Day 9
Days remaining: 225.

Mental Math.

Truly Awesome.

(But never raced in fleets of 100+ did it?!)

It might seem like an easy boat to build, but a foiling moth is a mathematical nightmare... Just figuring out wing angles and where the wings are going to go on the boat, and where the mast is going to go, where the foils go through the boat and at what angles ... It's all a moveable feast - Open rules you see....  I know it was a bigger deal, but the REAL Blackbird would have been easier in some ways... No rules at all... (apart from physics and gravity)... Also, the SR-71 was going to tear through the sky in glorious isolation, with the odd SAM to have a pretty one sided drag race against...
Not race in fleets of over 100!

Of course you can copy what's already going on - and indeed there are some very fine boats out there.  I have massive respect for the current top designs - bearing in mind how long the Mach 2 has been King of the Hill for example.... But if you copy every detail of the boats you are racing against, you are just about guaranteeing that your boat won't be any faster, and also I quite like my mates that designed and market the Rocket and the Mach 2 etc, and I'm looking forward to having a beer with them, and the conversation not starting with 'So, Dave, tell us about which bits of our boat you DIDN'T copy!'

SO... Back to the math of my Blackbird.  Volume is a pretty straightforward bit of integration, ie As the boat is 11ft long it's pretty easy to calculate the volume of each 1ft section and from there you are home free.  Mast to centreboard position is pretty easy too. We're dealing with some finite numbers - sail area, positions of centreboard and rudder, and centre of buoyancy mean you're pretty much strapped down to a small range of positions from the moment you pick up your pencil.  What I did struggle with was some tooling to guarantee one of the most obvious, yet influential parts of the boat: Wing angles.  The sweep back angle is pretty straightforward, and the rise angle I can copy from the rest... but you find yourself trying to figure out what the included angle between the 'stumps' that will be fitted into the boat and how to hold it all still while the glue goes off. Get them wrong at such an early stage of the build and the wings will be wrong... and that would make the whole boat just awful to sail - and it would all go back to getting a simple bit of geometry wrong months before.

Welcome to my world!

Off for a run to think about it..


D