My fish has hardly any rocker at all. It sort of resembles a door.

Sounds like an interesting project. Have you checked out what Feral Dave is doing at Diverse? If you go to his shop in the Gold Coast, you can see one of his hollow boards half-way through construction.

I found some pics here: diversesurf.com.au/?categories=wood



Dave has designed the ribs on a computer and he's getting them machine cut. I think he's going to offer them as a kit for people to buy and build at home.

I can measure the rocker on my fish if you like. Where would I take the measurements from?

dl that would be tops if you could measure it. just set it on a table with the fins hanging off the end. measure the dist from the table to the nose. then for the tail rocker measure from the top of the table to the ground, then from the ground to the bottom of the tail at the end and subtract the two.

thanks for the help
btw what length is your fish.

My fish:

4" nose rocker, 1" tail rocker (exactly).
Dimensions: 5'6", 20", 2 3/8"

However, with a quad fin fish, you have to go REALLY short. I borrowed a 5'7" quad from Diverse a couple of weeks ago and I could hardly turn the thing. It went super quick on fat waves, but I couldn't sink the rail enough to get a decent turn. 5'2" would probably be the right size for me (I weigh 65kg).

Kearnsey and Cpt. Bob both have longer fishes, but they are probably not the "old school" type.

Remember, it is about total board volume. So if you are going super wide (+20") with boxy rails, you need to keep the length down otherwise you'll end up with something you can't turn.

To estimate the volume of your board design, try using this tool: http://aps3000.com/software.php?p=download_design_version
Aat 65kg, I'd probably go for about 27L for a quad fin fish.


"

Mine is actually 6'6 20 3/4 2 3/4 epoxy

Gets up and goes quick, and turns fine but I also weigh 100kg so can get enough weight to get the rails in. Would deff go shorter if I weighed less.

It's a webber fatburner so is actually classed as a semi fish.