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Old Sep 03, 2012, 12:16 PM
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Shadrack's Avatar
Winnipeg
Joined Feb 2002
5,757 Posts
Couple of hints that can help some people out.
I have almost finished reading this tome of information. There seems to be a common question and issue with the wing strength on here.
Now I have accidentally put a lot of stress on my wings. Looking back at the situations, there seems to be one thing in common. Wing lift. One scary issue I had at an fpv event lost me my ailerons. Now for the longest time I couldn't figure it out, but I remember when the plane landed, that my tilt servo wire was between the wing and the fuselage. The only way that happens is from a wing lift. I double check that when I setup for launch by testing every channel.
If the wing lifted enough, it would have pulled my aileron servo connection out of the receiver underneath in the fuselage.
Right after that, I purchased some SIG #67 elastics for 3 dollars a bag, and use 6 of them. Because they are tighter, I cross 2 of them, and hook in parallel 4 of them. No way is the wing getting lifted. Since then I have had 0 issues with the wing.
Now all I did for reinforcement was 2 strips of fiber tape. You can see where in the picture below. One from tip to flap cutout parallel to the ailerons, the other from the aileron servo to close to the root.
No problems.
Now I am not doing loops or rolls, but fly up to 120kmh and try to fly smooth. My wings, after going through crashing in a wheat field, and doing stunts not planned, had the holes the single spar goes into get a fraction larger. My solution, a layer of the strong fiber tape around the middle of the spar that makes sure it is tight. I have a rare earth magnet that holds the wing together, but once in the cradle, that isn't really doing anything as the elastics holding the wing down do that work.
The other thing I found yesterday with my 5.8 vTx, is that I was having issues with range when coming home. When I nosed down to lose some altitude and pointed at my ground station, I would get bad static. Made sense as the video signal had to go through the battery and internals of the plane.
Well I straightened out the coax, and used a 90 deg sma connector and raised up the 3 lobe antenna about 1.5 inches from where it was before.
Huge difference in signal and clarity. Had very few static points, up to 2 km yesterday.
Very happy with things.
Now I was running at CG of 30mm behind the servo wires on the v5.1 wing.
I found that it was hard to keep my plane in a shallow dive. It wanted to nose up all the time. What is that a symptom of Ian?
So now I am just trying to get the setup right so it is balanced. Have 5mm up and down on the elevator.
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Old Sep 03, 2012, 02:35 PM
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Blackrat's Avatar
Jeffreys Bay South Africa
Joined May 2006
1,313 Posts
lol mountaineering ..... thermic ... you liked it didnt ya hehehhehe

anyone flown with 20A 3s in a skywalker ? im gonna do a flight with 15A 3s , i dont think the fuse can hold the weight, so gonna wrap some bands around the fuse to keep it all together

ps this is with a non std wing
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Old Sep 03, 2012, 03:36 PM
OSUFPV - KF7VFT
Corvallis, OR
Joined Apr 2010
1,762 Posts
Quote:
Originally Posted by Shadrack View Post
I found that it was hard to keep my plane in a shallow dive. It wanted to nose up all the time.


-Blues
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Old Sep 03, 2012, 05:32 PM
If it's to be, it's up to me.
subsonic's Avatar
Sydney, Australia
Joined Jan 2007
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Quote:
Originally Posted by Shadrack View Post
I have a rare earth magnet that holds the wing together, but once in the cradle, that isn't really doing anything as the elastics holding the wing down do that work.
Thanks for all that Shadrack. A good contribution with your findings.

One thing though. The protrusions on the bottom of the wing root that sit into the cutout in the wing saddle are designed to hold the wings together when it's fitted to the fuselage. There is no need for any other feature to do this job.

Sub .
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Old Sep 03, 2012, 08:40 PM
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Shadrack's Avatar
Winnipeg
Joined Feb 2002
5,757 Posts
Sub
Yes, I know. I put those in more to keep the wing together when I was putting it on the plane. The strength is in the protrusions. That and the elastics holding them in there.
If the single spar was such a weak point, then why has the hole at the root of the wing not enlarged a lot?
The stress if it was at that point, would deform the foam where the spar slides in.
I did put strain on the wing, and I take my wing apart for transport, and the holes were not deformed. Little sloppy from the beginning so I put a wrap of fiber tape around the middle to totally remove the slop.
I don't know if it could do the things that Ian and others do, but it has shown me that it is up to the task.
I have no issues with version 5.1 and the single spar. This is at about 2.1 kg total. Have had cruises at 5 amps for level flight. The orb 1200kv is a great motor on 3S. Flew 18 minutes tonight using 2300 mAh.
I have a 6000 mAh battery.
This was not trying to be conservative.
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Old Sep 04, 2012, 02:47 AM
If it's to be, it's up to me.
subsonic's Avatar
Sydney, Australia
Joined Jan 2007
3,066 Posts
Quote:
Originally Posted by Shadrack View Post
If the single spar was such a weak point, then why has the hole at the root of the wing not enlarged a lot?
To answer your question directly, it's because the compression strength has nothing to do with the bending strength of the spar.

Quote:
Originally Posted by Shadrack View Post
I don't know if it could do the things that Ian and others do, but it has shown me that it is up to the task.
You may well have success with yours and it's likely down to a combination of luck, and the way you fly it. Others have not had the same success with version 5, and some have had failures with earlier versions which are widely accepted as being of a stronger design.

Sub.
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Old Sep 04, 2012, 03:22 AM
Foam Snow
South Africa, WC, Cape Town
Joined Aug 2011
1,325 Posts
Quote:
Originally Posted by Blueshy View Post


-Blues
Thanks Blues - but isn't it the other way around? CG too far back will cause the plane to climb?
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Old Sep 04, 2012, 04:02 AM
Fatshark Repairs AU/NZ
hpcoolahan's Avatar
Australia, NSW, Yamba
Joined Oct 2008
761 Posts
http://www.southernsoaringclub.org.za/a-CGdivetest.html

same idea , but a bit more explenation
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Old Sep 04, 2012, 04:26 AM
OSUFPV - KF7VFT
Corvallis, OR
Joined Apr 2010
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Quote:
Originally Posted by heinduplessis View Post
Thanks Blues - but isn't it the other way around? CG too far back will cause the plane to climb?
No, because you trim the plane to fly level (which the pic neglects to show) then do the dive test.

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Originally Posted by hpcoolahan View Post
same idea , but a bit more explenation
Ha! That was actually the one I originally searched for. Yes, read this. Much better.

-Blues
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Old Sep 04, 2012, 06:36 AM
Registered User
France
Joined Feb 2010
191 Posts
Anyone has tried to put the antenna like this on its video TX ?
The antenna seems do not touch the ground when the SW is landing. But il's limit
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Old Sep 04, 2012, 06:57 AM
Fatshark Repairs AU/NZ
hpcoolahan's Avatar
Australia, NSW, Yamba
Joined Oct 2008
761 Posts
Quote:
Originally Posted by jeff82 View Post
Anyone has tried to put the antenna like this on its video TX ?
The antenna seems do not touch the ground when the SW is landing. But il's limit

Personally i wouldnt do it , if you damage and short out the antenna on a rough landing , it will fry your transmitter and could even have a cascade effect through you OSD shorting it out too..........$$$$$$
Not a good idea really.
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Old Sep 04, 2012, 09:42 AM
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Winnipeg
Joined Feb 2002
5,757 Posts
I was thinking the same thing. I am setup in the same area. I had great success with the antenna pointing up in that location. I used a piece of antenna tubing like you used with the RC cars of the past. I taped it to the coax to brace it against the blast from the prop.
Works like a charm. Was out 2.5 km yesterday with this setup and totally clear video. Before when I had the coax bent and I wasn't using a 90 deg sma connector, it was rough coming home as the signal was forced to go through the plane/battery/receiver, etc.
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Old Sep 04, 2012, 09:48 AM
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Winnipeg
Joined Feb 2002
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Quote:
Originally Posted by subsonic View Post
To answer your question directly, it's because the compression strength has nothing to do with the bending strength of the spar.
.

So you think that the spar would break, or show signs of stress, before the foam was affected?
Not disagreeing, just trying to follow the logic from a physics standpoint.
So if we braced one side of the wing so it can't move, and inserted the spar fully, and then grabbed the exposed end of the spar and started to move it to the side, you say that the spar would snap before the foam would deform?
I would also think that if that was the weak area, that there would be signs of stress after some flights. If the wing was deformed at that middle point, again, would the top section of the wing that fits flush with the top of the other wing not be compressed as well?
I just want to feel safe with the setup I have now.
I have had the wing lift and cause multiple high G loops that were unintended. People watching from the ground were surprised that the wing didn't snap. It didn't even show stress.
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Old Sep 04, 2012, 09:57 AM
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France
Joined Feb 2010
191 Posts
I've tested with the antenna pointing up and i was having many issues when coming home at 1,3 km. The video is totally clear in the other direction. So I think i've a masking effect and I'm looking for another setup for my antenna.
I've tried also to put the antenna not in the alignment of the fuselage but the issue is the same when coming home with a little shift.
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Old Sep 04, 2012, 10:01 AM
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idletime's Avatar
Canada, ON, Toronto
Joined Apr 2011
1,574 Posts
Quote:
Originally Posted by Blueshy View Post
No, because you trim the plane to fly level (which the pic neglects to show) then do the dive test.



Ha! That was actually the one I originally searched for. Yes, read this. Much better.

-Blues
Makes a huge difference to the information originally communicated - cuz I myself thought the diagram was wrong.

Makes sense now.
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