Wood backpack

[Luke Hospadaruk]

Because I like to try and make everything I use, I got it in my head to try and make a wood-framed camping backpack. I'm aware of old-style packframes, but those are too heavy duty for me.

Turns out in the 70's some guy/company in oregon made just the pack I want to make, the Segen Pax.
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I believe the frame is made out of white ash.

I have a couple questions here mostly regarding what kind of wood to use.

I have some nice green white oak I recently acquired for steam bending on a kayak I'm building, if I can use that I'd like to. I'm imagining laminating 3 1/4"x3/4" strips for the vertical and some 1/4"x1-1/2" strips for the horizontals. Probably steam bent to some kind of jig.

My major questions with the oak are:
1) what to use to glue the oak - I imagine some kind of polyurethane glue would work well since the wood is pretty wet.
2) Can I expect the wood to warp significantly as it dries over time - even if everything is laminated?
3) should I just use a different wood alltogether? I have a couple good small sawmills nearby and I can get just about any variety of kiln-dried, air-dried, or green white oak or white ash (or whatever other kind of wood). I'd like to use the oak just because I already have some surplus, but it's not a big hassle for me to get a different species.

Thanks in advance! - I love the forum, I could read about people's projects all day long.

[Jamie Buxton]

I'm confused. You mention both lamination and steam bending. Generally, when folks say lamination in the bending context, it means slicing the wood into thin layers, slathering them with glue, bending the stack over a form, and waiting for the glue to dry. There's no steam involved. Most often, the wood is dry, not green. In contrast, steam bending means steaming the solid wood, bending it over a form, and waiting for the wood to cool down. There's no glue involved. Steam bending is ideally done with wood that was not kiln dried; air-dried is generally recommended.

Green lumber, even green lumber that has been bent a bit, may warp and twist as it air-dries to its final dryness.

Both ash and white oak are good woods for bending -- either steam bending or bent lamination.

[Jamie Buxton]

Your photos are teensy, so I can't tell, but it seems like there's almost no curvature on the vertical pieces, and there's very little curvature on the horizontal pieces. You might could get away with just bandsawing the curves, and not messing with bending forms and such. If you don't get short cross-grain areas, the parts will still be sturdy.

[Prashun Patel]

If it were me, I'd use dry wood, saw it into 1/8" slices, and laminate it with polyurethane glue. No steam, just clamp it to a bending jig b4 the glue sets.

I'd also use a lighter wood than ash or oak; but I have a bad back. I wonder if cedar would be strong enough and if it would glue well in lamination? But it certainly gets high marks for weight and weatherability.

[John TenEyck]

There's a reason that company is no longer around. In fact, there's a reason you hardly ever see an external frame pack of any kind anymore. Internal frame packs are just a lot more comfortable to carry. A few diehards still use their old external frame packs, but normally the only time I see them used is for hauling really heavy or bulky loads relatively short distances- like packing out an elk or something like that. If you want to try to build a pack, why not look at modern internal frame packs and figure out how to adapt their frames to wooden construction. Some would lend themselves to bent or laminated wood pieces and one potential advantage of wood is that you could customize the curvature for your spine and height. Personally, I'd use laminated carbon fiber if I was going to go to all that effort, but wood should work - it's just going to be heavier.

[Greg Portland]

My major questions with the oak are:
1) what to use to glue the oak - I imagine some kind of polyurethane glue would work well since the wood is pretty wet.
2) Can I expect the wood to warp significantly as it dries over time - even if everything is laminated?
3) should I just use a different wood alltogether? I have a couple good small sawmills nearby and I can get just about any variety of kiln-dried, air-dried, or green white oak or white ash (or whatever other kind of wood). I'd like to use the oak just because I already have some surplus, but it's not a big hassle for me to get a different species.Cool project! I would start with dry (not green) wood. For glue in exterior environments I am a big fan of 2-part epoxies (good stuff like West Systems, etc.).

Ash would be a good option because it takes a beating (dropping the pack on the ground, etc.). With the frame shown I wouldn't expect a ton of warpage plus you'd just need to adjust the straps slightly.

[Eric DeSilva]

I would seriously disagree with the idea that internal frame packs are more comfortable to carry. In my experience, for normal backpacking, an external frame pack is far more comfortable than an internal frame pack. There are applications--mountaineering, ski touring--where you need your center of gravity lower, but that comes at a cost, including a lot poorer ventilation. At some point in the backpacking scheme of things, internal frame packs somehow became "cooler" or something. That does not make them better.

[Rob Fisher]

I would seriously disagree with the idea that internal frame packs are more comfortable to carry. In my experience, for normal backpacking, an external frame pack is far more comfortable than an internal frame pack. There are applications--mountaineering, ski touring--where you need your center of gravity lower, but that comes at a cost, including a lot poorer ventilation. At some point in the backpacking scheme of things, internal frame packs somehow became "cooler" or something. That does not make them better.My personal opinion, and it has been a few years since I backpacked, is that it depends on whereyou are backpacking. When I did short distances on the AT I felt like an internal pack was more easily carried. Not exactly sure why, something to do with the hopping from rock to rock thing I think.

[Luke Hospadaruk]

Ok,
Edited the first post with the full size images - don't know what happened there.

Some thoughts -
As to the laminating/steam bending issue, I should clarify a little what the situation is:

I have some spare oak leftover which I'd like to use if possible, ordinarily I would probably just use thinner, dried wood and laminate it like a normal person. It's certainly not the ideal wood, but I don't really have any other use for it.

I have two types of white oak stock:
1/4"x3/4" strips
1-1/2"x1/4" strips

I don't really have the capability to resaw the oak into laminatable strips, and I'm not sure the quarter inch thick strips I have would bend tightly enough to shape without steaming. Whether I steam or not isn't a major concern, I'll see if I can get the bend without steaming and just hold it in place with the lamination, and if not, I'll steam. If I end up buying different wood, I'd just get it in thinner strips from the sawmill (1/8" probably) that could be easily laminated without steaming (so I could use fully dried wood and not worry).

There isn't a ton of bend in the verticals, but at the bottom around the waistband there's a moderately sharp bend outward so the bottom of the frame doesn't poke your butt.

As to the jointery between the verticals and the horizontals, it looks like the verticals probably have mortises cut into them, I'm thinking I'd just cut dadoes into the outer side of the verticals and fasten the horizontals with glue and a dowel or two.

I found a paper (http://teilar.academia.edu/GeorgeMantanis/Papers/114672/Green_gluing_of_oak_wood_Quercus_conferta_L._with_ a_one-component_polyurethane_adhesive) that seems to indicate green oak can be glued successfully with polyurethane glue, and I have to imagine a CA glue would work well too. My biggest concern is warpage/shrinkage, especially with the glue joints - would the glue joints overly inhibit natural shrinkage and cause cracking or excessive, unexpected warping?

I'll probably just go ahead and try it with the oak and see what happens. If it blows itself up I can always make another =)

[Luke Hospadaruk]

Also to the internal/external debate, I have an internal, I like it and it's my main backpack, but I'm a big dude and I like to carry lots of luxuries, so I've been thinking about going back to an external. I like the ventilation and the ease of being able to tie things onto the frame. It's also nice to be able to change out the entire pack (like for example strap a big drybag onto the frame for times when it's going to be super rainy or if I'm boating/hiking/portaging, etc).

I've used externals in the past and liked them, but it's hard to find ones that fit me well, and I feel silly buying a new anything when I might be able to at least have a try at making it first.

[Rod Sheridan]

Luke, if you have green white oak, steam bending will work great, just leave it in the form until it has dried a bit.

Regards, Rod.

[Jay Jolliffe]

To answer the statement about steam bending & lamination bending is, sometimes the wood won't bend to the radius without a little help from steam bending first with the same form that you will use to do the lamination bending only after the wood has dried from the steam. I know I did this. I made some side tables out of cherry & the legs were made from 1/8 x 1" strips & I needed to steam them first because they cracked. When you steam bend it doesn't always turn out the same if you have to do multiple pieces but when you lamination bend & epoxy it they will be all the same. I used Unibond 800 when I did it because the catalyst comes in different colors .

[Jim Matthews]

It looks like the back of a chair to me.
Some research into chair making (http://www.finewoodworking.com/PlansAndProjects/PlansAndProjectsPDF.aspx?id=2881) should get you started.

I would say that the key concerns are lateral strength balanced with wearing comfort.
The weaving across your back will be under some tension, and this will pull the side rails together.

I suspect they are flexible, to allow some give for the load to shift.

I would concentrate my efforts on getting the hip girdle right - the idea is to get the center of gravity low, while packing high.
Rather than try to bend the oak, why not go with additional webbing, as on a canoe seat?

Lastly, you might try carving the pieces to get close to your desired shape.

This is a worthy and interesting project, please post your progress!

jim
wpt, ma