largy porty vs. medium porty

[GoodYautja]

I just realized they are rated the same (2000 wll). I assume because of the smaller diameter of the medium porty that extra wraps will be needed to maintain the same amount of friction as would be had on a large porty.

can anyone tell me the approx. difference, assuming the same size wood? i'm guessing an extra half-wrap to make up the diff...

 

[southsoundtree]

max rope diameter 9/16 vs. 3/4 is another difference.

 

[grappleyarder]

The Capstan equation is theoretically independent of the device diameter. Friction is created by force over a given area (pressure). Seems a little counter intuitive but the larger diameter capstan adds more contact area which reduces the unit pressure therefore reducing the unit friction. Easier on the rope but the same holding force per angle of rotation around the bollard.

What are peoples infield observations?

 

[born2climb]

The medium is great for in-tree usage when you have only 1 groundie. I have used mine aloft several times. It does take more wraps, and heats up quicker than a large. I like using it alone up top....no block. Simply rig the porty in a good spot above the target limb, and usually 3 wraps, just cut and the piece will float to the ground. The weight of the rope will tend it. You have to match number of wraps to weight of piece, of course.

I do not like the medium for use on the ground, however. I prefer the large one for more control.

 

[GoodYautja]

grappleyarder, that's wild. I suppose it sort of makes sense with regards to the tighter angles around the smaller diameter... a 'flatter' surface would yield less friction, is that what that equation is about?

born2climb, that's even wilder. invisible groundies... what will they think of next! i'm not quite ready for that rig, but i look forward to the day.

thanks, i still can't decide but at least i know more.