Elevator Gap Seals

[Dick Williams]

elevator gap seals

I am a believer. I have flown cubs with the zero thrust mod and believe the gap seals do 90% of what the thrust mod does for low speed authority. I did stall tests, and don't have the table with me here but recall at light weight, full flaps, full power, my stall speed went down 7 mph. The other regimes were not as low, but all stall speeds went down at least 2-3 mph and you get the same low speed authority/feel that comes with the thrust mod. I did the two-sided sticky to sticky method 4 years ago, the cub has been in AK with no dirt collection or other concerns Jerry Burr noted.
Dick

 

[Dave Calkins]

I believe the gap seals do more for some Cubs than for others.

A good -18 with proper wing-incidence may not see the gains that a "mediocre" or "bad" Cub frame would see.

Also, it can help a "nose-heavy" bird more than a normal bird.

 

[DW]

Ordered mine from Vera yesterday. I used duck tape for years and am a ferm beleaver in elevator gap seals they make a differance.

 

[Dick Williams]

elevator gap seals

I agree, I think they will help some cubs more than others. We measured our angle of incidence but I don't have the numbers handy. As I recall we figured it was a cub that would benefit somewhat from zero thrust.

 

[CubDriver218]

Any pics?

 

[Bill Rusk]

Link to a post with info and pictures of the CC gap seals.

http://www.supercub.org/phpbb2/viewtopic.php?t=4309&postdays=0&postorder=asc&start=330

Bill

 

[cubflier]

I'm trying to understand the aerodynamics behind how gap seals between the elevator and stab help lower stall speed? How does tape on the elevator gap give improvement in the wings ability to fly.

I'm not challenging what's been said about the improvement on stall speed it's just that I can't see how it would accomplish anything but adding a little muscle to the elevator/stab combo maybe the same way a slightly larger tail surface would.



Jerry

 

[Dick Williams]

elevator gap seals

I'm no aero-dynamicist, but I think the idea of the elevator strakes or vgs with the VG kits might be to keep the tail flying longer. Without them the tail wing might have been trying to stall before the main wing, so one might surmise that the gap seals keep the tail flying even longer or cleaner, just as they would do with the main wing. I believe the VG kit makers may have some explanations with their products, too.
Dick

 

[Bugs66]

Went flying briefly yesterday and the gaffer's tape holding good. I didn't have time to do any testing or determinations. Just wanted to report they stick.

 

[Dave Calkins]

adding a little muscle to the elevator/stab combo maybe the same way a slightly larger tail surface would.



Jerry

ding ding ding! You have it.

Also, it is a DOWN FORCE.

VG's help the air stay attached as it flow around the bottom of the stab and UP elevator...helping maintain downforce.

Strakes are another story. They are an "artificial" pitch limiter that reduces elevator authority. I have an article by the famous aerodynamicist Barnaby Wainfan that describes Strakes (ala BLR VG's) as being a stabilizing force that LIMITS the available pitch forces....in other words......."...the strake limits the available downforce, thereby limiting the nose-up pitch, thereby avoiding a stall...". Local aerodynics experts have confirmed this in the case of the SuperCub. Aritficial pitch limiting, not what I want on any Cub I fly.

 

[DW]

Jerry they just gives you more elevator athority at all speeds.

 

[Fortysix12]

I don't know that gap seals will help me. A 24 inch longer landing gear might. I already fly slower with a higher angle of attack than I can manage on landing,that is to say my tires are off the deck who knows how far at my mca. Do gap seals allow less angle of attack at slower speeds. I realize the longer gear and 31 would do wonders but if you don't have these items what's the point.

 

[Dick Williams]

elevator gap seals

Dave,
Thanks, that is very interesting about the strakes and I had not heard that before. That being said, however, for what it's worth, I don't recall ever needing or wanting more nose up than I have with the strakes.

 

[Dave Calkins]

The strake thing versus VG's under the tail versus a sealed gap is applicable more to power off flight or power off flare in my opinion.

If a guy flies a slatted hotrod Cub, he's not helping himself by having a strake. In fact, smaller stabilizers and bigger elevators would be a smart move on a slatted bird. The squared off tail feathers offer this because the leading edge of the squared off stabs have less area than the stock one.

A good Cub does pretty well stock, but there are little bits of optimization if a guy wants to tinker.

 

[Jerry Burr]

Tail stuff

Hi Dick. I guess it's time for me to get in on this. You are correct. With the BLR V.G.'s back at 10% of the chord you're not going to need V.G.'s under the tail or seals on the elevators and the strakes will serve you well. Jerry B.

 

[arcticflyr]

so what does the logbook entry look like for a certified aircraft? With the duct tape?

 

[SteveE]

so what does the logbook entry look like for a certified aircraft? With the duct tape?

What logbook entry? 8)

 

[Dave Calkins]

so what does the logbook entry look like for a certified aircraft? With the duct tape?

What logbook entry? 8)

What certified aircraft?

 

[behindpropellers]

so what does the logbook entry look like for a certified aircraft? With the duct tape?

Looks like this:

 

[Coyote Ugly]

I'm probably the only one that feels this way, but I didn't like the way the elevator seals made my Cub feel in turbulence or slow flight. It took a lot more work it seemed like, with the stick always kinda fighting back my inputs, or having weird stick pressures. Jerked them off and had my old Cub back again... My $.02.

 

[flylowslow]

Coyote, I just read your report, and were you flying with bushwheels? no floats right?............I'm just real curious as Jim Richmond has some new gap seals that I would like to try on my J-3, with Baumann 1500s.........I understand what your saying about getting back that feel for the airplane, but try and expound on what happened at slow flight..........no feel?

 

[Dave Calkins]

I'm probably the only one that feels this way, but I didn't like the way the elevator seals made my Cub feel in turbulence or slow flight. It took a lot more work it seemed like, with the stick always kinda fighting back my inputs, or having weird stick pressures. Jerked them off and had my old Cub back again... My $.02.

Coyote Ugly, in which flight regimes do you notice this?

I had heard reports of stick feedback with elevator gap seals. I watched for it and always wondered.

I honestly have not had an issue with it. Any of you that know Windy Pass up by Healy, Alaska know what it can be like. One time I came through there at gross on skis showing a 29 MPH ground speed in a 96 MPH Exp. Cub getting beat to hell. I feel like I tested the wood spars in this airplane, and the gap seals were no issue. Maybe it'd be worse in turbulence with an empty airplane, or slow flight with flaps down, and flaps extended to the fuselage.

Anyway, different airplanes, etc........ who knows what you'll get?!

 

[AkPA/18]

[ Exp. Cub getting beat to hell. I feel like I tested the wood spars in this airplane,

Hey Dave--had to chuckle a bit at that. I think those spars came pre-tested for you

Mark

 

[Coyote Ugly]

I'm probably the only one that feels this way, but I didn't like the way the elevator seals made my Cub feel in turbulence or slow flight. It took a lot more work it seemed like, with the stick always kinda fighting back my inputs, or having weird stick pressures. Jerked them off and had my old Cub back again... My $.02.

Coyote Ugly, in which flight regimes do you notice this?

I had heard reports of stick feedback with elevator gap seals. I watched for it and always wondered.

I honestly have not had an issue with it. Any of you that know Windy Pass up by Healy, Alaska know what it can be like. One time I came through there at gross on skis showing a 29 MPH ground speed in a 96 MPH Exp. Cub getting beat to hell. I feel like I tested the wood spars in this airplane, and the gap seals were no issue. Maybe it'd be worse in turbulence with an empty airplane, or slow flight with flaps down, and flaps extended to the fuselage.

Anyway, different airplanes, etc........ who knows what you'll get?!

When I bought my previous Super Cub, it had the gap seals on it, and I was really used to my old J-3. the elevators just had that subtle weird pressure I described, like it was fighting back against me in turbulence and the stick didn't get lighter and start coming back easily just as you get really close to a stall like I was used to. The seals were barely coming loose in one spot, so I just removed them, intending to replace them with some new tape, and wow, that Cub felt like a Cub again... That old J-3 feel was back. Never did reinstall on that Cub or my present one, cause I like it just as it is.. I do saw off 1/4 - 3/8 inch off of the up stop tho, to get a little more up, as both 180 horse Cubs seemed to need it.

I don't know, maybe that first Super Cub was just strange, it had over 10,000 hrs. and I know everyone else seems to like the seals. My son flew that Cub a lot for work before I bought it, and he liked the seals too. Maybe it's me that's weird.

Oh, and... I don't like the thrust line mode either, maybe that says something too... ha ha

 

[Marty57]

This is a very interesting thread. Some of the comments about stick inputs and pressure on J-3s vs other Cubs with the gap seals need some clarification. Are you flying J-3's with or with out balanced elevators? I would think it would be apples vs oranges if you are trying to compare balanced vs unbalanced. Any thoughts on that? Thanks,
Marty57

 

[Crash]

First it's wing candy, now its tail candy. Will you guys ever just learn how to fly?

That being said, I think I'll try a set to see for myself..... :lol:

Crash

 

[arcticflyr]

The comment about cert a/c was that this is not in the experiential form. I thought we were talking about a/c that have tdc's. Just found it odd that a a IA would tell any one to put duct tape on a primary flight control.

 

[SteveE]

articflyer....

Ok,, you are probably right... Yes there are the "By gosh, dont change a thing, you be damned and hung forever FAA rules",,,, and then there is common sence...

Most of the mods have evolved from somebody doing something on an experimental and found it worth the money to get it certified.... Not sure it is worth the money to pay to get a piece of duct tape certified for an stc.... so it falls in the common sence category... just like putting duct tape on your oil cooler in the winter to keep the oil warmer when flying.... no stc for that either....

It falls under the government "Dont ask dont tell policy".. 8)

Have a good Thanksgiving..

 

[mikeo]

Eaton only You an Eddy would know about don't ask don't tell policys mikeo

 

[SteveE]

Eaton only You an Eddy would know about don't ask don't tell policys mikeo

And may your Thanksgiving turkey be burnt and dry.. 8) and your pumpkin pie be runny... 8)