set up for rigging


Jan 1, 2008
enid, ok
How would you set up your block and port a wrap if using a 5/8" double braid lowering line.

block in tree - 5/8" double braid, 5/8" hollow braid (tenex/yalex), 3/4" db, or 3/4" hb, or larger (specify)

porty on base of tree - above same options.


I was in attendance at a seminar last week that was done by Ken Palmer. He was saying that if you are using a 5/8" lowering line, use the same size (5/8") for your block and step up at least one size (3/4) for the porty.

In talking w/ Splicer Nick, he (and I tend to agree) said he thought it best to step up both the block and porty to the same size.

We'd like to know your opinions.

My thought is that the sling at the top should be the bigger one, since the top sees a theoretical double load.

I'm thinking the portawrap sling could be the same as the rigging line, or slightly bigger.

The Block has 2 legs of pull on it; the Porty and Load positions only have 1. Everything being equal/unbuffered/ Zer0 friction; the Porty and Load connections take equal force. Any friction in between and the Load connection takes more Loading than the Porty connection. That is for lowering and holding; if lifting or pretightening by pulling Porty with truck; that re-versus to Porty having more force on it when friction in system.

Zer0 friction; and closed angle on legs to pulley/block will give 2x loading to it. Increasing friction and/or more open angle on legs of pull on block/pulley will give 1xLoad<block loading<2xLoad.

Therefore IMLHO; the Porty connection generally takes the least force of all 3 positions, but all ways less than the pivot of the block/pulley position.
A good rule of thumb is to have your rope be the weakest link in your rigging system. That does not mean skimp on SWL on your rigging line. Of choices you gave, I would go with the 3/4" Tenex. Its more than satisfactory for the setup you describe, and it seems to me that I get more life out of Tenex slings than double braid.
Adding if things were unequal in the setup; then he might be write. Like if the attachmeant of the block was in basket formation to a krab/block; then that would be 2 1/2x strength of same in choke(for unleveraged basket) and 2x line strength. So block in basket vs. Porty in choke might tilt model some. Especially if the block attachmeant was taking inline forces and the Porty attachmeant was taking forces leveraged across it's bindings(as it usually is). Like if block is on horizontal support, and the Porty on vertical; the block sling would more likely take inline forces; and the Porty sling perpendicular. Also, the block would take less than 2x with lines spread to wider teepee.

i wasn't there; just trying to give Mr. Palmer every benefit of the doubt..
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Thanks for the replies.

I email arbormaster last night and got a reply to day from Ken.

He said to use a 3/4" on the block and a 5/8" on the porty.
Yep, the block will be holding 2x as much as the porty. However, if your block is 5/8" capacity, then a 3/4" sling obviously won't fit in it. Go with the biggest diamter Tenex sling your block will accept (Tenex is stronger than double braid lines) and one size down from that for your porty.

I like to use whoopie or loopie slings for attaching the block. They go on and come off quicker than eye slings because you don't have to tie any knots. I use eye slings for the porty though because they work on very large as well as very small diameters.
Tenex can also lay flatter; so gives less height/leverage against line on the bent axis; to preserve more of it's higher strength.
speaking of Tenex. Yes it is strong, but I have problems with the low melting point. Too often just the friction of a girth hitch has melted spots on various slings.
I know guys use them for climbing hitch prussiks, but I just dont use tenex slings or prussiks anymore.

Better to use something with a cover on it IMO.