SJ23 Tech Tip F18, (Reissued 2014-09-01, Bob Schimmel)

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

Stepping a heavy mast on a sail boat can be a dangerous job.  It can also be expensive to replace a dropped mast, not to mention paying for what you hit!  An SJ23 mast probably weighs close to 150 pounds, plus whatever wind force you have to deal with.  For these reasons it is important to control it as much as possible. 
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 manoeuvre it over the ground.  Similarly, an A-frame can be mounted on the edge of a work barge as a very robust yet simple crane.  You don't see them anymore today because it is quicker to rotate a hydraulic knuckle crane on the barge than rotate the whole barge.  Either of these methods is simply a convenient way of moving a heavy object through the short range of a "gin pole" or an A-frame. 

Years ago sail driven commercial canal boats in Holland were equipped with an A-frame as a permanent deck fixture to lower the mast so the boat can slide under an unattended 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.  Blocking the canal to other commercial traffic 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 and lots of control to minimize sideways movement.  The longer or taller the A-frame is relative to the mast length, the greater the mechanical advantage.  The huge control that you achieve 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.  I have done this quite a few times with no problem.  The less time you spend in the transition zone with an unsupported mast the better.  If the wind is really strong, park the boat somewhere and go find a coffee shop to wait it out!

CONSTRUCTION - Fabricate your A-frame in the sequence that the components are described here.  It reduces your chances of making an error relative to the effort required to make each component.  Cut the poles, attach the foot hinge plates to the poles, bolt the plates to the T extrusion on the foot pads, screw the T extrusions to the wood pads and finally, cross the poles to form the apex and drill the hole through the two poles for the apex hinge.  By following this procedure you eliminate a bunch of complex measuring that will likely be off by several degrees making for misaligned hinges that can't pivot.  The chances of you measuring it correct are minimal!  Remember, Murphy! 

A-FRAME 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.  The apex fits just short of the forestay fitting, leaving room to easily transfer the forestay from the A-frame to the deck.  It is prudent to attach the forestay to the deck 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 shouldn't vibrate or buckle 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 wood.  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 clamps over the end to reinforce the pole end.  If you saturate the pole ends with epoxy for strength and coat the wood with Cetol, it will protect it from the elements.  Another simple method is to use 1/8" thick metal tubing slipped over the pole end, leaving 6" of metal protruding beyond the wood.  Flatten the 6" protruding tube 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 bit than consider Two shorter poles joined with a sleeve to make a longer one.  This would allow you to store the assembly in a small space.  A great way to go if you are a globe trotting sailor who wishes to be independent of shore services.   TOP

A-FRAME FOOT HINGE & DECK PAD - There are two ways you can fabricate a hinge; make it fully articulating so the poles always align to the deck or make it fixed so it aligns on the same plane as the poles pivot.  I built the latter design because it is simpler, I had the material and I was in somewhat of a hurry. 
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.  (If you used 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

 

A-FRAME 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!   It may look unsophisticated but it works, it is easy to make and stores well.  Assemble the feet, bolt the poles to the feet, cross lap the poles, lock them together and drill a 1/2" hole through the middle of both poles.  Insert a 1/2" 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, one in each pole, just below the apex hinge bolt.  If you can find a long enough eye bolt to go through both poles so it also makes the hinge, all the better. 
The forestay attaches to the aft facing eye bolt and the 4x1 block and tackle attaches to the forward eye bolt.  Be very careful in drilling the two holes.  Alignment of the moving parts is critical.  If you are off by a little bit, the hinge will bind.  I suggest making the foot hinges first, assembling them on deck, then drill the holes for the apex hinge.  Finally, test your frame by swinging it through the full arc of the required travel; about 1350At 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 "jam tarts" are squeamish about a stick falling on them!  

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!  

 

 

 

 

RAISE THE MAST ON YOUR OWN - While I usually have a buddy to pull the mast up while I control the sideways movement, there is no reason why it can't be stepped by one person, even in a wind.  Seems I always have gusty winds when I do this job!  Lines tied to the side of the mast will control  the sideways movement of the mast.  But given the fact that the deck elevation is below the mast pivot point, you can't just attach lines to the toe rail.  They will instantly go slack as the mast is lowered.  You have to artificially raise the deck with two bridles.  At the middle of each bridle is a ring positioned at the pivot axis of the mast step (deck plate).  By terminating the temporary shrouds at the mast pivot point it prevents the shrouds from binding as the mast is stepped and eliminates the sideways movement of the mast.  This frees you for pulling on the hoisting line beside the mast.   It may sound complicated but isn't.
Make each bridle from low stretch 3/8" line, 1 welded ring, 2 carabineers and 1 low stretch shroud.  The bottoms of the bridles are clipped to their respective toe rail with the carabineers so each ring is positioned above the toe rail, at the same height as the mast step.  A temporary shroud is attached to each ring and the upper ends of the shrouds are tied snugly around the mast and tensioned with the main halyard to a few feet below the spreaders.  Now all you have to do is raise the mast using the procedure described below. 

Here is a variation of this technique using a sliding spinnaker ring on a track. http://www.klackospars.com/about/mast-raising-magic.html

A-FRAME MAST STEPPING PROCEDURE - Inspect the standing rigging where it attaches to the mast.  All cotter pins must be rolled over 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 it.   This is oscillating bending which will induce fatigue, resulting in breakage at the kink.  This is exactly the same process as flexing a piece of metal 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 intend to 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 back.  Also, ensure you are on the shore side of any overhead electrical power lines or other obstructions.  (An alternative is to float the boat in calm water, hopefully pointed into the wind to eliminate side forces on the mast.  I was forced to do this once, but never again.  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 it from 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 Morley lines to control sideway movement of the mast.
  5. It is assumed the standing rigging is attached to the chain plates correctly and was never removed from the last take down.
  6. Extend the shroud turnbuckles 3/8" up from the tuned sailing position by turning the barrels.  This prevents excessive pull on the rigging and side load on the chain plates as the mast is raised.  (Ensure there is at least 1/2" of thread screwed in). 
    - Tape the bottom swivel of each turnbuckle in the upright position. 
    (This is important as it prevents them from bending over, binding and breaking). 
  7. Close the companionway sliding hatch. (Don't step 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 or tabernacle.  Rest the mast on the transom support bar.  While holding down the foot of the mast, insert the hinge pin and locking cotter pins in EACH end 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 bolts.  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 A-frame bars, close to the apex.  You should use all your lines (forestay, jib1, jib2) to equally pull the mast up.  This adds extra security in case one breaks. 
    When you go forward to transfer the forestay from the A-frame to the stem fitting, it will be conveniently at hand.  If you shorten the halyards about a foot less than the forestay you can hold the A-frame down to keep the mast standing with your body weight. 
    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. Pull on the free end of the block and tackle to raise the mast, watching 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.  
    HINT - If you tape the bottom turnbuckle swivels together it keeps them upright to prevent buckling while stepping the mast.  Similarly tape the bottom swivel of the backstay turnbuckle in the upright position.
  10. Once the mast is vertical, secure the block and tackle line to keep the mast up.  The walk forward and push the A-frame down on the deck with your body weight.  This pulls the mast forward with the halyards and forestay. 
    - If you pulled the mast up with just the forestay have your helper push the mast forward while you transfer the forestay from the A-frame to the deck fitting.  Alternatively pull the mast forward with a line around it.
    - If you use the shortened halyards to pull the mast up hold the A-Frame down to the deck to keep the mast standing while you transfer the forestay from the A-frame to the stem fitting.  Snug the turnbuckle and transfer the halyards to the pulpit.
  11. Snug up all turnbuckles.  Ensure the mast is perpendicular to the deck, tension the rigging and lock the turnbuckles.
  12. Remove the A-frame and store all mast stepping lines and the bridles in a bag for the mast take down in the Fall.
  13. 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 actually 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 to lower his mast and quickly discovered he knew very little about the procedure when the mast was just above horizontal.  The combination of short lines tightened to violin tension, prevented the mast from being fully lowered and nearly ripped deck fittings out.  It was scary how quickly he was willing to release a crucial line to lower the mast to the bottom.  Had he done so, the mast would have dropped.  As it was, the dock watchers supported the mast while the short deck lines were released and we then lowered the mast to the bottom.  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

 

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 is cleared of gear.

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 - The pin shown is made from 1/4" stainless steel rod.  I bent one end back on itself to create a loop for easy operation and the other end has a hole drilled through the rod for a cotter pin.

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 - Windex and VHF antenna attached to mast head. Loosened turnbuckles 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 - In future the 2 jib halyards will be attached to the A-frame to pull up the mast.  The forestay will also be attached and all three will pull equally.  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.  This will require bridles to limit sideways movement of the mast.   TOP

 

MAST HINGE PIN - The factory hinge pin is difficult to insert through the 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.  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.  There is only a slight force to push them aft towards the stanchions.
Despite the ease with which I describe stepping the mast I still recommend that this is a two man job.  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 at SAN JUAN SAILBOATS.  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 SPAR TECH - 15230 NE, 92 St. Redmond, Washington. 1-206-883-2126.

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.  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!  

 

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