Mast Angle, 26M?

[Jim Cate]

Hi,

As a new 26M owner, I am occasionally having difficulty bringing the boat through a tack. - The boat seems not to have the momentum to carry it through from one tack to the other, at least in comparison with what that I usually experience on other boats. I'm aware that I shouldn't leave the ruddfers hard over during the tack (since they can act as a brake), and I'm aware that the jib shouldn't be pulled to the other side until it is pulled over by the wind, and I do keep the dagger board down or almost 100% down when going upwind. In addition to these adjustements, I have seen suggestions that if the mast is brought forward a few degrees it will improve pointing and tacking performance. - I need some advice on how to determine if the mast should be moved forward, and how to determine if it's in the right position.

Specifically, how do you measure the angle or position of the mast, and what position is recommended? For example, must the position of the mast be measured with the boat in the water, under normal load? Do you measure the position by using a carpenter's level against the mast and figuring out the deviation from verticle as you wold a post, etc.? Also, is the position actually significant for tacking, etc., and if so, please suggest some acceptable range of positions.

Thanks,
Jim

[Jim Cate]

I see from some of the other notes that a rake of around 3-4 degrees seems to be suggested. (Excuse the dumb question, but does this mean that the mast is raked rearwardly from vertical, when the boat is sitting in the water with normal load?) - Does the 3-4 degree position apply to the 26M? Also, since the Mac 26M doesn't have a backstay, are there special considerations I should be aware of in making the adjustments?

Thanks,
Jim

[Frank C]

The Mac 26X mast rake is 86 degrees from the factory, i.e. with the mast tip aft by 4 degrees. Most who have adjusted the mast rake correct it to about 2 degrees of aft rake, reducing the boat's tendency for weather helm.

My boat & motor floats true to the bootstripe when loaded for weekending. So, I just leveled it on the trailer for calculating the rake. Because I just happened to have a digital carpenter's level, it was particularly easy to level the boat and measure the mast. Otherwise, you can weight the main halyard, measure its distance aft of the mast, and do the trig.

Since the 26M has a rotating mast - sorry, all bets are off.

[craiglaforce]

Its all about helm balance. If the steering is light and under control even in windy conditions, then you should be good. If weather helm is trying to pull your arm off, then you've got too much rake. You want just a touch of weather helm.

Are your sails trimmed well for an upwind course and do you have good boat speed before the tack? Is the jib working efficiently before the tack? If so, it should tack quite easily. The only time I've missed a tack was when sailing under partially rolled up working jib and no mainsail in pretty high winds. Reduced boat speed, lee helm and windage all contributed to the missed tack.


Things to check are a fairly flat mainsail shape (tight outhaul, full hoist).
You might also want more weight moved forward (maybe move the water tank and tool box forward a bit). Are the rudders all the way down tight?

[Dimitri-2000X-Tampa]

Is reducing mast rake and weather helm going to make a boat tack easier? I think probably not seeing as you are moving the center of pressure further forward. You need to move the center of lateral resistance (CB) further forward for easier tacks. Theoretically, the boat will tack easier with the COP moved further back or basically adding more rake...not that I would recommend this as there is already too much. When you feel this rake is in higher winds (ie. > 12-15).

Anyway, with a 26X, it is very important to have the CB all the way down to accomplish tacks properly in light to moderate wind. But since this is a 26M, that doesn't really apply. A couple more suggestions though: As someone mentioned, make sure both rudders are down...I've also gotten the boat out of irons by putting the motor down as a third rudder. Not sure how it is on your M, but in certain positions, my swim ladder hits the motor when you are putting the helm hard over to port. This restricts the movements of the rudders in that direction and may not give you the necessary rudder deflection to come through the wind. I have to adjust my ladder (in the up position) differently when the motor is up versus down in order to have full rudder deflection...and this could possibly be a problem for you perhaps.

[RandyMoon]

I am bringing this old post back to life. There are lots of threads about the X mast needing a rake of 4 degrees. Now that the M has been around for a few years, does anyone have thoughts on what the rake angle should be for a M? The manual does not get clear on this measure.

[Jim Cate]

[quote="Jim Cate"]Hi,



Specifically, how do you measure the angle or position of the mast, and what position is recommended?

----------------------------------------------------------------------------------

Since posting the original note shortly after getting my 26M, I have reduced the mast rake somewhat, and adjusted the tension on the stays, and the boat does indeed point higher and tack more consistently. Thanks for all the suggestions.

I would still like to get instructions in response to the above question as to how to determine what the rake is. - Assuming that the boat is at the dock and is loaded and manned as it will be during the voyage, what's the best way to measure the rake without buying a laser level computation instrument? Specifically, when observing the distance of offset between the lower free end of the halyard (weighted, and hanging down about 29 feet) and the mast, what's the relationship between inches of offset and degrees? (There must be a formula for this, but my trig and physics books aren't easy to dig out.) Or alternatively, what offset, measured in inches, are you using on your M?

Thanks,
Jim

[Catigale]

Jim - since the angle is small, you can approximate the offset in units of length to be equal to the angle in radians...or mathematically

Offset in inches
sin (Angle) = _______________

29 feet * 12 inches/foot

On edit - the post engine butchered my formula above, not quite sure how to fix....


BUt the angle has to be in radians, not degrees

There are about 57.3 degrees in one radian in the Northern Hemisphere, so

3.00 degrees /57.3(degree/radian) equals 0.0524 Radians

ANd your offset of your hanging wrench will be

29 feet * 12 inches * 0.0524 or 18 inches from base of mast

That seems large - did I screw up??

[JJ]

I got the same result using degrees instead of radians:

Let the angle from the vertical to the angle of the mast= 3 degrees
Mast height=29'
Let x = horizontal distance
therefore, sin 3= x/29
or x= 29*sin 3
x= 1.52 ft or 18"

So, if you drop a plumb line from the top of the mast to the deck you should see 18". Can anyone crawl up there to do that???


Mod's edit: JJ, an original poster always has ability to edit any of your own posts.
I've made your correction here, but look for an "edit button" at upper right of every post you've made - fc

[Dimitri-2000X-Tampa]

If you check out my mast rebuild thread, you'll see that I just raised my forestay by 4 inches. Before I put any tension on the shrouds, the pendant was about 4-6 inches away from the mast. By your calculations, that would be about 1 degree of rake. When you put some bend into the mast by tightening the uppers, that pendant goes back another 4-6 inches or so. I don't know how much applies to a 26M but even in this new configuration on my 26X, I still have plenty of weather helm. I can't be positive, but I have a feeling that before I made this mod, my hanging pendant would float probably 18-24 inches behind the mast or perhaps 3-4 degrees.

[delevi]

Here is my simple, unscientific answer. I believe the boat comes stock with too much mast rake, which makes it more prone to weather helm. Simply adjust your forestay turnbuckle, cranking it down to the maximum, thus making the forestay as short as the turnbuckle will allow. This will produce minimum rake, reduce weather helm, and in my expereirence, improve performance and handling significantly. This may or may not solve your tacking problem, but I haven't experienced this. The Mac is a unique animal and takes some getting used to. With some experiecne, however, you will tack just fine. If you do adjust the turnbuckle, keep in mind that the top forestay attachment doesn't have a swage, thus doesn't rotate. This measns you will need to secure the metal fitting just above the turnbuckle with vice grips and hold it in place firmly as you crank the turbuckle with your other hand (use a screwdriver for leverage.) I learned this the hard way by not doing this and untwisitng the wires of the forestay and having to replace it. If you make this adjustment, keep in midn that the forestay will become more difficult to pin while regging and you may have to make adjustments to your shrouds to compensate. Good luck.

Leon

[David Mellon]

I tried to perform the hanging wench step, but she just said no. Trying a trollop next.

[LOUIS B HOLUB]

Hi Jim,
I sent you a PM concerning Legend Point Marina. (Im not sure if you received it). I and the 3 other Mac owners like the facilities so far. Hope youall decided to move in too.

Best Regards, Louis, and
The Holub Boat