be displayed on this forum.   Use any photo-editing program of your choice to re-size your photos;   you probably have one (or more) already on your computer.

As one tip for re-sizing;   you may find that your photo-editing program allows you to set the image size in pixels,  rather than the file size in bytes.    Try 1000 pixels for the longest size,   save to a different filename (so that you don’t spoil your high resolution original),  and then either try to upload that or  –  if you wish  –  right-click on the file icon first and select Properties to check the filesize.

Hope this helps,

Oliver

She is looking good.

Well done.

Oliver

Looks good – and not an especially bad job on one of these. I think making the patch bigger makes it easier to be honest.

Keep it up – the boat looks well worth saving.

I think you are right in saying that you have managed to avoid the worst of the curvature.

The curvature of the extreme forward end is probably about the maximum that the ply will accept  –  Jack Holt seems to have had an exact appreciation of what he could and could not get away with in this wonder new material  –  and Bell Woodworking’s recommended technique for that forward piece was to pour a kettle of boiling water onto it.    I think that is in their book “Home Boat Building Made Easy”,  and I feel sure it is also in Searson Thompson’s cine film of the build process.

On which topic,  I saw the film some years ago (converted to video),  probably at Dovey Yacht Club,  Abderdyfi;   and also film of the launching of the prototype at Aberdyfi.    I cannot now be sure whether this was all in the same film,  or whether it was two separate films.    Does anyone know whether the Association has a copy?    It is something which we ought to have,  and it would be great to have it available on the website.    There may of course be be only one copy,  in the possession of Searson’s estate,  unless they have already passed it on.

Oliver

Yes;  or,  at least,  sections of it.

I presume that you mean the keel itself,  i.e. wood,  rather than the metal keelband.

If you feel that you will need to remove a section of the keel,  do it before you fit the new plywood;   also remove the plywood under the keel,  and bring the new plywood right up to the centre line.

First use either a heat gun or paint stripper,  plus scraper,  to remove the paint;   that will expose where the screws are,  albeit that what you will most probably find is circular patches of filler which will then have to be dug out to reveal where the screws themselves are.

Remove the screws.   That may be easier said than done;  if they were originally brass they will almost certainly now have lost their zinc content,  ending up as porous (and very weak) copper.  heads may well fall apart under the influence of a screwdriver,  shanks may snap,  …    At worst,  you may have to drill them out,  and then make good the resulting holes later.

Cut straight across the keel,  coming as close as you can down to the plywood,  but ideally not cutting into the plywood;   normally it is better to stop just a fraction short rather than go too far.    (However this is unimportant if you are replacing the plywood anyway,  and epoxy is a wonderful thing if you do inadvertently end up cutting a fraction too far …).    My preferred tool for that job would be a dovetail saw,  but there are alternatives,  including a hacksaw,  and an electric oscillating saw.     Perhaps the least preferred acceptable option is a tenon saw;   a dovetail saw is like a smaller version of a tenon saw and with finer pitch to the teeth.   My one was picked up second-hand on Fakenham market …

Then chisel away the section to be removed.    Eventually replace with new wood.    If the length to be removed is substantial,  you might prefer to remove the majority of it with a router,  but I suspect that hand tools may still be needed to finish the job.   

Routers became relatively commonplace for DIY woodworkers only in the last few decades,  and it was only last year that I finally bought one (second-hand,  from Fakenham market   –   and I have still not yet had occasion to use it);    by contrast,  it must be perhaps 50 years since I last had occasion to remove a section of keel.   Hence I naturally think in terms of hand tools,  but by all means update to whatever technology you have available.

Hope this helps,

Oliver

Basically with the bands off if it falls off its got to come off! Beyond that the glue join will be degraded so gentle encouragement should see the borderline wood come away. If you are towards the ends of the boat I’d go all the way.

Mine was at the bow and wasn’t actually rotten, just extremely wet. I drilled holes in it to establish the extent of the wet timber, cut at an angle (Not especially steep) and used a wide chisel to remove the section which was just over a foot. The only things holding it on were paint and nails, the glue had gone completely.

Re assembly was the reverse of removal and I used the same wood – once dry it was fine. I filled the core sample holes with plugs from an old GP side bench (Rotten mk1 GPs are an excellent source of good quality hardwood).

What I should also say is that you’re not just removing the keel to dry and replace the keel. What is underneath is actually far more important and fiddly to repair if it goes wrong. That was why I took the keel off mine, it was wet, not rotten and would have dried on its own in a week or three. What was underneath the keel however was also sodden and would have taken many months to dry. Also I was unaware of it until the keel was off and by now it would probably have rotted the play out again and we’d have been back to square one.

I’m a big believer in only doing this sort of work once!

Agreed.    When I took a section of keel off,  for access to the centreboard case securing screws (as the first step towards removing the case in order to deal with a bad leak),  it was around fifty years ago,  and the boat was not as old as your one.   I had momentarily overlooked the possible state of the glue on your one.

Yes,  there is a sporting chance that the glue will be so degraded that just gentle encouragement (perhaps with the aid of a chisel flat to the bottom between keel and plywood) may be sufficient,  once the screws have been identified and removed.

Oliver

Well done.

I would guess that the non-radiused corners of the bailer are for ease of manufacture,  particularly in the twin context of controlling manufacturing cost (and thus keeping down the price that you pay),  and obtaining a reasonably watertight seal.

Oliver

Port self-bailer looks further forward than starboard one;   that imbalance is bound to slow you down at least 3%  …

(Only kidding.)

Very well done so far.

Oliver

Ive just picked up a Duffin Mk1 13063 thats destined for the bonfire. Case, hog and floor rotten. The rest of it looks very good, it looked great until the floorboards came out! Its been left with the water pooled around closed bailers which I suspect is what happened to yours too.

I did wonder if there’d be any takers for it as a Mk2 conversion but I doubt it. Shame.

the best stuff to use is 1mm Lexan. You’ll get it off eBay, just watch the size and make sure it’s big enough. No hinges are required with this stuff and the best way is to use one piece to cover both holes I think. You can cut it with good scissors or a band saw.

Generally if these are leaking its because you’re sitting too far back in the boat.

My limited experience of capsizing series 1 boats back in the sixties is that after a capsize you can expect them to come up half full of water.   Transom scuppers were introduced to deal with this problem.   Most of my personal experience was with a boat with buoyancy bags throughout,  including the bow,  and one thing that I learned from a deliberate experiment in flooding the boat is that you need the maximum possible bow bouyancy to enable the transom scuppers to do their job.   If you have just the minimum bow buoyancy permitted,  as I had when I tried this experiment,  when you come to sheet in to attempt to sail her dry there is a real rik that she will instead simply submarine.

However if you have the maximum possible reserve bouyancy,  including a bult-in bow tank and the largest possible side and quarters buoyancy bags,   that is a very different situation,  and I am prepared to accept that the transom scuppers may well then work well.   You have the benefit of at least the built-in bow tank,  and I would recommend that you fit the largest buoyancy bags that will physically fit under the side benches and in the quarters.

In my case,  in the sixties,  having cut the transom scuppers I never then used them for real.   In the light of my experiment I did fit the largest bow bag that I could get into the space,  and I carried a plastic bucket;   following a capsize I would then use the bucket to bail about half the water out before using the self-bailers to sail her dry.     When I later had another series 1 boat early in the Millenium,  which did have a bow tank plus seriously large buoyancy bags,  the opportunity to see how well the transom scuppers worked never arose.

Oliver

I’d probably make the flaps out of one piece and secure in the middle – the rudder retraining clip would be an adequate fixing point. They’d look like a figure on 8 on its side.

As for in use the last time I capsized a mk 1 GP was many years ago in a boat with a bow bag. I dont recall the flaps being much use. A bow tank is not only more buoyant, it keeps the water from sloshing all round the boat and this is vital to getting the flaps to work. I think in a bow tank boat they’ll work pretty well.

I think 2x 36×12 bags in the back and 2x 34×9 under the benches was standard. But its been a while!

Once you are ready,  you don’t need to necessarily capsize in order to test the system.

Choose a day when there is a decent wind,  around force 4.   (Anything less,  and you have no right to be inadvertently capsized anyway).

Choose favourable conditions,  and/or ask your club safety boat to stand by.

Then sit stationary in the water,  open the transom flaps,  and allow her to flood.

Then sheet in on a beam or broad reach,  and attempt to sail her dry.

Either it will work,  or it won’t.   But at least you will know.  And if you choose suitable conditions and/or have a safety boat standing by you will not be at any risk.

With generous reserve buoyancy I would hope,  and cautiously expect,  that it would work;   but it would be good to know for sure.

Oliver

Take Oliver’s advice and carry a bucket.  Sod’s law states that the force 4 which tips you over could drop to 2 or less when you need to sail it dry.  I would also retain a bungee to keep the flaps closed.

Norman

It has been said that one of the fastest methods of all to remove water from inside a boat involves a frightened man with a bucket …

Oliver

T-shaped piece of wood:  so idea.   Sorry.

Cam cleat;  these can usually be stripped and cleaned,  but to the best of my knowledge the individual parts are not normally marketed.    However the cost of replacing the complete fitting with new is not exhorbitant.

“Back in the day”  –  i.e. c. 1970,  when I had Barton cam cleats for the genoa sheets (rather larger than your ones) the plastic jaws were softer than I hope modern ones are,  and in seriously competitive racing the teeth wore out quite frequently.   But in those days the manufacturer did market replacement jaws,  and I used to get through about two sets per season.  However I am sure that those days are long gone.

Oliver

Those are Harken ones. You can get the springs, I think P&B do them. If they don’t give Harken themselves a call and see if they’ll help.

The whole fitting is actually quite expensive compared to most but they are very, very good and well worth keeping.

We live and learn;   I am happy to stand corrected.

Oliver

I’ve just checked, they’re part no HSB56 and readily available.

About £3

Unusual these days!

piece of wood could be a (very) thin mast gate chock.

Looking again at the wood the grain is running in an odd direction for a hardwood chock. This implies that it was once plywood, has been marinading in the bottom of the boat for ages, has delaminated and fallen apart. Most GP chocks are about 8mm I think. I made mine out of tufnol. If you use that as a pattern I would significantly reduce the size of the T as it’ll get caught on the Genoa sheets.

If for any reason you can’t resurrect the cleat the Harken ones knock spots off all the others and are well worth the extra cost.

• This reply was modified 5 years, 2 months ago by Chris.

Glad it went so well.

She looks to have been well worth saving;   and as an added bonus you will have expanded your own skill set and will have more confidence for any future repairs.

Oliver

Its a Duffin hull.

Well worth saving, well done!