Notice:
The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.
Oh sure, Let me just run out to my machine shop and whip one of those out!
Wait! Let me mail the cardboard prototype to you first!
All the measuring and thinking that has gone into this stupid thing and we still have to walk the (tall rig) mast up quite some ways before the block and tackle can take over!
I made an A-frame out of 2 x 4's exactly like Scott's photo above, but since I rarely use the A-frame, I attached the base of each leg simply by tying a 3/8 inch line or a piece of strong wire cable throught the A-frame hole at the bottom and through the chainplate. That allows easy rotation and needsno special fitting to the chainplate.
You asked about the size of the legs. Yo proabably did not mean the size of the "feet". For legs, I used 12 foot 2 x 4's, and OJ's cadillac version uses 9 foot conduit sections.
There is little difference with different leg lengths for a standard rig mast (~28 feet in height) with no furler. If you are dropping and raising a mast with a furled jib still in place, there is considerably more weight to hold up, and longer legs provide a little more leverage and stability down to an angle of 45 degrees.
For a tall rig mast you may want longer A-frame legs, and with the weight of a furler and jib particularly.
Below 45 degrees, I found that this setup that drops the A-frame with the mast kept the mast well under control, and even with some sideways breeze it was easy and safe to continue lowering the mast slowly and catching it in the cockpit with one hand while feeding more line to the A-frame turning block on the bow.
I learned that my 28 foot mast weighs something like 75 pounds and is easy to guide into the crutch that I simply attach by tying with lines to the pushpit.
I've only done this single-handed, but having a helper or two hold the mast centered and then guide it into the crutch would make the process very straightforward.
I just made the A-frame utilizng Davey J's examples. I must have screwed up something as I am bending the bolts I use to secure the a frame pipe to the pipe nipples at the chainplate. while testing the arc, it binds up and bends the bolts at around 40 degrees.
Sounds like your holes are drilled 90 degrees apart (top to bottom) and they should have been drilled to line up with the holes in the chain plates which is not quite 90 degrees from the holes at the top of the nipple.
Slide the nipple down over the chain plate and line up the holes at the bottom of the nipple with the holes in the chain plate. Then standing directly above the nipple look down and see how the holes in the top of the nipple line up with the holes in the conduit. I'm betting you will see that they should have been drilled at a different angle so they would line up with the holes in the conduit. If they are at the proper angle there should be almost no binding. Definitely not enough to bend the bolts.
Hey Gary, not binding there, when the frame moves thru it's arc, it is wanting to twist the pipe nipple arrangement. The nipples are secure with the holes on the chainplate.
The best way to get the angles right is to first drill the holes for the pipe nipple to the chainplate. Now Bolt the nipple to the chainplate. Now lay the A frame out on the deck exactly like its suppose to be when it if fully built. Put the leg of the A frame against the pipe nipple and drill the hinge hole through the nipple and the leg keeping the drill 90 deg to the leg, If you do this correctly (90deg to the leg) that hinge bolt should angle slightly toward the back of the boat.
Also when you bolt it all together don't make the bolts too tight in the hinge joint. Finger tight will do. This will leave some play in the A Frame and will reduce any binding that might occur.
Perpendicular to a plane through the particular shroud and the mast. Run a line from the mast to the chainplate and set the cp perpendicular to it. It isn't that critical.
Here's a photo so you can see how they face. There should be 2 screws in the deck flange that keeps them from rotating You can see them in the photo, And a Aluminum backing plate on the interior of the boat.
Interesting, mine are about 90º to yours and were presumably built that way since there are only two screw holes underneath. I don't see any reason for concern since they load a single, centered stud The shrouds are angled in two planes and the cp.'s cannot align perfectly to both. Close enough, they don't appear to have weakened the deck or pulled through in 35 years.
quote:Interesting, mine are about 90º to yours and were presumably built that way since there are only two screw holes underneath.
Thats strange... Seems that the chainplate is vertical and the shroud is angled. Your set up would put all of the load/tension on the outside of the toggle no?
Thanks Bruce, That is actually a bread board I found in a store and re- worked it a bit. It opened up the interior and is still big enough to put a cold one on or dinner for two. I still have the big table down in the basement so the next owner will have 2 tables to choose from.
Notice: The advice given on this site is based upon individual or quoted experience, yours may differ. The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.