Which Thickner do you prefer...

[cs]

for mixing with epoxy? I know that it depends on what you are using it for, but go ahead and throw out your ideas.

I've used wood flour, "Q" cells, talc, & Aerosil-Cabosil. The Cabosil makes a good laminiting additive and the "Q" cells makes a good faring additive. The wood flour on the other hand seems to do both of these jobs rather well.

The talc, well I ain't figured out what it does good. It seems to be heiver than anything else but takes more to thicken the epoxy. I've not been impressed with it.

What are your recomendations & experiances?

Chad

[stan v]

Milled fiber. Super stong. Good stuff. And Cabosil.

[cs]

Stan how well does the milled fiber sand?

Chad

[George Roberts]

Cabosil makes a hard but brittle surface.

Milled Glass / Kevlar make nice wear layers. The longer fibers are stronger but lumpier.

Milled Glass / Kevlar / Carbon are nice for casting.

Wood fiber makes fillets less brittle.

Wood fiber adds the proper color for gap filling.

[stan v]

Milled fiber sands with effort. It ain't micro balloons. But, great gap filling, and strong for fastening. I use this more than anything else. I use FGCI out of Florida for epoxy. Great prices, excellent service, and epoxy that compares favorably with West. I looked at the data sheets for both products.

By the way, milled fiber mixes very easy.

[ 10-24-2002, 05:04 PM: Message edited by: stan v ]

[NormMessinger]

Milled fiber and wood flour does not thrixotropic make, that is the epoxy can still flow out of the mixture. I like to mix cabosil? with wood flour for fillets because it is a little stronger and much smoother. Smoother is irrelevant if the glass is laid on before it hardens. I've always had the idea that the fillet joint was so hell-fer-stought that fibers were unnessary.

Dave C. has his own ideas about fillers. Wheat flour, portland cement,...

--Norm

[stan v]

I read where one guy uses dirt.

[imported_Paul VandenBosch]

I like silica with a small amount of microballoons added. Makes it much easier to smooth out.

[rkrough]

I saw a guy use Portland cement as a thickner.

[Wild Wassa]

I use 3 different light weight fillers.

BoatCraft Pacific's 'sander filler', filthy looking stuff. Multi-coloured, in pinks to maroons. Multi sized grains. I'll mix it to various thicknesses, from runny through to almost dry. You can certainly see where you have applied this stuff, by the pink and red stripes and the scratckmarks and divets caused by the different grain sizes. This product needs working a lot. I surface this material with either of the two fillers below, before painting.

BCP's 'compression strength filler', pale pink in colour, mixed to a thick mayonaise like texture. Difficult to sand. This material gives a very uniform surface. I use this even as my sanding filler. Although difficult to sand, it gets the jobdone in one go, this saves time.

My favourite for fairing and finishing, Norglass's 5 micron hollow glass spheres. A joy to use on every occassion. When using the Norglass, I use a non yellowing hardener (BCP's) in the epoxy. Curing is 'very slow' when using the non yellowing hardener, unless the ambient temperature is higher than 26 oC.

None of the products above are suitable for brightwork.

I've used fine sawdust for filling on the odd job, but have given up, because of hardness alone. BCP's Epoxy and sawdust is not sandable. Too hard, this I don't understand.

Warren.

ps, Boatcraft's site is, http://www.boatcraft.com.au. Check out the Iluka Kayak in the section called 'What's New'.

[ 10-24-2002, 11:27 PM: Message edited by: Wild Wassa ]

[cs]

I think that maybe I will try the cabosil with wood flour and see how that works. I had been mixing the wood flour with talc cause I was running out of wood flour and had plenty of talc.

Has anyone used the talc? I just used it this week so I know nothing about the sanding or long term strength.

Chad

p.s. I use fillers for either laminating or filling. I hope not to ever do S&G again, so I will not be doing fillets.

[Tar Devil]

From a boatbuilding friend of mine in Alaska...

"Flour (yep, the stuff in the kitchen), or wood flour, or saw dust mixed into epoxy sets into a near bullet proof product (like breaking rocks with a sledge hammer) and a tough tough tough glue joint.
Garden lime is supposed to be the same although I haven't tried that one myself."

Hope this helps.

Later,

Phil

[mhoffman]

I have used talc (in the form of baby powder- just read the lable- some are corn starch) with good results. Its cheap, and when used with wood flour (read dust collected from my sander) you can get good coloration and smooth flowing for filling gaps and fairing.
Matt

[paul oman]

Hello:

We sell a couple of different thickers and epoxy additives (copper, graphite, teflon, etc).

Most people like the fumed silica, but microspheres work (but work like ball bearings and tend to sag). Our chopped fiber is recommended for thick patching (internal support of the epoxy). We blend the three together for 'yacht mix' - 2 parts fumed silica, one part fiber and 1 part microspheres/balloons.

I tell people for a quick tiny repair just use talc. For cement like epoxy lime powder from the garden store...

Another alternative is to purchase pre thickened epoxies and not fight with the thickeners.

paul oman
progressive epoxy polymers
www.epoxyproducts.com/marine.html (http://www.epoxyproducts.com/marine.html)

[DerekW]

I'm surprised no-one else has mentioned it; plastic mini-fibers. (Not the milled glass)

I add some to almost everything - they're more thixotropic than cabosil, and tough without being impossible to sand. Most of the time I use wood flour / mini-fibres 90 / 10. Glue lines look inoffensive and fillets are smoother than with wood flour alone, and the darned stuff stays where i put it. All my test pieces have broken in wood - the fibrous nature seems to create a tough matrix in the resin.

cheers
Derek

[capt jake]

CS On my Weekender I am using calloidal silica (fumed silica) with microballoons. Just a dash of the silica to help thicken it, fill the rest with the microballoons.

Wood flour is hard to sand. If you are asking this in regards to your Weekender, remember all of the 'little' spaces that you will have to get to to do the sanding! ;) They are a bummer to get to. smile.gif

Lay it in as neatly as you can and clean off any goobers while they are still soft.

[Mark Van]

Talc works great for final fairing, after the fiberglass cloth is on, and a few coats of epoxy, it is rough sanded, and epoxy thickened with talc is troweled on with a drywall trowel, and then it is sanded. It sands easily, and is about as hard as the straight epoxy, so it sands evenly. I have tried other fairing fillers, from micro balloons, micro spheres, and WEST system microlight, but I think talc works best.
Mark

[Ron Williamson]

I use wood flour because I always have it.
It is helpful to run lumpy fillers through a sifter before they are used.
R

[Bob Williams]

Has anybody ever tryed diatomaceous earth, Its used in swimming pool filters ? I think it is made out ground up shells

[Nicholas Carey]

Originally posted by Bob Williams:
Has anybody ever tryed diatomaceous earth, Its used in swimming pool filters ? I think it is made out ground up shellsErr...no..

Diatomaceous earth is made of fossilized diatomes. "Diatoms are unicellular algae generally placed in the family Bacillariophyceae. The cell walls of these organisms are made of silica, and the varied shapes and beautiful ornamentation of these walls made the study of the diatoms and related siliceous organisms a favored pursuit of the microscopical pioneers. The cell wall is also one of the major reasons why these algae are today a favorite tool of modern ecological and evolutionary researchers, because the fossils are often well preserved in lake and marine systems".

Here's a good starting point for more information

http://www.indiana.edu/~diatom/diatom.html

And here's a photomicrograph of a diatom:

http://www.calacademy.org/research/diatoms/images/diatom2-2b.jpg

I doubt very much that diatomaceous earth will behave significantly better than fumed silica (and perhaps worse).

but diatomaceous earth is great for killing aphids -- the sharp silica edges slice the aphid's belly -- They bleed out and die.

Wear a good dust mask if you work around diatomaceious earth, even in the garden.

[Bruce Hooke]

I know this is herasy to some folks around here but I like the range of fillers that Gougeon sells...they may be more expensive than other solutions but since it takes me years to use up a cannister of any of them it doesn't really matter that much to me. And, with Gougeon's products I can be reasonably certain that they have been tested fairly thoroughly for complete compatibility with epoxy, and they sell a range of fillers that covers most possible situations. I'm all for finding the best tool or material for the job but I don't feel any need to develop my own solution when someone else already has a good one...

[Wild Wassa]

Originally posted by paul oman:
Hello:

...microspheres work (but work like ball bearings and tend to sag). ...I normally fill 3 times (but often only once). I let the surface sag and cure well before refilling or sanding.

I'm only interested in as perfect a surface as I can put on a racing dinghy. I would fill a dozen times, if I needed to.

After 17 months (my oldest restoration of a racing hull) I see no sags. I only see more wins.

I made epoxy blocks, using the various fillers, when I first started out, including flour and sawdust, a swag of others as well and just straight epoxy. A few of them did not float. The one that was most bouyant had the hollow glass spheres added. If I remember correctly it was 100% by volume. I'm now at 100-150% by volume.

Could I suggest you do the same small experiment, if your needs are above the ordinary.

Warren.

ps, The epoxy without 'any' filler added, had the same bouyancy as a rock. The choice of filler should be selected to suit your ultimate needs. Our needs are for fairing, light weight racing hulls.

[ 10-31-2002, 11:06 AM: Message edited by: Wild Wassa ]

[capt jake]

"Flour (yep, the stuff in the kitchen), What are the thixotropic properties of flour? If it works, and is cheap. I am in need of a final fairing coat on the hull.
Thoughts? smile.gif

[cs]

capt jake for a final farring compound I think I would recomend the "Q" cells. You can sand that stuff smooth as a baby's butt with very little effort. I don't think I would use it for laminating.

Chad

[On Vacation]

Kitchen flour requires a huge amount of resin. Sanding it ?? Forget it. Like a rock.

[JJBoatman]

Have just had graphite suggested as a thickening agent on a current job, I don't know why or anything about it as an additive. Any advice or directions in which to look would be helpful and appreciated

[capt jake]

It is supposed to promote a 'slick' finish to the hull. From what I have heard, it is used in the fairing of the hull bottom and finished off with epoxy. Nice black finish, from what I have heard.

I contemplated it, though bagged the whole idea. My hull bottom is very smooth and will be painted with an LPU.

Good luck. smile.gif

[JimConlin]

I know of two uses for graphite as an epoxy additive.
It's used to provide a low-friction scuff-resistant surface. Very popular for drift boat bottoms. I've used it recently for the bottom of a dinghy and a daggerboard trunk.
The Gougeons recommend it as a colorant for the seams in teak veneer decks. I'm not sure that I prefer it to polysulfide. The black sanding dust was an awful mess.

I've heard that graphite is sold in farm supply shops as a lubricant for planting seed.