External Carbon Frame Backpack from Scratch

[nighthawkf-117]

Hi everyone,

I'm going to take you all along for the build of my newest backpack this spring. This will actually be version 3 of my backpack, Ive not posted much about these before, but feel I finally have a lot to share for someone looking to do this themself. First a little history about V1 and V2 then Ill get on to V3.

V1:
This was actually my third backpack build, the first two being lighter packs with aluminum frames made from tent poles. This was heavily inspired by the EXO pack and used a 3d printed frame which was then wrapped in carbon fiber. This worked ok but was very time consuming and not very pretty. Additionally it was not as stiff as I wanted it to be. However I did pack out a whole quartered whitetail on this frame with no problem. The bag itself was Ecopak EPLX 400. The bag was essentially a single big roll top bag with stretch pockets and the sides and front. The bag worked great and I used the same bag on V2.

V2: After seeing Kifarus ARK frame I new I wanted to do something similar. I modeled the frame in CAD and 3d printed molds out of ABS. I then painted the molds in Duratec surfacing primer and polished. The frame could be directly fabricated in this mold. Ill go into more detail as I build V3 as the process to create the molds will be the same. This yielded an extremely strong frame. The shoulder straps and hip belt was attached to the frame and buckles sewn on with webbing to attach the bag. As mentioned I used the same bag from V1. This pack worked great and I have lots of miles on it. Loaded up to 65lbs in my recent Idaho bear hunt and carried it without problems. However Ive identified several improvements to make for V3.

1: The load lifter points on the frame need to be higher in relation to the shoulder straps, this will better distribute weight through the frame when the load lifters are used.

2: When the pack is loaded down and full it has a tendency to swing laterally. This is due to the taper between the top of the frame and the bottom.

3: I found myself wishing I had a way to access the bottom of the bag without completetly unpacking it. I plan to add a large vertical zipper to the front of the bag.

4: The Ecopak has worked great for several years now but it starting to show its age. Im going with a more robust fabric this time around.

5: The internal foam for the shoulder straps have stretched and worn some over years of use. Ill be using a more robust foam in V3.

Ill go into more details about the design in future posts. The mold design is done and being 3d printed now.

 

[TxLite]

The creativity and people’s capabilities on this forum never ceases to amaze me.

Great job and looking forward to seeing the next revision.

 

[4090Sharps]

Thanks for sharing with us!!! I’m excited to follow along.

 

[doncarpenter]

Fantastic! I would love to hear more about the frame build. What kind of sewing and fabrication equipment you're using? I would also like to see some pics of the frame and suspension by itself.

Strong work, very impressive.

Sent from my SM-S911U using Tapatalk

 

[nighthawkf-117]

Here are some pictures of my current frame. Some of the hardware is 3d printed from CF reinforced nylon. You can see some of the "stretching" I'm referring to in the shoulder straps which will be addressed in this version.

I'm fortunate to have a Juki 15-41 compound feed sewing machine. I typically use size 92 coated polyester thread which is very strong. The carbon equipment is actually quite minimal and ill show some of that with this frame build. Mostly hand tools and a vacuum pump.

 

[nighthawkf-117]

Printing of the frame mold is done. I use a syringe to inject acetone into the seam between printed parts which melts the ABS and welds the parts together. Some pretty light sanding was then done to smooth the surface Some minor filling with bondo to smooth a few areas and the mold is ready to be painted. I will paint the mold with Duratec surfacing primer which goes on very thick and will level out the small imperfections in the mold surface. The Duratec will then be polished and ready to fabricate parts.

 

[4090Sharps]

Really cool. I'm interested to see how you handle making the slots in the frame. I see the raised sections to account for them. Do you lay the carbon fiber over the top, vacuum bag the whole thing, and then trim those sections out?

 

[nighthawkf-117]

Yes the frame gets layed up as one piece then the slots are cut after the fact. Much easier to do it this way. I use a 3d printed guide for my Dremel and an end mill to cut the slots.

 

[doc holiday13]

looks awesome. Even cooler that you though ahead to print a guide for milling out the slots.

What size is the frame? I assume you're using someone elses shoulder straps and waist belt??

 

[4090Sharps]

Yes the frame gets layed up as one piece then the slots are cut after the fact. Much easier to do it this way. I use a 3d printed guide for my Dremel and an end mill to cut the slots.

Great idea with the jig/guide!

 

[4090Sharps]

Is that a Venom stretch fabric you used for the inside of the shoulder straps? How are you liking it for that application?

 

[nighthawkf-117]

I make my shoulder straps and hip belt. I'll detail that process in this thread.

Yes that is the venom stretch mesh. Traditionally 3d spacer mesh is used for inside shoulder straps but I honestly don't feel it adds a lot to the comfort of the strap with a heavy pack. The venom stretch has worked really good and is super durable. Its got a good amount of grip/texture to comfortable with clothing in my opinion.

 

[4090Sharps]

I make my shoulder straps and hip belt. I'll detail that process in this thread.

Yes that is the venom stretch mesh. Traditionally 3d spacer mesh is used for inside shoulder straps but I honestly don't feel it adds a lot to the comfort of the strap with a heavy pack. The venom stretch has worked really good and is super durable. Its got a good amount of grip/texture to comfortable with clothing in my opinion.

Thanks! I typically use spacer mesh or Spandura, but that Venom fabric is so tough, I bet it holds up extremely well.

 

[tcg144]

Awesome, can’t wait to see the next steps.

 

[nighthawkf-117]

While in between steps on the frame mold, I completed the shoulder straps. These straps are of my design and are probably the 6th iteration. Ive gone through various shapes and materials. I have specifically found the internal foam to be very important to the comfort and durability of the straps. I use a foam called Minicel T600. This is an EVA foam in 6 lbs density. I found lighter density foams are more comfortable initially but don't hold up well.

I am using Xpac X50 fabric for the pack. This is among the most durable and waterproof fabrics available. I decided to go with Multi-cam Alpine for the pattern. I know this isn't a practical camouflage but its all about looks for me. I like the look of the fabric. Ive never been busted by an animal from my pack!

You will notice some 3d printed hardware. I use a PA6 CF filament for these components. This is super strong plastic and Ive yet to have a failure of any of my printed hardware.

First the webbing and hardware is sewn to the facing fabric.




The Venom stretch mesh backing is then sewn onto the facing fabric. The strap is then turned inside out and ready to insert the foam.

The foam is worked into the strap. This is tough but eventually it is properly positioned.


Once the foam is worked in place the entire strap is sewn in a few places.

And two straps ready to use!