Wed Jun 23 2010

Popup tipup modifications

When I tried to fit the top flange angles to the new ribs yesterday, it was clear that the vertical leg of the angle wasn't high enough to allow riveting these on while allowing adequate edge distance. So, Clare was nice enough to let me come to his shop again and cut some new strips and use his brake to bend these. The vertical leg is about 3/16 longer than the previous version.

These retainer clips arrived from TruTrak in the mail today. These retainers are designed to prevent the center screw from backing out. Although I'd rather have their new design for the shafts (threaded stub, cross drilled for a castle nut and cotter pin) this fix will work. Regardless, I may still check with TruTrak to see if I can get my servos upgraded with the new shaft.

Here is one of the new upper flange angles drilled to the new rib. You can see that the top of the rib is about 3/16 below the bend, which is why I needed to make the vertical leg longer on these flange angles.

While working on fitting the new ribs, I realized the 2 degree bend in the sub panel would interfere with the forward flange of my new rib. I'm going to need to make a change here.

I decided to go ahead and make the 2 degree bend in the sub panel components. I just clamped 'er up and beat on the web with a mallet. Worked OK, but the best results were achieved by clamping the rib over a steel bar and beating on the top of the web at the corner of the bar. That made for a "crisper" bend.

Afterward, I trimmed off the bottom portion of the forward flange of the new ribs and fabricated a little flange to rivet on which would follow the 2 degree bend.

Then, after clecoing the top forward skin back on, I drilled through the skin into the top flanges of the new ribs. Since the inboard ribs are normally just stub ribs, I extended the row of rivets the full length of the skin. Unfortunately, the prepunched hole pattern spacing for the stub ribs didn't match that for the full length ribs. I decided to make the rest of the hole pattern match that of the original full lenght ribs, so you can see the spacing is off at about the halfway point.

Before taking this skin off again, I marked where it overlaps the sides of the fuselage. I'll use these marks to determine the length of the new seal strip I'll be installing under the aft edge of this skin.

After thinking about how to correctly position the canopy frame weldment for drilling, I decided that I would make some templates to correctly position the frame in relation to the forward structure.

These pieces of aluminum are some scrap used for practice riveting way back when I was working on the empennage. They're now going to be used for temporary joint plates to hold the canopy frame weldment in position relative to the forward structure. Note that I've drawn a centerline on each of the two skins and aligned them...

...These two joint plates were slid under the skins and match drilled through the prepunched holes in each skin. Here, I've just placed them back on top of the skins to show where they were when I drilled.

The canopy frame is now held in position with the joint plates.

Hrm....something doesn't look quite right here. This image is taken from the front looking aft. You can see the canopy frame weldment pivot between the two ribs, just below the joint plate. Problem is that it doesn't appear to be on center. This pivot is supposed to be halfway between these ribs. Gonna have to figure out where the problem is.