Split Flaps

Have noticed looking back through the years , There has been a lot of discussion about mounting flaps on cubs that do not have them. Have always wondered why nobody considers mounting split flaps such as these. Much easier to add ,no internal wing mods required ,less than 20 pounds total additional weight and can guarantee they will work just as well as rear spar mounted flaps . Also understand it would have to be an experimental category cub.

they probably work better.

What do you expect from the flaps? Just drag or would you also like to have a considerable amount of lift? Split flaps can provide a small amount of lift, sometimes, but usually mostly drag.

Maybe contact the owner of N100DY and ask him how well they work?

My understanding is that split flaps work wonders on landing, but might not help as much for take-offs because of extra drag. This all based on anecdotes, though.

I'd sure like to know.

Then I had another idea--instead of split flaps hinged right at the front, put them on an arm so that they extend a bit below the wing as an independent airfoil. It would be more like a slotted flap, but below the wing instead of behind.

I'm strongly tempted to mount some sort of test device in the back of a pickup and test different configurations at highway speeds.

Vic

that is his airplane

tempdoug said:

that is his airplane

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Oops! I don't get out much....

How about split Gurney flaps at the trailing edge? Figure a way to have them open and close at will.

Gary

I put a row of VG's on one of my 110" flaps on the top and so they tuck behind the wing when retracted. Did absolutely nothing. Still there as I have been slack about taking them off. You would think that after 80 landings I would have noticed something different about that wing!

Any more details on how they work? I would like to see how they are mounted and linkage to deploy them, might like to try something like that.

BC12D-4-85 said:

How about split Gurney flaps at the trailing edge? Figure a way to have them open and close at will.

Gary

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I've fiddled with that idea, too. My concern was the potential for flutter. Loose tab-like objects on an airfoil send chills up my spine.

I tried a 40" length of a fixed gurney flap. It did provide a very slight amount of lift. Not enough improvement to make it worthwhile in my opinion to place it full span.

I'm in the slow process of building a F22 Taylorcraft, and have considered going with a split flap like the Auster. From all the research that I've read, the split is a little better than the plain flap on the 23012 airfoil.

A little more complex than the OP's system. Mongo not smart enough to change .pdf to .jpeg

View attachment J5F-Flap-arrangement.pdf

skywagon8a said:

What do you expect from the flaps? Just drag or would you also like to have a considerable amount of lift? Split flaps can provide a small amount of lift, sometimes, but usually mostly drag.

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I put the flaps on expecting to get a lot of quick lift at take off ...... I got more than was expected, shorten my take off run Considerably, shaved another 75 feet off of my ground run. I rotate now at just over 30 at around 125’.without the flaps use to have to do it at 40 at around 200’. Also, lowered the stall speed in level flight by 7 miles an hour . Approach now it’s at 35 mph comfortably to where I used to have to do it at about 42 comfortably . Touchdown now it’s just under 30 to where it used to be in the mid to high 30s No wind, All this as well as lowering the nose on approach!
No doubt split flaps are not as efficient at making lift as regular flaps or especially a slotted flap, but they are an exceptional add on considering the lack of complexity and weight.
Like has been said before about flaps, all an airplane in ground effect needs is a way of deflecting Air flow towards the ground efficiently. Split flaps do that very well, and they do a fair job at producing lift out of ground effect.
Again, seems to me that the guys with the experimental Cubs that have no flaps could really do themselves a favor by considering this easy add on .Don’t have to tear into the wing , They mount on the rear spar attach at the fuselage as well as the rear lift strut attach and lightly loaded mid span at the Jury strut attachment.
Will also say I started out with flaps half as big as what’s on it now 4 feet long by 12 inch cord they worked so good I increased to 80 inch long 12 inch cord and they work even better.

sburg58 said:

Any more details on how they work? I would like to see how they are mounted and linkage to deploy them, might like to try something like that.

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Used 2x2 angle bolted to the rear spar and rear lift strut attach points as hinge mounts . Also because the jury strut attach is inline with the other 2 attachments due to all being mounted to the rear spar, made a hinge there as well. Although it takes little if any loads at all.
You can see in the photo that I mounted the attachment for the cable to deploy it at 4 inches off of the hinge point of the 12’ cord. Slaved it to my belly flap, and then they are both deployed by a standard piper warrior 3 position flap Handel.
The flap it self is made from 1 inch diameter 058-6061 tubing with half-inch holes drilled for 1/2” 035 tubing for ribs .
Covered with oratex.

P

A couple more photos

flyrite,
I just noticed that you have the Curtis pusher look alike. Since you have a pusher prop which sucks air over the wings your characteristics are very likely to be much different than a Cub configuration. What may work well for you won't necessarily work well on a Cub. That fact may actually contribute to the excellent result that you get with the split flaps.

Skywagon You might be right, I would have thought though that having the prop blast on the flaps would actually give you better performance but I may be wrong .

I've flown several different airplanes with pusher props Seabee, Lake, Colonial Skimmer, Lane Riviera, Volmer sportsman and Cessna Skymaster. They all have characteristics which are peculiar to their design that can be attributed to the pusher prop. The prop actually sucks the air from the wings into itself with totally different result from being blasted from a prop which is way out in front of the wing.