Mariner  kayaks are carefully constructed of the finest quality corrosion resistant materials. We are continually researching resins, gelcoats and fiberglass fabrics to produce kayaks of great strength and longevity. Currently the materials used include sewn double biased fiberglass fabric, woven roving, reinforced gelcoat and vinylester/polyester co-resin.

Decks and hulls are manufactured using a laminating process (vacuum-bagging) where the composite laminate cures while under constant pressure. Vacuum bagging allows us to use a stronger fabric (without the resin running down the vertical walls and pooling in the bottom before it cures as would happen if the same husky materials were hand-laid). Vacuum-bagging provides a smooth corrosion resistant interior that is not nearly as abrasive as hand-laid glass interiors. This smooth interior saves wear and tear on your skin, shoes and gear bags and makes it easier to slide gear bags into place. Because the laminate is held under pressure while it cures the ideal ratio of glass fiber to resin for maximum toughness can be achieved. In contrast, even the best hand laid laminates must use a much greater percentage of resin (the more brittle component) than is desirable. Extra resin is used to avoid the more serious problem of air infiltrating the laminate. The laminate expands some when the liquid resin stiffens as it begins to harden. This expansion will pull in air unless there is enough extra resin on the surface to be pulled in instead. The vacuum bag barrier keeps air from infiltrating the laminate while allowing the use of just enough resin in the laminate to thoroughly glue all the glass fibers together. The result is a much tougher laminate.

Strategically placed fiberglass and foam core reinforcements also add impact, folding, and abrasion resistance in critical areas of your kayak. Decks and hulls are joined with fiberglass seams both inside and outside for watertight integrity and extra strength. 

Note: We do not use the much cheaper to build with (but weaker and more leak prone) vinyl extrusion in the seams ( found on many sea kayaks today). Claims that materials costs are higher using a molded vinyl extrusion seam are very misleading because the labor cost is so much greater with fiberglass outside seams that the  material cost differences are of comparatively little consequence. The reality is that the far greater labor expense in building a kayak with fiberglass outside seams translates into a $150 to $250 higher retail price for that kayak. We think the trouble free security using  fiberglass outside seams (as well as fiberglass inside seams) is well worth the extra cost. If some one tries to tell you that vinyl extrusion seams are the more costly, ask them how much less they would charge you to build one of their kayaks using  fiberglass outside seams rather than with the vinyl extrusion.

Another Note: One company is claiming that seams are the weak point of a fiberglass kayak and that their glued together overlapping seams are stronger (they even include an animated diagram on their website purporting to show stresses concentrating on the seam joint of a flexing kayak). We believe that while gluing a kayak together in one step may certainly be a lot less expensive building method it is unlikely to be a stronger method. Because of the extra thickness of fiberglass materials at the hull/deck seam, the seam area of even kayaks with vinyl extrusion seams are stiffer and less prone to bending not more prone where their diagram predicts.  It is more likely that the seams are one of the sturdier parts of the hull because the stiffer seams are less subject to bending or buckling (the usual cause of damage--at least away from any part of the kayak that is taking a direct blow). The addition of fiberglass outside seams to this joint, like all Mariner kayaks have, further helps prevent flexing at the joint. 

Having seen damage to a wide variety of  kayaks with different construction methods and materials over the last 26 years, it has been our experience that the weaker parts in the kayak are more likely to be right next to the seams rather than at the actual joint in the middle of the seams. Because of this we taper the joining materials thickness, thickest at the middle of the joint to thinner toward the edges of the joint tapes. That way, the flexing stresses won't be focused into such a small area at the edges of the seam tape as happens if the transition from the more flexible deck or hull to the stiffer seam area occurs over a shorter distance. Overlapped/glued seams are likely to have a sudden transition from one thickness of fiberglass to two (in the overlap area), creating a potential stress riser on each side of the stiffer overlapped area. Stresses tend to concentrate where the laminate is most likely to be bent sharply. If the stresses are great enough, damage will likely occur first in the most vulnerable area, often right next to a sudden transition to a stiffer area or some other area that concentrates or focuses the forces into a small area. 

I suspect one of the hardest things about building kayaks with glued together overlapping seams is preventing gaps and leaks in places along the glue joint. Most owners of a kayak that is getting water inside the compartments think that their hatches must be leaking. While this certainly can often be the case, if the kayak has vinyl extrusion or glued seams, we have learned to check the kayak's seam area first (by putting water inside the kayak and watching where it comes out as you rotate the kayak around) when looking for leaks. Our experience has been that the seams of kayaks (those not seamed with resin and fiberglass tape on both the outside and the inside of the hull) have often been the source of annoying and hard to find leaks. The area within several feet of each end of the kayak is the most likely place for a seam leak. I suspect that's because this area is the hardest to see from inside of the kayak during the seaming process. The builder is essentially working blind in that area.