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Thread: SHig's Superlight Packin'tube Project

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  1. #1
    Join Date
    Sep 2008
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    Citrus Heights, CA
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    1,514

    Default SHig's Superlight Packin'tube Project

    Okay, first off, no, I haven't yet built my pram. It's still in the works, but on the back burner for now.

    So what's new? Backcountry hike-in fishing! I gave in and tried it and found that I really like it! Best off, there are LAKES in the mountains, and I love fishing lakes, and most of all I love fishing from a float tube.

    So what's a boy to do? My FishCat IV DX weighs a healthy 14 lbs and when fully deflated and folded is the size of a 2200 in^3 pack! Luckily, I was able to snag a Del Canty Lunker Hunter tube which fits the bill for packing (mostly). 3 lbs, bladderless coated fabric, packs small (about the size of a pair of breathables rolled up) and floats reasonably well. Add the half-pound inflatable backrest from my Outcast and the top halves of my thighs stay dry - though my knees do press up against the inside of the donut somewhat unfomfortably, and it sure does "weebles wobbles - but they don't go down" quite a bit more than my v-boat. The inflator bag works efficiently and weighs another half pound.

    Here's the setup next to Scott V's FCIV:



    And me sitting in it:



    So now what? Heck, let's build one that's better! I used to sew and competed with stuntkites of my own design, I'm marginally skilled with a blade and fabric, and the sheepskin says that I've completed all prerequisites that somehow prove that I can design and build stuff...

    Well, I first did my homework. What's out there? Well, the DC was 'it", though they stopped making it 20 years ago. Since then, the donuts have gone out of vogue, and the U/V-boats are what's cool and what works. The Creek Company U-Boat 2000 weighs in at supposedly 6 lbs, though it plunks your ass into the water and is somewhat ungainly. The Creek ODC420 Lightweight is 8 lbs, and you sit high and dry. Add the inflatable seats and it folds down relatively small - maybe a 1800 in^3 daypack? Both of these guys are a pack cloth and vinyl bladder deal. Fianlly, the "Cadillac" of UL tubes right now is the Outcast Trinity. 6 lbs, urethane coated 420 denier fabric, bladderless, packs down into it's own 1600 in^3 pack. With pack and pump I think they claim 8 lbs?

    BUT, if 'ol Del could make a 3 lb tube 20 years ago, I can beat that right?

    So I first decided what the basic design would be - bladder in skin, or bladderless? At first I thought that bladder in skin would be easier being a bit leery about sewing and sealing a bag. I looked around for lightweight bladder materials, tried to get information on the mylar that they use to make balloons that is heat sealable and super light. Unfortunately, nobody wanted to talk to me. While I was waiting for information about the bladders, I came across heat-sealable urethane coated nylons. Similar stuff to what Outcast uses, but it's lighter (70 and 200 Denier). Think Thermarest skins. Apparently it's not too hard to work with.

    At this point it was decided - bladderless, heat sealed fabric. No sewing at all for the main bladder(s). Inflator bag and mouth inflated. No pump required.

    Next I had to decide on the shape of the boat. Should I go V-hull like the Fish/Fat Cats? U-boat u-tube style? Caddis pon'tube style? After spending a lot of time Google image searching all possible configurations, I settled on a simple u-tube for ease of manufacture. The main bladder would be two flat pieces of fabric edge welded with a perimeter butt seam. Did the calcs at 5 psi (about double what any normal human can blow by mouth) and the seams would only have to take 30 lbs per inch of seam of force. Apparently no problem. Did I mention that I managed to strike up a conversation with a guy who markets ultralight packrafts? He's been a great resource to bounce ideas off of.

    In addition to the simple u-tube "frame", there'd be a nice, fat inflatable seat to add buoyancy and to lift me out of the water. With this seat, I'd have the second bladder to give me some redundancy in case something terrible went wrong with the main bladder. Even the smaller seat bladder will give me more than 90 lbs of buoyancy. Great comfort that...

    Now to the drawing board! I wanted a 12" diameter main tube that ended up parallel after inflation. Did some drawings, and printed out a scale drawing and started playing with some Press 'n Seal wrap. This stuff is GREAT for getting in the ball park with goofy stuff like this.

    First try:



    Ooops! I guess if you model it flat, it won't blow up quite the same. Since the outer radius of the bladder "shrinks in" but the circumference of the flat profile is longer than the final inflated outer circumference, the thing closes up quite a bit!

    Did some calcs and back to the drawing board...

    Rev 2:



    Ooops again! Guess one of my assumptions was wrong... Try, try again...



    There! That's more like it...

    Now on to a bigger model to see if things "scale" right:

    Laying it out:



    Blowing it up:



    Looks good, but still a bit pinched in.

    Also, you'll notice that the nice triangular shape of the "tits" on the drawing don't inflate well. It was at this point that I started playing around with this profile a bit:

    Nope:



    Nope:



    Nope:



    YES!!



    Now that I had the geometry of the tube ends right. time for a full blown (no pun intended?) 1/2 scale model:




    Pretty damn cool! Still a bit pinched in. Couple more degrees maybe? Nip there, tuck here...

    To be continued...
    Last edited by SHigSpeed; 11-20-2010 at 02:26 PM.

  2. #2
    Join Date
    Jun 2009
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    Cal.
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    367

    Default

    Pretty cool!
    Looking forward to seeing your progress.

  3. #3
    Join Date
    Sep 2008
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    Citrus Heights, CA
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    Default

    Quick dissertation on valves:

    You can see on the pics above that I have a nice inflator tubes on the 1/2 scale models. Garden sheeting and duct tape work great, but not quite as quick to prototype as the Press 'n Seal. Anyway, you'd be surprised what valve manufacturers will send you for free as a sample!

    These inflator tubes are similar to what Outcast uses on the Trinity and on their inflatable seats. Work well, but not made for big volume in or out. I needed something else for the main bladder.

    I think everyone knows what a Boston valve looks like:



    Pros: Light (1 oz including threaded seat), cheap ($4 for a replacement)
    Cons: I couldn't find anyone who sold the damn seat! Everyone sells the valve but I guess the seats only get welded into the vinyl overseas in quantities of 1000s or more! I did finally find a way to get seats, but let's move on...

    Halkey/Roberts-Summit style raft valve:



    Pros: These things are great! They don't need to be welded or glued in, they have a nice feature that you can inflate them most of the way with teh valve open, then top off with the check valve active. They deflate just as quickly.

    Cons: They are a bit expensive, and they're HEAVY! 3 ounces. And BIG! Rolling one or two of these into a packing tube would suck. To have 6 ounces of valve in a tube that weighs under 3 lbs is silly.

    Finally, this guy:





    This is what's in my DC tube and gets the job done!

    Pros: Light (less than 0.5 oz), low profile, check valve, relatively fast inflate and deflate. Cheap - kinda. I found where to get them, but their minimum purchase is $500!! I did get some samples though.

    Cons: Well? It's a bit cheesy looking but asking around with people that design and build inflatable things say that they've never had a failure. It does require it to be glued or welded in, but who cares?

    I do have another couple of options yet to investigate (more samples in the mail - should be here Monday) but I think I'm set on the main valve for now. If I do smaller bladders (backrest maybe?) I may use either the tube inflator valve or maybe something like a twist close Thermarest valve.

    So, now that I have the basic shape pretty much down, it's time for a full size mockup. You may notice that I used the Summit 2 valve in this as it makes inflating and deflating easy peasy!



    You can see the Outcast seat in place to get an idea of what's to come.

    For grins, check out the evolution of the tube and sketchpad:



    The plan is to make it a bare bones and modular tube. So far, it seems like the tube and seat MIGHT be doable at right on 2 lbs. On top of that there will be a strap-on pocket option, possibly a backrest, big cargo drybag for the "trunk", stripping apron, and rod holders. Don't expect the all-singing all-dancing PVC rocket-launcher rod holders for this flyweight. I think even with ALL of this it'll be well under 3 lbs. Perhaps with all this and the inflator bag it'll nudge up to where the Del Canty was ala carte.

    More musings to come, gotta get dinner going...
    Last edited by SHigSpeed; 11-19-2010 at 07:27 PM.

  4. #4
    Join Date
    Aug 2008
    Location
    On the hill
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    260

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    I am soooooo looking forward to owning one of these things!

  5. #5
    Join Date
    Jul 2009
    Location
    Auburn, CA
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    Total engineer! Can't wait to see what the final model looks like. For now I'll stick with strapping my pack frame to my inflated tube. Good luck with your project!

    Dan

  6. #6
    Join Date
    Aug 2007
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    401

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    You will have no issue packing a tube in now huh Jay! Spectacular.

    SHig, rocket launchers sound like a blast for an accessory. Let me know if it makes the specialty item list.

  7. #7
    Join Date
    Jun 2007
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    El Dorado Hills
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    Mine better come with a light weight rod rack as well.
    So long and thanks for all the fish!!!
    `·.¸¸.·´¯`·.. ><((((º>`·.¸¸.·´¯`·.¸><((((º>`·.¸¸.·´¯`·.. ><((((º>

  8. #8
    Join Date
    Nov 2007
    Location
    Rocklin
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    130

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    Very interesting! Wonder how a light weight pontoon boat would work? I hate sitting in cold water. I am still interested in your pram project, but looking forward to more postings on the float tube. Looking for a used backpack on CL now! Bill

  9. #9
    Join Date
    Jan 2005
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    336

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    Very fascinating!!!!

  10. #10
    Join Date
    Nov 2009
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    Rescue ,CA Cromberg, CA
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    Shig, I think your post may have the most pages linked to a thread ! You are a talented man , happy new year!

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