Boat Design

Why I over-design electrical systems

Submitted by Matthew on

"Why", I'm sometimes asked, "do you specify electrical stuff that's bigger and more powerful than I had expected?"

It's a justifiable question. Batteries are expensive, heavy and bulky; why would you want any more of them than necessary? And what's with the multiple shutoff switches, subpanels, and other non-typical features of my electrical designs?

Criticality One

Submitted by Matthew on

Anything that people make is going to break. This is inevitable. It's a direct consequence of unavoidable, fundamental laws of the universe.

Part of the art of engineering is to control where, and after how long, things will break. We can't prevent failure entirely, but we can focus our efforts on the most critical items and we can ensure that the complete system – an engine, boat, spacecraft, whatever – is unlikely to fail at all within a certain service life.

The Factor Of Ignorance

Submitted by Matthew on

"Safety factor." It's probably one of the most common, and most misused, terms in engineering.

The "factor of safety" might be better described as a "factor of ignorance". It's a multiplier, applied to loads and/or structural components in a design, to account for things that weren't explicitly taken into account in the design calculations. Those things could include variations in material quality or workmanship, uncertain overload conditions, accidents, and other hard-to-predict conditions that could cause a failure.

Weak Links

Submitted by Matthew on

Is there an advantage to designed-in weak links, where a cheap and easily replaced part fails so that a more expensive one can be saved?
In many cases, there is; nevertheless, we shouldn't apply this design philosophy to everything we design.

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