|
Post by vance on Apr 26, 2019 16:34:43 GMT -8
Pics, please!
|
|
|
Post by SeaRat on Apr 26, 2019 19:27:19 GMT -8
Here are some of the photos I've taken of the Spoiler Fin Forensics, and the modification to the Scoop Fin design I pretty much invented decades ago. First, let's look at the original concept of the Spoiler Fins. They have this channel that goes down from the top of the blade to the tip of the blade, and is supposed to channel water in a water jet out the tip from the "dead area" of the fin. As I stated before, this is problematic, as I did not note any water moving out of the tip of the blade when in the water in a swimming motion. Here's the channel when opened: _MG_5884 by John Ratliff, on Flickr Note that it is fairly narrow. Now, if the fin is bent, this channel closes off: _MG_5883 by John Ratliff, on Flickr You can see that the channel is completely closed off. This is why this fin is so rigid. In order to have any hope of "channeling" water through these internal channels, they must remain open, and therefore the blade must remain very rigid. John
|
|
|
Post by SeaRat on Apr 26, 2019 21:44:50 GMT -8
I have now taken two swims with modified Spoiler fins. The first used a modification which was half-way to producing the "Scoop Fin" design; I took off the top part of the blade. The fin performed better, and was more comfortable, without the top blade. I was able to use it for an hour. You can see that fin in the bottom fin in the below photo: _MG_5878 by John Ratliff, on Flickr But what I wanted was to produce a "Scoop Fin" design with this fin. It would be a departure for me, as I would be using foam neoprene, 3/16 inch thick, from the top part of an old wetsuit. You can see the mockup of this fin in the top fin in the above photo. Here is a closer photo: _MG_5879 by John Ratliff, on Flickr But I could not dive it or swim it in this way, as the neoprene which formed the scoop in the blade needed to be secured to the fin. I usually have used pop rivets for this, and choose aluminum ones. But the ones I had were too short, so I had to go to my ACE Hardware store and get longer ones. That I did Thursday, and yesterday late evening completed the "Scoop Fin" modification on one fin. These pop rivets I got were just barely long enough to make them work, and if I could do it over, I'd get even longer ones with a wider top part for better securing to the fin. I had one pull through, which was unfortunate. Here's photos of the end product: _MG_5888 by John Ratliff, on Flickr _MG_5889 by John Ratliff, on Flickr This view shows how the neoprene is flexible enough to make a semicircle at the tip of the blade. I took these two fins into the water this morning, and swam them. The Scoop Fin modification was easier to swim with, more comfortable, and may have provided more propulsion, although my subjective test (swimming with my eyes closed and determining whether the Scoop Fin pushed me off center) was indecisive. I do note that the ribs of the Spoiler fin still almost prevent flexing of the blade, although the center is now free to flex and the foam neoprene allows that flexing. All my other Scoop Fin mods have blades which allow some flexing. For this Spoiler fin, the "Scoop Fin" modification would be worthwhile, in my opinion, simply for comfort, even if the propulsion effect is not as evident as it is in other fins I've modified. The other observation is that the "Scoop Fin" modification with foam neoprene makes these fins floaters now. John
|
|
|
Post by nikeajax on Apr 27, 2019 8:53:49 GMT -8
John, so wait, what yer tellin' us is that the blades of these fins are... hollow-- REALLY! I was wondering how you did the channel for the foam inserts! I thought you'd used a router, "OK, John's finally lost it!" WHEW! I know that with aircraft people have been working for a long time on how to stabilize the air that as it flows over the top section of the airfoil/wing: image from Wikipedia JB
|
|
|
Post by SeaRat on Apr 27, 2019 11:08:19 GMT -8
Jaybird, It's actually two blades, one on top of the other. They form a channel between them, and the theory was that the higher pressure area around the toes would translate into a stream of water jetting down the channel and out the end of the blade, creating a propulsive effect. From what I can tell, it is a flawed concept, having nothing to do with aerodynamics or even hydrodynamics. In other words, it ain't workin' that way. Here's the patent introduction: John
|
|
|
Post by SeaRat on May 1, 2019 16:28:11 GMT -8
I don't have the time right now before my next swim to modify the other Spoiler fin, which already has the top blade removed. But what I'm going to do is to make it into a double-split fin until I can find the time for the conversion to my "Scoop Fin" design.
John
|
|
|
Post by SeaRat on May 2, 2019 17:54:22 GMT -8
I am out of the water, and have put my Spoiler Double-Split fin into the water, along with its sister, the Spoiler Scoop Fin. The two felt like they swam equally well, and much better than the original. The original Spoiler fins, with the blade so inflexible that it could not bend under normal swimming conditions, was a bear to use. I had to take them off after just a little while of swimming them. But both the Spoiler Scoop Fin design and the Spoiler Double-Split design worked apparently equally well. Here are some photos. IMG_1108 by John Ratliff, on Flickr Note that I drilled a hole, then split both sides of the fin blade. In addition, I have taken the top blade off, but left a little bit for the conversion to the Spoiler Scoop Fin design. IMG_1109 by John Ratliff, on Flickr Here you can see that the entire center section, supported by the center rib, can flex. This provides a scooping action similar to my Scoop Fin design, but without the webbing. It works similar to the Split Fins that are out there, but with a more rigid design. IMG_1111 by John Ratliff, on Flickr Here I have pushed down the center section to show the amount of flex available to this fin now that the mods have been made. This allows the Spoiler Double-Split fin to perform better than the original, and also with much more comfort. The Spoiler Double-Split will probably eventually be converted to my Spoiler Scoop Fin design, so that the two will match. But I wanted to show this as a fairly easy way to convert the Spoiler Fins to a design that actually works. John
|
|
|
Post by tomcatpc on Jul 8, 2019 17:32:11 GMT -8
I dove my Spoiler Fins this evening. Honestly, I could not tell any difference between them or my ScubaPro Jets, or my Dacor Turbo II's... Not my favourite, but not too bad... Mark
|
|