Oven molding boot shells

[Brian Finch]

It appears many ‘19 boots are now “Heat Moldable” & even some carry over models now claim to be as well.

Would someone educated talk me through this process?

 

[Mike Thomas]

Each manufacturer is different, but there is one common thing- Don't use the broiler.

(you're welcome)

 

[Monster]

I've heat molded quite a few boots - with a heat gun and hydraulics. . .

Seriously though, they fit hockey skates with heat and vacuum all the time and it seems to work. I've never heard anything good about that process in ski boots and have witnessed miserable failure from the Fischer version. Lousy plastic, limited shape change, ultimately poor performance, and a waste of $ IMHO. Someone's going to figure it out sooner or later but later seems more likely than sooner to me.

 

[jmills115]

It appears many ‘19 boots are now “Heat Moldable” & even some carry over models now claim to be as well.

Would someone educated talk me through this process?

Educated......ehhhh. Willing to stuff my foot into a shell that’s been in the oven at 215 for 12-14 minutes, sure. I tried it for some additional room after seeing a fitter.
I read a thread on another site where hot water was used for the shell and an oven for the liner. Not having a pot big enough I used the oven for both.
A ski sock with adhesive backed foam was used to build up over hot spots, a toe cap (wool sock cut a few inches up) followed by a wool sock. This “should” increase your shoe size by +1 (I needed) with additional space where the foam is used.
I used a tile in the oven preheated to 215 so the shell or liner wasn’t touching the metal rack, cooked the shell for 12-13 and the liner for 8-9, removed, stuffed in liner, foot, lightly buckled, and put the toe on a 2x2 for 12 more minutes followed by cooling in snow.
The liner did mold to the shell and think I got some additional space where the foam was built up.

Guess which ugly foot got the heat

 

[Brian Finch]

^ This makes the site great.

 

[neonorchid]

How much time do you have?

 

[Primoz]

Seriously though, they fit hockey skates with heat and vacuum all the time and it seems to work. I've never heard anything good about that process in ski boots and have witnessed miserable failure from the Fischer version

I always fit my ice hockey and inline speed skates, as well as ski boot liners in my home oven. But with this, you are actually heating foam inside of skate (similar to liner of ski boot), not shell of skate. For boot's shell, I somehow doubt you would get some decent result doing it same way. I agree boots are different, but race boots that I fit for myself require plastic to be heated up to around 150c (for skates and liners it's normally more around 70-80c), and then pressed and cooled off. Exactly what you said, with heat gun and hydraulics (or similar). You certainly don't want all plastic of the boot to be heated this much, as it will loose all stiffness. But I believe there might be some low level boot where ultimate stiffness is not required and losing some of it, won't be priority, so they would be able to survive heating them up this high.

 

[Monster]

I have a friend who's a former US women's hockey team member. She once described to me in detail how they fit skates at that level. It involves heating the entire skate and putting it in a vacuum rig so molding the shell to the foot, not just the liner, though that too in the process. I imagine that's where Fischer got their idea for their vacuum boots. Seems like a reasonable idea for ski boots - too bad it doesn't work yet. The lateral demands on ski boots are just too great to use plastic malleable enough to mold like that. Plus, on a skate, the edge is right under the center line of the foot and you can balance on it when you angulate. For skis, the wider the ski, the farther the edge is laterally from the center line of the foot, the more mechanical advantage forces generated there have on the boot. Much greater demands on the system overall, I think.

As an aside, the Zipfit guy recommends heating shells in a rice cooker (!), then putting the liners into the hot shells and letting the heat from the shells be what warms the liner, rather than heating the liners and putting them into a cool shell. Interesting. I use heat moldables - never met a stock liner I liked - prefer Black Diamond, and heat them in a conventional oven. Works great as long as the shells are the right shape. The punches have to be precise and match the fill volume of the chosen liner. IMHO, no moldable liner will compensate for a shell that's just the wrong shape.

 

[Monster]

How much time do you have?

At home, it takes me usually 3 or 4 hours total to bring a pair of boots to final fit from off-the-shelf. Including a few test skis and tweaks (not counting the time skiing).

 

[Swiss Toni]

All injection molded thermoplastic ski boot shells can be molded to the shape of a skiers feet by heating them up in an oven. The method used depends on the softening temperature of plastic used to make the shells. If the shells are made from a traditional plastic such as polyether polyurethane, which has a softening temperature above that which will burn the foot wooden lasts customized to the shape of the skiers feet can be used.

The shells are heated to the required temperature in an oven and the lasts are inserted into the hot shells which are then allowed to cool.

If the shells are made from one of the newer low softening temperature plastics such as Salomon’s Kaprolene (a blend of polyester polyurethane and polycaprolactone, polycaprolactone is also used to make heat moldable footbeds) or Fischer’s Vacu-Plast (a blend of nylon 6 and an ethylene acrylic acid / methacrylic acid copolymer resin) the boots can be molded directly to the skiers feet.

Salomon and Fischer will more than likely have had exclusive supply deals with the plastics manufactures, which might have expired. If this is the case other manufactures will now be able use these plastics. As the Salomon plastic is a polyurethane blend it is most likely to be the plastic being used by Head and Dalbello / K2 in their custom shell boots, as it’s use wouldn’t require any changes to the molds. Nylon is much less viscous than polyurethane so the runners and gates in the molds would probably have to be modified if the Fischer plastic was being used.

 

[DanoT]

Ski shops that sell Head "Form Fit" boots have a special oven that produces the correct temperature. With the footbed removed, the liner is put in the shell and heated for I think 12 minutes. The footbed is then inserted in the boot and the customer wears the boot for about 15min. in the shop.

 

[Monster]

"If the shells are made from one of the newer low softening temperature plastics such as Salomon’s Kaprolene (a blend of polyester polyurethane and polycaprolactone, polycaprolactone is also used to make heat moldable footbeds) or Fischer’s Vacu-Plast (a blend of nylon 6 and an ethylene acrylic acid / methacrylic acid copolymer resin) the boots can be molded directly to the skiers feet."

In my experience, those things aren't worth the time and expense to fit - lousy on-hill performance.

 

[James]

How much time do you have?

]

I followed that 300deg F recommendation in punching a Lange Plug last year. Had a bootfitter laugh, but when pressed on what temp he used got no answer. His punches had a habit of not holding too, and would tell people that putting boots in say an 85 deg furnace room to dry was responsible for the punch not holding. Really annoying but par for that course.

 

[Dakine]

IMO...any plastic that is thermoformable at temperatures below 250F doesn't have the guts to hold up in a ski boot application.

 

[Doug Briggs]

I've had two (really three, more later) heat molded boots.

The first was the Fischer Vacuum RC4 Pro 130. It fit well before the molding but was pretty uncomfortable. After being heated and vacuumed (actually pressure applied, not vacuum at all) they fit great. I only heated the shell; the liners were warm enough from the hot shell to conform during the process. I experienced the unfortunately typical cracking of the shell just aft of the second (from toe) buckle and got another pair under warranty. Same story, different pair. I used a hot nail to stop the crack and have raced and skied in the boot for 2 seasons now without further cracking or performance degradation. The boots were cooked in the Fischer oven and vacuumed in the shop I work at. Fischer has since upgraded their plastic and stopped vacuuming some of the higher end models. They seem to have fixed the plastic problem.

The second (or is it third) pair were my Atomic Hawx XTD 130s. They fit well for a while without molding then I developed a hot spot on my heel spurs. I had them cooked along with the liners at the shop and since I was only looking for increased volume we didn't do the vacuum part. The boots fit better than the Fischers which is incredible given that the Fischers fit perfectly.

We have lots of people bring their non-Fischer, non-shop sold boots to us to have them cooked and fit. We use the manufacturer supplied ovens and I don't know what the temps or times are. They do vary from manufacturer to manufacturer.

Caveat emptor: you can only gain volume if you cook and don't have the machine to press the boot onto your foot. The only machine that I know of for doing that is the Fischer system. I could be wrong, but I think it is patented so it might be a while before you see other companies offering the process.

I highly recommend getting your boots cooked. Despite the problems Fischer has had with plastic cracking, I believe that their product is exceptional. Nota bene: I do work at a Fischer dealership. I don't have first hand experience other than that presented here as I'm a ski mech not a boot fitter, but I think cooking any boot that can take it is a good idea.

 

[Doug Briggs]

A point that might be overlooked cooking your first shell. Wear gloves when handling the boot out of the oven. It may seem obvious but in the excitement of doing it, you might forget. Put the gloves on the handle to the oven so you won't forget. It would be tragic to cook your boots, pull them out touching anything metal on them and then have to do first aid instead of fitting.

 

[Primoz]

I have a friend who's a former US women's hockey team member. She once described to me in detail how they fit skates at that level. It involves heating the entire skate and putting it in a vacuum rig so molding the shell to the foot, not just the liner, though that too in the process

For this you need skates to be made from carbon that is meant to be used this way. I know my Powerslide Core Icon boots for inline speed skates are suppose to be made of such carbon (it's actually not carbon fibers itself, but epoxy/glue or whatever is proper word for thing that holds everything together), and you can actually mold outer shell of speed skate. But for ice skates I never heard they would be done this way. And normally ice skates have much thicker "liner" then speed skates that are basically just carbon fiber straight to foot, so there's less need for reshaping outer shell. But I also believe top players have different skates then "top skates in stores" are, just the same way as WC race skis are different then "race skis from store".

the shells are made from one of the newer low softening temperature plastics such as Salomon’s Kaprolene (a blend of polyester polyurethane and polycaprolactone, polycaprolactone is also used to make heat moldable footbeds) or Fischer’s Vacu-Plast (a blend of nylon 6 and an ethylene acrylic acid / methacrylic acid copolymer resin) the boots can be molded directly to the skiers feet.

It's true but it's also true, changes in plastic after heating/molding are bigger then someone would want to admit. That's one of reason all Fischer guys in WC are still on normal, non-vacuum boots Boots just get way softer after being heated, which basically renders them unusable for real racing.

 

[jmills115]

I didn’t mention I forgot to pull the superfeet carbon insole out of the liner on the first boot I did. It curled a bit on the toe and will be in the trash before next season.

 

[Swiss Toni]

Ski shops that sell Head "Form Fit" boots have a special oven that produces the correct temperature.

Ski boot ovens have been around since the 1990s, I think they were introduced by Raichle for heating their Thermoflex liners.

As you can see heating element and fan are the same as those used in many domestic ovens. The temperature is pre-set depending on application. They are all made by the same German company https://www.myformbase.com/en/specifications.html

I thought that these boots were mainly aimed at recreational skiers who ski for maybe 1-2 weeks a year, I can’t see why keen a skier or racer would be interested in them. In my opinion there is still no substitute for polyether polyurethane. As far as racing is concerned I thought the main reasons polyurethane ispreferred was because of vibration damping and rebound, polyurethane is much better at dampening vibrations and rebounds better than any of the other materials currently used.

The Fischer plastic is made by DuPont, I don’t think they have any previous experience of making ski boot plastics and Fischer themselves have only been in the ski boot business for a relatively short time, manufacturing is contracted out and a lot of the design work has been carried externally so I think there is still some way to go before their boots could be considered as being on par with the boots from the more established players.

 

[Dakine]

If anyone wants to get lost in the mechanical properties of engineering thermoplastics, this is a good place to do it.
https://www.curbellplastics.com/Research-Solutions/Plastic-Properties