Just built on a .585 butt blank using carbon fiber CFX grips. When the fighting butt was reamed the foam core was paper thin and split when it was put on. Using a EVA butt cap that fits the core. If you were to build on a blank with a larger butt diameter would you cut the foam core tenon off and ream the butt more or opt for a different grip. Unsure if reaming the cores so much compromises the carbon fiber material?

The foam core is the grip, the carbon skin over the top is just to protect the core. You could ream the core very thin and it would still be okay. As long as there is core to blank contact for support, you shouldn't have any problems.

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The tenons on the CFX grips I have used have had an O.D. of .750". If the butt measurement you supplied is correct, after reaming to fit you should have had about 1/16th of an inch of tenon surrounding the butt of the blank.

Anyhow .... if it makes you feel any better, I had the same thing occur when I did my very first foam core grip. So speaking from experience lol, even though the tenon split, if you can get the butt cap to go over the tenon without out it completely destroying the tenon, it shouldn't cause you any problems. The grip is going to be secured to the blank. It isn't going to move once installed.

I would go ahead and install the grip, but leave the butt cap off until the epoxy has set up and dried, then try and slide the butt cap on. If you fear doing so will damage the tenon, use a piece of masking tape (or 2 if needed) laid flat over the end of the butt and trimmed so that when you start to slide the butt cap on, a little bit of the tape rolls over the end of the tenon. It will make that edge a little slick and keep the tenon from chunking off. If that description makes sense?

If you wanted to eliminate what tenon there is left, you could install the butt cap similar to how you would if you used masking tape as an arbor for installing a reel seat. Wrap about a 1/4" wide strip up against the grip, and a 1/4" wide strip around the very end of the blank. Coat it well with epoxy and slip the butt cap on. I would think that would be more than adequate to secure the butt cap.

Finally, to avoid this same problem in the future, just ream the grip a little more. As you've found out, the foam core is rigid, if there isn't carbon sleeve surrounding it, it is gong to split if you've made the fit too tight. I've only used foam core grips on 4 of the rods I've built. The last 3 I did, I dry fitted them to within 1/4" to where I want them to end up.

I had the same issues on a nfc 736. I had the foam crack off when reaming si ce the part the cap attaches to was so thin. I ended up fitting a paper thin graphite/foam arbor for the butt cap. Next time, I think I will use some thread to fill the gap. For the arbor, the thinner diameter portion of the arbor started to through before it would bit the blank.

I had the same issues on a nfc 736. I had the foam crack off when reaming si ce the part the cap attaches to was so thin. I ended up fitting a paper thin graphite/foam arbor for the butt cap. Next time, I think I will use some thread to fill the gap. For the arbor, the thinner diameter portion of the arbor started to through before it would bit the blank.

One thing to consider is reducing the butt section diameter by inserting a stint into the butt section. On a recent fiberglass build I was able to reduce the butt diameter from .452 to .400. Around three inches of the butt section was removed and a section of fiberglass blank was inserted/bonded into the butt (similar taper). Made a large difference considering that I wanted to mount a wood reel seat insert onto the butt section. On another build, I reduced a .505 butt diameter to around .390. In this case though, I used tape arbors to match the ID of the shortened original butt section. I have no concerns about security of the reel seats mounted onto the stints.

Not exactly your situation, but it appears to me using a stint would allow you to reduce the diameter of the butt where the fighting butt will be mounted. Thereby reducing the amount of material you'd need to remove.

"The greatest barrier to discovery is not ignorance, it's the illusion of knowledge" - Daniel J. Boorstin

You still have to slide the grip down over the existing butt to get it to the stent. So that wouldn't likely help by much, unless you just wanted to remove the tenon, then shim and install a cap on the stent from behind the grip. Which would sort of negate the reason for needing the stent in the first place since you could do the same thing right on the existing blank.


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I use the Matagi Aluminum butt-cap from VooDoo Rods on the CFX casting grips. The outside diameters match down to the hundredth of an inch. They look much better than the foam cap to my eye. I've gotten very thin on the tenon, but have yet to go through or split. I've been prepared to just cut the tenon-off if this were to occur. The inside diameter of the Matagi cap is just slight over .6 inches. Leave .30 or slightly less of blank sticking out past what would then be the bottom of the grip (the depth of the Matagi mortise). Cut fiberglass drywall tape to that width. A couple of rounds will likely get you to .6 inches. Epoxy the cap on and enjoy.