## onsdag 1 augusti 2012

### Matematik och segling: Mathematics and sailing

Det finns en massa matematiska formler för olika begrepp och faktorer inom båtvärlden. Speciellt en formel fascinerar mig, den kallas överlevnadsfaktorn och den räknas så här:

Överlevnadsfaktorn( survival factor) = Båtbredd(meter) / Deplacement( ton) ^0,33
En båt med ett värde större än 2.0 ska hålla sig inomskärs och undvika öppna havet enligt formelns upphovsman, Peter Ibold, Brittisk båtkonstruktör.
När jag räknar på min båt så får den koefficienten 2,36. Helt plötsligt känns det lite osäkert att ge sig ut och segla! En Alacrity 19 bör väga mer än 1,3 ton för att klassas som sjösäker ute på öppna hav enligt denna formel.

There are a lot of mathematical formulas for different terms and coefficients in the boating world. Especially one formula fascinate me, it's called survival factor.

Survival factor = The boats width (meters) / Displacement (tons) ^ 0.33

A boat with a value greater than 2.0 should stay inshore and avoid open sea, according to the formula creator, Peter Ibold, British boatbuilder.
When I count on my boat, the factor went 2.36. Suddenly, it feels unsafe to go out and sail! The Alacrity 19 should weight more than 1.3 tonnes to be classed as seaworthy on the open seas under this formula.

#### 2 kommentarer:

1. It's not all bad. There is a lot of water inshore and you will do a lot more sailing where all your skills are required than someone who goes offshore for the same amount of sea miles (not my words by the way). All those islands and places to stop at and see, OK not the Caribbean but you don't have to take a lot of time off work to get there. Add to that the fact that you can go where bigger boats can't and everything is cheaper you are set to have a lot more fun for your money :-) (not my words either but worth repeating) and you don't need a crew. Then again Alacritys have proved themselves to be capable of more.

You have not given Peter Ibold's definition of inshore but the Recreational Craft Directive gives it as Category C - Inshore: Designed for voyages in coastal waters, large bays, estuaries, lakes and rivers where
conditions up to, and including, wind force 6 and significant wave heights up to, and including, 2m may be
experienced. When buying flares, an inshore pack is for use up to 3 miles from land, coastal is up to 7 miles from land and an offshore pack is for use over 7 miles from land.

2. Hi David!

I agree with you. I was not really worry about my Alacrity 19 seaworthy. I will probably alway sail inside the Stockholm archipilago and almost certain that the day I will cross the Östersjön to Åland or Finland I have a bigger boat.

PS Today I have picked up a used rubber dinghy wich I bought from "Blocket" for 700 SEK, cheap for a rubber dinghy isnt'it. My plan is to use it when exploring new landing places. DS

regards Thomas S