Question about epoxy resin chemistry..

Corky Scott wrote:

Ernest, I'm not sure I understand the problem. Most kits that require
fiberglass supply the recommended type of resin. If you are doing
something other than buiding a kit, you could just look at what the
kits supply and use that, couldn't you?

Why is this so difficult? Are you designing your own airplane?

Thanks, Corky Scott



Hey, Corky! I believe you were involved in the most informative thread
I found as I was searching the archives of this group.

Let me see if I can convey a least part of my confusion. The Dyke Delta
JD-2 is a plans built craft...ie, no kit. The plans specify that the
composite wing skins be laid up on a flat table and then wrapped and
riveted to the stainless steel ribs before it is fully cured.

I'm at work, so don't have the plans in front of me, but the instruction
read something like:

The prototype uses polyester vinyl resin. Other types of resins are
available. Follow resin manufacturer's instructions.

May not be the exact wording, but that is the gist of it. John Dyke has
had a lot of problems over the years with the resin continuing to
shrink, exposing the weave, etc. So I want to avoid those problems.
That's the start of the confusion.

Larry LaBeau just completed his Delta a year ago, and had a lot of
success using premade panels. Hmmm...get a stronger, pin-hole free skin
without all the work, smell, or exposure to hazardous chemicals. Great
idea in my book. He bought his panels 6yrs ago. If you look at a
manufactures web site, you'll be inundated with choices, all only
slightly different.

The thread I read here occured in 1994, and it discussed how brittle
resins were and that some 'new' developments were making resins tougher
vs just harder. It discussed how West Systems was not a good laminating
epoxy, even though Aircraft Spruce sells it as a laminating epoxy.

In fact, every place you look that sells epoxy says that every
formulation is the perfect solution for everything. Just a lot of noise
and practically no signal. I go to the EAA meeting and mention "resin
system" and really get noise. If you try this, be ready to duck the
flak from those supporting epoxy vs vinyl ester vs polyester vinyl vs
chicken soup soaked paper napkins. I get the impression that very few
know anything other than what their kit specified, and are arguing from
the 'my choice must be the best, else I'm an idiot' perspective.

I'd like to make these skins once, and not have a lot of regrets in
5yrs. I want to pick the BEST sytem, not just a good system. But as
far as I can tell, the stuff that Lowe's has on its shelf is no
different than the 'aircraft' epoxies, except in the lower price. I
find VERY little difference in the mechanical properties of the
different resins, but a LOT of difference in prices. Either I'm missing
out on something, or a lot of people are getting taken for a ride. At
this point, I'm assuming the former.

Where can I find recent information other than sales brochures? More
importantly, does it really matter? Is the stuff at Lowe's so much
stronger than what's required that it just doesn't make sense to spend more?

I forget who said it, but answers are easy. It's asking the right
questions that's hard. Right now, I'm at the point of not even knowing
if there is a good question to ask.

--
http://www.ernest.isa-geek.org/
"Ignorance is mankinds normal state,
alleviated by information and experience."
Veeduber

On Fri, 09 Apr 2004 15:37:51 GMT, Ernest Christley
wrote:

Corky Scott wrote:

Ernest, I'm not sure I understand the problem. Most kits that require
fiberglass supply the recommended type of resin. If you are doing
something other than buiding a kit, you could just look at what the
kits supply and use that, couldn't you?

Why is this so difficult? Are you designing your own airplane?

Thanks, Corky Scott



Hey, Corky! I believe you were involved in the most informative thread
I found as I was searching the archives of this group.

Let me see if I can convey a least part of my confusion. The Dyke Delta
JD-2 is a plans built craft...ie, no kit. The plans specify that the
composite wing skins be laid up on a flat table and then wrapped and
riveted to the stainless steel ribs before it is fully cured.

I'm at work, so don't have the plans in front of me, but the instruction
read something like:

The prototype uses polyester vinyl resin. Other types of resins are
available. Follow resin manufacturer's instructions.

May not be the exact wording, but that is the gist of it. John Dyke has
had a lot of problems over the years with the resin continuing to
shrink, exposing the weave, etc. So I want to avoid those problems.
That's the start of the confusion.

Ah, got it. The only suggestion I can make would be to speak to the
folks who supply the plans materials and see what type of resin they
are now offering. Perhaps it's different from the one originally
called for by John Dyke.

If that doesn't give you satisfaction, I think I'd speak to the
manufacturers of the various resin systems and ask the opinion of the
experts there. Explain what it is you are trying to do and why you
are asking for their opinion.

The covering process sounds complex: you have to allow the cloth to
semi cure, and then lay it one such that it bonds in place. Man, that
sounds like a narrow window.

Saw one of those things zipping by at a Waco fly-in in Ohio back in
'93 or so. It was FAST.

Corky Scott

Corky Scott wrote:

On Fri, 09 Apr 2004 15:37:51 GMT, Ernest Christley
wrote:

Corky Scott wrote:

Ernest, I'm not sure I understand the problem. Most kits that require
fiberglass supply the recommended type of resin. If you are doing
something other than buiding a kit, you could just look at what the
kits supply and use that, couldn't you?

Why is this so difficult? Are you designing your own airplane?

Thanks, Corky Scott



Hey, Corky! I believe you were involved in the most informative thread
I found as I was searching the archives of this group.

Let me see if I can convey a least part of my confusion. The Dyke Delta
JD-2 is a plans built craft...ie, no kit. The plans specify that the
composite wing skins be laid up on a flat table and then wrapped and
riveted to the stainless steel ribs before it is fully cured.

I'm at work, so don't have the plans in front of me, but the instruction
read something like:

The prototype uses polyester vinyl resin. Other types of resins are
available. Follow resin manufacturer's instructions.

May not be the exact wording, but that is the gist of it. John Dyke has
had a lot of problems over the years with the resin continuing to
shrink, exposing the weave, etc. So I want to avoid those problems.
That's the start of the confusion.

Ah, got it. The only suggestion I can make would be to speak to the
folks who supply the plans materials and see what type of resin they
are now offering. Perhaps it's different from the one originally
called for by John Dyke.

If that doesn't give you satisfaction, I think I'd speak to the
manufacturers of the various resin systems and ask the opinion of the
experts there. Explain what it is you are trying to do and why you
are asking for their opinion.

The covering process sounds complex: you have to allow the cloth to
semi cure, and then lay it one such that it bonds in place. Man, that
sounds like a narrow window.

Saw one of those things zipping by at a Waco fly-in in Ohio back in
'93 or so. It was FAST.

Corky Scott

Back in "the old days", polyester resin was all that was really
available.
Not wanting to start the resin wars again, I'll only point out that
JD used polyester resin for the Delta skins.

But if he were designing this plane today?

It would use epoxy resin. And foam cored composite structure -
(instead of the welded/brazed steel structure)

just the way he originally envisioned it.


John was _way_ ahead of his time...

Richard

Me thinks the 'panels' are riveted on semi-cured because in the good ol' days when resins cured they were brittle. These
are simply skins on the wing and they are not adhered via the resin; the resin is supposed to be slightly green to allow
it to conform to the airfoil without cracking.

Lay out the panels on a big piece of glass and it will be pin hole free when you pull it off. The panel can be trimmed
to size while still on the glass. How many layers of what kind of glass are used in the lay-up? How sharp is the
tightest bend?

--
Dan D.



..
"Corky Scott" wrote in message ...
On Fri, 09 Apr 2004 15:37:51 GMT, Ernest Christley
wrote:

Corky Scott wrote:

Ernest, I'm not sure I understand the problem. Most kits that require
fiberglass supply the recommended type of resin. If you are doing
something other than buiding a kit, you could just look at what the
kits supply and use that, couldn't you?

Why is this so difficult? Are you designing your own airplane?

Thanks, Corky Scott



Hey, Corky! I believe you were involved in the most informative thread
I found as I was searching the archives of this group.

Let me see if I can convey a least part of my confusion. The Dyke Delta
JD-2 is a plans built craft...ie, no kit. The plans specify that the
composite wing skins be laid up on a flat table and then wrapped and
riveted to the stainless steel ribs before it is fully cured.

I'm at work, so don't have the plans in front of me, but the instruction
read something like:

The prototype uses polyester vinyl resin. Other types of resins are
available. Follow resin manufacturer's instructions.

May not be the exact wording, but that is the gist of it. John Dyke has
had a lot of problems over the years with the resin continuing to
shrink, exposing the weave, etc. So I want to avoid those problems.
That's the start of the confusion.

Ah, got it. The only suggestion I can make would be to speak to the
folks who supply the plans materials and see what type of resin they
are now offering. Perhaps it's different from the one originally
called for by John Dyke.

If that doesn't give you satisfaction, I think I'd speak to the
manufacturers of the various resin systems and ask the opinion of the
experts there. Explain what it is you are trying to do and why you
are asking for their opinion.

The covering process sounds complex: you have to allow the cloth to
semi cure, and then lay it one such that it bonds in place. Man, that
sounds like a narrow window.

Saw one of those things zipping by at a Waco fly-in in Ohio back in
'93 or so. It was FAST.

Corky Scott

Blueskies wrote:
Me thinks the 'panels' are riveted on semi-cured because in the good ol' days when resins cured they were brittle. These
are simply skins on the wing and they are not adhered via the resin; the resin is supposed to be slightly green to allow
it to conform to the airfoil without cracking.

Lay out the panels on a big piece of glass and it will be pin hole free when you pull it off. The panel can be trimmed
to size while still on the glass. How many layers of what kind of glass are used in the lay-up? How sharp is the
tightest bend?


Wow. Big piece of glass. The skins will be a triangle with 8ft sides.
The plans specify two layers of 7.5 or 10oz glass. They extend up to
the 1" radius of the leading edge, but don't actually go around it.

--
http://www.ernest.isa-geek.org/
"Ignorance is mankinds normal state,
alleviated by information and experience."
Veeduber

Yes, I guess that would be a big piece of glass (don't take anything out of context here!). Do the plans/instructions
have any other suggested way to lay up the panels?

As far as bending the finished panels, a two layer lay-up will be quite flexible, even fully cured, and as long as you
don't have to wrap around the LE I'm sure you will not have any problems with cracking. Have you looked at the
http://www.westsystem.com/ site? Good stuff...

--
Dan D.



..
"Ernest Christley" wrote in message om...
Blueskies wrote:
Me thinks the 'panels' are riveted on semi-cured because in the good ol' days when resins cured they were brittle.
These
are simply skins on the wing and they are not adhered via the resin; the resin is supposed to be slightly green to
allow
it to conform to the airfoil without cracking.

Lay out the panels on a big piece of glass and it will be pin hole free when you pull it off. The panel can be
trimmed
to size while still on the glass. How many layers of what kind of glass are used in the lay-up? How sharp is the
tightest bend?


Wow. Big piece of glass. The skins will be a triangle with 8ft sides.
The plans specify two layers of 7.5 or 10oz glass. They extend up to
the 1" radius of the leading edge, but don't actually go around it.

--
http://www.ernest.isa-geek.org/
"Ignorance is mankinds normal state,
alleviated by information and experience."
Veeduber

Blueskies wrote:

Yes, I guess that would be a big piece of glass (don't take anything out of context here!). Do the plans/instructions
have any other suggested way to lay up the panels?

As far as bending the finished panels, a two layer lay-up will be quite flexible, even fully cured, and as long as you
don't have to wrap around the LE I'm sure you will not have any problems with cracking. Have you looked at the
http://www.westsystem.com/ site? Good stuff...

--
Dan D.

.

I've been told that West does indeed make a laminating resin,
but this isn't it.

West 105/205 is absolute best stuff I've ever used - on wood.

It will probably be great on wood/foam structures.

But it's not what I ever use (again) for laminating glass fabrics.

I used to use Dow 330 / 147(?) but my source quit carrying it
(because I was the only one buying it?)

My impression is that resins like 330 that don't use MDA (Methyl
Diethel Amines???) share a common "problem". At low temperatures
they tend to "separate out". The resin has an odd lumpy look on
the surface and there will be a lump of soft rock candy in the center.

It is real simple to correct by immersing the resin container in hot
water for a while. When the soup is clear again, it's ready to use.

But if the resin is at all "crystallized", it won't completely set -
ever.

It even says so in the directions!
For those who read such things...

Got AeroPoxy(?) last resupply to make a new cowling for Leo's
Super Zodiac. I've used it before, no complaints (other than the
MDA toxicity?).


So, what is it that you are building?

Richard

Richard Lamb wrote:
Blueskies wrote:

Yes, I guess that would be a big piece of glass (don't take anything out of context here!). Do the plans/instructions
have any other suggested way to lay up the panels?

As far as bending the finished panels, a two layer lay-up will be quite flexible, even fully cured, and as long as you
don't have to wrap around the LE I'm sure you will not have any problems with cracking. Have you looked at the
http://www.westsystem.com/ site? Good stuff...

--
Dan D.

.


I've been told that West does indeed make a laminating resin,
but this isn't it.

West 105/205 is absolute best stuff I've ever used - on wood.

It will probably be great on wood/foam structures.

But it's not what I ever use (again) for laminating glass fabrics.

I used to use Dow 330 / 147(?) but my source quit carrying it
(because I was the only one buying it?)

My impression is that resins like 330 that don't use MDA (Methyl
Diethel Amines???) share a common "problem". At low temperatures
they tend to "separate out". The resin has an odd lumpy look on
the surface and there will be a lump of soft rock candy in the center.

It is real simple to correct by immersing the resin container in hot
water for a while. When the soup is clear again, it's ready to use.

But if the resin is at all "crystallized", it won't completely set -
ever.

It even says so in the directions!
For those who read such things...

Got AeroPoxy(?) last resupply to make a new cowling for Leo's
Super Zodiac. I've used it before, no complaints (other than the
MDA toxicity?).


So, what is it that you are building?

Richard

Dyke Delta JD-2. http://www.ernest.isa-geek.org for the whole story.
The skins, turtleback and cowling are all fiberglass. Some builders
have also glassed the belly, tailfin and control surfaces (plans call
for fabric there).


--
http://www.ernest.isa-geek.org/
"Ignorance is mankinds normal state,
alleviated by information and experience."
Veeduber

Blueskies wrote:
Yes, I guess that would be a big piece of glass (don't take anything out of context here!). Do the plans/instructions
have any other suggested way to lay up the panels?

The directions say to lay it up on a couple pieces of MDF laid
side-to-side, with a piece of tape down the center. I have to cut forms
for the stainless steel ribs, so I thought an improvement on this
technique might be to use the forms to shape the MDF so that the
resulting layup is nearly the correct shape already. Very little
bending==very little built up stress.

The biggest improvement would be not to have to make the skins at all.
I've looked at G-10 and FR4, and have found several manufactures with
lots of data sheets. Reading them, I keep hearing that eerie refrain,
"You are in a maze of rooms, all slightly different..."


As far as bending the finished panels, a two layer lay-up will be quite flexible, even fully cured, and as long as you
don't have to wrap around the LE I'm sure you will not have any problems with cracking. Have you looked at the
http://www.westsystem.com/ site? Good stuff...


Looked there. Good stuff...IF you're building a boat, or a trailer, or
a chair. Goes back to what I said before. Every manufacturers claim
that what they have is good for whatever you're doing. While that just
may be true, but I don't trust it to be, and it is so much unfamiliar
territory that I just keep getting lost. What I need is a map to help
seperate the hype from the information.

--
http://www.ernest.isa-geek.org/
"Ignorance is mankinds normal state,
alleviated by information and experience."
Veeduber

On Fri, 09 Apr 2004 15:37:51 GMT, Ernest Christley
wrote:

:In fact, every place you look that sells epoxy says that every
:formulation is the perfect solution for everything. Just a lot of noise
:and practically no signal. I go to the EAA meeting and mention "resin
:system" and really get noise. If you try this, be ready to duck the
:flak from those supporting epoxy vs vinyl ester vs polyester vinyl vs
:chicken soup soaked paper napkins. I get the impression that very few
:know anything other than what their kit specified, and are arguing from
:the 'my choice must be the best, else I'm an idiot' perspective.

Talk to Gary Hunter, of Gary Hunter Composites in Houston, Texas. The
last email I have for him is gluegaru (at) earth (dot) net. Another
one I have is gary (dot) hunter (at) resins (dot) com but that one is
older and my not be good anymore. Do the obvious replacements to
despamify.

"Gary is an Epoxy Resin Chemist for Shell Chemical Company, with over
26 years experience formulating and using epoxies in various end uses
throughout the industry."