Using Kevlar instead of cleats for crack repair.

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Mario Kessels
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Joined: Sun Sep 16, 2012 7:03 am
Location: Deurne netherlands
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Using Kevlar instead of cleats for crack repair.

Post by Mario Kessels »

Helo everybody,

hope you are all healthy where ever you are!
I used some kevlar on my last build (Classical) as reinforcement for the inside. Very easy to apply, and extremely strong of course. It comes in very thin woven sheets.
I have always used cleats for crack repair, like most have been doing for hundreds of years.
What is yours opinion in using something like this kevlar for reinforcing the inside??
For this repair it is a top crack about 15 cm long.
Let me know if you have seen it before, ised it yourself, and what you think of it. I think the pros would be:
It is string as hell, meaning that crack will never crack again. It is light, and since it's light and flat it might have less influence on the sounboard than 'point masses' like the cleats. But that is just assumption.
The cons would be for one that it's a one shot repair. You will never be able to get it off again, and might influence any future repairs.

Anyway, interested in your opinion!

all the best, Mario

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Barry Daniels
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Joined: Thu Jan 05, 2012 10:58 am
Location: The Woodlands, Texas

Re: Using Kevlar instead of cleats for crack repair.

Post by Barry Daniels »

Kevlar would have little bending resistance so an applied pressure could still cause a crack.
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Brian Evans
Posts: 900
Joined: Sat Aug 30, 2014 8:26 am
Location: Tatamagouche, Nova Scotia

Re: Using Kevlar instead of cleats for crack repair.

Post by Brian Evans »

I've used fiberglass cloth, very light, applied with epoxy, when building. I cracked an archtop top plate before the box was closed, and since I was using the FB cloth and epoxy to reinforce the F-holes, and the crack was from one of the F-holes to the top edge, I just extended the reinforcement. Worked fine, since I forgot about until now. I rarely work with kevlar only because I don't need things to be bullet proof, and I hate buying the special shears you need to cut it.

Clay Schaeffer
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Joined: Fri Jan 06, 2012 12:04 pm

Re: Using Kevlar instead of cleats for crack repair.

Post by Clay Schaeffer »

"The cons would be for one that it's a one shot repair. You will never be able to get it off again, and might influence any future repair"

Hi Mario,
I think for me that might be the biggest argument against using it. If you want to do long thin continuous "cleats" the TJ Thompson technique might be better. With a little effort I'm sure a person could bodge together something similar to the commercial offering.
https://www.stewmac.com/video-and-ideas ... video.html

Steven Smith
Posts: 193
Joined: Fri Jan 06, 2012 5:01 pm
Location: East Tennessee

Re: Using Kevlar instead of cleats for crack repair.

Post by Steven Smith »

For a similar type of reinforcement I have used linen and hide glue. I prefer something that can be reversed unless I am working on a cheap Chinese guitar. I still put cleats on cracks for the reason that Barry stated.

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