Sal - a ? about FRN models

4 s ter

4 s ter

Joined
Apr 22, 2001
Messages
1,068
Sal

A member of this Forum has repeatedly warned us about the possibility of "catastophic" failure of the FRN handles on a number of models if put to "hard use" The suggestion is that models such as the FRN Matriarchs, Enduras, etc. can't be trusted under hard use and our fingers are at risk.

I have yet to see a Spyderco response to these comments and warnings. Could we have your response to the issue? I personally have a number of these models and have never seen any indication of a problem but I would like to get your side of the discussion.

Thanks!!!

p.s. It's great to see you able to free up some time to participate in this and the Spyderco site Forum again!!
 
Hi 4 s ter. I can offer my opinions on locks and catastrophic failure, but they are my own opinions. There is much disagreement on locks and "hard use".

We shall define "Catastrophic failure" as when the lock suddenly fails and creates the situation where the blade can close on the users fingers.

"Hard use" we shall change to "Spyderco's Heavy duty use", which we use 100 inch lbs of lock strength per inch of blade length measured from the leading end of the handle to the tip of the blade. For example if a knife has a 3" blade X 100 inch/lbs, the lock would have to hold 150 inch/lbs of direct force.

Catastrophic failure occurs:

1. often as a result of dirt or lint or other unwanted material lodged inside the locking mechanism and preventing it from holding properly.

2. a lock that has not been properly engineered or built and simply slips.

3. a part breaking under force.

The question then becomes is FRN capable of holding enough force to keep from breaking under our own "Heavy duty use" standard?

With our FRN handles (using the brand that we use with the amount of glass that we control), yes. Our Enduras and Delicas usually break at about 80-90 inch/lbs per inch. These would be in the very high "Medium Duty use" range (50 - 100). That's about where we like to see it. We're working on some new materials to make pins out of that will hold higher force and still be workable, because it is more often than not, the pins that give out first. I think that a well made FRN handle with no metal liners is capable of holding sufficient force to take "Heavy duty use" at the bottom end of the scale.

This is not to say that it is as strong as if made with a metal liner like steel.

G-10 has demonstrated very high resistance to breakage and our G-10 is specially maded to take even higther than normal loads.

hope that helps

sal
 
Sal,

Have the stainless handle models been shown to be stronger (load-bearing) than the FRN models? For example...Is the stainless Delica stronger than the FRN Delica?
 
Thanks for the info Sal.

Personally I find the anti-FRN (Zytel) hysteria by some as a bit silly and more due to snobbery (people who need the best of the best), or naivety (people with too high of expectations). The way some people talk you'd think FRN will melt if you leave it in the sun!

Zytel certainly is not in the league with G-10 or CF, but this stuff is what the wheels of my BMX bicycle was made of when I was a kid so I know it's pretty tough stuff.

It all boils to common sense: DON'T PUSH THE KNIFE PAST ITS LIMITS. What's pushing a FRN (or most folders) past it's limit? Doing silly things with it like: using it in place of a prybar, using it as chisel, a screwdriver, using it as throwing knife, stabbing plywood or other hard objects (even frozen fish or steaks), or other horseplay. I admit, I've done some of these. :o

That's not what FRN or even most folders are designed for. As they said in shop class in highschool, use the proper tool for the proper job or you're going to have an accident.

I say, if you need something heavy duty, get a good fixed blade, or pay that little more for a G-10. But don't totally write Zytel off as sh*t because you were foolish enough to subject it to -- what is in essence -- unreasonable use and it failed on you.

Yes, FRN is a compromise but for most common cutting tasks (cutting string, boxes, rope, whittling, cutting bagels) it's sufficient. I own various G-10, titanium, and SS handled knives but I use a FRN Native for an EDC and it works fine.

Don't get me wrong. All other things equal (like price) I'd pick a G-10 knife over an FRN simply because G-10 is more high-tech, more sought after, and that much better. However, I don't write off FRN as a bad material for knives. After all, FRN gave price conscious knife nuts like me an opportunity to own an affordable CPM 440V blade -- The Native Lightweight.
 
Thanks Sal!!

I recognize that it is your "opinion" but your opinion is based on extensive testing and research, something I value and feel I can count on.

The chances of me exerting the forces mentioned ON THE SPINE OF THE BLADE (which would be required to caused failure which would injure my fingers) is very unlikely.
 
Originally posted by Sal Glesser
"Hard use" we shall change to "Spyderco's Heavy duty use", which we use 100 inch lbs of lock strength per inch of blade length measured from the leading end of the handle to the tip of the blade. For example if a knife has a 3" blade X 100 inch/lbs, the lock would have to hold 150 inch/lbs of direct force.
Click to expand...
Sal, can you explain this a bit further. I'm not quite understanding it.
Are you guys putting pounds of force about an inch away from the pivot point?
 
Sal,

The opening post here may or may not refer to my posts, but I have posted such sentiments on FRP, particularly nylon matrix, materials. A bit on my background qualifications, I did my undergraduate work in chemistry from the University of Wisconsin and went on to Stanford where I did my graduate studies in physical polymer chemistry. I held a number of positions in the aerospace industry doing materials science research and development.

During my last years in that industry, I had several assignments dealing with the failure analysis of FRP materials which had failed catastrophically in applications where the design indicated they would last many times longer. Upon doing an extensive literature search and corresponding on many occasions with DuPont personnel, a picture emerged of a very unpredicatable material. To make the problem worse, the mechanical properties originally generated and the performance exhibited with a newly-made component (in our discussion let's say a knife handle) may degrade tremendously over a few years use.

I won't get into additional details, but I would NEVER recommend FRP for structural applications. Now, of course, if a good liner material is used with the FRP in a knife handle application, there should be no problem. With no liners, the situation is quite different.

In an emergency situation where non-ideal and significantly out-of-plane loads are involved, all bets are also off. The modulus of FRP is not outstanding and deflection and distortion under load occurs to a far greater extent in FRP than in G10, carbon fiber/epoxy, steel, titanium or even an aluminum handle. I would expect some strange and premature failure modes to be observed under non-ideal loading. (I recall a significant number of such problems occurring in an earlier go-around on this topic).

So that's my opinion for what it's worth. Certainly everyone here is free to purchase whatever knife made with whatever materials and of whatever design they choose. I, for one, will continue to avoid unlined FRP-handled folding knives.
 
Thanks Blade Santa Cruz for the chem lesson. It adds to my "bladeucation".

I appreciate you have qualified your answer as to why you don't like FRN (FRP, Zytel, whatever). Also, it is certainly up to individual taste as to what they choose to buy. Lastly, the demands you require from your knife may very well differ from my own requirements. Still, based on my own personal experience with Zytel (in knives, on BMX wheels as a kid) I believe within limitations, FRN is a viable material for folders. Moreover, it keeps the cost down so that the cost savings could be deferred to, say, better blade material. It's a compromise.

About the deterioration of FRN: I have always wondered about this since I keep all my knives lubed with petroleum based oils. I know that many synthetics -- particularly plastics -- chemically react with a petroleum base and can deteriorate rendering them brittle over time. Has there been studies to research the estimated life of FRN?

This isn't a huge concern as I always say: I don't need a knife that will last me a lifetime. Just long enough to satisfy me until the next cool knife comes along.
 
Blade Santa Cruz

Yes, my original post was in reaction to your previous comments. I am pleased to see the discussion taking place. I am also pleased to see that you certainly are stating opinions based on research and testing.

My post was not an attempt to prove you wrong. The purpose of my question to Sal was to see Spyderco's reaction to the warnings which you have given. Seeing both sides of the discussion helps me make informed choices.

Thanks for your response!!

p.s. my EDC is a g-10 Native
 
Originally posted by Blade Santa Cruz
Sal,

The opening post here may or may not refer to my posts, but I have posted such sentiments on FRP, particularly nylon matrix, materials. A bit on my background qualifications, I did my undergraduate work in chemistry from the University of Wisconsin and went on to Stanford where I did my graduate studies in physical polymer chemistry. I held a number of positions in the aerospace industry doing materials science research and development.

During my last years in that industry, I had several assignments dealing with the failure analysis of FRP materials which had failed catastrophically in applications where the design indicated they would last many times longer. Upon doing an extensive literature search and corresponding on many occasions with DuPont personnel, a picture emerged of a very unpredicatable material. To make the problem worse, the mechanical properties originally generated and the performance exhibited with a newly-made component (in our discussion let's say a knife handle) may degrade tremendously over a few years use.

I won't get into additional details, but I would NEVER recommend FRP for structural applications. Now, of course, if a good liner material is used with the FRP in a knife handle application, there should be no problem. With no liners, the situation is quite different.

In an emergency situation where non-ideal and significantly out-of-plane loads are involved, all bets are also off. The modulus of FRP is not outstanding and deflection and distortion under load occurs to a far greater extent in FRP than in G10, carbon fiber/epoxy, steel, titanium or even an aluminum handle. I would expect some strange and premature failure modes to be observed under non-ideal loading. (I recall a significant number of such problems occurring in an earlier go-around on this topic).

So that's my opinion for what it's worth. Certainly everyone here is free to purchase whatever knife made with whatever materials and of whatever design they choose. I, for one, will continue to avoid unlined FRP-handled folding knives.
Click to expand...
It's good to see that I might not be going in the wrong direction in liking the stainless handled Spydies the best.:).
 
Yes, thanks alot, Blade Santa Cruz, for your expert comments on this matter. Very interesting, and something to think about. Still, I'm happy with FRN knives, such as Cricket and Native, and would buy them again.

I always enjoy commentary from those with some strong technical expertise, and I wish there was more of it here on BF.
 
It is a good thing to have such general discussions. To fill out the background a bit more, the classic example of potential problems I encountered involved key hardware, in fact, a component of our strategic tactical defense triad, that was pulled for a ten-year check. The investigators found an alarming number of the zytel hooks and hangers for electronic cables in pieces.

Now this was a non-structural application, with components lightly loaded. A few, followed by many of the birds in place were then examined. Some showed no indication of the problem while most had a significant number of broken components. That's when I and others were called in to find out what was going on.

We started testing field components and running extended aging studies on test components. At the same time, I found out who had led the Zytel development work at DuPont and managed to contact him. It seems DuPont was aware of a potential problem, but the reports expressed opposing and conflicting opinions.

It turned out we were working with poorly characterized materials, at least when it came to these problems. A lot of money had already been spent with little progress made, and authorization could not be obtained to do the work required to really uderstand what was going on. Then I was removed to chase another gremlin down elsewhere and never found out how or if the problem was resolved.

That experience turned me off on chopped fiber/nylon matrix materials, especially when I'd worked so extensively over my career with carbon fiber (CF) and glass fiber epoxy (G10 type) composite materials. I consider these far superior, if more expensive, to the glass/nylon (FRP) materials.

Another problem does arise in that the flexural, tensile and compressive moduli of FRP is far lower than other widely-used handle materials. As the handles deflect and deform under load, it is far easier to generate complex, non-ideal failure modes and the part fails at much lower loads than expected. Put this together with the environmental aging problem, and I find I'd rather avoid such material systems.

Full Tang Clan - I didn't mean to slide by your question. I'm sure there has been a reasonable data base generated on exposure of Zytel to various solvents and lubricants. However, I've never really worked in that area and so can't help very much. The case I referred to indicated that the reinforced nylons would have a very severe problem with polar solvents or materials. The key component in this case was a very simple polar solvent - moisture! And a modest amount found in an average humidity enfivonment, at that.
 
I think my hand would fail at 80-90in lbs. I've had good, if not excellent, service from my FRN Endura. The clip popped off, but thats been about it, and it is going on almost 10 years of use.


Blades
 
I think it's well known that I'm not a great fan of FRN (no, really :) ), but it's nothing to do with it's ability to do the job or worries over safety, it's just I prefer G10, CF, Micarta and SS.

Catastrophic failure of a FRN handle isn't an issue with me, I've spent most of my life using slip joints. How much pressure do you want to put on the back of the blade whilst your fingers are wrapped around the handle ??
 
This is the kind of discussion I love...regardless of personal preference, I learn from others!
Thank you.
 
Just another small question: is there any difference between FRN and Zytel? I thought it's just the same thing, but I recall someone emphasizing "FRN, not Zytel (handles)".
Thanks for the infos, I learned a lot. Now that's the kind of subject I like :)
 
Originally posted by dialex
Just another small question: is there any difference between FRN and Zytel? I thought it's just the same thing, but I recall someone emphasizing "FRN, not Zytel (handles)".
Thanks for the infos, I learned a lot. Now that's the kind of subject I like :)
Click to expand...

I thought they were basically interchangeable - glass reinforced nylon composite. I assumed Zytel was just a trade name for a particular manufacturer of this material. However I could be wrong. Perhaps FRN has additional properties? Sorry, I'm not a chemist like Blade SC.

Another advantage of Zytel (FRN, whatever) that hasn't been pointed out is that it can be injected molded into practically any shape. That's why I find that my inexpensive knives (the FRN ones) are ironically the most comfortable to hold.

No. I don't work for Zytel. I guess I'm just sentimental since I grew up in a synthetic, Zytel era. :)
 
Zytel is a trademarked name of Dupont's FRN (Fiberglass reinforced nylon). Many companies are using FRN made by many different mfrs, so call them all Zytel is like calling all soft drinks Coke.

sal
 
I doubt that using FRN handled knife will in the way it was intended to be used will ever be a problem. I never liked the look of most FRN knives but Spydie has a few I do like, IF I were going to buy a frn handled knife it would have to a Spyderco. I have also wondered how the FRn would hold up to oil,grease ect. through time but I have a friend who is a mechanic and carries a Spyderco with FRn handles and uses it everyday and I doubt it has ever been cleaned or wiped off but it shows no signs of any problems.
 
Mr. Blade Santa Cruz, like they say in Missouri, "Show me." Why not come forward with proof of FRN failure in a reputable manufacturer's knife? Why not do some testing? Get a used Endura and put it to some materials science tests.

You can't come forward with proof because you're wrong. Conjecture based upon the use of FRN in other materials applications, is just that...conjecture not proof. Too bad some believe your line and now are questioning, of all things, the FRN Delica.

Many who do not truly understand design, engineering and materials science believe that steel, G-10 titanium and overengineering equate strength. Unforutnately, that means your pants hang down on one side and your tool (i.e. concealed weapon to a LEO) is brutally obvious.

In a similar vein, many have criticized the Starmate for having only one steel liner. Some self-proclaimed experts in knife design and street fighhting proclaimed on this forum "Starmate's a nice knife, but for truly tatical applications, G-10 needs dual steel or titanium liners for strength." Terazula and Spyderco have also proved those pundits wrong. Over-engineering does not always make for a better product. The Endura, with its FRN handle, is one of the most popular knives used in self defense classes.
 
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