How do the vents actually work?

[Danny D]

Nemrod really knows his stuff...he has been diving since there were no fins.... Id say he has a good understanding of fins and he has a few dives under his belt so listen to then man.

p.s.boloney macaroni that is just silly.....I think we should send some of those hose cutters after this person ......

 

[rgbmatt]

C) you have no proof that fins exactly like the Jetfins minus the vents would not in fact work better so then

You should try taping the vents on a pair of Jets and see what happens...

 

[Nemrod]

Sorry I was smart alec-----I get carried away sometimes--fingers out run the brain you know. I have taped them, I see no difference but then some have taped those split type fins as well with mixed results. Maybe they work some, maybe they don't, I think they just mostly look cool and sometimes that is important as well. Peace. N

 

[Allison Finch]

Allison, obviously you do not realize ---A) we not talking about split fins and B) Jetfins are not split fins and C) you have no proof that fins exactly like the Jetfins minus the vents would not in fact work better so then D) I say baloney macaronni. N

Nem,
you need to READ my post! I made one sentance about splits. The rest addressed the vents in the jet fin. My comment about the rocket fin is the only fin that I said was less efficient. That was a proven discussion that I had with a USD rep in 1975, who represented the rockets and ADMITTED that they could not use the patented (and more efficient) SP vent angle. I made no comparison about the more modern copies of the Jet because I simply don't know where they stand. I also made NO comparison to non vented fins ANYWHERE in my post.

Please, read before "venting".

 

[dbg40]

PERFECT! this is exactly how they are designed to work. And for the past 15 years have for me. If its a fad its been going strong since 1965!!

 

[Nemrod]

Please, read before "venting".[/QUOTE]

As I said, I was sorry I was smart alec, also I read your post and I did not understand obviously what you said.
Can you please provide actual test data that records thrust, energy input, speed graphed against effort against caloric burn that supports the supposition that vents actually do a darn thing other than provide good looks. I would like to read it. I have JetFins and I have tapped the vents and darn if I can tell the difference but then I don't perhaps have the muscle power to push the fins to the point where the venting becomes effective, that may well be possible because I go much faster with UDTs or Mares Planas with much less effort and neither are vented. Perhaps some kicking styles make better use of the vents than others. Nonetheless the Jetfins are fine fins for those who like them, no my Jets are not for sale, may come a time when I need boots and they are hard to beat when you need to wear a boot, vents or not, they are a great fin with a long and grand history. N

 

[willydiver]

Wow, what a touchy subject! I appreciate all of the high spirited responses. Allison, thanks for the explanation of the turbulence reduction. I was under the wrong assumption that the vents made the upstroke easier.

The idea of taping the vents to compare is great. I'll have to check that out. I have heard on other posts, that Scubapro's patent ran out a while back, hence all the Jet copies available now.

I wonder if the Aqualung/US Divers' Rocket II's are designed with the previously patented vent angle. I'm just real interested in them, since they've got the extended foot bed and are designed similiarly to the SP Jets. I dive coastal rivers with a ton of tidal current. I love my SP Jets for the short distance power they have while crawling along the bottom, but long swims on the surface back to the boat cramp my feet.

Since there is ALOT of difference in people's kick styles, I guess the vent advantage theory is hard to lay out across the board.

Appreciate all the great opinions/insights.

WD

 

[Kestrell]

Kestrell, I'm pretty sure that Willydiver is asking about the older Jetfins, not the new twin jet split fins.


As to the question of how those fancy vented fins work ... they are just a gimmick. They'll never last. One should use big flat board fins. (sound vaguely like what many now say about splits????)

You are right. I just re-read his post. I guess I was thinking it was more likely to have someone to ask about splits than Jets.

Thanks.

 

[SangP]

Hi,

I'm very curious about the way vents work and a friend of mine commented that the reasons why rockets don't perform as well as the jets was due to the material rather than the vents although the way the vents on the rockets are angled would allow water to go through the fins on rather then allowing it to be channeled through the fins like in the case of the jets.

Please don't think that it's a qualified statement but merely an expression of opinion.

I would think that materials rather then vents are the major contributors to performance. Apparently there seems to be little difference between fins with channels and those without.

SangP

 

[willydiver]

Hi,

I'm very curious about the way vents work and a friend of mine commented that the reasons why rockets don't perform as well as the jets was due to the material rather than the vents although the way the vents on the rockets are angled would allow water to go through the fins on rather then allowing it to be channeled through the fins like in the case of the jets.

Please don't think that it's a qualified statement but merely an expression of opinion.

I would think that materials rather then vents are the major contributors to performance. Apparently there seems to be little difference between fins with channels and those without.

SangP

SangP,

Could you post some closeups of the US Divers Super Rocket II's you had mentioned in another post? What's your opinion on the performance of these versus the SP Jets?

Apparently the patent on SP Jets has run out, as there are now ten different copies available on the market. If the previously patented "super vent angle" of the SP Jet fins were really that great, every new fin made should have it as part of there design. If USD Rockets had worse performance due to their vent angle, wouldn't they change that design flaw as soon as it was legal to copy the SP Jet vent angle? Surely they would at least incorporate it into any new designs they put out (EX: the new Super Rocket IIs)?

If anybody has the new Rocket IIs and could post some comments/pics that would be great. Thanks!

WD