Fin location

[Velasco]

Question for those that know, or who have ordered custom racing boards -

Where is the optimum position for a fixed fin (no rudder) with the goal of tracking straighter? 

I thought the answer was towards the back of the board, and with the fin all the way back in the fin box.  But looking at the videos/pictures of stuey's penetrator and some of Ron House's monohulls (the red one Kyle M has been paddling), the fin(s) are further up.

And on www.surfingsports.com (blog pages), Wardog has posted pictures of a Starboard distance prototype board with the same fin config as Ron House's monohull (two fins similar to a keel/daggerboard - rudder setup). 

I would think some of the lessons learned in longboard windsurfing and modern yacht racing would apply here.

Thoughts (before I order a custom)?

[DavidJohn]

Good question.. The fin is way up near the center of the board on this new Starboard . 

DJ

[Tom]

Is that top picture your garage. If so, I'd like to come for a visit.

[DavidJohn]

Is that top picture your garage. If so, I'd like to come for a visit.

Ha..  .. I wish..  .. http://www.surfingsports.com/blog.asp

BTW now I see a rear fin on that board.. 

DJ

[SteveF]

My guess is that the forward fin on the Starboard is primarily for stability. It appears to have enabled Starboard to build a board with a more rounded hull than would otherwise be possible.

[greatdane]

Here is a good picture of the Starboard hull & fin set up.  Although a small one since I stole it from the internet 

[stuey c]

   On the 16' penetrators and the 18'8" that Woogie was riding in the vid, they had 8" finboxes and the box was set in at 42" from the tail on the 16' and 50" on the 18'8". On the new 18'8" that I'm just finishing with my new steering system the rudder is again placed at 50" from the tail. I will post a new vid of the testing soon after tomorrow.......Stuey

[Velasco]

Stuey -

Are you finding your boards track straighter with the fins that forward of the tail?  In your descriptions of the penetrator development, you reference yacht building principles - which would have the rudder further up from the stern on high performance craft. 

I have also thought about fin placement on surfboards - how you want your rear foot over the fin cluster to make use of them - and how that principle applies here.

I am trying to come up with the factors that will go into my next board - thanks for your feedback!

Vic

[stuey c]

 Hi Vic, didnt so much do that from a yacht design point of view, just kind of looked at the shaped boards early in the piece and figured where I thought you would tend to stand when on a runner and placed the fin under the back foot. It worked well and just moved them further forward the bigger the board got...........Stuey

[PonoBill]

that starboard race board was at the battle of the paddle, it had a big, swept-back center fin and a tail fin. Ekolu Kalama was supposed to ride it, but he retired after 1 lap because the board was so unstable in the choppy conditions. I empathize, the age-group races were in better conditions (somewhat horrible vs. totally horrible) and my 12'2" X26 felt line a greased bongo board