No one wants a 40 liter 15 ounce framed pack right ?

I'm not going to get into the laminated balsa vs CF argument Mary, but I will say, it's inappropriate to state that carbon fiber won't conform to spaces that balsa will.

Carbon cloth, kevlar cloth, and glass fiber cloth, can be molded to much tighter tolerances than balsa can, highly intricate contours, and that's an indisputable fact. Also, the strength vs. weight statistics aren't black and white either, especially concerning the aforementioned contouring.

Balsa is used heavily in advanced composite(carbon, kevlar, texalium, glass fiber) lay-up, but there's a reason why it's not used exclusively, and it's not price related, since CF cloth is many times more expensive than balsa.

Ultra-thin veneers of laminated woods like balsa have a lot of potential, but they can be even further outside the realm of small scale production than composite layup, since to be competitive(by volume/weight), they can require industrial processes that are completely outside the realm of feasibility for a small shop.

Bear in mind, we're not talking about surf board thicknesses here. We're talking about 1/8 inch or less to be viable, and multiple layers are necessary to meet performance demands.

Javan, that just shows how much I _don't_ know about carbon fiber and the other materials you mention! All I know about is the straight stuff in my trekking poles, a tent pole and in the old Gossamer Gear Mariposa. (I still have one of those hanging around.) Thank you for the info about the various materials. It's people like you that are taking innovation a lot farther, and we need that! IMHO, it's the folk like you and the others coming up with new products who will be the true saviors of our economic system, not the big guys sending all their production overseas!

The one argument in favor of wood would be that when the pack gets lighter, there would be nice dry fuel available. :-)

"The bigger question, why would we need a SUL pack with stays? If you're SUL, you shouldn't need stays."

Then it's a super ultralight pack (in terms of pack weight) meant carrying above SUL loads.

"The bigger question, why would we need a SUL pack with stays? If you're SUL, you shouldn't need stays."

Then it's a super ultralight pack (in terms of pack weight) meant carrying above SUL loads.

Fair enough, go for it. I'll be surprised to see it carry the aforementioned loads by my definition of "comfort", but if it truly does, I'll be it's foremost proponent.

While the Kifaru UL packs aren't UL in terms as most people define here, Patrick uses wood/carbon fiber stays on this packs and they can comfortably carry tremendous amounts of weight.

http://kifaru.net/KU_suspension.html

Sorry if this is off topic.

Warren,

Heres a link to a discussion of my frame pack from the myog section of this website:

here

Daryl

I like that design. I might try something like that at some point. That may be the only practical way to make a SUL pack that could carry heavy duty loads. I do like the contoured fit of aluminuim stays so I might try a frame from Gossamer Gear at some point, its a tad heavier but I don't mind an ounce or two if I like the fit.
One question with yours. It looks like the weight lower than it normally would be on a traditional pack. Do you think it would carry better if you shifted it up a tad or is there a reason you made it that way?

MLD and Zpacks have packs using Klymit pads. I wonder how a pack using inflatable tubes as an integral part of their structure would work?
It seems like a nice idea to have an inflatable tube running down the sides of the pack, and curving into and around the hip-belt.

good conversation on the subject guys two points i have. One yes comfort is a personnel feeling and i can not define "your' comfort only mine. Two is i am marketing the pack for sul hikers doing either 1 longer hikes/ thru hikes or 2 in dry areas like my home turf N.M. any way here's the pics

"it's inappropriate to state that carbon fiber won't conform to spaces that balsa will."

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Pretty much just an FYI for those who wish to MYOG or hobbies or what not below:
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Yes/No. If using CF chopped fiber, then yes, its far easier than balsa on super complex 3d shape(backpack frames are NOT a complex 3d shape) as you make a mold and "mix-&-pour" in. Not quite as strong, but still pretty darned good stuff. I take all of my CF fiber scraps and chop them up for use in such "blob" molded parts. Likewise achieving a smooth CF part is rather arduous work. In the end its also a heavier part. If you need the Specific strength and high tensile/compressive stresses then its mighty good stuff.

Working with cloth on flat thin surfaces is fairly easy and quick. So, in this aspect CF is almost as quick as wood. Anytime you go 3d or have to build up corners in small areas, cloth of any-type stinks.

Wood on the other hand can easily be shaped/modified/clamped/glued using far fewer specialized tools that are more readily available to the common Jack and Jill.

Wood is always faster for prototyping in all aspects. Wood is always faster for 1 or 2 'offs'. If you are setting up a production facility then investment in molds will pay back in time savings. Otherwise Wood is always a faster medium to work with. It also does not cause as many health problems when working with its dust than epoxies. In the end wood workers will have just as many health problems as those in handling epoxy products. Difference is Epoxy is dense and therefore and cutting 'smoke' is 'lighter' and easier to suck away than wood dust.

Either wood or epoxy work has aspects that cause harm to the workers. Something to think about if one is going to be working with these materials over an extended period. Lung/Nasal problems. Asthma, Allergies, Rashes, Hives, etc.

Making a tube out of wood is next to impossible on the other hand. Best lightest option generally speaking for carrying weight and rigidity is a hollow tube. Differences with high grade balsa is that its so light structures don't need to be hollow to achieve the same strength. Making a curved beam out of balsa is also fairly easy and VERY quick. Knife/glue, template/drawing, BAM done, install, check it out 10 minutes later. Will take longer making the template/drawing than actually making the part.

High grade balsa 4-6lb/cubic foot is actually MORE expensive than Carbon Fiber on a weight and on a volume basis. Cheap, read; dense/Heavy Balsawood is not as expensive as carbon fiber and is readily available as its used as shipping container wood from SA.

Creating joints with balsa does take some experience. Have to transition between a low tensile material to a high tensile high strength high density material. Quite often one needs to put transitionairy medium tensile materials between say, Super light Balsawood and Dense CF. A quick way is to very simply put glue(CA) on it as it is a super low viscosity glue and wicks into the BW quite readily. So readily in fact that the material SMOKES and if you touch it while it is curing will burn you and thoroughly stick your finger to said material.

PS: My background in composites is mainly in competitive airplane construction. Likewise I have been worked for Boeing in wind design on 787 Dreamliner with a bit of work in kayak construction as well. I have been building/designing RC competition airplanes for near 20 years. Won several. Everything from high lift SAE heavy lifters to Pylon speed racers and sail planes. For instance our SAE plane lifted 25lbs and weighed all of 1.3lbs(structural) with a tolerance for +3g maneuvers. My brother(pilot) still managed to pull a 5.5g(from video) turn at which point the 1/32" balsa wing and carbon fiber spars exploded on the right side turning the entire airplane into so much confetti in the air drifting over the airfield for the next 2 minutes and the 25lb weight went augering into the concrete taxi-way. Thankfully no one was hurt even though said weight went flying through the safety barrier for 10 feet smashing into a trailer.

PPS. Made a "cup" out of laminated balsawood to save weight. Yes, I saved weight, but can't heat said cup over a flame so it was essentially a non starter and useless. On the flip side it insulated the hot coca far longer than my TI or AL cups. It even held up to the 'sit' on and squish test. Not sideways though. Then again an AL/TI cup won't hold up to a sideways test either.

I like the overall look of that pack. Is there any padding between the frame and your back? That would seem necessary for a commercial design since everyone is different and someone is bound to have it poking their shoulderblades.
I like the hipbelt attached near the center so it wraps around the hips better.

yes the final model will have a pad sheet of 3/8 inch foam. however the frame is designed to avoid pressure contact with your body, and it does this pretty darn well

Luke,

The back bag's position on the frame is adjustable. My wife and I like it low. My tall friend likes his high.

I don't have any explanation other than personal preference. When I was younger I liked my load high. Go figure.

Daryl

William,

Nice looking pack.

I like the obvious attention to detail.

Daryl

I believe the reason is that when young your balance was better with a higher CG(Center of Gravity). Even though the CG was higher it allowed you to walk more upright as you did not have to lean as far forward to counter balance the weight.

Think of it this way: Heavy Dense items are/should always be carried as close to your back as possible. To counter said "backwards pull" you have to lean forward less to counter said items. Now if said heavy dense items are higher up on your back, when you lean forward you bring their mass closer above your feet/hips as that is your true balance point in regards to how much one must lean "forward" to counter said weight.

Of course all those heavy dense items when carried at the top of your pack like to make squished pancakes out of everything(light fluffy stuff) at the base of your pack… So, much for that fresh bread and whole cookies that just got turned into a packed sawdust log and crumbs.

I would gather you like yours low because you have a front pack now requiring you to bend forward far less. Likewise I have found that the speed at which I walk determines how far forward I "lean". Slower, I lean less. Faster, I lean more. Introduced trekking poles into the equation to lean forward weight onto?

<< Muddies the water probably >>

Brian,

Thanks for the perspective. Makes sense to me.

Daryl

Many years ago I prototyped a T shaped frame. It seemed to work well but never took it any further. I am interested to hear of any other efforts of the T shaped frame.

My logic (no doubt flawed) is that packs are basically a tube and when we fill them their tendency is take a circular horizontal cross section. What we really want is to make them a rectangular box section. This can be tackled in three ways, control the shape and thickness of the pack on the vertical central plane (the aim of the T frame), push the sides apart so it cannot achieve a tubular shape, or fill the pack with rigid containers of the correct shape. The second is the aim of most frames. The first method is seen in a coupe of old designs which had a vertical central divider which basically turned a single tube into two tubes, keeping the pack more slender and so better weight distribution. The divider between the top and bottom compartment in some packs also has some similar benefits as does the top of panel loading packs.

The base of the pack achieves this by its rectangular shape while the hip belt pulls the sides of the pack apart so the issue become controlling the pack shape towards the top of the pack. While the shoulder straps have some effect, they are not at the outer edges of the pack and there is no rigid piece of fabric at the top of a top loader. A single strap closure does have a positive effect.

Most frames have a horizontal cross bar and two vertical bars at either end. MY idea is to use a single centrally located vertical bar attached to the horizontal cross bar. This should be lighter as there is only one vertical bar. It also may improve carrying comfort by allowing a pivoting hip belt (subject of a recent thread) to be connected to the frame.

I also plan to have a removable cord connection between a vertical rod on the front of the pack and the vertical frame bar to help control shape and volume. Rather than cut the sides of the pack as rectangles I have contoured them to follow the curves of my back.

I am just about to order some CF tape and resin to build a shaped T frame. I am hoping the CF vertical bar will have sufficient flex to work with the body. A Christmas project.

Meh, Twin 7075 alum. stays are still the best way to go. But, instead of plugging them in behind your back, you spread them wider apart, more to the sides of your back. Add load lifter straps directly where the stays end, and you have excellent load transfer.