Swapping out outhaul -- question about line diameter

obelisk · #1 (**permalink**) 12-23-2009

I´m swapping out my outhaul and genny sheets and have run into a snag in measuring. My old outhaul is Sta-Set and I believed it to be 1/2" but when I compared it to my new mainsheet (1/2" Samson XLS) it is larger in diameter. The 1/2" Samson measures under 1/2" and the Sta-Set is right at 1/2". Both were under about the same load when measured.

How much is line diameter affected by load and would the effect be different between these two brands and models? I have not swapped out the outhaul yet--could it be 9/16" Sta-Set that measures 1/2" when under load?

???

zz4gta · #2 (**permalink**) 12-23-2009

I think you're asking the wrong question. What load is on the outhaul for that boat?

To answer your question, tension on the line will effect the diameter a bit. It will very depending on cover/core material and braid.

obelisk · #3 (**permalink**) 12-23-2009

There´s quite abit of load. I would like to push the size up as far as possible. The determining factor is the sheave size in the cheek blocks leading backto the cockpit.

More to the point--Could the line I have already be 9/16" Sta-Set if it measures 1/2" (with calipers) when under load? It is old and somewhat worn. The breaking strength of the 9/16" is more appealing but I don´t want to buy 80´of it and find that it chafes on the sheaves running up to the boom.

blt2ski · #4 (**permalink**) 12-23-2009

Lets look at this a different way, Figure out the load, and find the line diam that will fit the sheaves without chafing.

There are a few of us that prefer to go to something stronger than Sta-set. I am one. I dumped ALL of my staset and went with Sampson's XLS Extra which gives me the ability to go with a 3/8" line, that is still stronger than the 1/2" line it replaced, with less stretch at the same load. Along with I do not have to worry about being at the larger diam end of the spectrum to have chafe going thru my sheaves.

Not sure if this is really what you want from an answer, but another way to look at it.

Also, while the XLS I used vs Sta-set is more $$ per foot, about double for the same diam, by being able to go to a smaller diam, the actual increase was more like about 40-50%.

Also, for my out haul, I use a 3/16" steel line rope equal. It is stronger than the 5/16" lines I use for halyards. BUT< being as I only need 25', $30 for the line is nothing compared to the lesser amount of chafe, along with less friction to deal with when adjusting the outhaul. which being as I race my boat, this is something I worry about. A cruiser that has a set it and go for the next two hours....may not worry about every .1-.3 knots with an out of adjustment line.....

PS on edit, if you go to Harken IIRC, or maybe PYACHT.com or sailnet.com store or, some other online sources, there are pages with in these sites that you can look your boat up, or go to a chart with sail area and will tell you the max load with different wind conditions. From here, you can then choose a line with the strength to fit your sheaves, and not stretch either, have better performance too.

Good luck.
Marty

roline · #5 (**permalink**) 12-24-2009

For the outhaul, line diameter is only concerned over running through the blocks and hanging up internally. The tensile strength is a bigger concern. Dyneema, Vectran, PBO are stronger than polyester and can be downsized for the same tensile strength. I downsized to 1/4" inside the Cal 9.2 boom by using a super fiber double braid. Breaking strength over 4,000lbs. The only down side is that end termination , spliceing or knots becomes the weakest link and must be done with care.
For genny sheets, what feels good in the hands and works with the winches especially self tailers is most important. Some of the outside braids on the low stetch lines will not feel good in the hand.

obelisk · #6 (**permalink**) 12-24-2009

The major hang up is that I am in Buenos Aires right now and options are limited. There is a huge sailing community here, but mostly in the 30-35' range so too chandlery is sized accordingly. All Spectra, Dynema, etc. is too small for my selftailer on the outhaul (Barient 28).

I calculated the load on the outhaul with the (windspeed)*squared*X.004X(sail area in sq. feet) formula and came out to a number much less than I would have guessed. I used 25 kts for windspeed.

625x.004x651=1627.5lbs

This seems too low, but that's just a feeling. By that calculation, 1/2" would be fine. Realistically, that's my only choice down here anyway!