Corroded main pins?

Have a friend looking at a used SZD 48-3 for sale with corroded pins,
he's wondering if replacement is feasible. Would pins from a totalled
ship be a possibility?

On Friday, 5 June 2020 07:58:06 UTC-7, kinsell wrote:
Have a friend looking at a used SZD 48-3 for sale with corroded pins,
he's wondering if replacement is feasible. Would pins from a totalled
ship be a possibility?

Shear pins protruding from the fuselage? These are not replaceable. Spar stub connecting pin is standard on many SZD gliders. You can buy a replacement from AllStar PZL (http://szd.com.pl/en).

Are they so bad that polishing them out with fine wet sandpaper is out of the question?

On 6/5/20 4:25 PM, wrote:
Are they so bad that polishing them out with fine wet sandpaper is out of the question?


Don't know. He did use the term "corroded" so that implies a
significant problem. He is an A&P who works on helicopters, hoping to
find technical documentation on the issue. Says the factory is shut
down with the virus situation and not currently responding to support
requests.

If there is significant "pitting," the corrosion is probably advanced enough that the strength is compromised to some extent. If it takes more than polishing to remove rust, you are probably taking off enough material to affect the fit in the bushings, and that is most definitely a bad idea.

On Friday, June 5, 2020 at 8:58:06 AM UTC-6, kinsell wrote:
Have a friend looking at a used SZD 48-3 for sale with corroded pins,
he's wondering if replacement is feasible. Would pins from a totalled
ship be a possibility?

The right side pin has some pitting but I feel not enough to worry about. The left pin, I was able to peel a significant chunk of rust off of it with my fingernail. All this was due to a couple of tennis balls left on the pins to "protect" them. They held water in contact with the pins. The rest of the ship is in great shape, it would be a shame to throw it away on account of the spar pins. I hope they are replaceable without having to cut into the spars.

On Monday, June 8, 2020 at 7:16:08 PM UTC-5, Bob Herman,

While I have never seen any SZD glider up close,
Several of the gliders I have owned, (Phoebus, STD Cirrus, SHK, Mosquito)
Have what appears to be a sleeve and a roll pin securing such pins. Sleeve being the Glassed In part, roll pin securing the actual pins in the sleeve.
Worth a close look.
Scott

On Tuesday, June 9, 2020 at 7:21:46 AM UTC-6, Scott Williams wrote:
On Monday, June 8, 2020 at 7:16:08 PM UTC-5, Bob Herman,

While I have never seen any SZD glider up close,
Several of the gliders I have owned, (Phoebus, STD Cirrus, SHK, Mosquito)
Have what appears to be a sleeve and a roll pin securing such pins. Sleeve being the Glassed In part, roll pin securing the actual pins in the sleeve.
Worth a close look.
Scott

I've looked at them closely and they don't have a roll pin. They are drilled through the center, about a 5mm hole and threaded. I'm hoping this is for the sake of extracting the pins and replacing them.

If it is the pins at the pointy end of the wing spars, the answer is that
they cannot be replaced without serious work. The pins are welded onto a
steel fixture that is glassed into the spar stub. Roughly said (and by
heart), it is wedged in between the upper and lower longerons, with some
filler blocks. The stub is then wrapped with several layers of glassfibre
cloth. Good news is that replacement is not only feasible by a competent
repair shop, but a repair procedure is available through SZD, as this is a
standard replacement with the similar Jantar Standard 2's at 3,000 hours
life. Like most other companies in Poland SZD's company hours and
capability are much reduced through Covid-19 restrictions at the moment.

On Wednesday, 10 June 2020 17:30:06 UTC+10, Eric Munk wrote:
If it is the pins at the pointy end of the wing spars, the answer is that
they cannot be replaced without serious work. The pins are welded onto a
steel fixture that is glassed into the spar stub. Roughly said (and by
heart), it is wedged in between the upper and lower longerons, with some
filler blocks. The stub is then wrapped with several layers of glassfibre
cloth. Good news is that replacement is not only feasible by a competent
repair shop, but a repair procedure is available through SZD, as this is a
standard replacement with the similar Jantar Standard 2's at 3,000 hours
life. Like most other companies in Poland SZD's company hours and
capability are much reduced through Covid-19 restrictions at the moment.

+1 to Eric's response here. The Jantar Std 2 pins are replaced with Std 3 pins, which are good for a 6000hrs (replacement is not done on Std3s). I would not be using pins from a totalled ship unless you put them through some serious NDT procedures to ensure they're safe. They cop a lot of force through them in any situation where the wing tip stops and the rest of the aircraft keeps moving.