Hinge Thickness For Falling Large Diameter Trees?

[SteveSr]

Hello,

Happy Thanksgiving everyone! Here is an interesting question to ponder over turkey and football.

The Forest Service guidelines specify a falling hinge thickness of 10% DBH as a maximum. The 10% number works out pretty good for trees under 20" or so. But what about a 48" tree? 10% is 5 inches which sounds like a near impossibility to wedge over, especially if the tree is dead and has no lean or weight. Think about trying to break a true to life 5" x 48" piece of wood. Think about a huge dead, dry piece of red oak.

Here is the situation: The tree in the photo is right next to a hiking trail and has been dropping widow maker limbs onto the trail. Due to this the trail section monitor has asked me to evaluate the safe removal of this tree. The tree was supposedly alive a couple of years ago until the town put a sewer line in the vicinity of the tree and damaged the root system.

As a disclaimer I have not laid eyes or hands on the tree as of yet. I do have it on good authority that the DBH was actually measured at a little over 48". The diameter tape was only 12 foot and that was the end of the tape!

For mitigating resources/measures we have access to rope rigging and a Tu-17 Griphoist so this could belay having to wedge the tree over.

Your thoughts?

 

[SteveSr]

Website won't take photos... Will try again later.

 

[Marley5]

48" is absolutely massive

 

[buzz sawyer]

I agree, 4.8" is a lot but 10% is maximum as stated, not minimum. I would take into consideration the quality of the wood and the amount of lean and how much weight is in the top.

 

[J D]

Well... I haven't cut oak (or any deadwood that big)... but for redwood & cypress around that size I would generally have a hinge around 3" thick... sometimes with the center bored out

 

[ZeroJunk]

And, here I was thinking it was 1/3 . Unless it was leaning too much. I dropped a 48 inch white oak a couple of years ago. Notched it about 1/3 and knocked it out with a sledge hammer. Went without incident.

 

[SteveSr]

I just added the photo... No Server Error this time!

 

[ZeroJunk]

I'm confused. Hinge thickness, notch depth ?

So, you are cutting to a certain hinge width and doing the rest of the work with a wedge.

That tree would scare me. I have several red oaks here in that shape that I won't touch.

Particularly not start banging on it.

 

[PV Hiker]

Could be a lot going on inside that tree. Limbs fall on their own and if chainsaw causing vibration could send another limb down. Risk factor of safety.

You'll have to visit the site to see and sound the tree to evaluate if there is holding wood or rotted out around the trunk base.

Looks like in the picture there is some weight to the side falling toward the open field. Is that fence in the drop zone?

Using a grip hoist might be better than banging on a wedge sending upper limbs down. Rig the grip hoist with redirect to not put the operator in the fall zone (dead tree and limbs shatter and fly many directions). If using pulling aid, consider using a bore cut behind the hinge just as you would felling a heavy leaner as the tension on the line is pulling the same.

There is more going on than just thinking about cutting face cut and setting hinge depth, a field trip is always best and evaluate from there. Good luck.
Patrick

 

[SteveSr]

I'm confused. Hinge thickness, notch depth ?

Hinge thickness is actually the fiber that gets bent over.

The notch depth sets the length of the hinge. USFS says >80% of DBH.

So, you are cutting to a certain hinge width and doing the rest of the work with a wedge.

Wedge(s) would be one possibility and if we get that far we might try that. However, we also have access to rigging (TU-17 griphoist) as a backup plan.

That tree would scare me. I have several red oaks here in that shape that I won't touch.

That is why I NEVER say that I am going to remove a tree and I am only there to evaluate if the tree can be removed safely.

I live in an older neighborhood and have seen several considerably smaller red oaks come down due to rot at the base. I will be checking this one carefully for this defect.

Particularly not start banging on it.

My plan is to use the attached rigging from a safe distance to shake the top of the tree to see if any more of the top is ready to fall. This should get rid of any widow makers.

 

[rwoods]

Only an armchair call from a firewood hack looking at a picture, so please don’t take offense. This tree is one you confront with plenty of experience. With all due respect, if you have no experience in felling large dead oaks, I seriously doubt you should be advising whether the tree can be safely felled, particularly, since what is safe depends heavily upon the felling method chosen and the skill, experience and judgment of the one behind the saw.

In my opinion, the one cutting this tree should be experienced and confident enough to size the situation. If not, he shouldn’t be cutting the tree without the direct supervision of someone who is. If the cutter is only seeking an opinion, ideally, it should come from one who has been there and done that many times.

Pulling on the tree to shake out widow-makers is not fail-safe as it can increase the risk of a widow-maker.

Ron

 

[J D]

@Kodiak Kid might have some valid input.
If dead oak has a tendency for the roots to rot & its looking compramised at the base I'd be putting a decent wire rope through that fork & pulling on it from a safe distance with the biggest machine I could get my hands on. What's the access to the area like?