Thanks Garry. J is defined as the horizontal length of the base of the foretriangle from the landing point of the forestay on the deck to the front side of the mast. For a 30 MK I that landing point is the chainplate at the top of the bow stem. A horizontal line aft from that point meets the front of the mast just below the partners. But I don’t think that invalidates the geometric estimate of forestay length.
In any case, I’ll be measuring it this weekend using a tape on a genoa halyard from the bow, and I'll report back. I’ll have to compare the halyard sheave height to the forestay attachment height and adjust the measurement accordingly (I can’t go up the mast right now because the boat is shrink-wrapped). This is all for the purpose of determining the luff length for a new sail I’m ordering to go on a new furler I have yet to install - a Selden Furlex 204S. Selden has calculators for the luff length, that take the forestay length as an input. Cheers, Randy SV Grenadine > On Jan 22, 2022, at 9:01 AM, Garry Cross <garr...@gmail.com> wrote: > > I doubt the geometric calculation you are using will work. A straight line at > right angles to the mast will likely cross the bow line below where the > forestay attaches. > If you have a halyard that turns near where the forestay attaches, you likely > will get a closer approximation than the geometry method. > > According to sailboatdata.com <http://sailboatdata.com/> > Est. Forestay Len: 41.27 ft / 12.58 m > Seems your calculation agrees with that. > > > On Wed, Jan 19, 2022 at 7:51 PM Randy Stafford via CnC-List > <cnc-list@cnc-list.com <mailto:cnc-list@cnc-list.com>> wrote: > Hello Listers, > > Does anybody know the forestay length of a 30 MK I as it came from the > factory, with the rig properly tuned for 8” of mast rake? > > By geometry (square root of I squared plus J squared) I’d expect it to be in > the neighborhood of 41’3”. I is 39’ for a 30 MK I, and J is 13.5’. > > According to the owner’s manual the forestay cable is 1/4” and the lower > fitting is <quote>1/2” jaw to jaw turnbuckle & toggle</quote>. On mine, the > cable is swaged into an eye fitting on the lower end, which is pinned to a > turnbuckle screw that’s probably 1/2” jaw to jaw (if that’s what’s meant by > the owner’s manual). The screw at the other end of the turnbuckle is > identical, and is pinned to a toggle that’s pinned to the bow stem. Picture > at > https://drive.google.com/file/d/1ZT794BQaw0R8aWZCK9NqmVqRJ9K85VT9/view?usp=sharing > > <https://drive.google.com/file/d/1ZT794BQaw0R8aWZCK9NqmVqRJ9K85VT9/view?usp=sharing>. > > I’m wondering if this is the standard from-the-factory setup, and what the > overall forestay length is from pin at masthead to pin at bow stem, when the > rig is properly tuned. > > Thank You, > Randy Stafford > SV Grenadine > C&C 30 MK I #79 > Ken Caryl, CO > Thanks to all of the subscribers that contributed to the list to help with > the costs involved. If you want to show your support to the list - use > PayPal to send contribution -- https://www.paypal.me/stumurray > <https://www.paypal.me/stumurray> Thanks - Stu
Thanks to all of the subscribers that contributed to the list to help with the costs involved. If you want to show your support to the list - use PayPal to send contribution -- https://www.paypal.me/stumurray Thanks - Stu
