Slotet Wings: Nose and Aileron/elvons

[HugePanic]

I plan to build a allround-plane.

The plan is a delta with brushless motor that has a large flight envelope.

I want it to be fast, but also be able to fly slow without any bad behavior

I want to use slots at the LE of the wing, and also at the elvons to get a large ca_max at high AOA und prevent tip-stals.
Strakes are also planed...

Here is my Problem:
I can find masses of data about slats and fowler-flaps, but nothing about slottet-ailerons/elvons or just slots at the LE.

I am building a plane with no tail, so i need to know if i can control the cm that is resultet by the slots...

Does anybody has experiences that could help???

I plan to build a scratchbuild-foamy, span under 1m.

thx

[MarkusN]

I don't think that delta and slots will mix well. On a delta you want the flow to detach. (Slots are devices that are used to prevent this.) The conical vortex over the wing is what delivers lift up to high AoA. Combine a stron motor with a delta wing and you have an aircraft with a wide flight envelope.

Same thing with the slotted elevons. I am really not sure if they work as intended on a delta.

Any Cm data that you might find is valid for near-two dimensional flow. Applicability for the high lift situation on a delta is doubtful.

The Abbot and Doenhoff contains some data on slats and slotted flaps. All checked at full-scale Re, of course.

[BMatthews]

A delta wing with a strong sweepback angle forms a strong vortex flow around the leading edge. No need for slots.

For high speed you pretty much want a symetrical and fairly thin airfoil. For low speed just keep it lightweight and use a sweep back angle for the leading edge greater than 50 degrees. Or if you're using LEX strakes then you can do a double delta planform with more like a 40 to 45 degree outer section leading edge sweep.

[HugePanic]

my idea was sth like this...

fuselage is solid foam, wing is two layers of foam with carbon-reinforcement.
(flat plate with chamfered LE)

slots at the LE and elvon to improve slow-speed-flying....

i am not sure about the rudders influence with the wingtip-vortex....

maybe i build it without slots/slats and try to improve it...

[BMatthews]

That is more of a flying wing with a little bit of sweepback. To be a proper delta wing it would need to be much more extreme a taper.

Slots are also hard to build in model size and ensure that they work. Just because you put a slot there doesn't mean that the air will see it the way you think it should see it.

Again, you're far better off to build it clean and with very little camber in the airfoil for fast flying and then make it light so it'll fly slow.

This will be more a flying wing than anything else. Also it is very close to being a "plank" style of flying wing since there is only a little sweep. This means your airfoil will be more critical. You want to use either a symetrical airfoil and just reflex the elevons a little or you want to use a low camber plank flying wing airfoil.

If you choose to use a "lifting" airfoil I'd suggest the HS 2.0/8.0 . Profili2 has this airfoil available. It's been used on some fast thermal and slope style gliders.

[JetPlaneFlyer]

Leading edge slots need to be shaped very precisely to turn the air round the leading edge of the wing such that it remains attached to the upper wing surface... this would be difficult to do with all foam flat plate construction. Simply cutting square edged slots into the wing will have a negative effect in all flight regimes.

The slots in front of the wings control surfaces on some full size aircraft are to make the flaps work better. You see this on many airliners but the slot is only there when the flaps are deployed, not for normal flight. They effective only when the flaps are in the extreme 'down' position. Again the shape is critical and would be hard to do in flat plate foam. In any case as you are building a flying wing then you wont have flaps and when you are flying slow then the elevons would be deflected 'up' not 'down' so the slots would be ineffective even if they were done correctly

[Daddio]

There's a lot of truth to - models just don't fly the same as their full sized cousins - something about Reynolds numbers and a bumblebee really can fly. ;-)
There's nothing at all wrong with tinkering, though; go for it!
To really see the efffects your looking for, I'd suggest scaling it up as much as you can afford.
If you just want to get airborne, follow BMatthews advice.
Have fun and let us see what you build!

[HugePanic]

...Have fun and let us see what you build!


I will let u see what i fly, not what i build...
i am currently in a stage of development.

Stage 1:
Fly without any fancy slots-stuff..

[BMatthews]

Well, if you're making it to learn with then I'd suggest you make up the wing with a separatly attachable leading edge so you can swap out the front inch or so for a regular leading edge. One with slots or one with whatever shape you want. That way you're altering one thing while keeping the rest of the model the same. That old truism about experimenting at work, only change one variable at a time or else you don't know what works and what doesn't.