correct ratio for adding milled fibre to epoxy?

[Amanwhocan]

Hi peeps
Please can someone tell me the correct ratio for adding milled fibre to epoxy (for fillets) ?
Thanks
... Kev

 

[dixontj93060]

You don't need much. The milled fiber will provide a matrix to strengthen the fillet. Really typically want a lighter additive like fumed silica for sanding.

 

[Steve Shannon]

I agree, you just want a pinch, otherwise you end up with something like the worst furball your cat ever hacked up. Carbon pulp or chopped fiberglass AIDS strength, but makes it harder to get a smooth fillet. If you want something that adds strength and finished off nicely silica, like West Systems, works well. I just learned about the 406 from a post by John Coker the other day here on TRF. I always used 404, I think.


[emoji1010] Steve Shannon [emoji1010]

 

[RocketFeller]

On the package (can't remember the brand offhand) of my milled fiberglass it says to add 1/4 to 1/2 teaspoon per ounce of epoxy. I tend to go for the higher end. I actually think that the fiber improves the consistency of the epoxy somewhat. Warming your fillets with a heat gun or hair drier will give them a nice glassy finish and speed cure time.

 

[markkoelsch]

Or be a rebel and go to a higher amount of fiber, smooth it the best you can, and then use an epoxy based filler for sanding/finishing.

 

[cwbullet]

I add a small amount of chopped CF. If I need it thicker, I add something else to the CF epoxy mixture.

 

[dixontj93060]

I agree, you just want a pinch, otherwise you end up with something like the worst furball your cat ever hacked up. Carbon pulp or chopped fiberglass AIDS strength, but makes it harder to get a smooth fillet. If you want something that adds strength and finished off nicely silica, like West Systems, works well. I just learned about the 406 from a post by John Coker the other day here on TRF. I always used 404, I think.


[emoji1010] Steve Shannon [emoji1010]

Just to clarify I believe the OP is talking about milled fiberglass (typically pieces of 1/32" or less). Fiberglass 1/4" to 1/2" doesn't ball up. Only issue with matting is carbon fiber strands (even those as short as 1/8" are a problem). The milled fiberglass will increase the viscosity a little bit--only a minor issue and often desired.

 

[JohnRE]

Depends on the job... Ketchup, Mayonnaise or Peanut butter

https://www.westsystem.com/ss/fillers-and-additives/

 

[DEmery]

Hi peeps
Please can someone tell me the correct ratio for adding milled fibre to epoxy (for fillets) ?
Thanks
... Kev

If it is milled fiberglass, I just add until it is the viscosity I want. I often add a tablespoon or more to the usual West/Aeropoxy pump system volume. If it is fiber you are cutting yourself, that makes for some pretty lumpy epoxy.

Dale

 

[DEmery]

This is the stuff I am referring to.

Dale

 

[AlfaBrewer]

Enough, but not too much. Too much and the epoxy will kick on you and set up before you can even finish stirring.

I aim for a heavy 1/2 tsp per ounce of epoxy, on the rare occasions I use it. I used it once for fillets, and had a helluva time sanding them. Now I use SuperFil for fillets (and nosecones). Really nice stuff.

 

[Rob702Martinez]

I've used milled fibers for many things over the years...a little goes a long way, don't make too big of a batch for no reason, weight your mix ratio out and add it at 8-15% by weight for added strength, or 15-25% by weight for fillets or the like. I found that using the 20%-45% range is better used with slow set high quality epoxy like Aeromarine 300/21 and some heat here and there, rather than the 10-30 min kwik epoxies. I typically weight in ounce.... or gram if needed for small batch.
Weigh part A write it down and zero out the scale, Slowly weigh part B to required ratio (2:1, 1:1 etc.) Do your math, write down total and add to that number.

Use a digital scale you can find at the smoke shop, they actually have quite the selection.

Rarely do I not add it to my epoxy, the only time I don't use it is if I am laminating a tube or using rocketpoxy.