Epoxy fairing

[mogmog2]

Not sure where to post this and hope it's ok: I'm looking to use boat materials on a mild steel sculpture I'm making - a structure analogous to a steel boat, not least as it will be painted with a 10 year+ marine paint system (probably Jotamastic and Hardtop HB) so I thought you lot would have some experience.

I have some pinholes in my welds (non-structural and I have ground & filled extensively, just thought these were small enough to fill) and some fairing to do which comprises the odd grinder scuff on a flat surface as shown in the pic, and perhaps making the the all the external corner radii more consistent. I was thinking that an epoxy compound would be appropriate.

I haven't found an off-the-shelf ultra fine compound and it therefore looks like I need to mix my own.
I have some fumed silica, but I understand that is to increase viscosity rather than as a filler? As I understand it, microballoons leave micro craters which leads me to talc.

Has anyone got any experience or recommendations for very fine fairing - ready-mixed, general tips or a recipe?
Many thanks.

 

[Tranona]

International Watertite for ready mixed (actually 2 component) or a lightweight fairing filler powder for adding to your own epoxy mix will do the job. Latter available from epoxy suppliers and if you have epoxy already probably the easier solution.

 

[Lon nan Gruagach]

Micro balloons are just that, micro. The finish is smooth as a baby's bum. Since you will be coating the whole thing after fairing, you won't see the difference. Only snag is going to be that the fairing compound will sand down much faster than the surrounding metal. It's going to be very hard to avoid shallow dips.
What volume of filler do you need? Is chemical metal going to be too expensive?

 

[mogmog2]

International Watertite for ready mixed (actually 2 component) or a lightweight fairing filler powder for adding to your own epoxy mix will do the job. Latter available from epoxy suppliers and if you have epoxy already probably the easier solution.

Thanks. I normally don't go for ready made products, but have no epoxy at present & will shortly be ordering some stuff so could add this.

Micro balloons are just that, micro. The finish is smooth as a baby's bum. Since you will be coating the whole thing after fairing, you won't see the difference. Only snag is going to be that the fairing compound will sand down much faster than the surrounding metal. It's going to be very hard to avoid shallow dips.
What volume of filler do you need? Is chemical metal going to be too expensive?

Thanks for the heads up about the microballoons - I had read somewhere about the micro-craters, which is partly why they offer other fillers? The West blurb also states "Epoxy thickened with Microlight feathers to a fine edge", which the microballoons doesn't say.
Like most things, it's all relative. Smooth as a baby's bum sounds smooth enough to me, especially as it'll be rollered or roll & tip.

Chemical metal might do, but I thought epoxy's superior sticking power might be better given the thinness/fineness of application in most areas. 560ml from Halfords is only £13 so a possibility for the edges althouhgh it is polyester based so not sure.

I don't see the sanding differential as a problem as it'll mostly be filling depressions, where the surrounding metal is the datum The edges I can just build out then sand back to whatever profile I decide as I have already ground these back to neat but variable corners.
Thanks

 

[Brent Swain]

Shining a light along the hull in the dark will show you where the humps and hollows are.

 

[solent clown]

if it is just a sculpture and not to be immersed full time in water, why not just use a decent car body filler and paint? Cheap, and made for that job. A thin skim of good filler over the thing, sand back to shape, a guide coat of paint to do the fine shaping, then paint

 

[mogmog2]

Fair point. I suppose I wanted to ensure I used the best materials and epoxy sticks better and I plan on using epoxy coatings.
However, car filler is undeniably made for the job...

 

[Aja]

if it is just a sculpture and not to be immersed full time in water, why not just use a decent car body filler and paint? Cheap, and made for that job. A thin skim of good filler over the thing, sand back to shape, a guide coat of paint to do the fine shaping, then paint

,

+1 for car body filler. Quick, and as said easy to sand and shape, takes paint well.

Donald