[NSRCA-discussion] thinning epoxy, how?

J Shu jshulman at cfl.rr.com
Mon Mar 16 10:45:10 AKDT 2009 

This is for the firewall and pipe tunnel.

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

  ----- Original Message ----- 
  From: Gray E Fowler 
  To: General pattern discussion 
  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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  I have Z-Poxy 30 min and Finishing resin 

  Regards,
  Jason
  www.shulmanaviation.com
  www.composite-arf.com 
  ----- Original Message ----- 
  From: Gray E Fowler 
  To: General pattern discussion 
  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> 
        Sent by: nsrca-discussion-bounces at lists.nsrca.org 
        03/16/2009 11:46 AM 
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  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
  www.shulmanaviation.com
  www.composite-arf.com 
  ----- Original Message ----- 
  From: Gray E Fowler 
  To: General 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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  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> 
        Sent by: nsrca-discussion-bounces at lists.nsrca.org 
        03/15/2009 02:15 AM 


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  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
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