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General control line discussion => Open Forum => Topic started by: Matt Colan on July 24, 2012, 11:45:07 PM
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A couple weeks ago there was a thread on gyroscopic procession and there was mention of Randy Smith flying a Magnum with contra-rotating props. I found the video I had that Windy recorded from the early 90s at the NATS where Randy flew it, and decided to post it on Youtube.
Rather than cut and splice the footage where only Randy's Magnum was flying, I just let the video run, and there's a couple neat outakes in the video also. Bill Rich spelt out Tactor Stunt on the nose of his SV-11 instead of Tractor Stunt, Lew McFarland was taxiing out to take off in his T-34, and Bill Simons was having a conversation with Allen Brickhaus.
There's a lot of great stuff in this video, I have Paul Walker flying a Lubbock, Windy with his 20 point green cardinal flying, and many other cool flights. Over the next few days, I'll see if I can post a few of them.
Anyway, here's the video. H^^
http://www.youtube.com/watch?v=yz3zyDXStOU&feature=youtu.be
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Wow! The howl of that prop is unbelievable!
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Very cool. As a side note, makes you appreciate the AMA site we have the Nats at now.
James
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The sound of that prop was incredible!!!! Dubbed the 'Swiss Army Prop' ~^
The motor was very stout also!
Thanks
Jim
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My impression from the starting sequence is that the rear prop was freewheeling, not being driven. Anyone have better info?
Contra-rotating electrical systems are now readily available. It might be worth looking into.
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My impression from the starting sequence is that the rear prop was freewheeling, not being driven. Anyone have better info?
Contra-rotating electrical systems are now readily available. It might be worth looking into.
Its friction or fluid drive. If you think it does nothing watch when it stops and think of sticking your finger in it.
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Sounds Amazing!
Martin
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Its friction or fluid drive. If you think it does nothing watch when it stops and think of sticking your finger in it.
Yep, since the spinning of the weight in the opposite direction is what is offsetting the procession then you don't need that prop to be a driving prop that is grabbing air and moving the plane forward as well. The front prop is moving the plane. The wash from it is activating and driving the second prop due to its opposite pitch and camber. That spinning prop is counter the procession effect from the drive prop. Very cool.
The newer electric ones seem to have both props being used as accelerating props. Each prop powered by a separate engine. pretty cool stuff for sure.
But as someone noted on the other thread the newer radios can be programmed to counter procession so the extra advantage in RC is probably greatly reduced.
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I suspect we'll see contra's in CLPA soon. I have seen more F3A stuff in CLPA at this years Nats then I can believe. Vortex generators, (that is there thing) canalizers, etc. The tip vortice controllers that are common on these ships will probably show up also. Contras such juice like crazy but, we may have the advantage here in that are prop diameters won't anything close to what they use.
I still question the value of a lot of this stuff for us because, we fly at half the speed they do. Most of what they developed benefits them because, their ships are big enough and their velocities high enough, that the extra control these devices really provide measurable value. That said, it would be certainly fascinating to see.
I should be obvious by now, based on so many of my posts that I am absolutely fascinated by F3A ships. Their smoking hot looks, the sophisticated aerodynamics, killer powerplants, cutting edge use of materials technology, and mind boggling complex radios keep me constantly interested. Now that our Nats is over, I am carefully tracking F3A, to see what’s up. I specifically want to see if the new YS 175 Gas motor, is gaining any traction here in the states-I doubt it.
I suspect it may also be like F3A in that a guy that’s just plain really good, with a good simple setup and a reliable I.C. will still be able punch through for the win, such as Orestes Hernandez and Doug Moon etc.
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My impression from the starting sequence is that the rear prop was freewheeling, not being driven. Anyone have better info?
Contra-rotating electrical systems are now readily available. It might be worth looking into.
Hi Larry
Your impression is wrong, the system was a fluid drive system just like any car is driven by with an automatic trans.
The rear prop will take you finger off if you stick it in it when running, the ...ONLY... time it is freewheeling is when the engine stops
This has been explained here as late as a couple of weeks ago :-)
Regards
Randy
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Actually, with all the enthusiasm I am hearing concerning the reverse rotation in electrics using pusher designed props and getting more tension with them, why consider contra rotating props - use the reverse to line tension advantage, especially at the top. Having said this, let me remind you that I have two wonderfully running PA's that I fully intend to wear out, and that will take me the rest of my life!
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Hi Will
Because the contra system work far better than pusher props ever could, it does things that a pusher, or any single prop cannot do
Regards
Randy
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I suspect we'll see contra's in CLPA soon. I have seen more F3A stuff in CLPA at this years Nats then I can believe. Vortex generators, (that is there thing) canalizers, etc. The tip vortice controllers that are common on these ships will probably show up also. Contras such juice like crazy but, we may have the advantage here in that are prop diameters won't anything close to what they use.
I still question the value of a lot of this stuff for us because, we fly at half the speed they do. Most of what they developed benefits them because, their ships are big enough and their velocities high enough, that the extra control these devices really provide measurable value. That said, it would be certainly fascinating to see.
I should be obvious by now, based on so many of my posts that I am absolutely fascinated by F3A ships. Their smoking hot looks, the sophisticated aerodynamics, killer powerplants, cutting edge use of materials technology, and mind boggling complex radios keep me constantly interested. Now that our Nats is over, I am carefully tracking F3A, to see what’s up. I specifically want to see if the new YS 175 Gas motor, is gaining any traction here in states-I doubt it.
I suspect it may also be like F3A in that a guy that’s just plain really good, with a good simple setup and a reliable I.C. will still be able punch through for the win, such as Orestes Hernandez and Doug Moon etc.
Hi Milt,
I actually would think that because we are flying at half the speed of the F3A, these devices like Vortex Generators and canalizers might help us out even more so. With the slower speed, it becomes more critical to keep constant flow over the wing and tail surfaces. Obviously I'm no engineer, but that's just my educated guess.
Just as you, I find all these neat trim features fascinating to read about and think about trying them out on a stunt ship. How does a Tip Vortice controller work, I've never heard of it.
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Hi Milt,
I actually would think that because we are flying at half the speed of the F3A, these devices like Vortex Generators and canalizers might help us out even more so. With the slower speed, it becomes more critical to keep constant flow over the wing and tail surfaces.....
BINGO!! Air molecules are small, really small. Our planes large enough to take advantage of such devices. Kenny said the canalizer on his plane made the vertical and over head performance better. His thought was that it cleaned the air as it hit the tail secion and vertical stab so it was more effective.
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How does a Tip Vortice controller work, I've never heard of it.
I didn't respond right away because I went hunting for pictures so you can see it. If you study your "Fanchers" which you should, you'll know that there are dirty deeds being done cheap at the wingtips. Tip vortice controllers for these guys, help them to control these evil beings, thereby allowing to see a bit more effective lift.
They have a 2 meter limit. The controllers fool the wing into thinking it is bigger then it is, without actually being bigger. Because, they are seeing less losses at the wingtip. Now, they are not being used universally in F3A. Chip Hyde is a big fan of them,(he is a star-so he has pull). But some people swear by them.
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Okay Randy, since I'm running your PA's I gotta take your word as gospel, so thanks for the guidance. Now to try and find a combination of desire to fly and cooler weather so i can burn some fuel! (I've done two whole patterns this year!) I feel a little burned out because of flying mostly alone. Whine, snivel, whine. :-\ :-\
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HI Brother Will,
Don't complain! You have flown at least twice as many patterns this year than I have! ;D
Bill
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Okay Randy, since I'm running your PA's I gotta take your word as gospel, so thanks for the guidance. Now to try and find a combination of desire to fly and cooler weather so i can burn some fuel! (I've done two whole patterns this year!) I feel a little burned out because of flying mostly alone. Whine, snivel, whine. :-\ :-\
That whine.. snivel ....will dry up really fast with some more flights, I may get up to see and fly with you guys soon :-)
Randy
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I didn't respond right away because I went hunting for pictures so you can see it. If you study your "Fanchers" which you should, you'll know that there are dirty deeds being done cheap at the wingtips. Tip vortice controllers for these guys, help them to control these evil beings, thereby allowing to see a bit more effective lift.
They have a 2 meter limit. The controllers fool the wing into thinking it is bigger then it is, without actually being bigger. Because, they are seeing less losses at the wingtip. Now, they are not being used universally in F3A. Chip Hyde is a big fan of them,(he is a star-so he has pull). But some people swear by them.
I tried these things years ago. What I ran into was it would cause massive yaw. I messed around and found if I remove all of the TW the yaw was reduced greatly. But that shouldn’t be the case….TW is to offset the weight of the lines….odd this shouldn’t happen.
It would fly ok and I trimmed on it more. The line tension now is completely relying on these tip devices to hold the line tension. Why always fly in a side slip so they would work while the plane was at speed. But when you slow down a whole host of other issues show as line tension goes down.
I made them smaller and started added TW back in as I did. What I came up with the plane was a better flyer without these devices on the tips and ended up back at my original trim setup for optimal performance.
I do use these items on the stab/elevators. The thought is they will trap air that is slipping off the stab and force it over the elevator making it more effective and efficient.
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I do use these items on the stab/elevators. The thought is they will trap air that is slipping off the stab and force it over the elevator making it more effective and efficient.
That is one thing I would like to try on my Thundergazer when I get it flying. Since I'll have a removable tail, I could do my own tail experiments and see what I like better. Another layout I would like to try on the tail is PJ's swept back 1/4" hingeline, just to see what differences there are between the conventional tail that I've already made.
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Randy I launched that double prop plane for you quite a few times. St/.60 or was that the .64
Ed
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That is one thing I would like to try on my Thundergazer when I get it flying. Since I'll have a removable tail, I could do my own tail experiments and see what I like better. Another layout I would like to try on the tail is PJ's swept back 1/4" hingeline, just to see what differences there are between the conventional tail that I've already made.
There is an old Stunt News where David Fitzgerald did a very comprehensive study on stabilizer/elevator combinations. I highly recommend finding and reading it before you try your own testing.
As far as end plates, fences, or rudderlets, (excluding the drooped tips on STOL airplanes), I thought they were primarily to reduce spanwise flow on swept wings, and will not really have any effect on a straight (stunt plane) wing or tail?
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Randy I launched that double prop plane for you quite a few times. St/.60 or was that the .64
Ed
Hi Ed
Not a ST 60 , it was a homemade 64
Randy
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There is an old Stunt News where David Fitzgerald did a very comprehensive study on stabilizer/elevator combinations. I highly recommend finding and reading it before you try your own testing.
As far as end plates, fences, or rudderlets, (excluding the drooped tips on STOL airplanes), I thought they were primarily to reduce spanwise flow on swept wings, and will not really have any effect on a straight (stunt plane) wing or tail?
Hi Steve,
I've looked for the article in our SN archives, and sent Dave an email asking what issue it was in, but so far haven't heard back yet. What issue was it in?
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Hi Ed
Not a ST 60 , it was a homemade 64
Randy
Randy, was there any advantage to running dual plugs on that motor? Or was it just a fail safe method in case one of them crapped out?
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Hi Steve,
I've looked for the article in our SN archives, and sent Dave an email asking what issue it was in, but so far haven't heard back yet. What issue was it in?
March/April 1998 Stunt News has David's article on tail design.
Keith
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Randy, was there any advantage to running dual plugs on that motor? Or was it just a fail safe method in case one of them crapped out?
Hi Matt
Yes there is an advantage in any motor, especially a hi comp motor like that one, if you have a glow plug go bad ,the other one keeps the motor running just as it did without any flameout of burping or ratty inside manouvers.
Rarely happens, but it does happen on ocassions.
Randy
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As far as end plates, fences, or rudderlets, (excluding the drooped tips on STOL airplanes), I thought they were primarily to reduce spanwise flow on swept wings, and will not really have any effect on a straight (stunt plane) wing or tail?
Right it appears that would be the case. But we dont fly in a straight line. We are always side slipping around the circle. At least I am thinking that is the case. I have tried planes with removeable plates. A few flights with them and and few flights without them. There is an increase in the tail power with them. They really help on planes with smaller % tail sections. I had one model with an 18% tail section with tip plates and it was a monster. I flew it in expert for many years.
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That whine.. snivel ....will dry up really fast with some more flights, I may get up to see and fly with you guys soon :-)
Randy
Hey Randy, that would be super great!! Come on up! y1 #^
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Since we hit the subject of Contras AND tip plates here, I thought this picture would be appropriate. I think this thing is packing a Belt drive. Everything but the kitchen sink.
Check this out Doug
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Since we hit the subject of Contras AND tip plates here, I thought this picture would be appropriate. I think this thing is packing a Belt drive. Everything but the kitchen sink.
Check this out Doug
THAT IS BADASS!!!
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THAT IS BADASS!!!
Doug pay close attention to the props. Those are right on the cutting edge of tech. This thing is loaded baby!!
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Doug pay close attention to the props. Those are right on the cutting edge of tech. This thing is loaded baby!!
Way too much separation between the props
Randy
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March/April 1998 Stunt News has David's article on tail design.
Keith
Thanks Keith! I'll look for that issue of SN next time I get the chance H^^
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I hesitated to post this because, I sense we are on somewhat of a technology high right now here in stunt. But, if you followed my prior posts, you will know that I stated that, the contra drives in F3A were not turning into success at the contests level as much as expected.
The results are in F3A at the 2012 Nats and, none of the contra equipped ships were able to break into the top or, none of the top five winners were contra equipped. What was a big surprise to me, was to see the YS cracking the top 5 stateside. Brett Wickizer was the lone man holding up the I.C. banner for 3rd place.
There were 2 biplanes in the top five. Internationally, biplanes in F3A rock!! Since we seem to be going great guns for tech right now, maybe this is something one of you with advanced aero skills can explore and exploit for our uses. Or, pickup on John Millers work while he is recuperating.
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I had not seen that engine before - Heard about it yes.. - Looks awesome !
Another layout I would like to try on the tail is PJ's swept back 1/4" hingeline
.... I highly recommend finding and reading it before you try your own testing. "
That tail modification Matt is talking about is simply a further extension of Dave's Tail and said article. - I completely agree with everything in the article - It was the basis for this design.
Its almost an identical tail but the hingeline sweeps back 1/4 " - so the shape looks slightly different. I find improved tracking.
However - I dont think there is any universal gospel theory..
I tried Wing plates - and found similar to Doug moon - difficult to trim for - when it was in trim, didnt improve it any more. -
However
I also tried Stab Plates and found no improvement ( contray to many opposing opinions ).. This was done to one of my newer airfoiled swept back Tails. I have not tried it on Flat Stabs. I make mention of that because ALL of the Stab Plates I've ever seen on models have been Flat Stabs.
I dont know if thats co-incidence or not - If people run things make sure you can quantify the results. Back to back flights on and off .. Do you prefer or, or can you not tell ?
Only when there is a definitive improvement should one proceed.