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Old Mar 20, 2012, 10:01 PM
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Originally Posted by dave1993 View Post
regarding the airfoil, is it possible you have not seen a single one of the photos ive put up here and scattered just about everywhere else on rcgroups? like just a few posts back for example?
Many old guys call those Trainer airfoils. When you get your big boy pants you can start using airfoils that don't have a ton of drag if you try to go fast.
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Old Mar 20, 2012, 10:08 PM
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Originally Posted by aeronaut999 View Post
Yes I'm aware that by the aerodynamicist's system of specifying airfoils by the shape of the camber line and the variation of thickness along the camber line, it's an arbitrary or accidental distinction as to whether the undersurface happens to have any undercamber or not.
Steve
That's what I was about to say! Thanks for the background, I'm not very familiar with hang gliders.
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Old Mar 20, 2012, 10:16 PM
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Originally Posted by Steve Anderson View Post
Many old guys call those Trainer airfoils. When you get your big boy pants you can start using airfoils that don't have a ton of drag if you try to go fast.
sorry gramps. if getting "big boy pants" means spending a grand a month on the hobby and needing to join ama for fields big enough to fly that fast, ill pass.

for last few years ive been happy to experiment with wings and power systems and float around nearby soccer fields with my deltas and 4' foamies. no inclination to grow up and end up like some of the guys i see who dont seem to be having any fun at all. just bragging about how much they spent and recollecting "good old days". nope, not for me.
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Old Mar 20, 2012, 10:36 PM
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"Big boy pants"-- made me laugh. Time to let this thread simmer for a few more days, see ya in a while. Steve
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Old Mar 21, 2012, 09:47 AM
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Originally Posted by dave1993 View Post
sorry gramps. if getting "big boy pants" means spending a grand a month on the hobby and needing to join ama for fields big enough to fly that fast, ill pass.

for last few years ive been happy to experiment with wings and power systems and float around nearby soccer fields with my deltas and 4' foamies. no inclination to grow up and end up like some of the guys i see who dont seem to be having any fun at all. just bragging about how much they spent and recollecting "good old days". nope, not for me.
No thatís not what it means. A little time figuring out why you owe Don Stackhouse an apology and the reason you need to insult people who disagree with you may help you figure what it means.
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Old Mar 21, 2012, 10:28 AM
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Originally Posted by dave1993 View Post
maybe its just me but im less impressed by aerodynamic theory than real world obesrvations.
Maybe this thread ought to just park until Dave shares those real-world observations he is always talking about-- don't know why he won't share those pressure readings from the top/ bottom of the wing of his park flyer that show how the high pressure on the bottom surface is the dominant effect contributing to the lift force on the airfoil? Not that that has anything to do with whether lift involves a downwash (which it does), but still, it seems to be one of his favorite topics, so why won't he share the evidence with us? Maybe-- it's because that would belong in the "modelling science" forum? Which this is not...

This is the "bash academic theory" / "extol the virtues of my favorite branch of RC flying and bash the rest" / "make generalized physic arguments about lift based on quirky things I think I'm seeing in slow flying aircraft" / "misrepresent my opponent's statements/ predictions" / "engage in illogical arguments" / "argue against the existence of logic" / "accuse everyone else of being a religious nut case" forum.

You mentioned playing with cooling fans in your last post.

We all know that a propeller makes a strong propwash behind, but not in front of, the propeller disk, in terms of the velocity of the flow at any given point. (I.e. the outflow is much more concentrated than the inflow.)

So, is this yet another manifestation of the idea that an airfoil has a stronger high-pressure area on the bottom and only a weaker low-pressure area on top? If the low pressure on top were stronger than the high pressure on the bottom, then the "sucking" propwash in front of the prop would be stronger than the "blowing" propwash behind the prop? Even if the prop is operating at a very high airspeed and is using an airfoil whose pressure distribution is well known to be the opposite (low-pressure on top of the airfoil is stronger than high-pressure on bottom)? That would pretty much be the logical extension of the positions you've taken over the last few days.

Real world this, real world that, we would be all ears if you would tell us something from the real world that pertained in any real way to what we've been talking about. Rather than saying "you'd get all this if you knew about thin films, so go google thin films".

This thread is long overdue for being put out to pasture...

On the other hand maybe it ought to remain as a special preserve for this kind of twisted discussion-- sort an exhibit, a museum, a zoo?

Steve
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Old Mar 21, 2012, 11:03 AM
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No that’s not what it means. A little time figuring out why you owe Don Stackhouse an apology
your post dont sound like trying to elicit an apology. unless you consider don an airfoil type:

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When you get your big boy pants you can start using airfoils that don't have a ton of drag if you try to go fast.
if you read those original posts and my reply youll see i was strictly referring to ultralights and you and dons infatuation with speed dont apply there. if necessary i can go into more detail on legal issue involving speed limits of part 103.

i agree there was a considerable amount of "twisting" going on and an apology might be due. but not to the person you suggest. try reading those posts and links again. i suspect that in view of what appear to be romantic involvements this might not happen.
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Old Mar 21, 2012, 11:53 AM
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Originally Posted by aeronaut999 View Post
Not that that has anything to do with whether lift involves a downwash (which it does), but still, it seems to be one of his favorite topics, so why won't he share the evidence with us? Maybe-- it's because that would belong in the "modelling science" forum? Which this is not...
well... since op and anyone else sharing his viewpoint were simply run out of town then it must be open season topic wise. in any case understandable why those who dont read and/or understand posts might think they are ot.

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Originally Posted by aeronaut999 View Post
This is the "bash academic theory" / "extol the virtues of my favorite branch of RC flying and bash the rest" / "make generalized physic arguments about lift based on quirky things I think I'm seeing in slow flying aircraft" / "misrepresent my opponent's statements/ predictions" / "engage in illogical arguments" / "argue against the existence of logic" / "accuse everyone else of being a religious nut case" forum.
lol! cant argue with that. pretty obvious a few guys here do NOT like it when their pet theories are challenged.

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Originally Posted by aeronaut999 View Post
You mentioned playing with cooling fans in your last post. We all know that a propeller makes a strong propwash behind, but not in front of, the propeller disk. So, is this yet another manifestation of the idea that an airfoil has a stronger high-pressure area on the bottom and only a weaker low-pressure area on top?
its not so much that one is stronger than the other but as i said before:

"mostly im not convinced low pressure above is as effective as air from below."

at least in term of lift. i repeat this for any interested parties who actually do read the posts here.

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Originally Posted by aeronaut999 View Post
Real world this, real world that, we would be all ears if you would tell us something from the real world that pertained in any real way to what we've been talking about.
how many actual experiments have you conducted and posted since the start of this thread. you know, ones with photos and description of results. in fact going though your post history not many since joining this forum. let me count... well.. there must have been at least ONE. no?

going through a persons forum history can be very telling. browsing list of attachments in their blog too. imo some guys here would be much happier in ltup where most have never even seen an rc model let alone built or flown one.

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Originally Posted by aeronaut999 View Post
Rather than saying "you'd get all this if you knew about thin films, so go google thin films".
thin film technology is fasicnating and i have played with vacuum deposition at the school but i dont recall ever bringing that up here. maybe you confuse it with my response to dpates query about single surface wings. my description of os film was quite appropriate if somewhat unappreciated. maybe more so for those with actual sense of humor too.

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This thread is long overdue for being put out to pasture... On the other hand maybe it ought to remain as a special preserve for this kind of twisted discussion-- sort an exhibit, a museum, a zoo?
lol! like i said...
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Old Mar 21, 2012, 12:39 PM
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Originally Posted by dave1993 View Post
your post dont sound like trying to elicit an apology.
An apology is not what I was trying to elicit with that comment, you are correct.

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Originally Posted by dave1993 View Post
unless you consider don an airfoil type:
I think Don is a human, not an airfoil.

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Originally Posted by dave1993 View Post
if you read those original posts and my reply youll see i was strictly referring to ultralights and you and dons infatuation with speed dont apply there. if necessary i can go into more detail on legal issue involving speed limits of part 103.

i agree there was a considerable amount of "twisting" going on and an apology might be due. but not to the person you suggest. try reading those posts and links again. i suspect that in view of what appear to be romantic involvements this might not happen.
I read some of your interaction with Don and also what you have written here. I don't need to re-read it.

You really like throwing out accusations about people. You also like to have everyone go back and do this and that, but when you're called out on something you said, you don't do any work. How is that list of Newtonian deniers coming?


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i suspect that in view of what appear to be romantic involvements this might not happen.
Why would you suspect that? Are you and Tim having one?
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Old Jan 11, 2014, 01:04 PM
Lift is cheap - Drag sucks
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Backwash

I'm curious what impact the B-36 would have on the downwash discussion.

It seems that six pusher props and four under wing jets would redirect the flow sufficiently to destroy lift - if indeed downwash is the lift generator rather than a residual effect of the wing having passed.

Tom
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Old Jan 13, 2014, 06:22 PM
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Unlike a conventional airplane where the lift in level flight is 49.9% due to downwash and 50.1% due to the Bernoulli effect, the lift on a pusher configuration in level flight is 36% due to downwash, 50.1% due to the Bernoulli effect, and 31.9% due to magic.
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Old Jan 13, 2014, 06:28 PM
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Even worse in the Northrop YB-35 flying wing (http://en.wikipedia.org/wiki/Northrop_YB-35), with the reflexed trailing edge and the props pushing air upward! The amount of magic goes up to at least 47%!
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Old Jan 13, 2014, 06:35 PM
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But with the right twist distribution on a jet-powered swept flying wing like the later YB-49, you can get the lift-due-to-magic down into the 38-42% range.
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Old Jan 13, 2014, 09:47 PM
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Quote:
Originally Posted by Tom Harper View Post
I'm curious what impact the B-36 would have on the downwash discussion.

It seems that six pusher props and four under wing jets would redirect the flow sufficiently to destroy lift - if indeed downwash is the lift generator rather than a residual effect of the wing having passed.

Tom
Bernoulli is European and so has nothing to do with the US air force.
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Old Jan 14, 2014, 02:56 AM
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There is no such thing as magic. Everything can be explained by simple physics. Since the upper part of the wing is further away from the earth's gravitational center than the lower part, it is more likely for air molecules travelling along the upper side to tunnel through the gravitational potential barrier, causing a lower pressure due to the lack of molecules.
Another effect for high speeds faster than approximately 2*Pi/2*s0 is the relativistic Lorentz contraction for the faster upper air molecules, creating more room for low pressure air on the upper side, increasing suction.
Also, it is common practice in aircraft construction to build the lower side of the wing from a lighter material than the upper side and using the resulting buoyancy of the wing within itself to support lift. Early aviation pioneers even took this to an extreme by not using any lower surface at all, creating enough bouyancy to even fly at such low speeds.
However it is still a mystery to scientists how planes can fly in Australia.
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