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Hot box with an open box and exhaust fans

post #1 of 23
Thread Starter 
Been planning and thinking about building a hot box for about 3 years.

What about having fans exhaust the air out the front and thus act as a heating unit for the tuning area? I'd leave the back open and up almost against the wall for air intake.

I know there would be a lot of heat loss, so I'd use more and maybe brighter bulbs. Do you think I'd get enough heat out of this, both for the skis and to add some heat to the air right around it?

I'm thinking of mounting it under my workbench.
post #2 of 23
I've played around with a few different hot box designs & think that you'd definately loose too much heat with any noticeable opening in a lamp powered box.
post #3 of 23
Thread Starter 
Hey Jon, your box is actually an inspiration for me with the clear front and under counter installation.

Do you know if that guy still sells the heating unit?

Do you think if I used that and fan vented to the outside that I could keep sufficient heat inside?
post #4 of 23
I dont think its a good idea, mine has a true heater and if I leave the box open it never gets hot enough to do the job, and my box is fully insulated and lined with reflective material.

Build the hot box and get an area heater if needed. IMHO
post #5 of 23
Thread Starter 
I have a wall mounted Modene heater that runs off the furnace in the garage and a big plastic sheet running across the back of the garage so it only needs to heat that area.

Thing is I don't want to use the furnace this year, plan on heating with wood as much as possible.

OK, how about instead of open back, if I just have some inlet vents and a fan on the front exhausting air. Still think it wouldn't get hot enough?
post #6 of 23

Not likely...

Quote:
Originally Posted by SkiMangoJazz View Post
I have a wall mounted Modene heater that runs off the furnace in the garage and a big plastic sheet running across the back of the garage so it only needs to heat that area.

Thing is I don't want to use the furnace this year, plan on heating with wood as much as possible.

OK, how about instead of open back, if I just have some inlet vents and a fan on the front exhausting air. Still think it wouldn't get hot enough?
...what everybody said above is basically where it's at: If you don't have a sealed box, it's going to be pretty hard to keep consistent heat. Take a look at the Toko site. They want pretty high temps (130 - 140 F). I think this is a little aggressive. Mine does the job at 120 degrees. Anything less than that is a waste. I started off with a bulb arrangement that produced 100 F, and it did nothing. On my design, which is pretty much a close knock-off of the design from the Tognar toolworks site, the idea of the fans is to cycle the air in the box, much like a convection oven. You really aren't trying to pull in fresh air and exhaust heated air...that's pretty much the opposite of what you want to do. Boxes are easy to make, but time consuming. Once you have one that works, though...all you have to do is wax, crank on the box, insert skis, crack and beer and watch WC racing on TV...
post #7 of 23
I find it peculiar that people use bulbs for heating in this application. I'm not aware of any particular effect visible light has on wax, but it is certainly difficult to achieve even temperatures across high aspect ratio items using a few point sources of substantially radiant heat. For one thing, the center of the

Minimizing any thermal gradients or local hot spotting is difficult enough with forced convection. I've built a couple boxes in the last year and I wouldn't trust valuable skis to one without investing in several temperature measuring devices. A half dozen thermocouples and a noncontact thermometer is cheap compared to a fast pair of DH skis.

I think the appropriate use of lightbulbs in hotboxes is for admiring your work and seeing what you are doing when you load and unload them.

For the original question: Unless you need some localized source of warm air in your shop, I can't see any benefit in putting a hole in your oven. The energy you put into the box isn't wasted during winter in that it ends up as heat in the surrounding environment in any case. In summer it is waste. If you do need local warm air, you could build such a dual use device, but it will make the design more complex and expensive. You will need a lot more heat with any useful flow rate out of the box.

My opinions, still in development as I build, test, use these devices:
-Too much fan never hurt anyone. Too little fan is easy to achieve. Keep pressure ratio in mind. There really isn't anything at Home Depot designed to do this job...but don't let that stop you from trying.
-Any internal electrical/electronic devices including fans need to be rated for the conditions they will be subject to. I experimentally determined that electronic fluorescent lamp ballasts last for approximately 15 minutes at sixty degrees Celsius.
-Windows are nice.
-Controlling temperature accurately is easy. Controlling ramp rate is hard, especially if you want to be able to load varied numbers and sizes (masses) of skis. The thin layer measurement techniques needed to validate the importance of ramp rates (and ultimately the entire endeavor) are way out of my wheelhouse...can anyone help there?
post #8 of 23
I've never used one but have to wonder. I'd guess that they have to be safeguarded by thermostats not to exceed about 130 degrees (maybe even less?). Skis are made with plastics and fibreglass that is often held together with contact cement that is pretty suceptable to failure at moderately high temperatures. The tools used to take apart or delaminate laminate products is really nothing but a really powerful blow dryer (called a heat gun). I'd think you could seriously compromise the integrity of a ski if you exposed it to temps beyond 130 degrees for extended periods- beyond that of running an iron down it slowly.
post #9 of 23

See what I said...

...in the following:

http://www.rmmskiracing.org/articles...-03-Hotbox.pdf

http://www.rmmskiracing.org/articles...tbox-Part2.pdf

As you can see, what I did was pretty simple and straightforward, but it works amazingly well. I didn't want to do the lightbulbs thing, either, but my dad, who was an architect before he died, couldn't come up with a small heat source that would work as well or better. As I say in the article, I just dinked around with different wattages until I got it to a consistent temperature of 120 degrees F.

As you can see from the Toko site, they put their wax bag at 130 degrees, which they claim is optimum. I feel like that's getting into the range where you do begin to risk ski delamination and other bad things. Empirically, 120 degrees definitely saturates the base for me, and I think it's less risk for the ski construction. My local Atomic rep says to remove the bindings before hotboxing the ski (easy to do with Atomic bindings) because a hot box can cause bad things to happen with the (internal) binding lube. I don't worry about it with non-Atomic bindings, partly because I only do 120 degrees and also because I don't hot box a ski more than once or twice a season, if that. Once a ski is hotboxed, if I keep up with the basic waxing ritual, and I don't ski on WC ice all the time, the base stays pretty well impregnated.

One of the things I wanted to do in building my hot box was to keep it simple and affordable. So I didn't do much more than just follow the basic design I found on Tognar toolworks, with the few tweaks I mention in my article. It's a pretty simple job to put one together...just more work than I thought it would be...but that's the way the Deck from Hell project went, too...
post #10 of 23
There's no problems hot boxing at 120-160 degrees Farenheit. This is a relatively low temperature compared to the melting point of p-tex at approx 285F & the melting point of the epoxy resins used in ski construction of approx 310F. Even in a very well sealed & insulated box you won't get a soft base prep wax to melt consistently along the full length of the ski at much under 120F, with harder waxes requiring up to 160F.

For a consistent & an even temperature a decent fan is key, blowing air across the heat source - my box uses a small commercial blower & a 900W heating element. When the required temperature is reached the thermostat/control unit turns off the heating element only but leaves the fan running to give the convection affect described by SkiRacer55.

I've also put Vist & Atomic Neox bindings in the box at 140F will no ill effects & no loss/melting of lube.
post #11 of 23
I'm fairly sure bindings will be fine in a well implemented box. I'm also fairly sure UHMW PE is going to do things you would rather it not long before it actually melts.

I would be much more concerned about the behavior of plastic parts of bindings at high temperature than the lubricant. Even water is good to 100 degrees, after all. The service limit for a lot of plastics used in skis, bindings, bases is around 80 degrees.
post #12 of 23
Quote:
Originally Posted by Garrett View Post
I'm fairly sure bindings will be fine in a well implemented box. I'm also fairly sure UHMW PE is going to do things you would rather it not long before it actually melts.

I would be much more concerned about the behavior of plastic parts of bindings at high temperature than the lubricant. Even water is good to 100 degrees, after all. The service limit for a lot of plastics used in skis, bindings, bases is around 80 degrees.
I hadn't put any thought in to extreme heat effects on bindings. I'd agree that the plastic and hardware in bindings is safer than the adhesives holding a ski together.

But, I can see the problem with the lubricant. The grease could melt and get runny, then drain out of the binding instead of sticking to the components like it does its lower temp gooey state
post #13 of 23
So, I haven't ever hot boxed skis. Has anobody that does gone and checked the grease under their bindings to see? I'm now very curious to see if it is a factor. In the end, it's no big deal to shoot some more grease in upon finishing the job. I usually do that to all my bindings about twice a year anyway.
post #14 of 23
Some of the grease melted, not all, but I go on the upper end as far as heat, I like to keep the wax in a liquid state. No delaminations, but as I mentioned in a post a few months ago some of the goo used to mount the VIST WC plate to my skis oozed out.
post #15 of 23
Quote:
Originally Posted by crgildart View Post
Has anobody that does gone and checked the grease under their bindings to see?
Yes. It is fine. The dropping point of typical binding greases is hotter than you should be getting them in a hot box. I don't know exactly how hot because I've never gotten it there, and I've never run a hot box over 70 degrees. Go ahead and test it with an old pair of bindings. My car gets to at least 60 degrees and I've never had a problem with skis stored in the car...and unlike most, I actually test and inspect my bindings.
post #16 of 23
Thread Starter 
I love it Richie - the goo oozed!
post #17 of 23

Check the Head GSs I just sent you...

Quote:
Originally Posted by SkiMangoJazz View Post
I love it Richie - the goo oozed!
...and you'll see the Vist Goo from Outer Space...
post #18 of 23
Thread Starter 
Wasn't there a Phil Collins song? "goo goo goodio"

(Thanks again for your incredible generosity btw!)

Four word press yore is all set now!
post #19 of 23

Coolness...

Quote:
Originally Posted by SkiMangoJazz View Post
Wasn't there a Phil Collins song? "goo goo goodio"

(Thanks again for your incredible generosity btw!)

Four word press yore is all set now!
...the first time you put those puppies on snow, I Strongly Recommend that you don't even try to turn them very much. Just find something wide, flat, and long and point 'em down and let 'em buck...
post #20 of 23
Garrett, What is ramp rate?

How thick insulation do you guys have in your boxes?
post #21 of 23
Thread Starter 
Quote:
Originally Posted by SkiRacer55 View Post
...the first time you put those puppies on snow, I Strongly Recommend that you don't even try to turn them very much. Just find something wide, flat, and long and point 'em down and let 'em buck...
Don't worry, because according to a former member here I can't even buy a turn anyways.
post #22 of 23
Quote:
Originally Posted by Christer View Post
Garrett, What is ramp rate?
How quickly (the rate) we go from room temperature to our desired process temperature (the ramp) and vice versa.
post #23 of 23
Christer

My insulation is fiberglass batting adhered to aluminum foil. Uncompressed its about 2" thick, the box itself is constructed out of 3/4" MDF (overkill). Were I to do it again, I would simply make a suitable metal frame to hold the brackets that support the skis and just build the entire box out of styrofoam insulation, then line it with reflective material. This would be cheaper, just as affective, and I would actually be able to move it. My box weighs well over 300lbs.
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