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Innegra S & H

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    Innegra S & H

    There isn't a forum for paddlecraft construction, excepting Wood/Canvas, so I guess general discussion is our daisy for new developments in boat building!

    Innegra Overview

    Innegra is a high density polypropylene; an aromatic polyethylene. It has very low specific weight and low tensile strength and modulus mechanicals combined with high elongation to failure. Innegra lowers fabric weight and increases resistance to flexural failure. Compared to Kevlar it is roughly half the weight, hydrophyllic, and bonds better. Fabrics are bulky, or thick, for given weight. Thickness and weight, Innegra floats on resin, are best controlled with infusion to minimize resin content.

    It is used to sheath thick carbon race car chassis to control traumatic splintering. We've seen it in a Wenonah canoe and on SUP boards. Most experimentation has focused on thicker ~500 mill laminates, but paddlecraft utilize thin, 35-45 mill, three to five layer laminations. Innegra can be placed on the inside or outside of thin laminations, or both, sheathing stiffer materials, or internally as captured layers. Which choices will optimize paddlecraft laminations?

    Innegra S is available as woven fabric in various weights/ thicknesses. Innegra H is bi-woven with E glass, with basalt, a natural material with characteristics between E and S glass, or with carbon. Innegra H is also hybridized with basalt or carbon into bi-spun or co-mingled threads and woven into fabric. There is a broad array of hybridized Innegra S and H configurations.

    Basalt/Innegra combinations currently price near Kevlar, Innegra/carbon hybrids near 100% carbon prices, so we need product improvement to justify use. For example, Innegra/Carbon comes closest to a whitewater worthy laminate but at unacceptable price; the basalt hybrid most closely approximating acceptable river tripper pricing. The expense and learning curve of converting to infusion lamination and the cost of attendant discardables further complicates paddlecraft pricing.

    Several Canadian composite infusion manufacturers have sample yardage in house and hulls built. We can assume several US infusers are also working with the material for canoes, kayaks and other items amenable to composite construction. There should be quite a creative range of laminations available in the next few years. Lamination schedules will coalesce with industry experience and prices lower over time as volumes increase.

    CEW Oct 14

    I'll try to get some images of I/B, I/C hulls up
    Last edited by charlie wilson; 10-22-2014, 10:02 AM.




      Very interesting layups discussed in some of the SBIR PH I report.
      Some of the weight savings were impressive, but could those same savings be translated to canoe/kayak designs?
      Do you expect to see flexible hulls with pneumatic stiffening chambers in canoes anytime soon?
      And the results of that short beam shear testing on representative coupons was quite impressive...
      See stripperguy's photos


        If you're looking for a Beta Tester I'll throw my hat into the ring


          All right, how much lighter would a Keewaydin 15 pack boat be in the Quad Woven Innegra/Carbon and the full carbon tec package in the trim pictured? And how much would they charge? And how quick can they make it! Lol


            There should be a new DSM diagnosis - OLD = Obsessive Lightness Disorder.


              Innegra is new stuff, and it probably won't have a 50 year run like Kevlar has had. Weight saving and strength increases will be incremental. We're hoping for a pound or two less weight, and some increased durability. Swift's tech package, composite thwarts, handles and end caps, may same a pound or so over bolted in wooden thwarts, etc in pack canoes. We're working on a few new wrinkles for kneeling/ sit-high canoes, but again, no more than a pond or two. The big steps in weight savings; Glass fabric replacing wood/canvas, Kevlar replacing glass, vacuum bagging which reduces resin content and infusion which allows integral rails are already achieved. We're just nibbling around the edges to achieve small progression[s] towards Lighter, Stronger, Faster.
              Last edited by charlie wilson; 10-23-2014, 08:21 AM.


                A few pounds and more strength is always a great thing! I know I am spoiled with the composite thwarts, handles and end caps on mine and the integrated rails are great. Not a single bit of wood/metal to worry about. The future materials may be better yet, but every pound saved is worth some effort! Will be interesting to see the pricing on this!


                  Beam thickness in lamination strength

                  Strength and resistance to flex in composites is a function of the resin and reinforcing material used and panel thickness. Composite reinforcements are available in an array of mechanical properties including tensile strength, resistance to being pulled apart, and tensile modulus, resistance to bending. They also come in varying thicknesses, which is important as panel stiffness increases as ~2X the square of thickness.

                  Given two plates of any thickness, T, increasing thickness to 2T results in a 3.5X gain in bending strength and a 7X increase in panel stiffness. Increasing thickness to 4T results in 10X strength and 37X stiffness improvement.

                  To address the question of resin uptake, let’s control panel thickness and compare weights

                  5.5 oz / sq yd Kevlar, 4.9 osy Innegra and 10 osy fiberglass are ~11 mill thick. VE resin has a Relative Density of 1.02, similar to water before out-gassing when catalyzed, gelled and hardened. Using industry standard 45% resin content for infused fiberglass, resin per sq yard weighs about 9 osy for 11 mill laminates. This will vary somewhat with weave tightness or Per Inch Thread Count, PIC; loose weave holding more resin.

                  When infused, the fiberglass sheet will weigh ~19 osy, the Kevlar panel 14.5 osy and Innegra’s 13.9 osy. The organic materials save about 25% of panel weight for the same thickness. This is born out in hull weights after trim and outfitting are excluded. Further performance is a function of each materials mechanical characteristics.

                  I think any difference in resin weight between glass/carbon and the aramids and HD Polyethyenes is pretty small. The weight difference is mostly a function of differential fabric weights.


                    I wish I had some meaningful response but I don't. I'll just say thanks for posting things like this. It's interesting reading and I'm learning a lot....mostly that there's a lot I don't know.



                      Does anyone know if there is anyone developing a material that would perform like Royalex?


                        Google says



                          I keep reading and rereading Charlies posts. The understanding is dawning slowly and in minute increments. Not often on the interweb that you read something that requires thought and is not a one liner.

                          As far as T formex ( reminds me of a dinosaur!). it remains to be seen whether any other manufacturer will buy sheets of it or if Esquif will be the only one using it. I keep thinking of the stranding of Mohawk canoes. The website( updated last winter it seems) indicated they were trying out new materials too.


                            I'm about 90 degrees away from you, Mike.
                            While I am keenly (some would say fanatically) interested in hull performance, I am fascinated with the materials and manufacture, especially the production methods.
                            My background is highly technical, yet my exposure is limited to R & D and one off production. The methods, materials, tolerances that I need are far away from the average industrial or consumer needs. The technologies that I live and breath are invisible to some, the products are too advanced for the masses.

                            When Charlie speaks of materials, my ears perk up! When he discusses manufacturing methods, I can hardly sit still!! I dare say I'm as much intrigued with how boats are made as I am with how they perform...but that's just me. I enjoy the higher level derivations, but I know from intimate experience that those discussions can cause much eye-glaze. (eye-glaze, the substance produced in abundance when the uninitiated are exposed to the unfamiliar).

                            I think this diversity of members is what keeps me hanging around...everyone is a quasi expert in something, I thoroughly enjoy seeing through the other folks' perceptions.
                            See stripperguy's photos


                              My summary is that the new composites coming on-line are a bit lighter and stronger, and have an interesting visual appearance.

                              My car, toaster, and washing machine are utilitarian items. Canoeing is my enthusiast’s hobby, so I am extra interested in all aspects of canoeing. Some of the info is over my head, but I absorbed much of it.

                              My paddling season is essentially over. I'’ll take what I can get. If you are not into it, don’t read it. Simple.
                              Last edited by DaveO; 10-29-2014, 12:53 PM. Reason: typo