I've got a cylindrical cavity about 1.25" in diameter and 1.5"
deep that I plan to plug with a cylinder of styrofoam that's
slightly smaller in diameter.

West System resin and 206 hardener plus a little 403 adhesive
filler and/or some chopped-up fiberglass.

Smear the inside of the cavity with the mix, making sure there's
enough at the bottom to smooth over any irregularities, smear
the plug, pour some of the mix in to the cavity, moosh the plug
down until the mix overflows the edges and the plug won't go down
any further, and let it harden - trimming jelled resin as
possible/convenient.

My concern is that in that confined space, the resin will go off
too hot and melt the plug and/or the surrounding styrofoam.

Is this a legitimate concern? If so, how far can I depart from
5:1 and still be sure the stuff will harden?
--
PeteCresswell

"(PeteCresswell)" wrote in message
...
I've got a cylindrical cavity about 1.25" in diameter and 1.5"
deep that I plan to plug with a cylinder of styrofoam that's
slightly smaller in diameter.

What is the purpose of using epoxy with styrofoam?

Sounds like a waste of good epoxy to me.

Lew

On Oct 10, 8:34 pm, "Lew Hodgett" wrote:
"(PeteCresswell)" wrote in message

...

I've got a cylindrical cavity about 1.25" in diameter and 1.5"
deep that I plan to plug with a cylinder of styrofoam that's
slightly smaller in diameter.

What is the purpose of using epoxy with styrofoam?

Sounds like a waste of good epoxy to me.

Lew

Been there, done that, it works. I would not worry about melting the
styro.

On Wed, 10 Oct 2007 20:18:27 -0400, "(PeteCresswell)"
wrote:

I've got a cylindrical cavity about 1.25" in diameter and 1.5"
deep that I plan to plug with a cylinder of styrofoam that's
slightly smaller in diameter.

West System resin and 206 hardener plus a little 403 adhesive
filler and/or some chopped-up fiberglass.

Smear the inside of the cavity with the mix, making sure there's
enough at the bottom to smooth over any irregularities, smear
the plug, pour some of the mix in to the cavity, moosh the plug
down until the mix overflows the edges and the plug won't go down
any further, and let it harden - trimming jelled resin as
possible/convenient.

My concern is that in that confined space, the resin will go off
too hot and melt the plug and/or the surrounding styrofoam.

Is this a legitimate concern? If so, how far can I depart from
5:1 and still be sure the stuff will harden?


As a general statement, do not deviate from the recommended mixing
ratios for epoxy. In the past I did quite a number of tests with
various brands of epoxy, varying the ratio of resin/hardener, and
invariably the strongest bond resulted from using the ratio
recommended by the maker.

If any load at all may be placed on this repair I would strongly
recommend several layers of cloth over the top of the repair as epoxy
is rather brittle and styrofoam crushes very easily.


Bruce in Bangkok
(brucepaigeATgmailDOTcom)

"(PeteCresswell)" wrote
I've got a cylindrical cavity about 1.25" in diameter and 1.5"
deep that I plan to plug with a cylinder of styrofoam that's
slightly smaller in diameter.

I missed how small this repair is the 1st time around.

I'd make the repair directly using fairing putty and get on with it.

You can eyeball a 1 oz serving of mixed epoxy.

I use 1 oz serving cups sold in restaurant supply shops for this task.

Mix up 1 oz of epoxy, then transfer to a larger container (Paper
coffee cups work for me) and thicken with micro-balloons.

If this is a thru hole, cover the bottom with duct tape, then apply
about 1/2"-3/4" of fairing putty in the bottom of the hole and trash
the rest of the fairing putty.

Wait 24 hours, then repeat.

Continue until putty is proud on both sides.

Allow 36 hiurs to cure, then sand flush.

At the outside, you will use 3 oz of mixed resin and a 1/2 cup of
microballoons.

The trick is to remember that a 1/2"-3/4" coat of fairing putty is maz
or it will go exothermic.

Lew

On Oct 10, 8:18 pm, "(PeteCresswell)" wrote:
I've got a cylindrical cavity about 1.25" in diameter and 1.5"
deep that I plan to plug with a cylinder of styrofoam that's
slightly smaller in diameter.

West System resin and 206 hardener plus a little 403 adhesive
filler and/or some chopped-up fiberglass.

Smear the inside of the cavity with the mix, making sure there's
enough at the bottom to smooth over any irregularities, smear
the plug, pour some of the mix in to the cavity, moosh the plug
down until the mix overflows the edges and the plug won't go down
any further, and let it harden - trimming jelled resin as
possible/convenient.

My concern is that in that confined space, the resin will go off
too hot and melt the plug and/or the surrounding styrofoam.

Is this a legitimate concern? If so, how far can I depart from
5:1 and still be sure the stuff will harden?
--
PeteCresswell

Do not vary the ratio provided by the manufacturer. Epoxy is not like
poly where you can "heat" a batch with more hardner. On a molecular
level, and in laymans terms, epoxy molecules need to individually
connect to a hardner molecules to react and finish. If you say use 20%
less hardner, you will in theory have a mixture of which 20% will
never cure... in laymans terms...

Per :
Do not vary the ratio provided by the manufacturer. Epoxy is not like
poly where you can "heat" a batch with more hardner. On a molecular
level, and in laymans terms, epoxy molecules need to individually
connect to a hardner molecules to react and finish. If you say use 20%
less hardner, you will in theory have a mixture of which 20% will
never cure... in laymans terms...

That's totally new to me. I had been thinking of it in terms of
being a catalyst.

Thanks.
--
PeteCresswell

(PeteCresswell) wrote:
Per :

Do not vary the ratio provided by the manufacturer. Epoxy is not like
poly where you can "heat" a batch with more hardner. On a molecular
level, and in laymans terms, epoxy molecules need to individually
connect to a hardner molecules to react and finish. If you say use 20%
less hardner, you will in theory have a mixture of which 20% will
never cure... in laymans terms...


That's totally new to me. I had been thinking of it in terms of
being a catalyst.

Thanks.

It's not.

The freak told you true...

Per Frogwatch:
Been there, done that, it works. I would not worry about melting the
styro.

Just did it. Stuff has pretty much gone off and, as you say, no
problems.

Which begs a question:
Given an area about 3" in diameter that I will glass over -
feathering from the edges into the 1" hole in the center -
intuitively it seems like I should layer the glass with a small
patch in the center first, a larger patch over it, and so-forth
until the last patch covers the entire area instead of
vice-versa.

Seems like I'm aiming for a situation where, as much as possible,
I've got a single contiguous hunk of glass over the whole thing.

Does this sound logical?

I ask because I can twist it around and rationalize the opposite
too...
--
PeteCresswell

(PeteCresswell) wrote:
Per Frogwatch:

Been there, done that, it works. I would not worry about melting the
styro.


Just did it. Stuff has pretty much gone off and, as you say, no
problems.

Which begs a question:
Given an area about 3" in diameter that I will glass over -
feathering from the edges into the 1" hole in the center -
intuitively it seems like I should layer the glass with a small
patch in the center first, a larger patch over it, and so-forth
until the last patch covers the entire area instead of
vice-versa.


You were correct the first time.
Try not to leave exposed edges.


Seems like I'm aiming for a situation where, as much as possible,
I've got a single contiguous hunk of glass over the whole thing.

Does this sound logical?

Yes.

I ask because I can twist it around and rationalize the opposite
too...

Don't.