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UG Fiddlesmith

Glueing Carbon Fiber Bowtips

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I have a carbon fiber bow that needs a new tip installed.  I have tried two-part epoxy and Cyano Acrilate and the tips peeled off like a Post it note sticker.  The original tip was white plastic and the back half disappeared unnoticed and when I proceeded to remove the remnant of the tip it came off with no difficulty.  Any clues on how to glue stuff to a carbon fiber fiddle bow?  Thanks 

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How did you prepare the gluing surfaces?

I filed the surface to remove old glue, scored the head with a knife, scored the tip, placed in a jig to hold it stable, mixed the epoxy and applied it, clamped it.  Ditto for the the CA and accelerator.

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David may be right, most epoxy failures are relates to surface prep.

 

If there is some sort of wax or oil before you've filed it you may have filed the wax/oil into the surface.

 

Always clean with acetone and color free paper towels twice first, than file or sand, wet sanding 80 grit is what West Systems usually mentions....

 

There may have been some amine blush left from the previous epoxy also, need to be removed, see quote below. Amine blush is no good for adhesion.

 

Once cleaned water sanded 80 grit, clean again with acetone and paper towel, wait for full evaporation - you can heat the surface a bit - epoxy once heated near 100ºC, 120ºC starts to gel and once cooled it will return to it's original condition, it may help adhesion.

 

Apply a thin coat of epoxy resin without any fillers to both surfaces, and than if you need "space filling" apply thickened epoxy - the strongest I've tried has been 10% graphite (to the epoxy amount) and the rest needed of silica.

 

I am not a maker....but have to deal with epoxy bonding in a daily basis.....hope it helps some.

 

Checkout these sites for great epoxy info.

 

http://www.epoxyworks.com/

 

http://www.westsystem.com

 

From Westsystems website:

 

Special preparation for various materials

 

 

Cured epoxy- Unless you're using WEST SYSTEM's blush-free 207 Special Clear Hardener, amine blush may appear as a wax-like film on cured epoxy surfaces. It is a by-product of the curing process and may be more noticeable in cool, moist conditions. Amine blush can clog sandpaper and inhibit subsequent bonding, but this inert substance can easily be removed.

To remove the blush, wash the surface with clean water (not solvent) and an abrasive pad, such as Scotch-brite 7447 General Purpose Hand Pads. Dry the surface with paper towels to remove the dissolved blush before it dries on the surface. Sand any remaining glossy areas with 80-grit sandpaper. Wet-sanding will also remove the amine blush. If a release fabric is applied over the surface of fresh epoxy, amine blush will be removed when the release fabric is peeled from the cured epoxy and no additional sanding is required.

Epoxy surfaces that have not fully cured may be bonded to or coated with epoxy without washing or sanding. Before applying coatings other than epoxy (paints, bottom paints, varnishes, gelcoats, etc.), allow epoxy surfaces to cure fully, then wash and sand.

 

 

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Good tips from Carlo.

Another thing which can make a night and day difference (if it wasn't mentioned in Carlo's links) is "wetting out" both surfaces with the epoxy before putting them together.

You might notice with some epoxys that when you first apply them to the surface, they sort of roll around and don't stick, or will lift from where you had already touched them to the surface. If you smear them around some until the surface is "wetted" and they no longer pull away, it will usually make a much stronger bond.

 

Edit:

I see that Carlo kind of mentioned that with his recommendation that thin epoxy be applied before "filled" epoxy. The thin epoxy does a better or easier job of wetting out the surface.

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You change it's properties when thinning, these are good articles....

 

http://www.westsystem.com/ss/thinning-west-system-epoxy/

 

http://www.epoxyproducts.com/penetrating4u.html

 

edit - it has been a while since I've read these articles, so please forgive me if I repeat stuff in them.

 

From my experience, if I want penetration and structural strength, as well as humidity protection, I work with the slowest curing epoxy I can, heat it with the heat of the sun, and heat the wood with a heat gun (by heating epoxy you also speed up the cure) - than apply and it can penetrate quite deeply.

 

I only thin in very special situations (rarely).

 

Another subject regarding epoxy - I have used as a ground for several things or as primer or paint (both pigmented), and have tried many different forms of application, my favorite has been pad printing (with gloves of course), I have done very large surfaces that way, and fast.

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Going through some stuff on pvc bonding I read this and perhaps it is a "maybe, need to test".... or someone knows if it's good?

 

Plastic—Adhesion varies. If a plastic is impervious to solvents such as ace- tone, epoxy generally will not bond to it. Soft, flexible plastics such as poly- ethylene, polypropylene, nylon and Plexiglas fall into this category. Hard, rigid plastics such as PVC, ABS, polycarbonate and styrene provide better adhesion with good surface preparation and adequate bonding area. After sanding, flame oxidizing (by quickly passing a propane torch over the sur- face without melting the plastic) can improve bonding in some plastics. It’s a good idea to conduct an adhesion test on any plastic (or any other ma- terial) that you are uncertain about.

 

quote from the enclosed WestSystems pdf

 

---edit - the plastic bit I posted because the torching may also work for cured epoxy..... ;)...it is a plastic isn't it?

Ew20_Contamination.pdf

Edited by carlobartolini

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Stay away from fast curing epoxies; they don't bond nearly as well. I would suggest Industrial Formulators G2 epoxy. In my opinion, this is one of the best and strongest quality epoxies on the market. If it's recommended for laminated aircraft propellers, you know it's got to be good.

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ha...you almost got me.... :P

 

A carbon fiber bow is a plastic bow - being that carbon fiber lamination is a carbon fiber reinforced plastic...ha  :lol:

 

http://en.wikipedia.org/wiki/Carbon_fiber

 

Wolfgang Is that man playing a Stradivari with a plastic bow? Oh, yes Constanze I am afraid so, and look they all wear the same uniform... :D... I knew the future would be strange...are you sure you know how to work that time machine back again?

 

Bill thanks for the Industrial Formulators G2 epoxy tip.

 

David thanks for the "smearing" tip, used it a few times already. (before I was usually only brushing it)

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Thanks for the replys to the question about bow tips and epoxy; I really learned that I was doing almost everything wrong and it is a miracle that any of those tips held.  It was news to me that carbon fiber was plastic-most adheasive packages say they don't bond well with plastic.  I have put quite a few plastic tips on plastic bows and expect there are more to come.  A lot of carbon fiber bows are being sold and the tips do break/come off.  Thanks again.

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