New Material Recommendation

[Mike Hutchison]

This is too simple a topic for this board but does not fit as well on any of the others.
I have been using JB Weld for a few years and it has done fairly well in terms of strength for
repair and in filling in and around gaps in fabrications, etc. However the stuff does not lend
itself to being smoothed out or "mini-troweled" to give it a semi-finished appearance which can
then be sanded or ground. I have tried waiting a little while before attempting to work it but that
tends to shift a mound over in direction of tooling. In that case, when sanding the dried JB Weld you
have to take so much off to remove ledges at the edge of applied material you have possibly removed
enough to compromise the application. If you try to work it wet, you get swirls when you lift the
tool (beveled stick) like on top of an ice cream cone. Does anyone know of an epoxy with good strength characteristics that can be worked towards a smooth surface in preparation for final sanding and paint?

[Lee Schierer]

I like PC-7. You mix what you want, it has a good working time and best of all you can "tool it" with a wet finger tip before it sets up. You can also file it or even plane it once it cures.
424736

[Jim Koepke]

One trick my dad showed me to get a smooth surface on products like JB Weld and other epoxies is regular old scotch tape.

After the compound dries the adhesive on the tape acts like a release material.

jtk

[Mike Hutchison]

Lee and Jim
Thanks for your info
Since I still have JB Weld on hand and need to do a little patching on
a current small metal project, will try the scotch tape trick first.
Will also check local availability of the PC-7.

[Jim Koepke]

Mike, if you can, post pictures. There are likely others who will appreciate knowing and seeing the results.

jtk

[Lee DeRaud]

If you try to work it wet, you get swirls when you lift the
tool (beveled stick) like on top of an ice cream cone.Use one of those flexible plastic trowels like you'd use for Bondo. I fixed a divot in a black laminated counter top, and it was perfectly smooth when it dried.

[Bill Dufour]

Use one of those flexible plastic trowels like you'd use for Bondo. I fixed a divot in a black laminated counter top, and it was perfectly smooth when it dried.


A plastic fast food spoon or knife should work. And no cleanup. California is slowly banning plastic straws. Now you have to ask for straws, by state law. Any one seen a paper straw in the last twenty years?

[Lee DeRaud]

A plastic fast food spoon or knife should work. And no cleanup.Been there, tried that: not flat, curved edges, non-flex. Yup, three-way fail.

[Carlos Alvarez]

Packing tape or even wide painter's tape works great for these cases.

[Kev Williams]

My favorite epoxy is Marine Tex, incredibly strong stuff. When it's set, my pneumatic needle scaler won't even scratch it. I accidentally got some of it on my eyeglass frames last June, I got the big chunks off but what's still there I keep trying to pick it off with my fingernails, but can't. Knife, maybe, but I wouldn't bet on it ;)
425043

BUT, like other good epoxies, troweling it smooth is not going to happen with typical tools. In fact, I'd be suspect of an epoxy that DID trowel smooth; it if doesn't stick to the putty knife, is it going to stick to my <project>? A squeegee made from a piece of Teflon or HDPE MIGHT work, but I've never tried, as I've never really needed a smooth finish. I like the scotch tape idea, plastic wrap would also likely work. What I might try would be some 'Press N Seal', it's thicker than typical wraps, would be easier to work with...

[Tom M King]

If you babysit it, you can trim it with a paring chisel, and even finish with a card scraper, but you have to catch it at just the right stage. It saves a Lot of sanding. Cheap chisels work fine if you can get it really sharp. I used to have a boat repair business, and the shop had an oversized AC system. I'd quickly cool it down to mid '60's to do fiberglass work, and then turn it back up to normal when the layup was finished.

The motorboat repair guys here on the lake tell me that there are many cracked blocks still operating with the cracks "repaired" with MarineTex. I use it for some things too.