Install the Robertson kit if you really want STOL performance. I use 50 KIAS for final, that is the Robertson book speed. Taking off, she will get into ground effect before much of an airspeed reading. Of course, she won't climb until you get some speed and clean up. I have the Flint tips, also makes a difference.

In my experience, flap gap seals on a Cessna are a NOTABLY bad idea. Cessna 170, but the wings are virtually identical aerodynamically through many if not most of the Cessnas.

Why the hey would you put Gap Seals on a Fowler Flap installation???? Duh.

MTV

IF they did anything for reducing drag, you'd want gap seals in order to clean up the wing for reduced drag during all the times you did not need the Fowler flap effect.

But the benefit for a Cessna wing where the flap already seals well to the top trailing edge will likely not be very significant. And the negative effect on the slot effect has been well understood already.

So IMHO the task is to make sure the flap seals against the wing, which will give the majority of the benefit (from a SEALING standpoint), and forget the small benefit of FAIRING over the discontinuity if you plan on any STOL work.

After reading about the 206 crash at Merrill I have a couple of questions for the 206 expert guys.
I have found that with my wings (Sportsman, wingx, flap gap seals) I do not care for the takeoff performance at flaps 10 and I can match or beat the performance with flaps 0. Flaps 20 takeoff performance is as it should be. That guy was trying flaps 30 and stated that was normal? I haven’t tried a flaps 30 takeoff and have never heard of any one using 30 for takeoff.
I would like to experiment with what kind of short field distance and angle of climb I can get with the PT6-206 and was thinking I may have the HP to do a flaps 30 takeoff and get some blow down lift through the flaps.
Does any one ever use Flaps 30 for takeoff and when would you?
I do not have any experience with the cargo pack and would like to know your opinions on STOL performance with it. Flaps 10 limitation? Once again Im thinking of the PT6-206 and want the maximize the carrying capacity and STOL performance.
I know that removing my gap seals would improve the flaps 10 performance and I could go and try some empty weight flaps 30 takeoffs to simulate the HP to weight ratio.

With the 206's that we ran in real short places, we used 30 degrees all the time! Started the roll with flaps.
185's used all the flaps to get in the air, and then used the flaps with the button pushed in to go fast enough to fly.
Sealevel and 30-60 degrees f, only used 20 on the pavement.

GT,

On Stene's site they list Vx climb for the 180/182/205 with use of 30 degrees of flaps.
http://www.steneaviation.com/performanc ... =5~5~11~11

I had Knots 2U flap gap seals installed on my 1963 P172D, several years ago. I did not notice much of a difference in take-off distances, nor did I notice much of a change in my ability to make a steep approach. I did notice an increase in climb rate (flaps up), although I haven't actually measured it--more of a seat of the pants thing. If I take off with any extended flaps, it's only 10 (20 is a bit too much, and I can't go in between), and then I raise them as soon as I can, because the Vfe on my airplane is only 100 mph/87 knots, so most of my climbing out will be with flaps retracted. But I did get a solid 6 knot increase in cruise speed. In my poky little airplane, that's significant, so I'm not sorry I had them installed.

Cary

Hi Van, what did you decide to do? leave them on or take them off? As I'm sure you've seen I have a 182P project. Sportman STOL just installed, wing X is next. I'm debating flap gap seals. As you said, the company claims 50-100 a min climb improvement which is pretty enticing. I'm operating on 2100 feet of pavement so "short field" performance isn't a must, but always nice...

This is the third or fourth time MTV and I have agreed on this subject of flap gap seals on Cessnas.

I have a 170-B with a Horton Kit on the leading edge and the aileron seals. The guy I bought it from in McCall Id. said that he was told do NOT put on the flap gap seals if you are going to be flying in the back country where you may need a steep approach.

Well, I had to learn the hard way. At least my AP-IA told me to buy the Knots 2U kit and throw away the Horton set that came uninstalled with the plane. Glad I followed his advise. The plane would not come down as needed, when needed. Maximum decent rate I could get in a stabilized approach was around 400 ft./min. Needed to get closer to 600 or more. Fortunately it only took fifty some screws to remove the Knots 2U seals. Left the small mounting brackets in case some other flyer wants to go a little faster.

Without the flap gap seals I could get almost any decent rate I wanted/needed.

Chris C

Excellent thread guys. I never claimed to know everything, but it's been a while since I was so astonished at *how* wrong I was about something aviation related. I had no idea that gap seals where a benefit in cruise and a detriment in landing config. Would have bet money it was the opposite.

Have any of you guys taken into consideration that the wing loading between the 170/172 vs a 180/182 Is about 2 1/2 to 3 pounds per square foot More on the 180/182? From my experience and I've flown both the 170 of which I have 550 hours in both are floaters Compared to the 180/182's. They all four have the same wing area 174 ft.²

I'd really like to see someone put a go pro on the tail and a bunch of yarn on the flaps and go fly with one on and one off. I'll bet you money the one with the gap seal drops first every time with thw flaps on.

wannabe wrote:This is the third or fourth time MTV and I have agreed on this subject of flap gap seals on Cessnas.

I have a 170-B with a Horton Kit on the leading edge and the aileron seals. The guy I bought it from in McCall Id. said that he was told do NOT put on the flap gap seals if you are going to be flying in the back country where you may need a steep approach.

Well, I had to learn the hard way. At least my AP-IA told me to buy the Knots 2U kit and throw away the Horton set that came uninstalled with the plane. Glad I followed his advise. The plane would not come down as needed, when needed. Maximum decent rate I could get in a stabilized approach was around 400 ft./min. Needed to get closer to 600 or more. Fortunately it only took fifty some screws to remove the Knots 2U seals. Left the small mounting brackets in case some other flyer wants to go a little faster.

Without the flap gap seals I could get almost any decent rate I wanted/needed.

Chris C

Interesting comments. I bought my 182 with the flap and aileron seals already installed and learned to fly in this 182. So I have no experience without the gap seals. With that said, I was always able to pretty much make my 182 drop into just about anywhere with some hard work. But, maybe it would be a lot easier and get into even tighter spots with out the gap seals?? I dunno. That's why it would be very interesting to see the results of before with the gap seals. And then after without the gap seals.

I personally wouldn't mind giving up some cruise speed, but not sure if I'd like to give up any FPM Climb. I guess there's pro's and con's to most everything.

Delete

Late to the "Thread" but he's my $0.02.

I put the Knots-2 U removable gap seals on my A185F.

They definitely help in climb out and cruise.
They make planning a decent more important, and during landing, they effect the way the wing pays off (adversely).

A side note; With the gap seals installed, it takes considerably more force to extend the flaps, which can't be good for cables, rods, bell-cranks, rollers, tracks etc.

I fly around with them off, and "might" put them on if I have a long Cross Country flight. I won't forget my small re-chargeable screwdriver either, especially if I'm going to the back country

If I had to do it again, I wouldn't install them.

I know I’m WAY late to this thread but I thought I'd post my thoughts in case anyone would like to respond, I’m a fairly low time pilot...less than 1000 hrs...and have limited BC experience but lived on a 2000’ grass runway back in the 80’s. Never had a problem with that in a friend’s stock C180. Never had any trouble getting down or making really nice 3-point landings. I could peg the A/S on final at 60 mph and the airplane was rock solid. Touchdown was at around 55 mph. I had a long stint of no flying and then purchased my 1958 182 in June 2018. I had never flown an airplane with “STOL anything”. This plane has a Horton STOL, flap gap seals and VG’s. It was owned by a rocket scientist who worked at JPL in Pasadena. I figured he had thoroughly researched the STOL mods before installing. That was back in the early 80’s however and we’ve probably learned some things since then. I flew the plane from SoCal back up to Boise and didn’t notice any negative characteristics except that it felt heavy on the ailerons. I have about 40 hours on the plane now and have some new opinions about the way it flies. I don’t think it comes down as quick as the 180 did, even with full flaps. My landings are some of the worst I’ve made in 45 years of flying...not terrible, just not great. I fly the final at 65-70 and try to touchdown around 60 with a little power. But at 60 when the plane gets in ground effect it just wants to float, unless fully loaded. Won’t come out of ground effect until around 50. The airplane is not nearly as stable on final at 60 mph as the 180 was. I could blame my poor landings on there not being enough of them but landings were always something that we’re easy for me.

After all my reading on the subject of flap gap seals, I’d like to place some blame there. It sounds like my slow speed/landing performance would improve if I removed them. Living in Idaho, I’d gladly exchange some cruise performance for better short field/rapid descent performance. My first trip into Johnson Creek last year looked like it was going to be no problem until on base to final I just couldn’t get airplane to come down fast enough, necessitating a go-around. The second attempt was successful but a little faster airspeed than I would have preferred. Removing the flap seals won’t be easy as they are riveted on. Still considering but leaning toward removal.

Maybe...but probably not. I think airspeed is the issue.

My airplane has the dreaded flap gap seals, and I can get it down just fine.

I think there is an easy way to remove them by scoring and breaking them. PM Bigrenna, I think he has posted about doing this.

I'm afraid that I seriously doubt that I could tell the difference with or without.

Flap gap seals (at least with fowler flaps) are a speed mod, not a STOL mod.

If you are "floating" with or without them you are too fast. If you have time to look at your ASI to see how fast you are while doing a STOL landing you are too fast. If you are landing "by the numbers" you are probably too fast.

You want to get to the point where you land (and takeoff) by "the seat of your pants" without ever looking at the ASI. That can be learned with tons of practice at any airport. Make every landing a precision landing. Which to start with should be the length of the fuselage. In other words pick a spot on the runway and strive the be on the ground with no flying energy left within the length of the fuselage of that spot (and concentrate on not being short of that spot). It's a perishable skill and if not practiced constantly it won't be available when you want it.

My experience with flap gap seals on my 185 (before and after) is that when they were on the plane- the point of flying and not flying (in other words the sink when the wing no longer has enough lift) was quick. When I removed them the transition was much more gradual allowing for a slower more precise landing.

Thanks deadaluscon. I figured if I was to remove them I would try to cut them off even with the trailing edge of the lower skin rather than drilling out rivets.

Barnstormer...I can identify with your last paragraph describing the transition from flying to not flying being quick. I’ve realized I can’t be in the 50-60 mph range without carrying a modest amount of power. I usually want to get the power off once I’m in ground effect but that’s usually still too high.