Windshield/skylight replacement

[dholly 718]

Ok, bear with me...

The new to me model III windshield was crazed at the forward carry thru tube and really needed to be replaced. Since the plane came with a bunch of stuff including some clear and tinted .060 Lexan, I figured I'd get that out of the way first and the long Memorial Day weekend provided the opportunity. Not having done this before I was a bit nervous about cracking the Lexan but that ended up being the least of my worries.

Both the windshield and skylight were riveted on. Once I figured out the best size bit for the job, drilling out the 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 hell to get out. Did I mention, the builder went the distance and completely covered the butt ribs, which looks great but offers little to no access to grab a rivet shank while drilling. Suffice to say, many of the original 1/8" holes in the capstrips are probably 5/32" or bigger now.

Using the old windshield for a template was a snap, I cut the outline with a fine tooth metal/plastic blade in a Multi-tool (Harbor Freight's Fein knockoff) and drilled the polycarbonate with a standard 1/8" metal drill bit. Following the Manual instructions I went back and enlarged all holes to 3/16", +1/16" to allow for expansion/contraction with (hopefully) minimal cracking/crazing. I brought the new windshield down to final size and smoothed the edge with a small sanding drum in the Dremel then 220 grit on the palm sander. I'll ease and final polish the edge with some 600grit by hand after taking off the protective film.

For the reinstall, 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 1/8" x 3/8" large flange aluminum rivets I had in inventory. 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 make a final set of backer strips with better hole placement.

After finding the white part of my Hysol supply had crusted over, I followed a tip that heating slightly in the microwave softens to mixing consistency and prepared a batch of epoxy. Not sure if the earlier heating or the 90* hot weather caused it to go off quick, but even with the stuff placed in my beer fridge to keep cold it was a race trying to get the strips epoxied in place before it became too hard. 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 patchs. I'm a bit surprised the KF III construction manual recommended riveting directly into the wood capstrip, though it sounds like manuals were revised sometime later to recommend backer strips. In any event, I'm hoping I kept the Hysol far enough from the holes to prevent gluing the clecos in place while it set up, and the glue on my iPhone screen come off. Grrrr...

The foregoing drama aside, the only real issue I have is with the front windshield post rivet position. From what I see, the manual says to butt the windshield edge to the tubing and drill through the corner angle, lexan and mounting tabs. Mine was originally drilled through the mounting angle, lexan and into the tubing. Clearly incorrect and I don't want holes in the tubing that compromise strength if I'm banging around on floats. So the question now is do I remove the corner angles (looks like they just 'snap pinch' over the tubing and are held on with the two rivets securing the door gas struts) and weld the holes shut? Or add some Hysol and a steel rivet to close each hole? What's the fix here? Funny how the simple jobs tend to turn into more than anticipated, I guess Murphy is alive and well.

Getting closer.

[akflyer 1428]

Ok, bear with me...

The new to me model III windshield was crazed at the forward carry thru tube and really needed to be replaced. Since the plane came with a bunch of stuff including some clear and tinted .060 Lexan, I figured I'd get that out of the way first and the long Memorial Day weekend provided the opportunity. Not having done this before I was a bit nervous about cracking the Lexan but that ended up being the least of my worries.

Both the windshield and skylight were riveted on. Once I figured out the best size bit for the job, drilling out the 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 hell to get out. Did I mention, the builder went the distance and completely covered the butt ribs, which looks great but offers little to no access to grab a rivet shank while drilling. Suffice to say, many of the original 1/8" holes in the capstrips are probably 5/32" or bigger now.

Using the old windshield for a template was a snap, I cut the outline with a fine tooth metal/plastic blade in a Multi-tool (Harbor Freight's Fein knockoff) and drilled the polycarbonate with a standard 1/8" metal drill bit. Following the Manual instructions I went back and enlarged all holes to 3/16", +1/16" to allow for expansion/contraction with (hopefully) minimal cracking/crazing. I brought the new windshield down to final size and smoothed the edge with a small sanding drum in the Dremel then 220 grit on the palm sander. I'll ease and final polish the edge with some 600grit by hand after taking off the protective film.

For the reinstall, 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 1/8" x 3/8" large flange aluminum rivets I had in inventory. 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 make a final set of backer strips with better hole placement.

After finding the white part of my Hysol supply had crusted over, I followed a tip that heating slightly in the microwave softens to mixing consistency and prepared a batch of epoxy. Not sure if the earlier heating or the 90* hot weather caused it to go off quick, but even with the stuff placed in my beer fridge to keep cold it was a race trying to get the strips epoxied in place before it became too hard. 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 patchs. I'm a bit surprised the KF III construction manual recommended riveting directly into the wood capstrip, though it sounds like manuals were revised sometime later to recommend backer strips. In any event, I'm hoping I kept the Hysol far enough from the holes to prevent gluing the clecos in place while it set up, and the glue on my iPhone screen come off. Grrrr...

The foregoing drama aside, the only real issue I have is with the front windshield post rivet position. From what I see, the manual says to butt the windshield edge to the tubing and drill through the corner angle, lexan and mounting tabs. Mine was originally drilled through the mounting angle, lexan and into the tubing. Clearly incorrect and I don't want holes in the tubing that compromise strength if I'm banging around on floats. So the question now is do I remove the corner angles (looks like they just 'snap pinch' over the tubing and are held on with the two rivets securing the door gas struts) and weld the holes shut? Or add some Hysol and a steel rivet to close each hole? What's the fix here? Funny how the simple jobs tend to turn into more than anticipated, I guess Murphy is alive and well.

Getting closer.

Couple holes in the tubes are not going to be a deal breaker... I would put a little hysol over the hole to keep water out and call it good. or run the windshield rivets back in place. U spent alot more time dicking with the backers than I would have.. Ida cut the fabric in about 2 seconds flat and had it done in an hour, but that is why you will have a beauty and I have a beat around the bush, alder basher

make the fat bastard your show bird and get the KF in the air

[dholly 718]

Well, after reading a recent post on another site where the skylight pulled away from the butt ribs and blew out the turtle deck, I wanted the backers but I just couldn't bring myself to start cutting fabric yet lol. And sometimes I just get stubborn enough to take the hard road as a matter of principal. Anyways, I didn't realize the windshield post holes were in the wrong place until looking in the manual for rivet sizes and already match drilled the new windshield. so as long as there is no safety issue I guess I'll just re-do the way it was and save having to replace the trim angles.

[dholly 718]

New windscreen and skylight sure look nice, but now the side windows look like crap lol. Time for some new bubble doors maybe.

[Bflight 11]

SInce avid is on a break anyone have a windshield template for Avid MK IV

Edited 21 Aug 2020 by Bflight

[1avidflyer 2006]

If you have the old windshield still, the best thing to do is clamp it to the new sheet of lexan, and drill all the holes and mark out and then cut the new sheet.  You will end up with an exact copy depending on how accurate you can cut the new sheet.  I've done that quite a few times.  JImChuk

[dynomike 91]

I didnt like the rivets in the capstrip only either so I used backup washers on the riviets

[Bflight 11]

All mine seem to be bolted in. I dont know what is better for strength but rivets with wqshers would be faster and cheaper, prices out box of stainless bolts,nut and washers WOW

[1avidflyer 2006]

On Kitfox 4 I used # 6 truss head SS screws, box of 100 is probably 6 bucks on ebay.  Used maybe 30.  Pop riveted to the back cross piece of aluminum.  Actually large head rivets were 10 cents each in local farm and fleet type store.  JImChuk

[TJay 1042]

I also used rivets on the back and screws everywhere else.

https://www.ebay.com/itm/Qty-100-6-32-x-3-4-Button-Head-Socket-Cap-Screw-Stainless-Steel-Screws/152580219328?hash=item23867d61c0:g:bk0AAOSwRl9dg9lT

https://www.ebay.com/itm/Stainless-Steel-Nylon-Insert-Hex-Lock-Nuts-4-40-5-40-6-32-8-32-10-32-1-4-20-5-16/122625440131?hash=item1c8d0bb983:g:bM8AAOSw0wldC-Gk

There you go.

[Bflight 11]

I also used rivets on the back and screws everywhere else.

https://www.ebay.com/itm/Qty-100-6-32-x-3-4-Button-Head-Socket-Cap-Screw-Stainless-Steel-Screws/152580219328?hash=item23867d61c0:g:bk0AAOSwRl9dg9lT

https://www.ebay.com/itm/Stainless-Steel-Nylon-Insert-Hex-Lock-Nuts-4-40-5-40-6-32-8-32-10-32-1-4-20-5-16/122625440131?hash=item1c8d0bb983:g:bM8AAOSw0wldC-Gk

There you go.

I like it will start work soon on it. Just ordered the lexan for the turtle deck wanted bronze uv tint but all they had it in was .118" luckily its all straight no real heat bends. What thickness did you do with on the clear windshield? 

[Dusty 126]

Mine was originally riveted with washers on the capstrips. I epoxied a spruce strip to the back of the capstrip for a good bite for stainless screws. The screen replacement will be easier next time. Don't be tempted to try 1.5 mm lexan as the flexing above 90 kts is a bit disconcerting!

[1avidflyer 2006]

.060" thick lexan is probably all you need for an Avid or early Kitfox.  That's all I used on 4 Avids and 1 Kitfox.   Up around 100 mph, it will start to buckle in a bit.  I did use .90" on the Kitfox 4, but that plane may see 120 at tiimes.   Not sure how well the .118" thick will bend around where the wings connect.  Kind of a tight compound bend.  JImChuk

Edited 21 Aug 2020 by 1avidflyer

[wypaul 460]

The .060 works fine at least up to 120 mph.  Yes it flexes but nothing to be concerned about.