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Old Mar 19, 2015, 07:46 PM
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United States, NE, Grand Island
Joined Dec 2009
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Polyester Resin Glue

I have a Dumas boat that I am told is polyester resin made.
The outside is gel coat white.
The inside of the hull is shiny glassy finished and I can see fiberglass fibers.
What glue would I want to mount engine bearers and deck formers?
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Old Mar 19, 2015, 09:08 PM
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Old Mar 20, 2015, 12:00 AM
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Canada, BC, Victoria
Joined Oct 2011
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I would say either bondo, or CA glue.

In either case, I'd scuff the area up with some coarse sandpaper and wipe it with acetone or alcohol before hand.

You could even use the CA to tack the pieces in place, and use Bondo to really lock 'em in place.
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Old Mar 20, 2015, 12:35 AM
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Sand and "prep" properly, then I would use a Med. CA. If you still want to reinforce things, (ie: motor mounts, shaft and rudder stuffing box's) I would use Marine-Tex. Over time, it will hold up MUCH better, than Bondo. It is designed for the Commercial Marine Industry.
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Old Mar 20, 2015, 12:58 AM
Spreckels Lake, GGP, SF, CA
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If you already have some polyester resin, mix and add some micro-balloons and 'thixo' (a powder/thixotropic thickening agent, usually fumed silica) to a paste consistency of about peanut butter. Use a tongue depressor or popsicle stick to create a smooth fillet along the joint and allow to kick. For some jobs, spread a very light, thin coat of catalyzed resin on the surfaces before applying the paste. For added strength, you can add chopped fibers as well for a really strong joint.

I like doing this better than using Bondo since I can control the 'stiffness' and strength of the mixture and I've never had issues with getting the catalyst mix right.

There has to be a resins supply house in your area that has fused silica powder and glass micro-balloons in 1lb bulk packs.... set you up with a lifetime supply My 5# bags have lasted a lot of years and a lot of projects...

I gotta' concur with CaptCB, straight CA glues are never enough and should always be reinforced.
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Last edited by craig_c; Mar 20, 2015 at 01:05 AM.
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Old Mar 20, 2015, 11:17 AM
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bellingham, wa
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CA , like CB said, will bond, but isn't the best for when a "load" is put to that area. Several different things to use to bond to the fiberglass. But most importantly is to prep the area to be glued as CB recommended. I like to use G-flex marine epoxy from West Marine for all major construction/bonding. In the case of motor mounts, I cheat and use RTV silicone (black stuff) to mount some motors. I do use a slow to medium CA on the gel coat to glue things that are not in big danger of being pulled off.
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Old Mar 20, 2015, 11:20 AM
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Use z-poxy finishing resin.
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Old Mar 21, 2015, 07:06 AM
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Anything NOT polyester based, regular epoxy, J,B weld, G-flex, all bond very well to polyester resin after a scuff and clean with solvent to get all the wax off the surface.
CA will break loose with any hull flex, anything polyester just stinks, it really isn't a glue, it's for laying fiberglass, bondo is a filler not an adhesive as well.
I personally use JB Weld for all internal assembly, never had anything come loose even with many crashes pushing 60-70 mph. It is thick enough that you don't need to add anything but flows just enough to smooth itself out just a little bit, the drawback is the grey colour stands out inside the boat if this kind of thing matters to you.
Polyester only bonds well if the layer below it is still "green" or not completely set up AND as long as the layers below it are NOT waxed resin.
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Old Mar 21, 2015, 06:52 PM
Spreckels Lake, GGP, SF, CA
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Regarding prep -

1) The area needs to be absolutely clean of grease or waxes. Usually a few passes with lacquer thinner will remove most wax, grease, oils, etc.

2) The area must have 'tooth;' the resin (any resin, epoxy or poly) has to have a roughened physical surface to bind to. This is a physical bond, not a molecular one as you have between layers of partially cured resin.

60 or 80 grit sandpaper is great for roughing/prepping a surface for resin.

A note on CA from the jewelry industry.... in addition to it being brittle which causes it to fail when flexed, some appears to become more brittle/degrade with age and possibly UV exposure. This is anecdotal from some folks I knew but they basically said you cannot trust CA to hold that diamond to its setting for more that three to five years.
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Old Mar 23, 2015, 08:31 AM
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Central Kentucky
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Originally Posted by txt killer View Post
Use z-poxy finishing resin.
+1 Easy stuff to use and does not smell. Bondo is super smelly stuff and will permeate your entire house.
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