One of the most important and vital design tools to create a new cat or tri is the weight/trim spreadsheet. I always use it in tandem with the hull lines program. It’s not that inaccurate to say that knowing how long a boat is does not matter at first. I have my magic hull proportions, and I have weight and payload needed. Ideally, the length is a result. I cannot imagine doing it any other way, but I still encounter builders, even boatyards, who are happy to storm ahead without a weight study. That profoundly amazes me. I know of one professional builder here in my state who prefers to start with hull patterns, and then he freestyles the design from there. Utterly amazing. I even offered one to him for $100 and he declared that he didn’t want to waste his money. (a complete one takes some 10 to 20 hours to flesh out)
Knowing what it will weigh, how it trims, and what it can carry are the most important foundations in any design as I see it. In a series of loops, the hull lines are updated to reflect the excel data. Then the new hull information goes back into excel and tightens that up.
The final hull lines and patterns should only be created after everything else important is designed. Understand that it takes mere seconds to parametrically revise a hull. I know that not everyone agrees with this, but I cannot understand why not.