Smooth on EA40

[DaveMac]

I'm working onmy first laminated bow, and have a few questions before glue up. Is it OK to reheat the epoxy in a hot box, so I can glue up in stages?

Also does the hotbox curing make the glue stronger or just speed the process along?

[canopyboy]

There will probably be a few different responses, but my two cents is as follows:

Yes, you can reheat and glue up in stages. I glue up my risers first, and then the whole bow. Some people say that any future glue-ups need to be at a lower temperature than the first, but I have not seen where that is promoted by the manufacturer. Many epoxies break down at high temperatures, but those temps are usually well above their recommended max cure temperatures.

I've seen several people with convincing arguments and data that says that EA40 achieves the same strength regardless of cure temperature. It can just take a long time at low temperatures. I've also seen people swear that you need to heat cure to get full strength. I kinda believe the first group but heat mine for convenience and for the effect the heat has on the wood. (Press a stack of laminations and cook at 180 degrees for four hours without glue and you'll note that they have taken on much of the shape of the form. No heat means the residual stresses are still in your laminations.)

-Dave

[Bowjunkie]

I am in agreement with Dave.

[jsweka]

Trust Dave.  He's an engineer    

[Robertfishes]

Im not sure what you are planning to do..if you mean gluing up a riser then gluing up a bow with the riser in a form under pressure then I have done that with no problems..  if your parts are not in a form  then the heat from your oven will soften the glue and could cause a delam or twist if not done correctly.. I remember someone posting a picture of a bad twist when he over heated the end of his bow gluing on tips..the weight of a clamp twisted the end about 60 degrees when the epoxy softened

[Trux Turning]

Like the other guys said- it's ok to reheat the epoxy in the hot box just make sure everything is in the form under pressure and let it cool to room temps before taking it out. Here's some info about the glue from their web site:
WOOD LAMINATING / BOWMAKING
EA-40® has been used for many years for laminating fine woods. It is preferred by bow makers around the world and offers longevity, flexibility and memory required for making award winning performance bows.
Suggested laminating procedure;
1. Plane or lightly sand all surfaces to be laminated with 120 grit sand paper
2. Blow off dust with compressed air and wipe all surfaces clean using acetone (Warning – acetone is flammable. Follow acetone manufacturer procedures for handling). Let acetone evaporate for 10 minutes.
3. Mix and apply EA-40® as directed between layers of laminate to sanded surfaces using a brush.
4. Carefully clamp laminated pieces together applying even pressure. 5. Place in oven and use the following step-cure schedule:
Important; Let cool for at least 6 hours to room temperature before releasing clamps or handling.
Temperature
Duration
120°F / 48°C
2 hours
150°F / 65°C
2 hours
185°F / 85°C
2 hours

[mikkekeswick]

Trux - that's the info you want.
Any and all glues have a datasheet - just email the manufacture and they will send you one. Straight from the horses mouth and you know it's definitely right and based on scientific testing.