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 Catalina/Capri 25/250 Sailor's Forums
 Catalina 25 Specific Forum
 170 Genoa Dimensions		  New Topic  Topic Locked
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Bruce Baker
Captain

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USA
402 Posts
Initially Posted - 07/15/2004 :  09:43:15  Show Profile
I'm getting ready to order a 170 genoa, but I've got a few questions about the dimensions. I'd like to measure twice, order once, if you know what I mean.

According to our website, the J (foredeck) dimension is 10'6" and the I (mast) dimension is 29'0". That makes the luff 30.84' or about 30'10". According to the website, the maximum luff length for racing purposes is 30'0". However, the owners' manual (older) on the website says the forestay is 29'10".

Also, I don't quite understand why the way sailmakers use the LP (luff perpendicular) the way they do for measuring sails. I understand that the luff length must remain fixed while the foot can vary, so using the luff as the "base" and the LP as "height" makes sense. What doesn't make sense is using 170% of the J value instead of 170% of the LP of the forward triangle (9.68).

Questions:
1. Is the forestay 29'10 or 30'10?
2. Off-the-shelf sails have a luff of 29'5". Is that to provide some room for error, or to allow C-25 sails to also fit C-250's?
3. Why use 170% of the J? Is this some kind of weird rule like the Twelve Meter Rule (12-meters are about 75 feet long, not 39 feet).

Thanks,
Bruce Baker
Falls Church, VA
"Yee Ha" 3573
'83SR/SK
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Bill Holcomb
Admiral

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USA
769 Posts
Response Posted - 07/15/2004 :  10:30:52  Show Profile
Hi Bruce,

Remember that most of our boats have gone through several owners and that PO's have a habit of making modifications that may not be obvious. I remember looking over a std rig C25 a few years ago that seemed to have very different shroud and stay lengths from factory. Later I found that the mast base had been damaged. So, the PO cut the base off, drilled a new hole for the pivot bolt, and had all the standing rigging shortened. So, what length is your forestay??? The factory spec says that the standard rig forestay is 29'10". Tall rig = 31'10". You should measure yours though to be sure.....and factor in the length of the turnbuckle and turnbuckle bolts.

The reason for the jib luff max length being a somewhat shorter than the forestay length is two-fold. The shorter luff allows you to stretch the luff (that's why the mast winch is on the port side for the jib sails). Tighter luff equals moving the sail draft forward. And, tighter generally means flatter sail. Tight for stronger winds. The shorter luff also allows you to secure a short pigtail to the sail's tack corner. This raises the foot and gives you somewhat better vision forward.

Why use percentage of J?? Fairness. By using the LP, sails with the clew corner higher or lower above the deck should have approximately the same square footage as other sails using the same LP length but a different clew height. A roller furling 135% will have the same square footage as a "deck sweeper" 135%. If you just used the J measurement, a higher clewed sail would be smaller than the deck sweeper. J is the standard length within a class then for 100% LP.

Bill Holcomb - C25 Snickerdoodle #4839
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JimB517
Past Commodore

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USA
3285 Posts
Response Posted - 07/16/2004 :  14:22:41  Show Profile  Visit JimB517's Homepage
Hey, send us a photo of the boat flying a 170. Thats a massive sail!
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sbenson
Deckhand

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USA
12 Posts
Response Posted - 07/24/2004 :  04:33:44  Show Profile
The luff length of your sail on a std rig will be approximately 29'6". This is the deminsion that my sailmaker ended up with and the length you get from Catalina tech services. The measurement your sailmaker can use most is the length from shackle to shackle. Take a rope, fasten it to your halyard, hoist it to the top. Then mark at the lower shackle. Then get the length of the rope measurement.
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Notice: The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.