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      Moderation Team Change   06/16/2017

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eclipsemullet

Laser up mast

15 posts in this topic

Has anyone heard of adjusting the rigging to get the mast straight, by using a laser pointing up the track?

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I tried it and could not see the laser on he mast. What I do is stand at the dock directly in front of the boat and align my position until the center of the base of the mast and the forestay are aligned and then take a photograph with a wide angle lens that will take in at least the center of the mast. I take several and then look at the one with the best alignment. Then I look at the position of the forestay and halfway up the mast. Assuming the forestay is straight, you have a perfect reference.

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Has anyone heard of adjusting the rigging to get the mast straight, by using a laser pointing up the track?

How would you get the sharks to stay still long enough?

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Has anyone heard of adjusting the rigging to get the mast straight, by using a laser pointing up the track?

Shine up boltrope slot. works best at dusk. Done it on smaller keelboats.

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Has anyone heard of adjusting the rigging to get the mast straight, by using a laser pointing up the track?

How would you get the sharks to stay still long enough?

Best line so far today

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I have often thought of doing this but have never tried it, because I didn't think I would be able to see the laser. As someone pointed out, you can't. Now, if it was a foogy day, then it would work... I also figured I could put the laser on some kind of pivot and move it back and forth so the spot moves up and down, but unless the pivot if perfect that won't work...

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Maybe use a laser level that would put a vertical line all the way up the mast

 

Although IMHO setting up a laser level is so much a PITA that if there's another way to line it up, I'll probably use that (based on other projects like hanging kitchen cabinets). Any minor error at the laser gets bigger the farther away you get....

 

I have often thought of doing this but have never tried it, because I didn't think I would be able to see the laser. As someone pointed out, you can't. Now, if it was a foogy day, then it would work... I also figured I could put the laser on some kind of pivot and move it back and forth so the spot moves up and down, but unless the pivot if perfect that won't work...

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Just shoot a thin messenger line up with the main halyard and pull it tight to the groove, that should get you a pretty damn straight line.

 

When the mast is straight, spend some time just sighting the groove with your eye. You should be able to get good at visually sighting the mast for straightness into the foreseeable future...

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I have often thought of doing this but have never tried it, because I didn't think I would be able to see the laser. As someone pointed out, you can't. Now, if it was a foogy day, then it would work... I also figured I could put the laser on some kind of pivot and move it back and forth so the spot moves up and down, but unless the pivot if perfect that won't work...

 

 

get a green laser...

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I have a home depot laser that I have set up on the transom and it provides a vertical line. My boat has a wooden mast and the main luff track is secured every 6" with a screw so I get good resolution lining up the screw heads.

Then I began to understand how much my mast moves and went back to using the main halyard to get it straight in the boat....

I did have fun with it on a calm evening.

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Finding the red laser dot in bright sunshine is also a problem for surveying equipment. There are some red lens glasses provided in some kits that are supposed to help by passing only a limited range of light color. That makes the dot stand out better.

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Seems like a lot of work when you really need to get out on the water with the boat loaded up, crew on the rail and then check the rig under dynamic loads. Top in the center and eyeballed straight is good enough to that point. 30-45 minutes sailing on opposite tacks in a nice breeze should wrap it up. Good excuse to go sailing too B)

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Brother Fixit is correct. Straight at the dock and straight under sail can be very different realities.

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Run the laser up the halyard. Adjust rigging until the beam hits you in the eye. Your mast is straight.

 

(do not do this)

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First off, "straight" compared to what?

 

since the mast and the keel work in tandem, ideally you would want it in a straight line from keel shoe to mast, which you can only really do with the boat on a hardstand, and then your laser isn't going to be of much use unless you drill a hole in the hull.

 

Ideally also the keel is "straight" WRT the hull (many if not most, are not) One way to check this is that the next time you are on the hard,

  1. take a METAL tape measure from the stemhead fitting, and measure equal distances from the bow to
    1. a point on the Gun'l at the leading edge of the root of the keel
    2. The leading edge of the tip of the keel
    3. the TE of the keel at the tip (you can do the root if you want as well

now take a piece of 2mm wire or spectra and fasten it to one gun'l mark,[*]run it under the hull to the other gun'l and mark that gun'l point and the where it touches the middle of the keel. [*]Repeat for each of the above points.[*]now take each of those string measurements and touch the two gun'l marks together and stretch the string paired over to see if the mid-keel mark is centered or not

 

Odds are you will find both a twist in the keel as well as a bend in the keel and its also likely to be slightly off center at the root. Why? because keels often were ordered in batches and/or ahead of time and stored on pallet separators (so a forklift can get its tangs between them to lift them) and lead slowly deforms. And fairing it straight is expensive.

 

OK so now that you know how many inches to one side or the other your keel deflects, you can use some HS geometry and figure out how many degrees to one side it is canted. You will want to cant your mast the same amount to the other side.

 

Best way to do this is to use the same gun'l marks and the main halyard and your Loos Gauge. clip your Loos Gauge into the halyard (the part you pull on with your finger. Now touch the other part of the gauge to the gun'l (making sure the lifelines and spreaders don't touch) mark and have someone take up on the halyard slowly so that you get the gauge to max deflection.

 

This is so that you have max REPEATABLE tension on the halyard. Ideally you do this on a calm day so there is no wind driven deflection of the halyard, but the REPEATABLE tension makes this somewhat less of a problem. Now move to the other side of the boat and measure there. Adjust the shrouds in such a way as to get the tip centered over the deck.

 

NOW after doing some more simple geometry where you figure out how much longer the halyard needs to be on one side vs. the other to get the degree of offset you have on your keel, you make the adustments to the tip to get it to that point.

 

Odds are your mast now has wows in it. The human eye is remarkably sensitive to being able to detect that by sighting up a straight line (the bolt-track) keep re-adjusting the mast to get it straight. Remember you will have to re-adjust the Mast tip a couple of times as you do this as well because some of your changes will move your mast.

 

 

NOW you have the mast straight WRT the keel. If you want to go and be more accurate with a laser AT THIS POINT - go-fer-it... but until you have done all of the preceding, the Laser approach is "false precision" in that you don't really know what you are aligning it as "straight" against. Aligning it as "straight" vs. your likely skewed transom or coachhouse roof is a fools errand.

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