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Main Boards => The Bowyer's Bench => Topic started by: Archer Dave on September 03, 2016, 10:45:00 AM
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I was wanting to check with you guys about what is the minimun requirment for curing bows after glue up. I live out a ways off grid and only have solar for power in the workshop.
I am guessing that I will have to run the generator while it cures in the oven box. However I would like to be able to limit the time perhaps or power draw to accomplish this.
I was thinking I can super insulate the oven box. Maybe have a this foil backed foamboard on the inside with 2" foamboard over that. How many bulbs might I need with this setup to reach and maintain the proper temp?
What would be the quickest curing epoxy that still is good? I noticed Bingham says Smooth On needs 4 hours while others talk about as much as 8. Which is it?
Thanks a lot.
Dave
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If you have good sun exposure why not make a solar hot box. You could probably get to 150 degrees and maybe higher.
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Thanks Pat. That might work in warmer days if I could figure out a way to regulate the temp. However I live in Northern Minnesota, so before long we will be down to -30F and I don't want to chance it.
My home solar system could handle the oven without a problem but the workshop is to far away to run a cord. Not sure I want to do curing in the house thought with three little kids, and a new house I am almost done building.
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Smooth On and unibond800, both of which I use, will cure in 24 hours at 70 degrees. The odor really isn't bad.
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I use Smooth On all the time with no hot box, just let it cure at room temp for 24 hrs. In the winter I bring the bow into the house to cure. Make sure it's wrapped in plastic wrap so it doesn't drip on floors.
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Good point Dan, the plastic wrap will cut down on what little odor there is too.
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Thanks guys. Will the Smooth On and Unibond 800 still be as good if not baked? If so why bake?
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Of course you bring bow in the form into the house. Most are aware of this but some may not.
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I found this on the Smooth On website.
GENERAL PURPOSE BONDING APPLICATIONS...
Application --
Apply to prepared surface and let cure for 24 hours. Applying mild heat will cure EA-40® faster – 150°F/65°C for 6 hours.
Post Curing --
After EA-40® has cured at room temperature, heating the epoxy to 150° F (65° C) for 4 to 8 hours will increase physical properties and performance. Let cool to room temp. before moving bonded substrates, machining, etc.
To Attain Maximum Heat Distortion Temperature - let cure for 24 hours at room temperature, heat cure for 2 hours at 250°F (122°C).
At mix ratio 1A:1B – HDT will be 163°F (73°C).
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:
Temperature Duration:
120°F / 48°C 2 hours
150°F / 65°C 2 hours
185°F / 85°C 2 hours
Important; Let cool for at least 6 hours to room temperature before releasing clamps or handling.
Like you guys said, it looks like it will be fine to not bake and allow it to cure for 24 hours at room temperature.
However, from their literature it would look like heating it makes the epoxy have better properties.
I wonder though how much of a difference it makes and if I should try to figure out a way to operate an oven in my conditions or just let it air cure?
Dave
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AS long as you keep the ambient temp above 70F during the 24 hour cure, you absolutely do not need a bow oven.
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Dave, since you're off grid, why don't you build a solar oven? Instead of installing a lid that has lights in it, build a lid with a window, preferably double pane. A couple of metal reflectors can be used to reflect more sunlight into the box and a couple of adjustable vents can control temperatures inside. It should do well enough from March until October.
I'm looking forward to moving out into the country and this is one thing on my list of things I want to build.
Dave.
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I have been setting aside some materials for a solar hot box. No sense in running light bulbs when the sun is already cooking, but until I get that project built, the old van gets pretty hot on sunny days :)
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I know one famous bowyer that wrapped his forms in black plastic and put it out in the sun on his driveway it got hot and cured . Ive been building bows for more than 30 years, from my experience you need to heat your smooth on if you want heat resistance such as hot car etc. after curing. Mix slightly more part a than b .
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Thanks guys. However I do not think the solar thing will work when it is -30F outside though. I wont have the shop set up till winter so that is kind of my dilemma with the heat box thing. I am thinking I just might have to keep the shop 73F when I want to let the bows cure are room temp. That or run the generator for 4-6 hours, which really is not that big of a deal I guess since the gen only burns a gallon per 4 hours.
Thanks
Dave
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I've built probably 12 laminated bows with smooth on and have never heat cured. I've only had one failure of the glue bond (swap bow I sent to woodcarver2 popped the riser off) but I suspect that it was a surface prep issue.