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Old Mar 28, 2012, 07:07 AM
Tony Audsley Retired Locksmith
Lockey's Avatar
Australia, WA, Perth
Joined Sep 2011
3,098 Posts
Seawind 2 was a disaster, I wasn’t happy with it right from the start and I was fighting with it.

I kept it high because it didn’t seem to want to trim out properly, it seemed to be throwing its nose in the air and then all of a sudden I lost control of it altogether…. I simply had no control and it came in hard on the basketball court, only concrete on the whole oval.

I flew the other one (first prototype) straight after and it was OK, flew OK with the airfoil wing BUT didn’t seem to fly any better than it did with the flat wing.

I will first have to do a range check on the receiver in Seawind 2 to see if this was a problem.

Open to suggestions on why it would just simply fall out of the sky .... HELP PLEASE

Video with #16 cam on my hat

Lockey

Seawind Disaster.mp4 (1 min 21 sec)


Second flight on Seawind 1 finished in a small mistake on my behalf with a silly landing, only minor damage … silly me, maybe nerves from the other crash … that’s my excuse

Seawind 1 ... 2nd flight.mp4 (6 min 17 sec)
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Last edited by Lockey; Mar 28, 2012 at 07:54 AM.
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Old Mar 28, 2012, 05:50 PM
crashology student
Ontario, Canada
Joined May 2008
116 Posts
Lockey, I am so disheartened by you bad luck. I have followed your many hours of planning, building, making pdf plans, and testing with anticipation - Sorry for the loss ... is #2 salvageable at all?

Several of my crashes have been similar to yours and I chalk it up to brown-outs where the battery voltage has been drawn down enough for the RX to temporarily de-bind (but I'm no expert). Fortunately for me all my "downers" have been into water with little damage.

Hopefully one or more of the experts will chime in for an explanation to help you understand just what happened.

I have heard that both Spectrum and Orange RXs will brown out if you forget to reset the TX when changing batteries after a flight (if that is of any help).

Repair - rebuild - stay with it Lockey. Perhaps we could prepare a crashology course from our experiences ... Bob
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Old Mar 29, 2012, 12:13 AM
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Grand Junction, Colorado
Joined Dec 2007
2,930 Posts
To me big is 72" and up.
I am looking forward to starting a 300" B-17. Going to have to work out the finances for a foamy that big.


Quote:
Originally Posted by Lockey View Post
Thanks Larry, as soon as we get a day without wind (and I have the time) I will be able to let you know if it flies good ... when you say "big one" how big would you like it to be?



Can't find this in Bunnings or Mitre10 over here, looks like I might have to try and get it on line
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Old Mar 29, 2012, 12:53 AM
Tony Audsley Retired Locksmith
Lockey's Avatar
Australia, WA, Perth
Joined Sep 2011
3,098 Posts
Thanks Bob, we live and learn

I have spoken to Daedalus66, and after watching the video he seems to think it went into a spiral dive due to it being tail heavy and I tend to agree

With Seawind #1 I flew it first with a flat Depron wing, it seemed to fly best with the C of G at about 60-65mm from the leading edge of the wing

With the same model (Seawind #1) with a airfoil wing, it seemed to fly best with the C of G at around 50mm from the leading edge of the wing.

With Model #2, I had the C of G with a airfoil wing at 60-65mm and this looks like it is too far back…. silly me

It seems that maybe the flat wing … having less lift than the airfoil is more tolerant to the C of G a little further back.

Having no formal experience in aeronautics I am afraid I can only work from past experiences and trial and error, maybe some of you guys with more experience than I can throw some ideas and experiences in the mix.

I have glued the model back together, surprisingly little damage, I think dive or spin must have flattened out a bit before it hit the deck as the nose is dented on the underneath and not directly on the nose at the front.

For the Aussie guys, I have tested a new glue from Bunnings and it seems very good, and very strong (for some applications) such as this . It is a foaming type glue similar to Gorilla Glue, but half the price.

Lockey

PS.
Can anyone tell me if the wing tip floats would have any effect on stalling or spins?

If washout were to be incorporated in the wing, would the wing tips effect this?
.
.
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Old Mar 29, 2012, 05:09 AM
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Canberra Australia
Joined Feb 2007
1,455 Posts
Lockey, I've been using the Silka PU glue on my last few builds - since I could no longer get the Vise brand Bunnings used to sell. Seems to work well. A trick I have learned is to stand the bottle upside down (inside an empty jam jar or similar) between uses to prevent it from forming a skin and blocking the nozzle.

Sorry for the crash, great looking plane. To me (a bit hard to tell in the photos) it looked to be flying very slowly, almost at a standstill, just before it entered the dive. The slow flying might have caused a stall exacerbated by the rearward CoG, and it then entered the spiral dive. It was a tip-stall, so a bit of washout could be beneficial.
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Old Mar 29, 2012, 07:43 AM
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Lockey - I agree that a little washout is usually a good thing on a straight wing.

You probably know this, but one easy way to effectively add washout to a wing like yours with outboard ailerons, is to add a few degrees of up aileron to both ailerons (so they are both slightly up when the stick is neutral). This will lessen the tendency of a `tip-stall'.

Good luck on the re-maiden!
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Old Mar 29, 2012, 11:30 AM
Tony Audsley Retired Locksmith
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Australia, WA, Perth
Joined Sep 2011
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Thanks for the replies guys and thanks for the tip on the Silka PU glue Casey

Quote:
You probably know this, but one easy way to effectively add washout to a wing like yours with outboard ailerons, is to add a few degrees of up aileron to both ailerons (so they are both slightly up when the stick is neutral). This will lessen the tendency of a `tip-stall'
Thats a good idea with the ailerons Zaurak3, might be worth a try

Do you think the Tip Floats lessen the effect of the washout? Or do you think it will still work?

On this one it will be easier to lift the ailerons a little but it would be easy enough to put washout into the wing by blocking on end on the final gluing of the wing wrap.

I have had a lot of problems getting the Cof G forward, had to cut into the nose a little to get the battery further forward and without adding “extra” dead weight, I am going to use a 2200 battery

I am hoping that I am far enough forward now, it balances at 50mm from the leading edge, wing chord is 160mm ... can't get it any further forward without adding some weight

Here is the repair, ready for re-maiden just a little less pretty.

Lockey
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Old Mar 29, 2012, 01:15 PM
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Quote:
Originally Posted by Lockey View Post
Thats a good idea with the ailerons Zaurak3, might be worth a try
Do you think the Tip Floats lessen the effect of the washout? Or do you think it will still work?
Here is the repair, ready for re-maiden just a little less pretty.
Lockey
I doubt that the floats will have much effect either way, but the quasi-washout trick should help a little. Once you find the sweet spot for the CG, you can probably remove the washout trim - I have a switch on the transmitter to remove it for general flying, as washout can induce some adverse effects to roll characteristics, but it's nice to have in when flying slow, near stall speed.

Again, good luck with the re-maiden - she's a pretty plane.
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Old Mar 29, 2012, 01:19 PM
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Lockey that looks slick
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Old Mar 29, 2012, 01:51 PM
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United States, IN, Bloomington
Joined Sep 2007
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Lockey for a standard airfoil with rectangular wing shape you need to have the CG in the 25 to 30% range. You were in the 40% range on your initial test flights and that is quite tail heavy. By standard airfoil wing we are defining the max thickness to be in the 25 to 35% of cord area. I don't know how to judge flat non airfoil wing structures for CG but since they need to fly at a bit more of a positive angle of attack they can most likely tolerate a more rearward CG. For your next flight tests I would be sure that the CG was in the forward part of the range even if you have to add weight. You can sort it out after you get a good trim condition and push the CG back until you don't like it. A tail heavy plane is not a thing to have to deal with as it is very unstable.
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Old Mar 29, 2012, 01:51 PM
skumgummi dave
Gresham, OR.
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Lockey:

She is still a beauty.
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Old Mar 29, 2012, 07:48 PM
Tony Audsley Retired Locksmith
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Australia, WA, Perth
Joined Sep 2011
3,098 Posts
Thanks for all your comments and advice guys, it is really appreciated.

I agree that I need to get more weight forward and try to start with the C of G at 40mm from the LE and go from there

I don’t really need another disaster like the first one

Will let you know how it goes as soon as we get a calm day

Lockey
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Old Mar 30, 2012, 06:08 AM
We shall serve the Lord
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United States, TX, Kingsland
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An old sage once told me that nose heavy airplanes fly poorly, tail heavy airplanes fly ONCE.
McD
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Old Mar 30, 2012, 04:23 PM
60 years of RC flying
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Canada, ON, Ottawa
Joined Feb 2006
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Quote:
Originally Posted by rshep View Post
Several of my crashes have been similar to yours and I chalk it up to brown-outs where the battery voltage has been drawn down enough for the RX to temporarily de-bind (but I'm no expert). Fortunately for me all my "downers" have been into water with little damage.

I have heard that both Spectrum and Orange RXs will brown out if you forget to reset the TX when changing batteries after a flight (if that is of any help).
Hi Bob
I don't think there's any evidence of radio problems in Lockey's disaster. The rearward CG is enough to explain what happened.

As for brown-outs, they are 100% preventable. All you need is a decent ESC with plenty of capacity. For the size of model we are dealing with here, I always use a 40A ESC, preferably with switching BEC for even greater safety margin. The motor Lockey is using draws a bit over 20A at full throttle, so we are not pushing the ESC hard, and the three or four 9g servos will not tax the BEC too much. I've only had one brown-out type problem in over 10 years of flying electric (and that was with a helicopter and FM radio).

Failing to turn off the transmitter between flights simply causes the brown-out detector on the receiver (flashing light) to be triggered. It does no harm but if its already flashing it can't tell you if you have a problem. So always turn off the Tx when you unplug the battery. And always check the receiver light before you unplug to make sure you don't have a power problem.

By the way, brown-outs (as opposed to power failures) very rarely cause crashes. First, they aren't all that common, and second, they are generally momentary. The receiver should recover in under a second and you may not even know there was a problem. That's why Spektrum invented the brown-out detector to tell you you need to improve your power source.

I hope this clarifies things.
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Old Mar 30, 2012, 04:27 PM
60 years of RC flying
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Canada, ON, Ottawa
Joined Feb 2006
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Quote:
Originally Posted by Zaurak3 View Post
Lockey - I agree that a little washout is usually a good thing on a straight wing.

You probably know this, but one easy way to effectively add washout to a wing like yours with outboard ailerons, is to add a few degrees of up aileron to both ailerons (so they are both slightly up when the stick is neutral). This will lessen the tendency of a `tip-stall'.

Good luck on the re-maiden!
Very good idea. It doesn't take much, though.
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