Meranti Plywood

[timeandtide]

Hey fellow builders, I have seen the builders updates with the laminate schedule for a Meranti plywood hull and deck although I had my Rudder and Daggerboards cnc cut along with my kit. They were also made from laminated Meranti plywood and I am curious about the layup schedule for these items. So, how much glass for a meranti rudder and daggerboards?

[timeandtide]

I am just going to use the 450g/m2 required for the hull plating.

[brucel]

Don’t forget about the vertical reinforcement strip of fibreglass

[martellmarine]

The rudder structure is not in the same category as the hull structure. One of the draw backs (limitations) of the CG5580 set of plans is the lack of detail associated with the laminate schedule. While the Meranti hull can technically get away with the 450gsm skin as a general water proofing and abrasion membrane with a little bit of 'strength' added to the mix, the physical structure (dimensions, planform, thickness etc) of the rudder is different than the hull skin and the rudder is being 'asked' to do a different job.

In my opinion, using the hull laminate of 450gsm is not enough. At the very least you would use a min 430gsm double bias (plus/minus 45 deg) finished with a min 200gsm boat cloth, but would prefer to bump the DB up to 600gsm and the cloth to 290gsm for a total of 900gsm for the Meranti rudder. The Vertical reinforcement strip should be spec'd as unidirectional with all fibres running vertically.

My reasoning for the above is that using ply wood as the core of a rudder (foil) renders 50% of the wooden fibres doing nothing to resist bending forces and therefore not contributing to stiffness. Some builders have chosen to use solid wood where 100% of the wood fibres are going in the right direction to resist the forces being applied to the rudder. Adding the +45/-45 fibres with the Double Bias layer will add another layer of strength and stiffness not inherent in the wood core itself. The cloth layer is to protect the DB's and Uni's from excessive sand throughs (when filling and fairing) which potentially ruin their fibre contributions.

Cheers.

[timeandtide]

Thanks Greg, that’s the exact info I was looking for. I also felt like 450g/m2 would be inadequate. I will use these suggestions to come up with a stronger matrix. Thanks again for the response.