Wood/carbon fiber laminate

[katokoch]

Before I start buying wood and laminating boards up for a new stock blank, I'd like to see if anyone has input on something I was considering.

I'm probably going to make a stock from 3/4" thickness walnut boards, laminated with an epoxy. I was thinking... what about putting a sheet of carbon fiber inbetween the peices of wood?

Would putting carbon fiber inbetween already thick peices of walnut make any difference in stiffness/stability? The stock itself would be 3" wide at it's biggest... there would be only three peices of carbon fiber used. Would it make cutting, shaping, and finishing the stock any more difficult?

All boils down to: is laminating carbon fiber inbetween walnut boards worth my time?

 

[tpbscha]

I believe this place uses that type of construction. My gunsmith has several at his shop and they are NICE!

http://www.sandkgunstocks.com

 

[butchlambert]

I have 3 benchrest rifles that are carbon fiber laminates. 2 redwood and 1 walnut. I have had 2 of them for several years and they are great. I would reccomend that you vacuum bag them rather than clamp them when gluing them up.
Butch

 

[katokoch]

My preferred method of laminating boards is stacking several 45 lb. weight plates on top of the wood. Several hundred lbs. of pressure evenly spread out can't be bad.

 

[butchlambert]

You may get by stacking weights, but you cannot get the even clamping force like you can with vacuum bagging. I guess that you work with what you have.
Butch

 

[criver600]

Butch He's just wanting to laminate the carbon fiber not encapsulate the whole stock.

The carbon fiber cloth will add stability to the blank, unidirectional pultruded carbon fiber sheet will add significantly to the stiffness.

 

[butchlambert]

I thought that he was talking about a competition stock. The carbon fiber cloth is laid in both vertical and the horizontal plane. It is very difficult to clamp in both planes at the same time and do a good job.
Butch

 

[katokoch]

I don't quite have access to vacuuming something that large...

 

[katokoch]

What sort of epoxy will I need to use for laminating carbon fiber with walnut?

FYI what I am doing is laminating together four 3/4" walnut,7"x30" peices) to make a single blank suitable for hacking a stock out of. I'm epoxying a sheet of carbon fiber inbetween the boards to add stiffness. I'm ordering the fabric as I type this up and will get 11 oz. 2x2 twill fabric.

When I say I'm going to use weight plates for pressure, I mean I'm going to set the boards down on a concrete floor and add several hundred pounds worth of weight on top. I'm pretty sure the weight can be distributed evenly because I can lay the large 45-lb. plates across the blank and then stack up 35's and 25's and more 45's on top of them evenly so the weight should be even across the top of the boards.

 

[bkmilw]

Wood is softer than concrete, so if there is moisture in the crete, wich there is, the wood your weighing down will absorb it. Use a 2mm plastic sheet of some kind fore a vapor barrier between wood and crete. Some vapor barrier for a wood or laminate floor would be perfect.

 

[criver600]

West Systems

 

[TonyR]

You might also want to consider the MAS Slow Cure Low Viscosity epoxy. I built a lapstake wooden boat a number of years ago and many of the cedar planks had to be scarfed to make something long enough to go around the curves in the hull.

Standard glue-up procedure for the scarfed joints was to wet both surfaces with fresh epoxy, then mix some micro-balloons into the remaining epoxy, then smear that onto the joint to prevent voids from forming as the epoxy soaked into the wood. Then we used lead ballast ingots from an old Skipjack to compress the joint. What a mess!! Keep a supply of plastic sheet or drum liners handy because this stuff will run all over the place otherwise.

We tested some of these joints to fracture and the wood adjacent to the scarf always broke out, never the epoxy itself. The keys to success seemed to be wetting the wood thoroughly with epoxy and eliminating any voids with the micro-balloon slurry and the weights. I never tried this with any other brand, but I would look for low viscosity and slow cure.

I just completed some stock work with this same procedure and it seemed to work just as well on walnut as it did on cedar. I am going to make up a stock blank myself this winter and the carbon fiber sounds like a great way to stiffen things up particularly in the pistol grip area which looks to be vulnerable to splitting without some reinforcement.

I hope you will post your progress as you move along.
Tony

 

[butchlambert]

You might do a search on vacuum bagging. It is an easy, clean way to laminate. I have bought used vacuum pumps for $25. West Systems is a great source for epoxies. Remember carbon fiber is very abrasive and dulls cutting blades. We have a fellow that disagrees with that on this forum. I doubt that he has machined any.
Butch

 

[katokoch]

I'm getting an epoxy reccomended by the company that is selling me the carbon fiber. It may not be perfect but it should work. I appreciate the advice though... there will probably be another time for me to try different epoxies out.

Butch: Carbon fiber dulls blades? How else is it difficult to cut/carve/sand?

 

[criver600]

As long as you use carbide its not too bad. Sands great but use a collection system and at the very least a good dust mask.

Here are two sitka spruce/rosewood carbon fiber cloth blanks. Its hard to see but there is a layer of carbon fiber cloth between every lamination.

 

[TonyR]

Kato.
Who is your supplier for the carbon fiber and the epoxy?
Thanks
Tony

 

[katokoch]

Criver thanks for the advice, I appreciate it.

I'm ordering my carbon fiber fabric from http://www.shopmaninc.com/carbonpage.html

We'll find out tomorrow how good their products are but I can tell anyone now that their customer service is excellent.

 

[katokoch]

Well, I got the stuff in the mail today and went right to work.

Lessons learned:

-12.3 oz. carbon fiber is thicker than I thought it would be
-The fabric is very loosely woven and loves to seperate at the edges
-The best way to cut it was with a razor blade over a simple cutting board
-It took lots of epoxy to saturate the CF so it would completely bond with the walnut without pockets. Once again, thicker than I thought it would be.

From beginning the cutting to setting the final weights on the blanks, it took a little over an hour. I used a total of 395 lbs. for weight... should be enough. Lots of epoxy was squeezed out the ends and sides, but I would rather see that than none.

I would have photos but my camera isn't working

I'm going to remove the weights tomorrow morning and see how it turned out. Sadly, I move back to school tomorrow so I will be doing the cutting later... maybe in a month or two. Good news is, I realized last night I had enough space in the single blank I laminated to make two low-rider style stocks.

 

[MCehand]

A small shop vacuum will give you all the negative pressure you need. Clear plastic like you find at Home Depot or a garden store will work for the wrap.
You only need to use the vacuum for about three hours.

If you use thinner wood it will also make the stock more ridged.
1/4 to 1/8 inches thick pieces work best for small projects.

Good luck.

Michael

 

[TiGuy]

Well I guess you found out the hard way that 12oz woven fab is waaaay too thick for laminating wood, especially if you aren't using a vacuum bagging system. 5.7oz woven,loose weave) is plenty. The looser the weave the easier it is to impregnate the fabric. Remember you only need enough resin to get a 50/50 mixture of fabric/resin,theoretically) for optimal strength, but it's easier to go heavy on the resin to fill any gaps in the cloth.

I suggest buying kevlar cutting scissors to cut the fabric, or a rotary cutter/cutting mat used to cut plain fabric. West Systems or Aerospace Composite Products,ACP-composites.com)Easy-Lam epoxies.

If you find any voids in the seams between the CF and the wood when you are sanding, you can use a woodgrain filler to seal them up. CA glue also works well for larger voids.