SIB hard floor wood repair

[jimbo341]

I recently purchased a second hand SIB (aquaquick 320) that uses a 4 piece wooden floor that slots together. I used it at the weekend and although we hit some moderate waves fairly hard, it was only a few times and the rest of the time was spent either planing smoothly or at a calmer pace.

Hower, I noticed that the rear panel now has a big crack in it from the edge running about 20 cm inwards. The crack goes all the way through and is just before the end of the side rail. There is another crack forming on the other side of the panel in roughly the same place.

Is the wood used in these boats normally so fragile or was I just unlucky?

Most importantly what are the repair options for this sort of damage?

Can I try to glue it with epoxy or would that not be strong enough. A neighbour suggested I put some metal plates above and beneath the crack to act as a brace and put rivets through. Would this work in combination with glue?

I guess my other option for piece of mind is to buy a piece of marine plywood and cut a replacement. Is this preferable or could it just snap again in he future without some form of reinforcement?

[Fenlander]

Hi and welcome to the forum.

Usually the wooden floor panels will go the life of a SIB unless they get water in them and delaminate. The main thing that can cause a crack such as yours is under inflation of tubes/keel. As it sounds like the crack is close to the end of the alignment given by the side stringers I wonder if this is the case?

Regarding repair I’d cut a new panel from ply but structurally almost any “patch” would do the job if you are happy with the look. Just beware nothing on any patch can rub the boat’s material where there otherwise wouldn’t have been contact.

[Steve509926]

For the time and trouble taken to attempt a repair, I would replace the whole panel with a new one. Grade "A" quality exterior ply is more than sufficient providing it is well sealed. I would seal it with a few coats of epoxy resin.

[jimbo341]

Thanks for you help guys. The boat was inflated to 0.25 bar at the sides and 0.5 bar in the keel as per the instructions. There was still some slight give in the sides though so maybe the pressure gauge on the pump is off.

I am having difficulty sourcing A grade plywood where I live.

The nearest boat shop have Mahogny plywood with B classification glued with water-resistant WBP glue. This is quite expensive.

The local builders have construction rated spruce plywood with Moisture Resistant Adhesive WBP glue. This is about half the price of the other but only has 4 layers.

Is it possible with the cheaper plywood or would your recommend the more expensive?

As for the epoxy, I can source epoxy primer relatively easily. Is this ok to use as coating or does it need to be penetrating epoxy?

[Steve509926]

What thickness is your original plywood floor panel?

[jimbo341]

original thickness was 12mm (size of panel is 880mm x 530mm x 12mm)

[Steve509926]

I would expect 12mm exterior ply to have a minimum of 5 but usually 6 plies and be hardwood not spruce.
4 layer spruce ply would normally be used in construction where the the finish isn't important, hidden structures, used for shuttering - pouring concrete, or making packing cases.

I would not use it for a floor panel in a SIB.

The term WBP refers to the adhesive, Weather - Boiling Point. It means it can stand up to being subjected to weather and heat (boiling water), however it doesn't mean that the wood plies are protected. The ends and the surface of the ply must be protected, either paint, varnish or epoxy resin - I've used this in the past which ships from Germany so I believe they will ship to Oslo. (https://www.epodex.com/en/product/ep...ourless-(clear))

If you can't get good quality hardwood exterior ply, then I would use the expensive marine ply.

[Peter_C]

Photos are worth a thousand words.

It might be possible to laminate a sheet underneath to reinforce it??