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Chair enlightening – 13 oz full chair


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Viewing 25 posts - 1 through 25 (of 59 total)
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  • #3811498
    Brian T
    BPL Member

    @whynotlighter

    I am a long time fan of ultralight camp chairs (REI Flexlite Air, Helinox Chair Zero) I think it’s a huge quality of life upgrade over a little pad, or a crazy creek or something along those lines that I have used before. something that has always bugged me about these chairs is that they stopped pretty far from optimal in terms of weight. So I took to improving mine.

    I started with an REI flex Lite Air, which started as 17.2 oz 491g (with the storage sack)

    The sack is now dyneema, which cut it down to 6g

    the poles were next, which I replaced with carbon fiber.

    Last I replaced the upper shock cords with lighter, thinner shock cord.

    All in, I saved 113g which is close to 25%.

    rear view

    Front View

    On the gram scale

    There is more room for optimization too. What do y’all think of this project?

    #3811500
    MJ H
    BPL Member

    @mjh

    Very nice. Do you think the chair will hold the same weight?

    #3811501
    Brian T
    BPL Member

    @whynotlighter

    It holds my weight no problem. I’m pretty light 175 lbs, I had a friend 190 try it out. It seems perfectly durable in its current form.

    #3811505
    Kevin Babione
    BPL Member

    @kbabione

    Locale: Pennsylvania

    Very nice – that’s a great weight savings.  Thanks for sharing!

    #3811511
    Stephen Seeber
    BPL Member

    @crashedagain

    That sounds great. Can you provide some guidance for those of us who have no experience with carbon fiber?  You know, imitation is the greatest form of flattery.

    #3811515
    dirtbag
    BPL Member

    @dirtbaghiker

    Ditch the sack, save 6 grams and another item not to have to worry about or store or look for.  I usually just wrap the legs with the seat and either put it in side pocket or outside mesh.. Depends what my load is and how I packed.

    #3811518
    Brian T
    BPL Member

    @whynotlighter

    @stevenseeber

    100%. There are a few clever things I did from a carbon fiber perspective here, but here is the basics you can start with:
    you can buy dimensional carbon fiber tubes from a lot of suppliers. The quality and dimensional accuracy will vary. Some providers are very good, but tend to be expensive, if you order carbon from amazon, you might have high dimensional variation. (composites are inherently hard to make perfectly dimensionally accurate). For a project like this you have 2 primary concerns about the carbon you select:

    1. dimensional accuracy. You want the carbon to fit into the joints of your chair, and the cord locks, etc, but most importantly you;re going to need a coupling for the long poles (this is where dimensional accuracy needs to be excellent)
    2. strength/weight ratio. There are 3 major influences to this ratio. a. what the carbon is made from (all carbon is a combination of the actual carbon and epoxy, this comes in varying ratios, and this determines some of it’s properties) b. Layup design (how the fibers are oriented, like wood determines against what forces it will be strongest) c. How the carbon is formed (depending on how pressurized the contents are during curing and what method was used to make the tube will have an influence – e.g. pulltruded tubes are different from roll wraped are different from filament wound.)

    ⬆ this is all just meant to explain some of what using carbon in a project adds in terms of complication, but I don’t want to make it sound harder than it has to be.

    In simple terms, all you need to do is find a tube you think will work, that actually is lighter than the DAC featherlight it comes with and do a swap out of the tubes (I also swapped the shock cord on some tubes for something lighter, and have some more ideas on how I can lighten it up further.

    The hardest part would be engineering the coupling if you want the packed dimensions of your chair to remain the same (the long tubes could be one pice which would be about 5g lighter, but would double the packed length of the chair). In my case I chose to have the coupling on the outside of the long tubes (rather than internal as the original poles were designed). I did this for strength. (note – for the same material and wall thickness, increasing the diameter of a tube by just 20% will double it’s stiffness). So by having the coupling slide over the outside of the tube it is much stronger than the original design (a concern when cutting weight)

    You could further cut weight by shortening the legs of the chair, if you’re okay with that comfort and stability compromise.

    Let me know if I am answering your questions. If you want to purchase some carbon tubes to play around with Rock West Composites makes extremely dimensionally accurate tubes with all kinds of different layups and characteristics, diameters and thicknesses. https://www.rockwestcomposites.com/tubing/round-tubing/round-carbon-fiber-tubing

    Also, if people are interested, I could make these into kits for folks.

     

    #3811519
    Brian T
    BPL Member

    @whynotlighter

    Dirtbag, I actually tried just using a tiny velcro strap to hold it together, so it wouldn’t get tangled up and would slide easily into and out of my pack, but it was harder to use, and didn’t save much in weight (about 3g) so the sack is a good compromise for me, but a lot of people (I think) would say less is more, leave the sack at home.

    #3811520
    Monte Masterson
    BPL Member

    @septimius

    Locale: Southern Indiana

    I could make these into kits for folks.”

    How about selling completed modified chairs? Of course you’ll need to do some field testing to see if everything holds up, but if the lighter mods appear to be solid I think there would be a market for them. A 3 to 4 oz drop is something a lot of people would pay for.

    #3811521
    Stephen Seeber
    BPL Member

    @crashedagain

    I like Monte’s idea. Depending on cost, I could go either way.

    #3811522
    Jon Fong / Flat Cat Gear
    BPL Member

    @jonfong

    Locale: FLAT CAT GEAR

    Or you could sell the idea/prototype to for cash to REI.

    #3811524
    Brian T
    BPL Member

    @whynotlighter

    Monte,

    I absolutely could do such a thing, however I might run into problems with patent issues. I looked into the options because there is further optimization to be had in the plastic bits and seat fabric potentially. However both REI and helinox have some patent protection on their designs. I can probably purchase their chairs and do the mods then sell them as a mod, but it would be pretty expensive and I suspect most of us already have one of these chairs.

     

    I could certainly make 10 modded chairs and 10 kits to diy and see what people are excited about. I started the project simply to see what I could accomplish here, but I’m pretty interested in making more of the demand is there, I love making cool stuff people get excited about.

    #3811525
    Stephen Seeber
    BPL Member

    @crashedagain

    Entrepreneurial spirit lives on at Backpacking Light

    #3811526
    Brian T
    BPL Member

    @whynotlighter

    lol Stephen.
    Not sure that’s what I’m hoping for, but the thought did cross my mind. I have a regular job I like a lot. But I get a big kick out of making cool stuff for other people, especially if they use it in doing something cool.

    #3811529
    Stephen Seeber
    BPL Member

    @crashedagain

    Well don’t quit your job yet, but this might be a fun side hustle.

    #3811580
    jscott
    BPL Member

    @book

    Locale: Northern California

    Still too heavy for me. Abd too close to the ground. There’s a hammock  style chair that hangs between trees that tempted me in the past. Much lighter and more comfortable.

    I don’t mean to disparage your fine work! for many this chair is just the ticket.  Kudos.

    #3811592
    Brian T
    BPL Member

    @whynotlighter

    Jscott, do you have a link to the hammock chair you mentioned? I’m curious to see the design.

    #3811642
    Link .
    BPL Member

    @annapurna

    I don’t know the one Jscott is referring to but here a couple you can look at Bushman Hammock Chair and a review Bushman Hammock Chair — review  and DUTCHWARE GEAR HAMMOCK CHAIRS .

    #3811643
    Monte Masterson
    BPL Member

    @septimius

    Locale: Southern Indiana

    Again, I think the modified Flexlite Air would need to be field tested quite a bit before marketing. Carbon poles probably won’t stand up to the maximum weight of stock aluminum, but if it could be rated to say 195 lbs max that would cover the majority of backpackers.

    I would then produce a small run of the modified chairs and start off charging enough to make it worth your while. Even if its $200 or more there are a number of UL hikers who would be wiling to pay for a lighter Flexlite, especially if its proven durable over time (Nemo Moonlite Elite is $180). I’ve been considering a Chair Zero for quite awhile but the weight (1 lb) is just a bit too much. A 13 oz Flexlite however would be tempting.

    I see REI has the Flexlite Air marked down to $70 until May 27. Might be a good time to grab up a few. https://www.rei.com/product/148036/rei-co-op-flexlite-air-chair

    #3811651
    Brian T
    BPL Member

    @whynotlighter

    Thanks Link – those chairs are interesting, essentially no structure, just the tension of the support lines and your body to give it shape. Clever, light, and probably confortable. (I suppose you need trees, and it might be hot (kinda cocooned in there)

    Monte,
    I agree with you 100%. I’ll pick up some discounted chairs to make a run of them. I also will do some destructive testing on this one I have made (although it’s a prototype, and a production run might get some changes.

    FWIW carbon is actually stronger than aluminum in most cases (2-5x the strength to weight ratio) so being 25% lighter, I’d bet this is actually stronger in an absolute sense. The trick is that it’s not as crush resistant, so if the angle puts the wrong cross load on it, it will fail.
    I’ve been using it as a chair for a couple weeks so far, but I only weigh 175. It feels stiffer to me than the aluminum version. I will put some weights in it to see what causes it to fail. I am also going to make a version from the Helinox, as well as experiment with new seat skin materials (although the flex lite air is very thin, this is where it saves 1.5 oz over the Helinox). I also think there is room to optimize the feet at the bottom and perhaps remove some material from the plastic connections to cut a few more grams. I’ll keep posting progress as I learn more.

    Thanks for all the support on this idea, really appreciate everyone’s thoughts, this is very fun. Glad to be a part of the community.

    #3811653
    Brian T
    BPL Member

    @whynotlighter

    One design question:
    how much shorter could the chair be before it was useless? ( shortening the legs would cut some weight, despite also making it a bit less stable)

     

    #3811655
    Jon Fong / Flat Cat Gear
    BPL Member

    @jonfong

    Locale: FLAT CAT GEAR

    Sounds like an ergonomic question/trade-off.  There are probably a lot of variables involved: gender, age, height, weight and so forth.

    #3811768
    Paul McLaughlin
    BPL Member

    @paul-1

    Nice work. I have a couple of these and have thought about making a new fabric seat partly to save weight but mostly because I would like a mesh seat for warm days. Seems like the seat is your next step also. I was thinking maybe the monolite stuff that ripstopbytheroll has, I think that is the lightest non-stretch mesh that is readily available. Whether the lighter of their two versions would still be strong enough would be the question – although either is going to be lighter than the fabric the seats are made of –  as well as reinforcing details for the pole pockets at the corners.

    #3811769
    Paul McLaughlin
    BPL Member

    @paul-1

    And as for shortening the legs, I think the loss of stability that you would have due to a narrower base makes that not worth it.

    #3811789
    Chris L
    BPL Member

    @thechrislundy

    Locale: Idaho

    200 pound Helinox Zero user here if you need a tester 😃

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