aileron seals on SZD-45

Hi Folks,

Looking for some crowd wisdom (or individual wisdom) on the subject of putting seals on a previously unsealed glider. I have an SZD-45 Ogar motorglider, which is a lot of fun to fly except for a couple of things. The main one is that the stick control forces get really high as the speed goes up (as in, two hands on the stick at 70kt). This is not a mechanical malfunction, but needs some explanation. The aileron mechanism is not the usual bellcranks and linkages, but a peculiar combination of a sliding connection between the wing pushrod and a linkage to a 45-degree angled bolt on the aileron. I do not know what this mechanism is called, but apparently is was common on 1970's gliders because it is entirely enclosed in the wing profile. I can see why it fell out of fashion though. The previous owner of my glider, who is an excellent mechanical engineer, spent considerable time and effort trying to make this smoother (such as replacing nylon sliding contacts with teflon, etc) but it's pretty clear that the mechanism is just not designed for low control forces.

I was considering fitting aileron seals, both to reduce drag and also because there is some anecdotal evidence that this reduces stick forces. Is there any reason not to try this? The glider is experimental category - I was thinking that I might ultimately throw out these ****ty linkages and fit a bellcrank system, but that is major surgery, would prefer to try less invasive stuff first.

Thanks,
Jon

On Friday, April 26, 2019 at 7:02:56 AM UTC-6, ProfJ wrote:
Hi Folks,

Looking for some crowd wisdom (or individual wisdom) on the subject of putting seals on a previously unsealed glider. I have an SZD-45 Ogar motorglider, which is a lot of fun to fly except for a couple of things. The main one is that the stick control forces get really high as the speed goes up (as in, two hands on the stick at 70kt). This is not a mechanical malfunction, but needs some explanation. The aileron mechanism is not the usual bellcranks and linkages, but a peculiar combination of a sliding connection between the wing pushrod and a linkage to a 45-degree angled bolt on the aileron. I do not know what this mechanism is called, but apparently is was common on 1970's gliders because it is entirely enclosed in the wing profile. I can see why it fell out of fashion though. The previous owner of my glider, who is an excellent mechanical engineer, spent considerable time and effort trying to make this smoother (such as replacing nylon sliding contacts with teflon, etc) but it's pretty clear that the mechanism is just not designed for low control forces.

I was considering fitting aileron seals, both to reduce drag and also because there is some anecdotal evidence that this reduces stick forces. Is there any reason not to try this? The glider is experimental category - I was thinking that I might ultimately throw out these ****ty linkages and fit a bellcrank system, but that is major surgery, would prefer to try less invasive stuff first.

Thanks,
Jon

Jon,

I do not think that the type of aileron seals used on sailplane will reduce aileron friction where high unsealed forces due to mechanical linkages are already present. It may add to it. It may reduce drag though.

Mike

I’d inspect and lube everything you can get to in the aileron control system. If the wings bow up in flight, duplicate the bow by raising the wing tips. Something else I’d try is to make the stick taller which will give you more mechanical advantage...........I know a major manufacturer that did this to help out with higher stick forces in the air. When flying fast, hold on to the stick up on top, down low when thermalling. Can’t recommend re-doing the control system as this would involve major surgery to the wing and ailerons and would change the balance of the ailerons, also. Doubt that adding Mylar seals would help stick forces.
Hope this helps,
JJ

Do not lube Nylon or Teflon bearings, it will only make it worse. They have the longest liftime and friction when run dry.

FWIW... We found that zig-zag tape in front of control surface seals of our Grob Twin Astir made a significant difference in handling and control forces. Being a standard airworthiness glider, it's nice that the TC owner actually has a service letter for this:

http://www.ltb-lindner.com/service-l...%20seals .pdf

On Monday, 29 April 2019 17:20:34 UTC+2, Papa3 wrote:
FWIW... We found that zig-zag tape in front of control surface seals of our Grob Twin Astir made a significant difference in handling and control forces. Being a standard airworthiness glider, it's nice that the TC owner actually has a service letter for this:

http://www.ltb-lindner.com/service-l...%20seals .pdf

As a person who trained on one of these "concrete swans", I think anything that improved the handling would be appreciated. Will give the zig-zag tape a try.

I trained on a Grob Twin series 1, it had the zig zag turbulators on rudder and elevator.
Works well. It’s available from Striefeneder as ‘combi tape�

Thread drift warning light on.

FWIW one day standing next to my Grob Twin Astir TF in Parowan some guy [ I forget who} Stops by and says: "Hey if you put zig zag tape on the elevator on the fixed piece in front of the hinge line it will help you out"
So I did and he was correct.

Warning light off

On Monday, 29 April 2019 17:59:35 UTC+2, Nick Kennedy wrote:
Thread drift warning light on.

FWIW one day standing next to my Grob Twin Astir TF in Parowan some guy [ I forget who} Stops by and says: "Hey if you put zig zag tape on the elevator on the fixed piece in front of the hinge line it will help you out"
So I did and he was correct.

Warning light off

Thanks Nick, I might give that a try. Are you based in Telluride? Think we met one time...