So much for a dry boat-Zephyr problems!!!!

ClassFive Boats · Post by **ClassFive Boats** » Fri Apr 07, 2006 11:23 pm

Ive posted about polypro resin systems (twintex) in another thread I think.. Its not as tough as high quality epoxy, according to the manufacture Saint-Gobain Vetrotex but stronger that vinylester. . It is a pre preg material and like all prepreg's the resin to glass ratio is fixed by and large. Pin holes are caused by oxygen being traped in the laminate when the mold is heated and the resin liquifies. Its a problem thats hard to control. As the boat flexes , the resin will micro fracture. If your boat is leaking when its fairly new, It will unforetunately increase as the boat becomes more flexabe with wear. The basic problem with all composite boats is in the nature of composites'. There is no complete blending of components as compared to say plastic. Its not a fully homogeneous structure and the components break individually . ( the glass remains intact but the resin is breaking down for example.) . Twintex according to vetrotex, is a blend of fiberglass or carbon with polypro resin. Dagger made a few kayaks using twintex. but decided they would be too expensive to mass produce. If you enjoy reading the tech stuff, heres a link to Saint-gobain in regard to twintex..........http://www.sgva.com/products/rna_twintex.html... Its neat stuff , but its still a composite boat and has certain composite boat weaknesses I believe.

ncdavid · Post by **ncdavid** » Sat Apr 08, 2006 3:01 pm

Chris,
I hadn't responded to your offer to paddle on Monday, since I was scheduled to work that day. But I've manipulated my way into a day off. So I'm up for paddling Wilson Creek if we have enough water. If not, maybe we can paddle French Broad Section 9?

David Sink

Martyn · Post by **Martyn** » Sat Apr 08, 2006 3:12 pm

Hey Class V Boats,

You have done a much better job of explaining what I suspected. Friends of mine worked at another canoe company for a long time. They were trying to figure out ways to further lower the weight of kevlar boats. It seemed that the less resin you used, the more prone they were to pinhole leaks. It didn't seem to affect the large-scale structural integrity of the boats, but it wasn't too appealing aesthetically. As far as I can tell, there is a bit of a black art to minimizing boat weight and avoiding pinhole leaks. In light of my previous dealings with Esquif, I'm pretty sure they will get to the bottom of it and continue to provide us in the open canoe world with great boats.

Martyn

Post by **sbroam** » Sat Apr 08, 2006 3:40 pm

I wonder if there is a way to bond a layer of vinyl to the Twintex on the inside. That could take care of the pin hole leaks and allow gluing in of anchor points with a familiar process. I wonder how much weight that would add or if you could get a suitable bond...

ps - if this works, I won't insist on a patent and royalties, just a free boat!

Rumplestiltskin · Post by **Rumplestiltskin** » Wed Apr 12, 2006 9:17 pm

I was just wondering what type of molding process has to be used when building with Twintex.

Is it possible to vacuum bag the Twintex layers before/during heating?

How much heat (what temperature) is required to liquefy the pre impregnated polypro resin?

If epoxy is still King of the Hill for strength, why bother with using polypro?

msims · Post by **msims** » Wed Apr 12, 2006 9:34 pm

cost? poly-pro may be a filler material.
________
Rohypnol Rehab Dicussion

the great gonzo · Post by **the great gonzo** » Wed Apr 12, 2006 10:02 pm

Rumplestiltskin, polypro is used in Twintex because it is a thermoplastic and not a thermoset resin, like epoxy.
A termoplastic resin can usually (there are some excemptions, I think, college was a loooong time ago

) be molded when its heated up close to the melting point. This allows the manufacturer to prepare twintex, i.e. fiber reinforced polypropylene sheets, which can subsequently be heated to close to the melting point and formed.
This process is, as far as I can remember not possible with thermoset materials. Once the reaction between the resin and the hardener has started, it's an irreversible process, once cured, the resin will not become moldable again, if heated beyond a certain point it will simply be destroyed withaout having become moldable again.

If a factory is set up for large scale production, thermoplastic resins are easier to handle and allow for much faster cycle times.
Simply cooling down the molded product les it harden again and the next piece can be built in the same mold (matter of minyutes or a few hours , probably less, While with a thermoset laminate the hole layup is usually biuilt inside the mold and then needs to stay in there significantly longer to allow an adequate cure of the resin, so it's a much slower process.

msims, no, as far asI know the polypro is not just a filler, it is the resin that's used in twintex.

I have seen a Zephyr demo boat on the Upper Black river in Ontario last weekend, and in this one the outfitting (d-ring patches and such) was all epoxied in, no vuylil patches, everything was donne in glass or kevlar.

martin a.k.a. the great gonzo!

richard · Post by **richard** » Fri Apr 21, 2006 1:27 pm

In a perfect world there would lots of new designs and new materials. The boats would be fast, dry, stable, responsive and light. they would also be cheap.

As open boaters in this imperfect world we should be thankful for Millbrook and Esquif, who, each in their own way offer the only new designs and new materials available to us.

The Zephyr is a friendly design made from an innovative material, let's be thankful that the folks at Esquif continue to push the envelope.

Got water in your boat? Do you paddle whitewater?