# Thickened Epoxy Recipes For Coosa/Divinycell ?



## MikeChamp12 (May 17, 2021)

I’m about to start rebuilding my skiff. There’s lots of epoxy resins and fillers. Has anyone had great luck bonding Coosa and/or Divinycell to existing hull ? Epoxy Brand? Type of Hardner? Any other additives or techniques would be greatly appreciated. Thanks in advance.


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## VANMflyfishing (Nov 11, 2019)

You can bond epoxy to other epoxies or poly resins. Don't use poly resin as it doesn't bond to epoxy. Make a paste/glue with epoxy and silica. You can find everything at US composites for epoxies. I Would us the fast hardener. Wet out the Divinycell really well, wet out whatever you are sticking it to with the epoxy silica mixture, and clamp it down. Depending on hull shape, Divinycell is probably easier.


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## bryson (Jun 22, 2015)

When I doubled the core on the inside of my hull I wet out all the bonding surfaces with neat resin, then before it cured I troweled on putty made with cabosil (and some milled fibers for good measure).

Then I immediately put my core down. I had lots of vent holes so that I didn't trap any air pockets. I weighted it down and once it all cured, I went around and tried to find voids by tapping or visual inspection. Anywhere I was even slightly suspicious, I drilled a hole through the core and injected thickened resin (not too thick, or it won't flow well enough).

I'm sure there are many ways to do it, but this process seemed to work really well for me. I have heard others also use a single layer of cloth or mat between the core and bonding surface -- I think that would probably work pretty well too, especially if you are adding core to a totally un-cored area.


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## MikeChamp12 (May 17, 2021)

Thanks for the response guys. Any particular brand? I was just going to use West Systems.


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## VANMflyfishing (Nov 11, 2019)

I like US Composites, but West Systems in fine. One thing you could do is drill vent holes every 2"-4" and the epoxy will seep through. I used mat-10oz cloth-mat for doubling my transom. Its hard as a rock. I wouldn't hesitate putting at 150 on my skiff! If you are doing the transom, I like mat, but it's not needed.






Epoxy : Epoxy Resins and Hardeners


Wholesale/retail sales of composite and fiberglass materials, including epoxy, adhesives, carbon fibers, urethane foam, urethane casting rubbers



www.uscomposites.com


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## Sam K (Apr 24, 2020)

Also keep in mind, especially faster cure epoxies, will kick off very quickly in this hot weather. In my experience silica causes it to trap the exotherm and kick faster. Stuff like fillets can harden to a point of being difficult to work with in a matter of 20 minutes. You don’t want to end up with cured silica that needs sanding under any circumstances, it’s terrible. Excellent ventilation is a must and work on small areas at once. Any time the fillers come out, the respirator goes on, especially the silica as it is really nasty stuff for your lungs. 

I’ve used 4 kinds of epoxy now and us composites epoxy resin is as good as anything else as far as I can tell and will save you a ton of money. I use the medium hardener pretty much exclusively. I also like fiberglass Florida’s resin because it has very little odor and their slow hardener is my preference there. I prefer to use Q cells whenever possible over silica because they’re less dangerous for your lungs and tend to use all Q cells for fairing, equal parts Q cells and silica for fillets, and all silica for bonding things together. You can start with roughly 3 to one ratio filler to mixed epoxy and adjust as you like depending on the application and your preferences. Q cells and aerosil silica are pretty much all you need in terms of fillers, again FGF or US composites will hook you up with them. In my experience the folks at both (ask for Mandy at FGF) are very helpful and know their products well. I was confused by all the products out there when I started out but I’ve realized you really can do anything with a good resin, Q cells, and aerosil. I hope that ramble is helpful, good luck and feel free to message me if you want!


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## Sam K (Apr 24, 2020)

For bonding core to the inside of your boat, vacuum bagging it down would be ideal but I’ve also had success just screwing it in place with plenty of drywall screws and vent holes. The screws always come right out. Obviously you need a solid surface underneath that you don’t mind putting a void into, and you have to fill that void with thickened resin before you glass over top of the core


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## MikeChamp12 (May 17, 2021)

Thanks everyone this is very helpful.


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## Sublime (Oct 9, 2015)

I've been US Composites epoxy as well with the slow hardener. I have had ZERO blushing issues.


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## JC Designs (Apr 5, 2020)

All great info thus far! Here is how I would do it…

For the optimal bond and strength, wash surface with soap and water and rinse thoroughly, grind old glass with 36 grit until no shine, wet out all surfaces to be bonded using neat epoxy and allow to tack up and cool down, here it can get tricky…

Slightly thicken some epoxy with fumed silica and roll out some 10oz cloth onto the hull surface to be cored “don’t worry about adding weight as you ground out more than you are putting back”, wet the cloth out with your slightly thickened epoxy and leave it plenty wet for bonding, now do as mentioned… lay your drilled core onto the wet surface and weigh it down with as much weight as you can. Clean up all resin that spooges out and allow to cure. The glass will reinforce you bonding resin while adding structure to the matrix.


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## JC Designs (Apr 5, 2020)

Also, US composites, Marine Epoxy, or just about any other brand will be far less expensive and just as good as west!


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## MikeChamp12 (May 17, 2021)

Thanks @JC Designs. Also enjoy your YouTube channel


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## K3anderson (Jan 23, 2013)

JC Designs said:


> All great info thus far! Here is how I would do it…
> 
> For the optimal bond and strength, wash surface with soap and water and rinse thoroughly, grind old glass with 36 grit until no shine, wet out all surfaces to be bonded using neat epoxy and allow to tack up and cool down, here it can get tricky…
> 
> Slightly thicken some epoxy with fumed silica and roll out some 10oz cloth onto the hull surface to be cored “don’t worry about adding weight as you ground out more than you are putting back”, wet the cloth out with your slightly thickened epoxy and leave it plenty wet for bonding, now do as mentioned… lay your drilled core onto the wet surface and weigh it down with as much weight as you can. Clean up all resin that spooges out and allow to cure. The glass will reinforce you bonding resin while adding structure to the matrix.


I did this exact process (despite not believing JC) and it's incredibly strong.. Of all the epoxy I've used, I like Raka.


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## JC Designs (Apr 5, 2020)

K3anderson said:


> I did this exact process (despite not believing JC) and it's incredibly strong.. Of all the epoxy I've used, I like Raka.


At least you’re honest😉🤣


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## DuckNut (Apr 3, 2009)

K3anderson said:


> I did this exact process (despite not believing JC) and it's incredibly strong.. Of all the epoxy I've used, I like Raka.


What the heck does JC know- he is swapping out his brain in a couple weeks. 

Raka is good stuff.


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## JC Designs (Apr 5, 2020)

DuckNut said:


> What the heck does JC know- he is swapping out his brain in a couple weeks.
> 
> Raka is good stuff.


Less than that buddy, and if I have another seizure they are going in sooner!😔


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## DuckNut (Apr 3, 2009)

JC Designs said:


> Less than that buddy, and if I have another seizure they are going in sooner!😔


You know I've been talking to the big man on your behalf.


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## JC Designs (Apr 5, 2020)

DuckNut said:


> You know I've been talking to the big man on your behalf.


Yes sir I do, thank you!🙏🏻


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