Starting Quattro 16 from Woods Design

[dewaegep]

Dear all,
I decide it, I start the construction of my Quattro 16. I will face some difficulties, the first one is that I´m not leaving in my own country (I'm in Mexico in a small island called "Ciudad del Carmen"), so I don´t have all the contacts, shops and so on to find all the supplies, and also friends with experience who can help me. Second, I will need to import a lots of things from USA, and that take long.
After studying all the information provide by Woods, my first question is:
:confused:What is COLLODIAL SILICA? How do you use it? What is his purpose? I couldn't find in the plan where to use it, but it appear in the material list.
I will, of course, give you the advance of the project via this Forum and post photos.
Thanks in advance for any help provided.

Patrick

[Hwyl]

It's a thickening agent for the epoxy, Gougeon West call it 406.

If you're completely stuck you can use sawdust, but the silica is much better

[Cuyahoga Chuck]

Colloidal Silica is a thicksatropic agent. That is, it makes epoxy thicker so it won't run out of a glue joint before the stuff kicks. There are various thickeners which are rated by strength and usage. The strongest are fibers like chopped glass and milled cotton. Medium strength is wood flour. Not sawdust but something close to sanding dust. Coll. silica, brand name Cabosil, makes for harder joints. Not good if you have to sand this stuff. Then there are weaker agents like microballoons which is used for fairing because they sand easier.

[switters]

Your boat is stitch and glue, so you will be making "fillets" of thickened epoxy on the inside of the joints.

Hope this is specific enough to let you know where you will be using it, basically all of the long seams in the hull. I am not familiar with the plans but if they didn't give you a quantity take off of the materials we can try to help. I used west for some skiffs. The micro ballons mentioned above were $12 US for a tube about a liter in volume. Making 3/8-inch fillets I manged to cover about 50-feet of seams.

Others will be along with more information now that I have been specific enough to evoke outrage:D.

Best of luck with your build hope to see your progress here on the forum.

[JimD]

WEST calls it colloidal silica, perhaps to justify charging more for what almost everyone else calls fumed silica, often sold by the names cabosil or aerosil already mentioned. Not sure why Woods calls it colloidal silica. That's their privilege, I suppose.

[Thorne]

Others will be along with more information now that I have been specific enough to evoke outrage:D.



My understanding is that microballoons should only be used to thicken epoxy used for fairing / smoothing the hull surface -- NOT for load-bearing joints. For these long joints, also called fillets, you'll want to use the silica or sawdust as a thickener..

[JimD]

My understanding is that microballoons should only be used to thicken epoxy used for fairing / smoothing the hull surface -- NOT for load-bearing joints.

Absolutely. Do NOT use microballons for joint filets. They are called balloons because they are hollow. When you mix them with epoxy you are making epoxy foam, more or less. Use the balloons for fairing and smoothing only. You need something much stronger, such as silica, for the joint filets.

[slidercat]

Jim, I've always heard the same thing, and I'm using silica for my fillets in my current project. On the other hand, I've recently wondered if most of the strength of a filleted and taped joint doesn't come from the tape, and that perhaps the fillet mostly improves the geometry of the corner the tape has to fit into. If so, you could use microballoons for fillets, as long as they will be taped. It would make finishing the interior a lot easier, and silica is truly nasty stuff to work with.

Any structural engineers want to comment?

[S B]

Jim, I've always heard the same thing, and I'm using silica for my fillets in my current project. On the other hand, I've recently wondered if most of the strength of a filleted and taped joint doesn't come from the tape, and that perhaps the fillet mostly improves the geometry of the corner the tape has to fit into. If so, you could use microballoons for fillets, as long as they will be taped. It would make finishing the interior a lot easier, and silica is truly nasty stuff to work with.

Any structural engineers want to comment?
Not a structural engineer, but silica is also a very dangerous substance, if handled improperly. Never sand with a power tool and never dry sand, always wet, to keep the dust from getting airborne.

[JimD]

Not a structural engineer, but silica is also a very dangerous substance, if handled improperly. Never sand with a power tool and never dry sand, always wet, to keep the dust from getting airborne.

I don't think fumed silica is all that bad, actually. A quick msds google for it turned up this:

Section III – Hazards Identification
Main Hazards: Dry powdered materials can build static electrical charges when subjected to friction. Proper precautions when using CAB-O-SIL (registered trade name) fumed silica in the presence of flammable or explosive gasses and liquids should be taken to prevent accidents.
Potential Health effects: Eye: May cause irritation at high dust levels
Skin: May cause drying of skin
Ingestion: None expected
Inhalation: Temporary discomfort due to inhalation of dust
Chronic: Not listed as carcinogen by IARC, NTP, Z list or OSHA
Teratology: None identified
Reproductive Info: None identified
Target Organs: Lung

Section IV – First Aid Measures
Inhalation: Not hazardous. In case of discomfort, remove exposed individual to fresh air
Ingestion: Not hazardous. No treatment required
Eyes: Immediately flush lightly with plenty of water for 15 minutes. Get medical attention
Skin: Not hazardous

[JimD]

Jim, I've always heard the same thing, and I'm using silica for my fillets in my current project. On the other hand, I've recently wondered if most of the strength of a filleted and taped joint doesn't come from the tape, and that perhaps the fillet mostly improves the geometry of the corner the tape has to fit into. If so, you could use microballoons for fillets, as long as they will be taped. It would make finishing the interior a lot easier, and silica is truly nasty stuff to work with.

Any structural engineers want to comment?

I think tape over balloon filets might just be a waste of tape. I've also built a couple kayaks with tape on the outside and no filet on the inside. They have not seemed to suffer by it.

[S B]

I don't think fumed silica is all that bad, actually. A quick msds for it turned up this:
Last I heard, Silicosis was still a killer. The finer the particle the more reactive the silica. I have been collecting MSDS on silica compounds for many years, first time I have seen one not warning of, long term, inhalation problems. Perhaps it isn't one, I wouldn't take the chance.

[Bill Huson]

I'm starting a Woods design Pixie 14, and I have the plans for a Quattro as well. The instructions call for fillet mix to be made with microballoons and enough thickener (collidial silica et al) to keep the goo from creeping. WEST has two fillet mixes, high density and low density. Woods specifies which one to use for which fillet.

It is true that Microfibers create the strongest fillet, but for the beach cats microballoons are just fine. You have thin plywood joined with a microballoon fillet and taped inside and out. I gaurentee the wood will destruct before that joint does. My prior experiance is building outboard hydros. An 80+ pound 9 1/2 foot hull powered witha screaming (close to 9K rpm) outboard and doing 65+ mph and I never had a microballooon fillet fail.

[slidercat]

I just looked it up, and Jim D. is correct about the non-dangerous quality of fumed or amorphous silicas like Cabosil. Apparently silicosis is only associated with the crystalline forms of silica. In other words, my cheap potter's silica is not good for my lungs, despite its vastly cheaper price. I wonder why this crucial difference has not been made plainer by the manufacturers of these products? Seems like a really good selling point. Silicosis is a terrible disease that might eventually kill me, since I've been a potter all my adult life.

[switters]

Ah, good stuff, I should have added that I taped the outside of the fillets and used the micro balloons on the inside to fill the joit and keep the inside smooth for clean-out.

[S B]

I just looked it up, and Jim D. is correct about the non-dangerous quality of fumed or amorphous silicas like Cabosil. Apparently silicosis is only associated with the crystalline forms of silica. In other words, my cheap potter's silica is not good for my lungs, despite its vastly cheaper price. I wonder why this crucial difference has not been made plainer by the manufacturers of these products? Seems like a really good selling point. Silicosis is a terrible disease that might eventually kill me, since I've been a potter all my adult life.
Let's hope potter's rot has not set in, for either of us.