Many Different Composite Layups.
My Expedition Kevlar Swift Osprey has been pretty well abused, including some hard hits, without too much harm. I believe a similar Royalex boat would weigh about the same as the Osprey.
My standard layup Millbrook Souhegan suffered a broach that resulted in 3 tears in the chines (since repaired). I’ve seen royalex boats fare as badly or worse in similar pins. I expect that boat would weigh 20 to 30 lbs more in Royalex.
The old J200 I had seemed to crack if I even looked at a rock. It also weighed about 20 lbs for an 18’ solo.
Tommy, what was the nature of the
tears in the chines? Were they parallel to the axis of the boat, or perpendicular?
I test-paddled a well-used Millbrook Defiant before I ordered my Big Boy (or “Edsel” as Kaz seems to have withdrawn the Big Boy from his lineup). It was interesting to me that the Defiant had tears in the Kevlar in the chines, that ran parallel to the axis of the boat.
Kevlar’s lack of compression strength, and liability to be “scrunched,” may make it vulnerable to failure in chines. If the bottom of a Defiant is struck hard and deep, the chines will be compressed, and perhaps the Kevlar fibers may fail. Inside chine repairs might be better done with S-glass or carbon, while outside repairs might be done with Kevlar.
Twin-tex?
anyone here familiar with the Twin-tex material that Esquif uses? How does it compare in toughness with royalex, kevlar, fiberglass, etc.
Tried one
The one I tried paddled well, and was a compromise in stiffness between the usual plastics and the usual composites. I think it is a bit of a compromise in toughness too. It would likely be plenty tough for regular hard use, the only downside being that repair may be more difficult due to bonding issues. Perhaps they have the bugs worked out, and maybe West G-flex works, but early on nothing was sticking to it.
Twintex
Well, one of my two boats is an Esquif Mistral. Bought it used last winter for a “Song” and paddled it probably 30+ days this year. Have not “Babied” it and it has been used exclusively on rocky, Ozark streams. Bottom pretty scraped up, but hull is “Sound” so far. It’s probably seen more use in one paddling season than many in 5-10 years. WW
http://www.pbase.com/ozarkpaddler/image/126055545
http://www.pbase.com/ozarkpaddler/image/126674476
getting to the fiberglass …
– Last Updated: Oct-26-10 12:20 AM EST –
....... what I am speaking of is the actual fibre of glass (a single strand) , the bundles of glass strands then woven or other are what we know as the cloth .
It is my understanding that these strands of glass are sucseptible to degradation , breaking down of their properties , weakening and therefore breaking .
It's not simply the possibility of an impact break in a laminated shell , but a break (crack) that has occured because the glass strands have been degraded (chemically broken down) by exposure to chloride ions and acids .
A chloride ion or an acid attacks the glass stands ... they need to be kept protected from contact with these things . It's not so much the strength of a composite matrix , but the degradation that occurs when the glass strands become exposed .
E glass is more sucseptable than S glass , but both are degradable . Scour or abraid the surface of a glass cloth that has been used in a layup and now it is exposed (plus it will have some physical strand breaks) , stripped of it's barrier coating , it will be attacked by chloride ions and acids ... it will degrade (breakdown) and the next thing that happens is it's function as a stiffner fails and then the composite cracks . You can think of this process as similar to the way UV breaks down plastics ... the glass strands need to be kept protected .
In my way of thinking , the greatest function of gelcoat is to protect the glass strands of the cloth . Chew up the gelcoat (or whatever the barrier coat) and expose the glass strands , then the very water you paddle in will contain the chloride ions and acids that attack the glass strand .
I know that glass is susceptible to
chemical attack, and over a very long time, will very slowly degrade in water. But I have never seen anything in the composite material literature to suggest that glass, Nylon, polyester, Kevlar, Spectra, or any other fiber used to lay up boats has been observed to degrade when encapsulated in epoxy or vinylester. If a layup is hammered and smashed enough that water and chemicals can reach the fibers, then slow degradation may occur. But experience with composite whitewater boats (my experience goes back to 1973) indicates that cloth degradation (other than that caused by mechanical abuse) is not significant.
Repeated severe mechanical bending can degrade both the resin matrix and the cloth. Truth told, such bending can even damage poly boats, but it takes longer.
One thing that is seldom mentioned— FG cloth has a coating to make it bond well with epoxy or vinylester. That coating degrades while FG cloth sits on the shelf, and FG cloth that is over roughly 4 years old should not be used for high stress layups or repairs. This is discussed on sweetcomposites.com.
that coating is called a “sizing” …
– Last Updated: Oct-26-10 8:27 AM EST –
....... the sizing applied to the glass strand can be (will be) damaged by water .
The individual glass strands can abraid each other . Becuase of the higher tensile strength of S glass , the sizing is even more critical because the S glass strands would readily abraid theirself if the sizing is damaged .
This sizing is first used to protect the glass strands from abrasion and breakage during the manufacturing process . Afterwards the same applies , but it (sizing) also is used to increase the bonding properties between the glass and the resin .
Amazing as it is , fiberglass strands are "glass" . Very fine thin strands of glass ... glass threads !!
Guess what. I have a batch of S-glass
with no sizing. I don’t know how they did it, but it’s great to have repair material that isn’t going to degrade from humidity. It’s kind of an unattractive mottled tan, but as you know, I don’t care about appearance.
Brit Wit ?
ha ha ha ha ha … at 'ere is funny, I don’t care who you are !!! LOL
chloride ions, acids ??
– Last Updated: Jul-05-14 12:19 PM EST –
where are you paddling ? Sounds like Love Canal ! I doubt the amount of degradation you describe could happen in a lifetime, or at least not the usable life of the boat. If so, I'd suggest looking for water with a higher pH. :-)