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BJCraft Episode

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Old 11-14-2011, 01:08 AM
  #1
bondtasha
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Default BJCraft Episode

Following on from the Nuance and the Prolog this new development looks pretty special to say the least

http://rcone.kr/board/index.html?id=bjair1&no=66
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Old 11-14-2011, 05:33 AM
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Default RE: BJCraft Episode

To whom it may concern: I've waited patiently for this opportunity to address two areas of concern that I've wrestled with for some time. First, if I have offended anyone, I apologize. Second, it is truly time for change and yes, that includes my contributions to RCU. I sincerely wish all of you the best, God's speed and a safe environment to enjoy this wonderful area of the hobby. Thanks for your patience, Everette
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Old 11-14-2011, 06:30 AM
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Default RE: BJCraft Episode

Looks interesting to me.. Glad to see BJCraft working hard to bring us some good fairly priced planes to the market!

Chris
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Old 11-14-2011, 06:44 AM
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Quote:
ORIGINAL: patternflyer1

Looks interesting to me.. Glad to see BJCraft working hard to bring us some good fairly priced planes to the market!

Chris
Yes, it does look interesting.

And it makes me wonder about the need for/benefit from both winglets and a canalizer.What are the effects from the winglets and how do theydiffer from SFGs/wing fences in terms of flightcharacteristics? Is BJCraft working off a theory or is this a creative case of trail-n-error? Nonetheless - good stuff! It isnice to see folks taking ideas/concepts and moving forward with them.
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Old 11-14-2011, 07:54 AM
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Default RE: BJCraft Episode

I find the evoulution of pattern planes to be facinating. Just when you couldn't imagine something new being added to a 2 meter box someone thinks of one. Mike
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Old 11-14-2011, 09:19 AM
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Default RE: BJCraft Episode

I beleive the curved tips the plane to be more stable with the wind, it also may help with rudder sensitivity around center. My 02 cents
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Old 11-14-2011, 11:15 AM
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Default RE: BJCraft Episode

The problem with the winglets is they'll increase effective dihedral on the airplane when upright. I think it's interesting to see the developments, but a lot of this DOES feel very much like trial and error as opposed to engineering a solution to a problem.
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Old 11-14-2011, 11:39 AM
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Default RE: BJCraft Episode

Actually Boeing 737s use similar winglets to save energy. The ones shown on RCONE are unproportionally large.
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Old 11-14-2011, 11:46 AM
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Quote:
ORIGINAL: nonstoprc

Actually Boeing 737s use similar winglets to save energy. The ones shown on RCONE are unproportionally large.
Sure.. but 737s don't spend much time upside down, spinning, or any other aerobatic maneuvers for that matter. As I've said, I don't follow the problem they're trying to solve with the winglets.
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Old 11-14-2011, 12:38 PM
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Default RE: BJCraft Episode

Just a food for thought...

A few weeks ago, Darin Peirce was flying his Peridot with the fancy wing tips. One fell off in the air. The wing with the remaining tip pitched up pretty noticeably. Darin landed it without incident but it was interesting to note what effect it had.

Guy
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Old 11-14-2011, 02:32 PM
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Default RE: BJCraft Episode


Quote:
ORIGINAL: Doug Cronkhite


Quote:
ORIGINAL: nonstoprc

Actually Boeing 737s use similar winglets to save energy. The ones shown on RCONE are unproportionally large.
Sure.. but 737s don't spend much time upside down, spinning, or any other aerobatic maneuvers for that matter. As I've said, I don't follow the problem they're trying to solve with the winglets.
Correct me if I'm wrong, Doug.

My thought is that they are looking for a way to increase the wing area of the airplane. It has always been my understanding that winglets reduce the amount of vorticies present at the tips, making the outer 20% or so (I believe), more effective. Looking at the numbers, I think that they are making the wing smaller in area for both better snaps, and also because they are relying on the canalizer for a lifting surface. I would conclude that they are trying to increase effective wing area without actually adding it.

I can see several downsides to this; first, with the shape of the wing, it would appear that it would decrease the aspect ratio of the wing, actually hurting the airplane's ability to snap. I would say the airplane's ability to snap with the winglets would be a function of how large they are as to how much they affect the aspect ratio. Secondly, I would like to know how much they would affect inverted flight, as you previously alluded. It would seem that they would need to be basically what Chip was using out at the tips so that the airplane would fly the same upright as well as inverted.

Just my humble opinion.

Regardless of that, I think the airplane looks really, really cool. Even if it is gimmicky, I like the looks of it, and it has an aggressive appearance about it. The only thing it needs now is a four-bladed propeller to make it look really mean!
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Old 11-14-2011, 03:08 PM
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Default RE: BJCraft Episode

Quote:
ORIGINAL: Doug Cronkhite

The problem with the winglets is they'll increase effective dihedral on the airplane when upright. I think it's interesting to see the developments, but a lot of this DOES feel very much like trial and error as opposed to engineering a solution to a problem.
+1
Exactly!!

the marketing dept is making design decisions again...

there is no way those winglets are gonna make that plane fly more neutral or symmetric (Upright vs inverted)
I expect the yaw coupling is significantly impacted in a negative manner in particular....


I expect there will be the Kool Aid drinkers that will go on and on about how great they make the plane...

hogwash....

winglets are for making a plane (specifically a wing) more efficient if there is a span limitation....
and the more effective a winglet is.. the more damaging it will be in the off-design condition...

all they need are little embedded LED's ......Buick Ventiports

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Old 11-14-2011, 03:21 PM
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Default RE: BJCraft Episode


Quote:
ORIGINAL: mithrandir

winglets are for making a plane (specifically a wing) more efficient if there is a span limitation....
and the more effective a winglet is.. the more damaging it will be in the off-design condition...
Do wingtip fences/SFGscontributeto thisnegative effort, to an extent?Or is it the case that since they are symmetrical above/below wingtip chord the negative effects cancel out?

Iguess the better question is - what are the overall effects of the SFGs? We know why they are being used, but what are they actually doing from an aerodynamic standpoint?
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Old 11-14-2011, 03:25 PM
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Default RE: BJCraft Episode

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.
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Old 11-14-2011, 03:33 PM
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Default RE: BJCraft Episode


Quote:
ORIGINAL: Ryan Smith
Correct me if I'm wrong, Doug.

My thought is that they are looking for a way to increase the wing area of the airplane. It has always been my understanding that winglets reduce the amount of vorticies present at the tips, making the outer 20% or so (I believe), more effective. Looking at the numbers, I think that they are making the wing smaller in area for both better snaps, and also because they are relying on the canalizer for a lifting surface. I would conclude that they are trying to increase effective wing area without actually adding it.
That's entirely possible Ryan. I know Christophe added the area from his canalizer into the total wing area on his Axiome, although there is some efficiency lost due to it being effectively a very asymmetric biplane.

What we REALLY need is for someone to tuft up a couple airplanes, and take a look at them in a real wind tunnel to see what's going on. I'm curious as to the effectiveness of CPLR's canalizer vs Naruke's fuselage strakes on his Asyuler External.
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Old 11-14-2011, 06:17 PM
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Default RE: BJCraft Episode

Doug.

I sure agree with you on a bunch of this thread! Earlier you mentioned that the Boeings dont do snaps and fly inverted, etc.. The wind tunnel, unless its pretty big and can discount the boundary layer problems that many wind tunnels have, will only show the results for a few attitudes and speeds. Our aerobatic planes are flying slow, fast, high alpha, snapping etc, so much of the information we can glean from certain kinds of "accepted testing" is only marginal.

I really believe you are spot on in your assessment of winglets. What we really want in aerobatics is just enough stability to draw the lines comfortably, and then come unglued in the instant we want the plane to do that. Even airfoil concepts kind of fall short of useful where our wide speed envelopes, light wingloading, high power loading, and rapid changes in attitude are needed. In fact, on some of our full size aerobatic counterparts, the airfoil design parameter most emphasized is "how stiff can I make it"!
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Old 11-14-2011, 09:06 PM
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Default RE: BJCraft Episode

Do I think there is a lot of Kook Aid drinkers. Perhaps. But that's the sport. Many of us wouldn't be flying electric had we not had a few sips of the Kool Aid right? That being said, I can tell you, it's not just about Kool Aid with these design ideas. I know for a fact, my Abbra flew a bunch better once I had the canalizer setup up properly on it. I know of very good pilots in my district that swear by the large canalizer/small second wing. I know of those that swear by the SFG's.. But remember this, what works in this years pattern, may not work in the pattern 2 years down the road. So it's going to be a constantly evolving thing with pattern IMO. Planes will change for the FAI pattern. Just the way it is.

I commend the designer of this airplane for thinking outside the box and trying something new. Without new ideas like this, there would be little advancement in designs. Does it work? I don't know, none of us do. Does it not work? We don't know that either. People are quick to speculate as to why things won't work though. In theory, I agree, this seems odd and theoretically, you all make sense to me.... Would love to have a plane I could chop us to try a bunch of different things on as Doug said.. Would be quite fun really.

Chris
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Old 11-14-2011, 09:21 PM
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Default RE: BJCraft Episode

Not sure what he's aiming to do with the double taper wing either.

It's all a bit, um, dunno really [&:]
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Old 11-14-2011, 09:27 PM
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Default RE: BJCraft Episode

Same thing as maybe the Spark wing I reckon.

Chris
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Old 11-14-2011, 09:39 PM
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Default RE: BJCraft Episode

Ok then, I'll bite, what was with the spark wing? That confounded me also!
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Old 11-14-2011, 09:40 PM
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Default RE: BJCraft Episode

Andrew says it snaps better having the narrower tips I believe.

Chris
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Old 11-15-2011, 04:52 AM
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Default RE: BJCraft Episode


Quote:
ORIGINAL: Rendegade

Ok then, I'll bite, what was with the spark wing? That confounded me also!
Yeah.. the wings on the Spark have to develop some interesting airflow as the spanwise flow reaches the break in the wing surface for the narrower tip. Granted there really isn't very much spanwise flow going on probably due to the relatively low sweep angle, but I bet there is some. Would love to see some CFD on the current generation of airplanes.

As for the Episode.. I absolutely applaud BJ for trying new things. I love that kind of creativity.
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Old 11-15-2011, 05:49 AM
  #23
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Default RE: BJCraft Episode

David Snow has doing extensive wing testing. He is flying an old Genesis wing on a Wind Pro 2 Contra. It had proverse roll coupling on rudderand he was able to counteract it with SFG's on the bottom of the wing only.
Sooo many do dads and so little time!!! Mike
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Old 11-15-2011, 06:33 AM
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Default RE: BJCraft Episode

Those SFGs on the bottom of the wing only change the drag profile "vertically", that is, lower the center of drag, among other things. If our planes had as much fuse below the wing as above, some similar things happen.

Check out some of the latest F3P planes from Europe that have this feature. Although foamies dont deal with everything that we do in F3A, many of the same aerodynamic situations come up (snaps, downlines, spins, etc)

AND you can change shapes by adding and subtracting bits and pieces of airframe. In just a minute or two, you can come up with an idea and test it. I was chatting with Dave Lockhart a few weeks ago. He said he takes

that same concept to the field with his F3A planes. He brings out foam and tape and adds it as the ideas come up. Same thing with Andrew out at our field here in Utah. His stepped wings on the Krill effectively lower the

aspect ratio, which helps snaps. The really neat thing about those wings is they are Dave Snow superlight wings and that makes soooo much difference in the snaps. I'm building those same wings for my Lightning right

now. The double taper effectively increases the tail moment. Plus, and I realize the dubious value in this, it looks cool.

Guy
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Old 11-15-2011, 06:54 AM
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Default RE: BJCraft Episode

Thanks Guy good info. Dave is developing a new Eliptical wing right now. It looks cool but as with anything will need to be tested before released. I had the Dynamic Snowbird's on my Spark. They were very impressive. Mike
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