Quick-cure Epoxy

To All:

There are times when you need to put something together fast, often
while HOLDING the parts in positionby HAND, such as when you are
making a jig or fixture. Many times the fixture is made of whatever
wood you happened to have available.... 'good' scrape, if you know
what I mean. But the jig or fixture itself is NOT scrap -- you want
it to hold up, often for a span of YEARS. That's when you reach for
whatever quick-curing EPOXY you happen to have on hand.

I've previously mentioned that I use several different adhesives,
selecting them according to need, cost, availability, temperature and
so on. STRENGTH is never an issue since ALL modern adhesives are
stronger (in shear) than the softwoods normally used to build an
airplane (or even a jig :-)

If you will go to...
http://search.harborfreight.com/cpis...?keyword=epoxy...
....you will see several epoxies, including Item# 65048 and Item#
92665. The latter is often on sale for 99cents and is super-simple to
use, thanks to its 1:1 mixing ratio.

If you remember to apply the adhesive to BOTH surfaces... and give
them a couple minutes of 'open' time, they even work on hardwoods.

Don't take my word for any of this. Do your own tests and base your
opinion on that.

--------------------------------------------------------------------------

If you've done any composite work at all, you're probably familiar
with 'ice cream' sticks. Retailers call them 'mixing' sticks, 'hobby'
sticks and so on, and they often turn up in the Toy Dept... so if the
clerk gives you that blank look and sez they don't carry anything like
that, don't take it as gospel.

Tongue depressors fall into the same category and those which fall out
of date can usually be found for sale as new-surplus, from such
outfits as American Science & Surplus. (A tongue depressor is just a
BIG 'ice cream' stick.)

I don't know what these sticks are made of; birch or poplar at a
guess. But it's a dense hardwood that works very well as 'curbing'
around metal fittings. That is, with the fitting in place, you
prepare a hardwood 'curb' around the fitting. Do a proper job of it
and the 'curbing' will provide such a grip on the fitting that it
serves to hold the fitting in place, allowing you to drill the holes
for the fasteners. A fast-curing epoxy such as those mentioned above
appears to be the ideal adhesive for this kind of work.

-R.S.Hoover

On Mon, 22 Dec 2008 13:12:08 -0800 (PST), "
wrote:


Tongue depressors fall into the same category and those which fall out
of date can usually be found for sale as new-surplus, from such
outfits as American Science & Surplus. (A tongue depressor is just a
BIG 'ice cream' stick.)

I don't know what these sticks are made of; birch or poplar at a
guess. But it's a dense hardwood that works very well as 'curbing'
around metal fittings. That is, with the fitting in place, you
prepare a hardwood 'curb' around the fitting. Do a proper job of it
and the 'curbing' will provide such a grip on the fitting that it
serves to hold the fitting in place, allowing you to drill the holes
for the fasteners. A fast-curing epoxy such as those mentioned above
appears to be the ideal adhesive for this kind of work.

-R.S.Hoover

ice cream sticks are made from strong non aromatic woods so that they
dont taint the food product or break while in use.
in australia all that I am aware of are made from queensland hoop
pine.
in america I'd bet that your ice cream sticks are made from grade 2
spruce.
Stealth Pilot

"Stealth Pilot" wrote in message
...
On Mon, 22 Dec 2008 13:12:08 -0800 (PST), "
wrote:


Tongue depressors fall into the same category and those which fall out
of date can usually be found for sale as new-surplus, from such
outfits as American Science & Surplus. (A tongue depressor is just a
BIG 'ice cream' stick.)

I don't know what these sticks are made of; birch or poplar at a
guess. But it's a dense hardwood that works very well as 'curbing'
around metal fittings. That is, with the fitting in place, you
prepare a hardwood 'curb' around the fitting. Do a proper job of it
and the 'curbing' will provide such a grip on the fitting that it
serves to hold the fitting in place, allowing you to drill the holes
for the fasteners. A fast-curing epoxy such as those mentioned above
appears to be the ideal adhesive for this kind of work.

-R.S.Hoover

ice cream sticks are made from strong non aromatic woods so that they
dont taint the food product or break while in use.
in australia all that I am aware of are made from queensland hoop
pine.
in america I'd bet that your ice cream sticks are made from grade 2
spruce.
Stealth Pilot



Just looking at the wood (sticks), my first guess would have been basswood
(linden), beech, or birch. light-grained, clear, straight/

Flash

In article
,
" wrote:

To All:

There are times when you need to put something together fast, often
while HOLDING the parts in positionby HAND, such as when you are
making a jig or fixture. Many times the fixture is made of whatever
wood you happened to have available.... 'good' scrape, if you know
what I mean. But the jig or fixture itself is NOT scrap -- you want
it to hold up, often for a span of YEARS. That's when you reach for
whatever quick-curing EPOXY you happen to have on hand.

I've previously mentioned that I use several different adhesives,
selecting them according to need, cost, availability, temperature and
so on. STRENGTH is never an issue since ALL modern adhesives are
stronger (in shear) than the softwoods normally used to build an
airplane (or even a jig :-)

If you will go to...
http://search.harborfreight.com/cpis...?keyword=epoxy...
...you will see several epoxies, including Item# 65048 and Item#
92665. The latter is often on sale for 99cents and is super-simple to
use, thanks to its 1:1 mixing ratio.

If you remember to apply the adhesive to BOTH surfaces... and give
them a couple minutes of 'open' time, they even work on hardwoods.

Don't take my word for any of this. Do your own tests and base your
opinion on that.

-----------------------------------------------

One major caveat:

Do NOT use quick-cure epoxy for PERMANENT bonds!

It is fine for temporary structures, such as jigs, but would be a
disaster if used in anything like wing spars, skins, ribs, etc.

It will disassociate in time into a jelly-like goo, with no strength.

--
Remove _'s from email address to talk to me.

On Dec 22, 6:13*pm, Orval Fairbairn
wrote:

It will disassociate in time into a jelly-like goo, with no strength.

Cite?

I have examples of 20-year-old bonds of 5-minute epoxy up at the shop,
and the bonds are still stronger than the substrate material.

In article
,
Bob Kuykendall wrote:

On Dec 22, 6:13*pm, Orval Fairbairn
wrote:

It will disassociate in time into a jelly-like goo, with no strength.

Cite?

I have examples of 20-year-old bonds of 5-minute epoxy up at the shop,
and the bonds are still stronger than the substrate material.

I had some that turned to goo, just as I said.

A friend, who used to work at Stanford Research Center, researched
epoxies and told me this about quick-cure epoxies.

Another point is to watch the temperature on ambient-cure epoxies, as
they lose much of their strength above about 150 F.

--
Remove _'s from email address to talk to me.

On Dec 22, 6:32*pm, Orval Fairbairn
wrote:

It will disassociate in time into a jelly-like goo, with no strength.
-----------------------------------------------------------

Dear Orval,

You're right, of course. Any epoxy, fast or slow... CAN react exactly
as you've described. But the reason can usually be tracked back to
some problem with either the chemistry of the components or a problem
with the ratios. For example, more than thirty years ago I recall
using lots of "5 Minute" epoxy on at least three of the Varieze's
fabricated here in San Diego county. Fortunately, we never had any of
the 'epoxy problems' such as the one you described but a lot of other
builders did. Those problems were among the reasons that lead to
ratio-pumps, which have become pretty much a standard tool for
builders of composite aircraft.

However, for my own work, here at the shop -- especially when I need a
third hand and don't have one, I've found fast-curing epoxies to be a
very handy tool.

As for using such an adhesive in a structural capacity, I've got a
hunch the parts being joined would never be of any significant size,
since the 'cure-time' usually starts when the two parts are added
together. Then they must be mixed to a perfectly uniform blend, after
which comes applying the adhesive to the parts, etc. The point here
is that most of the year it probably takes me a couple of minutes to
get just a SMALL amount of them properly mixed... and I'm even worse
with filled epoxies, such as 3M or JB Weld. So if the stuff was for
something structural, it couldn't be of any size.

But I wonder if the Varieze owners have a Newsgroup or mailing list.
(They probably do.) And if they've ever run into this problem.

-R.S.Hoover

"Flash" wrote

Just looking at the wood (sticks), my first guess would have been basswood
(linden), beech, or birch. light-grained, clear, straight/

Yep, basswood would be a real good guess, and birch would be my second
guess.

There is no easy to see differences between the summer and winter wood in
our sticks, so I would rule spruce out.
--
Jim in NC

"Morgans" wrote in message
...

Yep, basswood would be a real good guess, and birch would be my second
guess.

There is no easy to see differences between the summer and winter wood in
our sticks, so I would rule spruce out.
--
Jim in NC

These guys use Birch:

http://www.quickmedical.com/puritan/depressors.html

Wood-based products and wooden shafts are made from Northern White Birch,
which yields a high tensile strength and is smooth to the touch. The
following Puritan tongue depressors are perfect for oral patient examination
and patient care.

On Dec 23, 5:38*am, "Morgans" wrote:

Yep, basswood would be a real good guess, and birch would be my second
guess.
--------------------------------------------------------------------------------------

Dear Jim and the Group,

Some of you have been asking if this thread has anything to do with
the Chugger Project, and if so, shouldn't it be included there. The
answer is a qualified 'Yes,' in that the structure will appear in both
the Chugger as well as the Primary Glider, assuming I live long
enough.

Right now, the thread has to do with fast-curing epoxy and it's
availability through Harbor Freight. That brought some mail wanting
to know just HOW this applied to the Chugger/Primary experiments, so
I've concluded this message with an explanation that will hopefully
answer many of your questions.

So let's get back to the show :-)
-------------------------------------------------------------------------------------------------------------------------

I don''t think you'll see any spruce tongue depressors. Not in North
America. Poplar and birch but no softwoods at all. This is based on
about two dozen samples, purloined from examining rooms at medical
facilities in northern San Diego county between June and December,
2008. Since some of the examining rooms were in the same facility
it's fair to assume they had the same source of supply so the two-
dozen figure should be adjusted downward to about six ordering
sources. (Even then, I've a hunch some of those will be dupes.)

The 'ice cream' size sticks were hardwoods; probably poplar, but
that's based on only two samples: New surplus 'Hobby Sticks' in one
case, 'mixer/stirer' sticks in the other, the latter purchased from a
local composites retailed, the former ordered via mail from American
Science & Surplus.

Why the interest in the specie & source? Because of the material's
strength in the first case, and the chance of the wood being treated
with an antibacterial compound on the other. Mixing or 'hobby' sticks
(ie,'ice cream sticks) won't have any antibacterial treatment. Tongue
depressors MAY be treated if they're shipped 'bare' -- about fifty in
a sealed plastic pouch. But some are shipped individually sealed in a
paper sleeve bearing advertising for various drug dealers and the
paper or the tongue depressor emits a mild chemical odor indicating
some form of antibacterial treatment. Tests with epoxy shows the
chemical does NOT interfere with making bond that passes the FPL's
standard shear-strength test, albeit one that has been scaled down to
match the material.

Size-wise an average of five gave the following dimensions: Tongue
depressors, length = 5-29/32" (5.94") 150.889mm, width
29/32" (0.90625) 23mm, thickness 1/16" (0.068) x 1.727mm
Ice stick dimensions: Length 4-7/16" (4.423) 112.344mm, width
3/8" (0.478) 12.14mm, thickness 1/16" (0.084) 2.13mm

I've mentioned the sizes here because one of the Chugger's experiments
is the use of redwood plaster lath instead of spruce as a building
material. The reason for this is because all six varieties of redwood
are a close match for Sitka Spruce when it comes to weight & strength,
plus the spec for plaster lath is that it must have a run-out of not
less than 1:16 (ie, the distance between studs in a wall), and it must
be clear -- no knots! Plaster lath comes in lengths up to 8 feet.
It's nominal width is 1-1/4" wide x 1/4" thick but it is ROUGH SAWN
and deliberately left brash, so as to offer a maximum amount of
'tooth' for the plaster. And it's relatively inexpensive. The
problem is that brashness. The surface is so rough that it's
impossible to get a good glue bond unless you use a filled adhesive OR
take the trouble to run the lath through a surface plane. Alas, the
typical plane wants a sixteen of an inch. Take that off both sides
and you're left with a rather whippy stick barely an eighth of an inch
thick. Which is fine if you're making wing-tip bows, or the Chuggers
rudder.

I've used redwood lath for the spars in a simple tail group, in which
the C-type hinges were made from steel strapping. This stuff is
pretty whippy being only .023" thick. But it's steel and it's free,
if you do a bit of dumpster diving, plus it's easy to work with. One
problem with it: It's so thin it will cut through the typical hinge-
pin ( a nail or Cotter key ) in about 100,000 movements at max load.
The solution (for me) was to add more hinges, which meant doing the
ends first then aligning the others with a length of thread, fixing
them in place with neatly shaped pieces of ice-cream sticks and FAST-
SETTING EPOXY. Once I'd boxed the fitting, I drilled through it for
8-32 hardware. The hinges sit atop a foundation of tongue depressors,
which solves the problem of the rough-sawn surface of the redwood.

Alignment of the rudder and elevator is even easier: Simply attach
the mating half of each particular C-type hinge to its partner, attach
the rudder spar to the vert. stabilizer spar using only the END
hinges, then align those in between, fixing the hinges into place
using the method described above.

This method meets the Chugger's design philosophy of minimum cost.
Tests indicate the hinges are more than strong enough. (See the blog
article 'Tail flapper failure.') The parts are locally available for
most of us.

The purpose of the hinge is rather subtle and from a design point of
view, you want the encountered loads to appear across the hinges. To
get them there, you use ribs or diagonals that are stiff enough so as
not to buckle. Redwood stringers and door-skin shear-webs on ribs
that are fabricated in place work perfectly well. But so does bamboo
shish-kabob skewers and fiber gussets, and they weigh but a fraction
of the traditional spar-cap/shear-web design.

-R.S.Hoover