What could cause extremely high effort to release a Tost CG hook on aTwin Astir?

On Sunday, May 31, 2015 at 8:12:52 PM UTC-6, Bill T wrote:
Hate to launch again as an "experiment " without knowing what is really going on.
You said the instructor "rear" seat release pull took what you estimate is a 200 lb pull.
Is the front seat release having a problem?
Any problems with an auto back release at top of climb?

BillT

Yes, rear seat release.
The front seat release hasn't been tested in flight.
The "back-release" function seems to work well at the top of the launch.

On Sunday, May 31, 2015 at 7:12:52 PM UTC-7, Bill T wrote:
Hate to launch again as an "experiment " without knowing what is really going on.

I'd suggest anchoring the glider, and using a come-along to tension a rope on the hook to some modest value, say ~150 lbs, and actuate the release. That will at least give you an idea of the relationship between tow rope force and actuation force. It will also show you if anything is distorting under tow force.

On Monday, June 1, 2015 at 8:25:42 AM UTC-6, Bob Kuykendall wrote:
On Sunday, May 31, 2015 at 7:12:52 PM UTC-7, Bill T wrote:
Hate to launch again as an "experiment " without knowing what is really going on.

I'd suggest anchoring the glider, and using a come-along to tension a rope on the hook to some modest value, say ~150 lbs, and actuate the release. That will at least give you an idea of the relationship between tow rope force and actuation force. It will also show you if anything is distorting under tow force.

We're thinking along those lines too. However, to check a CG hook at the rope angles normally experienced, the pull angle has to be something line 45 degrees down from horizontal. That's going to be complicated.

On Monday, June 1, 2015 at 3:33:14 PM UTC+1, Bill D wrote:
On Monday, June 1, 2015 at 8:25:42 AM UTC-6, Bob Kuykendall wrote:
On Sunday, May 31, 2015 at 7:12:52 PM UTC-7, Bill T wrote:
Hate to launch again as an "experiment " without knowing what is really going on.

I'd suggest anchoring the glider, and using a come-along to tension a rope on the hook to some modest value, say ~150 lbs, and actuate the release.. That will at least give you an idea of the relationship between tow rope force and actuation force. It will also show you if anything is distorting under tow force.

We're thinking along those lines too. However, to check a CG hook at the rope angles normally experienced, the pull angle has to be something line 45 degrees down from horizontal. That's going to be complicated.

Lay the fuselage on its side??

Perhaps a pulley mounted to a 2 x 12 of sufficient length that the
glider sits on the board to hold it down. Position the glider on the
board to get the desired angle and put a couple of people in the
cockpit. Use a spring scale and come along to set the desired tension.

snip

We're thinking along those lines too. However, to check a CG hook at the rope angles normally experienced, the pull angle has to be something line 45 degrees down from horizontal. That's going to be complicated.

--
Dan Marotta

On Monday, June 1, 2015 at 11:26:28 AM UTC-4, Dan Marotta wrote:
Perhaps a pulley mounted to a 2 x 12 of sufficient length that the
glider sits on the board to hold it down.** Position the glider on
the board to get the desired angle and put a couple of people in the
cockpit.* Use a spring scale and come along to set the desired
tension.



snip


We're thinking along those lines too. However, to check a CG hook at the rope angles normally experienced, the pull angle has to be something line 45 degrees down from horizontal. That's going to be complicated.





--

Dan Marotta

Yup. Was involved in a similar exercise many years ago when John Campbell was investigating critical angles on Schweitzer releases. If the glider is assembled, you can get a group of folks together and lift it onto some tall saw horses supporting the wings near the root. Use big pads to avoid crushing the skin. Even better would be to take the wings off and support using the lift pin hardpoints. If you do this over a solid tie down (airport tiedown ring), you'll only need a small pulley and you can move the fuselage forward or backwards to get the required angles.