External Carbon Frame Backpack from Scratch

[tcg144]

What is the design thickness of the finished piece? How does that relate to you mold depth? What did you use to cut the carbon out?

I’m interested to see how you finish the edges and cut the holes.

 

[Traskie]

Do you have the stls for the mold available anywhere?

 

[Trumpkin The Dwarf]

This is wicked cool! Now what I would like to know is if the foam core makes an appreciable strength to weight difference over a thin marine grade plywood core. The old kifaru ultralight stays were built like bow limbs. Just a curious idea.

 

[nighthawkf-117]

What is the design thickness of the finished piece? How does that relate to you mold depth? What did you use to cut the carbon out?

I’m interested to see how you finish the edges and cut the holes.

I am for a little over 4mm finished thickness. There isn't too much engineering that goes into this, its plenty strong. I just want enough frame thickness that all the edges can be rounded over nicely and look right. The mold depth is also right around 4mm. When a part is made I like the layup to essentially end up flat with the flanges of the mold. This just helps the vacuum bag easily conform to the layup without having to sink into a recess. The carbon fabric is cut with a rotary cutter over a self healing cutting mat. The dry fabric is very fragile and frays easily.

I should note here I'm not an expert on any of this. This is all what Ive learned over years of making composites as a hobby. Its just what works for me.

 

[nighthawkf-117]

Do you have the stls for the mold available anywhere?

I would share STLs on a case by case basis

 

[nighthawkf-117]

This is wicked cool! Now what I would like to know is if the foam core makes an appreciable strength to weight difference over a thin marine grade plywood core. The old kifaru ultralight stays were built like bow limbs. Just a curious idea.

I just use the foam because its easily available to me and easy to cut out with an knife. I'm sure a wood core would work just fine and be a similar weight and strength.

 

[nighthawkf-117]

Work on the frame continues. I pulled the part from the mold. Overall this part turned out great and will work just fine. You might see in the pictures there are some small voids in the surface where the carbon didn't conform perfectly to the surface of the mold. I sanded these areas and spot filled them with some epoxy.


The flashing around the outside of the frame was trimmed off with a band saw. I then went on to cutting the slots. As mentioned I used a dremel with a 3d printed guide. I start by drilling a starter hole in each slot with a drill press. The guide is then located to the slot and clamped. The center section of the guide is then removed. The slot is then cut with a dremel and a 1/8" endmill. The guide is sized so the dremel can just follow the inside perimeter of it and creates the size slot I desire. Each slot is then cleaned up with sandpaper and a nice radius formed on all edges.

 

[Trumpkin The Dwarf]

That looks fantastic! I’ve done a lot of fiberglass work, but never carbon fiber. I’m assuming it’s very similar working just harder to cut

 

[Traskie]

I would share STLs on a case by case basis

Totally get that.

The frame looks incredible, and this build along has definitely got my gears turning on what I could make for myself

 

[nighthawkf-117]

Frame is done and ready to attach webbing too. After some minor filling and sanding I clear coated the frame with Spraymax 2k. This stuff is much tougher than normal rattle can paint and is a true two part hardening paint.
Overall it’s not the most flawless carbon part in the world, but totally functional. In the future I’ll probably make another one once the design is proofed out.

 

[4090Sharps]

Really nice work. I love seeing what you're able to accomplish through the use of a multipart 3D-printed mold. This seems like the sort of technique that could be extended to all manner of parts/applications.

 

[nighthawkf-117]

Thank you! I hope this can inspire someone. I got my start years ago making gear from reading threads on forums like this. It can seem daunting at first but anyone can do projects like this at home with enough dedication and planning.

 

[nighthawkf-117]

The hip belt was finished this week. It’s a similar process to the shoulder straps. The belt is sewn from combination of x-pac, 500d cordura (the grey), and venom stretch mesh.


A Velcro seam is sewn to the middle of the belt where the foam will be inserted later.


The lumbar pad is the same with a Velcro seam to add foam. This also allows you to fine add or subtract foam for a different fit.


Foam then inserted which is a huge pain but it eventually fits

 

[nighthawkf-117]

The lumber pad foam is the same foam used for the shoulder straps however with a total thickness of 1.5”. The two sheets not facing the wearers back have holes drilled in them to save some weight and add some compliance. They glued together with contact adhesive and inserted into the pad.

Finished hip belt

And how its secured to the frame.

 

[nighthawkf-117]

I got the back itself finished this week. I have found for backpacking and extended hunts I like one large bag. For this pack I added a zipper along the front which will let me access gear in the pack without fully emptying it. I also added a large stretch pouch with a zipper to the front for storing rain gear and whatever I need available quickly. The bag is sewn as three panels which are then all sewn together.

Venom stretch pouch with its zipper on the right and the main zipper on the left. The main zipper is a YKK aquaguard.


The bottom panel is two layers of fabric. Xpac X50 and then an additional layer of 500d Cordura for extra durability.

Any sewn through areas like this are taped with UltraTNT tape.



Back panel with the slot for the frame.

 

[nighthawkf-117]

The side panels have large stretch pouches for storage. These again are Venom Stretch mesh with a pleated Cordura bottom. Ill use shock cord later the cinch the top.


All of the major panels layed out to be sewn together.


After being sewn together the edges are bound using 1 inch grosgrain ribbon. I have a nice binding attachment for my Juki that makes this easy.

Then flipped right side out.

 

[4090Sharps]

The side panels have large stretch pouches for storage. These again are Venom Stretch mesh with a pleated Cordura bottom. Ill use shock cord later the cinch the top.
View attachment 1029026
View attachment 1029027
All of the major panels layed out to be sewn together.
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After being sewn together the edges are bound using 1 inch grosgrain ribbon. I have a nice binding attachment for my Juki that makes this easy.
View attachment 1029031
Then flipped right side out.
View attachment 1029030

Not sure if you're interested or tried one, but you can get a special needle plate and set of feet for binding that will make binding much easier on that 1541:

NEEDLE PLATE+FEEDER BINDER+WALKING FOOT FOR CONSEW 206RB, JUKI DNU-241, DNU-1541 | eBay

CONSEW: 206RB. JUKI: DNU-1541 DNU-241. 1SET Raw Edge Plain Tape Binder. 1SET Walking Presser Foot. 1SET Needle plate and feed dog. And SIMILAR WALKING FOOT SEWING MACHINES. 1PCS Radish head short handle screwdriver.

www.ebay.com

 

[nighthawkf-117]

Not sure if you're interested or tried one, but you can get a special needle plate and set of feet for binding that will make binding much easier on that 1541:

NEEDLE PLATE+FEEDER BINDER+WALKING FOOT FOR CONSEW 206RB, JUKI DNU-241, DNU-1541 | eBay

CONSEW: 206RB. JUKI: DNU-1541 DNU-241. 1SET Raw Edge Plain Tape Binder. 1SET Walking Presser Foot. 1SET Needle plate and feed dog. And SIMILAR WALKING FOOT SEWING MACHINES. 1PCS Radish head short handle screwdriver.

www.ebay.com

I have seen the really expensive ones and didn't know these existed. I think I need one!

 

[doc holiday13]

Man.. Looking GREAT!!! Kinda looks like a cross between the Kifaru Ark and Initial Ascent frames

 

[nighthawkf-117]

This pack is largely done now. Finishing steps include sewing the roll top webbing, and making the straps which attach the pack to the frame.





A look at the side zipper to allow access to gear in the bottom of the pack.