If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#51
|
|||
|
|||
Why don't wings have dimples?
"cavelamb" wrote in message
ink.net... Peter Dohm wrote: "T o d d P a t t i s t" wrote in message ... "Peter Dohm" wrote: The Embry-Riddle link leads to someespecially fascinating discussion, including that some efects of the dimples are related to Reynolds Number. However, I clearly have a distance to go before understanding this subject--even enough to safely apply any rules of thumb. If you are interested in the aerodynamics of spinning balls, or want to try to extend the state of our knowledge of aerodynamics as applied to aircraft design, then by all means, keep on looking at dimples. However, if your real interest is in reducing the drag of an aircraft, you'd be better off studying up on laminar flow and interference drag. There is enough information out there in the glider community on fairings, control seals, inexpensive laminar flow testing techniques (old motor oil, pieces of yarn, microphones or stethoscopes) to keep you busy for a long time and which will really produce drag reduction. -- T o d d P a t t i s t (Remove DONTSPAMME from address to email reply.) Make a commitment to learn something from every flight. Share what you learn. Well, I already know a lot of the rules of thumb for drag reduction, especially with laminar flow, and that is my first choice for choosing or building an airplane. I am also interested in general aerodynamics, and am somewhat intrigued by the issue of dimples. Particularly, grooves and dimples could be quite interesting as related to propellers. Regrettably, there is a /very/ finite limit to the percentage of time I can devote to that, so my progress may be gradual. Regards, Peter All we need is a wind tunnel... You're right. Then we could prove a lot one way or the other--especially if a little smoke was part of the system. There would still be the effects of scale and Reynolds number, which are supposed to be quite significant, but a lot could still be learned. At least it should be possible to either verify or deny the assertion that grooved or dimpled props produce a virtual "switch pitch" effect. Maybe next year. Regards, Peter |
#52
|
|||
|
|||
Why don't wings have dimples?
"Peter Dohm" wrote You're right. Then we could prove a lot one way or the other--especially if a little smoke was part of the system. There would still be the effects of scale and Reynolds number, which are supposed to be quite significant, but a lot could still be learned. At least it should be possible to either verify or deny the assertion that grooved or dimpled props produce a virtual "switch pitch" effect. Maybe next year. I would be willing to bet a month's salary that at *least* one of the big prop makers have done all of this kind of research. After all, these companies strive to eek out hundredths of a percent improval of propeller efficiency. Any takers? April Fools! (so I'm a little late, sue me! g) I'm too poor (and not enough of a gambler) to risk any of my salary, even if it is a "sure thing" bet! g Still my point stands. Me thinks that if these tricks have not shown up on your manufactured props, the gain is not significant enough to be worth the effort of incorporating them into the props. -- Jim in NC |
#53
|
|||
|
|||
Why don't wings have dimples?
"Morgans" wrote in message
... "Peter Dohm" wrote You're right. Then we could prove a lot one way or the other--especially if a little smoke was part of the system. There would still be the effects of scale and Reynolds number, which are supposed to be quite significant, but a lot could still be learned. At least it should be possible to either verify or deny the assertion that grooved or dimpled props produce a virtual "switch pitch" effect. Maybe next year. I would be willing to bet a month's salary that at *least* one of the big prop makers have done all of this kind of research. After all, these companies strive to eek out hundredths of a percent improval of propeller efficiency. Any takers? April Fools! (so I'm a little late, sue me! g) I'm too poor (and not enough of a gambler) to risk any of my salary, even if it is a "sure thing" bet! g Still my point stands. Me thinks that if these tricks have not shown up on your manufactured props, the gain is not significant enough to be worth the effort of incorporating them into the props. -- Jim in NC The issue is certainly not in first place on my priority list. But I am not ready to suppose that it can't be done, nor that it hasn't been done. There seem to me to be good and sufficient reasons to suppose that the big porp makers might *not* give much effort to certifying and announcing higher performance props for the low end of the performance spectrum. For example, if the effect is sufficient to be really usefull on a 100 to 115 Kt airplane, it might also make the performance of the prop more sensitive to surface condition. In addition, if applied to SLSA, it could become more tedious to certify within the limitation on maximum speed--and there are already some which require aerodynamic faults introduced for the US market with their existing props. That leaves the Cessna 172 as the only obvious candidate for which anyone might certify and announce such a prop. Remember that the major prop manufacturers are primarily in the business of certified props for certified engines which qualify for single engine night and IFR flight. It has been done before; the Cessna 150 received a Clark-Y prop, which was regarded as a fairly new improvement, shortly before it was replaced by the Cessna 152. I am curious, but not holding my breath. Peter |
#54
|
|||
|
|||
Why don't wings have dimples?
"Peter Dohm" wrote That leaves the Cessna 172 as the only obvious candidate for which anyone might certify and announce such a prop. Remember that the major prop manufacturers are primarily in the business of certified props for certified engines which qualify for single engine night and IFR flight. It has been done before; the Cessna 150 received a Clark-Y prop, which was regarded as a fairly new improvement, shortly before it was replaced by the Cessna 152. I am curious, but not holding my breath. Fair enough. Go for it, then let us know! -- Jim in NC |
#55
|
|||
|
|||
Why don't wings have dimples?
On Fri, 16 Jun 2006 00:40:30 -0400, "Morgans"
wrote: "Peter Dohm" wrote You're right. Then we could prove a lot one way or the other--especially if a little smoke was part of the system. There would still be the effects of scale and Reynolds number, which are supposed to be quite significant, but a lot could still be learned. At least it should be possible to either verify or deny the assertion that grooved or dimpled props produce a virtual "switch pitch" effect. Maybe next year. I would be willing to bet a month's salary that at *least* one of the big prop makers have done all of this kind of research. After all, these companies strive to eek out hundredths of a percent improval of propeller efficiency. Any takers? April Fools! (so I'm a little late, sue me! g) I'm too poor (and not enough of a gambler) to risk any of my salary, even if it is a "sure thing" bet! g Still my point stands. Me thinks that if these tricks have not shown up on your manufactured props, the gain is not significant enough to be worth the effort of incorporating them into the props. -- Jim in NC I'm sure dimples would work on propellers my plane definatly flies slower after I clean the bugs off the prop and bugs are just dimples in reverse. |
#56
|
|||
|
|||
Why don't wings have dimples?
Drew Dalgleish wrote:
On Fri, 16 Jun 2006 00:40:30 -0400, "Morgans" wrote: "Peter Dohm" wrote You're right. Then we could prove a lot one way or the other--especially if a little smoke was part of the system. There would still be the effects of scale and Reynolds number, which are supposed to be quite significant, but a lot could still be learned. At least it should be possible to either verify or deny the assertion that grooved or dimpled props produce a virtual "switch pitch" effect. Maybe next year. I would be willing to bet a month's salary that at *least* one of the big prop makers have done all of this kind of research. After all, these companies strive to eek out hundredths of a percent improval of propeller efficiency. Any takers? April Fools! (so I'm a little late, sue me! g) I'm too poor (and not enough of a gambler) to risk any of my salary, even if it is a "sure thing" bet! g Still my point stands. Me thinks that if these tricks have not shown up on your manufactured props, the gain is not significant enough to be worth the effort of incorporating them into the props. -- Jim in NC I'm sure dimples would work on propellers my plane definatly flies slower after I clean the bugs off the prop and bugs are just dimples in reverse. Well, let's postulate something ... A LONG, slow turnng propeller, pretty wide chord. Tips are turning about the same sped a golf ball flies (get it?) Dimpling the prop might produce amazing results. But the prop on a 172? Probably not a lot of help because the velocity is way above RN(crit). Richard |
#57
|
|||
|
|||
Why don't wings have dimples?
karel wrote:
because dimples don't have wings either? Mary sez it's all the work of Lift Demons, That's her story, and she's sticking to it. |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
VP-II wings available in Oregon, USA (Or, "How I was coconuted...") | Roberto Waltman | Home Built | 2 | October 29th 04 04:21 PM |
Charging for Wings safety seminar? | Marty Shapiro | Piloting | 19 | June 23rd 04 05:28 PM |
Double covering fabric covered wings | [email protected] | Home Built | 9 | May 9th 04 08:39 PM |
Stolen "Champ" wings located...from 23,000 feet!! | Tom Pappano | Piloting | 17 | December 15th 03 01:24 PM |
Wings from "Champ" stolen in Oklahoma after emergency landing | Tom Pappano | Piloting | 1 | December 7th 03 05:02 AM |