dive knife broke trying to break glass

S

subo

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not to belittle anyone or the drama and tragedy that happenned here.

http://origin.twincities.com/ci_8966505

Your theories why a dive knife would break while trying to go thru car window.

These are some amazing brave people and if possible I would want to buy these guys some good tools (read dive knives).

Thanks.
 
Maybe it wasn't a dive knife. The article just says knife.
 
Hi,

First off, he should have had the window punch on him before entering the scene. I do Fire/Rescue/EMS, and we train for such things. A knife would have been the wrong choice of tools for the job. Knives, while interesting and useful tools in general, aren't really all that useful for such work. We have better tools than that.

Tempered automotive glass is pretty tough stuff. A knife, would most likely just poke a hole. In this situation, you need to have the whole window shatter into tiny pieces with one shot. Perhaps he poked a hole with the blade, and then tried to wiggle it back and forth to make the window shatter. Instead, the blade snapped.

If you wish to try an experiment, "stab" a car window with a sharp pointed object. Then take a $5.00 automatic center punch and press it against the glass in either of the lower corners of the window. Please wear heavy gloves if you try this.

dalee
 
Besides just because he is a "professional" doesn't mean he didn't buy a POS knife. I know quite a few LEOs that carry really flashy pieces of crap...lol. Also he may have tried prying first, who knows?
 
I have had some high end brand name dive knives when I dove and there are some things that even a good dive knife will not do. The main job for a dive knife is to cut the diver free from entanglements. Specialized tools are needed for jobs like in the article...
 
Automotive glass is pretty tough stuff; I once had to break one of my windows to get my keys out because the locksmith couldn't get it open. Took everything I could swinging a hammer into it to break it and even then it almost broke the wooden handle on the hammer.

That being said he didn't really say how the knife broke. I would think the more common sense thing would be to use the butt of the knife and not the blade. He might have just broke the handle...I wouldn't assume that the blade broke in half unless they put that. I could easily see the tip of a blade damaged though by trying to shove it through the glass.
 
"Jonas Werpy was watching the news Sunday night at his downtown apartment when his pager went off at 10:04. Within minutes, the Stillwater firefighter and diver was at the fire station and in his dive gear, including dry suit, air tanks and mask.

By 10:13 p.m., Werpy was making his first real rescue dive. He slipped into the frigid St. Croix River, looking for some way to get into the Hyundai sport utility vehicle that had plunged into the water just 10 minutes earlier. "

That means that it took only one minute for the call to be handled and nine minutes for Firefighter Werpy to get to the station, rig , travel to the incident and start a dive??
That's unbelievably quick.
 
Steven Andrews said:
"Jonas Werpy was watching the news Sunday night at his downtown apartment when his pager went off at 10:04. Within minutes, the Stillwater firefighter and diver was at the fire station and in his dive gear, including dry suit, air tanks and mask.

By 10:13 p.m., Werpy was making his first real rescue dive. He slipped into the frigid St. Croix River, looking for some way to get into the Hyundai sport utility vehicle that had plunged into the water just 10 minutes earlier. "

That means that it took only one minute for the call to be handled and nine minutes for Firefighter Werpy to get to the station, rig , travel to the incident and start a dive??
That's unbelievably quick.
Click to expand...

Hi,

The page most likely would have indicated a water rescue, (though information is only as good as dispatch gets). And I suspect he didn't suit up for a dive, but rather donned a "Gumbie" suit. This would have been done during the drive there. I don't think the car was completely submerged. Otherwise at the 10 minute mark, the rescue would have been a body recovery instead.

dalee
 
from my understanding tempered glass is supposed to basically disintegrate once there is a big enough change in the structure (i saw a demo for a glass class where the guy made a huge rain drip shape and tempered it, smashed it with a hammer on a steel table, dented the table the broke off the tinny tail and it turned to powder). but there is so much science behind tempering anything so ya moving on

i wouldnt be surprised if the thermal shock was partially responsible, less than 10 mins after the knife left a 70* building, probably not cooled down much and then plunged into near freezing water and smashed against something hard i could see how it could happen. i kind of expect the knife would have a flaw or be a junk knife to start though

-matt
 
Most dive knives are not made of good knive steel
They are not even heat treated. They are corrosion resistant rather the heat treated. (Thats why I make my own dive knives)
Pick up a dive knive in a scuba store and all it will most likely say is stainless steel.
I believe there is also a differance between the windshield of a car at side windows. The side windows will shatter compleatly while the windshield has layer(s) of plastic (polycarbonate i think) .The windshield you would have to cut through ,while the side windows will shatter if hit with a punch( center punch) or even the tip of a knife .
 
It is very difficult to break toughened vehicle glass unless you use a proper spring-loaded glass punch.
I have thrown a pair of pliers as hard as I could at a car's side window, only to have then bounce back at me. I have also had a GPMG butt bounce off - I had to turn the gun around and ram the barrel through the window.
 
I'm wondering if he had a folder and that the hinge might have broken when "stabing" the blade into the window, especially if he had a slight angle on it.
 
SR_Matt,

I believe the glass drop in the demo is called "Prince Rupert's Drops". Hot glass is dripped into warm water. The drops that survive the water quench have a lot of internal stress in them because of the rapid cooling. If looked at under polarized light, it will show a lot of stress marks. When the tail is broken off, it releases all the stresses in the drop and it shatters into dust.

I made some in high school. Take some glass tubing (run of the mill soda lime glass) heat it with a bunsen burner and let the drops fall into some water. I found that if the water was about ~20 C (~ 68F) it worked better. make sure you wear eye protection.

I believe that auto glass is laminated. Look at a car window with polarized sun glasses. You can usually see some sort of regular pattern. I think this is from the adhesive or bonding process.

Ric
 
Phydeaux, yep thats the name i couldnt remember exactly but i knew there was a prince and a drop in there

-matt
 
Just to clear things up. I was the diver. The knife was a standard dive knife and was not a specific rescue tool as would be normally used on a vehicle accident on land. It is hard to mound a window punch on a BC. They are either too big or too small . If it is too big, it is in the way for the majority of your dives. if it is too small, such as what people are describing here, the spring-loaded type, it becomes too small to even handle with gloves on or in this situation, hand motor skills become limited due to the cold. It was a 3" fixed blade with clip-in sheath. It stated "stainless steel" on the blade. I don't have this knife anymore. It is at the bottom of the river. We are currently searching for an adequate knife to replace it and the others on our dive equipment.

The problem here, and what i've noticed while shopping for replacements, is that dive knives are flimsy. I always suspected this and requested a window punch while en route to the call in case the knife did fail to break the glass. I am looking for stronger, non-flexing knives. These would probably work fine but redundant is always good. There will always be a back-up option readily available.

Other factual inaccuracies on peoples posts I wanted to clear-up:

1. It was a fully submerged vehicle, not partially as suspected by one poster.
2. It came as a dive call and I was in a dive dry-suit.
3. The timing being reported is accurate to the best of my knowledge. We are a rapid-response team and train for this. I can be on air and water ready in less than two minutes. There is nothing we can do about drive time to a call.
4. There are only a few documented calls like this in the world. Drownings happen fast.

Hope this helps.
Jonas
 
im glad we were able to hear from you, that clears a lot of things up and hopefully you can get better guidance on what to look for to carry for your team.

thank you for posting and thank you for your service
-matt
 
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