Go Back   Starboard Forums > Windsurfing School

Reply
 
Thread Tools Display Modes
Old 29th August 2010, 08:17 AM   #11
Roger
Dream Team - School Guru
 
Join Date: Aug 2006
Posts: 2,110
Default

Hi Cholo,
My mistake in the previous post. I got the tolerance backwards.
The Larry Tuttle drawing gives the fin head "thickness" (the dimension that fits in the slot and need to be parallel and close tolerance on both the fin and the fin slot in the boards is:
0.620" -0.000 +0.004, so what I suggested in Feb. 2009 is correct.
Max fin head dimension is 0.624" (15.8496 mm) and the min. fin head thickness is 0.620" (15.748 mm)
There fore the slot in the board should be 5/8" (0.625") (15.875 mm) if you allow 0.0010" clearance to get the fin down into the slot.
So, based on the Larry Tuttle drawing, the size (width) of the fin slot would be 15.875mm or 0.6250" minimum.
Sorry for the error.... my laptop battery was dying and I got in a hurry.
Hope this helps,
Roger
Roger is online now   Reply With Quote
Old 29th August 2010, 05:35 PM   #12
cholo
Member
 
Join Date: Aug 2006
Posts: 33
Default

Hi Roger,

so, roughly summarizing:

fin head width (mm) = 15.80 +/- 0.05

fin slot width (mm) = 15.875 -0.000 / + ?

The problem is that all Deboichet Custom (I have 2008 SL4's made by UFO) have fin head width of 16.05 / 16.10.
Old Starboard tuttle boxes were much wider than that and I even used mylar spacers up to 3x 0.3mm (!) in order to have good fit. That was also happening for other board brands. Now I have changed for a new isonic and the deb's simply do not enter the fin slot, which is around 15.8 mm.

My big question mark is whether to work the fins or the board.
Considering that I'll keep the fins for many years and will buy more deb's soon, and that I'll change the board every one or two years, I would prefer to enlarge the board fin slots to 16.15 mm.

But, if fin slots (Starboard and others) from now on will always be 15.8/15.9 mm wide (as Tuttle drawing), maybe I should consider to work all my fins, once for good? (with no possibility of return...)

What is your suggestion?

Cheers
Cholo
cholo is offline   Reply With Quote
Old 29th August 2010, 08:31 PM   #13
Roger
Dream Team - School Guru
 
Join Date: Aug 2006
Posts: 2,110
Default

Hi Cholo,
The obvious answer (to me anyway) would be to open up the fin box on your iSonic, and continue to use your fins that fit all your other boards.
I just received a 2010 iSonic 121 WC and I noticed immediately that the fin box is not the std. Cobra box
we have seen for the last 10 years.
Obviously they have redone the interior mold for the fin boxes on the new iSonics, and my guess would be that they spec'd. the original Larry Tuttle design dimensions.
So, we may see better (closer to Larry's original desin tolerances) quality control on all Starboard fin boxes, but then again maybe only on the "hand crafted" high end, very expensive iSonics.
Enlarging the interior of a fin box, already installed in a board, is a lengthy hand work process unless you have a fairly large milling machine and some very special very long end mills and a way to swivel the
cutter to the front and rear taper angles.
So, working the fin heads down seems the logical way to fix this issue.
Maybe a better way to go would be to make up side shims for your other boards, and then epoxy the
shims into the fin boxes to decrease the interior width.
This is something you could do in a pretty straight forward manner, without any large precision tools required.
You could cut off the head on a broken fin, and carefully tap a couple of holes and grind/file/sand it to the correct width/length/depth, and use it as a "master" to "cast" the shims into the fin boxes on your other boards, then work down all your fin heads to this spec. The tapped holes could be used to "pull" the master plug out of the fin box after the epoxy slurry you use to hold the shims in place has cured.
Hope this helps,
Roger
Roger is online now   Reply With Quote
Old 30th August 2010, 12:19 AM   #14
cholo
Member
 
Join Date: Aug 2006
Posts: 33
Default

Hi Roger

actually I made a mistake in the slot width measurement of the isonic (I removed the caliper from the slot before reading, therefore I got smaller values!), the right value is more around 16.0/16.05 mm.
Anyway, I can only measure the beginning of the slot, the feeling is that deeper in the slot the thickness is getting smaller.

So I take even more happier your suggestion of leaving the fins as they are and work just a little bit, with sanding paper, the board slot.

By the way, what is the slot width you measure on the 2010 isonic 121 WC?

Cheers
Cholo
cholo is offline   Reply With Quote
Old 30th August 2010, 09:41 AM   #15
Roger
Dream Team - School Guru
 
Join Date: Aug 2006
Posts: 2,110
Default

Hi Cholo,
I'll have to get some precision tools and measure the new iSonic 121 fin slot.
I can use an adjustable parallel to measure at least half way down in the box.
I'll try to do that in the next few days and let you know what I find.
I would make it a priority, but Hurricane Earl is bearing down on my "hideaway" in Cape
Hatteras, so that gets my main focus until Hurricane Earl gets past the Outer Banks of
North Carolina.
As far as "sanding" your fin box, I think you will be at it a very long time.
Perhaps get a file and be able to remove more material, and right where you need to remove it.
Another option would be one of the tiny wheel air driven belt sanders and make some sort of guide
so you simply widen the slot, not put tapers in it and goof it up.
Hope this helps,
Roger
Roger is online now   Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +7. The time now is 01:52 AM.