Mast not plumb

[David_cepi]

Hi guys:

I am asking for thoughts about a mast installed with a 10mm out of plumb towards starboard at the keel step when measured with a spirit level. The boat is a 33' with a 13m mast. In other words, the collar and the step at the keel are off by 10mm so I guess the mast has a lean as it goes higher.

Would like to know if they would be any significant issues when cruising. Would the sailing performance be compromise?. Just checking if I it's serious issue or it's just me being perfectionist.


Thanks guys.

 

[PlankWalker]

Why don't you correct it, if its out. Though spirit levels are not verry accurate on a floating boat.
Slacken off one side and tighten the other, counting the turns as you go.
you'l need about one and a half inch to 2 inch aft mast rake on 33 footer

 

[David_cepi]

Why don't you correct it, if its out. Though spirit levels are not verry accurate on a floating boat.
Slacken off one side and tighten the other, counting the turns as you go.
you'l need about one and a half inch to 2 inch aft mast rake on 33 footer

That would be ideal if the mast wasn't in now. Once I get to my destination I am thinking of hiring a crane slack of everything and rescue back the step 10mm to Port. I just was asking if I should even be bother for a cruising boat. Its not the rake which worries me as much as a port/starboard of set.

 

[jac]

That would be ideal if the mast wasn't in now. Once I get to my destination I am thinking of hiring a crane slack of everything and rescue back the step 10mm to Port. I just was asking if I should even be bother for a cruising boat. Its not the rake which worries me as much as a port/starboard of set.

I'm confused

Are you saying that the mast foot is 10mm too far to starboard ??

Generally the foot is pretty much in a fixed position port / starboard and you adjust the mast by tightening / loosening the shrouds to pull the top of the mast one way or the other? If the mast foot is stepped in physically the wrong position i would be more worried about what else the builders / yard had got wrong

 

[David_cepi]

I'm confused

Are you saying that the mast foot is 10mm too far to starboard ??

Generally the foot is pretty much in a fixed position port / starboard and you adjust the mast by tightening / loosening the shrouds to pull the top of the mast one way or the other? If the mast foot is stepped in physically the wrong position i would be more worried about what else the builders / yard had got wrong

Yes, the foot where the mast stepped had to be replaced and is off by 10mm.

 

[Praxinoscope]

I’m impressed if you managed to achieve any sensible information using a spirit level on a boat

 

[penfold]

A spirit level is about as much use on a boat as an umbrella or a naval officer; check the plumbness of your mast using a halliard, or if you have stretchy braid halliards a length of thin dyneema cord, or measuring directly at the mast foot with a caliper or rule from known datums. Your mast foot must be very unusual, there is usually no means of stepping a mast off the centre line laterally, although fore and aft adjustment may be done on more sporty numbers.

 

[Concerto]

Have you checked whether the masthead is off centre? On a day with negligible wind, take the main halyard and get it to just brush the deck under tension on the deck by the port cap shroud. With the halyard fixed, check if it touches the deck on the other side. If it does then it is upright to the boat, if not the adjust the cap shrouds to make them the same length. This is far more accurate than a spirit level. Do not forget to adjust the lower shrouds. With a keel stepped mast the exact position of the mast foot is not as critical as you think as you will have space as it passes throught the deck, so where the top of the mast is is far more critical.

Setting up your masthead standing rigging

There are plenty of other web sites for "How to set up a masthead rigged mast" that Google will pull up from the likes of Selden, North Sails, PBO.

 

[David_cepi]

Thanks Concreto. I just had to cut the floor as it was sinking. I replaced it with a new reinforced fibreglass sheet and screwed the timber step ontop of it. I tried very hard to try my best to get the timber step plumb with the deck collar, I didn't have any old marks/references.
The rigger says that I won't appreciate the difference in sailing performance but I question everything.

Before trying to modify things I try to ask before I modify things aiming for perfection and making it worse (which I usually do).

I'll measure how you showed me. Thanks.

 

[Neeves]

Again

It might help if you provided some pictures, of the mast base, and define the yacht. The mast is commonly located at a bulkhead - a tape from fixed points to either side, chain plates ?, showing the differences in dimension would also help.

Jonathan

I don't quite see how the base can be 10mm out but the original shrouds and stays still fit - unless you have a strange bend in the mast. The forestay should be straight - I'd have a look from a distance bow on and check how the turnbuckles fit as they should fit similarly.

 

[David_cepi]

Hi Jonathan:

I'll have a look when I am back at the boat. I'll take more pics but now I only have this one on the phone.

 

[Neeves]

Hi Jonathan:

I'll have a look when I am back at the boat. I'll take more pics but now I only have this one on the phone.

David,

Bad timing - I was in Hobart last week, depends where you are - but I could have come and had a look. Too late now - pictures will help.

Jonathan

 

[john_morris_uk]

Aiming for perfection is admirable, but the rigger/sailmaker is right. You won’t notice the difference.

In addition, most every boat is not quite symmetrical. (Hulls distort, rigging stretches, builders get careless over placement of bits. ) I think every boat I’ve ever sailed seemed to go better on one tack than the other. No excuse to being careless in fittings, but 10mm on the mast foot REALLY doesn’t matter and you won’t notice.

Anyway if it’s keel stepped you could correct it a bit with the mast partners at the deck. Then use your cap shrouds and lowers to get the mast straight and central. (Use a dyneema string as described above)

Like others, I’m unconvinced by your use of a spirit level. A spirit level only works really accurately when the boat is truly levelled up in a cradle ashore using known reference points to get the boat sitting on her lines. When I was doing a major refit in our boat earlier this year I had to go through this exact process. Levelled up in the cradle using known reference points.

 

[Black Sheep]

I suspect a lot of the replies don't appreciate that your mast is keel-stepped rather than deck-stepped.
If you're happy that your step is solid, then I wouldn't move it!
I take it that you've checked there's no space at the collar to correct things there?
But really, I would trust your rigger on this. Masts are never vertical when sailing anyway - all you've got is a very slight bias on one side. It doesn't sound significant enough to cause any great discrepancy in shroud stresses.
If there were a difference in sailing performance, it would be that one tack orthe other would be slightly better when close to the wind. But I don't think you'll notice the difference

 

[howardclark]

I’ve got two ‘off centre’ effects on the boat- the wooden mast is not quite straight and we are trimmed to one side because heavy things like batteries, spare bottled water, coal burner and food ( it is impossible to comprehend just how much food my wife can justify loading, but that’s a separate thread) are all to starboard.
it really makes sod all difference to how she sails! You may be fractionally less efficient on one tack but then you will be better on the other!

 

[neilf39]

If the mast foot is off centre there is a chance the boat hull is not perfectly symmetrical. 10mm at the foot is neither here nor there. So long as the mast is straight and dead upright athwartships it won't matter.

 

[Black Sheep]

So long as the mast is straight and dead upright athwartships it won't matter.

I beg to differ. There is no need for the mast to be dead upright athwartships. The deflections he's talking about (10mm at foot) would translate to between 50mm and 70mm at the cap (depending whether the mast length is overall, or above partners, and guessing at 2m below partners). That won't make any noticeable difference.

 

[neilf39]

Why? The mast will just be 10mm to one side all the way up if it is vertical. If the mast is just off centre in comparison to the shrouds at the foot the difference in tension to keep it upright will be negligible. I think I would like my mast to be upright across the beam which is what athwartships is. Are we talking at cross purposes?

I beg to differ. There is no need for the mast to be dead upright athwartships. The deflections he's talking about (10mm at foot) would translate to between 50mm and 70mm at the cap (depending whether the mast length is overall, or above partners, and guessing at 2m below partners). That won't make any noticeable difference.

 

[Birdseye]

Sail it and see if there is a perceptable or measurable difference hard on the wind on both tacks. Likely there will be a small difference but then there often is as few older boats are symetrical. For that matter, I sailed a modern Westerly which had its forestay by design off centre on the bow!

 

[Black Sheep]

Why? The mast will just be 10mm to one side all the way up if it is vertical. If the mast is just off centre in comparison to the shrouds at the foot the difference in tension to keep it upright will be negligible. I think I would like my mast to be upright across the beam which is what athwartships is. Are we talking at cross purposes?

Yes, we're talking at cross purposes. The OP's mast is keel stepped. As the mast step is not vertically below the collar/partners/hole in the deck, then it won't be vertical, no matter what you do with the shrouds. But it really doesn't matter. A mast doesn't have to be dead vertical to work - I very much doubt that there will be any noticeable difference in sailing.