Airfoil selection for "FunJet" like design?

[wim5150]

Working on a Funjet/Twinjet/Microjet LIKE design and not sure about the airfoil. Want something that's fast and aerobatic. The design will also have a functional canard.

PW51 a good choice or is there a better one?

[vintage1]

Dunno, but put some reflex in unless the canard is substantial, and possibly washout..but beware, these things are less than ideal when inverted.

Possibly a fully functional canard would actually perform a bit better, then use a fairly symmetrical section.

[wim5150]

Thanks Vintage. Yes, more symmetrical maybe a better choice.

[frank40]

Hi wim5150

looks like we got the same idea. I am building a plane that in time will bee redesinged to a funjet look a like. Well allmoste, I whold like it to end up a bit more sports like and will be powered buy a 90 mm midi fan.

[Julez]

I'd take a PW 51.

http://www.rcgroups.com/forums/showthread.php?p=6378115&highlight=pw51+airfoil#post6378115

[BMatthews]

For high speeds a thin symetrical will be fine and will provide the best performance for this type of model. The elevons will require a little upward reflex to achieve stability for the first flight. Adjust the elevator trim to find the happy spot from there. Finally you can then adjust the elevon clevises to retain the final amount of reflex and allow you to return the elevator trim setting to zero.

On models of this sort unless the canard is quite big and located well out front the chief contribution by the canard is to direct air over the wing during high angle of attack operation like when flying slowly or when pulling a lot of G at high speeds. Note how the canards on all the modern fighters using them place the canards up higher than the main wing or angle them up to achieve the same effect? The canards in this case are acting more as a wing slot than as flight controls. If that is the style you're going for then I think you're going to find that they don't make good flight controls and also they are inside to outside loop specific. They'll help for insides but do nothing for outside loops.

[Mayrit]

Hi, We were thinking of same design for slowing down the funjet :) but at the end another concept was chosen so we didnt build the canards and test them...

[frank40]

Wow.... thats a nice plane ;) What are the plan? size, fan or prop.???
By the way I am going for speed. I am thinking min. 50" wingspan and about 1.5KW. :eek:

[BMatthews]

For ultimate speed a pusher prop is far from the best solution. Granted the model may look good but a conventional puller prop will be faster. Not to mention less noisy. Operating in the wake of the wing and fuselage generated turbulence does not make for great prop performance.

[Kristian k]

For ultimate speed a pusher prop is far from the best solution. Granted the model may look good but a conventional puller prop will be faster. Not to mention less noisy. Operating in the wake of the wing and fuselage generated turbulence does not make for great prop performance.

Really? I thought the less obstacles there are in the path of the props generated "wind" the less turbulent the air would be and therefore the prop would be more efficient and less noisy... is it because the prop needs to suck the air from somewhere? and then the whole body is in the way? how come it works better in puller configuration?

[BMatthews]

Props only act like fans when on the ground. Once in the air they act more like small wings to lift the plane forward through the stationary body of air. So the cleaner the air they are biting into the more effective they are.

You'll notice that there's been precious few full size or even model racing designs that use pusher props. And the ones that use them generally don't do well. This is why.