TD roof lifting off w/gas props

[Via]

My new to me TD galley hatch is held up with 2 poles put in place after lifing the lid. I wanted to install gas props and based on sizing and placement tips given to me by Grant, started to install the props, but it caused the top of the TD where the lid is attached to lift off. Any ideas on what is happening and what I need to look for? I have also decided I would prefer not to use gas props but the manual ones used on the old Hunter TDs.

[Gage]

A couple of things could be causing the problem. We need to see pictures of the teardrop and your hatch also just where you located the shocks on both the tear and the hatch. Also what size shocks? Very seldom is Grant wrong with his advice.

[Via]

Gage,
I'll have to post pix later, but the prop was 90 lb and I measured from the hatch hing along the side rib like 4" and then dropped down 7" for location on side of TD. The prop was 17". It took very little pressure to pop the roof. I only installed the one side and a friend held up the lid, then dropped lid slightly, immediately causing roof to lift. I didn't get to 2nd one because of this. If I use a manual prop I am presuming location to be similar?

[KCStudly]

When you say it lifted do you mean that the screws holding the hinge to the roof pulled out (this is what I am assuming), or that the roof itself bulged up with the hinge, or something else?

More info is needed.

Most people seem to under estimate the forces involved in a mechanism like this. Despite the fact that the hatch may only weigh 65 pounds or less (tho in some cases more), there is a huge leverage factor that multiplies the forces at the strut anchor points and hinge. Also, if there is any binding, such as if the strut bottoms out before the hatch closes, or as it goes "over toggle", either the hatch will not close or the leverage will make something give.

One thing I plan to do with my hinge is to drill a second row of screw holes on each leaf in an offset pattern (zig-zag if you will) so that the hinge has less chance to rock back and forth on a single row of screws.

[Gage]

Well I'll bet the side that pop'd up was the side with the shock when your friend lowered the other side a little. You have to have both shocks installed so as the hatch opens and closes evenly. Your location sounds about right. The same thing almost happened to me after I installed one shock. I just had to see what it was going to look like. I was holding the left side up and I noticed that I could flex the roof skin on the shock side just by relaxing the left side. Once I got both shocks installed, there was no problem. Not sure but I think I droped down to 80# shocks.



P.S. The poll is a safty item because I was working in the galley area.

[danlott]

I created a spreadsheet calculator to help determine the right struts to use and where to mount them. Here is a link to the thread.

http://www.tnttt.com/viewtopic.php?f=21&t=58263

Dan

[Via]

Great suggestions and illustrations. I will try again shortly.