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  #1  
Old 04-09-2019, 07:51 PM
NYTOM NYTOM is offline
 
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Default Resin type

Would anyone know the type of resin compatible with the green cowls as opposed to the older pink models. Polyester, vinyl ester or epoxy ?
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  #2  
Old 04-09-2019, 07:54 PM
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wirejock wirejock is offline
 
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Default Vans fiberglass

I believe it's all epoxy.
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  #3  
Old 04-10-2019, 03:27 AM
NYTOM NYTOM is offline
 
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Quote:
Originally Posted by wirejock View Post
I believe it's all epoxy.
Thank you Larry
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  #4  
Old 04-10-2019, 10:16 AM
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Default Use Epoxy

My understanding is that you can use epoxy resin with polyester parts, but not polyester resin with epoxy parts. I could be wrong about that, but my friend, who's a fiberglass guru, told me to use an epoxy based system, so I did. I've used the West Systems epoxy resin for all my fiberglass work so far. If you get the slow hardener (but not the super slow), it has a great working time.
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  #5  
Old 04-10-2019, 10:37 AM
lr172 lr172 is offline
 
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Quote:
Originally Posted by ppilotmike View Post
My understanding is that you can use epoxy resin with polyester parts, but not polyester resin with epoxy parts. I could be wrong about that, but my friend, who's a fiberglass guru, told me to use an epoxy based system, so I did. I've used the West Systems epoxy resin for all my fiberglass work so far. If you get the slow hardener (but not the super slow), it has a great working time.
+1

Polyester resin layups over epoxy is a no no. Adhesion is poor. However, polyester fillers will adhere just fine to fully cured epoxy layups.

Larry
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  #6  
Old 04-10-2019, 12:24 PM
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Polyester resin layups over epoxy is a no no. Adhesion is poor. However, polyester fillers will adhere just fine to fully cured epoxy layups.
..Alchemy?
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  #7  
Old 04-10-2019, 05:18 PM
NYTOM NYTOM is offline
 
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Originally Posted by lr172 View Post
+1

Polyester resin layups over epoxy is a no no. Adhesion is poor. However, polyester fillers will adhere just fine to fully cured epoxy layups.

Larry
Good to know. Epoxy it is.
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  #8  
Old 04-10-2019, 05:59 PM
BillL BillL is offline
 
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Quote:
Originally Posted by DanH View Post
..Alchemy?
Apparently . .
West testing.

West: "Because of the difference in curing chemistry, it is not possible to achieve a chemical bond between epoxy and polyester gelcoat."

They go on to say the adhesion is mechanical. The final conclusion is that the bonding is fine for gelcoat (I assume not as a structural bond).

Pretty much covers polyester fillers too.
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  #9  
Old 04-10-2019, 10:23 PM
lr172 lr172 is offline
 
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Quote:
Originally Posted by DanH View Post
..Alchemy?
Not sure I understand your meaning by that.

A decent amount of research taught me that polyester resin (as in peroxide activated for layups) does not adhere that well to epoxy, though it adheres well to cured polyester.

Not saying that it will fall off, but does not create the bond level expected for a layup andt is considered a bad practice by those in that business.

I am admittedly not a "fiberglass guy" just passing along learnings.

Larry
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  #10  
Old 04-10-2019, 10:26 PM
lr172 lr172 is offline
 
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Quote:
Originally Posted by BillL View Post
Apparently . .
West testing.

West: "Because of the difference in curing chemistry, it is not possible to achieve a chemical bond between epoxy and polyester gelcoat."

They go on to say the adhesion is mechanical. The final conclusion is that the bonding is fine for gelcoat (I assume not as a structural bond).

Pretty much covers polyester fillers too.
This relates to epoxies ability to bond to polyester which isn't really relevant to polyesters ability to bond with epoxy. The cured epoxy or gel coat on the OP's cowl has reached a full cured state and therefore cannot chemically bond with anything (epoxies can only chemically bond prior to reaching a full cured state). Epoxy is known to have a much stronger mechanical bond than polyester resin. Epoxy is much more flexible in what it will form a relatively strong mechanical bond with. This is one of it's main advantages. Polyester is not as flexible in this regard and doesn't grip very strong, mechanically, as epoxy even in its most favorable environment.

If I remember correctly, polyesters chemical bonding window never closes, which is why polyesters resins can be so successfully applied over cured polyester; In this case, it is not rely upon it's poor mechanical adhesion, but forming a strong chemical bond. As West mentions, polyester cannot even chemically bond with epoxy, even if the epoxies window was open, due to different chhemistries.

Larry
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Last edited by lr172 : 04-10-2019 at 10:42 PM.
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