SJ23 Tech Tip F18, (Updated 2015-09-19, Bob Schimmel)

Step the Mast With an A-Frame.
poles, foot hinge, apex hinge, bridles, mast stepping procedure, hinge pin.

Stepping a heavy mast on a sail boat can be an awkward job.  An SJ23 mast weighs about 150 pounds, plus whatever wind force there is.  It can also be expensive to replace a dropped mast, not to mention paying for what it hit!   For these reasons it is important to control the mast when stepping it. 

In a trucker's world an A-frame secured to the back of a flat deck is usually called a "gin pole" and is used to easily lift a heavy object on or off the deck or maneuver it across the ground.  Similarly, an A-frame is mounted on the end of a work barge is a very robust yet simple crane.  You don't see an A-frame much anymore because it is quicker to rotate a hydraulic knuckle crane than rotate the whole barge.  An A-frame can also be considered as a convenient way of lifting & moving a heavy object through a short distance. 

As late as the mid 1900s sail driven canal boats in the Netherlands were equipped with an A-frame as a permanent deck fixture to lower the mast so the boat could slide under an unmanned bridge.  The boat's momentum carried it past the bridge and the mast was raised on the other side to resume sailing.  This procedure had to operate very smooth and quick so the vessel would not loose way or block the canal to other commercial traffic.  It was considered a major blunder if you screwed up the procedure.  In the trailerable sailboat world, an A-frame comes into its own for stepping a mast.  The advantage of using an A-frame is that you have lots of mechanical advantage to reduce the lifting effort.  The longer or taller the A-frame is relative to the mast length, the greater the mechanical advantage.  The huge control that you have leads to the single biggest advantage, safety; in large part because you don't have to stand under the unsupported mast!  If you step the mast hand over hand, with the aid of a block and tackle connected to the forestay, then you must also steady the mast sideways so you don't twist the deck plate off.  The most difficult part of stepping a mast is the transition from standing in the cockpit to standing on the cabin roof.  It is during this CRITICAL TRANSITION that the deck plate is usually twisted loose or when you increase your odds of dropping the mast.   I have stepped the mast in a side breeze using my A frame, there is that much control, but I don't recommend it.  If the wind is strong, it is much safer to point the hull into the wind and step the mast quickly during a lull.  I have done this a few times with no problem.  The less time the mast is in the unsupported transition zone the better.  If the wind is really strong, wait it out in a coffee shop or install some temporary shrouds.  

A-FRAME CONSTRUCTION - Fabricate your A-frame in the sequence that the components are described here to minimize your chances of making an error relative to the effort required to make each component;

  1. Cut the poles to length, about 101".
  2. Attach the foot hinge plate to each pole, bolt to the T extrusion, screw the T extrusion to on it's mating foot pad aligned to the toe rail.
  3. Cross the poles to form the apex and drill a common hole through both poles using a single long bit to make the hinge. 

By following these steps you eliminate complex measuring that will likely be off by several degrees making for a misaligned hinge that will bind or can't pivot.  The chances of you measuring it correct are minimal!  Remember, Murphy! 

1 - Poles - The aluminum poles of my A-frame are 2" OD with 1/4" thick wall.  This thickness is overkill to the Nth degree but the price was right; 1/8" thick wall is sufficient, similar to a spinnaker pole.  See COMMENT below.  Each pole measures 101" long.  The distance from the pivot bolt at the foot to the hinge bolt at the apex is 99" with 1" of pole beyond the apex hinge.  The apex fits just short of the forestay fitting, leaving room to easily transfer the forestay from the A-frame to the deck fitting.  It is prudent to attach the forestay to the fitting quickly to secure the mast and protect the safety of the people standing within the drop zone.  It is also convenient to leave the A-frame on deck for trailering or winter storage, as seen in these two  photos.

COMMENT:  When I designed this A frame I had no idea how much force I could be dealing with so I erred on the side of safety by using heavy material.  After using this A-frame on other boats as long as 30', I realize I overbuilt the assembly.  I now know that lighter poles are quite OK since the load is all compression.  In fact I have seen poles made from 3/4" conduit (1" would be better as they are less apt to buckle or collapse under the load).  I have also seen poles made from 1.5" spruce tree trunks, gnarled up 2" poplar trees and fir (2x4)"s.   If you intend to use wood then choose clear straight grain poles.  It would be relatively simple to cut a notch in the end of the wood pole to insert the hinge plate and slip a metal collar or hose clamp over the pole end to reinforce it.  Saturate the pole ends with epoxy for strength and coat the wood with Cetol Marine to protect it from the elements.  Another method is to slip 6" long 1/8" thick metal tubing over the pole end.  Flatten the protruding tube end and bend it to align with the T extrusion to form the foot hinge.  Light gauge aluminum poles would make it easier to carry the assembly.   Be your own judge in this design.  I have this habit of building everything to withstand "WWIII".  I hate flimsy Mickey Mouse stuff.  No offence Walt!

If you want to fabricate an A-frame for a larger sailboat, scale the dimensions up proportionally.  The length of the A-frame poles should be from the mast step to the forestay fitting.  The pole diameter and wall thickness should be equivalent (or bigger) to a spinnaker pole designed for your boat.  If the assembly is too long then consider two shorter poles joined with a sleeve.  This would allow you to store the A-frame in a small space.  This is a great way to go if you are a globe trotting sailor who wishes to be independent of shore services.   TOP

2 - Foot Hinge & Deck Pads - There are two ways you can fabricate a hinge; make it fully articulating so the poles always align to the deck or make a simple hinge, aligned to the plane the poles pivot on.  I built the latter design because I had the material and was in a bit of a hurry to launch. 
The top half of the hinge consists of a 1/4" thick aluminum plate fitted inside the bottom of a pole and fastened with a 3/8" bolt with two centering spacers.  The spacers are short sections of tube cut from an aluminum ski pole.  Click here for a cross profile of the hinge assembly. Notice the two notches cut into the pole to fit the plate into.  The spacers and notches hold the plate firmly down the center line of the tube.  The plate is bent 250 to align it with the aluminum T-extrusion (bottom half of hinge) on the deck pad.  The T-extrusions must lie parallel to the center line of the hull or the turning axis of the hinge so the frame can pivot. 
At the hinge location draw an imaginary line across the deck and another one over the hinge fore & aft parallel to the center line.  This is your pivot point and axis of rotation.  The curvature of the deck can fool you when taking measurements.  Be careful. (If you use a full articulating ball joint here, all of this critical alignment can be dispensed with as the hinge would pivot freely regardless of the angle of the poles.  Aviation type ball joints are not cheap but they work very well.  The aircraft industry uses them extensively for perfect alignment of control arms).  The hole in the plate is drilled slightly forward of center so the A-frame can lay flat on the fore deck.  The two deck pads are made of (2x8)" soft spruce to protect the gel-coat and are coated with tung oil to prevent rot.  The 3" long aluminum T-extrusions are screwed to the center of each pad.  Thus the hinge operates freely through the full 1350 arc that the frame must operate through.  With the deck pad wedged against the toe rail and the stanchion, the pad doesn't move.  All of this may sound complicated, as it takes a bit of finagling to bend the plate just right, but both hinges must turn freely.  Take your time with this part of the job.  Patience has its rewards!  TOP

3 - Apex Hinge - The simplest way to create a strong hinge at the apex is to overlap the ends of the poles.  I was well on the way to making a fancy hinge when common sense prevailed!   The cross lap joint may look unsophisticated but it works, is easier to make and stores well. 
I suggest assembling the foot hinges first, place the assembly on the deck, bolt the poles to the foot hinges, cross lap the poles to form the A-frame, lock them together and drill a pilot hole through the middle of both poles.  Be very careful in drilling the pilot holes as alignment of the moving parts is critical.  If you are off by a little bit, the hinge will bind.  Enlarge the holes to 1/2."  Insert a 1/2" hinge bolt using a large nut as a spacer between the poles to create room for the eye bolt nuts.  The two eye bolts (use cast type for strength) are through bolted just below the apex hinge bolt.  Finally, test your frame by swinging it through the full 1350 arc of travel. 
The forestay attaches to the aft facing eye bolt and the 4x1 block and tackle attaches to the forward eye bolt.  At right you see the apex of the A-frame hanging below the mast with the block and tackle in place.  I tow my boat regularly with the A-frame hanging just below the mast, unless somebody has borrowed my A-frame!  TOP

RIGGING - If you use a 4x1 block and tackle you will require 80' of 3/8" line.  This length creates a long tail section which allows the tailing person to stand well out of the mast's drop zone.  Some people are squeamish about a stick falling on them!  Jam tarts!

ASSEMBLY - Having assembled the frame on deck, mark the starboard and port poles with a felt pen for easy reference when placing it on the deck the next time.  It may not be obvious now but you'll thank me for this tid bit of advice later!  






ELIMINATE SIDE SWING of MAST - I usually have a buddy to handle the hoist line of the A-frame while I control the side swing of the mast.  This has worked for many years and I thought it was good enough.  But I always knew there was a way to eliminate the side swing in a cross wind by tying temporary shrouds to the mast.  It seems I always have gusty winds when I do this job!  What follows was an experiment during my 2014 haul out.  It turned out successful. 

The problem of tying temporary shrouds to the SJ23 is that the deck elevation is below the mast pivot point.  If you attach the temporary shrouds to the toe rails they will go slack as the mast is lowered, rendering them useless.  Therefore, you have to artificially raise the deck height up to the height of the mast base by installing port and starboard bridles.  The steel ring at the middle of the bridle becomes the pivot point for the temporary shrouds so they stay tensioned as the mast is stepped.  With the A-frame supporting the weight and the temporary shrouds controlling side swing you have total control of the mast.  In addition, you can handle the hoist line from the safety of the fore deck.   This may sound complicated but it isn't.

I made each bridle from low stretch 1/4" line, 1 welded ring, 2 small carabineers and an old stretched 3/8" line for a temporary shroud.  The bottoms of each bridle are clipped to their toe rail with carabineers.  See left photo showing port bridle clipped to the toe rail with the temporary shroud tensioned. 

The upper end of each temporary shroud was tied (bowline) around the mast and the two loops were clipped to the spinnaker halyard, hoisted to the spreaders.  See right photo above.  The bottom of each temporary shroud was pulled through its bridle ring and tensioned by tying a trucker's rolling hitch.  This was the easiest way to create equal line length.  The halyard line was then tightened to take up the slack.  Afterwards we stepped the mast using the steps listed below.  I was pleasantly surprised at how well this technique worked as we laid the mast directly into the yoke that supports the mast on the transom.  Talk about cool.  In 2015 I took this procedure to the final step and lowered the mast on my own with complete control.  Keep in mind that this is possible because I don't have roller furling hardware to contend with.  Unfortunately I can't give you line lengths for the bridles because the toe rail holes are in different places for each boat.  There is enough information here for you to position the rings to your own boat, knowing that the system will work!

  • IMPORTANT 1 - Once the mast is down, don't release the temporary shrouds.  It is impossible to set the length of these lines with a mast lying on the deck and you will need them for the next time the mast goes up.  When you have figured out what length works, it's OK to make two permanent lines of equal length with eyes spliced in the ends.  You can make them from whatever line you have but I prefer low stretch yacht braid because it doesn't mar the mast. 

  • IMPORTANT 2 - Once the mast up, the shrouds are quite easy to pull down with a boat hook.  Just don't hoist them beyond the reach of your boat hook! 

Here is a variation of this technique using a sliding spinnaker ring on a track.

MAST STEPPING PROCEDURE using an A-FRAME (no roller furling) - Inspect the standing rigging where it attaches to the mast.  All cotter pin ends must be rolled over leaving nothing sticking out and show no sign of fatigue.  All nuts must be screwed tight to full depth.  There must be no "meat hooks" (broken strands) sticking out of the wire and no kinks in the wire.  The continual changing tension of the wire (pumping), between strained and released, will eventually fatigue and break it at the kink.  This is the same process as flexing a piece of metal back and forth in your hands to break it.  While this A-frame makes it is possible to step the mast by yourself, the job is easier with two people. 

  1. If you step the mast on land, keep the trailer securely hitched to the tow vehicle or block the rear end of the trailer so it can't rock.  Also, ensure you are on the shore side of any overhead electrical power lines or other overhead obstructions.  (An alternative is to float the boat in calm water, hopefully pointed into the wind to eliminate side swing of the mast.  I tried this once, but will do it again only if I'm forced to and have temporary shrouds to eliminate side swing.  The boat rocks too much when walking on the deck and the risk of twisting the deck plate loose is too great).
  2. Attach the Windex and VHF antenna while you can still reach the mast head from the aft of the cockpit.
  3. Lay the A-frame on the fore deck with the apex at the bow and the deck pads wedged against the forward side of each mid stanchion.  Secure each deck pad with a short line tied around the stanchion to prevent movement.  In practice mine have never moved but the extra bit of security is worth it.
  4. Attach the temporary shrouds to control side swing of the mast.  Bridles clipped to each toe rail, temp shrouds tied to bridles, top of temp shrouds tied around mast and hoisted to spreaders to take up the slack.
  5. It is assumed the standing rigging is correctly attached to the chain plates and the shrouds were never removed from the previous take down.
  6. Extend (loosen) the shroud turnbuckles 3/8" from the tuned sailing position by turning the barrel and holding the wire from turning.  This prevents the standing rigging from binding and puling the chain plates up as the mast is raised.  (Ensure there is at least 1/2" of thread screwed in). 
    - Tape the two shroud
    turnbuckle toggles on each side together in the upright position.  (This is important as it prevents them from flopping over, binding and breaking as the mast goes upright). 
    - Tape the back stay turnbuckle toggle in the upright position to prevent it from binding.
    - Now all turnbuckles can pivot safely on their T-bolts without binding.

  7. Close the companionway sliding hatch. (Avoid stepping on it).  Stand on the cockpit seats, one foot on each, and carry the mast aft until the mast foot rests on the deck hinge plate.  Rest the mast in the yoke of the transom support post.  While holding down the foot of the mast, insert the hinge pin and locking split rings in BOTH sides of the mast hinge pin.
    NOTE: The condition of the screws that hold the foot casting to the bottom of the mast extrusion MUST be very secure as the foot undergoes a tremendous amount of torque loading when the mast is stepped.  If the rivets are worn loose, replace them with 1/4" NF stainless steel screws.  Drill out the rivet holes and tap a thread through the foot casting.  Snug up the screws and secure them with marine sealant to prevent movement and corrosion.
  8. Tip the A-frame up to vertical and attach the forestay to the apex (top) eye bolt (aft) and secure the jib halyards (2 wraps) around the apex of the A-frame.  You should use your lines equally (jib1, jib2, forestay) to pull the mast up.  This adds extra security in case one breaks. 
    HINT - When you go forward in step 10 to transfer the forestay from the A-frame to the stem fitting, the forestay will be conveniently at hand.  If you shorten the halyards about a foot less than the forestay you can hold the A-frame down with your body weight to keep the mast standing.
    Then attach the top end of the block and tackle to the forward apex eye bolt and the bottom end to the forestay fitting.  (DO NOT attach to the rams horns as the blocks may slip off or the horns may NOT be strong enough)
    Take up the slack line of the block and tackle and wind the free end around a winch or to a cleat to secure the line. 
    Tie all other loose mast lines to the butt of the mast to eliminate clutter. 
    Take a last look around the deck to ensure all rigging is loose and turnbuckles are free to stand up.
  9. Lift the mast the first 3' by hand.  Stand under it in the cockpit, one foot on each seat, then pull the free end of the block and tackle to raise the mast to vertical.  Watch for jammed turnbuckles, snagged lines, etc as you lift.  If you feel resistance STOP, investigate the problem.  You can do serious damage to a turnbuckle by bending it, there is that much mechanical advantage to this A-frame.  When all is clear continue pulling / hoisting till the mast is vertical.
    HINT - If you taped the turnbuckle toggles together it keeps them upright to prevent buckling while stepping the mast.  Similarly tape the toggle of the backstay turnbuckle in the upright position.
    NOTE - There is not enough mechanical advantage to lift the mast from horizontal with just the A-frame.  For this reason lift the mast the first 3' by hand and pull the line while standing in the cockpit.  Alternatively, if you make the transom support post telescopic and extend it up 3' with the mast resting on it, you will have no problem starting the lift with the A-frame. THIS IS THE ANGLE FROM WHERE THE SYSTEM IS STRESSED AT ITS EXTREME.  Be cautious.

  10. Once the mast is standing, secure the free end of the block and tackle line to keep the mast standing.  Then walk forward and push the A-frame down on the deck with your body weight.  This holds the mast forward via the halyards and forestay.  Transfer the forestay from the A-frame to the stem fitting and snug the turnbuckle.  Lastly, transfer the halyards to the pulpit for storage.
    HINT - If you pulled the mast up using just the forestay have your helper push and hold the mast forward while you transfer the forestay from the A-frame to the deck fitting.  Alternatively pull and hold the mast forward with a line around it and the free end secured to the deck.
  11. Snug up all turnbuckles.  Use a free hanging halyard to determine if the mast is standing straight (left / right) and raked aft about 6-8".  Tension the rigging and lock the turnbuckles. 
  12. Remove the A-frame and transom support post then store all mast stepping lines and the bridles in a bag for the mast take down in the Fall.
  13. If you have a roller furling jib now is the time to attach it on the forestay.
  14. Reverse the procedure to lower the mast. 

If you have never stepped a mast before, rehearse this procedure in your mind so you know it cold when you do the job.  Go through the motion, doing several dry runs if you have to.  Nobody will pass judgment on such an important job as this.  Practice, practice, practice till everybody understands.  The astronauts do it all the time.  Whenever I have a "green horn" to help me, I always go through at least two dry runs with them till I know they understand.  You know they understand when that squirrelly look on their face changes to a "light bulb" smile.  If you don't get that light bulb moment, change your description of the process!  Go slowly so no steps are missed. 
I once helped a guy lower his mast and quickly discovered he knew very little about the procedure when the mast stuck at just above horizontal.  His lines were too short (tightened to violin tension) preventing the mast from being fully lowered. It was scary how quickly he was willing to cut a crucial line in the urgency of the moment to prevent deck fittings from being ripped out.  Had he done so, the mast would have dropped and likely broken.  As it was, some kind hearted dock watchers supported the mast so we could release the lines and then we all lowered the mast to the deck.  After discussing the problem, he still didn't realize the physics of a mast base that pivots on the cabin roof, well above the deck where the A frame feet pivot are.  Sometimes the obvious isn't obvious to all!  But it does demonstrate the need to fully understand the problems at hand.   TOP

Words are all fine and dandy but picture often demonstrate the procedure better.

1 - This was my first time using the new A-frame and my buddy Ron was curious about my latest gadget so he came along to help.  The road tie down lines were  released, shrouds freed from fittings and deck cleared of gear. Windex and VHF antenna attached to mast head.

2 - Mast was carried aft and the foot aligned to the tabernacle. Here I'm twisting the mast into alignment so Ron can insert the hinge pin.  Note that the mast is supported by the transom support post.

3 - Hinge pin is inserted. I made this custom hinge pin because everybody had a difficult time inserting the factory pin through the tabernacle and mast base.  The end of the pin is slightly tapered to facilitate easy insertion.  The loop on the end makes it real easy to manipulate the pin.

3a - Hinge pin is made from 1/4" stainless steel rod.  I bent one end back on itself to create a loop for easy extraction. There is a hole drilled through the rod for a split ring or a safety pin.  I have since replaced it with a stainless safety pin for greater security.

4 - Final check of A-frame, forestay is attached to the apex of the A-frame, block & tackle line is attached between the apex and the bow.  Halyards not yet attached to the A-frame.

5 - Turnbuckles loosened and standing up. All lines clear. Mast ready to be raised.

6 - Steady the mast sideways during the bottom portion of the lift to protect the mast step when the boat is floating or in a side wind. Its a bit wiggly on a floating boat.

7 - Mast is almost vertical with the A-frame pulled down to the deck.  It is important to push the mast fully forward while attaching the jib halyards to the bow so you can safely transfer the forestay to the bow fitting. 

NOTE - I no longer use just the forestay to step the mast.  I now use both jib halyards (two wraps around a A-frame arm) to step the mast with the forestay attached as backup and to have it within reach to transfer it to/from the forestay fitting.  Once the A-frame is down on the deck (mast is standing) and the hoisting line secured, all I have to do is walk to the bow, transfer the forestay to the stem fitting and tighten the turnbuckles.  I also now use temporary shrouds to eliminate sideways movement of the mast.   TOP

MAST HINGE PIN - The factory hinge pin is difficult to insert through four misalignment mast base holes or to remove since there is no hand hold.  I made a replacement pin from 1/4" stainless steel rod.  One end is bent back on itself to create a 1" diameter loop for easy handling.  The other end is slightly tapered for easy insertion through the four holes and has a hole drilled through the rod to fit a hair pin through.  You could drill a second hold near the ring for a second hair pin.

COMMENT - "Using an A-frame to step the mast is so effortless that it takes all the worry and frustration out of the job.  There is minimal sideways movement of the mast when using temporary shrouds.  We stopped several times during the lift to check on things and to take these photos.  I wouldn't dare stop in the middle of a lift using the hand over hand method.  The deck pads stayed in place and the hinges worked perfectly.  I've used this A-frame to step the mast of several other SJ23s and an SJ7.7M and only tied the deck pads with a short length of line.  This poses no problem as they stay in place with the slight force that pushes them aft to the stanchions.
Despite the ease with which I describe the mast stepping procedure I still recommend this is a two man job.  That is unless you use temporary shrouds to eliminate side swing.  The reason is that steadying a 27' mast in a side breeze can be a daunting load.  Better to align the hull to the wind.  If it is too windy, better to find a coffee shop!"  TOP

Replacement SJ23 Mast - If you "intend" to break your mast or want other replacement rigging parts, contact:

Stephen Jensen
1(206) 714-9661 (4:30pm - 7:30pm Pacific, please)

He has lots of parts and can get just about anything else that isn't in stock.

Replacement SJ24, 26, 28 or 30 Mast - If you want replacement rigging parts for these models, phone:

15230 NE, 92 St.
Redmond, Washington.
1(206) 883-2126 (Pacific)

NOTE 1 - If you wish to leave the A-frame in place while towing, then suspend the apex of the frame from the mast with a line up to the mast.  This prevents the frame from pounding on the deck and punching a hole through the gel-coat.  In addition, you could use a tie down line to prevent the frame from bouncing up to the mast!  To date I know of eight A-frames that have been built using these plans.  Mine has stepped dozens of boat masts.  Hmmm, I should say this qualifies for a free grog!  

Here is a U-Tube video of exactly my system

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