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Oversize fin bolt holes

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Created by dedekam 7 months ago, 25 Apr 2025
dedekam
54 posts
25 Apr 2025 12:03AM
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I just bought two secondhand AV boards Nuvolari. Both boards have oval, oversize, bolt holes that can accommodate 8 mm bolts (se attached photo). The "length" of those holes is 15 mm...!!

Surely this is not ideal? Won't ventilation become a big problem, and/or water getting pushed up through the holes, increasing drag? What is the best way to correct this? Suggestions very welcome..

PhilUK
1098 posts
25 Apr 2025 12:36AM
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I think the holes are longer than normal to cater for fins which are out of specification.
On mine, a larger issue was the box being about 0.5-1mm to long so fins sat too deep in the box. I had to cut a plastic shim from a takeaway food box to put down the front of the box.
Water does come up through the fin box, but no issues with air going the other way causing spinout.
Otherwise very happy with the board. Apart from the Goretex valve. Not required in the UK weather. Soon after getting the board I did the fastest 500m speed in choppy Poole Harbour for about 8 years or so.

?si=no0c3drHB4Vg3MUS

dedekam
54 posts
25 Apr 2025 1:41AM
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Select to expand quote
PhilUK said..
I think the holes are longer than normal to cater for fins which are out of specification.
On mine, a larger issue was the box being about 0.5-1mm to long so fins sat too deep in the box. I had to cut a plastic shim from a takeaway food box to put down the front of the box.
Water does come up through the fin box, but no issues with air going the other way causing spinout.
Otherwise very happy with the board. Apart from the Goretex valve. Not required in the UK weather. Soon after getting the board I did the fastest 500m speed in choppy Poole Harbour for about 8 years or so.

?si=no0c3drHB4Vg3MUS



That's quite a bit a bit of water, but good to hear it won't be a problem. I might add some nylon insulators in order to reduce the water flow, something like this:

se.rs-online.com/web/p/screw-insulators/2326980

Another issue I found just now is that half of the footstrap screws, on both boards, were bent. I will replace all of them, but I am wondering if the screws are the correct type. Did your board come with this type of screws:



PS. I see you have the medium size, I have the two other sizes. Look forward to riding them!

PhilUK
1098 posts
25 Apr 2025 2:27AM
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I bought the board they used for Windsurf mag test so the straps were already screwed in place.

dedekam
54 posts
25 Apr 2025 2:32AM
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PhilUK said..
I bought the board they used for Windsurf mag test so the straps were already screwed in place.


Ah, right. That was a glowing review.

Mark _australia
WA, 23435 posts
25 Apr 2025 8:25AM
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its been used hard or crashed hard if they're bent like that. Often on waveboards, not so often on racey stuff. Have a goooood look at everything if they're bent

choco
SA, 4175 posts
25 Apr 2025 12:09PM
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dedekam said..
I just bought two secondhand AV boards Nuvolari. Both boards have oval, oversize, bolt holes that can accommodate 8 mm bolts (se attached photo). The "length" of those holes is 15 mm...!!

Surely this is not ideal? Won't ventilation become a big problem, and/or water getting pushed up through the holes, increasing drag? What is the best way to correct this? Suggestions very welcome..



Use rubber washer

SBGroupie
15 posts
25 Apr 2025 3:23PM
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If the fin fits properly it will seal any gaps.
Starboard supplied a couple of their oval serrated footstrap washers with a foil board, to be used inverted (smooth side down) on the foil bolts, which works well.

Imax1
QLD, 4924 posts
25 Apr 2025 6:35PM
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As stated above , probably slotted , because fins can be so far out. And because the holes are only 15 mm deep , they should handle way out fins.

elmo
WA, 8868 posts
26 Apr 2025 7:04AM
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Fin holes are most likely OEM and made for use with a foil

If you have a 3D printer or if you know someone with one you can drawup and insert which fits across the whole base of the hole and into the slot, and have it printed out of TPU which will seal it

dedekam
54 posts
27 Apr 2025 5:14AM
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Mark _australia said..
its been used hard or crashed hard if they're bent like that. Often on waveboards, not so often on racey stuff. Have a goooood look at everything if they're bent


Yes, I was a bit worried but otherwise the boards seem just fine.

dedekam
54 posts
27 Apr 2025 5:17AM
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elmo said..
Fin holes are most likely OEM and made for use with a foil

If you have a 3D printer or if you know someone with one you can drawup and insert which fits across the whole base of the hole and into the slot, and have it printed out of TPU which will seal it


Good call, a friend of mine actually has a 3D printer. I'll talk to him.

Imax1
QLD, 4924 posts
27 Apr 2025 5:18PM
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Silly question, please tell me foil heads nuts have the same pitch as Tuttle? And is it true that foil bolts are quarter inch and fins are 6 mm ? Or is that early foils being imperial ?

elmo
WA, 8868 posts
27 Apr 2025 4:01PM
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I believe some foil bolts are M8.

They may also be slotted to allow for tilting of mast

Mark _australia
WA, 23435 posts
27 Apr 2025 5:14PM
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Select to expand quote
Imax1 said..
Silly question, please tell me foil heads nuts have the same pitch as Tuttle? And is it true that foil bolts are quarter inch and fins are 6 mm ? Or is that early foils being imperial ?


Never found non metric in foil

dedekam
54 posts
27 Apr 2025 5:30PM
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elmo said..
I believe some foil bolts are M8.

They may also be slotted to allow for tilting of mast


Yeah, I was also thinking that. But I will be using fins only, going to find or make some oversize washers..

elmo
WA, 8868 posts
27 Apr 2025 6:45PM
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Mark _australia said..

Imax1 said..
Silly question, please tell me foil heads nuts have the same pitch as Tuttle? And is it true that foil bolts are quarter inch and fins are 6 mm ? Or is that early foils being imperial ?



Never found non metric in foil


both my foils are metric

Paducah
2784 posts
27 Apr 2025 8:46PM
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Mark _australia said..



Imax1 said..
Silly question, please tell me foil heads nuts have the same pitch as Tuttle? And is it true that foil bolts are quarter inch and fins are 6 mm ? Or is that early foils being imperial ?





Never found non metric in foil




Had two that were. One built by a refugee to the US as a measure of pride in his adopted land and the other by a US shop that felt that users might find long metric SS difficult to find in the hinterlands (they aren't wrong but the internet solves that problem in a few days if you have the time).
Slingshot is the only significant outlier on M6 that Ive encountered with the original tuttle adapters taking M10 (M6 adapters were available) and the Phantasm jackplates (aluminum) taking M8. M8 is probably a better standard as there have been cases of M6s failing from stress resulting in a lost foil. But, most foil makers hesitate to try to squeeze it into the small space of the head and risking not having enough carbon fiber to keep it together.
For boards without a chimney for the tuttle screw, slotted holes can be helpful as when using a 90 or 100mm screw, alignment has to be at a high standard for everything to be straight. Or, the foil maker, like on the IQ can slot the tuttle head on the mast itself.
So, Imax1, rest easy. M6 will almost always do the trick. However, I have a quiver of screws from 45-100mm in length for various boxes and tail thicknesses Ironically, my smallest board is the one that takes the longest screws.

mr love
VIC, 2401 posts
27 Apr 2025 11:59PM
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Some foil masts have a true deep tuttle with the angled top and others have a "foil" deep tuttle with the top parallel to the bottom of the board. They drill the holes for the mounting screws perpendicular to the top of tuttle head so the screws are at different angles depending which type of deep tuttle it is. The slotted holes in the tuttle box allow for both. Just use a gasket washer when using with a fin.



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"Oversize fin bolt holes" started by dedekam