The International Cessna^® 170 Association

In the process of installing flap trailing edge extrusions, I find that my flaps were assembled with 3 spot welds in-between each little v rib (1948 170A). It looks like it would take at minimum a 1/8" hole to drill them out. When I look at other posts I see two 3/32 rivets between the ribs. I haven't tried drilling any out yet, I'm concerned that a 1/8" drill won't remove all the welded area and then I will have to risk stretching the skin forcing it apart or drilling to 5/32 and having a lot of large rivets. I could also try to set up a flat faced bit to machine through one half of the weld, drill separate 3/32 rivet holes and fill the fly-cut spot weld holes with filler epoxy. Any recommendations?

Seems like it would be easier to re-skin them.

In between each ? diamond, ouch! How many holes do you think you'll end up with?
New skins are relatively easy to install, (a few hard rivets to get to at the wedges) if you have a solid straight edge jig to hold the trailing edge true to the front spar.

Hmmm makes me wonder out loud. "Are you using a STC to install the edge bulb and does it cover the '48 which seem to be welded at the training edge"

I had made repairs using rivits in several places on my '48 over the years. Last year I reskinned them. Much better.

Larry

I would drill them to the smaller size like you want then slide a thin steel putty knife between the skins and gently tap the handle with a hammer to seperate the remaining spot weld. I believe they were of pretty poor quality anyway. It should come apart pretty easily.

Fred you may have more skill in this process but when I've tried to split stuff apart the welds were not evenly spaced nor were the diameter of the welds.
So I was thinking much like you thoughts but then I had a vision of a trailing edge with holes in an erratic pattern plus the possibility of making an occasional tear. Again my vision is coupled to my past experiences with spot welds and flimsy flap trailing skin edges. Maybe I don't have the same amount of patience.

Is this a necessary repair or a desired modification? I've wanted to do this mod ever since the first time I blasted the trailing edge with my forehead

If its a needed repair, it sounds like re-skinning would be easier and look better in the end.

Well, Mc Farlane says that my flaps require re-skinning to install the trailing edge stiffener. I mentioned to them that a note to that effect would have saved me a lot of head scratching. BTW on Mc Farlane's and Spruce's websites the part is listed as approved for the 170 & 170A but a close reading of the PMA approval of this part only lists it for the 170B.
Thanks for the comments, I hope this helps someone else.

Douglas wrote:Well, Mc Farlane says that my flaps require re-skinning to install the trailing edge stiffener. I mentioned to them that a note to that effect would have saved me a lot of head scratching. BTW on Mc Farlane's and Spruce's websites the part is listed as approved for the 170 & 170A but a close reading of the PMA approval of this part only lists it for the 170B.
Thanks for the comments, I hope this helps someone else.

As a matter of fact it did help me...Thanks!!