I think this would be a fun craft project, and have been playing around with it for quite some time. Also, my current boots, which were full custom, but don't fit because I went to the wrong fitter, are somewhat uncomfortable, and have broken down. My other ones were too large, but I custom fit them to my feet by cutting foam to shape. They are too heavy.
I'm well aware it will take a lot of time, experimentation and effort, and that failure is probable.
I think the "right" way to make figure skating boots is to build them around the skater's feet. That way they will fit perfectly, and you can make them bend the exact way the feet bend, limiting the bend to what is safe and comfortable.
Current skate manufacturing techniques present several problems with that approach. Don Klingbeil, when the Klingbeil figure skate boot company was still in business, told me that they used heat, moisture (in the form of steam) and pressure to mold leather boots to the lasts. (A last is the mold around which the boot is formed.) The temperature required is too high for contact with the foot, and according to another custom boot maker (who makes walking and riding boots) the pressure required to bend leather thick and stiff enough for boots is much too great to be safe to use your feet. (However, softer custom shoes are often made that way.)
Some light weight skate boots are instead made by molding marine/aerospace composite materials around lasts to which a release agent has been applied, much like ultralight boats and ultralight aircraft. The release agent prevents the boot (or boat or aircraft) from sticking too hard to the last or mold. You don't need extreme temperatures or pressure to use this approach. Based on an old boat-building manual by Charlie Walbridge, they presumably combine cloth made of fiberglass, carbon fiber, (e.g., graphite fiber?), S-glass and/or kelvar, with liquid plastic resins (maybe two part epoxy resin, or polyester, or vinyl ester?), possibly with a light weight foam core. Before the resin has hardened, they might vacuum off of the excess resin - which is also done on the most expensive ultralight boats and ultralight aircraft, to save weight.
Problem is, all of those marine/aerospace resins are highly toxic and carcinogenic, before they are fully hardened. You don't want those resins in contact with your feet! I'm not even all that sure they are altogether safe for prolongued skin contact AFTER they have hardened. Even if you could find a non-toxic resin, if the release agent (like grease?) didn't work quite right, the resin would bond to the feet - very, very bad.
I've been playing around with lower tech construction techniques by wrapping tape around removable socks (to function as a washable liner, perhaps held in place using Velcro). I place sports wrap between the sock and tape to function like a release agent - though I have also played with wrapping the inner tape layer sticky side out. I use a a tape wrapping technique similar to what is used to what athletic trainers use to re-enforce ankles. I may stiffen the final boot using ultralight marine/aerospace composite materials for the outer layers.
I plan to drill the lace holes.
If you think about the intuitive physics, the bottom part of the sides of the boot need to be stiffest and strongest. That's because the sides of the boot act like a lever - the force is greatest there. If the boot was perfectly stiff at the base, the force would be infinite at the fulcrum - so it can't be. But in practice, a lot of the side stiffening needs to extend from the toe box and the heel counter, somewhat like arched buildings, because the foot goes in the middle. Some extra stiffness all around is required at ankle bone level to achieve that extension.
The outer sole needs to be very stiff, so it doesn't bend, and the screws or bolts for the blades stay in place. Also, perhaps it is needed to help spread out the weight support from the runners - though maybe the blade base plates are enough. In commercial skates, the outer sole is either made from plastic, or from adhesive-hardened leather. (Originally, pine pitch was used to harden Medieval and Renaissance leather, but I think more modern artificial adhesives are more typical now - though Don Klingbeil claimed his boots were all-natural, so I'm not sure.)
Another approach would be to tape the material of the sole to the base plate of the blades. Since that wouldn't let me move them after it was done, I might figure out where the blades go by balancing myself in the preliminary boots on a pencil. I'm also not sure if blade base plates are stiff and strong enough if the outer sole isn't very stiff.
So far, the hardest part is making the tongue - I have to be able to take the boots off, so a very long tongue is critical. (I had to cut off an initial attempt made from duct tape, in retrospect a really stupid mistake.
) I create this by sticking tape to itself for the inner layer, and wrapping more tape around it. On commercial boots, the tongue does not attach to the sides of the boot. But I think I want to make it do so, so a continuous tape wrap around the boot is possible. The idea is to fold the outer part under itself, so the tongue can be lifted to release the foot.
I haven't gotten very far - I'm not an engineer, nor have I any boot making experience, and don't really know what I am doing.
I am staying with duct tape for the initial attempts, because it's cheap, but will probably transition to athletic tape, because it holds its shape better.
Anyone have other ideas that might help?
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To give you some idea of what other skaters have gone through, to get good fitting custom skates made (the rest of this is from memory - some details may be wrong):
I corresponded with a lady who had had custom boots made by each of the major custom figure skate boot makers. None had fit. Each of those boot makers had a money-back guarantee, and she had demanded and received her money back.
She had used the same local fitter for all of them, not one of the world's best known fitters, nor did she travel to a fitter at the factory. I wonder if that was the problem...
She then went to one of the world's leading podiatrists, to get 3D feet scans made. The podiatrist then adjusted the scanned shape to make her feet healthier (or more comfortable?), apparently a very important step - she was told not to just take the natural shape of the feet. (But in my case, I don't have any medical issues with natural foot shape - I don't hurt walking bare foot, nor do my feet collapse asymmetrically.)
She then sent those scans to the world's leading custom last maker, who had previously collaborated with that podiatrist. There were only one or two such people in the world. He made her custom lasts - though, apparently, he didn't have the tools or experience to make them as high as a figure skating boot, but he did what he could.
This is highly atypical. Most custom boot makers take their stock lasts, and add putty or other material to approximately fit the measured shape of the feet.
(If I understood her correctly, she was told that many of the best boot lasts are made with hinges, perhaps to make it easier for the boot maker can pull the last out of the boot after the boot is made. Presumably, it also lets the boot maker adapt the boot to the way the foot actually bends. A good podiatrist can measure the places and extents of safe bend that your foot can take, though I don't know if she had this done. Thus, you can't just scan your feet, guess how to adjust the shape, and use a CNC router to make your lasts.)
She then took those lasts to a local boot maker (not the one the podiatrist and last maker had worked with before and had strongly recommended), who molded custom boots around them.
That should have created a perfect fit, and made her very happy, though it was a very expensive route to go.
Alas, that boot maker had not made figure skates before, and didn't understand what was needed. The resulting boots were not stiff enough to skate in.
Perhaps she could have sent the lasts instead to a custom figure skate boot maker. But perhaps she felt she had already burned her bridges with them by demanding a refund. However, she was considering trying that route with one of them anyway. I don't know if she finally did that.
That's all a very cool, but very expensive way to go. It also doesn't work well for a do-it-yourselfer who doesn't have the appropriate 3D scanning equipment, CNC equipment, and leather boot molding tools.
Last I knew, she had taken boots that were more than large enough to fit her feet, and had cut herself foam inserts, below and around her feet, to make her feet fit. That's more or less what I have done in my misfit boots. That can create a perfect fit which is completely comfortable. However, it results in boots that are bigger and therefore heavier and bulkier than is needed.