In my imagery;
1/3rd fair starting point to evaluate hinge placement mechnaix allowed.
>>not so much about face you are taking, but positions you leave behind to focus on.
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Less than 1/3rd can push loading to outer rings only and peel down side towards more of barberchair as Daniel says;
We want the 'whole welded mass' of tree (or close to/not just outer rings) supporting our hinging;
we want a wider / less loaded per inch support base of hinge/ not focusing all loading to more of a high pressure point like faceless fall.
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In many trees, 1/3rd back for facecut would place hinge at or right before tree center/widest positions;
this would allow tapered hinge most leveraged 'backfield fibers' to extend from about widest part of tree for most side to side control.
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On the other side of project, 1/3rd face helps to maintain fair face slap deck;
less face might eliminate this effect, clean tearoff etc.
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Hard forward leaners, might come forward with hinge, to move pivot of compressed part of hinge closer for some less lean angle to this pivot.
Shallow lean might come back more to undermine center of gravity more/ give more lean angle to compressed part of hinge as pivot.
Back leaners, would come back even further, but lots less side to side control
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In standard mechanix of movement, the saying 'a pivotal change' is very apt.
For pivot position change is compound action in 1 move,
can take leverage away form load and give more leverage to support side at same time (or vice/reversa).
>>returning high impacting immediate changes in mechanix.
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1/3rd back would tend to not allow/cast hinge center into center of tree;
avoiding any heartwood less flex-ability concerns.
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Evaluating of hinge fibers AND face slaps positions verifying good wood for mechanix is essential.
i think it is also logical and witnessed/tho hard to sift out;
That colder or deader wood can give good face slap mechanix, but less flexability on hinge.
Greener, outer wood, perhaps opposite...
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From 1/3rd face position, if not hard forward lean/list ;
would generally not want to go less facecut;
but ; have left room to go for deeper face, and might want to..
>> after re-evaluating what fibers are asking to do what function, after tree 'cracked open' w/facecut