Canopy screws

avi8tor50 · #1 07-03-2007, 07:23 PM

Working on the slider portion of my 9A canopy. Have everything drilled, dimpled, and countersunk. Went to do a test fit of the side skirts. When I placed the screws from side skirt to canopy I found that there was some bowing out of the sideskirt between the screws. This resulted in a gap between the plexi and the sideskirt. I rechecked to be sure that my hole spacing was correct and it was. I know I could slip some RTV to fill the gap but it really looks kind of bad. Sort of gives the top edge of the sideskirt a "wavey" appearance instead of straight and flush against the plexi. Wondering if anyone else had this problem and if so how they resolved it.

Thanks
Peter K

painless · #2 07-03-2007, 08:31 PM

How are you installing the screws? Perhaps you could start in the middle of the side skirt and work your way from there to the front and the back of the skirt. By doing that you would be essentially smoothing out the skirt from the center out.

I would also make sure that your countersinks in the plexi are deep enough.

Did the skirts lie flat when everything was clecoed?

Regards,

avi8tor50 · #3 07-04-2007, 06:56 AM

Yes to your questions Jeff. It seems that the screws, when tightened, just pull the metal of the skirt in enough to make it bow between the screws.

mburch · #4 07-04-2007, 07:24 AM

Peter - Thanks for posting this. I was about to dimple the side skirts, but based on your experience I think I'll use my edge roller on them first to try and prevent waviness. Maybe you could find a way to work around the dimples and do the same...?

cheers,
mcb

painless · #5 07-04-2007, 08:03 AM

Peter:

Ok, now I understand what is going on. One suggestion/possibility to try is when you go to finally assemble things, place a dab of proseal at each scew location in the plexi cs. Then install the screws just to the point where they start deforming the skirt and then back out a smidge.

This will support the skirt dimples. It sounds like you might have over-countersunk your holes in the canopy. The first logical concern with this fix is that you are not tightening those screws enough. Thing is, you are using locknuts here, and this is not a structural part. The proseal will frim up enough that if you want to you can go back and slightly torque the screws a tad after all has set up.

Perhaps you could try to duplicate the problem you have with your skirts on some scrap plexi and aluminum and try the above method out.

Hope this helps.

Regards,

mburch · #6 07-04-2007, 10:32 AM

Here's another idea - if the problem really is that you countersunk too deep, you could put #6 tinnerman washers between the screw heads and the side skirt. That would prevent the screw from sucking the aluminum down into the countersink. As a bonus, now the dimpled alumimum is free to float within the slightly oversized countersink, and all the force from the fastener is purely against the "shoulders" of the hole. Once it's all painted you'll never see them.

I'm thinking of doing this in the area at the front of the slider canopy where the plans call for pop rivets bearing directly on the plexi... seems like if I countersink just a touch deeper than normal and use #4 tinnermans under the rivets, I'd end up with the clamping force spread over a much larger area, and less strain on the plexi.

mcb

Jeff Vaughan · #7 07-05-2007, 09:44 AM

I had the same problem. Seems that the square tubing on the side of the slider canopy was not parallel with the side of the fuse. Both sides were slightly bent inward.

I took out my metal bender tool. Not sure what you call it you know the one that looks like pliers but has about a 4" flat face and bent/angled the top inward. This worked fine