[NSRCA-discussion] thinning epoxy, how?

Mon Mar 16 10:51:32 AKDT 2009

 I always use 5 minute epoxy, and add a few drops of denatured alcohol until
I thinned it to the point I wanted, then painted it on. I use a heat gun to
really make it soak and it is always dried in sort time.

 I have one plane with several years on it and no fuel-oil damage.

 Also make sure it gets into the holes for the fuel lines.

Sincerely

Linda A. Carnes

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From: nsrca-discussion-bounces at lists.nsrca.org
[mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of J Shu
Sent: Monday, March 16, 2009 2:45 PM
To: General pattern discussion
Subject: Re: [NSRCA-discussion] thinning epoxy, how?

This is for the firewall and pipe tunnel.

Regards,
Jason
www.shulmanaviation.com
www.composite-arf.com

----- Original Message ----- 

From: Gray E Fowler <mailto:gfowler at raytheon.com>  

To: General pattern discussion <mailto:nsrca-discussion at lists.nsrca.org>  

Sent: Monday, March 16, 2009 2:35 PM

Subject: Re: [NSRCA-discussion] thinning epoxy, how?

Jason 

Use the finishing resin...if no styrofoam core issues, cut with acetone of
MEK, both sold at Home Depot or Lowes. If the core is yellow-brown then that
is a urethane ridgid foam and okay for acetone/MEK. 

Gray Fowler
Senior Principal Chemical Engineer
Radomes and Specialty Apertures
Technical Staff Composites Engineering
Raytheon 

"J Shu" <jshulman at cfl.rr.com> 
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03/16/2009 01:25 PM 

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Re: [NSRCA-discussion] thinning epoxy, how?

I have Z-Poxy 30 min and Finishing resin 

Regards,
Jason
 <http://www.shulmanaviation.com/> www.shulmanaviation.com
 <http://www.composite-arf.com/> www.composite-arf.com 
----- Original Message ----- 
From: Gray E Fowler <mailto:gfowler at raytheon.com>  
To: General pattern discussion <mailto:nsrca-discussion at lists.nsrca.org>  
Sent: Monday, March 16, 2009 2:17 PM 
Subject: Re: [NSRCA-discussion] thinning epoxy, how? 

Jason 

When you say finishing resin do mean epoxy or polyester? I do not understand
your configuration of bonding the horns, but if the bond is the only thing
holding the horns on, best use and adhesive.  Laminating epoxies and all
polyesters have low peel strength = bad bond characteristics. Horns will
experience a cleave stress which is shear+peel, if there is any flex then
lots of peel stress. 

A good adhesive has thousands PSI shear strength, but only 25 lbs of peel.
Laminating resins peel = 0.

Gray Fowler
Senior Principal Chemical Engineer
Radomes and Specialty Apertures
Technical Staff Composites Engineering
Raytheon 

"J Shu" <jshulman at cfl.rr.com> 
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03/16/2009 11:46 AM 

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Re: [NSRCA-discussion] thinning epoxy, how?

So much good info. I'm gonna use Finishing resin to seal the motor area. 

How bad of an idea would it to be the finishing resin to glue in the
fiberglass horns into the wood surfaces? 

Regards,
Jason
 <http://www.shulmanaviation.com/> www.shulmanaviation.com
 <http://www.composite-arf.com/> www.composite-arf.com 
----- Original Message ----- 
From: Gray E Fowler <mailto:gfowler at raytheon.com>  
To: General <mailto:nsrca-discussion at lists.nsrca.org>  pattern discussion 
Sent: Monday, March 16, 2009 11:44 AM 
Subject: Re: [NSRCA-discussion] thinning epoxy, how? 

Jim 

Polyesters will not cure when in contact with oxygen, leaving a sticky
surface. If your surface is not sticky after applying-curing polyester then
you are using a "true" polyester finishing resin, which is fine, BUT look
out because to stop the oxygen inhibition polyester "finishing" resins add
5% wax, which floats to the surface and blocks the oxygen. I say lookout,
because any future bonding to this area will be extremely poor. If you are
not bonding to an area saturated with this resin you are fine. 

K&B paint was fine, just a regular epoxy cured with a polyamide, meaning the
mixture needs to be "inducted" prior to use, that is mixed up and then sits
in a mass for a t least 15 minutes (read the instructions) or the polyimide
will slightly separate giving you a sticky surface. 

Unfamiliar Formula U, but Concept clear works very well. 

I always clear coat with Concept 2021..easy, lightweight and more durable.
My entire engine area is sealed with Concept clear or laminating epoxy.

Gray Fowler
Senior Principal Chemical Engineer
Radomes and Specialty Apertures
Technical Staff Composites Engineering
Raytheon 

"J N Hiller" <jnhiller at earthlink.net> 
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03/16/2009 10:16 AM 

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Re: [NSRCA-discussion] thinning epoxy, how?

Thank you for the very informative information. I have never used epoxy for
fuel proofing. I've used Polyester finishing resin and K&B epoxy paint until
I ran out and recently Formula-U Polyurethane paint. What are your thoughts
on these alternate materials? 

I find fuel proof compromising gouges are more visible using colored paint
rather than a clear coating. 

Jim Hiller 

-----Original Message-----
From: nsrca-discussion-bounces at lists.nsrca.org
[mailto:nsrca-discussion-bounces at lists.nsrca.org]On Behalf Of Gray E Fowler
Sent: Monday, March 16, 2009 6:24 AM
To: General pattern discussion
Subject: Re: [NSRCA-discussion] thinning epoxy, how? 

Fast curing epoxy adhesives such as the 30 minute are a bad initial choice.
I realize that thousands have used it in these applications, but that still
does not make it a good choice. The non reactive components in the fast
epoxy plasticize with age and methanol and nitro will seriously degrade the
stuff. Using one of the thinner slower curing laminating resins will require
less solvent, if any and provide a much longer lasting barrier. Any solvent
added to an epoxy needs to evaporate completely or you will created a
problem. Denatured alcohol (ethanol) evaporates very slowly. Cutting a fast
cure epoxy with a slow evaporating solvent is a recipe for trapping alot of
solvent, making the chemical resistant even worse. Methanol evaporates much
faster and epoxy is much more soluable in methanol. Be very careful using
ketone solvents (acetone, MEK) or aromatics (Toluene, Xylene) because many
kit manufacturers use styrofoam as a core material that will be destroyed in
seconds with  all solvents except the alcohols. 

SO! 

1. Use a thin slower cure laminating resin 
2. Use Acetone, MEK or Laquer thinner 
3. NO puddles, super thin coat 
4. Alcohols if you have a styrofoam core 
5. rule #3 again 

6. If you only need the plane to last 1 year, then use 15 minute epoxy and
do not worry..it will last 1 year or so. 

Gray Fowler
Senior Principal Chemical Engineer
Radomes and Specialty Apertures
Technical Staff Composites Engineering
Raytheon 

"J Shu" <jshulman at cfl.rr.com> 
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03/15/2009 02:15 AM 

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[NSRCA-discussion] thinning epoxy, how?

I want to add another layer of sealer to the firewall and tunnel on my
plane... what's the best way to do it with epoxy? I've got 30 
minute but not sure how to thin it to seal it.

Regards,
Jason
www.shulmanaviation.com
www.composite-arf.com
[attachment "IMG_4498 (500 x 299).jpg" deleted by Gray E Fowler/US/Raytheon]
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