{nell hall}

Thought I’d post a fun work-in progress project I wrote up last year. hydrostatics is a little Python package mostly based on Gmsh that allows for sailboat hydrostatics and stability calculations.

I wrote this package because DELFTship doesn’t do inclined hydrostatics, and for sailboat design that’s absolutely essential. Right now the core functionality allows you to import an STL file, solve for the neutral waterline for a given displacement and heel, and from there calculate properties like the righting moment vs angle (a.k.a stability curves), volume, center of buoyancy, etc.

In lay terms, the stability curves tell you how much force is required to heel a boat to a given angle… and even more importantly, how much the boat will push back to upright at that angle. Inclined hydrostatics are also essential because, unlike with big container ships that mostly chug along totally upright, sailboats sail at significant angles of heel for significant periods of time (basically all the time upwind in more than a couple knots). Which is to say, if you only look at performance when totally upright, you’re missing a pretty big part of the real-world picture.

The first image above shows an example of a solved waterplane for a given heel angle; the second shows stability curves for a variety of displacements and heel angles, all at neutral trim.

Future functionalities I’m planning to build in once I have a little more time are:

• Form coefficients (prismatic, block, etc.)
• Station areas
• Waterplane characteristics

The package is now live on GitHub with documentation hosted here on my website. Check it out!

Made my way back up to Port Townsend for Fiddle Tunes, the annual festival up at Fort Worden.

Highlights of the week:

• Midwestern jam at the mule barn (pictured)
• Learning that most of the music I’ve played over the last couple years with Joe and Charles is secretly midwestern, even when it’s not
• Thought I was missing pride to be here but kept ending up in jams with oops all trans women
• Dancing and playing music until 2 am

Lowlights of the week:

• Busting my guitar

It’s like Catullus 46:

Iam ver egelidos refert tepores,
iam caeli furor aequinoctialis
iucundis Zephyri silescit aureis.
linquantur Phrygii, Catulle, campi
Nicaeaeque ager uber aestuosae:
ad claras Asiae volemus urbes.
iam mens praetrepidans avet vagari,
iam laeti studio pedes vigescunt.
o dulces comitum valete coetus,
longe quos simul a domo profectos
diversae varie viae reportant.

I think I’ll be back next year!

The head of the bow is one of the big ``cruxes’’ for me of the bowmaking process. While other aspects like the camber and graduations more directly affect the feel of the bow when played, the shape of the head really defines the feel of the bow artistically.

In the above, you can see my latest bow head in process. In the first two images, I’ve defined the first of the chamfers used to control the shape of the head. Part of why this is the crux of the process is that these must flow dynamically, gracefully, and be a perfect surface – very hard to do!

In the latter two photos, you can see the finished result. I’m pretty happy with it, though I think there are some things I’ll do differently next time. This head draws pretty strongly on those of Persoit, and I really wanted the start of the arête (at the top of the head) to be quite strong. I would actually like a shorter, more delicate bec in the next one.