DV8 550 Experiment!

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

DV8 550 Fin Design

As part of our continued development of the DV8 series of fins we recently did an experiment with the way we were constructing the new thick fins we are testing.

The main motivation for this experiment was to try and make a thick fin that was lighter and stiffer than one made from a solid 3/8" fiberglass panel. In order to accomplish this we decided to try using a combination of fiberglass and PHENOLIC as it is very light but incredibly stiff. For this experiment we used the paper based version of PHENOLIC.

We will go into a little more detail than normal so people can better understand the process for producing the fin shown in the photo.

  1. Scribe and cutout the fin template (DV8 550) from a 1/4" thick AMBER TINT fiberglass panel
  2. Cutout a matching template from a 1/8" PHENOLIC panel
  3. Cutout filler pieces for the tip extensions from a 3/8" OPAQUE WHITE fiberglass panel
  4. Run the PHENOLIC pieces through a thickness sander to remove the finish from one side
  5. Glue the piece of PHENOLIC to the BACK of the AMBER panel
  6. Glue the tip filler to the front side of the tip of the AMBER panel
  7. Profile the fins as a matching pair
  8. Machine the base down to 1/4" thick to fit the fin box slot (GEARBOX)
  9. Machine a taper from the base of the fin to the bottom of flip tip
  10. Machine the angles into the flip tip on both the back and front faces

Now we have the fin blanks ready for foiling.

It is a little more work foiling these thicker fins, but at the same time it also is a little easier as the foils are so much easier to achieve. With this set of fins the hard part was making the hollow foils on the inside face. The reason it is so hard is that PHENOLIC is very hard to machine, the sandpaper has to be fresh and it loses its cutting ability very quickly. So you go through a lot more paper.

Once foiled these fins have the PHENOLIC exposed at both the leading and trailing edges through the bottom 2/3 of the fin. If you look very closely at the photo you can see that there is a dark brown section. This is the section that is covered with PHENOLIC, after that there is a section of AMBER through the transition area from the main blade of the fin into the tip extension. The WHITE section is the main part of the tip extension. The tip in the photo is a little deceptive as the WHITE tip makes it looks as if the tip bend starts at the bottom of the WHITE tip. But in reality it starts about 1/4" below the top of the PHENOLIC section. This is mainly due to the fact that the thickness of the fin is 1/4" at the bend of the flip. This means we have ground into the AMBER panel by close to an 1/8".

Yes, we know this is all a little detailed and nerdy, but we thought it might be helpful to understand how these fins were put together. A lot of work but well worth the effort in order to get additional test results on the impact of stiffening the bottom area of the fin. We already know the impact of thickening the fins.

Next up we are also going to do one more test run with a set of fins that are constructed the exact same way but using G-10 instead of the PHENOLIC. This will make it a little easier to foil but will add to the cost due to the increased cost of the G-10. This is also an excellent way to make DUAL TAB fins that have almost indestructible tabs as the G-10 really reinforces them a lot!

More to come!


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