BOAT wrote:
If your using a smaller sail in the same cleats your not moving the sail power at all.
All your doing in that case is reducing the overall sail power.
You are also reducing the length of the moment arm - the distance between application of force and axis of rotation (A' < A). ie. my long-handled wrench versus sort-handled wrench example.
"Give me a lever long enough and a fulcrum on which to place it, and I shall move the world. " - Archimedes
I want the opposite.
BOAT wrote:Also, in the diagram the first boat has more force pulling the stern than the second boat. The second boat has more force pulling forward than the first boat, there for the second boat in the picture would round up later than the first boat.
That is what I want, so that corroborates my finding.
With stock sails both the and will overpower in high wind due to lousy sails, after which your efforts to trim and balance are the fruitless applications of lipstick on the s(c) ow.
Reefer is your only weapon then. Reefing will help too.
Catigale wrote:With stock sails both the and will overpower in high wind due to lousy sails, after which your efforts to trim and balance are the fruitless applications of lipstick on the s(c) ow.
Reefer is your only weapon then. Reefing will help too.
BOAT seems pretty certain that, with headsail only, a Mac should not round up.
Someone on my physics forum pointed out something that I should have realized.
Macs are susceptible to loss of rudder control just as other boats are. True, Macs' dual rudders mean that one will always be dug into the water, but the fact is, with increased heel, the turning moment is increasingly converted to a lifting moment. The turned rudder is increasingly acting to lift the stern, while decreasingly acting to turn it.
Yaw is supplanted by pitch.
That is not specific to this case, just an interesting fact to consider.
Another interesting and partly relevant point is related to the daggerboard/centerboard in the diagram above.
It's shown as if it's centre is the rotation or balance point of the boat.
With the M, the daggerboard is forward of the balance point. So, as it's deployed, it's effort is having the effect of increasing the weather helm.
With the X boat, the position of the board is also movable fore and aft (in addition to up and down), in fact it's a combined movement - i.e. The more it's dropped, the further forward it moves. Since we know that the design of the centerboard system is such that it's deployed fully when close-hauled, it follows that it is also located forward of the balance point. Indeed the more it is deployed, it's centre of effort is further forward of the balance point plus it's actual power/effort is increased (in much the same way we saw with the Genoa).
Just mentioning this as, whilst tinkering with my daggerboard on various points of sail, I noticed that changes to amount of DB make a big change to the balance.
BOAT, you mention that balance really isn't a problem on your boat BUT I'm guessing that that's a function of your innate sailing abilities, i.e. You are almost unconsciously trimming the boat's balance all the time - no wonder BOAT is always well balanced.
DaveC426913 wrote:Someone on my physics forum pointed out something that I should have realized.
Macs are susceptible to loss of rudder control just as other boats are. True, Macs' dual rudders mean that one will always be dug into the water, but the fact is, with increased heel, the turning moment is increasingly converted to a lifting moment. The turned rudder is increasingly acting to lift the stern, while decreasingly acting to turn it.
Yaw is supplanted by pitch.
That is not specific to this case, just an interesting fact to consider.
And the lift from the sail is farther and farther outboard of the hull and rudder as the boat heels, causing increasing moment about it's center of drag the farther the boat heels. There's a lot going on there.
It's hard to use me as a good comparison for other boats because I do not sail in high winds as much as a lot of you folks on the East Coast so really, we need the guys in M boats that sail in the really treacherous winds of the Great North to chime in here.
Highlander and Beene and YukonBob (I think he sails the M too) and other guys in the crazy Great White North can tell us if they ever round up. Mastreb sailed a M boat down here and I met him many times and the only "roundup" he ever mentioned was for killing weeds.
I did get a visit this summer from Jimmy Alonso from this site and he is an M driver out of Puerto Rico and he is on the East side of the island and his sailing grounds are on the west side so he is sailing in really crazy winds if he is skirting the southern shore of Puerto Rico (remember the hurricanes in Haiti?) I never heard him mention the word "roundup" once.
There are also guys in X boats in the wild winds like Wind Chime - I don't recall him ever complaining about a round up.
I guess I need to get on a X boat and sail one - I want to find out what everyone is talking about.
MikeFloutier wrote:With the X boat, the position of the board is also movable fore and aft (in addition to up and down), in fact it's a combined movement - i.e. The more it's dropped, the further forward it moves
CB is always 100% deployed on SeaSaw.
I'm not yet convinced that tweaking the CB is useful.
BOAT wrote:The fact that the X has a back-stay has always puzzled me - why would a boat with the same sail-plan need a back-stay?
The is not the different one, everything that came before the had a backstay. The M is the different one and was designed to not need a backstay so it could use the swivel mast. The difference is in the placement of the side stays. Previous discussions on this with the drawings are in the archives.
Well, then i guess the back stay will not help answer any issues regarding "rounding up" so what else?? The placement of the main sheet? Could that be it? Is it too far aft?
Perhaps the standard rig / design / set up, is adequate for 93.7% of 'normal' sailing. Once one gets to pointing high in really stiff winds to experince rounding up, they've reached the zone that is outside of the normal performance of what the boat was designed for. Adjusting this, moving that, may help a bit, but it doesnt mean anything is wrong with the boat / rig.
K9Kampers wrote:Perhaps the standard rig / design / set up, is adequate for 93.7% of 'normal' sailing. Once one gets to pointing high in really stiff winds to experince rounding up, they've reached the zone that is outside of the normal performance of what the boat was designed for. Adjusting this, moving that, may help a bit, but it doesnt mean anything is wrong with the boat / rig.
I'm not saying the boat is wrong or anything but I just can't figure out why the boats would not act the same when they are supposed to be almost identical - I guess I'm just trying to figure out what it is that makes the issue happen.
What are the differences between the two boats? They weight the same, right? Same hull pretty much? Same sails - I don't think the rudders are different are they? Could it be the rudders?
BOAT wrote:
What are the differences between the two boats? They weight the same, right? Same hull pretty much? Same sails - I don't think the rudders are different are they? Could it be the rudders?
The M has an additional 300 lbs of permanent ballast over the X. The two hull shapes below the water line are different. Daggerboard vs swingkeel. Swivel mast vs fixed. Mast stay placement. Most M's are blue hulls...that could be it... the slower blue hull!
Maybe thats Roger's intent, to de-tune the M so that it doesn't push the envelope the way the X does!
and 
will overpower in high wind due to lousy sails, after which your efforts to trim and balance are the fruitless applications of lipstick on the s(c) ow. 
