Spoilers on a Delta wing?

[johsan]

Am flying a Electric simple flat Delta wing and Am trying to find a way to slow down the speed when landing. High Alpha works but it's not easy to have the right combination of thrust and alpha.

What would be the effect of putting spoilers on a Delta Wing?
Is there any other way to slow it down?

//Johan

[Tom Harper]

johan.

I think spoilers would just make it drop faster. Maybe a split flap on the underside of the wing would help.

[Ollie]

I agree with Tom's solution.

Also consider practise flying landing over and over again. Then maybe you can fly the best combination of thrust and alpha. Build on flying skils rather than spoilers. Think differently.

[jamessimon]

I agree with Tom. I don't think you want to reduce lift, as a spoiler would. That would steepen the approach but not necessarily slow it down. I'm thinking you want to add drag and maybe get some more lift too so you can fly slow. That sounds like flaps to me.

Pitch control is going to be the issue with flaps on a delta. The nose must stay high. If the flaps give a big pitch moment you could have problems.

You might consider using 2 servos on each wing so that you could make a "crow" configuration like they do on sailplanes. This would allow you to add drag and control pitch too. It will need a pretty complex radio though.

An alternative would be leading edge flaps. Would be strictly test pilot stuff. Might be fun though.

[johsan]

Thanks for your input.

What about putting a canard wing with flaps in front of the main wing.
The canard would have a little higher AoA(Angle of attack) or even be movable (without flaps).

(My simple plane is my own construction and could easy be changed)

//Johan

[Ollie]

The solution with low AOA and slow flight is reduce wing loading and higher aspect ratio. A delta with low aspect ratio is a bad wing lift efficient at low speed and high AOA. It is a flying brick (SST or space shuttle Discovery). Consider a parachute rather spoilers. Consider flying into a soccer goal net.

[Jurgen Heilig]

johan.

I think spoilers would just make it drop faster. Maybe a split flap on the underside of the wing would help.

Split flaps don't work with a delta wing planform. High AOA is usually more than adequate to slow a delta down. Unfortunately up-elevons gives the wing more "flex" and reduces the max cl.

You can use an F-15 style speed brake on top of the wing. Properly dimensioned, this will help keep the wing at high AOA, with less up-elevons.

Alternatively you can use a split-rudder - like used on the Space Shuttle.

But the best solution: Practise makes perfect - get familiar with the way a delta handles.

:) Jürgen

[johsan]

Thanks all for your input.

I just came from another testflight, it's really fun to experiment with the capabilities of a Delta. I now fly it with a small part of the LE attached at 5 degrees down angle.
This sems to help and makes it more stable.

It flys good but when flying with in sidewind it makes a small rocking movement.
(like when moving the ailerons and the rudder in opposite direction on a non delta).
Am thinking of making a longer fuselage so the centered fin will be behind the TE.

When landing it's still hard to find the right balance between AOA and thrust.
To much thrust and the plane starts to gain altitude and to low and it lands fast like a brick. It would be interesting to know how real Delta planes are constructed to solve this. At higher AOA the speed goes down quickly could it be that a real plane calculates the airspeed and compensate with more thrust to find a balance that makes a good landing angle?

// Johan :)

[Jurgen Heilig]

Thanks all for your input.

I just came from another testflight, it's really fun to experiment with the capabilities of a Delta. I now fly it with a small part of the LE attached at 5 degrees down angle.
This sems to help and makes it more stable.

It flys good but when flying with in sidewind it makes a small rocking movement.
(like when moving the ailerons and the rudder in opposite direction on a non delta).
Am thinking of making a longer fuselage so the centered fin will be behind the TE.

When landing it's still hard to find the right balance between AOA and thrust.
To much thrust and the plane starts to gain altitude and to low and it lands fast like a brick. It would be interesting to know how real Delta planes are constructed to solve this. At higher AOA the speed goes down quickly could it be that a real plane calculates the airspeed and compensate with more thrust to find a balance that makes a good landing angle?

// Johan :)

A leading edge - permanently down - is only good for slow flight.

As far as AOA is concerned - as mentioned above - practise makes perfect (perhaps your throws are too big - have you tried some expo?).

:) Jürgen

[Mister UHU]

What about putting a canard wing
with flaps in front of the main wing.

The canard would have a little higher AoA(Angle of attack)
or even be movable (without flaps).

//Johan

A canard was my first thought, like the Eurofighter.

You could have an all moving one,
such as a carbon tube turning inside another carbon tube.

If you can carry the weight of another servo ?

Can you alter the CG position to make landing easier ??

Is the delta an own design trial ?
Or a proven design / kit from someone else ?
As there are plenty of deltas that fly fine, and land without problems.

[johsan]

Mister UHU:

Yes it's my own trail version of a delta and it flyes and lands better than I expected.
Am just trying to do some improvments while learning the basics of the delta wing.
As I understand it, it flyes on a vortex ontop of the wing. Some way or another the vortex is created and as loong as it's there the plane flyes.

I found some interesting input about the Concorde, which says that when it was on the runway for takeoff the presure on the landing gear was actually increasing with the speed before takeoff due to a vortex building up. In the moment of takeoff the AOA is increasing and vortex is big enough for flying.

On a ordinary wing the landing gear presure is decreasing as the plane gains lift with the ground speed.

// Johan

[Sparky Paul]

Some deltas made from 1/4" foam board..
Based on Larry Renger's (SoCalGliderGuider) "Foam Fatale".
Leading edge drooped 1/4" at 25% chord..
The drooped plane would outclimb the non-drooped original, in the same air.
The canard was added just to do it later..
And pointed out the fragility of a canard.