I'm so pleased with my arch that I wouldn't consider a JR without one, if your sheets are mounted aft of the cockpit. When gybing I know I can just duck under the arch and my neck will be fine. 

The arch also provides a great support and handhold for standing up in the cockpit and steering with my feet, good for stretching, mount point for cockpit awning, and stronger handhold for climbing into the boat than the stanchions.

I seem to recall seeing one in a photo made with flexible white plastic water pipe, strong enough to deflect slack sheets but nothing more. Might be better than nothing in a pinch and to mock up a final design. Mine is 1.5" (38mm) stainless. We didn't have a pipe bend for that size, so we ended up with a 5-sided arch with 45 degree sides. It does the trick, but an rounded arch would have been nicer. I have tied one end of cockpit cover to the arch, but the combination of the lashing and the angles in the arch tend to hold up the sheets on some gybes. Much rather that than my neck, though.

On Tystie, I'm sheeting my high AR sail to the arch over the cockpit, as I found that it was counterproductive to sheet as far aft as the transom - the sail was being hauled aft, rather more than it was being hauled in. The arch is of 38mm x 3mm wall alloy, and will carry the vertical loads, but wasn't designed to take the fore and aft loads, so I have added a 6mm bare Dyneema line under tension between it and the pushpit, which was designed to carry the sheet loadings. This setup has been OK during my crossing of the Pacific.

On SibLim, we're thinking of putting the deck blocks right at the after end of the deck, over the companionway, as there is to be no sliding hatch. This will get away, very neatly, from the problems of having the sheet sweep over the cockpit and having to lead the tail of the sheet forward around the cockpit to the winch and jammer near the pramhood.

Gary Pick wrote:

What grade alloy did you use David?

It would have only been T5. I seriously bent the frame on one occasion because the sheet got caught up in the bimini hoops which were lashed to the frame. But it all straightened out and I got some reinforcing added to the frame and I have not had any problems since. If you have a look through the New Caledonia album on my profile pics you will see several photos of the bimini frame/sheet deflection arch. It's that thing we are grabbing hold of in the cockpit. I could have had it made in stainless steel except Footprints is not a stainless steel kind of boat. Aluminum is light also and I am always conscious of weight.

My arch is mounted well inboard of the gunwale because if had been the full width of the cockpit the sheet would have fouled it on many points of sail. So as with everything on a boat there was some compromise! 

A sheet deflection arch is a great safety feature. I added one to Footprints after some near misses with the sheet, with our 53 sq m sail getting caught up in the sheet during a hard gybe could be lethal. My arch was designed to also serve as the bimini frame so the shape was more of a square with rounded corners but this does allow the sheet to get caught up on the frame sometimes, so a more rounded arch would be better. Ours is also in the middle of our very large cockpit and has proven very handy as a grab rail and also something to lean against while helming.

After looking at the various fabrication options including self build, in the end I had ours fabricated out of 40mm diameter alloy tube which I have left unpainted. Cost was about NZ$350 which did slightly shock me at the time but then it would have taken a lot of time for me to laminate something out of timber, plus the cost of the timber and epoxy.