We talked briefly about the spread tow carbon fiber we intend to use in this upcoming wakesurf board build. We are emphasizing the componentization of this next build, where we select the best material for what we believe is needed in that specific area of the board. So the bottom of the board will get one treatment, the deck another, the rails yet another. The composite sandwich methodology we use to build our Flyboy Wakesurf boards gives us this flexibility. Not only can we isolate the external areas, we have the ability to isolate the internal components also. One such internal component is the skins of this composite sandwich. If you’ve followed along with our various builds you know we’ve used Balsawood, Corecell, Rohacell and as in this build, Divinycell.
Divinycell is a crossed linked pvc foam, as oppossed to linear pvc foam. The concept of cross-linking is much like the rungs of a ladder. Linear is like the rails of a ladder without the rungs. The linear PVC is more flexible and can be considered more tough, much like comparing a rubber band and toothpick. The rubber band is capable of more tension and bending, but those properties aren’t really suitable for broad application in a wakesurf board. The cross linked variety is much more expensive, stiffer and we feel better suited to the demands of a wakesurf board.
One of the biggest benefits of the FlyBoy Wakesurf boards composite sandwich constructioon is the virtual elemination of heel dents. The construction allows the distribution of compression forces over a greater area than convetional construction, as well as, using a significantly harder and more dense foam compared to conventional constuction. That more dense foam, the skin of the composite sandwich doesn’t crush or compress like non-structural lower density foams and so is capable of distributing compression forces over a greater area. Imagine a slice of bread in comparison to a thinner but much more dense piece of balsa wood. If you apply enough pressure, with say your fingertip, to the slice of bread it dents leaving that depression just like the foam in conventional construction. Do the same thing with the balsawood, using the same pressure and there is no denting, but in effect the pressure is being spread over the surface of the balsa wood, you just can see it. This is how the higher density skin on the composite sandwich Flyboy Wakesurf boards work.
Again if you’ve followed us for any period of time, you’ll recognize that we routinely use a 5 pound density foam, with divinycell that is the H80 density. For this prototype we are increasing the density to 6′ish pounds, plus we also have thicknesses ranging from 3mm to 6mm. You know that the stiffness of a composite sandwich is derived principally by it’s thickness. In effect, the way we build our Flyboy Wakesurf boards is a cobination of 3 unique sandwiches. Each of the skins has a ply of reinforcement, thereby making up a composite sandwich with a core, plus the two skins are connected via an EPS core, making a separate third composite sandwich. By increasing the thickness of the skin thickness we can alter the stiffness of that component. It would be feasible to have the deck skin twice as thick as the bottom skin with an exponential increase in stiffness to four times that of the bottom.
This is the H100 we referenced earlier, you can see that it has a tan or yellowish coloration and might remind you of Corecell A500.
This is a picture of the H80 Divinycell that we have used most often, it is gray in color and it is a 5 pound density foam.
Interestingly enough, the compressive forces on a wakesurf board are rather unique when subjected to aerials. In terms of elapsed time, the deck skin is under compressive force the longest. Every minute a rider stands on the deck, it’s under compression, but not a whole lot of compression. Building a board to withstand that amount of compressive force doesn’t take much. In fact, you’ve seen the picture of the truck parked on one of our R&D boards. That takes more strength! Interestingly enough, landing from an aerial imposes some of the greatest compressive forces on a wakesurf board. Breakage on the deck side of a composite sandwich is almost always attributable to neglect or abuse, but the bottom can be the result of insufficient reinforcement. We should take a moment here and mention that Divinycell is typically considered a core foam, but we use it for the skin, because it is significantly more dense than the foams used in wakesurf boards, save for compression molded offerings.
Remember a few posts back where we talked about the tensile strength of wood and how the amount of force calculation included a factor for the amount of time the speed went to zero? That’s what landing from an aerial includes. Gravity is propelling the wakesurf board and wakesurfer unit down towards the wake accelerating at 32 feet/sec squared. That impact, while short-lived, is much greater than anything on the deck side, except for that very same landing. So we have to build to withstand that impact and it is greater on the bottom of the board, than on the top. Theroretically, we should be contemplating increasing the compressive strength of the bottom in some fashion. There isn’t impact issues, but there is compressive issues. This build will examine that theoretical concern hopefully address it!
10 comments
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January 19, 2012 at 8:44 pm (UTC -7) Link to this comment
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Teeryncappone
January 20, 2012 at 4:58 am (UTC -7) Link to this comment
i think not all of you agree with that .. but i have to say
an arab … learn the languge :d
thanks
Bethany Rice
January 20, 2012 at 8:51 pm (UTC -7) Link to this comment
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Antione Salz
January 21, 2012 at 12:00 am (UTC -7) Link to this comment
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Vivian
January 22, 2012 at 8:03 am (UTC -7) Link to this comment
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las artes
January 27, 2012 at 6:09 am (UTC -7) Link to this comment
I’m cleaning out the shop, I have 5 wakesurfers for sale, as is. I need to sell these, so don’t hesitate to make me an offer on one or all five. From the left. 4’2″ Walker Project Fast 50. I took second at the WWSC Men’s amateur in ’06 on this board and won Tulloch last year with it in the Master’s division. 5’8″ Surftech Barney – used twice. Super light. This board is $550 new. Great ocean grom board. 4’5″ Shred Stixx custom, like new, used 2 days. 4’11″ Shred Stixx JaMako…this board has nose damage. I’ve fixed it, but it’s rough on the nose. Rest of the board is in good shape. Alot of life left in this board. Save $440! 4’6″ Custom composite sandwich, D-cell h-80 skin, 1# EPS core. Good starter. Any one board $50, $100 if I have to ship it PLUS actual cost of shipping…I don’t want to ship them because it’s a pain. $200 takes the whole lot, if you pick up.
Sugel
January 27, 2012 at 6:10 am (UTC -7) Link to this comment
Without belaboring the math involved, the stiffness of any composite beam is determined by the distance between the facings. That is to say, in referring to a wakesurf board, the thicker said board is, the stiffer it will be. Also, the stiffness increase is exponential. Increasing by a factor of 1 increases stiffness by a factor of 4. In our wakesurf board the core of the board acts like the web of an I-beam and the fiberglass skin acts as the facings. The composite sandwich improves on this, by placing a high density foam skin between the two layers of fiberglass on the deck. On a normal surfstyle wakesurf board there is no distance between the two layers, and so by increasing the distance the stiffness is increased drastically, as well as improving strength and dent resistance.
Amberly Burtschi
February 1, 2012 at 2:46 pm (UTC -7) Link to this comment
Most of the time I’d have to agree. Last year during when I was shopping at Walmart I had a similar issue. I recently to acquire it.
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February 3, 2012 at 6:24 am (UTC -7) Link to this comment
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Jackson
February 3, 2012 at 10:51 am (UTC -7) Link to this comment
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Best wakesurfing boat
January 18, 2012 at 4:31 am (UTC -7) Link to this comment
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