Some boards (like the Dragon 13'9" ) I like heavier and some lighter. If the design is good then weight isn't an issue unless it reduces the buoyancy too much, so it is related to board volume. I don't use a length to weight ratio. I've gone up to 70 pounds on the Dragon, and it handles everything I took it out in including triple overhead ledging reef waves, but it isn't for the faint of heart. The Dragon I built last year could have been made down to about 35 pounds but I beefed it up to 50. For boards up to 12 feet there's no harm in going as light as you can though.
Malibu type shapes are very sensitive to weight changes because of the imbalance of the aft turning position, more balanced designs with a more central riding position handle weight better.
If you want to go light a 1/4" deck and bottom with lightweight cloth under the deck ( I use nylon) with 3/8" frames at 4 inch centres and less rail blocking inside the board is the way to go. I've been using paulownia which makes life easy in this respect, but have used heavier woods in the past. Denser woods can be used with lighter scantlings ( thickness etc) but this does require accurate work.
My 10 weighs in at 44 pounds. The only time I notice the weight is the carry from the car to the ocean. By the way I have been passing it around to friends lately and I get rave reviews. They absolutely love the board and the way it rides. The most recent holder reports 75 yard rides. Not bad for the surf out here latley. Also the board grabs more attention than a beached whale. My buddy says people see the board while driving by, stop get out and walk to the beach and ask " Holy **** is that a Roy Stuart surfboard!". Very cool!
A nice looking concave Steve. The weight isn't a problem in itself provided that it doesn't reduce the buoyancy too much. With paulownia I can get a 12 foot board at 24 pounds if I want to go light.
How thick is your planking?
Hey Roy, not sure if you were asking about the 6-6" PP which started this thread or steve's PP long board. I Used 5/16" for planking. I wanted robust but now that its reading 30 lbs I feel as though there are ways to make this build much lighter.
I'm using western red cedar. That's the lightest wood available to me. I considered clear pine but decided on cedar. All the guys at grain surfboards use cedar and rave about it. Grain is literally a mile from where I live / work