Crandall Black Arrow Runabout scaled up 25

[Boatman61]

About a year and a half ago I completed my Black Arrow Runabout, and while it's been a blast, I am already considering doing another build, but this time scaled up 25%, which will provide a bit more room Length 16' 4", approximately 60" beam and accommodate a 20" motor.

My build was modified heavily from the plans, has a self-bailing motor well, full instruments and a three-piece windshield. Performance is good from the 40HP merc showing 42 mph on GPS. I didn't see any reason to buy another set of plans, so I set about doing my own in Solid Works 2D, and working off the original table of offsets.

 

[Boatman61]

 

[gonzo]

On small boats the weight of the crew is a significant percentage of the total displacement. You may have to shift the seat forward to end up with the center of gravity at the same percentage of the length as the shorter boat.

 

[Boatman61]

I can tell you with authority that there is absolutely no issue with the cockpit in it's current place. We're talking about a 25% scaled-up version of a well documented design, When I built my last boat, frames were stretched approximately 3 inches without any issues with center of gravity. I didn't mention it, but I also have a 15 gallon fuel tank mounted forward, and use Nauticus trim tabs.

 

[gonzo]

A 25% scale up almost doubles the volume of the hull.