Gestalt said..mark62 said..
The numbers aren’t strictly correct, the boom length varies depending on boom height, shorter with a low boom and longer with a high boom. Most people simply adjust the boom length accordingly after setting the down haul, so the printed numbers aren’t needed.
The idea that boom height makes a difference is attractive, but it doesn't stand up to maths.
Pythagoras theorem kills it. Say you have a small wave sail with 150cm outhaul and the boom perpendicular to the mast in the middle of the cutout.
Moving the boom up or down by 10cm changes the length to the clew by 0.3mm.
Even a 20cm deviation results in only 13mm change.
The change is relatively smaller as the boom gets longer. At 200cm a 20cm move on the mast is only 10mm at the clew
It’s got nothing to do with Pythagoras fwiw. It’s about how the sail loads are transferred differently depending on boom heights. Next time you stop to adjust outhaul maybe adjust your boom height instead. It does the same thing more or less.
that aside sail designer recommend adjusting outhaul to suit boom height. As a group we need to stop telling people to ignore rigging instructions.
with my sails 0.5cm outhaul adjustment makes a noticeable difference.
Whilst Pythagaros lived on the windswept Greek Island of Samos, he clearly didnt windsurf much. When I change my boom height, the outhaul string either tightens or loosens.
