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Cheap 3D printed fin angle gauges available on SIA


DangerBoy
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I don't know how many of you may be interested in this and have seen this but there's a guy advertising a set of six 3D printed fin angle gauges in the Misc section of SIA for $5 shipped. That's $5 USD shipped outside of Canada but for Canadians, it's only $5 CAD shipped anywhere in Canada. The angles range from 7.0 to 9.5 degrees in 0.5 degree increments. If you have a 3D printer, he provides a link to where you can download the file for free so you can print them up yourself.

 

I bought some and they arrived in the mail today. They look to be very precisely made and are of good quality. They're not flimsy either. Just shy of 1/8" thick. Overall length is 4 inches and max. height is in the 1.125 - 1.375 inch range. Here's a pic of them. Pretty good value for $5 if you're in need of a set of fin angle gauges.

 

Here's the link: ski-it-again.com/php/skiitagain.php?endless=summer&topic=Search&category=Misc&postid=40455

 

1htq6sdangwi.jpg

 

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BraceMaker scores for observance. He is only the second person to point out the wing was on backwards and I have had the post on SIA for a long time. When I was doing the post I grabbed a ski for a pic and it had no wing. I found one, stuck it on and took the pic. Never gave it a thought.

 

Just curious why the lower angles? Are you using the CG fin as some others that asked for the lower angle are using?

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I corresponded with @tjones999 about also making some lower angle gauges since some skiers like the wing set with a lesser angle on the CG Fin. He is going to produce a set all the way down to 4 degrees in 1/2 degree steps. Plus the gauges will be wider to accommodate the low wing placement on that fin. He will post them on ski-it-again as a new set. Looking forward to buying and using them.
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@tjones999 where as I don't currently need the shallow angles - I'm the sort that usually likes to buy complete kits of tools - with the prevailing thought on the CG fin running towards some of these shallow fin angles I'd just as soon have them.

 

I have a little machine shop at home so this will sound silly but the last time I needed to make a fin gauge I used my sine bar and gauge blocks to set a protractor.

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Keep in mind that most 3D printed technology lays down material in .007” thickness. So could be off my .014” so best to “calibrate” with a machined aluminum gauge provided by one of the ski manufacturers (ie Radar for Radar and D3 for D3 etc). Or you can just “EYEBALL” it and call it good. True though if you are going off feel these gauges would be sufficient as you are changing angles based on what you have, so better than nothing LOL.
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@BuoyChaser that error though averages out over the length of the gauge as the gauge has a tapered surface printed at x degrees off the opposite edge. So atleast in theory the two sides should average out very close to the angle. The absolute thickness at one point may be high or low but so long as its sitting on the ski and slid under the wing Id expect the angle to hold quite true.

 

 

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Foregive me if this is hijacking my own thread but some things that were said earlier have really made me curious so I want to ask some questions. I could start a new thread about this if there's any interest in discussing this topic. Let me know if I should do that...

 

Earlier on, @BraceMaker rightly pointed out that @tjones999 had the wing on backwards on the fin in one of his ad pics and @tjones999 explained how that came to be. That got me thinking. It seems to me that we've all (or at least I have) just accepted that the wings are supposed to go on with the angled/tapered part forwards and we've all just done it that way because it seems to make sense. I'm curious to know if anyone has ever questioned that and has tried running the wings backwards like shown in that picture to see what kind of effect it has?

 

For decades it was generally accepted that plane wings had to be swept backwards until someone finally questioned that and did some research. Now there are many examples of high performance aircraft with forward swept wings. https://en.wikipedia.org/wiki/Forward-swept_wing

 

Maybe the ski companies have all toyed with this idea and have done some experimentation with forward swept fin wings so maybe they could chime in on this. @savaiusini ? @adamhcaldwell ?

 

The main point I'm trying to make here or the main question I'm throwing out is if no one has spent a lot of time experimenting with the fin wings turned around in a forward swept-like configuration, how can we be certain that the conventional rear swept configuration we've all accepted as being correct is actually the best way?

 

Again, I could move this topic to a new thread if people want to talk about it so we can keep this thread to just talking about @tjones999's awesome 3D printed wing angle gauges in this thread. Let me know if I should do that.

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It might be that running the fin wings "backwards" might create a bit more drag so it may be that one could run "backwards" fins at less angle to get the same results but this is pure conjecture on my part. There's reallly no way to know without experiments being done.

 

I think the question is quite a fascinating one. For all we know, 20 years from now fin wings may look very different from what they do now and the ones we're using now might look primitive or antique. Or maybe everyone will be using wings that are not much different than what we have now but will be running them "backwards" to the way we run them and this will be the normal way to do things then because some one or some company did some experimentation and found out the wings actually work better that way. In a way this is already starting to happen with fin design with the innovations the mad scientists at Denali are coming out with.

 

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Well @DangerBoy that post of yours generated a bunch of interest. Thx, I think. See if my 3D printer can keep up.

 

Working on the CG Denali set (wider, 4.0-12.0 degrees, it will be 3 sets of 6 since my printer is only big enough to print 6 at a time when they are that big).

 

The other consideration is postage. The current set can be mailed as a letter. The wider CG Denali set being wider no longer fits a COM10 envelope nor is it within the weight range for a normal letter. So when I start selling the CG Denali set they will cost more to make and ship. I suspect it will be like $15US a set including postage so not huge.

 

I will be posting them on Ski-It-Again.com with purchase info and also on thingiverse for those that want to make their own or have access to a 3D printer somewhere.

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@BraceMaker & @DangerBoy

Wings on supersonic jets have traditionally been swept back for reasons of drag and stability. Forward swept wings are so hyper-maneuverable that a human pilot couldn't keep up with the original designs that sought to gain maneuverability at the expense of increased drag. Modern computing power tamed the inherent instability of forward swept wings on some experimental fighter jets. But since modern jets are so stunningly maneuverable anyway, the designing in a drag penalty is unnecessary.

 

If you put your wing on your ski backwards, there may be some infinitesimally small increase in tip pressure at the same wing angle, but it's probably the equivalent of a one quarter degree wing angle increase—kind of a pointless reason to look like an idiot on the dock.

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I bought four sets of these plastic gauges about a year ago, then through them in every boat glove box I spend time in. They work great, don't rattle around or damage the glove boxes, and the set I attached to the dock at Predator Bay spent all summer in the sun with no damage. I prefer using my full sized aluminum gauges, but for $5, these plastic gauges are one of the best deals in water skiing.

 

If you just want a FREE paper or cardboard gauge for a quick measurement, you can download a set that you can print on your regular paper printer at: https://finwhispering.com/shop

tqkldjkx6tfy.png

 

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@SkiJay You say there MAY be some increased tip pressure at the same angle and it PROBABLY would be the equivalent of a small amount of angle increase with the wings on the right way. You very well could be right about this but you have to admit that's just a guess - albeit likely a well educated one. Please understand that I totally respect that you're one of the most knowledgeable people in the world on fin settings but I hope you can see my point that this is sometimes how things get overlooked and discoveries aren't made. People often just suppose doing certain things a certain way will yield certain results but they don't really know until they do experiments and gather data. Data is better than guesses and theories any day,

 

Has anybody ever tried making a fin wing that has a true forward swept design and tested it? I'll go out on a limb here and guess that no one has. If that's true is it because conventional wisdom says a backwards swept fin wings are best and no one questions that? But does anybody really know that for sure? Maybe there's absolutely nothing to this and forward swept or some other radically different fin wing designs are just god awful, but just maybe there's an important discovery waiting to be made there. But no one's going to make that discovery until someone questions conventional wisdom/dogma and does some actual tests. What is there to lose? No one will ever know if a forward swept or some other shaped fin wing design might improve/detract from/have no effect upon fin/ski performance until someone gets curious enough to make some prototypes and does some actual testing like Denali is with their non-conventional fin wings (or fins for that matter).

 

I can think of plenty of successful innovators and inventors who were throught of as being idiots, heretics or crazy until their whacked out theories and ideas turned into important discoveries... ;)

 

And looking like an idiot on the dock wouldn't bother me. Why should I look any different on the dock than I do on the water? :p

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@bhs @tjones999 - another option. Just sell that standard gauge set of 7-9.5 and a 0 degree and 3 degree shim wide enough to stack with the standard gauge and bring it to the depth of the CG's wing holes, maybe print the shim and gauge with some form of an interlock puzzle piece edge.

 

That way you could set the CG to 7-9.5 using the 0 degree, or if you used the 9.5 with the -3 degree you'd have 6.5, down to the 7 degree w/ -3 for a 4 degree wing angle on the CG.

 

Flipped the other way you could go 10-12.5 degrees if you really wanted - all for the time/cost of running two small parts that go along with your standard set.

 

 

 

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0ukvq6cd4cup.jpg

 

I'm certainly no stranger to looking the idiot on the dock myself, @DangerBoy. I've tested something different nearly every set for 300 to 400+ sets per year for over a decade now. And by "testing" I mean complete with written hypotheses, impressions, video analysis and notes.

 

You're right, I used the words "probably" and "may" specifically because my comments on the forward swept wing were a guess, but a somewhat educated guess. And I thought it obvious this test would be a waste of time because even if there is a benefit, it's moot because of the certainty of hooking and dragging clumps of seaweed down the lake with anything on a ski that is swept forward.

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I now have sets of CG Denali wider gauges as well as the regular and I have low angle regular now as well.

 

As @BuoyChaser mentioned you can just use a shim to use your regular gauges with the CG wing instead of the special CG set, but the first person that asked me about the CG fin set tried that and just found it easier to have the wider set and not mess around with a shim. Thus the creation of the wider set. But the wider set costs more to make and mail (they don't fit in a COM10 letter sized envelope like the regular set, they weigh more than 30g, they use more material, and a set of 6 takes at least 3 hours on a 3D printer to make) so I am charging $10 for a set of 6. Regular ones can work with regular alone or with CG Denali fins with a shim. Wider CG Denali ones work only with CG Denali fins. Your choice. (regular set of 6 takes 2 hours to print BTW... so I am not getting rich on any of these)

 

@BraceMaker has a good suggestion but again, adding shims of any form does complicate things and when trying to set angles within 1/2 degree, any time you add complexity you reduce repeat-ability and accuracy so I think I will take a pass on the angled shim approach.

 

So for each type I have 3 sets...

 

3 different sets of regular width at $5 per set

Low Angle: 4.0,4.5,5.0,5.5,6.0,6.5

Standard Angle: 7.0,7.5,8.0,8.5,9.0,9.5

High angle: 10.0,10.5,11.0,11.5,12.0,12.5

 

3 different sets of wide CG Denali Wide at $10 per set

Low Angle: 4.0,4.5,5.0,5.5,6.0,6.5

Standard Angle: 7.0,7.5,8.0,8.5,9.0,9.5

High angle: 10.0,10.5,11.0,11.5,12.0,12.5

 

All listed on SIA in the miscelaneous section and all also available on Thingiverse for free if anyone wants to print their own.

 

I have also changed the regular set just now to have the bottom cut out like the CG Denali set (again at the request of the first person to ask about wider ones for the Denali fin) so that they sit flat on a curved ski base to get more repeatable results.

 

 

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Nice photo, @SkiJay. :p Now that looks like a cutting edge innovation! Revolutionary even. I think it deserves some rigorous testing. Please take video when you try it. ;)

 

It's a good point you made about the seaweed issue. I never thought about that. The lake I ski on doesn't have a seaweed issue so it never entered my mind that could be an issue.

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I've seen people make a small fin move, go out on the water, ski like garbage, start complaining about the fin move, only to come back to the dock only to see their wing mounted backwards. I have personally never done it so cant speak first hand.

 

As an observer, its obvious that its far more significant then a 1/4 degree wing angle change and slightly more tip pressure. Its definitely enough of a change that you will likely miss your first pass until you sync back up, but count on about a 6 buoy deficit from your peak.

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@BraceMaker, I like your idea of a 3 degree shim. It reminds me of stacking 30 -60-90 and 45 degree drafting triangles to get angles in 15 degree incriments. I don't have a wing on my fin yet, but I will probably print a set out with a 3 degree guide when I do put the wing back on.

 

Ryan

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@DangerBoy & @adamhcaldwell

Curiosity got the better of me, so we tested a backwards wing. And I said "we" because I solicited the participation of a ski pro with unassailable testing credentials. Notice that the leading edge of the attachment flange has been chamfered to focus the test on the shape of the wing itself.

 

ustjej5rwg83.jpg

 

The results weren't as extreme as described by Adam, but his prediction was closer than mine. As I expected, drag increased hardly at all, about the same as a ¼° increase in wing angle. But as Adam described, ski behavior changed quite a bit. Transitions like the edge change became abrupt enough to affect skier balance—not enough to threaten the pass, but enough to know something wasn't right.

 

So there you have it. A rearward swept wing is both more stable and more seaweed proof than a forward swept wing.

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@grab2go

What you say makes sense, but it's not that simple. I've experimented with wing locations all over the fin without encountering the same change in instability. I suspect it's got more to do with the same principles that make jets with forward swept wings inherently unstable.

An airfoil with a straight leading edge is very efficient at low speeds, but gets progressively more unstable as speeds rise. Small planes have straight leading edges, fighter jets need the leading edge swept back for stability. And since water is 800 times denser than air, our flow dynamics may be closer to near super sonic air flow than not. The ski pro used the term "abrupt" to describe the ski's pitch behavior. Pilots refer to unstable pitch control as "snatchy." Similar descriptions for similar behavior???

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