Lots of choices. If we start with - a non-racing application - fairly stiff mast - no desire for forcing a pre-bend - a small amount of rake - a minimal gap between the mast and partners at the cabin top
then 1 - pick a starting point and block the mast heel. 2- on a windy day, say towards the higher end of the TWS you would carry your largest headsail, go upwind and trim for best speed and point. 3 - most people want a bit of weather helm, and there is some guidance that the rudder should be turned 3 or 4 degrees to counteract the weather helm. If you have lee helm add length to the forestay, too much weather helm shorten the forestay. In my opinion the blocks and mast heel position on a typical cruiser or racer cruiser is then used to adjust the mast position at the partners. With the backstay off going downwind the mast should be able to reduce rack and maybe touch the front of the partners. Upwind under full backstay the mast will move back and touch the back of the partners. > Doesn't the luff moves forward when you move the foot forward? To answer the question, moving the mast heel forward although it increases the rake it does move the whole sail forward and the center of effort goes forward. Moving the mast heel backwards decreases the rake but moves the whole sail backwards. This is exactly opposite to the effect of adding rake by lengthening the forestay ( or tightening the backstay ), which also increases rake but moves the whole sail backwards. The result is if a boat has too much weather helm and the rake is reduced by moving the mast heel backwards it will likely make the weather helm worse. If a boat has too much weather helm and the rake is reduced by shortening the forestay it will likely reduce the weather helm. So why the "likely"? It is also possible that with a bendy mast and an older main that moving the mast heel back could induce pre-bend in the mast which will flatten the main, and cause the backstay to flatten it more. That can help weather helm also. Michael Brown Windburn C&C 30-1 Launched at National Yacht Club on Saturday! Date: Sun, 3 May 2015 10:35:53 -0700 From: Knowles Rich <[email protected]> To: Josh Muckley <[email protected]>, cnc-list Cnc-List <[email protected]> Subject: Re: Stus-List LF38 Mast Placement in the Step Message-ID: <[email protected]> Content-Type: text/plain; charset="windows-1252" Hi All. I?ve been having an offline conversation with Josh, see below. Perhaps someone else might like to answer Josh?s questions as I can?t? Rich Knowles Nanaimo, BC INDIGO LF38 Almost sold in Halifax, NS. On May 2, 2015, at 17:41, Josh Muckley <[email protected]> wrote: Doesn't the luff moves forward when you move the foot forward? The original poster was asking about placement of wood blocks. He had all 4 blocks forward of the mast and the mask back all the way aft. I assumed that in moving the blocks to move the mast forward that this would move the foot forward as well. No mention of changing headstay length so I assumed it to be the fixed point in all of this. Based on these assumptions the trailing edge of the mast and the luff edge of the sail would also move forward but the mast as a whole would have more rake. Right? Josh On May 2, 2015 6:53 PM, "Rich Knowles" <[email protected] <mailto:[email protected]>> wrote: I'm confused. Since the luff is attached to the trailing edge of the mast, if the mast rake increases the luff must move along with it. Perhaps someone else can make more sense if this than I can for you. I'm at work but will post our conversation to the masses when I get home. RK On May 2, 2015, at 15:16, Josh Muckley <[email protected] <mailto:[email protected]>> wrote: > What you said was that moving the mast aft moves the center of effort aft. > Since the original question was about placement of the mast foot being all > the way aft and the consequences of moving it forward I assumed you were > referring to the foot. I had originally stated that moving the foot forward > would increase rake and then mis-stated that increased rake would reduce > weather helm. I was quickly corrected and I conceeded that more rake equals > more weather helm. > > So what is the combined effect of moving the luff edge forward but increasing > rake? The two actions have opposite effects correct? > > Josh > > On May 2, 2015 2:28 AM, "Rich Knowles" <[email protected] > <mailto:[email protected]>> wrote: > Moving the mast aft moves the centre of sail effort aft and increases weather > helm. Simple geometry. > > Rich Knowles > Nanaimo, BC > INDIGO LF38 > Almost sold in Halifax, NS. > > > > > > On Apr 30, 2015, at 11:15, Josh Muckley via CnC-List <[email protected] > <mailto:[email protected]>> wrote: > > Moving the base forward should give more aft rake and reduce weather-helm. > > Josh Muckley > S/V Sea Hawk > 1989 C&C 37+ > Solomons, MD > > On Apr 30, 2015 2:13 PM, "N7FN--- via CnC-List" <[email protected] > <mailto:[email protected]>> wrote: > > Hi, > > I need to know, from you 38LF owners, where in the mast step your mast is > positioned. > > Right now my mast is all the way aft in the step but I can see that the mast > was positioned in the step farther forward at one time. > > The only reason that it is all the way aft is because that is where the > workers in the yard put it. > > Any ideas about how the boat would sail if the mast was positioned all the > way forward as opposed to all the way aft? I have seen adjustments for > moving the mast in it's step on some sports boats.
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