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wood layer layup orientation for strength?

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Forum topic by jimmy J posted 11-03-2016 06:03 PM 957 views 0 times favorited 8 replies Add to Favorites Watch
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jimmy J

229 posts in 2213 days


11-03-2016 06:03 PM

I’m interested in making my own wood handled ice axe – not to scale vertical mountains with, but more of a vanity axe for use while mountaineering in the winter. needs to be strong but won’t be use as a life saving device.

The pick is steel and has a neck that extends down ~6” into the wooden handle. i believe this will transfer most stresses from the pick into the wood handle. in the attached pic, the orange/yellow part is to be wood.
Rather than one piece of wood sandwiching the pick, I am thinking of laminating several pieces of wood together, hopefully adding more strength.

overall it will be about 0.9” thick and the pick neck is 0.15”, so about 3/8 of wood on either side. this 3/8 would be 2 layers, so about 3/16 each. will use West Systems epoxy

thoughts on grain direction for the layup?

https://s3.amazonaws.com/vs-lumberjocks.com/og2v2ed.jpg!


8 replies so far

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clin

751 posts in 830 days


#1 posted 11-03-2016 06:45 PM

I have no experience with ice axes, but the thickness you suggest seems too thin for wood. Looking online, the equivalent to the one you pictured is made with an aluminum handle. For the same size, aluminum is stronger.

That said, splitting where the steel attaches is the most likely failure. Typical axes, sledges, hammers, have the wooden handle fit inside the metal so the forces are not trying to split the wood.

I would want layers of wood grain running across each other. Like plywood. Though perhaps not at 90 degrees given the boomerang shape of the handle. Alternatively some sort of band around the handle to keep it from splitting.

The Petzl ice axe seems to have a rivet running through the handle to bind things together. That’s certainly going to help hold the wood together. The larger the head of that rivet the better.

You might even consider putting a layer of fiberglass over the wood handle. With the right kind of clear epoxy, this can make for a nice finish.

Also, consider using composites internally. Instead of running wood cross grain, run some Kevlar. That way you can leave the bulk of the wood running in the primary direction needed for strength. The Kevlar would be very thin. But for it to help, it needs to be near the outside, it will mostly strengthen the wood that is between it and the steel.

Another option ,might be to make it with an aluminum core and put wood sides on it for looks. Like a knife commonly does.

-- Clin

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jimmy J

229 posts in 2213 days


#2 posted 11-03-2016 11:59 PM

Thanks Clin. All good comments. I’m confident the pick will stay attached to the handle with epoxy, and the stresses will transfer to the handle. It’s the bend of the handle that worries me. I don’t need it as strong as the standard axe, which is aluminum tube as you note.

View Woodbum's profile

Woodbum

798 posts in 2900 days


#3 posted 11-04-2016 12:38 PM

I’m not a true mountaineer (armchair one), but why would you carry an ice ax/tool that could not be used for a life saving arrest in case of a fall? Extra weight and extra gear to get in the way. It IS a rather interesting looking ice tool in the pic. Just a question from an old woodworker that spent a lot of time hiking and backpacking.

-- "Now I'm just another old guy wearing funny clothes"

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clin

751 posts in 830 days


#4 posted 11-04-2016 04:00 PM



Thanks Clin. All good comments. I m confident the pick will stay attached to the handle with epoxy, and the stresses will transfer to the handle. It s the bend of the handle that worries me. I don t need it as strong as the standard axe, which is aluminum tube as you note.

- jimmyhopps

My concern is not that you can get a firm attachment. And the stresses will transfer to the handle, because they have no where else to go. I’m just concerned that with about 3/8” of material on each side of the steel, it would be likely to split without some sort of reinforcement.

Concerning the bend, as mentioned earlier, a plywood construction or embedded composite materials will handle that. Another option would be a finger joint. Joining two pieces at the bend, each with primary grain running the length of the sections.

You could make this joint by laminating contrasting woods, rather than cutting the finger joint. Might be an interesting look.

-- Clin

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jimmy J

229 posts in 2213 days


#5 posted 11-04-2016 05:04 PM

Thanks again Clin

Woodbum, where I winter hike there are lots of ice slicks. I’ve climbed/hiked up them all without an axe and it’s a lot easier with one. I don’t want it to break on me, but if it does, it wouldn’t be the end of the world. And with axe, I get to skip the ski pole I otherwise would carry. I do own an aluminum straight handled axe, but want the cooler looking technical axe. All vanity. And since I like to woodwork and can buy a pick head for $50 and make the shaft rather than buying a technical axe for $200, I figure why not. Furnace Industries actually sells a technically rated wood ice axe – some sort of special plywood. So I know it’s possible.

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Rick_M

10607 posts in 2214 days


#6 posted 11-05-2016 05:07 AM

Wood is strongest parallel to the grain. Clin makes good points and assuming you can connect the head sufficiently the only way to make a strong handle in that shape is by either use a tree branch that has grown in that shape or using bent laminations to make a continuous grain handle.

-- http://thewoodknack.blogspot.com/

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clin

751 posts in 830 days


#7 posted 11-05-2016 10:48 PM



... or using bent laminations to make a continuous grain handle.

- Rick M.

Rick, you nailed it. This ^^^ is a great idea. This gives you an extremely strong “bend” in the handle. There are chairs made this way.

-- Clin

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JBrow

1273 posts in 754 days


#8 posted 11-06-2016 01:21 AM

jimmyhopps,

I think a good choice for a wooden handle would be knot-free hickory. Using a frow or a hatchet and hammer, the hickory could be split to the approximate size. Splitting the hickory rather than ripping would preserve the wood fibers from one end of the work piece to the other making the hickory very strong and resistant to breaking.

Once the rough size is obtained, it could be steam bent. Ensuring the grow rings of the hickory will end up parallel to the blade of the ax after bending would probably add some additional strength. After it is steam bent, the handle could be smoothed and made comfortable to the hand.

While some of those fibers running from one end to other may be broken as the rough handle is shaped, the broken fibers will be on the surface, leaving deeper fibers intact.

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