**EPP Peregrine, FFF-Eagle, Dragons and other Bird Planes** - Page 203 - RC Groups
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Aug 12, 2017, 11:42 AM
PunchDrunk ex-Pug try'n fly'n
jp.electrik's Avatar
Quote:
Originally Posted by flypaper 2
Many planes drop the nose in a turn. Let it stay dropped until you complete the turn, then level out. This helps keep above the stall speed.

Gord.
Right on the money keep your speed up and nose down. 😎 I hear thatfrom the guys in the club who know.
jp
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Aug 12, 2017, 11:55 AM
Registered User
flypaper 2's Avatar
57 yrs at RC and still learning. Wish we had the RC stuff now , back then.

Gord.
Aug 12, 2017, 05:25 PM
Lee
Lee
PERFECT LANDING !!!
Lee's Avatar
Often a stall is caused by too much up elevator. Your instinct is to give more up to correct the stall but you are better off letting go of the elevator and let the plane dive then gently pull the plane out of the dive. In other words you may have too much up elevator.

Another common problem is a slightly tail heavy plane. Add a little weight to the nose and see if that helps.

Another problem may be stalled servos. Are the servos strong enough to pull the plane out of a dive. Is the elevator flexing instead of responding to the servo?

All planes will stall if the flying speed is lower than the stall speed. I have seen many flyers flip planes over trying to land at too low of a speed. Keep the speed up and you are less likely to stall.

lee
Aug 12, 2017, 05:57 PM
PunchDrunk ex-Pug try'n fly'n
jp.electrik's Avatar
Some of you guys really know what you're talking about ....that's why I know who to listen to😎.
Meanwhile I'm trying to work out the inverted V-tail on my dancing wings eagle. big challenge this kit!
jp
Aug 12, 2017, 06:17 PM
Registered User
G-LO's Avatar
JP, here are some examples from a Rcgroups member who inverted his Eagle's tail.
https://www.rcgroups.com/forums/show...-Eagle/page163
Aug 12, 2017, 07:18 PM
Careful,.. confident,.. CRASH!
Dukejet's Avatar
I have a LOT of Vtails ..... others call it a fetish...lol.... I've set mine up at 100 to 110. They have always been well behaved.
Aug 13, 2017, 02:18 PM
mutski

Stalled and Crashed Again!


Thanks all for the good advice, especially JP.Electrik. Unfortunately, I've stalled and crashed again. I've never had a plane so prone to stall or so difficult to recover when it does. I read a lot about aerodynamics when I built V3, the one that crashed yesterday. The CG was exactly as specified in the plan, but I'm thinking it's still tail-heavy because it keeps bobbing nose-up in the wind. Changes I made in V3:

- I sanded the leading edge to a typical rounded airfoil shape ... the V2 wing was square from the stacked layers of foam. I thought rounding the leading edge might make it less likely to stall.
- I increased the dyhedral to 5 degrees. It was 2.75 degrees in V2. I was hoping dihedral might make its stall behavior more benign.
- I moved the tail servos forward and put the CG exactly as marked on the plan. I think V2 may have been a tad tail heavy.
- Put a lot of effort into getting the firewall square. It finished level and tipped very slightly to the right. In V2, I had the motor shimmed slightly right and slightly down.
- Mounted the electronics as low as possible in the fuse to increase the pendulum effect and help keep it level.

As in V2, the V-tail has an angle of about 105 degrees, with the base of the V level with the base of the wing. The FFF Eagle plan calls for setting the tail on top of the fuse. Anchoring the base of the V to a flat surface seems shakey to me, so I've recessed it into the fuse, similar to Tom Frank's eagle: https://www.rcgroups.com/forums/show...&postcount=821 I know his eagle flies well, but I'm wondering if lowering the tail puts it more in the wash from the wing, making it harder to control when it stalls.

V3 specs:
All-UP-Weight: 1 lb, 6.5 oz (637 gm)
HexTronics 24 gm 1300kv motor
APC 8x4.7 slow electric prop
3S 1250 kv battery
Turnigy Plush 12 amp ESC
Lemon rx with satellite
EXI D113F 9gm nylon servos for the tail
EXI D213F 9gm metal servos for the wing
Dihedral 5 degrees
V-tail 105 degrees

I also watched a bunch of videos on stalls and spins and practiced stalling and recovering the Sky Surfer glider on a simulator ... slow bank and up elevator to make it stall and spin, then release the elevator briefly to exit the stall and up elevator to exit the dive.

V3 was the easiest hand launch ever. It just floated out of my hand, didn't really require a toss. There was a 3-4 mph breeze for the maiden. The first flight went fairly well, but it kept bobbing nose-up on the breeze. I dialed in a little down-elevator trim but still had to push on the stick. I flew for 10 minutes, made an effort to keep the nose down and recovered from several stalls. The second flight was similar until it bobbed way nose-high on a gust, stalled and actually fell backwards. I recovered from that, but it slipped into several more severe stalls. I got out of a couple, but the last one was too close to the ground and it crashed. Maybe the simulator practice helped... I was able to fight it for quite a while before it augered. Here are the vids. Skip to 1:04 in the second video if you just want to see the crash sequence.

FFF Eagle maiden 8 12 17 (2 min 49 sec)

FFF Eagle stalls and crash 8 12 17 (1 min 35 sec)


In then end, I'm thinking maybe the CG marked in the plan is too tail-heavy. That would account for the strong tendency for the nose to bob up on the breeze. Unfortunately, the battery is right up against the firewall and I've moved the electronics as far forward as possible.

I am thinking I'll build a new fuse, this time with a T-tail. I'm tempted to make it more compact to make it easier to make the plane slightly nose-heavy. Maybe like this: https://www.rcgroups.com/forums/show...&postcount=513 But will I need a big rudder to fight the spin? The other possibility is like this: https://www.rcgroups.com/forums/show...&postcount=108, which is basically the same parts used in the original V-tail from the plan. More weight in the tail . I could use a 25 amp ESC to help weight the nose, but then, increasing all-up weight increases the stall speed. I could build a V-tail like on the Banggood eagle, which seems to have an angle much less than 105 degrees, i.e. more rudder control and less elevator. The Banggood eagle looks easy to control and even mildly acrobatic in Youtube videos.
Aug 13, 2017, 03:10 PM
PunchDrunk ex-Pug try'n fly'n
jp.electrik's Avatar
Mutt, I give that day of flight and A-. The maiden look pretty good. And it looks like you returned home with a whole aircraft. I count that as a success. ����
The improvements you made on the V3 sound spot on. Check your COG by using the Dive test. It DOES look tail heavy and that is the kiss of death. All said I think you're on the right track and doing great keep up the good work Mutt...
I wonder if your KF design is part of the problem I've done a lot of work myself with the Klien Fogleman and found if I didn't have the steps just write it didn't fly well. Best part is it's so cheap to make and easy you just start over. I would try more winglet and possibly dihedral.
jp
Last edited by jp.electrik; Aug 13, 2017 at 03:16 PM.
Aug 13, 2017, 03:23 PM
mutski
Quote:
Originally Posted by jp.electrik
Mutt, I give that day of flight and A-. The maiden look pretty good. And it looks like you returned home with a whole aircraft. I count that as a success. ����
The improvements you made on the V3 sound spot on. Check your COG by using the Dive test. It DOES look tail heavy and that is the kiss of death. All said I think you're on the right track and doing great keep up the good work Mutt...
I wonder if your KF design is part of the problem I've done a lot of work myself with the Klien Fogleman and found if I didn't have the steps just write it didn't fly well. Best part is it's so cheap to make and easy you just start over. I would try more winglet and possibly dihedral.
jp

What are the obvious mistakes to make in the KF wing? It seems pretty simple... glue the layers together and you have a wing.

PS - not quite whole. The nose is smashed but fixable.
Aug 13, 2017, 05:51 PM
PunchDrunk ex-Pug try'n fly'n
jp.electrik's Avatar
I guess I'm remembering the times when I was experimenting with the placement of the steps on both top and bottom, some worked better than others.
That was just a sidenote anyway I'm sure the COG is your problem.
jp
Aug 13, 2017, 09:15 PM
Culper Junior
Mutski,
My two cents...just wondering out loud if your wing leading edges are the cause of your stalling. By sanding you might have introduced different angles causing high angle of attack stalls similar to having stall strips. See here....https://www.google.com/search?q=stal...0on%20aircraft

I watched the 'stall and crash' video and the last 20 seconds of flight appear to be a radio or linkage problem. As if you were giving the correct control but either the radio wasn't working right or maybe a control surface malfunctioned by jammed linkage somehow.

Again my unasked for two cents.
Aug 13, 2017, 09:17 PM
Lee
Lee
PERFECT LANDING !!!
Lee's Avatar
Is it possible it is a loss of radio control?

You had a lot of time to regain control when the eagle was coming down in the second video.
Last edited by Lee; Aug 13, 2017 at 11:39 PM.
Aug 13, 2017, 11:12 PM
Registered User
My Canadian Eagle had been flying OK for about 2 years. I went out to fly with Lee in early June, and it crashed. I fixed it up and it crashed again - going in a wide death spiral. I finally changed the receiver from an old HK Orange to a real Spektrum and have had no further problems with it. My Bangood Eagle had similar problems until I moved the CG to 30mm behind the LE instead of 50mm which was incorrect on the instructions. -- Milt
Aug 14, 2017, 01:45 AM
mutski
Quote:
Originally Posted by aeronca52
Mutski,
My two cents...just wondering out loud if your wing leading edges are the cause of your stalling. By sanding you might have introduced different angles causing high angle of attack stalls similar to having stall strips. See here....https://www.google.com/search?q=stal...0on%20aircraft

I watched the 'stall and crash' video and the last 20 seconds of flight appear to be a radio or linkage problem. As if you were giving the correct control but either the radio wasn't working right or maybe a control surface malfunctioned by jammed linkage somehow.

Again my unasked for two cents.
I actually range-checked the radio before I flew it. At 95 paces, I had full control at low power. I didn't have the feeling my commands weren't reaching the plane when it crashed. I had the feeling it was stalling and spinning faster than my poor brain could catch up. I used the Lemon rx because it is tiny and light. I do have an AR6010 and an Orange rx I could stick in there though. I am still betting the CG needs to be further forward... i.e. it behaves like its tail heavy even though I balanced it according to the plane.
Aug 14, 2017, 05:43 AM
Registered User
flypaper 2's Avatar
Couple of things that bother me. In the video in post 3026 , the plane is almost vertical on its way down. Usually a stall spin from rearward CG will almost be a flatspin until you give the down elev to get the wing flying again.
With the swept forward wing much further out from the fuse, will give a much further point forward than we are used to with a straight wing. I'll bring mine in from the truck and measure it a little later. I know it's not far away from the leading edge at the fuse.

Gord


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