DV8 QUAD G-10 Experiment!

Posted by: Robin Mair | Posted on: | Category:

DV8 413F & 513 QUAD Design

In the last post we mentioned that we had one more experiment we wanted to perform with the construction of these fins. Well the above photo is the result of this latest experiment.

For this experiment the fin blank was glued up with the exact same procedure as described in the last post, the main difference was that this time we used a piece of 1/8" G-10 as the backing plate, in place of the PHENOLIC. For those who don't know what G-10 is, it is a material made up of fiberglass layers and epoxy resin that are compressed in a very powerful press into flat panels. This allows the typical 1/4" panel to have many more layers than one of our standard fiberglass panels, with a much lower resin content. This makes the panels incredibly strong and very stiff. G-10 is often used in place of metal for some applications, one example, on a lot of modern racing sailboats the chainplates that hold up the mast are made out of G-10 instead of stainless steel!

This quad set was for a DUAL TAB base setup, by using the G-10 we not only met the requirements for the stiffness, but it also meant that we got the added benefit of an incredibly strong base even with those small tabs. These fins do not flex in the bases like most DUAL TAB fins and are certainly going to be a lot less likely to snap off.

Because of the flip tips, the body of the fin is very stiff, but there is still flex in the tips where we would prefer to see it as the G-10 only extends to the base of the flip.

You might be wondering why we are interested in more stiffness, there are a couple of primary reasons.

First, in our testing of these fins with the larger flip tips, one of the problems we ran into is that they can hum at very high speeds and loads. Normally, humming is attributed to a bad foil, or some problem with the trailing edges (often from spray), but with these designs it was something completely different. When these fins are made out of a 1/4" panel with the extended flip tips, at high speeds and loads the fins flex enough that they flutter causing them to hum. The minute we started using 3/8" panels this problem disappeared. Although to be honest the only time the problem showed up in the first place was when using the fins in a tow board on waves with 30' faces, and even then it was very intermittent. Since moving to the thicker materials this problem has completely disappeared.

Secondly, the increase in stiffness makes the fins a lot more responsive, by this we mean that when you crank a turn the fins react immediately without delay making them feel a lot more responsive and fast. The characteristic shows up even more in bigger surf where it matters. Normally with a more flexible fin it will flex as it get loaded the starting a turn, this causes a slight delay in reaction time, by increasing the stiffness this problem is mitigated.

We are blown away by this set of fins, these things look like jewels even if we do say so ourselves. Foiling them was an absolute joy. Plus the presence of the G-10 made it so much easier to dial in the edges as this material hard and therefore not very easy to over sand. The way that the SMOKE TINT fiberglass transitions into the G-10 at the leading and trailing edges just looks insane. The fins in the photo have not been retouched in any way, this is what they looked like when finished. In this case the finish is just oil on the sanded fiberglass. Now admittedly we sanded all the way to 500 grit, but after that there is nothing but the oil. We like this finish because it leaves the foils unadulterated by spray. Also makes it a lot easier to tweak them if needed!

After this experiment we have now concluded that this DV8 series needs to be made out of 3/8" panels, and at the very least for the larger fins they can definitely benefit from this composite approach for the assembly of the fin blank.

We have to be frank though, these fins will not be for everyone as there is no way a fin like this can be made inexpensively, until we start molding them. This is a very labor intensive and time consuming way to make a fin. But as far as we are concerned they are worth every bit of the effort, as it makes something that is a highly function piece of art.

So what is left to do? The only thing we are going to be experimenting with are the use of different colors for the fiberglass parts of the fin blank, to see what the effects are when foiled with the G-10 backing, so purely aesthetic!

Next up we are doing a set of AMBER TINT and G-10, followed by a RED TINT and G-10! We'll post some photos of these variants as we get them done.


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