Is anyone familiar with the advantages and disadvantages of these? I’ve looked up some data on each, but not sure what the implications are for surfboards. I know core cell is heavier, but maybe it shapes better?
I’m interested in using it as a deck on my 1 pound EPS board, and maybe as a stronger material for rails.
Thx.
I’d go with the Divinycell. It is available in various densities, and various thicknesses, all coded by color. It is compatable with Epoxy, or Poly. Easy to shape, and sand.
Corecell and D-cell are both PVC closed cell foams. Depending on your location one may be more available or cheaper then the other. If you have access to both I would recommend the Corecell. If the Corecell isn’t available then the D-cell is still great stuff. The differences in weight are negligible for similar densities.
Without getting into a bunch of technical jargon the main difference is flexibility, (Corecell is harder to flex, D-cell has more flex for a given thickness) and for a density to density comparison the Corecell is a bit more resistant to compression.
I have always thought that a thin corecell deck and bottom with D-cell rails might give you the best of both worlds. Also Corecell has a white to off white color and D-cell is a grey.
Greg,
Core-cell is the superior material. It is not, as some people believe, another brand of PVC foam. It is a different material - Styrene Acrylo-Nitrile (SAN) foam. Divinycell is a cross linked PVC which is more brittle than Core-cell. I did a ton of research on what material to skin compsands with and core-cell came out on top (this was pre-Firewire or Futureshapes). One piece of research that convinced me was a US navy evaluation of hull materials for training yachts that compared a number of materials . Check:
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thx, everyone. I think I need to do a little experimenting on both and report back. I’ll let you know.
Which corecell type is the one to use? There is A-Foam, P-Foam, S-Foam, and T-Foam.
Dave_D
I was told A500, i’ve never done it so please don’t hold me accountable.lol. seems to be fine but what i found yet is 3times as expensive as d cell. i’ll keep searching.
uzzi
that is what I am finding too. and a bit heavier, but some believe it to be a better “marine” product. Thx for the article. I’ll read it tonight.
“Cross linked PVC” a major difference from “Linear PVC”
Yes I believe so. If you look at the mechanical properties for each, elongation is much greater for Linear PVC - I think this means the linear PVC’s are better able to take a beating - more resistant to snapping.
Check:
http://www.netcomposites.com/education.asp?sequence=48
The PMI foam - Rohacell that is mentioned in the above article is what Surftech are using for their TL2 boards.
There is crosslinked and linear Airex, the linear stuff is R63
When I was researching this stuff I checked boat and sailboard building forums - Core-cell and Airex 63 were rated highly but a lot of people stated Airex was hard to sand.
I’m coming from a kiteboard building background. So my experience is from using these foams as core materials with nothing else except glass, Carbon, and Kevlar.
There is a new formulation of D-cell that is out. It is supposed to be cheaper but have improved mechanical properties. I’ve used the H80 D-cell for two years without any failures and only switched to A500 Corecell this past year simply because the D-cell became unavailable in my area. The Corecell 4x8 sheets are only $20 more than the same sized D-cell sheets. The seat of the pants meter is that you can make a thinner stronger board with better flex characteristics with the Corecell. The boards are snappier with the Corecell and a bit softer with the D-cell.
For it’s use in compsand construction with sandwiched construction techniques I seriously doubt that anyone is going to push any of these materials to their mechanical limits in a surfboard. I plane the 3/4" Corecell down to less than 2mm in spots to get flex patterns out of the boards. These will cycle over and over in compression and flexion with just S and E glass skins for years without any breakage. I would be more worried about creating a board that was too stiff. If you can get you hands on some you’ll see how inflexible and dense the foam is. I can see why some of the builders are not using stringers with this type of construction it would give a horrible ride.
If you are looking at the materials from a mechanical properties standpoint only then Balsa actually outperforms all of them. The only problem is there can be inconsistencies with the balsa. A material that some builders had good results from was Balsa in “end grain scrim”. You can get it in sheets and that are very flexible yet have some of the highest compression resistance compared to the foams.
Another secret material is plain old luan door skin. It has a higher compression resistance than the foams and has better flex properties. Best of all it’s about $9 for a full sheet.
linear v crosslinked: think of crosslinks as the “rungs” (of a ladder) reinforcing the molecular chains. Thus the term “crosslink”.
Example below:
Linear vs. Crosslinked Polyethylene
Linear polyethylene is a long-chain polymer consisting primarily of ethylene groups. On the molecular scale, it may be described as a long chain of repeating groups, each having one carbon atom connected to two hydrogen atoms, one on either side. At each end, the carbon of one group is connected to another group.
Individual molecules are very long, generally containing between 10,000 and 100,000 atoms in the carbon backbone of each molecule. The solid polymer contains millions of those long molecular chains entangled together. The strength of the molded polyethylene part lies in the complexity of that entanglement, which mechanically restricts the polymer from changing shape.
Crosslinkable PE resins contain a small amount of crosslinking agent dispersed throughout a linear polyethylene material. The crosslinking agent is designed to decompose at a selected temperature during the rotational molding process.
During the decomposition sequence, crosslinking agents break down into two reactive products, each of which strips a single hydrogen atom from the carbon backbone of the nearest PE molecules. Stripped of their hydrogen, the remaining carbon atoms are reactive and combine with each other, thus “crosslinking” the carbon chains of two molecules.
Strength of the crosslinked PE depends solely on the links, usually no more than one or two for every 1000 carbon atoms. The strength of crosslinked PE no longer depends solely on the mechanical entanglement of molecules, but is reinforced by a network of chemical bonds.
PS- too bad Luan ply is so friggin heavy.