Windshield Pop Rivets

[bbryan]

What rivet heads are folks using for the windshield to butt rib. Wide flange aluminum of just regulars size head. Also what size for the lexan doors?

[Dick B in KY]

Building a SS7. Did not use rivets, used screws, washers(nylon under head) and self locking nuts.

Dick B

[bbryan]

This is a KF3, and the book has left me hangin. They were missing from my kit, or either I used them somewhere else.

[t j]

My Classic 4 kit manual calls out 1/8 X 1/4 aluminum rivits to attach the skylight to the butt ribs and rear angle.

I used machine screws and nylock nuts instead. They are a pain in the butt to install. I have replaced the windshield once and wished the whole time removing and replacing it that I had used the rivits instead. I can drill out a rivit 100 times faster than remove screws and nuts.

[HighWing]

Just something to think about. These windshields are Polycarbonate which scratches easier than acylic so replacement is definitely in your future. You might consider nutplates and screws for attachment. It will take an hour or so, but you will be glad you did when it is time for replacement. You can find flush head pull rivets on line and it is fairly easy to install the nutplates.
Lowell

[jtpitkin06]

Early airplanes used pop rivets. later aircraft used screws. Pop rivets may cause cracks with too much tension. Screws can be adjusted for tension.

Some builders have put a trim strip along along the screw line to disperse the load on the glass. At the very least, use nylon washers.

JP

[dholly]

bbryan-

I replaced the windshield and skylight on my KF3 with rivets. Drilling out the old rivets went pretty smooth... for the most part. Unfortunately, the rivets holding the skylight to the butt rib capstrips had a tendency to spin and some were generally stubborn as heck to get out. Also, the original builder covered the butt ribs which looks great but offers little to no access to grab a spinning rivet shank while drilling. Suffice to say, several of the original 1/8" holes in the capstrips enlarged to probably 5/32" or more in the process. Just something else to keep in mind when weighing the rivet vs. screw decision.

For the reinstall, I used 1/8" x 3/8" large flange aluminum rivets I had in inventory. Rather than upsize all the holes and use larger rivets into the capstrips or risk pulling new rivets through the capstrips, I decided to make some .035 alum backer strips for support. I really didn't want to cut the fabric over the butt ribs for access, so I had to work through the fuel gauge inspection cover in the right side, and a small opening in the outer left side near the rear spar. I tried match drilling the strips with the old skylight pattern and slipping them into the butt ribs first. Had to work with two pieces per side and, with a lot of fiddling and trimming, finally got them cleco'd in place. Well, kind of, I was still unable to get all clecos in so I marked the strips in place and used the 'prototype' strips to mark and make a final set of backer strips with better hole placement.

It was a race trying to get the strips in place before the epoxy went off and became too hard in the 90*F heat. It was also a messy job trying to snake the strips into the covered butt ribs but the job is done and it's done right without the need for any fabric patches. I would only add that I drilled the polycarbonate (slowly with very light pressure) with a standard 1/8" metal drill bit with no problem. Following instructions from my Avid construction manual, I went back and enlarged all holes to 3/16" (+1/16" oversize) to allow for poly expansion/contraction with (hopefully) minimal cracking/crazing. No problems after install so I'll probably do the same with my Avid+ since I'm not covering those butt ribs with fabric.

[HighWing]

Might have to disagree here as far as it applies to Polycarbonate (Lexan). This material is much different from Acrylic. It is more rubbery than acrylic and will not crack when drilling or if under pressure from the rivets. In fact it drills more like steel, leaving burs on the drilled hole. Rivets have been used on the early Kitfoxes for almost 20 years and the rivet squeezer puts plenty of pressure on the Poly. I am absulutely positive if it had proven to be a problem in that time there would have been lots of talk about it on the forums and the way of the rivet would have been long gone. Plexiglass (Acrylic)? Entirely different animal. Lots of talk of cracking when drilling and installing. You will never hear of cracking when installing the Poly. It will eventually craze at the wing root bend and may even crack from there, but very rarely if ever from a screw or rivet hole.
Lowell

[bbryan]

Great information. In my case I think I will go with the rivets. All good points brought up about stress. I will be adding a strip across the top. Also loved the pics. I will try to post some pics of this mystery plane soon.

[jtpitkin06]

Rubbery? The windshield on my SS isn't. In fact, it is very much like acrylic because it IS ACRYLIC!!!

I must have been reading a different forum a while back when there were many postings on Kitfox windshields broken during installation. The builders merely picked the windshield up and it split.
The instruction sheet included with my LP Plastics windshield has specific cautions regarding lifting it out of the box and cautions about drilling.

But don't take my word for it. Refer to the Kitfox SS assembly manual.

"CAUTION The windshield is made from acrylic and requires special care when installing."

"install the windshield using the sealing tape, screws, nuts, flat washers and finishing washers supplied in the Windshield Installtion Kit... ...Carefully tighten the mounting hardware until you feel slight resistance only."


There indeed was a problem over twenty years when using pop rivets and the factory addresses it in the current construction manual. As you say... the pop rivet is long gone.

John Pitkin
Greenville, TX