Re: [bolger] Re: Epoxy Pot Life

Thanks, Harry, that's good to know. I've added a couple more epoxy charts
to the "How-To" folder:

http://groups.yahoo.com/group/bolger/files/How%20To/

On Tue, 21 Jun 2011 20:50:23 -0700, Harry J wrote:

> The ratio for Raka 2-1 epoxies is 100 to 43 by weight.

--
John (jkohnen@...)
Anyone can do any amount of work, provided it isn't the work he
is supposed to be doing at that moment. (Robert Benchley)

The ratio for Raka 2-1 epoxies is 100 to 43 by weight.

HJ

On 6/21/2011 6:47 PM, John Kohnen wrote:
> A clever gizmo, Joe. I've been using an electric scale from Harbor
> Freight. Mixing by weight seems much easier and more fool proof for me
> than mixing by volume. Some epoxies use a different ratio for weight and
> volume, so check that out first. For instance System Three uses .44 ounces
> of hardener for each ounce of resin by weight, .5 ounce of hardener per
> ounce of resin by volume. I made a couple of charts for the epoxies I use
> so I won't get confused. Like this one for System Three:
>
>http://preview.tinyurl.com/6yfntym
>
>http://groups.yahoo.com/group/bolger/files/How%20To/
>
> Zero the scale with your cup on it, add the desired amount of resin (any
> weight unit as long as you don't change it before you add the hardener),
> and then add enough hardener to reach the "Total" weight.
>
> If there's a restaurant supply store near you, the squirt bottles used for
> ketchup, fry sauce, and whatever make good containers for resin and
> hardener. You can easily squirt just a little tiny bit when you're making
> small batches, or quite a bit for bigger amounts. The Curtis Restaurant
> Supply store near me has a good selection of sizes:
>
>http://www.curtisequipment.com/
>
> On Mon, 20 Jun 2011 22:26:16 -0700, Joe T wrote:
>
>> Some newer members may not have seen my Epoxy Ratio Scale article in
>> Duckworks:
>>
>>http://www.duckworksmagazine.com/05/articles/scale/index.cfm
>>
>> Tom H. suggested and improved pivot, using two screws down through the
>> board.

A clever gizmo, Joe. I've been using an electric scale from Harbor
Freight. Mixing by weight seems much easier and more fool proof for me
than mixing by volume. Some epoxies use a different ratio for weight and
volume, so check that out first. For instance System Three uses .44 ounces
of hardener for each ounce of resin by weight, .5 ounce of hardener per
ounce of resin by volume. I made a couple of charts for the epoxies I use
so I won't get confused. Like this one for System Three:

http://preview.tinyurl.com/6yfntym

http://groups.yahoo.com/group/bolger/files/How%20To/

Zero the scale with your cup on it, add the desired amount of resin (any
weight unit as long as you don't change it before you add the hardener),
and then add enough hardener to reach the "Total" weight.

If there's a restaurant supply store near you, the squirt bottles used for
ketchup, fry sauce, and whatever make good containers for resin and
hardener. You can easily squirt just a little tiny bit when you're making
small batches, or quite a bit for bigger amounts. The Curtis Restaurant
Supply store near me has a good selection of sizes:

http://www.curtisequipment.com/

On Mon, 20 Jun 2011 22:26:16 -0700, Joe T wrote:

> Some newer members may not have seen my Epoxy Ratio Scale article in
> Duckworks:
>
>http://www.duckworksmagazine.com/05/articles/scale/index.cfm
>
> Tom H. suggested and improved pivot, using two screws down through the
> board.

--
John (jkohnen@...)
One cat just leads to another. (Ernest Hemingway)

Some newer members may not have seen my Epoxy Ratio Scale article in Duckworks:

http://www.duckworksmagazine.com/05/articles/scale/index.cfm

Tom H. suggested and improved pivot, using two screws down through the board.

Joe T

--- Inbolger@yahoogroups.com, "Christopher C. Wetherill" <wetherillc@...> wrote:
>
> Yesterday I mixed 3/4 cup of MAS epoxy with slow hardener. My container
> was a PETE peanut butter jar. The ambient was about 80F. It kicked in
> about 1/2 hour. Fortunately, I was sticking on the butt plates for the
> panels of the Payson's Pirogue and I was finished before the event. I
> am curious, however, about the behavior with silica mixed in for doing
> the fillets. Will the silica slow the reaction down? It won't
> appreciably increase the surface area, but it will lower the unit mass
> of epoxy.
>
> V/R
> Chris
>

I found that using shallow containers was much better for keeping the epoxy from kicking off too quickly. I would mix in paper cups, then pour to a shallow plastic container that could be reused numerous times by simply flexing the container and dumping out the solid mass of leftover resin. For filling the weave, I used slightly larger trays like paint tray liners. these too could be reused and recycled.

My preference was for trays of Green Giant frozen beans with cranberries. I got 4-5 uses from each tray.

I also used flexible plastic spreaders like the WEST type. I still have all of them from the Clam Skiff build.

David Jost

--- Inbolger@yahoogroups.com, "Christopher C. Wetherill" <wetherillc@...> wrote:
>
> Yesterday I mixed 3/4 cup of MAS epoxy with slow hardener. My container
> was a PETE peanut butter jar. The ambient was about 80F. It kicked in
> about 1/2 hour. Fortunately, I was sticking on the butt plates for the
> panels of the Payson's Pirogue and I was finished before the event. I
> am curious, however, about the behavior with silica mixed in for doing
> the fillets. Will the silica slow the reaction down? It won't
> appreciably increase the surface area, but it will lower the unit mass
> of epoxy.
>
> V/R
> Chris
>

I've recently been working with SP106 epoxy (fast hardener), putting some strength back into the foredeck of my Express Pirate plastic sailing yacht (the 30 year old plywood stiffeners were mostly mush, now replaced with foam and a new ply backing plate for the foredeck cleat). Not a nice job, working on my back with my head stuffed up the end of the v-berth (despite taking all possible precautions, I still managed to get a fair amount of drips on me, including an incident where I glued my Norfolk Wherry Trust baseball cap to my forehead - one of the few times in life when I've really appreciated being bald).

Anyway, I found that for quantities up to 100g, mixed in a wide, flat aluminium container (as used to hold curry from our local take away), the quoted pot life and working time were reasonably accurate (15 and 45 minutes respectively, IIRC). Mixing more than that at once (the most I did was about 200g) caused enough heat to build up that the resin was turning to jelly in the container within about 5-10 minutes, and after I'd slathered it into place (risking burnt fingers as I did so) the working time was closer to 10-20 minutes. I didn't mix any large amounts with additives (I was using chopped strands and microfibres rather than silica), so don't know how they'd have affected things. I'd guess as they provide a mass to act as a heat sink, and divide up the epoxy somewhat, they'd reduce the rate of the runaway exothermic reaction.

Dan (who would write more, but I've got a five year old to persuade that it's bed time).

On 19/06/2011 19:27, Christopher C. Wetherill wrote:

 

Yesterday I mixed 3/4 cup of MAS epoxy with slow hardener.  My container was a PETE peanut butter jar.  The ambient was about 80F.  It kicked in about 1/2 hour.  Fortunately, I was sticking on the butt plates for the panels of the Payson's Pirogue and I was finished before the event.  I am curious, however, about the behavior with silica mixed in for doing the fillets.  Will the silica slow the reaction down?  It won't appreciably increase the surface area, but it will lower the unit mass of epoxy.

V/R
Chris