I was asked a question by a club member .......... If a Delta wing needs or can benefit from Leading edge slats like the Mirage 2000 has!

Considering that the airfoil is a Reflex type (MH61 will be used).

Any comments suggestions appreciated.


captain_Yak!

Deltas don't need reflex sections, and will respond to L/e devices as any wing. See the A4 `Skyhawk' as reference.
Evan, W.B. #12.

I must add that the model has no tail .......... and some reflex might be required???

Just asking.


Regards

Captain_Yak

There is a good book called, I think, " Riding the Dragon". About test pilot's exploits. Fellow flying a Vought Cutlass,Which was plagued with mechanical problems, had the hydraulics for gear and slats quit. Had to pump them down with a jack. With the long nose gear, had to get the slats out to get the nose up high enough to land on all three wheels and not just the nose gear. Said his pump arm was like Popeyes. It's a good read if you can find it. Also a good artical on test flying supersonic props on a P 47 Thunderbolt in a terminal velocity dive at full throttle. Talk about pucker factor.

By `no tail' I take it to mean no horizontal tail. No, pure deltas do not need reflex. This has been known in modelling circles since the early `60's when much delta experimentation went on, both for aerobatics and pylon racing. Any symmetric (uncambered) foil will do, with just enough thickness to hide the radio gear.
Evan, W.B.#12

Actually the deltas DO need reflex just as any other flying wing does. Pimmnz, I think you're missing out on that due to the fact that those symetrical sections would have just used a little "up" trim on the elevons. That up trim IS the reflex but it just doesn't always show as that on the plans.

But if the airfoil being used does have some camber then the amount of reflex at the trailing edge needs to be increased.

I wouldn't bother with slats on a model delta. Slat design needs to be done just right or it will either have no benificial effect or may even hurt things. And the more extreme delta shapes tend to have a very strong vortex flow over the leading edge that supports a highly delayed stall in any event. By extreme I'm talking a leanding edge sweep that exceeds 45 to 50 degrees. As the leading edge sweep gets to be less than 45 degrees the wing starts to act more like a swept and tapered flying wing than a delta and doesn't have that same tolerance to extreme angles of attack.

I was allways under the impression that reflex on a delta or flying wing is what decalage is to a tailed plane. The more nose heavy the more decalage or up trim or reflex you need. My old Hustler from the 60s has a flat bottomed wing with a lot of reflex built into the trailing edge of the wing before the ailerons. My Pizza box and other wings of the same configuration need at least a few degrees of up elev. or reflex, depending on what you want to call it, just to fly with a few degrees of incidence in the wing. As you all know, no plane will fly with a 0 angle of attack, at least not for long.

Sorry Bruce. I was typing while you were posting. I'm to slow again.

Umm, yeah, I guess I was trying to say that you don't need a special reflexed airfoil to do the job. If my 363 has some `up' trim when I'm flying it I can't detect it from the position of the elevons on the ground, but then I do have the cg back a bit so it could be flying nose up a bit, well who knows? Any way these things do deliver huge fun for little complication and with minimum power too.
Evan.

I must mention of the Hustler that you could hold full up el. on takeoff and it would raise the nose up to about a 25 degree angle and would hold that angle till it reached takeoff speed much like a 747. I think it has a lot to do with the airfoil shape. This has a very sharp leading edge at the root and very blunt at the tips.

A
Big "Thanks" to all! [8D]

Very constructive and helpful information.

Captain_Yak!

Not a delta with extreme LE sweep but a flying wing/tailless aircraft, the Shuebeler Vector DF has LE slats that help lower the stall speed for landing and improve low speed handling over all:
http://home.vrweb.de/~schuebeler.impeller/vector_e.html

Strictly speaking those are not slats on the Schuebeler Vector II, as they don't open up a slot - a gap for airflow. They are drooped leading edges (or leading edge flaps as they are called on the website).
Slat / Slot design is quite critical as Mr Mathews says.

Anyone know of a good website that shows exactly how to design and make Slats that produce accurate Slots?

Ah good catch. You are correct. I would think that slats would be great for scale applications but they do sound difficult to do right.