Saturday, June 29, 2013

Mast Steps

Years ago, while delivering s/v Tangerine from the Marquesas Islands to Vancouver, we heard a loud bang as something crashed to the deck. We were both below at the time, but instantaneously were both up in the cockpit – no backstay! Dirk dropped the head sail and while I bagged it, he dropped the main and we flaked it. From the crash on deck to the sails down, the time could have been measured in seconds. The mast held! The seas had a rolling swell, fairly short but not breaking, so the forces on the mast had not led to its failure.

A week earlier we were recovering from several days of assault by hurricane Diana, ending with our motoring through her windless eye. If we had lost the backstay then, the mast would have been gone. At that time we were at 17degrees N - 129 degrees W, about 1100 miles from the closest land and the next two tropical storms of the season tracked through that area in the following two weeks. Matsu, Goddess of the Sea, had watched over us again.

We ran a halyard to the stern to temporarily support the mast and Dirk held out two straws, I drew one, Dirk lost. With Dirk in the bosun’s chair, me on the winch hoisting, we managed a jury rigged backstay that held to Vancouver.  Even given the improved swell conditions, Dirk was in a world of hurt for several days from the beating he took against the swaying mast.

This event led me to years of debate on the merits of mast step versus the weakening of the mast structure. I am now convinced there is no detrimental structural effect if the installation is done correctly. Unfortunately, I reached that conclusion after Yachttech  in Sydney had fabricated and stepped the new mast, but I decided it was worth the effort to install them in situ (okay, that’s a construction term not a nautical term…).

The next decision was what style of step to use? A flat bar strap bent into an enclosed step profile is the most common style and if made with the right thickness of flat bar is probably the most stable. Also, your foot is restrained by the step design but the step is permanently there and notorious for fouling lines, halyards and sails. The folding steps intrigued me and I ended with the Netherland’s made Karver Mast Step made of fiberglass reinforced nylon.  They have a swl of 140 kgs, lock into the folded position so they will not rattle nor catch halyards, are noncorrosive and UV resistant. Blanchard Rigging on Hornby Island is the importer and gave a good price for quantities greater than 20 or 24.  

“So you’re gonna put some mast steps on – how many?”  These jobs are all about an endless number of small details that take time, lots of time. Tie a 100’/ 30m tape to a mast head halyard and tie a messenger line on as well. Use the messenger line to pull the halyard back down because without it the tape will break, the halyard will go to the top of the mast and you still don’t have mast steps so you will be in the bosun’s chair retrieving it! No, I did not do that, I know about Murphy so the messenger line was on from the beginning.

First locate the spreader heights and the top of mast height. Check for interference from shrouds and stays. Calculate your number of steps required by using a 400 to 450mm (16” to 18”) step height divided into the deck to first spreader increment, first spreader to second spreader and second spreader to about 900 to 1200mm (3’ to 4’) below the top of the mast where you will want a step on both sides of the mast for comfort during extended work projects. The rest of the steps are staggered on alternate sides and some may be skipped completely at mast mounted winches closer to deck level.

“Time to head up there – oh yah, what about safety?” Having come from the world of construction, I have a 5 point harness with D rings and lanyards. I also have a long length of ¾” braid and a sliding cam lock sized for the ¾”. When you see people on the sides of high rise buildings in swing stages or bosun’s chairs they are required to have a secondary restraint system. This is the same system I use. I would recommend not using a halyard for the cam lock as the jaws will chafe the halyard, use the halyard to pull up a working line.

I tend to over design things in an effort to achieve a failsafe system. It may take a little longer to install but I have never regretted the extra effort even if it was only for peace of mind, Mags’ peace of mind. The picture above shows 3 machine or tech screws holding the step and I have read recommendations for using pop rivets as mounting hardware. I have seen tech screws and pop rivets fail in construction applications and if there are 5 holes available why not use them all? They are not close enough together nor sufficient in number to structurally weaken the mast.

So the decision was: 5 - #10 – 32 (NF) 18-8 stainless steel machine screws per step. I would have used 316 stainless if it had been available but the 18-8 will do and the national fine thread engages more lineal mm/in of thread. To drill and tap 5 screws with the tolerance necessary to fit the step requires a fair attention to detail and precision. Initially I thought a template would be best but ended with just measuring the double step increments and using the step itself to pencil mark the holes. Center punch the marks to ensure the drill does not wander and I did use a small drill bit as a pilot hole to see that it was still centered before drilling the tap hole size. The tap drill often is sold in the package with the 10-32 tap and size does matter so use the correct drill. I have a T spinner handle for the tap and would recommend getting one. The mast is probably not too thick of an extrusion on the sides so you do not want to strip any threads. The right tool for turning the tap in and patience will make every hole good. When starting a tap apply even pressure turning slightly more than a quarter turn and then back spin to break the cutting free, continuing until the tap is turning freely. Aluminum galls easily so use a cutting compound, WD40 works, while cutting the thread and be patient.  When finished the 5 screw holes clean the WD40 from the mast, apply 5200 as a bedding compound to the base of the step and put the first screw in dry and not tight. The remaining screws get Lanocote, or equal dielectric grease, spread on the threads prior to placing and tightening. Remove the first screw and put Lanocote on it and tighten. Hand screw the machine screws, don’t use a drill to set them and be careful not to over tighten as you can easily strip the tapped threads. Also, if I was going to put Lanocote on the first machine screw anyway, why didn’t I do it in the beginning? Unless you are better than I am at standing on one foot, applying caulking to the step, but not too much at the screw holes, getting a screw from your pouch and screwing the step onto the mast without smearing caulking all over the tapped holes, all done while you added Lanocote to the screw, oh yah, and don’t drop anything because you are up a mast with water all around you, - the extra step of a preliminary screw wasn’t so bad! This probably explains why I have no pictures of the process.

So now that you have finished the first step while standing on the deck, I should mention the importance of putting lanyards on all tools. If you don’t, you will make some hardware store owner rich because water is a tool magnet.  I spent the better part of 3 beautiful days completing this job. Just knowing the steps are there makes me sleep easier. Not having to scramble up the lower shrouds and halyards to get to the lower spreader to spot for coral heads while entering a new anchorage made it all worthwhile. Now that vantage point can be the upper spreader with even better visibility. Although our rigging is new, shit happens and it is nice to know we have a chance to inspect and repair problems. Mast head lights, antennas, wind ‘ducers and all are accessible and the top of the mast makes a great photo location too!

To all of those who work with tools, I apologize for the minutia of details but if this description makes one person say, “I can do that” and know they did it correctly, it was worth my time. Anyway, the people who didn’t want all the detail quit reading at the top of the first page! Also, to any members of the Bluewater Sailing Assoc, Fleet of 2013, who have heard me espouse the virtues of mast steps and are thinking, “Is this the only damn job he has done on that boat?” the answer would be “No, but few other jobs have left the same satisfaction.”

1 comment:

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