Thanks for the info. I'll check out the Home Depot stock of red cedar and see what they've got. Home Depot also has "premium" pine, that is completely clear, and comes in lengths up to 8'. I'm not sure of the species, but the sticker on it says the company is in New Zealand. I'm guessing Radiata based on some googling. It isn't cheap, but there would be little waste.

Is there a reason you limit things to one scarf joint? I'd like to make an 18' boat, so I'd need to scarf together three boards to get the necessary length. My understanding is that if done properly, the joints should be stronger than the wood.