Lightweight Kimber Build with Custom Carbon Fiber Stock

[CoMtnMike]

I’d definitely defer to @Gobber here, as I’ve only done two so far and completely guessed on the thicknesses. But, I would suggest going with multiple layers of 3k. The thinner fabric will conform much better to those complex curves with simple methods (but if you have a full vacuum bag setup that should do 3k and 12k equally as well). I think there are areas in my ultralight Kimber where there are only 2 layers of 3k, but areas like the wrist have more. A good core with one or two layers of thin 3k carbon that was laid and conformed well is incredibly rigid. My learning curve is a bit slower, so around the complex curves in the wrist/grip area I can feel that the first few layers didn’t pull perfectly to the core or the previous layer, and another layer or two is required.

I would say for the first time only try do do one layer of carbon at a time, and you’ll learn how it pulls, bends, and dries pretty quickly. Then just add layers until you are happy with how rigid it feels.

And remember that if you are going for a good to perfect surface finish, you will definitely sand through some of the carbon, especially with the thinner stuff. But therin lies the beauty of carbon fiber - you can just add more!

Keep us updated and don’t hesitate if you have more questions!

@RepeatPete this is amazing and I have read through it and your earlier build 2 or 3 times now in awe. I think I have convinced myself to give it a try if I can find a used take off stock for my Ruger American at a reasonable price for the donor action inlet section to build off of. I'm curious if you or @Gobber would have thoughts on just shaping in foam vs maybe a 3d print shell to design the grip + butt stock section just to get the negative comb and toe angles correct, consistent shape and symmetry... My shaping and carving skills are rough... 3d printing a shell, filling with expanding foam and then covering with carbon fiber would definitely be heavier of course but my prime objective would the rokstock or mountain tracker lr ergos first and any savings in weight over the factory stock would be bonus...

 

[RepeatPete]

@RepeatPete this is amazing and I have read through it and your earlier build 2 or 3 times now in awe. I think I have convinced myself to give it a try if I can find a used take off stock for my Ruger American at a reasonable price for the donor action inlet section to build off of. I'm curious if you or @Gobber would have thoughts on just shaping in foam vs maybe a 3d print shell to design the grip + butt stock section just to get the negative comb and toe angles correct, consistent shape and symmetry... My shaping and carving skills are rough... 3d printing a shell, filling with expanding foam and then covering with carbon fiber would definitely be heavier of course but my prime objective would the rokstock or mountain tracker lr ergos first and any savings in weight over the factory stock would be bonus...

Thanks for the kind words!

I think 3D printing definitely has its place in stock modifications, but mostly for something like this: https://fullframeoutdoors.com/products/full-frame-tikka-accessories

For wrapping with CF after, I would shy away from 3D printing because those pieces are some type of polymer (PLA, ABS, etc.) which does not bond great with resin.

I would strongly recommend something like this foam: https://www.smooth-on.com/products/free-form-air/
It’s nice and lightweight, super easy to form, and most importantly for my low skill level, really easy to shape/sand after it’s cured. Regular sandpaper and files can remove a lot of material quickly with a bit of pressure, but it’s rigid enough that you won’t get gouges or nicks. Also, I think you would end up using something like this to fill in the gaps and transitions between the original stock and the 3D printed pieces if you went that route.

 

[CoMtnMike]

Thanks for the kind words!

I think 3D printing definitely has its place in stock modifications, but mostly for something like this: https://fullframeoutdoors.com/products/full-frame-tikka-accessories

For wrapping with CF after, I would shy away from 3D printing because those pieces are some type of polymer (PLA, ABS, etc.) which does not bond great with resin.

I would strongly recommend something like this foam: https://www.smooth-on.com/products/free-form-air/
It’s nice and lightweight, super easy to form, and most importantly for my low skill level, really easy to shape/sand after it’s cured. Regular sandpaper and files can remove a lot of material quickly with a bit of pressure, but it’s rigid enough that you won’t get gouges or nicks. Also, I think you would end up using something like this to fill in the gaps and transitions between the original stock and the 3D printed pieces if you went that route.

thanks for the reply. Just to clarify were you suggesting free form air on top of / in addition to green insulation board? Or skipping the green board all together and just using FFA? I had already considered using FFA maybe with CF chop mixed in for the grip and neck area - more moldable and stronger, but I wasnt considering it completely replacing green foam.

Thanks for the thought on 3d print compatibility, that makes sense. The other idea I had was buying a 1mm thick sheet of CF to cut the grip & butt stock shape from and control the intended dimensions - this would be epoxied into a center cut of the remainder of the stock grip / tang/ trigger area and then sandwiched in green foam / FFA. It would control dimensions and support the neck area rather than just the shell... Worth the effort or just build out of faom and put enough support int he shell layup?

 

[Ice-kub]

thanks for the reply. Just to clarify were you suggesting free form air on top of / in addition to green insulation board? Or skipping the green board all together and just using FFA? I had already considered using FFA maybe with CF chop mixed in for the grip and neck area - more moldable and stronger, but I wasnt considering it completely replacing green foam.

Thanks for the thought on 3d print compatibility, that makes sense. The other idea I had was buying a 1mm thick sheet of CF to cut the grip & butt stock shape from and control the intended dimensions - this would be epoxied into a center cut of the remainder of the stock grip / tang/ trigger area and then sandwiched in green foam / FFA. It would control dimensions and support the neck area rather than just the shell... Worth the effort or just build out of faom and put enough support int he shell layup?

I'll add my two cents on the cf sheet down the middle. I'd say go for it after breaking a stock I built that had the layers down the middle. I had to work extremely hard to break it. I used three layers of 1/2" xps foam board with 2 layers of 3k CF twill sandwiched between each layer of foam.

If assuming the 1mm cf sheet you mentioned is made of 3k, I believe that would mean it is made 4 layers thick which would be very strong.

The FFA mixed with carbon chop is a great idea as well.

 

[CoMtnMike]

I'll add my two cents on the cf sheet down the middle. I'd say go for it after breaking a stock I built that had the layers down the middle. I had to work extremely hard to break it. I used three layers of 1/2" xps foam board with 2 layers of 3k CF twill sandwiched between each layer of foam.

If assuming the 1mm cf sheet you mentioned is made of 3k, I believe that would mean it is made 4 layers thick which would be very strong.

The FFA mixed with carbon chop is a great idea as well.

were you intentionally breaking it? But yes I like the idea of a center beam and using shape structure like that to add strength

 

[Ice-kub]

were you intentionally breaking it? But yes I like the idea of a center beam and using shape structure like that to add strength

No, it was a formidilosus bedding job that I didn't want to be a formidilosus bedding job haha

 

[CoMtnMike]

No, it was a formidilosus bedding job that I didn't want to be a formidilosus bedding job haha

haha, got it. It was hard to know what "I had to work extremely hard to break it." meant! I mean intentionaly breaking things is a standard way to prove how strong the construction method is...