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Nov 25, 2018, 08:36 AM
Tony Audsley Retired Locksmith
Lockey's Avatar
Quote:
Originally Posted by Jürgen Be
Nice

10mm up elevator I think is but much, on the Jetstream I have 6mm.
mabe you can move the CG a little back.

Jürgen
Thanks Jürgen, yes mate will try that

Lockey
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Nov 25, 2018, 01:24 PM
Registered User
tspeer's Avatar
Maybe it needs a modest sized canard?
Nov 25, 2018, 06:33 PM
Tony Audsley Retired Locksmith
Lockey's Avatar
Quote:
Originally Posted by tspeer
Maybe it needs a modest sized canard?
Now theres an idea

Now whilst that would give it more lift at the front (I think) would that mean the CG would be further forward or further back ?

Lockey
Last edited by Lockey; Nov 25, 2018 at 07:15 PM.
Nov 25, 2018, 07:42 PM
Registered User
tspeer's Avatar
Quote:
Originally Posted by Lockey
Now theres an idea

Now whilst that would give it more lift at the front (I think) would that mean the CG would be further forward or further back ?

Lockey
The c.g. would need to move forward to maintain the same stability.
Nov 25, 2018, 07:44 PM
Registered User
tspeer's Avatar
I suggest putting a flap on the canard, made from, say, aluminum from a soft drink can. (Or, since you're Australian, a beer can.) That can be bent to change the pitch trim, without affecting the stability.
Nov 25, 2018, 08:03 PM
Careful,.. confident,.. CRASH!
Dukejet's Avatar
Good show Lockey! What nose dammage? .....lol..
Mate, you only have a flat wing on this one? No KFM2?
This will only create lift at a high alfa attitude??
I would have a KFM2 or 3 on this little gem.
Try moving the battery around every time you get on the ground. You'll get the sweet spot.
Nov 25, 2018, 08:20 PM
Tony Audsley Retired Locksmith
Lockey's Avatar
Quote:
Originally Posted by Dukejet
Good show Lockey! What nose dammage? .....lol..
Mate, you only have a flat wing on this one? No KFM2?
This will only create lift at a high alfa attitude??
I would have a KFM2 or 3 on this little gem.
Try moving the battery around every time you get on the ground. You'll get the sweet spot.
I need to make a little mod to the fuz to allow me to get the battery further back (have changed this on the plans for future builds)

Where would you start the KFm2 Duke ? remember the wing goes right forward to the front .. sort of .. I guess it would have to go there too .. ADDING MORE WEIGHT TO TH FRONT
Nov 25, 2018, 08:46 PM
Registered User
tspeer's Avatar
Quote:
Originally Posted by Lockey
I need to make a little mod to the fuz to allow me to get the battery further back (have changed this on the plans for future builds)...
A canard will move the neutral point forward, so you don't need to move the battery back. And the leverage the canard has for pitch trim would give you back lots of elevator authority. It'd be an easier modification than hacking the fuse to move the battery.

If you want to be sporty about it, you can start with a large canard and then cut it down to where the plane flies like you want.
Nov 26, 2018, 12:42 AM
Tony Audsley Retired Locksmith
Lockey's Avatar
Quote:
Originally Posted by tspeer
A canard will move the neutral point forward, so you don't need to move the battery back. And the leverage the canard has for pitch trim would give you back lots of elevator authority. It'd be an easier modification than hacking the fuse to move the battery.

If you want to be sporty about it, you can start with a large canard and then cut it down to where the plane flies like you want.
Thanks tspeer, I might give it a try later but have already done the mod this morning

Lockey
Nov 26, 2018, 12:56 AM
Tony Audsley Retired Locksmith
Lockey's Avatar
This was my Gripen with canards, very similar size to the sea scout, this flies great with the canards about 3 degrees positive incidence (up at front) but they are also switch optional linked to the elevator

Lockey
Last edited by Lockey; Nov 26, 2018 at 01:04 AM.
Nov 26, 2018, 11:13 AM
Careful,.. confident,.. CRASH!
Dukejet's Avatar
Just go with 40% of the cord measured at the root and the tip.
Canards look cool nut will not get the main wing any lift..... just my 1.5 cents....
Nov 26, 2018, 11:55 AM
Registered User
tspeer's Avatar
Quote:
Originally Posted by Dukejet
Just go with 40% of the cord measured at the root and the tip.
Canards look cool nut will not get the main wing any lift..... just my 1.5 cents....
The issue is pitch trim. This is something Burt Rutan discovered with his first canard homebuilt, the Variviggen. He built it with both canard and trailing edge flaps. He expected to use downward deflection of the trailing edge flaps to give more lift for landing, and to use upward deflection of the flaps to lessen the wing camber and reduce drag in cruise. Instead, what he found was he got a lower landing speed with the trailing edge deflected up, and he got better cruise performance with the trailing edge flaps deflected downward. The reason was the pitching moment from the flaps deflected up allowed the canard to rotate the plane to a higher angle of attack, and the higher angle of attack provided more lift than was lost from the flap deflection. When he deflected the flaps down, the resulting pitching moment had exceeded the canard's ability to raise the nose to the angle of attack he needed for landing. In cruise, deflecting the flaps downward loaded up the canard and offloaded the wing, which reduced the drag of that configuration.

Lockey's problem is he is running out of elevator authority for pitch trim. And the more nose-up elevator he uses, the less lift the wing produces. If he uses a fixed canard to provide a positive pitching moment, he won't need as much elevator to trim. And when he uses a higher angle of attack in a maneuver, the canard will produce more pitching moment, so he won't run out of elevator as quickly.

This is why you so often see canards paired with delta wings. If you position the c.g. for good stability, the loss of lift due to elevator deflection becomes a problem. The canard helps compensate for that.
Nov 26, 2018, 08:05 PM
Tony Audsley Retired Locksmith
Lockey's Avatar
Thanks for the in depth analysis Tom, not sure I understand it but seems to make sense

Would you put the canards a little higher than the wing ? or on the same plane ? and what size?

Hey Duke .. Maybe canards AND KFm2 foil

Lockey
Nov 26, 2018, 08:15 PM
Tony Audsley Retired Locksmith
Lockey's Avatar
Hey Duke .. Maybe both canard AND KFm2 foil

By the way, before any more mods ... she weighs 400 grams before battery, with 1000/3s lipo just 500 grams

Lockey
Nov 26, 2018, 08:49 PM
Retired CAD guy
birdofplay's Avatar
IMHO
after that nose trick you don't seem to need any more strength in the wing area
as it held up well in the tennis courts.

It'll be bullet proof with the KFM.

I see mike is doing a new Canard awith a 47" span.


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