thickened epoxy

[diving in]

Hello all,
As I get closer to starting the recore project on Whim (Triton #122) I'm trying to walk though the process in my head to make sure I do it right the first time. After reading about other's projects I'm still a little unclear about what is meant by "thickened epoxy" in the following applications.

1. When filling the void between the top and bottom deck skins, adjacent to the new core, with thickened epoxy; what is the best filler to use in the epoxy and what consistency should I look for?

2. When spreading thickened epoxy onto the top of the bottom deck skin in preparation for bedding the balsa core into place; do I use a filler and if so what is the best to use?

Thanks,
Steve

[Hirilondë]

You are using the epoxy as an adhesive, so you want an adhesive filler. You are thickening it to help it bridge gaps and reduce drooling and dripping. I suggest cabosil, which if you are using West System fillers is #406. When you get to fairing it becomes a whole new ball game. Cabosil makes the cured epoxy hard as a rock and a royal pain to sand.

[David]

Here is West Systems' definition of their fillers and use:

http://www.westsystem.com/ss/fillers/

Good luck with your project,

David

[diving in]

Thanks for the replies! I hope to get started soon.
Steve

[Rachel]

And to step backwards from the specific, I believe "thickened epoxy" always means epoxy with some kind of filler added (or mixture of fillers; you can blend them to get properties of a couple of types in one batch).

"Thickened" epoxy without fillers means your container is about to smoke, deform, and melt ;) Toss it like a grenade...

R.

[bcooke]

Toss it like a grenade...

Preferably into the neighbors Hunter.

Oops! did I say that out loud?

[Rachel]

:snark:

[okawbow]

Hello all,
As I get closer to starting the recore project on Whim (Triton #122) I'm trying to walk though the process in my head to make sure I do it right the first time. After reading about other's projects I'm still a little unclear about what is meant by "thickened epoxy" in the following applications.

1. When filling the void between the top and bottom deck skins, adjacent to the new core, with thickened epoxy; what is the best filler to use in the epoxy and what consistency should I look for?

2. When spreading thickened epoxy onto the top of the bottom deck skin in preparation for bedding the balsa core into place; do I use a filler and if so what is the best to use?

Thanks,
Steve

I make archery bows for a living, and use a thick epoxy called "Smooth-On" It is a 2 equal part epoxy made especially for gluing wood and fiberglass. The part A is like vaseline and part b is like thick honey. It need to be used in 70 degree plus temperatures and has a 1 hour pot life. It sands well after curing. It cures in 24 hours. I buy the 2 gallon kits for under $150.00. I plan on using Smooth-on when I recore my Bristol 24 deck. You can get it from Bingham Projects, Inc. in Utah www.binghamprojects.com

[Oscar]

your container is about to smoke, deform, and melt

I've done that.......

An even more fun epoxy story is when I bought an old Catalina 30 with the engine bed (pressure treated 4x4's before the pan days) loose. So engine out, 4x4's out clean up and start glassing back in. At some point I leaned into the bilges and put my hair in a thick layer of thickened epoxy.

I had two choices.... let it cure and get a crew cut. Not fashionable in 1990. Or, take the acetone and go to the showerhouse. In the middle of the whole operation a guy walks in with a cigarette. He knew enough to leave again....quickly.

[okawbow]

Hello all,
As I get closer to starting the recore project on Whim (Triton #122) I'm trying to walk though the process in my head to make sure I do it right the first time. After reading about other's projects I'm still a little unclear about what is meant by "thickened epoxy" in the following applications.

1. When filling the void between the top and bottom deck skins, adjacent to the new core, with thickened epoxy; what is the best filler to use in the epoxy and what consistency should I look for?

2. When spreading thickened epoxy onto the top of the bottom deck skin in preparation for bedding the balsa core into place; do I use a filler and if so what is the best to use?

Thanks,
Steve

I make archery bows for a living, and use a thick epoxy called "Smooth-On" It is a 2 equal part epoxy made especially for gluing wood and fiberglass. The part A is like vaseline and part b is like thick honey. It need to be used in 70 degree plus temperatures and has a 1 hour pot life. It sands well after curing. It cures in 24 hours. I buy the 2 gallon kits for under $150.00. I plan on using Smooth-on when I recore my Bristol 24 deck. You can get it from Bingham Projects, Inc. in Utah www.binghamprojects.com

By the way, there is no danger of the "smoking glue bomb" with the Smooth-on epoxy. It can be used to make thick castings. It's very strong an slightly flexible when cured, so I would expect it to be ideal for re-coring work.

[bcooke]

Based on what I have just read from the manufacturer's website I am not so sure about using Smooth-on in composite structural repairs. The company markets a whole bunch of products and several epoxies but most of them are geared towards mold making. (and yes, bow making)

The Smooth-On physical properties data for their adhesive epoxy mix shows the tensile strength as only a fraction of, say, West System. There are other attributes to consider but there isn't any indication on the website that makes me think Smooth-on products are in any way the equal (in the application we are talking about) of West, System 3, MAS, etc.

The castable epoxies that don't overheat are not designed for structural applications.

[edit]
On a second look, the castable epoxies actually come closer to replicating West System data. But these aren't considered 'adhesive epoxies' by the mfg so I have my doubts.

Just my thoughts.

[bcooke]

had two choices.... let it cure and get a crew cut.

I would definitely shave before I washed my hair with acetone. Yech.

Then again, people often refer to me as a trendsetter...

[okawbow]

Based on what I have just read from the manufacturer's website I am not so sure about using Smooth-on in composite structural repairs. The company markets a whole bunch of products and several epoxies but most of them are geared towards mold making. (and yes, bow making)

The Smooth-On physical properties data for their adhesive epoxy mix shows the tensile strength as only a fraction of, say, West System. There are other attributes to consider but there isn't any indication on the website that makes me think Smooth-on products are in any way the equal (in the application we are talking about) of West, System 3, MAS, etc.

The castable epoxies that don't overheat are not designed for structural applications.

Just my thoughts.

Just how much strength is needed in a core repair? And what kind of strength; compressive or shear? A longbow exerts tremendous forces on the glue joints during drawing and shooting. I have never had a glue failure. I have had wood failure. I can't imagine balsa wood being stronger than any epoxy glue. The wood will shear long before you have a glue failure. Some bowyers have used West system epoxy for laminating. It had a higher failure rate than Smooth-on. I've used smooth-on under a couple of stantions with excellent results. Easy to use and cheap. I would think it would be especially good for cores if the balsa was replaced in small squares with a 1/4" gap all around them and filled with epoxy. That would eliminate the chance of large delaminations in the future.