Amokka Race Plank - Page 2 - RC Groups
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Oct 20, 2008, 03:51 AM
Crikey never leave beer behind
steve wenban's Avatar
I would expect nothing less from Mr Wick's Stable. Another rocket with a mission.
SteveW
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Oct 20, 2008, 08:10 AM
Taranis Tyro...
MattyB's Avatar
Very impressive! I am still sceptical you will be able to generate a competitive F3F machine for lighter conditions, but it seems clear the gap has been narrowed between tailed and tailless in high lift conditions for F3F. Nice job!

Matt
who likes the performance, but is scared by the prospect of landing a 3m F3F plank in 25mph+!
Oct 20, 2008, 09:02 AM
Suspended Account
I want one too.. Thats a fast plank, but the conditions looked ripe for good flying.
Oct 20, 2008, 09:15 AM
Suspended Account
correction, thats a very fast plank!!
Oct 20, 2008, 09:56 AM
Detail Freak
target's Avatar
Quote:
Originally Posted by MattyB
Very impressive! I am still sceptical you will be able to generate a competitive F3F machine for lighter conditions, but it seems clear the gap has been narrowed between tailed and tailless in high lift conditions for F3F. Nice job!

Matt
who likes the performance, but is scared by the prospect of landing a 3m F3F plank in 25mph+!

I'm also wondering about the landing manners and speed. I would have liked to see some footage of the landing.
Most F3F races here in Socal have no less than 8 rounds, so there is 8 or more chances to wreck your plane.

How effective is this "Crow" setup on a plank?? Please explain for us Peter. I would like to know more.

Kind Regards,
Target
Oct 20, 2008, 12:15 PM
Taranis Tyro...
MattyB's Avatar
Quote:
Originally Posted by target
I'm also wondering about the landing manners and speed. I would have liked to see some footage of the landing.
Most F3F races here in Socal have no less than 8 rounds, so there is 8 or more chances to wreck your plane.

How effective is this "Crow" setup on a plank?? Please explain for us Peter. I would like to know more.
I think this is the problem, and why big planks are such a rare sight. Reading through Peter's post...
Quote:
Originally Posted by Peter Wick
Crow braking is a little bit different as from F3X planes. So far I think it breaks a lot, meaning a lot of height is lost, but it does not slow the Amokka down like it does on a F3X plane. So the landing plan is something like this: Come in at good height, crow break with nose down all the time, the speed is not that high, and flare out close to the ground with no flaps. If overshooting seems to become a problem, just open the crow for a short moment and the plane bleeds of speed.
...it sounds like he's got the classic plank problem of a high rate of descent under crow, but no reduction in speed. I can see this is manageable at 1.5m-2m span and reasonably low weights, but when it's 3m and carrying ballast, the energy in play and the increased precision required to land totally flat makes it a scary prospect. I've no doubt Peter can make a competitive machine, but unless he can get over this problem I agree it's not going to last an F3F comp, where there's a lot of landings in a day. Two possible appoaches...
  1. Build the fus with a superstrong layup, and "one point" it in each time;
  2. Try something even more radical - well, it worked for Apollo (most of the time)...!
Last edited by MattyB; Oct 20, 2008 at 12:41 PM.
Oct 20, 2008, 12:31 PM
Obsessed
screamin' eagle's Avatar
I agree that slowing these beasties down for landing is where the rubber (or the plane!) meets the road, so to speak. Perhaps the split rudder being used the custom Zipper in another thread (apologies, can't remember the OP's name) is a possibility? I have a few heavy composite planks, and a lighter 48" PW51 composite design, and they are all suicidal on landing...
Oct 20, 2008, 12:57 PM
Detail Freak
target's Avatar
I saw a design from the 90's that had a hinged up spoiler, like an RES plane has. I'm not sure how effective that would be, but maybe one with enough chord at 90* would slow it down(?)

T
Oct 20, 2008, 02:22 PM
Registered User
well, problems are here to be solved.

I am not at all so negative at this could be a serious drawback for heavy planks. There is quite a lot of speed reduction during crow breaking the Amokka. I wrote, it is just not as good as on others F3X planes.
The problem with the crow setting right now / if you can call it a problem / is more that because of the rather straight leading edge the inner flaps are quite far from CG, haveing a strong impact on the pitching moment. It is easy fx to fly the Amokka just with the innner flaps alone as elevator.
But during crow breaking this down pitching moment has to be compensated by the ailerons. Even the span of the inner flaps are much shorter than the ailerons, the Amokka loses too much lift by the uptrimmed ailerons. So drag is fine during crow breaking, but lift could be better.

Solutions: Another planform or making the inner flaps even shorter. I tend to the second solution.

I also had once a only 8 degrees swept wing with E228 airfoils in the 80 `s. The E228 has only 0,2% camber and I was flying F3B with it. So almost a plank and not a lot of lift. Breaking was easy with a so called "Endleisten-drehklappe"...This is a kind of flap where the upper part of the flap (upperside skin of the airfoil) is just half the chord as the underside (underside skin of the airfoil) of the flap. The flap is then hinged at this half chord point on the upper side. During breaking the flap opens 90 degrees, causing a lot of drag, almost no pitching moment and almost no loss of lift.

On other planks we simply found the best position for spoilers by taping them on the upperside of the wing together with the servo. Best position means no pitching moment.

The landing of the Amokka was by the way very fine and if it was caught on video, I don`t think there will have been this discussion, as it looked very much like other F3F planes coming in fast trough the sheer layer . As bigger planes take more advantage from the ground effekt and fly more stable they seem to flare out quite nicely. But I must admit, that coming in with a plank makes my heart going faster...but I doubt it is because of a huge landing problem....I like them.
The newer airfoils produce also more lift, which makes things easier.
So drag is not a problem..lift is / probably forever.


Yours Peter
Oct 20, 2008, 03:15 PM
Its not IF... Its WHEN.
The.Timinator's Avatar
Hi Peter

That really is a superb piece of work.

I love planks, for their "distinctive challenges" and I wish you all the best with a full-blown F3f version

Tim
Oct 21, 2008, 07:36 AM
Taranis Tyro...
MattyB's Avatar
Quote:
Originally Posted by Peter Wick
I also had once a only 8 degrees swept wing with E228 airfoils in the 80 `s. The E228 has only 0,2% camber and I was flying F3B with it. So almost a plank and not a lot of lift. Breaking was easy with a so called "Endleisten-drehklappe"...This is a kind of flap where the upper part of the flap (upperside skin of the airfoil) is just half the chord as the underside (underside skin of the airfoil) of the flap. The flap is then hinged at this half chord point on the upper side. During breaking the flap opens 90 degrees, causing a lot of drag, almost no pitching moment and almost no loss of lift.
Interesting - do you mean kind of like the illustration below, Peter? I suggested that as a possible solution in a thread last September, but I wasn't aware anyone had tried it - good to know not all of my ideas are rubbish!

Quote:
Originally Posted by Peter Wick
On other planks we simply found the best position for spoilers by taping them on the upperside of the wing together with the servo. Best position means no pitching moment.
I have never tried spoilers on a plank, though I've seen them on thermal planks but never a slope ship. Do you intend to use them on the 3m version, or will you stick with crow based on your findings so far?

Quote:
Originally Posted by Peter Wick
The landing of the Amokka was by the way very fine and if it was caught on video, I don`t think there will have been this discussion, as it looked very much like other F3F planes coming in fast trough the sheer layer. As bigger planes take more advantage from the ground effekt and fly more stable they seem to flare out quite nicely. But I must admit, that coming in with a plank makes my heart going faster...but I doubt it is because of a huge landing problem....I like them.
The newer airfoils produce also more lift, which makes things easier.
So drag is not a problem..lift is / probably forever.
Thanks for the extra detail Peter. One more question... do you ultimately intend to place these new airfoils in the public domain, as per PW51? I'm not suggesting you'd do so until you've had chance to expereiment more yourself and complete your F3F ship, but based on the performance of the Amokka and Retox I suspect you'll have a bulging inbox in the near future - letting people know whether you intend to release these foils at some point might prevent this!

Congratulations, and thanks again for your innovative work!
Last edited by MattyB; Oct 21, 2008 at 01:05 PM.
Oct 21, 2008, 08:07 AM
Registered User
Sleedo's Avatar
Peter, instead of the complexity of the above flap arrangement has there been any thought or better yet testing of a split flap design where the top skin is stationary and just the bottom skin of the flap deflects downward?


I could imagine how this would create a lot of drag but I have no idea how it would effect the rest of the planks' control.

Ed B
Oct 21, 2008, 08:07 AM
Composites Kid
Alex.Schweig's Avatar
Good idea on those sketches. What kind of hinge would you use?
Oct 21, 2008, 09:46 AM
Detail Freak
target's Avatar
Quote:
Originally Posted by Sleedo
Peter, instead of the complexity of the above flap arrangement has there been any thought or better yet testing of a split flap design where the top skin is stationary and just the bottom skin of the flap deflects downward?


I could imagine how this would create a lot of drag but I have no idea how it would effect the rest of the planks' control.

Ed B
I would think for a plank, you'd want the fixed portion on the bottom, and the top to come up....
Just an idea.

T
Oct 21, 2008, 01:10 PM
Taranis Tyro...
MattyB's Avatar
Quote:
Originally Posted by Alex.Schweig
Good idea on those sketches. What kind of hinge would you use?
Given the Amokka is a composite machine, I'm guessing living hinge of kevlar or somethign similar. Having said that, I'm sure tension hinges would do if you did them well enough.


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