no mat
aamapes from what i learned when looking into building my S&G, chopped mat is not good to be used with epoxy. I think something about how it doesn’t get wetted out properly or something, but it works fine with polyester resins. it also has a relatively poor strength to weight ratio.
mat… IMO
my glass guy uses mat for just about everything in the repair arena. he’s a PRO and also repairs 50’+ power and sail boats. it bonds better, conforms to bends, corners, etc. and is quite strong.
have fun
steve
Rider… the styrene in esters breaks
down the binder on mats …
I use only cloth…
…except in non critical areas where I just need a filler. Cloth is much stronger than matt and absorbs less resin. The only advantage of matt, other than being cheaper, is that it will conform to complex curves that cloth can’t. Either will work, but I always opt for cloth when it’s appropriate.
BTW, new Valley boats use only cloth except for the deck fittings.
Not surprising
Matt is used a lot in larger boats, but that doesn’t make it the best material for kayak repairs. He probably uses it because it’s what he has on hand. Matt does not bond better (I don’t know where your repair guy got that idea, as bonding is a function of the resin, not the reinforcement material), it’s nowhere near as strong as cloth and it results in a heavier, bulkier repair. It’s only real claim to fame is its ability to conform to complex curves better than cloth. For most structural hull or deck repairs, it offers no advantage other than being slightly cheaper, but the cost difference amount to pennies for the amount used in most kayak repairs.
About the only thing I use matt for is to add thickness and stiffness when I’m laying up bulkhead panels.
Bnystrom…
Could you expand more on the construction of the new Valley boats? I thought I’d been keeping my ear to the ground, but I hadn’t heard that.
well now…
another claim to fame of mat: It is isotropic. This means that it is equally strong in all directions. Mat and fillers are the only composite reinforcements exhibiting this trait. In a repair, especially, this is important. Woven fabrics are oriented in just two directions. The warp and fill yarns run at 0 and 90 degrees respectively. Thus, fabrics are anisotropic, or strong in only two directions. Fabrics need to be oriented so the fiber yarns run parallel to the expected loads. loads in a repair are going to come from ALL directions. If extra strength is needed in a different direction, another ply must be added at an angle to the first. The most common angles are +/- 45 degrees.
pulled from some site I found. 
steve
Certainly epoxy is stronger than
gelcoat, but its margin over vinylester is small.
Four letters, Flatpick
– Last Updated: Jul-19-06 11:05 AM EST –
PAPR
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Jim
The info is from Peter Orton…
…the new president of Valley Sea Kayaks (formerly Valley Canoe Products). Peter came over from P&H and has re-vamped the construction process. The boats are now built with cloth instead of matt. The standard layups are still done by hand, but the higher end layups are vacuum bagged. The weight of the boats has come down, too.
If you have questions, email VSK. I’ve found them to be very responsive.
That’s true, but…
…matt is poor as distributing stress compared to cloth. One of the advantages of the long, directional fibers in cloth is that it helps to distribute local stresses over a larger area, reducing the likelihood of failure. Matt tends to concentrate stresses locally, which means it may be damaged when a cloth layup wouldn’t be, or it may be holed when a cloth layup would be damaged but maintain its integrity. There’s no better demonstration of how durable cloth can be than the videos on the Tideline (Onno Paddles) website at:
http://eteamz.active.com/paddleshop/albums/index.cfm?id=239260
There’s no way a matt hull would survive that type of abuse.