Old School Reverse Fins

Had an a brief conversation today with Bill Thrailkill, pioneer San Diego shaper from the late 50s, about shapes “back in the day” for speed. Bill had a part in the original Phil Edwards sig. model for Hobie which had a reverse fin. According to Bill, the reverse shape helped stabilize, reduce slip, and helped with speed. I became interested to find out all I can about the rise and fall of the reverse fin. I did a quick scan through the archives and find mostly cynical comments about reverse fins and a general feeling that they don’t work.

Is there something to the reverse shape for longboard “style surfing”…something we forgot about? Apparently Phil Edwards used the reverse fin on his boards. Maybe Bill will jump in and give his wisdom here along with any of you “style guys” from the “golden age”. What say you about reverse fins?

Worked fine since '66 until you go to turn real hard, then it’s squirrelly, no matter what size. Of course, too big won’t turn.

Weed catcher.

Ever consider the jet plane with forward raked fins? Needs computer to fly it, like an F-117, just not inherently stable for all around use.

Style was never a consideration, only function. My part in the original Edwards Model was no more than being in the same room when either Phil or Terry Martin shaped them. As far as I know Phil was the creator of the reverse fin design. In 1960 I had a thirty minute conversation with Phil, at the old AJ shop in La Jolla, it was a real eye opener. That one conversation changed my thinking about surfboard and fin design forever. Phil was the first person I had ever heard discuss the physics, and science of fin design. I rode boards with reverse fins from 1960 to 1967. Two of those boards were full big wave guns. Both were blindingly fast. Both boards had 6 1/4" deep, thick foiled wood reverse fins. They were ridden in 10’/12’ Pipeline, 15’/18’ Sunset, and big Waimea on a day Buzzy Trent called “the biggest that Waimea can be ridden before it closes out.” None of my boards ever spun out. I mean NEVER! No instability of any kind. Kelp was a problem in California only. Anyone that says that they don’t work, is just ignorant of the true facts. Or perhaps experienced a reverse fin on a poorly designed surfboard. I’ve seen plenty of that.


Would you please describe general specs of the boards that you used which complimented the 6 1/4" deep reverse fin? Did the bottom and rail contours share in the holding power of the reverse fin? Thanks.

Dale, both boards weighed 38 1/2 pounds. One was 10’ 5", the other was 10’ 7". The 10’ 5" was fastest. Nose width 13 1/2", width 21 1/2", tail 12 1/2" to a 4" wide square tail. Rails were 50/50 at the wide point to hard down rail in the tail for clean release. There are many other design nuances that all contribute to performance ,as you know. With respect to the fin, the base was 10 1/2", glassed on with no rope, cloth only, cut on the bias. Belly in the nose, and flat to the tail, with little more than natural rocker throughout the length. That was the state of the art at that time. The fin provided great directional stability. The 3/4" thick foil of the fin, and the glass on technique were major contributers to the overall speed. The high angle of attack of the leading edge of the fin, and the fin placement, provided a positive and stable turning response.


A buddy of mine sent this to me about 4 years ago. Thought you might like to see it.

Surfore, thanks. That is a rare piece of local La Jolla surfing history.

Thanks Bill!

State of the art at that time… and just as functional today. Do you still own those boards, or just have a sharp memory?

Hey Thrailkill,

Do you know if there any photos of the profile of these fins on the boards you’ve referred to?

High aspect fins are the fastest, there’s no doubt in my mind.

Board outline, rail and bottom configuration along with the wieght of these boards had much to do with their holding power.

Good Surfin’, Rich

Dale, I’m blessed with an extremly good memory. Plus I have all my old templates back to 1958. Of the two boards referred to, only one survives, the 10’ 7". The board is co-owned by Erwin Spitz and another collector. A photo of three boards I had shaped appear on page 90 of the AUG 04 issue of LONGBOARD. The board on the left is the 10’ 7". The board on the right is the first hollow stringer board I ever shaped. That board was shaped in 1964 for Terry Hall, and is still owned by him.

Halcyon, no photos, but I still have the original fin template. Perhaps Erwin Spitz will post a photo. The fin on his board is a beauty made of black walnut.


Im sorry I dont have that issue. Could you post those photos from Longboard Mag?

FYI, the current issue has a fascinating article by famous Hot Curl rider, Fran Heath - surfing hawaii in the 1930`s, “Age of Innocence”.


Dale, sorry, I don’t have that capability at this time. Hopefully a kind Swaylockian will post the photo.


I’ve got the issue with the photo and will try to scan and post it (I’m too computer illiterate to figure it out, so my wife will do the honors). Great looking boards Bill. Is that a 48 Ford woodie?

Hi Bill,

Would love to see a pic of the walnut skeg if Erwin happens to post. Thanks for the info on reverse fins.

(template done!)

Here you go boys, I hope this is it.

Yes, that’s it. The car is Terry Hall’s 1949 Chevy wagon. Thank you for posting the photo.


Surefore, where do you find these things? To my eyes this is a rather extreme variation of “reverse” fin design. Do you have any info on who the manufacturer or designer is? Looks like excellent workmanship. It just does not appeal to me. Thanks for your contributions.

So what are the physics of the reverse fin and why did it go away?