Thursday, 8 December 2011

Tomahawk Speed Weed Fin Project

One of my most popular DIY articles - DIY Fin mould, was never finished because I sold the fin half way through the the setup stage.  I plan to cover the topic in full as well as each of the stages leading up to making a mould for an original fin design.  The range of fins I have been working on are Speed Weed Fins.  They have a leading edge rake of 45 degrees and a thicker base similar to the new breed of stumpy speed fins.
 Why a Speed Weed? Well since we don't have any local speed strips around Adelaide anymore we need to travel 5 hours to Lake George for a "fix".  The Lake has weed beds that rise during the day creating perfect speed conditions, unless you start catching the weed on your fin.

My reasoning behind the design is as follows:
  • 45 Degree Rake to shed floating weed as well as starting in weed beds.
  • Thick base to reduce fin depth and keep the centre of lift as far forward as possible.
  • Thick base to minimise twist and flex which are killers in weed fins for heavy sailors.
  • Leading edge set forward of base to keep the centre of lift as fas forward as possible.
  • 9.5 Percent Chord/Thickness ratio for a good compromise between power and speed.
  • Notched trailing edge(on bigger fins) to maintain flow attachement at low speeds/high angles of attack.
  • Full Carbon Fibre body construction for minimum flex.
  • Glass Fibre leading edge for abrasion resistance.
I am no fin expert but I have done a lot of research and know what I want from the design.  If the symmetrical design is successful I plan to make poth Port and Starboard Assymetrical speed weed versions in the smaller sizes.

The symmetrical range will be (Right to Left):
T30 30cm 400cm^2
T28 28cm 361cm^2
T26 26cm 323cm^2
T24 24cm 287cm^2
T22 22cm 253cm^2
T20 20cm 220cm^2
T18 18cm 188cm^2


  1. Great Project! Can't wait to read more.

    Btw, for abrasion protection I use carbon rovings covered with ceramic powder.

  2. Hi Fred,
    Is that ceramic powder as a filler in the resin? I have used aluminium powder and talc before...where do you buy ceramic powder? Chemical or Resin supplier.
    Regards, Tim.

  3. Hi Tim,

    no, the roving is first impregnated with pure unfilled resin and is then covered with the powder, creating a ceramic pipeline. I only use them for the edges but you can also make the entire fin with ceramized carbon rovings.

    For the moulds I use this as a filler in the resin.

    As casting is very popular over here, you can buy it in every hobby/artist shop and on ebay under several brand names: keraflott, keraquick, artestone ...I've done a bit of search for that kind of stuff on ebay australia but had no success.