flaps, airbrakes and wheel on a Nimbus 4d

[luc chev]

Sorry for the trivial questions,...but:
When flaps are on on that sailplane, do the flaps go Up from the wing, or down? If they go down I think I have to mix with some up elevator..?

If I have only 6 channels on my radio, is it ok if I put the retract whell as well as airbrakes on channel 5, altogether

thx

[Wight]

Ok, flaps work as follows.

If you lower the flaps say 5-10 degrees, you increase the drag a little, however you increase the lift a LOT. This allows you to fly slower, and effectively lowers the stall speed of the glider.

If you lower the flaps a lot, say 45 degrees or more, you get very little increase in lift compared to the first scenario. However you get a LOT of extra drag. In this case, the flaps are acting like airbrakes. If you mix in a little "up aileron" (Ie both ailerons coming up maybe 15-20 degrees) with this flap setting, you get LOTS of braking effect, this is called butterfly or "crow" braking.

If you raise the flaps a few degrees, (not normally more than 10 degrees, usually less.) you DECREASE the amount of lift. However, this reduces drag also, so your glider will now go faster. This is a "speed" setting, and should obviously NOT be used for landing!

In my experience, you need DOWN elevator to compensate for flaps. (Tho this can vary from wing section to section, some need nothing.) Having inadvertently mixed "up" with flaps, I do NOT recommend it! It looks like that "cobra" manouvere the Russians used to do in Mig 29s at airshows.....

I would definitley NOT put the retract on the brake channel. A retract is up/down only, not halfway. Wheras you want to have a whole range of brake settings available to you. Also, you will want to adjust brake settings as you fly the approach. We don't want the retract wiggling up and down as you come in to land!

6 Channel should be ok tho. I'd set up as follows:
1. Elevator
2. Aileron (both servos)
3. Rudder
4. Brakes
5. Flap (both servos)
6. Retract + tow release. (These can go together of you require a release.)

If you have only six "sticks" but 8 or 9 "software" channels (Assuming computer tx.) the way Multiplex Profi Trannies have, you can seperate out the flap and aileron servos.....

Can I ask what size this Nimbus is??? I'm not trying to be cheeky, but if you're not used to flaps, isin't a scale flapped model with retracts a wee bit ambitious to start? I'm not being rude, I'd just hate to see you end up in an unfortunate situation with a big glass model....

[luc chev]

Thx for the info
Nope, you are not rude. I am an old experienced flyer, but mostly with props or turbines. I have a 2m50 thermik star 3 with flaps, but when in action, they are up and I mix some down elevator.
It still speeds down correctly the plane....
This Nimbus being a scale model, I wanted to know exactly how it should go; this is a 5m20 all GFK from Lenger (Germany). It is electrified, so you have to re-settle the 6 channels ( I have a T6XA only). 11 servos in it, including 4 for flaps and 2 for ailerons, 2 airbrakes, rudder, elevator, wheel + motor. That's why I proposed to put wheel with airbrakes together (on channel 5) for the final approach (I don't expect to have anything proportional at that time). Of course I plan on the first flight to test well high the flaps (proportional, channel 6, mixed with elevator) and quickly the airbrake-wheel also.
You can have a look at my site (sorry in french, but with a lot of pics and some videos).
http://www.geocities.com/Colosseum/Game/1089/

Give me your comments. I apreciate

[alibodin]

If you can afford a model of that size and complexity it would be worth considering a decent computer TX to control it properly. 7 channels at least you would need more maybe with all the things you have on the model.

A

[Wight]

I have to agree with Albodin. If you're plowing this much money into the airframe, a radio upgrade would be an idea? (And it'll be good for all those other projects too!)

Ideal would be:

4 seperate channels for all four wing surfaces.
Elevator.
Rudder.
Brakes.
Retract.
Motor.

i.e a 9 channel set with full mixing. Really to get the full performance out of this kind of model, you need a full-blown trannie....

Regarding flaps, yes you have to mix down elevator if you reflex flaps (move the flaps up) but you may need even more down elevator if you apply downward flap. It might not seem to make sense, but believe me that's how it's always worked in my experience!