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sauls 18th February 2009 01:13 AM

Accurate tuttle fin head dimensions
I have purchased a tuttle fin the is not fitting exactly. I realize that I can use soap or other tactics to determine the areas that are not fitting perfectly. However, I also wanted to use a more empirical approach to determine how best to mod the fin to fit. The brass inserts may not be in the right location.

I also have a deep tuttle that I would like to modify to a regular tuttle and wanted to ensure that I get it right the first time. You know: measure twice, cut once.

I have searched the web for drawings with dimensions and found only one so far (here The trouble is that the width shown is wrong and so I'm forced to question the remaining dimensions.

Does anyone know where I can find a dimensioned drawing of a tuttle box and/or fin head?


Roger 18th February 2009 04:22 AM

Hi sauls,
The other dimensions are pretty close.
The thickness of the Tuttle fin head is 0.620" -0.624"/15.748-15.8496 mm on the original Larry Tuttle drawing (which I am not at liberty to divulge)
The Skoter dwg. needs to be corrected.
The length of the base (at the fin root) is 6.136"-6.140"/155.8544-155.956 mm.
Larry Tuttle measured the upper corners in a different way than on the Skoter Dwg.
The vertical dimension (from the base of the fin head) to the sharp junction at the back end of the fin is 1.250"/31.75 mm.
The vertical dimension from the base to the sharp junction at the front of the fin base is
2.00"/50.8 mm.
Both the top corners get a 0.25" radius from the sharp junctions.
The front and rear angles on the Larry Tuttle drawing are 80 deg. from the base at the wider root side. This is 10 deg. off perpendicular.
The distance between the drilling for the brass barrel nuts is 4.135"-4.140"/105.029-105.156 mm (centered on the top of the fin base). On the deep Tuttle the hole of the shorter end of the fin base is 0.491"/12.4714 mm from the junction of the rear angle and the top angle.
The center of the barrel nut cross drillings is 0.50"/12.7 mm below the top surface of the fin root.
If you modify the Skoter Dwg. with these numbers you will have your own version of the original Larry Tuttle design.
The Deep Tuttle uses all the same widths and angles, it's just 18 mm/0.7086 taller than the std. Tuttle.
If you make your own drawing and send me a copy (not of the forums please) I will check it against the original Tuttle design and make corrections as required.
Best I can do and still maintain my credibility with both Starboard and Larry Tuttle.

MartinJE 18th February 2009 04:23 AM

Hi S

Not that this answers your question (I see Roger has done that) - but after using a few boards, and adjusting fin heads to suit - I think the fin boxes are often distorted during placement in the boards: for example an iSonic 122 2008 - the box was compressed down its length, hence bulged in the middle and required the fin head ends trimming to sit flush; conversely a CA SL58 2006 - the box was slightly compressed in the sides, once sanded down the fin head sank too deep!

This is for stock and 3rd party fins - so, most likely the boxes are the problem.

So - bottom line: whether or not the fin heads are accurate, they'll probably still need to be custom fit to the board.

Regards - Martin

sauls 18th February 2009 05:02 AM

Thanks Roger.

I noticed he has the front and back angles wrong too.


sauls 18th February 2009 07:04 AM

A couple of clarifications.

The 0.7086 higher than a std tuttle, is that measured perpendicular to the root of the fin or perpendicular to the top surface?

radius on the corners between the sides and the front/back edges?

Any idea on the proper drilling for the barrel nuts or will that depend on whether you're using std or metric?

I can't seem to get the Deep Tuttle dimension from the back to the first bolt hole to work out (you said 0.491, I get 0.514). Are the holes in a different location than the std Tuttle box?

Thanks for the Great Reply Roger!!


Roger 18th February 2009 11:16 AM

Hi Saul,
The 0.7086" "addition" is measured perpendicular to the top surface and is parallel with the top surface.
1/4" (0.250") radius on the upper corners and on the front and back corners.
The cross drilling for the barrel nuts needs to be a size that makes the OD of the
barrel nuts a light press or heavy push fit in the fin head material.
No, the top of the Deep Tuttle drawing drawing suggests 0.724"/18.3896 mm from the front junction of the front taper and the top.... then 4.135"/105.029 mm between the hole centerlines.......0.491/12.4714 from the rear taper junction with the top to the center of the rear hole.
Spacing is the same as the std. Tuttle box (actually just extended up 18mm).
Centerline of the front barrel nut cross axis is 0.472/12.0 mm down from the top and the clearance drilling for the fin screws is 1.260/32 mm deep.
As far as where the hole in your fin box is, vs where Larry Tuttle meant for them to be
in the Tuttle fin head that's something you may need to alter.
I've used a rat tail (round) file to slot many boards to get the angle down to the barrel nuts right. Just use a large dia. fender washer with a good large dia. rubber washer under to seal the slot.
Several boards have had the fin screws coming out of the deck at pretty crazy angles.
Good engineering practice would have the fin screw holes counterbored concentric and
perpendicular to the clearance hole down to barrel nuts.
Hope this helps,

cholo 28th August 2010 04:32 AM

Hi Roger,

do you also know what the dimensions of the fin box should be?

Especially the width of the box (dimension around 15.816.0 mm), should how much wider than the fin head?

Roger 28th August 2010 10:15 AM

Hi Cholo,
The fin head dimension (from the original Larry Tuttle (Water Rat) drawing is 0.620" (+0.000 -0.004)
so the tolerance range is 0.6160"-0.6200" which according to my inch/metric conversion program
give the metric dimensions as 15.646mm - 15.748 mm.
So if the fin head width is 15.748 mm max and it is supposed to be an nice snug "push fit" I would guess
that the fin box width would ideally be about 15.75 mm.
Hope this helps,

cholo 28th August 2010 11:49 PM

Hi Roger,

thanks for the fast answer, but I think now I am more confused.
the fin head width is 0.6160"-0.6200", or 0.620" -0.624" like you wrote above in Feb. 2009?

From what you say it seems that the fin head was defined in detail by Latty in a mechanical drawing, but he didn't make the equivalent drawing for the fin box (board side)?
What's most important is the connection, the detailed fin head drawing is not so useful...


cholo 29th August 2010 12:14 AM

Larry, of course, not "Latty", too much hurry...

What I wanted to say: "the detailed fin head drawing is not so useful", without the detailed drawing of the slot on the board (fin box).

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