Hi Garry, Today I measured my forestay using a tape measure hoisted on a genoa halyard. Its length was 40’ 1.5” with the turnbuckle more than halfway extended (photo at https://drive.google.com/file/d/1sxleLIDl3c1WqF-PZ0XumIcFVJU8toRb/view?usp=sharing). That’s from the masthead attachment point to the clevis pin holding the toggle to the chainplate. That’s as accurate as I can get without going up the mast, or removing the forestay and measuring it stretched out on the ground.
Cheers, Randy > On Jan 22, 2022, at 11:21 AM, Garry Cross <garr...@gmail.com> wrote: > > Good to know. I should have looked it up. I had to get a new furler as my old > one broke. It was a bad mistake by me unstepping the mast. So the mast was > down. Got a new forestay as I had no idea the age of it. Sadly the new furler > tack attachment point was almost a foot higher. As a result required the #2 > Genoa to be cut. Mast was up when I realized this. Measured with a tape > measure and the slider on the furler. > Turns out I should have subtracted some. I would say if the length was any > longer it would not be tight all the way up. .5 in shorter and I could then > tension the luff to a more desirable tension. Since it is in the slot all the > way up it looks fine. Just not perfect. > > On Sat, Jan 22, 2022 at 11:45 AM Randy Stafford <randal.staff...@icloud.com > <mailto:randal.staff...@icloud.com>> wrote: > 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 >> <mailto: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
