150kg vertical leech load
100 diameter thin wall steel boom
10mm round bar steel vang
20ish mm round bar "spreader"
2.5m boom
400mm gooseneck to vang take-off
Conventional Boom
Bending Moment
Deflection = 14.5mm
Luka Boom Arrangement
Bending Moment
Deflection = 13.2mmA little over a tonne of tension in the vang in the conventional arrangement and a little under a tonne for the Luka setup.
Is it worth the complexity?
Sounds like a good NA-type talk:
ReplyDeleteMoths: are they worth the complexity?
Lucky the states aren't at easter, hate to try and fit under that in a light wind race when you start going into windward.
ReplyDeleteYou missed the point that the attachment point of the vang is further aft on the boom than normal so the bending moment for the same leach load is substantially less, or more likely the moment is the same for more leach load without breaking the boom.
ReplyDeleteMoving the attachment point act with a regular vang flattens the angle and adds to local stresses due to higher compression loads on the boom.
Yep missed the critical bit
ReplyDeleteConventional vang BP is at about 650mm from GN pin
Spreader vang BP is at 1100mm from GN (at bridle point)
Hence a lot less vang load required to achieve the same leech tension
Also another critical point. Boat is designed to take the extra load. I am pretty sure this would void any production boat warranty.
ReplyDeleteHa ha pwnd! Sux to be smart and wrong
ReplyDeletescrew you markla!
ReplyDeleteagreed it is a slightly stiffer arrangement with same vang attachment position on boom.
agreed it is stiffer with a long vang attachment position on boom, which this extra angle allows.
disagree with "a lot less vang load". it is significantly affected by the boom length and king post length, which doesn't appear to change between setups. the slight change in angle has minimal effect on the vang loads.
bit of an argument about the vang loads. can't be "a lot less vang load" and "designed to take the extra load". the load directions change slightly at the gooseneck and king post, and their magnitude is slightly different.
The loads all depend how much you are prepared to pull the rope, and what your original intention was.
ReplyDeleteare you saying the current setup cannot achieve enough vang load?
ReplyDeleteor
are you saying Luka has a different rig setup that requires more vang load?
Or are you saying that luka is a pussy and needs a setup that lets his weak pretty boy hands effectivly pull more vang on.
ReplyDeletehahahaha!!!
ReplyDeleteI would never say that.
title amended, credit where credit is due
ReplyDeleteThinking of putting a kink into my straight boom and adding a vang. What factors affect the decision on vang position on the boom and vang strut length?
ReplyDelete