Originally Posted by Brian.clarity
So I would need to reinforce that bulkhead?
Depends on what's there.
A 3/4" bulkhead that is tabbed to the hull
on both sides would be fine. If the bulkhead is just a partition that is not tabbed, sounds like you need to do some fiberglass
work. If the bulkhead is particleboard and not real ply, I would think about replacement, though I have seen some on boats.
The next question is how much meat is there at the top of the bulkhead, undoubtedly an access has been cut to access the chain locker and to allow maintenance
of the headstay chainplate. Specifically what is the distance from the top of the opening to the top of the bulkhead? To figure out what is enough you need to know how long the chain plate
needs to be. To determine the chainplate size you need to know forestay size. The only reference I have that discusses forestay (aka. staysail stay) size is Skene's Elements of Yacht Design which indicated it should be the same size as the headstay. Discussions of Skene's in other references
indicate that Skene's is very conservative on headstay size to begin with and is really overdone if there is a forestay too. Given that discussion and the fact that dead loads in the fore and aft direction will now be carried by 2 stays instead of one so I would be comfortable using the smallest wire size used in the existing rig, probably one of the shrouds. It may be that all of the wire is the same size in which case go with that.
Knowing the wire size will give you the turnbuckle size, which will in turn give you the pin size assuming you stay with standard sizes. For arguments sake lets assume a 1/2" pin. At RIGRITE
a standard flat chain plate (you would need to bend the top over to suit) would have 5-1/2"dia bolts thru the bulkhead at 2-1/8" centers. Given the need for meat below the bottom bolt and space for the nut and wrenches on the top bolt lets say you need 5 spaces or 10-1/2' of bulkhead. It's kind of iffy that there will that much meat in the bulkhead over the access opening.
Given the need to access the headstay chain plate for inspection
you don't want to fill up this opening. The number of bolts into the bulkhead is based on the bulkhead capacity, not the bolt or chainplate capacity so if the bulkhead were stronger you could get away with fewer bolts. In which case I would be comfortable with 2 bolts and happy with 3.
In order to make the top of the bulkhead strong enough I would get 2 plates of stainless 1/4" less in width than the maximum amount of meat in the bulkhead over the opening, same thickness as the chainplate (1/4" minimum) and long enough to span from the tabbing on one side of the boat to the tabbing on the other. I would not run these plates onto the tabbing. The plates need to be scribed and trimmed on the top to follow the deck and leave the 1/4" gap to the deck. If the deck is flat then no trimming will be necessary.
Next you need to layout the bolt holes. At the center you will need holes for the chainplate. The best way to do this is to clamp the pieces together and drill thru the holes in the chainplate into the reinforcing plates. Holes should be 1/16" larger than the bolts, so for 1/2" bolts use a 9/16" bit. During drilling you will need a cutting fluid (see this link for several different recommendations) on the bit to maintain bit sharpness. I would make the holes along the plates have the same spacing as the chain plate but staggered them top and bottom with the same edge spacing the chainplate has.
After making the first plate, clamp the second plate to it and drill thru the holes to guarantee that everything lines up. When drilling use a drill press or at least a guide so keep the holes normal to the plates. When drilling the wood clamp the plates in place, drill and install 1 bolt at each end before drilling the rest of the holes. Use the same bit, 1/16" oversized. Make sure to use stainless bolts.
Once the plates are installed THEN cut the deck for the chainplate, that way you don't get it in the wrong spot, the most obvious mistake would be to cut the deck at face of bulkhead rather than the thickness of the plate forward of the bulkhead. Now install the chainplate. You will need to bed
around the chainplate the same as all others on the boat.
See attached sketch for how I would do it.
This give you a tang sticking up out of the deck that a turnbuckle could be attached to. Securing the tack of the sail will take some additional thought.
Alternatively install a 90-degree toggle and an extra long shackle onto the tang. With that in place you can install a Staysail Release Lever
from Lin & Larry Pardey's website. Now you have a removable staysail that won't impede short tacking with the headsail.