Re: Is a Vang Really Useful on a mid to Large Boat?
From your pic, I might agree with Classic 30.
As I see several issues with your vang set up. (could be the angles of the pic, too)
1. the vang's connection to mast is higher than the absolute base of the mast. Looks like the geometry was chosen so that the present vang would clear an opened hatch. Getting the mast connection lower down will greatly help the vang generate more 'down' force on the boom.
Rx - do a trial with the vang pinned to the very bottom of the mast AT the coachroof. You can 'tie' a stout line around the mast base with a 'loop' (alpine butterfly knot, etc.) as the trial attachment point (w/ hatch closed).
2. From the pic, and I may be wrong, but I see a 5:1 vang being used @ 4:1 in the 'up' direction and 5:1 along the 'horizontal' direction, ..... the 'tail' of the vang seems to be running along parallel to the mast; and if so, the 'tail' is generating NO 'down' force !!!!!?????
Rx - even the vang control line should be run directly to the very 'base' of the mast.
3. Do a trial with the vang attached to the boom via 'strops/lashings' and with the 'strop connection' closer to the mast. A vang that makes a 45° angle with its boom will generate 40% more 'downforce' than a vang that makes a 30° angle intercept. (Of course when the attachment point on the boom comes closer to the mast, the 'moment force' becomes greater - a tradeoff, but should be investigated.) Your boom connection 'seems' to be a bit far aft on the boom.
Other - I often 'vang sheet' my boats (one has a Garhauer 'rigid' vang) when racing or just messing about. I initially pre-set the vang so that the boom meets the mast at a 90° angle (87° to be exact, as I have such marked on the vang control line). I can 'ease' the vang at will and under all wind strengths; but if the sail has a lot of developed wind pressure I can hardly ever be able to pull 'down' on the boom with a vang (10:1). To pull down with the vang (in above 'light-moderate' conditions), I always have to momentarily 'unload' the mainsail, reset the vang to the 'mark', then 'load up' again (takes few seconds). I dont know of many vang systems that will allow a fully loaded and drawing mainsail to be 'tightened' when the sail is 'loaded and drawing' (except when beating and the mainsheet is being over-tensioned, on purpose).
Usually most vangs require the mainsail to be 'unloaded' a bit before 'pulling in' on the vang.
Last edited by RichH; 01-30-2014 at 12:19 AM.