Primitive Archer

Main Discussion Area => Bows => Topic started by: deermaster on July 17, 2007, 05:27:56 pm

Title: heat box plans?
Post by: deermaster on July 17, 2007, 05:27:56 pm
does anyone have plans for a heat box for curing epoxies like bowgrip 100 and smooth on? i would like the plans and your method for regulating the temerature.thanks for any info!
Title: Re: heat box plans?
Post by: Jesse on July 17, 2007, 07:58:12 pm
I dont have plans Ive used recorsinol glue without high heat but Im prety sure all you need is a piece of stove pipe, a cheap heat gun, and a thermometer. Im sure someone else will give better instructions than this.
Title: Re: heat box plans?
Post by: Pat B on July 17, 2007, 09:16:59 pm
I got my plans from Bingham. I use 4, 200w light bulbs with a 168deg thermostat from Binghams. I usually don't need it that hot so I unscrew bulbs until I get the heat down where I want it. One light bulb will keep the box at about 100deg. My box is 3/8" plywood and I added 1/2" foil backed insulation board to all sides, a fan inside and a 1" hole at each end for venting moisture when drying wood. I plug it for heat curing glue.    Pat
Title: Re: heat box plans?
Post by: duffontap on July 18, 2007, 11:44:08 am
"Hot Box Wood Dryer" by Greg Harris Vol. 3 issue 3.  Check the store to see if the issue is availible.  It may not be.

         J. D. Duff
Title: Re: heat box plans?
Post by: rudderbows on July 18, 2007, 05:50:49 pm
An easy oven is some 6" single walled stove pipe and a heat gun, ( any heat source that can stay on for more than 4 hours is good including propane blowers. Use a cheap meat thermometer on the far end from the heat source to tell you how hot the air is exiting the pipe. Back off the heat when it hits 185-200 degrees.  Cook for 4 solid hours after getting up to speed.  MAKE SURE TO KEEP THE BOW AT LEAST 2 FULL FEET AWAY FROM THE HEAT SOURCE OR IT WILL FRY. !! Use 8 feet of stove pipe.
 Wrap it completely with shrink wrap to keep it from drying out. That's how we do our bows when we are curing only one or two and it works great. We use a much larger box for larger numbers of bows, but thats a different story in itself. Hope this has been helpful.
Title: Re: heat box plans?
Post by: tradrick on July 18, 2007, 06:48:55 pm
PatB,would the type of box you have be better suited for force drying a stave for bow building.Such as leaveing a stave in there for a week or two at maybe a lower temperture but have constant heat on it.I'm refering to drying hickory.Thanks tradrick
Title: Re: heat box plans?
Post by: duffontap on July 18, 2007, 06:59:38 pm
I use my hot box to cure selfbow staves.  Mine is just a 7' x 18" x 18" box with 4 basic porcelain fixtures.  I use 4, 60 wt. bulbs and the whole system is on a dimmer switch.  I dim them way down to keep the temp below 100 degrees.  It saves a LOT of money on your power bill and the light bulbs last forever when they're dimmed down (as opposed to two weeks when they're not).  You wouldn't think it, but the cost of electricity and light bulbs can really add up if you don't take pains to be efficient. 

          J. D.
Title: Re: heat box plans?
Post by: tradrick on July 18, 2007, 07:09:50 pm
Thanks J.D. I've got a pretty good idea of what I need now.Learning alot from this site and lovin every minute of it.tradrick
Title: Re: heat box plans?
Post by: Pat B on July 18, 2007, 10:13:43 pm
I added the 1" holes at either end of my box(one on top, the other on bottom) to allow moisture to escape while curing staves. A small fan inside helps to dry the wood quicker also. Each box will be a little different depending on temp and humidity so when you get one built you will have to tweak it to suite yourself.    Pat
Title: Re: heat box plans?
Post by: deermaster on July 19, 2007, 04:54:18 pm
thanks for the help!
Title: Re: heat box plans?
Post by: Justin Snyder on July 19, 2007, 08:24:30 pm
Wow JD, under 100*, I need to put an air conditioner in the box to get down to 100*.  ;D   On a serious note.  The dimmer switches have been shown to use the same amount of energy.  The energy not used in producing light creates extra heat in the switch itself.  Use 40W or 30W bulbs if you want to save energy and reduce heat.  Justin
Title: Re: heat box plans?
Post by: duffontap on July 19, 2007, 09:56:05 pm
Really?  I before I switched to the dimmer switch my energy bill would spike on months I was using the box.  I may be reading into it.  I'll do a little research. 

      J. D. Duff
Title: Re: heat box plans?
Post by: duffontap on July 19, 2007, 10:08:05 pm
Justin, I think that only applies to old, non-transformer style switches.  I'm not sure but the consensus seems to be that it does use less energy.  If the energy is being absorbed by the switch, that would be a huge fire hazzard.  Scary thought. 

(Online sources, note what they say about bulb life too!):

8. Do Dimmer switches save energy?

Yes, most dimmers today do save energy. Older dimmers used to simply cook off the power you did not want to use. Today's dimmers interrupt incoming current thousands of times per second (invisible to the human eye) saving 10% in energy costs even when on full, the life of your bulbs is also greatly increased.

From "8 ways to save energy":

Want to affect the mood and save energy? An effective way to quickly change the mood of a room is by dimming or brightening the lights. A softer light results in a more comforting, relaxing atmosphere. Brighter lighting is more suitable for normal room use and reading. An easy way to control your lighting is to install a dimmer switch. Dimmers also reduce energy consumption by cycling light and increasing bulb life.

Most dimmers cycle the light on and off 120 times per second faster than your eye can detect. The longer the light is ON versus OFF, the brighter the light output. Likewise, the longer the light is OFF versus ON, the lower the light output and the greater the energy savings. An added bonus is the incredible increase in bulb life from operating at a lower light output (filament temperature). Dimming the light by just 10 percent more than doubles the bulb life.
Title: Re: heat box plans?
Post by: MattE on July 20, 2007, 06:08:54 am
Why would you want a dimmer switch on a heat box when you can use a thermostat instead? You still have to check your temperature if using a dimmer switch, you don't with a thermostat. You can buy a thermostat but any used one will do, they hardly ever wear out. Toaster ovens, water heaters and any appliance that has a heat control knob has one. I personally like water heater thermostat and you get two from them as well.Think thermostat not dimmer switch!
Title: Re: heat box plans?
Post by: Pappy on July 20, 2007, 10:12:38 am
Good idea Matt,I now and have for several years used a dimmer set up like JD but my boxes are out side in my bow shop so I am constantly having to adjust the heat when the Temp. changes
so I may give that a try.I guess if the box was in a controlled temp. you could pretty much set it and would stay about the same but mine is not. :) ???
Title: Re: heat box plans?
Post by: duffontap on July 20, 2007, 11:44:47 am
You've got a good point Matt.  My heat box stays in my insulated shop so I never have to mess with it.  In my case, the dimmer switch I had on hand works great, but a thermostat that was trustworthy would be really nice.  The reason why I didn't use one was household furnace thermostats don't go high enough, and other thermostats have such a range I worry that they won't keep my box within the 5 degree range I want it at.  I have a thermometer in the box at the level of the bows so I can make sure I'm getting the temp I like.  I'm always open to improvements though.  :)

          J. D. Duff
Title: Re: heat box plans?
Post by: Justin Snyder on July 20, 2007, 12:05:40 pm
JD, there is no doubt that the new dimmer is more efficient than the old.  But lets not forget there is energy lost every time a switch is flipped, energy to run the switch. It produces heat in the switch just like in the bulb. In not suggesting the new dimmer with a 60W bulb is not more efficient than a 60W left on.  But a 30W will still be more efficient.

According to Advanced Technologies, who does the actual testing, there is some misleading info on dimmers.  The bulb is not actually turned off. The dimmer switching on and off just decreases the height of the sine wave, decreasing the power to the bulb. Because a bulb or appliance is not being supplied with the correct amount of power when it is on, it decreases the life of the bulb or appliance. Inefficient use does not necessarily relate to net savings. Example, if a fan is switched to medium, it requires less energy in 1/2 hour than if left on high. However the fan left on high can run 1/2 the time to cool the room, thus using less energy. I think the thermostat is the best option by far.  I know I'm a bit anal.  I am getting ready to start building my new "Green" home. A little up $ front can save huge later on. Might even pay for a caribou hunt. ;) ;D

Pappy, I would recommend a box outside anyway. Even if your wife don't mind the huge new piece of furnature.  ;) A box inside the house heating to 100* can sure add to the cooling bill. Just make sure your fan is wired on a seperate switch. It would be silly to reduce the air flow, since constant air flow is what the fan was added for anyway. Justin
Title: Re: heat box plans?
Post by: MattE on July 20, 2007, 01:14:37 pm
I don't see any pronlem with the dimmer switch method but if you use four or more bulbs of high wattage it will build up resistance and could catch fire.If you opt for a thermostat and incorporate a minature fan to keep the air flowing you will have accurate temps plus eliminate the possibility of resistance on the system and the chance of a fire.
Title: Re: heat box plans?
Post by: welch2 on July 20, 2007, 01:16:06 pm
Justin , I think you are both partly right. I've worked in electronics my whole life. you are right in that a dimmer 'cuts the sine wave' this reduces voltage. And it is detrimental to most devices. But a light bulb is just a piece of wire in a vacuum . You run current though this wire till it gets hot enough to emit photons (light). works like a feather burner.
   So here is where JD is right, in the heat box you don't care if the the bulbs light up dim or bright , you just want it's heat.The light in this case is wasted energy. JD's dimmer method will extend the life of the bulbs , because at lower voltages they don't get hot enough to burn the elements in two. Notice that light bulbs are not only rated by wattage , they also have a voltage rating. In a given light fixture the same wattage bulb with a higher voltage rating will last longer.
   But the dimmer does distort the waveform , and depending on the quality of the dimmer could have several switching spikes or other anomalies to the waveform that shorten the bulb life some.  Better than a dimmer ,find an old autotransformer or variac, these are adjustable transformers that allow you to adjust the line voltage up and down.
   So I think a thermostat ,even a fixed one like Binghams sells, is the most efficient on your power bill, but  a dimmer or a variac will make the bulbs last longer .Combining the two may be the best bet.

Title: Re: heat box plans?
Post by: Justin Snyder on July 20, 2007, 02:30:41 pm
Hey JD, I have a thermostat that has a 1/10 degree variance.  Its not really cost effective for a hot box at $70.  ;D Justin
Title: Re: heat box plans?
Post by: duffontap on July 20, 2007, 05:30:21 pm
Thanks so much for the info Ralph.

Here's where I'm at on this.  I posted the suggestion of the dimmer switch because it has lowered my energy consumption and greatly extended my bulb life.  I guess I'm just willing to squander the amount of electricity needed to power a dimmer switch.    My system isn't perfect but it beats controlling the temp. by venting (my old system) and I get to use the ultra-cheap 60 wt. bulbs I have in the pantry. 

Secondly, controlling the temp. by using lower-wattage bulbs has its down sides as well.  If you have to run lower-wattage bulbs at full power you may be getting less life out of more expensive bulbs, and have to let heat escape your box to control the temperature. 

Thirdly, while I totally agree that an accurate thermostat would be the way to go, I think my simple system gets me 90% of the way there and it's done.  I'm slightly suspicious that the $50 thermostat (plus S & H) from Bingham Projects would pay for itself in energy savings after about 400 years. 

Lastly, for many of us the object is to avoid any unnecessary expense.  I built my hot box out of construction debris I scrounged so it fit within my anual archery budget of approximately 5 bucks.  These drying boxes can be totally safe and respectably efficient without foil backed insulation and expensive fixtures, bulbs and thermostats and for some people it's worth the trade-offs of not having the 'ultimate' system that Bingham projects sells plans for. 

Justin--1/10 of a degree isn't good enough!!!!!!   ;D ;D ;D
          J. D. 
Title: Re: heat box plans?
Post by: MattE on July 20, 2007, 07:10:27 pm
J.D. I just happen to have an extra thermostat if you want it is yours!
 I will have to find it, I cleaned up my shop and now I am lost along with the thermostat! :)
  It is out of a hot water heater.