FangyFin DIY help, hints and show us ya fin page

Courtesy of Peter (Waricle) the first batch of titanium barrel nuts.
On the plus side - Very light, very strong and approx 9mm (3/8") so we can use these where space is limited.
On the downside - the galvanic reaction with the aluminium maybe be an issue ( the Aluminium is the anode and will corrode). They will also be expensive compared to the standard brass nuts - possibly twice the price.
On to the testing...!! And then I will let you know whether its worth pursuing
Thank you again Peter

Anyone used Duralac to isolate the barrel nut from the alloy?

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olskool said..
Anyone used Duralac to isolate the barrel nut from the alloy?

I did not know about this stuff - looks like it might be the ducks nuts

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remery said..
But renowned metalurgist Robby Naish says that he uses titanium bolts for less corrosion resistance with aloominum...

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Hmmm, maybe Robbie is talking about 'marketing' type of corrosion. Or perhaps there is something else going on that I don't yet understand - mind you, he does have his cap on backwards...

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Imax1 said..
I think people worry too much . Has anyone had a Fangy fin that has exploded with corrosion ?
I pack mine away wet and I only get slight crusty white dots which brush off , ( 10 sec ) , with a scratchy pad . At this rate of corrosion I should be OK for the next 5 years before I need to sand it . No issues around the brass barrel nut.

The worst I have had was a Bunnings brass barrel nut stripping its thread. The brass turned out to be plain steel with a very thin 'brass' coating. Doh! Lesson learned.

Have used Duralac extensively in marine industry. Great for preventing galvanic reaction. Have seen it last 8yrs or more on painted alloy where stainless fastenings used. No corrosion.
On the same hull ,same grade screw into painted alloy.No Duralac. Bad corrosion after 12months. Cab of boat needed repaint. All bcoz someone DIDNT take that extra step n Duralac a few fittings.
Sure its messy to use n sticks to everything, leaving its telltale pale yellow mark. But well worth the pain.
$30 tube of Duralac or $8k repaint 2 years down the track?

As a follow up on Elmo's anode post previously, I was given what I think is an excellent idea by a FF owner yesterday ( if you are concerned about corrosion). Buy some small zinc galvanised self tappers. Drill them into the base somewhere and then grind off the head - super cheap and easy sacrificial anode!

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elmo said..
I had a thought (another poor lonely little thing it was).

Are these fins hollow? is the fin based recessed?

If so just paint then simply these inner surfaces with cold galvanizing paint, couple of good thick coats and you now have a anode attached providing it gets wet

That seems like a very nice and simple solution Elmo. I will pick up some paint and try that just to see what happens. As alluded to by Imax, I am not sure if anyone has actually had a problem with corrosion yet, but if it ever surfaces as in issue it's good to know we might have some potential easy fixes on hand.
Just as a side note - the FF 18V2 test fins will be solid. The production fins will be hollow if the foundry can find the sweet spot of hollow size vs failure rate/casting shrinkage distortion. The hollow is so physically small and narrow on this fin, it maybe a case of the hassles of saving a few grams outweigh the benefits.

No reply? Hmmmm...Cmon Fangsters.
How far down from PB housing does barrel nut go?
My issue is coz ive cut fin head to suit PB the rear barrel nut for Tuttle won't have enough meat above it when screwed into board.

Easy. Fangy fins bear on the fillet flange n rely on the bolts to hold, not on fin head in board recess.
So cut finhead to PB shape n taper as per PB.
It'll easily fit in Tuttle.
Use 2 barrel nuts in Tuttle position with rear one lower(closer to fin tip) than standard Tuttle.
1 barrel nut for standard PB position. Will hafta use longer rear screw than standard for Tuttle.
So 10mm alloy above barrel nut?

^ Thanks Remery. Hmmm.. I hadn't thought that the barrel nuts would end up too thick for PB/Tuttle application. Lucky ive drilled no holes yet.
Guess if I put barrel nuts closer to mounting flange it'll cut down the amount of grinding needed.
Also need longer Fangyfin specific bolts for each board.
All good thanks!

Oops! Sorry Olskool I was asleep at the wheel again. In universal box preps, after some experimentation, I now place all my barrel nuts close to the fillet end. This gives the thickest base section and least lateral torque action on the bolt. Also, the amount of width reduction required on your barrel nut is kept to an absolute minimum.( you will still probably need to do some width reduction because the PB Is still a smidge narrower at the base)


Bolt hole location - if you don't have a jig: Tuttle - Place the fin in your board and carefully drill a small pilot marker hole using your board bolt holes as the template. Remove from board and check the holes have 105 mm centres. Then scribe/draw a guideline down the side of the base section at 80 degrees to the fillet, similar to what you have done with the white lines above, in line with your pilot holes. Then drill a full depth pilot, check you are vertically placed in the base and 80 degrees to the fillet at frequent intervals.
When complete, at approx 8mm up from the fillet drill a barrel nut pilot through the base sideways - it must intersect with your bolt hole perfectly in the middle. Check that the barrel nut holes have 105 mm centres. If all good, drill full depth bolt hole making sure you stay on the 80 degree alignment and follow with barrel nut hole.
Power box - drill the bolt holt at 90 degrees to fillet base as per above.

Fangy, I've not got a protractor or angle-ometer.
So 90deg to upper powerbox base cut out will give me 80deg to fin fillet flange?
Remery, don't worry ive got no drill press either, n no workbench. Using the local parkbenches for my Fangy Fiasco mods.

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olskool said..
Anyway I first attacked it with 40grit then 80grit flapper disc. Next was 180grit wet n dry. Then 360 grit wet n dry. Finished with wet green scourer. Any need to take it further?

Just noticed this one - 360 is fine. The experiments done so far suggest the higher polished surfaces have better lift, the lower polished foils have slighty low drag, but significantly lower lift.

TBH the power of the FF28 foil is such that I think the surface finish will make very little noticeable difference to early planing ability. What you have already done will be good.
In the most basic sense, More lift = early planing, but because nothing is that simple, More lift = More drag = slower top speed. It's always a trade off to some degree.