Re: Carbon wrapped barrel
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sirhitalot</div><div class="ubbcode-body">it will be stiffer than a pencil-barrel, thats for sure... You dont believe that the carbon fibre will better the accuracy ? As far as the safety goes, how do you explain that an already safe contour will be questionable when applying CF? The heat dispersion isnt too important to me. </div></div>
I misread your initial post as you were planning to re-contour the blank that you're starting with and sizing it based on QL output. QL pressure curve data isn't necessarily going to give appropriate safety margins and there's more to sizing barrel contours and associatively, action tenons/lugs/lug abutments than just Lame' equations. It was a word of caution to be careful as I don't know your experience/education in this regard.
CFRP wound structure finishes with a modulus that's around 3-5% of the comparative modulus that barrel steels maintain. Adding the weight and material to the outside doesn't do much for you in terms of stiffness, especially with wound filament as opposed to pultruded, compression molded or semi-planar laminate.
Adhesion characteristics, the barrel heat associated with use and the largely different CTE between the CFRP and barrel steel is going to cause longer term post-cure bonding issues at the interface surfaces.
It will only be stiffer if you can figure out how to make sure it stays there through the life of the barrel, once it starts to loosen up and wiggle in places how do you think that will affect the repeatability of the rifle? We know how letting the barrel touch the stock sometimes will totally jack up a rifle, so failing bond interface will very likely jack up the repeatability of the rifle in a manner you're not going to like.
The purpose that many are striving to increase stiffness for is actually to push the natural frequency of the barrel up. It may work out that because of the added mass from the CFRP with a weak bond interface for load transfer and marginal material properties of wound filament bonded to the steel you're going to end up dropping the natural frequency of the system. Certainly? I don't know, I'd have to actually sit down and do the math on it to see, but it's been known to happen in other structures that I've analyzed.
So, to kind of cap off the novella:
1) If you keep an already proven-safe contour then the safety issue is mitigated and I'll retract my safety statement.
2) Heat dissipation, stiffness and associatively the Fn on the system are all not going to meet the goals you've set forth
3) Filament wound application is poor for this due to how wound filament carries load
4) Bond interface will very likely have longevity issues for several reasons
Overall an appropriately contoured barrel from a solid barrel maker will do very well without the added hassles and experimentation and issues that will very likely arise from this.
If you wanted to do it because it looks cool, then the best of luck to you. As long as you're not cutting away steel on the assumption that the CFRP will carry the load instead, I wish you the best of luck in the endeavor.
