MYOG - External Frame backpack - DJ2 style

All

I'm thinking of copying DJ2's carbon fiber external frame backpack (see the threads "Very Light Pack Frame" and "9.5 ounce external frame backpack" in this listing). As I'm not much of a tailor, I think I want to use an already manufactured set of shoulder straps and waistbelt. Cheap is good, as this is a first attempt. Anybody have a source for this sort of thing, beyond using military surplus ALICE gear?

Sincerely

Steadman

Here are the straps removed from a Coleman Max. No cutting. It velcro's in place into a set of webbing on the pack body. Maybe not perfect for what you want, being a central mount rather than two separate straps, but pretty cheap.

Outdoor Wilderness Fabrics has a pair of shoulder straps you can just buy. Or you can cut some off of an old school bag.

I have found great waist belts and shoulder straps on used packs sold at 2nd hand stores. One can often get the entire pack cheaper than buying new belts and straps.

Here's a link to more info on the pack itself.

http://www.backpackinglight.com/cgi-bin/...thread_id=40531

dj2

Thank you!!!

Couple questions:

1) Where are you buying the fittings that connect the carbon fiber spars?

2) How do you cut the carbon fiber spars safely? I seem to recall that there are issues with splintering when doing this.

3) What kind of glue are you using to cap the carbon fiber spars?

With Great Respect

Steadman

Steadman,

The spars can be cut with a fine toothed hack saw blade. Put some tape around the spar before cutting to reduce splintering.

I've plugged the ends with solid fiberglass or solid carbon fiber rods and glued them in with super glue (aka ca glue). Epoxy would also work. For that matter almost any glue would probably work.

Glue and rods and a whole bunch of other stuff can be bought at Kitebuilder. Here's a link:

http://www.kitebuilder.com/catalog/produ...e59ecbaea89e211

The nylon barbed plumbing fittings are sold in the plumbing section. Their intended use is for connecting flexible tubing. The tubing is slipped over the barbed ends of the fittings. My favorite is the 1/2" black nylon T. Here's a link:

http://www.mcmaster.com/#barbed-tube-fittings/=eybi3b

Best of luck on your project. With a little experience I think you'll find that it is pretty easy to put together a frame.
dj2

Epoxy / Araldite glue works best. Bonds with the resin.

Frenchie,

Thanks for the tip. I'll give it a try.

dj2

Steadman,

Here's some info on making your own shoulder straps in case you change your mind.

http://www.backpackinglight.com/cgi-bin/...thread_id=41336

Daryl

Very cool.

How well do you think it would work with a hip belt?

I'm looking around a craigslist locally to see what I can find for a cheap used external frame pack as well, but this looks cheaper and simpler than retrofitting something that someone else built.

Steadman,

It would probably work well for a waist belt too. I haven't tried it, however.

You can eliminate shoulder straps completely if you use a front bag. I haven't used shoulder straps for years.

The simplest waist belt would be one made of 2" wide nylon with a 2" wide quick release buckle that adjusts on both ends (you don't have to sew the buckle onto the webbing). Check out the 2" double adjustable side release buckle at this link:

http://www.seattlefabrics.com/side.html

I have been using unpadded waist belts for a couple of years now. If they fit well I don't miss the padding at all. The belt fits me well if I simply cut it in half and sew it back together so the two pieces slope slightly upward from the back center (where the belt would cross my spine).

dj2

I think I understand what you are saying here. I need to go out and check on what I can acquire locally, and then start playing with the project.

Have you ever drilled holes in the carbon fiber poles? I'm thinking about tapping holes in the cross pieces for attaching the shoulder straps and putting in the load lifters, but I'm not sure how much that would weaken the stength of the pole.

I don't think the carbon fiber poles will tolerate any holes without losing most of their strength.

An aluminum tubing cross bar will tolerate a lot of holes. I use a thin wall 5/8" od aluminum tube for the top cross bar if I need to drill holes. It slips right over the 1/2" barbed plumbing fittings.

Take a look at the ZPacks Exo pack for a method of attaching shoulder straps without drilling holes in the carbon fiber spars. Here's a link:


http://zpacks.com/backpacks.shtml

That system makes all kinds of sense.

I'm pricing this out before I place an order and get stuff, and I have 3 more questions:

1) Just to confirm, these are the nylon tees you were talking about for connecting the frame together, and for connecting the frame to the hipbelt:

http://www.mcmaster.com/#nylon-barbed-tube-fittings/=f0upmb

2) You still prefer the Skyshark P400 tubing for a frame for carrying 30-40 pounds?

3) Do you use the .240 ferrules that Kitemaster sells to plug the ends of the rods, or does the .25 OD fiberglass solid rods work if you finagle them a little?

Sorry to ask all these questions; this is so very cool, and I'd like to get as close to right the first time as I can.

Steadman,

Your questions:

#1 Yes, your link is heading toward the nylon Ts I use but you must further select color, type of barb and size. Only the size is crucial. I use the 1/2" Ts.

#2 Yes, Skyshark 400 or something comparable for 30-40 lbs. My wife's pack is using no-name fiberglass tubing but she rarely carries more than about 20 lbs.

#3 Yes I have used the .240 ferrules. Either carbon fiber or fiberglass is fine. I haven't tried the .25od ferrules and probably wouldn't use them. The id of the Skyshark 400s is .244. It is much easier to add a bit more glue than to wittle down a ferrule. You might also be able to just plug the ends with epoxy but I haven't done this so I can't speak from experience.

Daryl

Steadman,

Here's a link to some photos showing details of my latest pack. (I couldn't figure out how to make it a hot link so you will have to copy and paste it. Sorry. Anyone know how to make this a hot link?)

Link to pictures...

The small machine screw you see in the top corners of the frame are from McMasterCarr. They are 4-40 size, stainless(18-8), pan head, phillips, 3/4" long with matching nylon insert locking nuts.

The 5/8" buckles sticking out of the top corners are where I attach the front bag to the frame.

The string (100 lb kite string)you see goes from the top corners of the frame to loops on the waist belt. It is cinched tight and holds the frame together.

The back bag has two loops that simply go over the top corners of the frame. Two velcro loops lower down then go around the vertical members of the pack frame. The front and back bags can both be removed from the frame without taking the frame apart.

The two 1/2" wide webs coming from the waist belt attach to my front bag bottom (or to shoulder straps if you use them).

The 1/2" webs coming from the waist belt and the top corners of the frame are run through the T fittings and then knotted. The thickness of the web makes for a nice snug fit for the spar within the nylon Ts.

The 5/8" aluminum top bar makes a good handle to lift the pack. I dimpled the ends a little to encourage it to stay on the nylon T. You could also use a carbon fiber cross top bar and run it inside the T instead of over it.

Enjoy.

dj2

Thanks for the hot link Bill. It was delicious.

Daryl

Thank you. That was very comprehensive, and answered questions I should have asked, but didn't understand well enough to. I think I can do this. I aim to have a parts list together this next week, and then put this together over Christmas and New Years.

Sincerely

Steadman

Dj, did you put a reinforcement patch behind (inside) the two main loops that hold the bag? I would think that those are the two main stress points that carry all the weight.

finallyME,

Good point on the reinforcement patches. I agree that these are the two main stress points.

Short Answer
There are two 2" X 2" patches of adhesive insignia cloth on the inside of the bag at the two attachment points. They are glued and sewn to the fabric. Reliability of this particular combo hasn't been fully tested.

Longer Answer
I'm experimenting with various hardware, fabrics and reinforcements to determine how light I can go. So my goal is to work my way down to a bag that self destructs, then to return to the last, lightest one that held up well.

The bag in the photos is made of uncoated, low quality 1.1 ounce ripstop with minimum reinforcements. I've used it for about a month, on a daily basis, carrying up to 30 lbs for distances of about 1/2 mile. It is too early to say whether or not it will hold up for the long haul, however.

Previous bags were made of uncoated, good quality 1.9 ounce ripstop with more reinforcments. For reinforcements I typically would add a 1" X 24" long piece of light nylon webbing running vertically inside the bag under and below each of the main loops from which the bag hangs. I've also experimented with including 1" wide seams in this area. All of these prior experiments have held up well with years of in field testing.

dj2

Steadman,

Ordering things from Kitebuilder has been taking a long time. I placed a small order with them almost a month ago and I don't think it has been sent yet. Another person said they have been waiting months for an order to be delivered.

dj2

This looks way more comfortable than my old CampTrails external frame that ways 5 lbs when empty. Its also a good choice for my 13 yr old since I can replace the carbon tubes as he grows.

BTW, amazon.com has them for about $4 each. I've found everything else at local fabric and hardware stores.

Cool. Best of luck on your project.

There are a lot of ways to go, design wise. Don't feel constricted by the way I did it.

My wife's pack, for example, uses some no name fiberglass spars for the vertical frame members. They are quite flexible but she likes them that way.