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liveitwell 07-30-2013 01:46 AM

cutting down aluminum masts
 
Ive recently took dow some aluminum masts of an old ketch rigged boat to replace my wood ones. The main mast is three feet too tall and the spreaders too this makes it easy to figure out how much to cut off. The gooseneck can be reriveted easy. The problem I have is how to cut a straight cut around the mast. Normally for something like this I woul just measure several times from the current end around the mast and connect the dots. The current end however is on an angle. Makeing the marking of the mast very difficult. Any sugestions that arent "dont cut down the mast" would be greatly appreciated. Thanks

knuterikt 07-30-2013 02:53 AM

Re: cutting down aluminum masts
 
Quote:

Originally Posted by liveitwell (Post 1066313)
Ive recently took dow some aluminum masts of an old ketch rigged boat to replace my wood ones. The main mast is three feet too tall and the spreaders too this makes it easy to figure out how much to cut off. The gooseneck can be reriveted easy. The problem I have is how to cut a straight cut around the mast. Normally for something like this I woul just measure several times from the current end around the mast and connect the dots. The current end however is on an angle. Makeing the marking of the mast very difficult. Any sugestions that arent "dont cut down the mast" would be greatly appreciated. Thanks

If I understand you correct, you want to cut off a piece off the mast at an square angle?

If the mast profile i straight (no taper) in the section you are going to cut you can use this method.

Get hold of a piece of paper with square corners and parallel sides that is larger than the circumference of the mast.

When I made the boom for my boat I taped together two pieces of A4 printing paper (same as Legal in US ?) with overlap, short end to short end making sure the sides where parallel.

Wrap this sheet around the mast make sure the overlap is parallel and tape it onto itself.
slide the paper with one of the edges to where you want to cut and tape in place.

Cut the mast with a good hack saw.
Start with a shallow cut around the mast parallel to the paper edge, now you have a groove to cut in.

Remember to have good support under the mast section where you are cutting so you get a clean cut without breaking in the final piece.

Good luck with the new mast.

imasaluki 07-30-2013 10:50 AM

Once you cut it with a hacksaw, use a metal file to make the end completely even. Use a level to verify levelness in several directions across the end.

chucklesR 07-30-2013 10:56 AM

Re: cutting down aluminum masts
 
Get a laser marker from any DIY store, set it to the proper angle /level then use it to mark the mast properly with no guessing.

pdqaltair 07-30-2013 11:18 AM

Re: cutting down aluminum masts
 
Knutterikt was dead-on. No pipefitter would have though about it for 2 seconds, he would have simply reached for his pipe wrap.

In fitting a new mast there are numerous structural questions, and without sounding condescending, if this required pause I have to believe there are other subtleties involved. What will the new mast rest on (the old block will be wrong)? Do the spreaders need moved or changed in length? Spreader angles? Is the shroud base changed? How do the weights of boats compare? How do you intend to lift and place the mast? Are you replacing the standing rigging--I assume you must be, as the terminals are certainly different. I'm not saying you must use a rigger, but I would certainly talk to someone who understands the engineering and the practicalities. How to cut the mast is the simple part.

And I would consider what adding 3 feet to my rig would do, as an option. You've certainly saved some weight aloft, so I bet she would stand it. But I'm sure you have considered all of this; changing all of the rigging and sails is real money.

DonScribner 07-30-2013 10:09 PM

Re: cutting down aluminum masts
 
LiveIt,

Throw it on a chop saw with a carbide blade. I am a skylight designer (not rectangles). We use aluminum extrusions of the same alloy as masts. Many of the fabricating steps involve chop saws and clamps. Be sure to block it up, make it parallel with the fence and the table and be sure the saw is squared up as well. Clamp it in place. Take your time cutting through the material and don't sweat it if you're off 1/8". That's what turnbuckles are for. After cutting, clean it up with emery cloth. The burr will be on the bottom of the material. That means the inside on the top and the outside on the bottom. Most of all, don't freak out. We do this ALL THE TIME. Just be careful. Be sure to wear goggles and no gloves.

Don

rugosa 07-31-2013 12:30 AM

Re: cutting down aluminum masts
 
Measure twice, cut once :)

Griffinroydonald 07-31-2013 04:25 PM

Re: cutting down aluminum masts
 
I have cut down several and have an easy way. I use wide masking tape and run a level band around the mast. I measure to make sure it is straight. I cut with a jig saw with a fine tooth blade. The rough edge in filed down by hand and cap installed. I mark the holes and drill away. I have had good results with this and it has kept me from replacing a mast.

Tim R. 07-31-2013 04:51 PM

Re: cutting down aluminum masts
 
A manilla folder works well as it will easily wrap square around the mast and then it is very easy to run a sharpie against the edge. I used this technique when I cut down the mast on my Pearson.

liveitwell 08-02-2013 05:18 PM

Re: cutting down aluminum masts
 
You folks are quite a wealth of knowlege. Thank you. The masts are set inside stainless steel brackets The ends of the masts are capped but on an angle that had plastic wedges placed under to level it out. My masts curently are three feet shorter as are the spreaders. This makes the cutting perfect. no rigging replacement no Chain aloft to extend the forstay. Im still open to suggestions. I have three feet to play with so I can practice cut it several times. Does anyone know if there is any bad news about not haveing an end cap welded to to bottom end?


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