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chrisg
05-24-2011, 09:44 PM
Does anyone have any experience with increasing the flap chord on a short wing? I know a lot of experimental cubs have flaps that are 2" or 4" longer, but I haven't really heard anyone talk about the actual benefits? What kind of STOL performance increase might one expect from extending the flap chord on a pacer?

Steve Pierce
05-24-2011, 10:06 PM
Never seen an extended flap cord approved on a Super cub or a Pacer but I have seen them installed. Not sure if they just create more drag or more lift but I think the Piper flap is more of a drag device. I saw these in Alaska. They are being tested for a Super cub STC. They are split flaps fashioned off a Otter. They create a flatter approach so you can see but are exhibiting a bit of tail shake. They are designed to bolt into the stock hinges and actuate with the existing parts. Hope it gets STC'd on the Super Cub and then maybe the Pacer.

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chrisg
05-24-2011, 11:45 PM
Yeah, I heard that Doug Keller was working on these and recently saw these pictures....very cool looking!

Throttle Pusher
05-25-2011, 05:07 PM
Great!:new_let_it_all_out: Something else Im going to want!!:banghead:

Those are the same style as you will find on jets and should give you more lift as well as drag.

Ken

Stephen
05-25-2011, 07:02 PM
How much do they weigh?

Steve Pierce
05-25-2011, 07:10 PM
About 10 lbs. more than stock.

Stephen
05-26-2011, 08:27 AM
Steve, did you talk to the pilot who flew with this flap?

You said it gives a flatter approach, are there any other low end performance changes? One would think it might give a slower and/or a more stable approach and a lower stall speed. It sure looks interesting.

Steve Pierce
05-26-2011, 08:32 AM
I didn't get a chance to fly it but several people I know did. They all commented on the flat approach and how they could land short and slow with out the nose high attitude and being able to see their landing spot. Paul Claus flew it and then his Super Cub. he flew his SC 2 miles an hour slower on the same GPS but with a much higher angle of attack.

dplunkt
05-26-2011, 09:41 AM
Chrisg,
I am thinking about sullivans wings and they are provided a little long in the cord so you can trim them back. I thought about leaving them and extending the cord on the flap and aileron an inch or so. My thinking is it would increase the effectiveness of both.

The downside is this; on the extended flaps I've seen on Cubs there is an adjustment to the hinges because the larger flaps will put more pressure on the hinge as the leverage point changes. So, I would be careful how much you extend the flap cord.

Dan

Stephen
05-26-2011, 10:15 AM
Chrisg,
I am thinking about sullivans wings and they are provided a little long in the cord so you can trim them back. I thought about leaving them and extending the cord on the flap and aileron an inch or so. My thinking is it would increase the effectiveness of both.

The downside is this; on the extended flaps I've seen on Cubs there is an adjustment to the hinges because the larger flaps will put more pressure on the hinge as the leverage point changes. So, I would be careful how much you extend the flap cord.

Dan

You are correct that changing the flaps (or ailerons) changes the wing loads. I am starting the process of paying an engineer (DER) to calculate the torisional forces and loads to the spars when one moves the aileron outboard and increases the flap size. We know that it works as there are a number of flying examples. The short wing does not have a jury strut; therefor the effect of these changes on the inboard spar also needs to be calculated. Unfortunately, Cub data is limited in being useful. I wonder if Piper had all this information when they mixed and matched their wing parts making all the variations of wings?

Thanks Steve for sharing this flap design, it is very interesting.

Steve Pierce
05-26-2011, 10:15 AM
You change the length of the cord on the ailerons and you get into a heavier aileron control input and you get into a possible flutter situation. Dakota Cub had to do a flutter test on their Super 18 to Part 23 standards when they got their type certificate and stock it was on the verge of not passing.

highroad
05-26-2011, 12:19 PM
Really hoping Doug K. can pull of this flap design and get us shortwings in the loop. I feel like the little flaps on my Pacer make a difference in lift, and obviously drag. The take off roll is significantly shorter with flaps on my airplane.

Grantmac
05-26-2011, 06:54 PM
I think the really exciting aspect to a flap design like this is in the partial settings for take-off use. A double element flap design like that is very efficient when lowered enough to get air flowing through the slots.
Of course being able to expose a virtually flat plate for approach control has its pluses as well.

-Grant

avcan
05-27-2011, 02:27 AM
When I did the Sullivan wing extension, I was sorely tempted to "quietly" move the ailerons outboard. I resisted the urge, and am pleased I did so. While the wing extensions are awesome, there is actually quite a lot of flex now in the wing if you hold the wing tip and flex it up/down or twist it. I'm sure moving the ailerons and flaps outboard would add excessive loads on the wing unless it was strengthened substantially and maybe added jury struts.