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BJCraft Episode

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Old 03-20-2012, 02:15 PM
  #51
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Default RE: BJCraft Episode


Quote:
ORIGINAL: Doug Cronkhite

SFGs are intended to provide more yaw lifting force I'd guess. The problem I see is that it isn't free. You lose yaw stability because of the proximity to the aerodynamic center of the airplane. Today's fuselages are big enough that I just don't see a need for the SFGs in the sizes most people are using. In order to get any real effective use out of the SFGs they'd have to be MUCH larger.
The SFG's do limit the spanwise flow over the tip of the aileron so increased aileron effectiveness can result....

but as you say... there is a price to pay.....
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Old 06-12-2012, 06:34 AM
  #52
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Default RE: BJCraft Episode

I see that B.J. Park has made progress on the Episode. He's continued to develop and test the airframe and it looks like he is about ready to release it to production.

Details are here: http://rcone.kr/board/index.html?id=bjair1&no=92

First and foremost, he gives credit for the design inspiration to CPLR. B.J. says he was really impressed by the Axiome family of airframes and used some of the ideas to help his initial Episode design concept.

The evolution of his Episode design has resulted in this version. Notably, he dropped the flaired wing tips because they were adding tip weight, he shrunk the size of the canalyzer, he went with the DTFS style wing, and he has added fences on his horizontal stabs.

Here are a few pics of the progress:
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Old 06-12-2012, 07:01 AM
  #53
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Default RE: BJCraft Episode

I got a note from Mr. Park last night and he said they have a target of the end of the month to start production on the Episode. No price estimate yet but we will have some as soon as they are available.
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Old 06-12-2012, 09:36 AM
  #54
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Default RE: BJCraft Episode

I'm seeing the stab fences a lot on newer designs, which to me says people are underestimating the vertical stab/rudder surface area needed to deal with the increase in fuselage volume ahead of the center of pressure. Love the look of the Episode now, and I can understand BJ not wanting to make new molds for the fuse. The stab fences work just fine to correct this issue.
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Old 06-12-2012, 12:03 PM
  #55
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Default RE: BJCraft Episode

I have the stab fences on my Onas now and they have really improved that model. I think they work even better then just making the fin bigger as they work in cleaner air then the fin does. I'm just about ready to start flying my Nuance with the Contra unit and I expect I will be adding them to it.
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Old 06-12-2012, 12:28 PM
  #56
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Default RE: BJCraft Episode

Like the design (very interesting),..good looking bird. I was going to go with the Nuance, but I'll wait and see how this pans' out.

bholsten
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Old 06-12-2012, 12:36 PM
  #57
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Default RE: BJCraft Episode

Wouldn't making the fin bigger increase the crabbing in a crosswind? This way is more effective because it actually doesn't increase the side area.
I hadstab fenceson my Spark last year and loved what they did for the plane. It tracked better with them on. I don't need them on my Nuance.
Question is a nose heavy plane more likely to benefit from having these? Thanks, Mike Mueller
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Old 06-12-2012, 12:41 PM
  #58
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Default RE: BJCraft Episode

He's optimizing this for FAI F type maneuvers which are heavy on the knife edge loops, rollers, etc. In my opinion it will be hard to beat the Nuance in patterns like Masters and FAI P13 because it really does well at those types of smooth and precise patterns.
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Old 06-12-2012, 01:56 PM
  #59
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Default RE: BJCraft Episode

According to his site on the bottom of the page, the price point appears to be $2200 USD....and I was just about to buy a Nuance.
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Old 06-12-2012, 02:14 PM
  #60
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Default RE: BJCraft Episode

No such thing as crabbing in a crosswind due to vertical fin area or amount of side area. The amount a model has to point in to the wind depends on what the crosswind component is compared to the airplanes speed. Slower airplane speed there is more angle, faster there is less. It's just a myth that more side area is bad in a crosswind.
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Old 06-13-2012, 04:51 AM
  #61
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Default RE: BJCraft Episode


Quote:
ORIGINAL: TonyF

No such thing as crabbing in a crosswind due to vertical fin area or amount of side area. The amount a model has to point in to the wind depends on what the crosswind component is compared to the airplanes speed. Slower airplane speed there is more angle, faster there is less. It's just a myth that more side area is bad in a crosswind.
Tony are you saying that more side area aft of the CG has no effect in how the plane tracks in a crosswind versus less area? I'm listening and appreciate the feedback. Thanks, Mike
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Old 06-13-2012, 05:43 AM
  #62
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Default RE: BJCraft Episode

Yep, that's what I'm saying. The airplane has to be yaw stable, which means the tail wants to stay in the back. If it's not yaw stable, the tail will wander all around and it will look and feel terrible. When it's flying, the airplane only feels it's relative wind which is it's velocity through the air. It does not feel the crosswind, except when that crosswind might change, as in a gust or a wind shear at different altitudes. Then it will only feel it long enough to align itself with the relative wind, which is a very short time period. Every airplane that is yaw stable, and that should be every good pattern model, will react the same. Doesn't matter if it's a pencil fuse like a Typhoon or a Nuance.

Alpha is the term used to describe angle of attack. Beta is the term used to describe angle of yaw. If your model is yaw stable it is always trying to fly at zero beta. You can kind of test just how stable your model is in beta by doing a quick rudder pulse while it flies overhead. Just blip the rudder and let go. The model should yaw with the rudder pulse then after you let go return quickly to zero beta. A model that is lacking yaw stability will oscillate a few times before returning to zero beta. You'll see that as a tail wiggle, which in pattern is bad. Also, a model that is lacking yaw stability will be very hard to "point". It will be unreliable on where it is going when you come out of a maneuver. Probably what you didn't like about the Onas when you had one. Which is why when I went to the Contra on the Onas I added the triangles on the rudder and a ventral and now the stab fences. They make the model point better coming out of a maneuver.

In a crosswind, to draw a straight line on the ground, which is what we are doing when we fly a track parallel to the runway, the model must fly on a heading that is not parallel to the runway, but one that is pointed slightly in to the wind. The amount of that angle is determined only by the speed of the model in relation to the crosswind component. The faster the model, the less the angle between the model's heading and the ground track. The slower, the greater that angle must be. Nothing to do with fin area or total side area.

I'm sure in trying to keep it simple I've upset some aero engineer out there. I'm not an aero engineer, but I did stay at a Holiday Inn!
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Old 06-13-2012, 06:36 AM
  #63
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Default RE: BJCraft Episode

Tony, your description of yaw stability when exiting manoeuvres ( the plane would point anywhere but straight) is exactly what my Nuance with contra drive was doing until I added the triangular edge to the rudder. I effectively doubled the width of the rudder from 16 mm to 31 mm. Now it is very stable in all axes.
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Old 06-13-2012, 06:47 AM
  #64
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Default RE: BJCraft Episode

Pippy, I'm going to fly my Nuance with the Contra tomorrow winds permitting. Widening the rudder adds drag and drag is also a way to keep the tail steady. But I'm not a big fan of unnecessary drag, especially with the speed control we have with the Contra. I suggest adding the stab fences. Use the laser cut piece that comes with the kit to set the elevator neutral as a starting template to make the fences. The set I have on the Onas now is made with 3 layers of 1/32" balsa laminated in a cross grain for stiffness. Keep the edges sharp, don't round them. I put the ones on my Onas out on the stab at 1/2 span, but I don't think where you put them is terribly important. Just make sure they are aligned with the centerline of the model. On the first set I put on the Onas I put some tape down on the stab first so I could remove them easily if I didn't like them. Once I knew I wanted them permanently I marked where they would go on the stab then used a pin to make a bunch of holes in the covering and thin CA'd them on. I think you will like them if you give them a try.

BTW, Andrew Jesky sent me pics about a year ago showing the stab fences on one of his models. Then I saw them on Dave Snow's Spark at the Nats last year. So that's where I got the idea.
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Old 06-13-2012, 07:09 AM
  #65
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Default RE: BJCraft Episode


Quote:
ORIGINAL: TonyF

Yep, that's what I'm saying. The airplane has to be yaw stable, which means the tail wants to stay in the back. If it's not yaw stable, the tail will wander all around and it will look and feel terrible. When it's flying, the airplane only feels it's relative wind which is it's velocity through the air. It does not feel the crosswind, except when that crosswind might change, as in a gust or a wind shear at different altitudes. Then it will only feel it long enough to align itself with the relative wind, which is a very short time period. Every airplane that is yaw stable, and that should be every good pattern model, will react the same. Doesn't matter if it's a pencil fuse like a Typhoon or a Nuance.

Alpha is the term used to describe angle of attack. Beta is the term used to describe angle of yaw. If your model is yaw stable it is always trying to fly at zero beta. You can kind of test just how stable your model is in beta by doing a quick rudder pulse while it flies overhead. Just blip the rudder and let go. The model should yaw with the rudder pulse then after you let go return quickly to zero beta. A model that is lacking yaw stability will oscillate a few times before returning to zero beta. You'll see that as a tail wiggle, which in pattern is bad. Also, a model that is lacking yaw stability will be very hard to "point". It will be unreliable on where it is going when you come out of a maneuver. Probably what you didn't like about the Onas when you had one. Which is why when I went to the Contra on the Onas I added the triangles on the rudder and a ventral and now the stab fences. They make the model point better coming out of a maneuver.

In a crosswind, to draw a straight line on the ground, which is what we are doing when we fly a track parallel to the runway, the model must fly on a heading that is not parallel to the runway, but one that is pointed slightly in to the wind. The amount of that angle is determined only by the speed of the model in relation to the crosswind component. The faster the model, the less the angle between the model's heading and the ground track. The slower, the greater that angle must be. Nothing to do with fin area or total side area.

I'm sure in trying to keep it simple I've upset some aero engineer out there. I'm not an aero engineer, but I did stay at a Holiday Inn!
I stayed at the Days Inn in Muncie. What a hole!!! Based on that I can use some advise. Great stuff Tony I love the layman's explanation. And yes that's exactllywhat I didn't like about the Onas. One more question. Does a tail heavy planehave more yaw stability than a nose heavy plane?Mike
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Old 06-13-2012, 08:12 AM
  #66
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Default RE: BJCraft Episode

Super 8 for me in Muncie!

No, it does not. Moving the CG forward improves both pitch and yaw stability. Moving it aft reduces it. I suspect you had the CG too far aft on the Onas. Mine is quite forward and it flew a lot better. It's really flying well now with the Contra and the stab fences. Wish I had done this work before last year's Nats!
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Old 06-13-2012, 08:20 AM
  #67
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Default RE: BJCraft Episode

Tony, thanks for that advice but I a comp this weekend and then 2 international events ( includes European champs for Ireland ) within a month so I will leave well alone for the moment. If it ain't broke as they say. I think it may be a project for next season. I would like to hear how your Nuance with that set up goes.
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Old 06-13-2012, 09:39 AM
  #68
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Default RE: BJCraft Episode


Quote:
ORIGINAL: TonyF

I have the stab fences on my Onas now and they have really improved that model. I think they work even better then just making the fin bigger as they work in cleaner air then the fin does. I'm just about ready to start flying my Nuance with the Contra unit and I expect I will be adding them to it.
I can see that, especially if you can get the fences installed outside of spiral slipstream. Of course, with the Contra, that shouldn't be an issue at all. One thing I've never been able to determine is if the contra system eliminates the spiral slipstream, or just has the same pulses in opposite rotation, thereby cancelling them out.
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Old 06-13-2012, 10:10 AM
  #69
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Default RE: BJCraft Episode

I have talked to Brenner about doing testing with the Contra. One thing I'd like to do is tuft one side of the fuse, put a micro recording camera out on the wing and see what the flow is actually doing. If you could run one on a stand and do some smoke testing you might also get the answer. But actual in-flight video would be neat.

pippy, good luck at the comps! I will post my experience with the Nuance as it develops.
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Old 07-31-2012, 01:21 AM
  #70
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Default RE: BJCraft Episode

Hi guys

Just went in to BJ blog and find a new update for the Episode.

It looks outstanding!

http://rcone.kr/board/index.html?id=bjair1&no=100
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Old 07-31-2012, 02:47 AM
  #71
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Default RE: BJCraft Episode

I WANT ONE,..or TWO!!

Been patiently waiting for the finished product,..gonn'a have to visit the F3A Unlimited warehouse and see it person when they arrive.

Chris,..can I fly it?

bholsten
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Old 07-31-2012, 12:50 PM
  #72
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Default RE: BJCraft Episode

Wow. That color scheme hurts my eyes.
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Old 08-01-2012, 10:55 AM
  #73
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Default RE: BJCraft Episode

Beautiful!!!
Looks like there will be a "contra drive fuse"
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Old 08-04-2012, 10:04 PM
  #74
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Default RE: BJCraft Episode

I like the color scheme minus the yellow. Maybe that will be the option color. The plane looks awesome! Glad to see BJ Craft working on new things. The don't seem to be scared to try anything to get a good flying plane.

Chris
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Old 08-05-2012, 12:09 PM
  #75
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Default RE: BJCraft Episode

Tony, could you post a photo of the stab fences you have installed please.
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