I have taken a question from another thread and going to give it a place of its own...
wokelliott said...
A question on mast rake. I notice that all the L/yachts have mast rake almost to an extreme angle whereas water based yachts have near vertical masts except that some Cats do have some rake.
Is it to position centre of pressure rearward or does it provide helpful wind flow? An old colleague and experienced sailor friend has suggested that in the case of Cats it can help lift the bows to avoid a nose dive. I would think that is not a problem with the land yachts as a more vertical mast placed rearward would achieve the same thing.
Increasing the mat rake does 2 things, it move the CE further back and also lowers the CE. (CE=Centre of Effort)
An upright mast / sail gives better lift, this is shown around in other things like high performance gliders, High performance hang gliders etc... but they actually have a very fine 'best' angle, by raking it back it give a more forgiving sail.
Swing wing aircraft do exist and use use best of both principles, the F1-11 used by the military was / is designed as a swing wing bomber that opens the wings up at lower speeds to create greater lift but at speed the wings move back to have a more stable air craft at speed.
Many years go the class5 rules just limited the mast length with maximum mast tip height from the ground, people then found they could get around the rule by raking the mast back, (this class5 rule now measures mast length + height from the ground to the mast base)
The Manta design yacht uses a VERY raked mast making the yacht a very forgiving and easy yacht to sail.
There are many good books written on aero and hydrodynamics of sailing by C. A. Marchaj that are worth reading.
en.wikipedia.org/wiki/Czes%C5%82aw_Marchaj
