Boat Builder Central - Builder Forums

...what?

And what's it for?

https://boatbuildercentral.com/product/ ... ound-8-oz/

This stuff?

Its a blend of Phenolic Microballons and Silica Thickener, it makes a really lightweight and easy to sand fairing compound.
Different uses, but a main one is to spread it with bondo spatchula much like you would bondo, a thin layer over everything, then sand most of it off and you have a very smooth 'fair' surface ready to paint. The number of times you apply and sand off depends on your level of OCD and perfectionism and desired finish levels.

Thats what I thought plain microballoons was for.

So, is this fairing compound for vertical or upside-down surfaces? Is that why the silica is added? Is it to be mixed with more microballoons or used as is?

Whats best use on an open OB?

I wouldn't change the ratio unless you know what you are doing.

use it where ever you need. I will say that things that sand was, wear easy. keep that in mind when putting it places that wil see impact and rub wear. in those places maye consider a bit more silica or more empoxy in the mix. but we are back to the opening line.

Maybe near inside corners where its a bit harder to sand? For filling the weave?

Trying to understand why I'd choose it over microballoons. Both come in a kit.

I could be wrong, but I think the silica helps prevent sagging on heavy coats or fillets. So pure mucrobalones in thin coats and horizontal surfaces and mix for thicker vertical? I'm not sure I used the mix for everything.
Wood flower for gluing joints
Mix for fillets and fairing
Graphite for the bottom finish

Silica is harder than wood, holds shape, and doesn’t hold water. Hard as forking steel.

Balloons add volume, don’t hold shape, and leave opportunity for water intrusion. Super easy to sand… and break.

Wood adds volume and strength, allows some flex in the joint, will absorb water when exposed via sanding.

Use wood filler in areas when you need to survive flexing and will fully encapsulate the material. That’s why it’s used for “glue”.

Use balloons to gap fill when no structural integrity is needed and easy shaping is advantageous. Ex fairing. It is NOT suitable for anything that will experience shock loading/impacts with no support.

Silica is for anything that needs to be as close to metal as possible but still epoxy. Problem is you get all the disadvantages and only a few of the advantages. Hard to sand and brittle. It breaks easy it you get too much silica in the batch. If you keep it under 20% it’s like concrete with enough flex to hold bolts and screws decently.

Not sure that helps and DO NOT consider this authoritative. Try some experiments in small batches.

I use a bit of silica pretty regularly in my daily just to make things easier. Takes threading from a tap well enough to make it easier than proper tapping for my needs.

Thanks fellas.

And I misspoke. The kit I recieved had this and woodflour, so its the fairing compound. I got lotsa balloons and unopened Quikfair from last time.

Looking forward to easier sanding.

Jaysen, you said woodflour absorbs water.

In glue, only the sanded surface would, much like closed cell foam, right?

Buz wrote: ↑Thu Mar 28, 2024 6:49 pm Jaysen, you said woodflour absorbs water.

In glue, only the sanded surface would, much like closed cell foam, right?

Correct. So if you use it for glue, sand, then glass, you’ve covered the exposed wood. You can reseal with thin neat coat (warm for easy flow). Let thing is if you sand wood flour impregnated you need to seal it. But wood allows that flexibility that silica lacks.

Hope that makes sense.

Sure does. Thanks.

A few people keep saying wood flour as an additive will absorb water, but once dry wood flour is been mixed into epoxy resin I disagree- as small as those particles are, they will absorb epoxy first, and once they're saturated that's it. It's ingrained in most of us to be sensitive to the relationship between boats, wood and water ingress, so I get where the feeling comes from, but I don't think it's something to worry about in real life.