New Inter forestay
 

Needing input on sizing for an inter fore stay on my 41 Ketch..displacement 30000

Mast and deck hardware already there..What size wire should I use...is 9/32 to small? ( have a line on a hyfield in that size is why I ask )

I want it stout enough to easly withstand 60 knots with my 100 squar foot storm jib hoisted..also will need new running backs..should I go wire or dyneema?

Inner Forestay
 

Assuming that the tang for this new inner is in the correct position for the cut of your existing sail, and that the runner tangs are all in. Then i'd pick make the new stay the same dia as the lowers, and unless you plan to make the runners fixed, then avoid wire like the plague (chafe, and pain in the arse factors), go for spectra or any other 'exotic' thats within budget.

theres me 2 cents worth enjoy...

Size relative to load
 

Hello,
As far as the size of your new forestay goes, it might well be the same diameter as your lowers... assuming those are the right size. Wire size is not relative to displacement, but to whatever portion of the total load the wire will bear. Have you run the standard calc's for this?
Fair leads,
Brion Toss

Hi Still,
What clevis pin size is the Hyfield lever?
If it's 5/8" you might want to go up to 5/16" wire.
If you plan on using the IFS for a storm sail. You would probably feel better about having the larger wire anyway.
Steve

I did extensive net search on this matter before you posted since I am wanting to install an inner forestay too. You are lucky because you already have connection strongpoints in place; I don't.

Best I could find was two separate articles: one said the inner forestay is normally two sizes smaller than the main forestay. The other said it should be one size smaller.

Okay, so the next question is: what constitutes a "size". Question is further complicated because we do have both metric and imperial sizes in the marketplace. But if we go from say 5/16 down to 9/32, is that a change of one size? or would a change of one-sixteenth represent a change of one size"?

In my opinion, for a 41' boat, one sixteenth should contitute one size. A thirtysecond this way or that way won't matter a damn.

Dyneema or spectra it is then..Thanks
\
No..nor do I know how..I'm not even sure what I currently have on the boat..I have been going to by a caliper but havent yet.

Hey Knoty..great to see you here my good friend...

The one I have a line on is 1/2 which is the same size hole in my existing deck fitting..but there is pleny of meat to drill out to a larger size..and yes this will be my "abuse mode" sail set up...:)..I dont see the anchor points on deck for the running backs but they are on the side of the mast already ..Im wondering if they had them ran to eye cars on the Genoa tracks?

BTW...Im spending a lot more time over at CF ..drop on over you would be a great addition to the site...not as much pettiness goes on over there either.


I guess the first thing I need to do then is go an buy a caliper and measure...Im starting to think the 9/32 might be too small as I want this thing to be able to act like a secondary fore stay in an emergency for safty reasons as well...I like to sail in the snot.

With a 1/2" clevis pin size you are limited to 5/16" wire that is if you choose to go with 1x19.
I would imagine that your lower shrouds are about that size. Aren't they?
I think I would rather see you go with 5/16" wire rather than drill out the chainplate just to jump up one size. Chance are, if your deck fitting is drilled for a 1/2" clevis then there's a good chance that the mast attachment is also designed the same way.
Attaching really big wire to a fitting that was designed for a smaller wire won't really gain you anything. The old weakest link thing.

I usually see a designated location for running backs like a big pad eye on the rail but I wouldn't be surprised to see them led to a car on the genoa track.
But you would probably want them at the end so as not to interfere with adjusting the genoa lead.

What's CF? Send me a PM if you have a moment.

Imperial wire sizes are in increments of 32nds of an inch. Metric wire sizes are by the millimeter.

OK..I have measured both uppers and lower'es they are both 5/16 actually .32" so I would think 9/32 would be ok for a interstay ...and like you said I only have the 1/2 holes anyway...what do you think?..

If you were at my shop I would just make it with 5/16" wire and use fittings with 1/2" holes. You have that option with 5/16".
9/32" would probably be adequate but I would think that the extra cost of jumping up one size would be offset by the convenience of having all the rigging built of the same wire. But then I think like a rigger. :)