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zmk1962

How to tell Polyester from epoxy fiberglass

8 posts in this topic

Hey Raiders,

I have not worked with fiberglass previously apart from fixing little gelcoat chips and drill holes - so I have experience with small stuff but nothing structural but would appreciate some advice. 

I am about to install a drum winch and want to strengthen the anchor well floor (especially where its glassed to the hull).  I'm ok with the basic principles of glassing: clean off all grease and grime, grind, more cleaning, accurate measurement of resin components, brush smooth layer of resin, lay fiberglass cloth, smooth out bubbles more resin more cloth etc. But my first question is, how do I tell if my fiberglass hull is made from epoxy or polyester resin?

I've heard that the two systems are somewhat incompatible and if you don't use the same system then delamination of the new layers will occur.

PS: hull is a 1996 Haines Hunter 635L.

Cheers

Zoran

 

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Posted (edited)

Id use epoxy resin,

heat up the job in the sun first.

do your glassing on a nice warm day.

n make sure you clean surfaces with acetone.

and rough up the surfaces to be glassed as much as possible Zoran.

give the guys I sent you in a private message a ring they will give you all the info you need.

im a rough old fiberglasser from the 1980,s 😜

cheers marty

 

Edited by Trailcraft43

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There is a way to tell, but I cant remember it off the top of my head.

Just remember that poly only sticks to poly, and epoxy sticks to everything. Rough up what you've got, making sure you're back past the gel coat, and go for gold.

Another option is to put a sheet of 6mm aluminium on the outside of the well. That's all my anchor winch has and I've never had a problem with it. The bowsprit will break off before I lose my winch!

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Thanks Guys .... helpful as always. I love that I can count on this site for practical experience.

Marty I'll call that crowd on Monday - always keen to learn something new - even if I don't end up reinforcing the well I still have to do some glassing to seal the core where I cut through the bulkhead. 

Spotterone, as part of my research on winches I was very fortunate to find photos of an identical hull to mine with the same size winch fitted. I have attached some of those photos here and it looks like as in your case they have not reinforced the anchor well and are just relying on the backing plate. My winch should arrive this week and I'll then be able to see what type of backing plate comes with it. I have a 1/4 sheet of 4mm marine ally left over from another project which I could cut to any shape and add to the solution if I go down that path.

I have a few chores for the missus today then I can get stuck into cleaning out the anchor well to have a real good look.

Cheers

Zoran

 

IMG_5192.jpg

IMG_5193.jpg

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Putting on my very old hat as an adhesives Chemist- as far as I can remember there is no quick and dirty test to tell the difference, Once the resin is bound into matting and pigments etc are added this would only make the test more difficult without using a FTIR or the like . I would observe that you shouldnt have too many problems using epoxy to bind to cured polyester but not the other way around. Check with the resin manufacturer before proceeding- i havent worked in adhesives in over 15 years so am a bit rusty

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What winch did you buy Zoran?

im just about to go down the same path.

i was steering towards a G3.

cheers 

marty

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I was heading down the G3 path but LSM didnt have a stand at the Boat Show ... so I ended up at the Stress Free booth and they gave me a deal on the NG Midi 50 Free Fall.  Should arrive this week. 

Cheers

Zoran

 

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21 hours ago, PaddyT said:

Putting on my very old hat as an adhesives Chemist- as far as I can remember there is no quick and dirty test to tell the difference, Once the resin is bound into matting and pigments etc are added this would only make the test more difficult without using a FTIR or the like . I would observe that you shouldnt have too many problems using epoxy to bind to cured polyester but not the other way around. Check with the resin manufacturer before proceeding- i havent worked in adhesives in over 15 years so am a bit rusty

Thanks Paddyt - if I do end up glassing it will be epoxy  !! 

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