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Question on the strength of kydex

Posted: Thu Jul 14, 2011 8:47 pm
by Sigismund von Helfenstein
Working on my new splinted limbs, and just about the only part I haven't made are the splints. I want to use plastic for the splints, and I have a sheet of 1/8" thick textured kydex. I have not worked with kydex much before so I want to make sure, before I finish my construction, that the splints will be hardy enough to last.

My concern is for how strong the splints will be if they are roughly 1 1/2" to 2" wide by at least 6" or more long, with two to three 3/16" holes drilled along the center line for the rivets. I'm not sure how resilient kydex is, so could anyone with some experience tell me if these splints seem feasible?

I've been cutting pieces and flexing, bending and hitting them, and it seems like these splints will work, so I just ask to see if there is some aspect I have overlooked.

Re: Question on the strength of kydex

Posted: Fri Jul 15, 2011 7:01 am
by Sean Powell
They should work rather well. Not indestructible but well. My fabric covered kydex vambraces lasted me 8 years of irregular practice and died because of cracking where the rivets for the hinge placed odd stresses on the plastic during impact. So long as you land the edged and don't make a hole by hammering through it with a philiphs head screwdriver there shouldn't be any cracks to cause a stress concentration.

If you can put a curve into them by say, heating in an even and draping over a wine bottle, the shape will give you a lot of stiffness that the material thickness doesn't.

Luck!
Sean

Re: Question on the strength of kydex

Posted: Fri Jul 15, 2011 8:52 am
by Sir Wilhelm
I have woven leather vambraces with kydex riveted into the weave. They work fantastic and show no signs of wear.

Re: Question on the strength of kydex

Posted: Fri Jul 15, 2011 9:10 am
by Adric13
I made kydex shield bosses 15 years ago and still have several going strong even when I was fighting 2 practices a week. It's pretty tough stuff.

Re: Question on the strength of kydex

Posted: Fri Jul 15, 2011 9:55 am
by Konstantin the Red
And in San Antone, it probably doesn't get cold enough to embrittle them. At least not often. Very cold weather can make Kydex more liable to crack, but in your application the problem may never come up at all.

Re: Question on the strength of kydex

Posted: Fri Jul 15, 2011 10:16 am
by Sigismund von Helfenstein
Konstantin the Red wrote:And in San Antone, it probably doesn't get cold enough to embrittle them. At least not often. Very cold weather can make Kydex more liable to crack, but in your application the problem may never come up at all.


In San Antone it doesn't get cold, as far as I can tell. :lol:

Re: Question on the strength of kydex

Posted: Fri Jul 15, 2011 10:25 am
by Sigismund von Helfenstein
Sean Powell wrote:They should work rather well. Not indestructible but well. My fabric covered kydex vambraces lasted me 8 years of irregular practice and died because of cracking where the rivets for the hinge placed odd stresses on the plastic during impact. So long as you land the edged and don't make a hole by hammering through it with a philiphs head screwdriver there shouldn't be any cracks to cause a stress concentration.

If you can put a curve into them by say, heating in an even and draping over a wine bottle, the shape will give you a lot of stiffness that the material thickness doesn't.

Luck!
Sean


Great idea, Sean! I was concerned that the 1/8" inch thickness would not be enough, and should perhaps go with 1/4", but putting in a slight curve should solve that problem nicely!

Re: Question on the strength of kydex

Posted: Fri Jul 15, 2011 11:22 am
by raito
Sigismund von Helfenstein wrote:In San Antone it doesn't get cold, as far as I can tell. :lol:


They have a different scale in TX. As near as I can tell, anything under 90F is chilly.

Re: Question on the strength of kydex

Posted: Sat Jul 16, 2011 10:25 pm
by Sigismund von Helfenstein
Bumping.

Kydex experts speak now, or forever hold your peace.

Re: Question on the strength of kydex

Posted: Sun Jul 17, 2011 3:40 am
by St. George
Kydex will work well and be safe as splints depending on how you shape the, Cracking in the cold shouldn't be a problem because your body will warm them up fast.

Consider puttingany padding behind them, either mouse pad or closed cell and this will be about as good of a style of protection as you can get in the SCA.

g-

Re: Question on the strength of kydex

Posted: Sun Jul 17, 2011 4:01 am
by Rayner
raito wrote:
Sigismund von Helfenstein wrote:In San Antone it doesn't get cold, as far as I can tell. :lol:


They have a different scale in TX. As near as I can tell, anything under 90F is chilly.



Hey us Texans are more cold tolerant than that! It doesn't start to get chilly till at least 87 thank you very much. 90 is just plain comfortable.

Re: Question on the strength of kydex

Posted: Sun Jul 17, 2011 10:53 am
by Sigismund von Helfenstein
Anyone have any ideas as to how I could shape the greave splints to form to my calves?

Re: Question on the strength of kydex

Posted: Sun Jul 17, 2011 6:56 pm
by leekellerking
If I may intrude into the thread, what thickness of Kydex should I be looking at for vambrace and kidney pad bracing?

Lord Leif
Stargate, Ansteorra

Re: Question on the strength of kydex

Posted: Sun Jul 17, 2011 7:31 pm
by Sean Powell
Sigismund von Helfenstein wrote:Anyone have any ideas as to how I could shape the greave splints to form to my calves?


I would recommend heating the splints at 250F and then draping over a cylinder of approximately the right diameter. I made my plastic leg armor in school by shaping over a fire extinguisher.

leekellerking wrote:If I may intrude into the thread, what thickness of Kydex should I be looking at for vambrace and kidney pad bracing?

Lord Leif
Stargate, Ansteorra


1/8" is sufficient for vambraces. 1/8" is legal for kidney protection but I've never worn it in that way. My corazinna is 1/8" kydex, has held up quite well over the year and provides plenty of protection.

Luck!
Sean

Re: Question on the strength of kydex

Posted: Sun Jul 17, 2011 9:09 pm
by Cunian
Shape the kydex to your leg first and cut it into splints after. It's easier to get a consistent, appropriate curve that way.

Re: Question on the strength of kydex

Posted: Sun Jul 17, 2011 9:38 pm
by Baron Alejandro
Sigismund von Helfenstein wrote:Anyone have any ideas as to how I could shape the greave splints to form to my calves?


How perfect do you want it to be? You could make a plaster of your calves pretty easily & cheaply, and form the plastic around *that*. Or, if lazy and stupid, you can put a towel over your calf, heat up the plastic, and get a buddy with another towel to press it onto your leg for as long as you can stand it. Run it under cold water to 'freeze' it into shape once it's come down in temp some.

Re: Question on the strength of kydex

Posted: Sun Jul 17, 2011 9:43 pm
by Sigismund von Helfenstein
Baron Alejandro wrote:
Sigismund von Helfenstein wrote:Anyone have any ideas as to how I could shape the greave splints to form to my calves?


How perfect do you want it to be? You could make a plaster of your calves pretty easily & cheaply, and form the plastic around *that*. Or, if lazy and stupid, you can put a towel over your calf, heat up the plastic, and get a buddy with another towel to press it onto your leg for as long as you can stand it. Run it under cold water to 'freeze' it into shape once it's come down in temp some.


Being both lazy and a bit stupid, I think I will attempt this ironman approach of holding the hot plastic to my betoweled leg. I'll let you know how it turns out.

Re: Question on the strength of kydex

Posted: Sun Jul 17, 2011 10:03 pm
by Konstantin the Red
Do not wet that towel. Use it dry, or else get scalded with steam. 2 layers toweling will be better than 1 and will aid in setting up for padding within splints. {ETA} Secure the towel firmly by any workable means. This is something you don't want slipping!

Re: Question on the strength of kydex

Posted: Mon Jul 18, 2011 8:28 am
by Baron Alejandro
You're going to have to heat the plastic in your oven until it just barely starts to droop. (Don't tell your Lady you just outgassed petrochemicals in her oven) When you press the hot plastic on, try not to squeal (I failed at that). For fine tuning, get a heat gun.

Re: Question on the strength of kydex

Posted: Mon Jul 18, 2011 8:28 am
by Baron Alejandro
Also, what Konstantin said. Unless you are going for that lobster look.

Re: Question on the strength of kydex

Posted: Mon Jul 18, 2011 11:48 am
by Baron Alejandro
Also, if anyone uses this advice to make exposed plastic armour, I will dump goat vomit in your armour bag. Don't think I won't.

Re: Question on the strength of kydex

Posted: Mon Jul 18, 2011 12:02 pm
by Sigismund von Helfenstein
Baron Alejandro wrote:Also, if anyone uses this advice to make exposed plastic armour, I will dump goat vomit in your armour bag. Don't think I won't.


Perish the thought.

Re: Question on the strength of kydex

Posted: Mon Jul 18, 2011 12:38 pm
by Konstantin the Red
Do pet goats have a gag reflex?

Re: Question on the strength of kydex

Posted: Mon Jul 18, 2011 1:20 pm
by Sean Powell
Baron Alejandro wrote:Run it under cold water to 'freeze' it into shape once it's come down in temp some.


The only catastropic failures of kydex I have seen have been with plastic that was 'shocked' by quenching in water. I would suggest against it.

Sean

Re: Question on the strength of kydex

Posted: Mon Jul 18, 2011 8:19 pm
by Baron Alejandro
I don't mean stick it in a cold bucket of water; i mean turn your faucet on and run it under that. Brings the temp down less precipitously. YMMV, ad goat nauseaum, etc.

Re: Question on the strength of kydex

Posted: Mon Jul 18, 2011 8:27 pm
by Payn
Konstantin the Red wrote:Do pet goats have a gag reflex?
not with "training"