:: View topic - heated ski press

Hey all,

First off, this site is incredible. It is the best resource I have come across.

I am trying to see if anyone has found a way to add heat to their press. I know the big ski/snowboard makers use metal heat platens which are built into their presses, but that is too expensive.

I am thinking of using ceramic infrared emitters. I know these are used to cure paint and other things.

I talked to a guy at BriskHeat about silicone heat blankets but I don't think they are going to work.

If anyyone has found a solution that isn't too much $$$, let me know.

Thanks,

Jordan

BTW the snow's comming........

I know that some professional ski press use hot water pipes (I suppose copper) to heat up the mold.

I think I was wrong about the silicone heat blankets. I think they might work.

I don't know if anyone else is/has tried to use them, but I think I'm going to give them a try. If anyone has used them with bad results let me know.

-jordan

my question is why would you think they wouldn't work?

To: Guest.

That's one of the things this forum is for. To post ideas for other to critique. If someone has already tried a silicone heat blanket but (for example) had issues with mantaining consistant heat at 170* F then D*MINION wouldn't have to discover that the hard way, or he could plan for the expected problem.

I for one have some electric heating elements which I plan to use to heat a small enclosure which I will roll my press into once the ski is layed up. The only obsticle I have yet to overcome is that of the proper thermostat for 170-180*F. I am going to go visit with an appliance repair shop to see if a regular oven thermostat may be used successfully in my ski press oven. Then hopefully he will let me scrounge a used one for cheap, or free.

I see no reason that this shouldn't work (Guest) but if anyone has sees any contraindications to using this big oven method, by all means, speak up. Thanks. -Jed

Hose-man -

I appreciate your comments, and I am FULLY aware as to what this forum is about.

I think you took my question out of context ...but that was most likely my fault.....I took his (Dminion) statement as ..he spoke to a manufacturer..and after doing so thought the silicone blankets wouldnt work..... I wanted to know what the manufacturer said ...if that was the case.... that changed his mind. Was it cost ..volatge requirements ...etc etc..

..sorry if I wasnt clear.

no worries Guest. Looks like I read you wrong.

I contacted a manufacturer (the first on a google search of silicone heat blankets) if they would work between 50 and 100 psi. He says that as long as the pressure is even it would work and they seem to have a well thought out temperature control setup. Hope this helps.

Ben

I dont believe the site was the first result from the google search so here it is http://www.briskheat.com/ I hope this can make the process easier, let me know how it works out if you try to go this route.

Ben

here are some more:

http://www.benchmarkthermal.com/flex.htm

http://www.watlow.com/products/heaters/

Hey all,

The reason I'm flip flopping with the heat blankets was that I assumed after intially talking with the manufacturer that the blankets could not withstand the pressure of my press (80-100psi). Then I asked them directly if it could withstand up to 100psi and they said yes, but only if the pressure was evenly distributed. So I'm thinking it can work b/c if I put it between the bladder and the top pressing sheet in my press the pressure would be even.

However, I just got off the phone today with the manufacturer and by "evenly distributed" he also meant the heat blanket must lay flat and not kink at all or bend (this is a problem for the tips and tails and possibly even the slight arc of the camber. They are getting back to me if they think it can handle the arc of the camber) . Sooooo.........I'm still figuring it out if I can use it and it be safe.

So all this is to say that I 'm still talking with the manufacturer to work out the details of using a heat blanket. They have been real nice and are trying to see if they have anything that can work.

Hose-man: I thought of making an "oven" as well. You're going to have to let me know how that works. I was thinking of using infrared heaters in it (like a sauna, b/c they make accurate digital temp. control units for them), but I wanted to explore the heat blanket idea first.

Also, I am real new to this. I haven't even pressed a ski yet. But I cannot wait.....I 'm getting close.

snow is comming.......

-jordan

What about simply laying sheet metal down the length of the mold having some stick out. Then heating the metal from outside the press? We all know metal is conductive.

I've been working on this and just received my heat blanket the other day. I have the control box wired and running and the heater seems to work really well. I haven't put the blanket in our mold yet and pressed a ski, but will do so in the next week or so. There should also be an article soon about building the controller.

The blanket is very flexible and will withstand pretty much any pressure that you can apply. However, you can still puncture it with sharp corners or points.

Kelvin:

Cool, I really am curious about how the heat blanket will work. I actually never ended up ordering one b/c the manufactuer seemed very hesitant about using it in the press (he was worried about it pinching, or crimping around the top of the ski). I think it was hard to describe to him exactly how I was going to use it. I was going to put it on top of the pressing sheet not directly on the ski. I felt like that could work b/c it would keep the pressure from pinching or contorting the balnket too much. Where are you going to put the blanket in your mold?

You guys are great. Thanks for all the info.

-jordan

My heat blanket is in the bottom mold under a sheet of thin aluminum. Looking from top to bottom: Aluminum, blanket, 2 sheets of 1/8" hardboard, mdf ribs. I made sure to smooth out any edges and elminated any pressure points.

I got my blanket through: http://www.michaelsenterprises.com

They are very good to work with.

we will be pressing some skis this weekend with the new heated mold. Stay tuned!

kelvin

Normally i post at Graf, but I build skis...so needless to say I was pretty excited when i found your site. So here is a "puzzle" that i found that has been bothering me, hopefully you have the answer:

I was recently reading my new composite construction book (my christmas gift to myself) and I came across a design warning that seems to be widely used in skis and snowboards. the analogy they gave was to hang a 1000lbs weight from a chain and a bungee cord. Both the chain and bungee have a 700lbs yield. the question was how do you hang the weight and have the two work together to support the weight. You couldnt just hang them side by side and latch the weight on because the chain is stiffer and would break before the bungee "kicks in". the solution is to hang the weight from the bungee and gradually let it down until the bungee is in tension, then hook up the chain.

NOW, translate this to carbon (chain) and glass or kevlar (bungee) because carbon has a much higher modulus of elasticity than glass or kevlar, so is stiffer. so the book was stating not to layup two different stiffness fabrics parallel to each other, because one will support all the weight till failure, then drop all the weight on the other. Almost universally skis and boards use triax glass and a strip of uni carbon. The carbon is running parallel to one of the layers of the triax. Doesnt this mean that we arent letting the glass get a chance to help out? And encouraging the carbon to fail? Do we need to put all glass in tension somehow while pressing? Thoughts, comments?

Check out this thread:

http://www.skibuilders.com/phpBB2/viewtopic.php?t=188

Basically, Henrik of Hendryx skis says exactly what you mentioned. Adding CF leads to premature failure.

We don't have too much experience with carbon fiber and have only used it in our latest ski. We used a pretty heavy (13oz) uni directional CF strip on the top of our ski. We'll see how it holds up.

-Kelvin

I'm not an ME and it's been a long time since I've been in a physics class so this could all be wrong, but I'll give it a shot. The important thing in this situation, I think, is the spring coefficent of the bungee cord. If it's 100 lbs/inch [yeah imperial units] and you want to load them equally, assuming that unloaded the chain and bungee are the same length, the top of the bungee should be 5 inches above the top of the chain. If it's 500 lbs/inch, it would be one inch.

I think this should be equivalent to preloading the bungee at 500 lbs of tension. But if you vary the load, either increasing or decreasing it, you're not going to load the chain and the bungee equally. So if you pretension the bungee at 500 lbs and load the chain/bungee with 500 lbs the chain won't be loaded. And all this is assuming that the bungee/glass is a newtonian spring, which they're not but I think you can assume they are.

So assuming this is all correct, the question becomes how elastic triax glass is. [???] Now, I guess you could take a strip, hang it, weight the end, and measure how much it streches. But if the glass is un-epoxied I don't think you'd get a very acurate measurement. And if the glass were epoxied I don't think you'd be able to measure it easily, since it would be small. Though there should be some data about this some where, but I haven't seen any.

Ok, I'm over thinking this and I've confused myself, so I'm going to give up while I'm behind...

Basically this theory is absolutely correct but it it depends greatly on what you're trying to achieve with the carbon fiber.

The simplest thing is just creating breaking strength. Carbon fiber has a much higher tensile strength than E-Glass so you can reduce the amount of fiber getting a strong and ligthweigth structure. In this case you definetly have to use 100% Carbon in the respective load axis.

With using 100% Carbon you also get a stiff snappy caracteristic. The disadvantage is the high price of the structure and the dangerous behavior in case of overloading. A Carbon fiber structure brakes suddenly and unexpectedly creating very sharp waste edges (high potential of getting severly injured). The structure is than completely distroyed and unuseable. A Glass fiber structure fails softly mostly just delaminating.

If you just want to add a little stiffness at small bending angles it absolutely makes sense to add a little carbon fiber to a glass structure. It is not true that the carbon fiber takes all the load. It takes load first but as it is able to stretch the glass beginns to take a good amount of load. When it comes to failure of the structure it is true that the Carbon part fails first. But then the Glass is still able to take the forces and keeping the structure useable and preventing injury.

Here is a nice summary of mechanical properties:

http://www.skibuilders.com/phpBB2/viewtopic.php?t=144