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Old May 11, 2011, 05:18 PM
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I decided to send in the FDR to Eagle Tree for repair. It's gonna cost $50 plus shipping to them.
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Old May 11, 2011, 05:25 PM
Jack
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Originally Posted by maguro View Post
I decided to send in the FDR to Eagle Tree for repair. It's gonna cost $50 plus shipping to them.
For $58.99 plus $4.99 shipping you can buy a brand new V4 on eBay:

http://tinyurl.com/43dmhuy

Check his other auctions if you want the leaded one.

Jack
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Old May 11, 2011, 06:02 PM
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Jack,

Thanks for the info, but the ELogger is not the same as the Seagull Pro FDR. The FDR unit alone cost $270 from Hobby King (USA). It connects to all the sensors Eagle Tree makes, and transmits the data (via separate transmitter module) to a hand held receiver. That's how I know what the airspeed, altitude, battery current, etc. are while flying.

Roger
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Old May 11, 2011, 06:21 PM
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I'm uploading the data from todays flight in case anyone is interested in looking at it. I tried some slow passes and some full speed passes. I even did a stall. Try looking at the date and figuring out what was going on. I saved the data in zipped Microsoft Excel format. The data file has a lot of fields that have no sensor, or I was just not recording to save space in the FDR. The important fields in this file other than time (X Axis) are airspeed, and the electrical data.

Just an FYI, the data is recorded every 1/10 second. The airspeed varies a few mph up and down at just about every tick of the clock. I was holding the pitch steady. In many places I just let the model glide. It is amazing how much the airspeed, and other values vary when the model looks like it's flying smooth as silk. The winds were not too bad 5-10, but gusty, and changing in direction by as much as 120 degrees.

I need to video the flight tests, and then time sync the video with the FDR data. Unfortunately today my camera person was the person who held the receiver and told me the readings (my wife).

Let me know what you think of the data.

Roger
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Old May 11, 2011, 06:42 PM
Dreamer
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intersting..

I did a CFD project on a KF airfoil, my cad of the KF was very crude, because i wanted to simulate what people can build in their shops. the results weren't very good, lots of drag was showing. But CFD has its inaccuracies. if someone can give me a cross section of their actual physical airfoil and dimensions we could do a few AoA and speeds...

i can post our report for the project but its not very good...
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Old May 11, 2011, 07:30 PM
Jack
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Originally Posted by maguro View Post
Jack,

Thanks for the info, but the ELogger is not the same as the Seagull Pro FDR. The FDR unit alone cost $270 from Hobby King (USA). It connects to all the sensors Eagle Tree makes, and transmits the data (via separate transmitter module) to a hand held receiver. That's how I know what the airspeed, altitude, battery current, etc. are while flying.

Roger

OK, I knew that. I just didn't think it through. For some reason I thought you were tallking about a eLogger.

Jack
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Old May 12, 2011, 02:18 AM
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Quote:
Originally Posted by sketchillus View Post
intersting..

I did a CFD project on a KF airfoil, my cad of the KF was very crude, because i wanted to simulate what people can build in their shops. the results weren't very good, lots of drag was showing. But CFD has its inaccuracies. if someone can give me a cross section of their actual physical airfoil and dimensions we could do a few AoA and speeds...

i can post our report for the project but its not very good...
From what i understand (never having used high end CFD) the results can be highly inaccurate for flow regimes with separation, transition and turbulence such as you get at low re and that you will without doubt get with a stepped airfoil. There was some discussion on the problems of CFD when used for this type of analysis here: http://www.rcgroups.com/forums/showthread.php?t=1401717

Steve
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Old May 12, 2011, 12:37 PM
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sketchillus,

Here is a drawing of the test airfoil(s) as accurately as I can draw them. The front half is as close to an MH32 as I can make it. The Blue id thhe KFm2 airfoil that is the base for testing. The black Rectangle is the standard KFm3 strip. The red wedge is the new variation on the KFm3 with 3mm steps. The green is the wedge which approximates the rear of an MH32. This blue/green airfoil is what the others are being compared against. Any CFD data you can generate will be of great value. I'll do my best to relate your findings with what we get in testing. As Steve said, the steps may cause inaccuracies in the computations, but that does not keep them from being of value.

Roger
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Old May 15, 2011, 11:00 PM
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I would love to know what the people on the VortexCell2050 project have learned about the use of the trapped vortex. I can't imagine that they would be pursuing this idea if it wasn't going to be productive for them.

Anyone know how to find out more info?
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Old May 16, 2011, 02:02 AM
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I would love to know what the people on the VortexCell2050 project have learned about the use of the trapped vortex. I can't imagine that they would be pursuing this idea if it wasn't going to be productive for them.

Anyone know how to find out more info?

Dick,

The project report was completed and issued in 2008 (I've referenced this report before in this thread): http://ltces.dem.ist.utl.pt/lxlaser/...ers/11.3_4.pdf

Here's a quote from the Conclusions in the report (Section 5)
Quote:
From the showed results the following conclusions can be draw. Passive TVC (Trapped Vortex Cell) flow control is not able to control the flow separation. The vortex is not confined in the cavity and vortex shedding is present decreasing the aerodynamic characteristics of the original airfoil. Active TVC flow control is able to control the flow separation, for limited values of the blowing coefficient full reattachment has been obtained.[/U]
So what they found was that without 'active vortex control' it was impossible to trap a stable vortex in the step/cell. The vortex could not be prevented from shedding which degraded performance compared to the same airfoil without the step/cell.

By adding complex active suction/blowing of the step/cell (three suction nozzles and one blower in the cell itself) they were able to maintain a stable trapped vortex in certain conditions and this did show positive results.

The test results are discussed in more detail in the 'results and discussions' section (section 4). Attached is a PIV image taken from section 4 which clearly shows how the vortex step/cell results causes full separation of the airflow downstream (i.e. a stall). With active control of the vortex cell they were able to prevent this separation but they don't have a good image showing that in the report.

Steve
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Old May 16, 2011, 02:35 AM
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Steve...

Thank you very much for that info. I must have missed your previous post. I did not see the link before. I noticed that the shape of the airfoil in the picture differed from the other one they showed previously. But no doubt the results would be similar. My question is... was this result obtained through the use of a computer program? Or, through actual flight testing with a real aircraft?

– Dick
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Old May 16, 2011, 03:01 AM
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Originally Posted by Dickeroo View Post
Steve...

Thank you very much for that info. I must have missed your previous post. I did not see the link before. I noticed that the shape of the airfoil in the picture differed from the other one they showed previously. But no doubt the results would be similar. My question is... was this result obtained through the use of a computer program? Or, through actual flight testing with a real aircraft?

– Dick
Dick,
Testing was done in a wind tunnel. There are good photos of the tunnel used and the airfoil test rig contained in the report.

I think the difference in the shape of the vortex cell is because the initial image was purely a publicity photo and was untested. The 'back wall' featured on the vortex cell tested would be required to try to prevent the vortex from getting blown away 'downwind'. The active vortex control had air injected in the cell back wall and three suction points in the front wall which worked to kept the vortex pushed up tight against the front wall of the cell and prevented it getting sucked out and causing separation.

Steve
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Old May 16, 2011, 08:30 AM
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Thanks, Steve.

In the conclusion, I saw the line.... "These first experiments provided really encouraging result."

There are some test results I'm hoping to hear about from the University of Michigan one of these days. I'll let you know if I find anything out.

You, sir, are a wonderful resource.

Dick
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Old May 16, 2011, 08:50 AM
Lee
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Dick

I sometimes sense some frustration on your part.

I know you are hoping for great things with the step airfoils but different people running different tests are going to get the same results. Great things are happening with them but not in the way your imagined.

The KF airfoil steps will never replace the full cut airfoils. That has been obvious from the beginning but they do have a place in RC modeling. They have changed the hobby forever.

I would guess thousands to hundreds of thousands of planes have been cut using KF steps. Look at how many different designers are cutting your steps!!!! They are inexpensive and so lightweight that they have been a great improvement to the flatfoam planes that are so popular. They make it so a modeler with a razor blade and a flat sheet of foam can be a plane designer. There are designs that can be done with a KF step that are very difficult to do with the foam cutters and horribly expensive to do with molds. Some of the most original looking planes use the concept you came up with.

There have been millions of hits and thousands of posts on planes that are using the KF concept. These people believe and will continue to use the steps.

Thanks for your efforts to promote the design. I have been a loyal follower and have encouraged the use of KF airfoils on the bird planes and others and have encouraged others to use the steps on other flat foam designs.

You have a big following.

Lee

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Last edited by Lee; May 16, 2011 at 08:57 AM.
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Old May 16, 2011, 09:11 AM
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Thank you, Lee.

I am just grateful to have been able to have made a contribution to this great hobby. If nothing further develops, so be it. I have encountered some wonderful people on these threads. I love the creativity that they bring to the table. I consider myself a very lucky man to have played a part in this terrific endeavor. Using the step concept in the RC may bring many more people into the hobby and it will give them a chance to experiment and learn from each other as well. I truly believe that this is the greatest group of people you could find anywhere. I'm content with that.

Dick
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