Oregon180 wrote:....in my experience the downsides tend to be exaggerated on the Internet.

Yes, but in my experience the up sides tend to be exaggerated also.

I think the only way to solve this for yourself is to take them off. If you find the plane works better for you with them off then leave them off. If you liked it better with them on just get them reinstalled. The nice thing about the Knots 2 u is you can take them on and off in about ten minutes. Let us know which you like the most.
KenW

I have had two 182B's and neither of them had a stol kit or flap gap seals. Now I have a 56 model that came with flap gap seals and no stol.

I installed a sportsman stol with aileron gap seals on the 56. Still have the flap gap seals.

I would never in no way ever have flap gaps seal installed and I feel the same about spending the time to remove them either.

Leave them on.

tim

If you fly your downwind at 80, base at 70, final at 60 and try to time your flare over the fence to hit the numbers and can live with floating in ground effect, flap gap seals are fine.
If you are into stabilized approaches with indicated airspeed below what your gauge will accurately read, using throttle to control your decent with little flare and no float, then I don't think you want flap gap seals.
But I have been drinking coors light and I'm due for another

hotrod180 wrote:

Cary wrote:.......Whether you would notice any measurable difference in your 180 if you yanked your flap gap seals, I can't say. But if you're satisfied with your airplane's performance now, why muck with it?

Because I can.
If "good enough" really was good enough, we'd still all be flying 65 horse Champs & Cubs-- and there'd be no 180's with the ponk 520, 185's with the 550, stol cuffs, VG's, or any other mods intended to improve performance..

That's why I didn't say "good enough"--I said "if you're satisfied". But if they're easy enough to yank, then do so and make your own comparison for your airplane. If then you're not satisfied, screw them back on, or rivet them, or whatever it takes--heck, I'm not a mechanic.

182 STOL driver wrote:NO flap gap seals for me ! I wouldn't pay the mail / UPS charges to get any .KILLS 20% of your lift on takeoff -lengthens take off run . If Cessna thought they would make airplane faster or better they would have added them at factory .Aileron gap seals are different story -Have those to work with my SPORTSMAN STOL !

Incidentally, Cessna did install flap gap seals at the factory on the last run of 206s, because they do make the airplane faster. Just sayin'.

Cary

A1Skinner wrote:

182 STOL driver wrote:NO flap gap seals for me ! I wouldn't pay the mail / UPS charges to get any .KILLS 20% of your lift on takeoff -lengthens take off run . If Cessna thought they would make airplane faster or better they would have added them at factory .Aileron gap seals are different story -Have those to work with my SPORTSMAN STOL !

Very interesting post. Where do you get the 20% figure from. In the post above yours we have a guy who repeatedly took them on and off for comparison and every time got better numbers with them on.
I enjoy these type of threads, seems to be one of the topics where engineering and real world don't line up very well.

Lower your CESSNA flaps and look at the end -looks like a Airfoil -now look at air flowing below wing at the area -it has to go over flap to produce LIFT. Best lift to drag ratio is at 17 degrees down( lower aileron at max and match) Wing on typical CESSNA 172-180-182 area is approx. 182 sq. ft. of which flaps is approx. 14% - of lift . If you have flap gap seal this amount of air or lift is going off the back with no lift.

182 STOL driver wrote:.... . If Cessna thought they would make airplane faster or better they would have added them at factory .Aileron gap seals are different story -Have those to work with my SPORTSMAN STOL !

The "if they were better, Cessna would have added them" argument could apply to aileron gap seals too.

hotrod180 wrote:

182 STOL driver wrote:.... . If Cessna thought they would make airplane faster or better they would have added them at factory .Aileron gap seals are different story -Have those to work with my SPORTSMAN STOL !

The "if they were better, Cessna would have added them" argument could apply to aileron gap seals too.

It could also apply to the cuff that they added on the later years. There is lots of upgrades that were done in later years to improve the airplanes.
I've never flown the same plane with and without flap gap seals. But I'd be willing to bet that many of us would be willing to add 50' of takeoff roll and get 4-5 mph cruise and 100+' fpm climb. Lots of places we are landing are in the mountains and climb rate can be just as important and getting off short.

182 STOL driver wrote:

A1Skinner wrote:

182 STOL driver wrote:NO flap gap seals for me ! I wouldn't pay the mail / UPS charges to get any .KILLS 20% of your lift on takeoff -lengthens take off run . If Cessna thought they would make airplane faster or better they would have added them at factory .Aileron gap seals are different story -Have those to work with my SPORTSMAN STOL !

Very interesting post. Where do you get the 20% figure from. In the post above yours we have a guy who repeatedly took them on and off for comparison and every time got better numbers with them on.
I enjoy these type of threads, seems to be one of the topics where engineering and real world don't line up very well.

Lower your CESSNA flaps and look at the end -looks like a Airfoil -now look at air flowing below wing at the area -it has to go over flap to produce LIFT. Best lift to drag ratio is at 17 degrees down( lower aileron at max and match) Wing on typical CESSNA 172-180-182 area is approx. 182 sq. ft. of which flaps is approx. 14% - of lift . If you have flap gap seal this amount of air or lift is going off the back with no lift.

So, with flap gap seals you are effectively eliminating your flaps? They no longer produce any lift? In which case you kill only 14% of your lift. I find it very hard to believe that a company designing a stol kit to get you off the ground shorter would kill all the lift produced by flaps. However I'm no engineer, just a farmer.

My FGS are by Horton. I called the factory and asked for tech help. They transferred me to Mr Horton, the guy who designed the Horton STOL kit. He told me to install a STOL kit (his naturally) and leave the FGS.

They did extensive testing of Cessna's with and without STOL and did the same testing with FGS and every combination of droop tips for the best overall performance. He said that if I were to take off the FGS it would be hard to tell the difference in landing distance. I believe him.

Tim

This is like the wheel landing/three point landing argument.
I put them on. No change to cruise speed or runway distance but noticeable climb rate improvement after a flaps 20 takeoff.

182 STOL driver wrote:Lower your CESSNA flaps and look at the end -looks like a Airfoil -now look at air flowing below wing at the area -it has to go over flap to produce LIFT. Best lift to drag ratio is at 17 degrees down( lower aileron at max and match) Wing on typical CESSNA 172-180-182 area is approx. 182 sq. ft. of which flaps is approx. 14% - of lift . If you have flap gap seal this amount of air or lift is going off the back with no lift.

With gap seals installed, the flaps are still increasing the effective camber of the whole wing when they are extended, so they still increase the lifting coefficient of the whole wing quite a lot, and the effective area of the wing to a very small degree. Losing the fowler component just makes them into a "barn door" type flap, which still greatly increases lift from the wing overall.

Yes, without the fowler slot they are producing slightly less lift, but nowhere near 14% less - probably closer to 1.4%... most of the extra life comes from the increased effective camber. But the centre of pressure would be in a different spot too. They would act more like a "barn door" type of flap, without the fowler component. That might result in a smaller pitching moment when flaps are extended, and less need to re-trim. It might also result in a higher nose attitude at Vso.

Terry wrote:If you fly your downwind at 80, base at 70, final at 60 and try to time your flare over the fence to hit the numbers and can live with floating in ground effect, flap gap seals are fine.
If you are into stabilized approaches with indicated airspeed below what your gauge will accurately read, using throttle to control your decent with little flare and no float, then I don't think you want flap gap seals.
But I have been drinking coors light and I'm due for another

What he said! Except I don't drink Coors.......

This is what it's about, NOT whether it'll take off shorter. If you fly the plane like the factory says, you'll never notice the difference. If you FLY the airplane like the STOL aircraft that it can be, you probably will.

And, Tim, Horton STOL kits are a waste of metal and labor to install. Install a Sportsman.

MTV

Any properly designed gap seal SHOULD provide some reduction in drag. Drag increases as a squared function of (a muddy mix of airspeed, dynamic pressure, Reynolds number, local velocity, density, etc.) Ten linear spanwise feet worth of a huge discontinuity and gap on the lower surface of the wing produces measurable drag. Smoothing this gap over will reduce drag to some measurable degree... or else a lot of very famous aerodynamicists have been scamming us for decades.

The number of places on a Cessna 100 airframe where they allowed gaps, discontinuities, angular changes, protrusions, and other drag-producing things to exist... in return for better production efficiency, cost and simplicity... is staggering. And there is a good reason for this, the same reason a pickup truck is not as fuel efficient or as fast as a teardrop shaped sedan on the same power.

Those same aerodynamicists proved that the Fowler Flap is a good thing at slow speeds. So having that smooth slot and airfoil-shaped flap is a good thing, especially in STOL oeprations. But IMHO many other factors are at play which can skew the results.

The trained aero guys can correct me if I'm wrong, but I'm guessing that there is also some combination of slot width, flap deflection, AoA, and other factors where "air leakage" and loss of "pressure" under the wing (because of the gap) creates a bigger loss than the Fowler Flap principle increases lift. If this is true as I suspect, then it would explain why some pilots in some airplanes using some techniques will swear that the gap seals increase climb rate and others swear it kills climb rate.

Any time you make lift you also make drag. So the amount of thrust you have determines how much you can overcome the drag. If you have more thrust than the next guy, you might be able to overcome the extra drag, and the extra lift shows up on the rate of climb indicator. Another guy with an identical airframe but a little less thrust might not be able to make as much use of the extra lift (from a certain gap seal configuration), and he comes back thinking that that particular gap seal configuration kills performance.

(For example, the Taylorcraft has a wing that can make a lot of lift, but the drag goes up quickly. So putting the 85HP engine on the T-craft allows a much greater improvement in climb than just that extra horsepower by itself should yield. Because the 65HP engine can't keep pulling that wing through the air for very long while it is making max lift. Anyone who has seen an old 65HP airplane take off and climb steeply, and then a few seconds later it almost stops climbing, is seeing this principle in action).

Point being, the flap gap seals will probably work one way in some situations (flap deflection/rigging, pilot technique, thrust, AoA, loading) and work differently in others.

One of the things I'd like to experiment with is a flap gap seal that opens up the slot as the flaps are extended, but closes the gap at cruise speed.

mtv wrote:

Terry wrote:If you fly your downwind at 80, base at 70, final at 60 and try to time your flare over the fence to hit the numbers and can live with floating in ground effect, flap gap seals are fine.
If you are into stabilized approaches with indicated airspeed below what your gauge will accurately read, using throttle to control your decent with little flare and no float, then I don't think you want flap gap seals.
But I have been drinking coors light and I'm due for another

What he said! Except I don't drink Coors.......

This is what it's about, NOT whether it'll take off shorter. If you fly the plane like the factory says, you'll never notice the difference. If you FLY the airplane like the STOL aircraft that it can be, you probably will.

And, Tim, Horton STOL kits are a waste of metal and labor to install. Install a Sportsman.

MTV

I did install a sportsman and I love it. I left on the FGS

Tim

I've been talking this flap gap seal removal thing over with a skywagon-owning buddy of mine. I happened to be looking at his airplane today with him and we noticed a whole bunch of #30 sized holes on the bottom of the wing at the forward edges of the flap coves. His apparently had a set of flap gap seals in the past which have been removed-- all prior to his ownership. The holes are not as obvious as you might expect-- neither he or I have ever noticed them before. Since they just go into sheet metal (they are aft of the rear spar), other than cosmetics there doesn't seem to be any real need to fill the holes with rivets plugs or whatever.

FWIW I've pretty much decided to remove the gap seals. Don't want to waste any of the good flying weather we've been enjoying around here, so it'll be happening during our next rainy spell.

So if your friend has a C180 without FG seals why don't you fly it and compare performance numbers?

As a kid, I never liked letting others play with my toys, and as an adult I still fell the same way. Apparently he does too-- he never offered and I wouldn't ask. I have ridden in his 180 several times, and it comes right off the ground at least as well as mine and clips right along at cruise also. So I'd have to say that removing the FGP's didn't hurt performance any.

hotrod180 wrote:As a kid, I never liked letting others play with my toys, and as an adult I still fell the same way. Apparently he does too-- he never offered and I wouldn't ask. I have ridden in his 180 several times, and it comes right off the ground at least as well as mine and clips right along at cruise also. So I'd have to say that removing the FGP's didn't hurt performance any.

He doesn't trust your competency while you are in the right seat and he's in the left? Or vice versa? I've got several friends that I've switched seats with in my plane that have 180 time. It's actually nice sitting on the right while someone else flies. I actually like the extra 5mph in cruse.

Let the drilling begin

I am almost 70 years old so I no longer have time to do stuff that offers questionable results

tim