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Old May 02, 2010, 09:50 AM
Cybernaught is offline
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Onward through the fog.
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Quote:
Originally Posted by phil alvirez View Post
...with all this considered, it is easy to understand why there are so few of them around (and none on competition free flight).
don't take me wrong: i like them. they are different, and give the plane a futuristic look. but they are fickle, heavier, more fragil, more complex, and less efficient....
I guess I like them 'cos they're different and look good, to me... They are harder to get to perform right. But then performance is kinda in the eye of the pilot and subject to what he/she likes.
RET planes are easy to me now and I like wings a lot because there's no fuselage to create extra drag. They're nice and simple.. I was getting into Parkjets a bit when the canards came up and deflected my interest into this area. Not sure how long the interest will stick. I move around a lot, within the hobby, and kind of go with the flow. The thing that is remaining constant for me is the use of the simpler KF airfoils. I put a KFm2 on just about everything and for general RC use I'm convinced it's the simplest best thing since the Wright brothers got us into this mess in the first place.

I've no idea where my "RC" interest will lead but I"m having fun and that's whats important to me.
I don't drink, chase women or gamble and it keeps me out of the pool halls so Edna is supportive of it.


Steve.

PS. I believe "canard" is French for "duck".
Last edited by Cybernaught; May 02, 2010 at 09:58 AM.
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Old May 02, 2010, 09:52 AM
poweredlawndart is offline
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Years ago, I had a 100" sail plane I put strip ailerons on. It flew well until I did that.

Left about the first two thirds fixed and left the outboard third operational.
Better!
Added differential throw and the rest was history..success, turned on a dime, well a quarter (sailplane)

Food for thought...

Love your predator, F/B is building the 98" one from Nitro Planes and going to start a build log in Warbirds. I'llcheck out his ailerons....Dart
Old May 02, 2010, 10:00 AM
phil alvirez is offline
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???


Quote:
Originally Posted by gpw View Post
Phil ... guess you've never built a FOAM-EZ huh ...???
why you guess?
Old May 02, 2010, 10:18 AM
phil alvirez is offline
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you enjoying it is all that matters


Steve: i agree with you.
in my blog i have an anecdote about the subject.
regards
Old May 02, 2010, 03:39 PM
nxtee4509 is offline
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Build, fly, CRASH, repeat
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Quote:
Originally Posted by phil alvirez View Post
50% seems too far back. that may make the plane too unstable. most planes balance around 33%, which is near the aerodynamic center of the airfoil, so there is no leverage between forces: all are concentrated on the same point
if you try shifting it forward, let us know how it works.
This is my first KF wing and I thought is was kinda different as far as COG. All my other builds were flat wings and a couple had normal airfoil shape and typically cog was 25-35% range. And around 30" wingspan. In reading up on the KF types I saw where the step for the KF2 determines cog. I thought I would give this one a try. This design is by another person with a build log here in rcgroups. It is still a work in progress as most scratch builts are.
As far as shifting COG forward that is a wing rebuild with the step closer to the leading edge. I have been contemplateing building a new wing alltogether anyway.
Here is a link to the plan if anyones interested
https://www.rcgroups.com/forums/show....php?t=1169243
Old May 02, 2010, 04:08 PM
nxtee4509 is offline
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Build, fly, CRASH, repeat
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Going to do more testing on this wing before i build another . I was surprised and happy with the takeoffs from this wing. I was expecting at least 30 ft run before it lifted, but it took to the air in about 10 or so ft with 5mph headwind. If and when I do a rebuild on the wing I plan on COG closer to leading edge, a little dihedral, stiffer structure, shorter and stiffer ailerons.
I first saw a version of the Predator from Nitro Models in Backyard Flyer magazine May 2007 "Still have a copy" Wanted one for a while. When the bugs are out a camera will be added.
I really appreciate the input guys.
Old May 02, 2010, 05:13 PM
phil alvirez is offline
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cg at 30-40%


nx: the position of the step does not determine the cg.
planes with flat (non-lifting) stab must balance between 30-40%, no matter if you use steps or not.
it is a good idea that on the new wing you are going to use the cg further forward. you will see that the plane may not take-off as quickly, but sure will be more stable.
and with the wing reinforced to avoid flexing too much, most likely you will have a much better time with it.
keep us posted
Old May 02, 2010, 06:52 PM
nxtee4509 is offline
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Build, fly, CRASH, repeat
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Quote:
Originally Posted by phil alvirez View Post
nx: the position of the step does not determine the cg.
planes with flat (non-lifting) stab must balance between 30-40%, no matter if you use steps or not.
it is a good idea that on the new wing you are going to use the cg further forward. you will see that the plane may not take-off as quickly, but sure will be more stable.
and with the wing reinforced to avoid flexing too much, most likely you will have a much better time with it.
keep us posted
The winds died down and I tried another flight. After the additon of flat Cf along the ailerons the flight was more stable in turns. I used a Thunder power battery instead of Turnigy. About 3oz lighter.

I could of swore i read somewhere the step determines the COG. Hmmm anyway the plan called for a 50% step with COG at or near the step. I Adjusted cog for previous flights around 1/4 in. ahead of step anyway. I like a liitle nose heavy. Have had a couple of planes wanna 3d on me after take off. Not into 3d
Todays flight went much better but the lighter battery had me flying with down elevator and after a few circles brought it in. The landing detached the rudder and had to bring it home for repairs.
Old May 02, 2010, 07:19 PM
Cybernaught is offline
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Onward through the fog.
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Quote:
Originally Posted by nxtee4509 View Post
This is my first KF wing and I thought is was kinda different as far as COG. All my other builds were flat wings and a couple had normal airfoil shape and typically cog was 25-35% range. And around 30" wingspan. In reading up on the KF types I saw where the step for the KF2 determines cog. I thought I would give this one a try. This design is by another person with a build log here in rcgroups. It is still a work in progress as most scratch builts are.
As far as shifting COG forward that is a wing rebuild with the step closer to the leading edge. I have been contemplateing building a new wing alltogether anyway.
Here is a link to the plan if anyones interested
https://www.rcgroups.com/forums/show....php?t=1169243
Good luck with your first KF wing. I use them exclusively, specially the KFm2, and find them to be great for RC planes. The KF wings seem to be able to fly OK with a CG that is a little farther aft than the conventional foils. Tip plates to contain the tip vortexes seem to help but can be omitted. Using foam and hot glue you can knock one together in nothing flat!

I think you'll like it.
Steve,

PS. nx, For your first KF foil, I suggest you keep the step at the 50% point. That is including the ailerons if there are any. Though 40% works OK too, the 50% step has been proven to work well and is the standard.


PPS. Phil is right about the CG placement. I would balance a conventional plane about 1/3 back from leading edge of the wing. (33% for no sweep) After you fly it a bit you could try moving the CG back a bit at a time and I think you will find you can get away with a more aft CG with the stepped wing than with, say, a Clark-Y. Don't fly with the CG too far back or you'll have serious control problems.

Let us know how you progress.

Steve.



Edit: 12:41 Monday May 3, 2010
the nose should be bullet proof but the back is weak. I'll have to be careful. It's a canard with only 12 sq in of area up front. Balance is within 1/2" of calculated and I'll put a peso or 2 on the nose to make sure it's not tail heavy...
Last edited by Cybernaught; May 03, 2010 at 12:47 AM.
Old May 03, 2010, 12:48 AM
nxtee4509 is offline
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Build, fly, CRASH, repeat
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Quote:
Originally Posted by Cybernaught View Post
I guess I like them 'cos they're different and look good, to me... They are harder to get to perform right. But then performance is kinda in the eye of the pilot and subject to what he/she likes.
RET planes are easy to me now and I like wings a lot because there's no fuselage to create extra drag. They're nice and simple.. I was getting into Parkjets a bit when the canards came up and deflected my interest into this area. Not sure how long the interest will stick. I move around a lot, within the hobby, and kind of go with the flow. The thing that is remaining constant for me is the use of the simpler KF airfoils. I put a KFm2 on just about everything and for general RC use I'm convinced it's the simplest best thing since the Wright brothers got us into this mess in the first place.

I've no idea where my "RC" interest will lead but I"m having fun and that's whats important to me.
I don't drink, chase women or gamble and it keeps me out of the pool halls so Edna is supportive of it.


Steve.

PS. I believe "canard" is French for "duck".
I too have a interest in a canard design. The x-41 which is another build here in scratchbuilt foamies. I am on my third rebuild. Each one of mine had fixed canards though. They flew great for me and my relaxed type of flying. I added landing gear, which I do for all my planes. The second build had raised motor mount for better ground clearance of the prop.
I am contemplating KF wing on X-41c but not sure where to start.
Old May 03, 2010, 01:31 AM
phil alvirez is offline
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cg ahead


nx: it is great to hear that!: if you moved the cg 1/4" ahead, and your flight was better, and still you had to keep pushing 'down', it means you are moving into the right direction, but still need to go further=move cg ahead more until you don't have to keep pushing 'down'.

Steve (cyber): i read somewhere that the word 'canard' came from, when the Wright brothers went to paris for a demo flight, and their 'flyer' was flying too low, 1 of the americans yelled 'duck', meaning 'keep down', and 1 frenchman that had some knowledge of english translated it to french and yelled 'canard', and the others misunderstood it as the name of the plane. the rest is history.
(and i have another still funnier about where the name of canada came from)
Last edited by phil alvirez; May 03, 2010 at 01:54 AM.
Old May 03, 2010, 12:50 PM
A Useless Geek is offline
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'C', eh? 'N', eh? 'D', eh?

Everybody knows that one, eh? Beauty.
Old May 03, 2010, 01:09 PM
phil alvirez is offline
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from 'the village'


Quote:
Originally Posted by A Useless Geek View Post
'C', eh? 'N', eh? 'D', eh?

Everybody knows that one, eh? Beauty.
not exactly what am talking about:
when the 1st explorers landed on what is now canada, they met the natives in good terms, and asked them what was the name of the place. of course no one knew a word of the other's language, and spoke with signs. the natives wanted to bring the visitors to their village, and pointed in that direction and said: cana-TA (meaning 'the village'), and the visitors repeated: cana-TA. so they left with the impression that it was the name of the place, and made it known by that name (it drifted to cana-DA, then CA-nada).
could you think of something funnier than that?
Old May 03, 2010, 10:44 PM
Cybernaught is offline
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Onward through the fog.
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Monday I should have stayed in bed!


5 flights, three planes trashed.
See for your self.

3 in 1 day.wmv (1 min 1 sec)


No excuse my reflexes went to hell!

Steve.
Old May 04, 2010, 02:55 AM
phil alvirez is offline
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'an archer is no better than his arrows'


Steve: i don't know how much of that is to blame to your reflexes.
it may be that the weather at the time also contributed to the demise of the planes.
sometimes is not a single factor.
i still believe that more stable planes would recover from those spins.
i don't think it was bad reflexes. watch the movie again.
but if you like to try unconventional planes, remember that 'pioneers get all the arrows'.
designing is a long, rough road, full of bumps, but it is a matter of persevering.
and, as you said, if you enjoy doing it, well, keep doing it. you may eventually find the answer.


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