Lift pins

I have not yet found a description of "lift pins" that I understand but they apparently are pretty important.

Can someone please tell me what lift pins are?

If you try and fly without your Lift Pins, you won’t find ANY LIFT!
;) JJ
Actually, the 4 lift pins attach the wings to the fuselage............rather important, I’d say!

Yea they are the pins that the fuselage hangs off of.

On Wednesday, July 24, 2019 at 7:09:32 PM UTC-5, Tony wrote:
Yea they are the pins that the fuselage hangs off of.

I'll bet they look a lot like SSA Diamond pins:-)

OK- nobody really gave a decent description of the lift pins, so I will give it a try.

Your wings are held together inside the fuselage by large composite spars, either with an interlocking fork and tongue and dual main spar pins (like Schleicher) which carry the load of the glider in flight, or a fore/aft spar arrangement with one main pin, generally located at the center of the spar junction, in the middle of the fuselage. The carry-through load is handled by pins extending through the ends of the spar stub that fit into sockets at the root of each wing. This is a characteristic of Schempp-Hirth gliders..

Both design methods have been utilized by other manufacturers. Interestingly, Jonker Sailplanes use the two main pin configuration on the JS-1, while the single pin and lateral spar pin/socket design is used on the new JS-3.

Now, the lift pins. Since the main spar is designed to carry the load of the aircraft laterally, there must be a way to constrain the wing and keep it in horizontal alignment with the fuselage. This is handled by the pins extending from the fuselage ahead of and behind the main spar. (Although Jonker prefers to have the pins extending from the root rib and fitting into sockets in the fuselage.)

Essentially, the lift pins keep the wing in proper alignment relative to the fuselage while in flight, while the spars and their retaining pin(s) hold the wing together and carry the load of the aircraft.

On Thursday, 25 July 2019 04:36:26 UTC+2, wrote:
Essentially, the lift pins keep the wing in proper alignment relative to the fuselage while in flight, while the spars and their retaining pin(s) hold the wing together and carry the load of the aircraft.


I'm not an expert but I thought the lift pins (for and aft pins at wing/fuse junction) carry the full load of the fuselage on gliders. They're not there just for keeping things aligned.

That is certainly the case on my Nimbus 2 where the main spar is joined and secured with a main pin but can still essentially float around in the fuselage if it were not for the lift pins on the wings.
Hence the name "lift pins" - they carry the fuselage load.

I think the goal of the wings only touching at the lift pins simplifies the design's engineering. As things expand, contract, and flex there are fewer places where the forces are transferred.

I've always first explained glider assembly to new folks as the assembled wings are a structure all themselves that happen to get assembled passing thru the fuselage. Then mention the 4 pins hanging either the fuselage or wings depending
if flying or on the ground.

What is interesting/fascinating to me is that the fuselage is hanging from the root ribs (via the lift pins) only. That means the entire load of the fuselage, pilot (times 7.5G design loads) are being restrained by the root ribs (one rib per side). I'm just amazed what little material is there to transfer the loads to the rest of the wing structure. I would expect those poor ribs to be ripped out of the wing at high G loads. But alas they don't.. Pretty amazing design actually.

Dirk,
Those are not,�poor little root ribs�, in fact the designers have reinforced them with several layers of cloth running from the spars deep into the root ribs on both sides of the spar, so that they will transfer the fuselage load into the wings.
JJ

On Friday, July 26, 2019 at 5:50:02 PM UTC-4, wrote:
Dirk,
Those are not,�poor little root ribs�, in fact the designers have reinforced them with several layers of cloth running from the spars deep into the root ribs on both sides of the spar, so that they will transfer the fuselage load into the wings.
JJ

Wing skins also play a meaningful part in handling the loads.
UH