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Am I correct in assuming that the bearing surface referenced in CR 5.6.1 is not required to be in the plane of the deck? In the most trivial case, a commercial stem head fitting would have the bearing surface above deck.

5.6.1 Intersection of the head stay and the bearing surface of the bow fitting shall be between 1" (25mm) forward and 2" (51mm) aft of the forward face of the bow.
5.6.2 J measured from the forward face of the mast to the intersection of the head stay and deck shall not exceed 89.5" (2273mm).

For example. if the headstay leads to a below-deck block I need only be concerned that the point of tangency between the head stay and the bearing surface of the block is between 1 inch for'd and 2 inches aft of the forward face of the stem, regardless of the vertical location. The intersection of the forestay and the deck might possibly be farther aft than 2 inches abaft the bow in that case, although I don't think that would necessarily be desirable.

I could be wrong, and usually am, but I think the intent of the rule is to put a limit on J. Therefore, if you are thinking of installing below-deck furling, J70 style, then I don't see any issue with that whatsoever. What you lose in J is probably going to be gained back, performace-wise, by lowered tack height and better end-plate dynamics.

Hope this helps.

I wonder ...

CR 5.6.1 seems to control rig location, albeit loosely. It is 5.6.2 that specifies J. Look at sketch A, with a standard stem head fitting. Here J is 'close' to the bearing point, but the intersection of the forestay and the deck is forward of the bearing surface. Cases B and C are the other way around, with the J point aft of the bearing surface. The block in C is fixed to the boat on its axle: am I correct in assuming that the bearing surface is the contact between the sheeve and the forestay? If the forestay block is free-standing is the bearing point the pad-eye on the after face of the stem to which the block is attached?

Does 5.6.1 simply mean that the forestay is supposed to attach 'somewhere near the bow' (+1, -2 inches)?

Where is Chad?

Yup, it clearly states 2" setback, max. I don't know what the intention of that Rule was. To eliminate the potential for a smaller J, so that boats in heavy air venues (with headstays set well back for smaller headsails) don't have an advantage? I have no idea, frankly.

All that rule does is eliminate the possibility of using a below deck furler, such as a Harken Small Boat Underdeck furler HAR478. I have no idea why the class thought that was important.

If I wanted to use one (or could afford it) I'd go ahead and put it on anyway, and if protested somewhere, I'd RET and then ask the class (such as it exists) to reconsider the Rule. But for now, I think the likelihood of your being protested for violation of class rule is about as close to zero as one can possibly get without crossing over into negative numbers.

and yeah, where's Chad when we need him....

Yeah, the 1” forward, 2” aft rule controls rig location. Early on, there were several different approaches to head stay attachments- Ron and Ben had hoops up there for their on-deck poles to slide through, with the headstay mounted on top of all that, for instance. A projected line would be a ways in front of the actual stem. Others had “typical” commercial stem fittings that almost always locate the headstay aft of the stem a little. And the earliest rule ignored all that and said “hook a tape on the stem” to determine J...
What the class didn’t want was people experimenting with rig locations -adding structure for alternate headstay locations, moving mast steps, and so on. Those can be either a hassle or expensive if it turns out that 6” aft is fast, for instance.

With regard to the drawings, I know the intent was for the stay’s location to be “near the stem”. I probably did picture a “as it passes through the plane of the sheer” intention originally for below deck hardware, but that idea isn’t expressed. (That’s how I did mine, with the bearing surface being a bushing in the deck/stem, before leading below). The wording doesn’t preclude your scenarios B or C. Both of those cases will still use the stock stem for primary structure, and seem within both the letter and spirit of the rule.

With one of those choices, I’d note that a full J length will cause your mast to either miss the f89.5 structure, or require the post to lean aft. Plan a smaller hatch, and more yoga for cabin entering!