Tubercles On Drive Fins?

I went down to the Silver Bank recently to swim with the Humpback Whales. It was a fun trip, and a report is forthcoming, but this question is really separate from the trip experience.

While there, we learned that Humpback Whales have "tubercles" which are big bumps along the leading edges of their pectoral fins. They have bumpy leading edges because it is actually MORE efficient, which really shocked me.

Here is an example photo:



Those bumps actually help? Yes, they really do, and biomemetic engineers at Whalepower have applied the idea to windmill blades.



All this makes me think I should take my original blades and put blobs of 3M 5200 along the leading edges. Or maybe I should do it to my Turbo Fins?

Anyone else see this and want to mess with Mirage Drive fins? Maybe bump up a rudder blade too? Or am I just nutz?

No, we will all just sit back and watch how yours turns out first Tom. It's cheaper that way.

That is amazing. It's another one of those 'Oh that's stupid' things that then gets proven by a team of engineers and wind tunnel tests, and then gets the 'Oh yea, of course it works' comment. I spose it works a bit like the golf ball aerodynamics.

You didn't take this photo did you Tom ? We also get the humpback whale migration up our east coast and over the next few months is prime time, so hopefully I might be able to get a few shots like this one.

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Don't take life too seriously................it ain't permanent.

I expect everyone wants to shoot you down in flames for heresy, there are 'tubulators' or rough spots on the wings of model aircraft, which cause a turbulent flow at certain speeds, this is more efficient and stops the laminar flow from separating from the wing. I don't have all the details but I expect someone will!

And also Weysail, some high performance cars are doing it with the rear ie: Evo's, WRX's, Porsche etc. with the aim of breaking up the vacuum at the rear of the car.

I spose this is a bit different though as whales don't really fit in the high performance category. All interesting stuff though. If a whale has evolved like this, ya gotta think that there may be something in all this, that may suit the leading edge of an AI's rudder or daggerboard. I think you're onto something Tom.

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Don't take life too seriously................it ain't permanent.

I think I remember Matt posting something a couple of years ago about roughening the hulls of racing yachts so the water would "stick" to them better.

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And VG (vortex generating) tape for helicoptor rotor blades-
http://www.abc.net.au/tv/newinventors/txt/s3138602.htm

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I still have not modified my fins, but I did post one of my whale videos from our trip:

[youtube]http://www.youtube.com/watch?v=iARw1F68hw8[/youtube]

You're joking !!! How mind blowing is that ! So how did you feel Tom ? Did you have any fear at all or was it all as sereal as they say ? Not many people can put that experience on their CV ( resume ).

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Don't take life too seriously................it ain't permanent.

Great footage Tom.

A full trip report is coming.

I was on the end of the line of divers nearest to that mother and calf as they approached, and there was a moment of fear when they turned right at me. They are not aggressive, but can accidentally hurt you. It wasn't really fear so much as the feeling you might get if someone turned a slow-moving bus right at you: Time to get out of the way!

We had been told to just remain still if they want to approach us, so that is what I did. They kept turning and passed close on our other side, and my uneasiness went away. We swam with that pair for a while.

As promised, the full trip report.

This consists of 4 pages on our adventure, including over a hundred pictures, with several embedded videos. It will take 20 minutes just to watch the videos, probably an hour to read it all and watch the videos.

So you might want to grab some coffee before starting...

Swimming with Humpback Whales on the Silver Bank

So, the bumps and knots I have accumulated on my old bald head over the years should be actually making me think faster?

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Island life in the Devil's Triangle:
http://2gringos.blogspot.com/

They should at least make your skull more aerodynamic, improving windward performance in the AI. Also more hydrodynamic, in case you have to swim home!

I may find myself down your way next winter, Gringo. The whale tenders shown in the trip report are here in my yard for repairs, but they must return to the DR by the end of January. One version of the plan has us driving them to the Turks and Caicos on their own bottoms, then they will be towed down from there.

Although it sounds interesting, frankly I'm hoping some other version of the plan comes to pass. That's a long way in two open boats!

Tubercles on Drive fins? IMO, I would have to say not realistically beneficial. What I see is several factual statements that aren't necessarily relevant to the Mirage Drive application.

1. Whales get their speed from the fluke or tail fin, not the pectoral fins. We don't find tubercles on flukes.

2. A Mirage Drive fin develops thrust much like a fluke, essentially a variable pitch, reversible prop.

3. Tubercles are found on the pectoral fins of Humpback whales (not a particularly fast whale). The Humpback has unusual acrobatic and maneuvering abilities for its size though, attributed largely to those long pectoral fins and the leading edge tubercles. The shorter, cleaner pec. fins found on other whales are far more aerodynamic.

4. Since tubercles pertain more to lift and drag than speed, the better potential application might be with the rudder if we want more directional control.

So what about Whalepower windmill blades? If you read the details, they never did a direct comparison with an identical "tubercle-less" or any other prop -- they just read the power specs off the plate. Neither did they get around to calibrating the test instruments. Small details. That isn't to say that the concept is bad, but the result wasn't as conclusive as it appeared to be.

The VG tape on helicopter rotors? This leading edge treatment might theoretically improve Turbofin efficiency, but any positive effect, considering our fin construction and operating speed would doubtfully be significant, compared with adjusting the clew setting for optimum AOA (angle of attack). Getting the tape to stick to a flexible fin surface is another matter.

Matt Miller's mention of sanding the hull on sail boats -- I believe that was with 400 grit sandpaper to insure smoothness and a laminar boundary layer over the hull (opposite result, different application from the tubercle concept).

Time will tell if tubercles offer anything new or are just another variation on well established existing applications such as slots, slats, boundary layer devices fences and winglets. I'm not holding my breath.

Great video on the whales though!

Thanks for saving me from destroying my stuff, Roadrunner!

You're probably right, but let me address your points anyway...

1. What grabbed my attention in the lecture was that he said the tubercles are most effective when the fin is making a sweeping motion - just like a Mirage Drive.

2. A pectoral fin works much the same way.

3. Humpbacks are much faster than Adventure Islands.

4. Yes, I have in mind destroying rudders, centerboards, daggerboards, propellers, AND Mirage Drive fins with my wacky idea.

Thanks for shooting some holes in the idea, though. There is really very little that is new in the world, and something to the idea that if it worked, someone would have used it already.

On the other hand, I did not ever believe I would live to see the paddle become obsolete. I had a great time introducing some newbies to our AI's this weekend, and when I got to the part about the paddle, I told them, "This is a kayak paddle, an obsolete piece of gear you will not be using today. It stows in this clip and under this strap."

I was using my obsolete paddle at the time...