Springy Decks

[Vitalba]

I have a small area of three quarter inch ply deck (about one and a half sqft) which has delaminated.
Has anyone expirence of or knows of a suitable repair technique as replacement would be a major job ?
I can`t see why a series of say .375" holes through all but the bottom layer of the ply and filled (and topped up) with "slow" epoxy should not, with the encouragement of a heat source, permiate the various cavities between the laminations. A tappered plug could then be tapped in just prior to the epoxy going off.
Come to think of it, it should not be too difficult stimulate the distribution with the aid of pressure from a bicycle pump.
Thoughts and comments would be appreciated. VITALBA.

 

[Poignard]

I'd recommend this book:-

"002-970 Wooden Boat Restoration And Repair.
A complete guide to restoring wooden structures, improving the appearance, reducing the maintenance and prolonging the life of boats. Chapters include localised dry rot, basic frame repair, hardware bonding, skin repairs, protection and maintenance. Softcover over 60 pages and numerous diagrams and drawings."

This book covers plywood repairs in great detail.

Available from www.wessex-resins.com, who are the UK agents for WEST Epoxy.

 

[Vitalba]

Thanks for your quick response and I agree "002-970" is an exceptionally useful booklet and if my question has done nothing else it has brought it to the attention of the Forum.
It does not, as far as I can see, cover the type of repair I envisage.
I hope this does not mean I`m the potential Christian Barnard of the Trampoline Deck ! VITALBA.

 

[npf1]

I've got what sounds to be a similar issue, but in the cockpit coamings rather than deck: the fibreglass skin is OK, but the plywood in between has got damp and is rotting in some places.

Last year, I attempted to do as you suggest: drill a series of holes then fill with epoxy. It was a total waste of time because the rotten plywood was a damp mush, which was not possible to entirely remove through a the drill holes. On top of that, around the rot there was a whole area of damp plywood that's not yet rotten. In both these cases, using epoxy would have been a waste of time unless I could have somehow dried out the area fully - which I couldn't with the crap weather we've had.

I still have the problem and have come to the conclusion only way to successfully cure the problem will be to cut out the entire area, including the damp but not yet rotten area, and then rebuild it, using what i can of the current fibreglass skin.

Not a job I'm looking forward to, but seems to me to be the only way of knowing that the problem will be solved once and for all.

I'd be interested to hear of any other experiences with plywood rot, especially where it's not possible to dry it out fully.

 

[KenMcCulloch]

I think the method you propose has significant potential pitfalls. Getting the epoxy to penetrate all the voids will be very difficult indeed and you would also need to apply pressure on both sides once the epoxy was permeated through the structure but before it had gone off. Quite difficult I think. Cutting out the failing section and scarfing a new piece in should not be so very difficult and also enables you to fully confirm that you have in fact cut out all the delaminated section.

 

[Tranona]

You don't say whether there is a beam under the damaged area, nor whether there is any significant curvature. These two factors will have a big influence on possible repairs. As others have said, the inner layers are likely to be damp, and the rot may extend far further than you imagine.

This thickness of ply cant be replaced in such a small area if there is any curvature, so you are into laminating, and even then getting 6mm to follow a curve without significant support is not easy.

I carried out a similar size repair on my deck - half inch - in two layers of 6mm, but I had two transverse deck beams for support and shape and put in fore and aft cleats to take the new first layer. I got most of the rotten core out, but I find if you leave it to dry thoroughly you can stabilise it with epoxy. This is more useful on vertical panels where gravity takes the epoxy further into the core.

There is no easy way - you have to remove as much rot as possible and stabilise the surrounding areas. Your proposed method would only work if the core and cavity is dry - and it almost certainly wont be!

 

[Seagreen]

For the equivalent expense and effort involved with either approach, the least time-wasting and most effective will be to cut out the affected area and replace. You could cut the deck out to the first unaffected beam and scarfe a piece in. To be honest, its often less hassle to cut out and replace more area than less. This will also ensure that you have got all the rotten wood out.

Notwithstanding any curvature problems, I think this will be the best approach in the long run.

 

[Tranona]

Depends on what is in the way. If it is clear deck then you are right, but often there are boring things like hatches that get in the way. That is why I used the method I described because the amount of sound deck (actually coachroof) to remove to get a good one piece replacement would have been about 5 times as big as the bit that was rotten! Remember also that in good ply construction the ply is glued to the beams, so not easy to remove cleanly.

 

[Seagreen]

As they say, it all depends. A picture would help greatly.