Original 4 panel flat windshield and wind screens

[Hank Jarrett]

When I rebuilt the 41 I had seen many photos of the factory production line and all of the planes had transparencies from flat pieces held together with metal strips like the Taylorcraft on display at Sun-N-Fun. A little more research showed that we did not have the technology to make "blown" transparencies before the war and much of the development was done after the prototype Spitfire was shown to need "just a bit" more head room and visibility. If you have ever sat in a Spitfire with a Malcom Hood it STILL needs some head room!
I decided to try to reproduce the 4 piece original windscreen for my 41. I did use 10-32 screws and nuts instead of rivets in order to get it right prior to finding a REALLY long throat rivet squeezer (no way I was going to try to buck all those rivets without cracking the Plexi). Since finishing it my IA has looked at it and said that the substitution of all those screws makes more sense than using rivets. I will probably go to rivets eventually, but there are a LOT of other projects in line first. If I remember right the one at Sun-N-Fun also used small screws. If you decide to try this (it turned out to be MUCH more work than I ever imagined!) you need to drill ALL of the fastener holes oversize so small pieces of rubber tube can be put in the holes. If the fasteners bear on the plastic it WILL crack! One screw or rivet rubbing the plastic hole edge will ruin the whole piece. I had a whole pile of broken transparency in the hangar corner by the time I got finished.

Yes, the vents are supposed to be on the windscreen, NOT the door windows. Also a great way to break the side "glass".

[Hank Jarrett]

Re: Original 4 panel flat windshield and wind screens

First step was to go to Kissimmee (OK I have no idea how to spell that which is why I say Sun-N-Fun....THAT I can spell, most of the time). Next i made the parts form card boar and wood to get a template for the "glass". The original transparency material was called Pyrene and is no longer made (since WW-II). It was not fuel resistant, turned yellow in sun light, scratched very easily and got very brittle with age. Some times you sacrifice some originality to keep from becoming "open cockpit" with a face full of plastic shards, plus I could find NO ONE who knew where you could even find it (research looking was how I found out what a terrible material it was). I looked at several plastics and settled on either Lexan (strong, low scratch resistance and poor fuel resistance) pr Plexi (still not great, but an aviation standard). Since the thickness of the original windshield was not even made any more I went up to the next thicker Plexi and had the piece cut and drilled at a professional plastics shop (over $100 for the plastic) Plexi is stronger than Pyrene and if I was going to add weight to the plane this looked like a good place.

[Hank Jarrett]

Re: Original 4 panel flat windshield and wind screens

Remember I said that if the fasteners touched the plastic holes it would crack the plastic? In order to bend the .125 windscreens (a windshield is the front piece, the side pieces are called windscreens) you have to get the plastic fairly warm. I snapped several pieces before I found out just HOW warm. The day I finally got the plexy to lay right I heat soaked the plastic till it was VERY hot to the touch, then gently pulled it around from the windshield to the A pillar with a false pillar and bungees. My hangar was 110* F that day and I let it sit all afternoon to get it to relax into position. I finally put the actual trim pieces on and secured it to the A Pillar, leaving it for the rest of the day and that night to relax. Next morning I came back to a snapped windscreen (that is my hand and a piece of upholstery fabric through the break). When I took it apart to make another new one I found that one of the little rubber tubes had fallen out and the strew had stressed the plastic and broken it. I made another one (I was pretty fast at making them by this time) and used a tile gun to heat the plastic while the bungees loaded the plastic and bent it. Once secure I once again fanned the plastic with the heat gun until it relaxed in position and no longer sprang back at all. I did get a few tiny bubbles in the plastic right up near the leading edge of the wing but the wing to fuselage fairing covers them. It was a couple of years after building the transparencies before first flight and there have only been a couple of tiny cracks in all those holes to stop drill (amazingly all in the professionally drilled windshield and none progressed). After the pilots side the passenger side was a breeze.

Hank

[3Dreaming]

Re: Original 4 panel flat windshield and wind screens

I did a 4 peice windshield in my 41 BL when I restored it. I used DOT Lexan instead of Plexiglass. It was assembled with round head soft aluminum rivets.

[Hank Jarrett]

Re: Original 4 panel flat windshield and wind screens

Tom,
When you get a chance I would like to hear more details. Issues getting it together, cracking problems and fuel resistance especially. The reason for posting is to help others who will follow us. I am especially interested in how you bucked the rivets! Your plane was a major inspiration in doing mine.

Hank

[3Dreaming]

Re: Original 4 panel flat windshield and wind screens

Hank,
We had obtained tracings of a barn find with a 4 piece windshield. I made patterns to fit the airplane out of the black panel board like used in upholstery. The assembly was pretty straight forward. We had to modify a rivet set for the round head rivets. The soft rivets buck pretty easy. After it was together you could see some little stress cracks around the rivets, nut they didn't have a tendency to migrate. I think the current owner replaced at least one if not all of the panels this past year, at least we sent him some rivets so he could replace the panels. That means they lasted about 25 years without any real issues.

[Hank Jarrett]

Re: Original 4 panel flat windshield and wind screens

My main concern was with getting gasoline on the Lexan. The plastics place said it could craze and fog the Lexan. I had a bad experience with a line boy overfilling my tank and flooding the boot cowl and cockpit with fuel once. I doubt Tom would ever spill gas on his windshield but has anyone else ever had problems with fuel damaging their transparencies, and if so what material? I may need to put some gas on some scraps and see what happens.

As an aside, did you secure the lower edge of your windshield or just let it float on the boot cowl? I used long machine screws at the bottom of the metal strips between the windshield and windscreen to run down through the boot to hold the lower edge down tight. I thought maybe the tabs on the tubes were for that but couldn't see how to use them. Anyone know what these tabs were for?

Hank

I DO NOT allow ANYONE to refuel my plane but ME now.

[3Dreaming]

Re: Original 4 panel flat windshield and wind screens

Hank,

I am sure that it had fuel splashed on it more than once, but I don't recall any issues.

To the best of my recollection the bottom edge just sat in the groove in the boot cowl. I did have a piece of rubber "U" channel around the bottom edge.

[Mark Julicher]

Re: Original 4 panel flat windshield and wind screens

Hank,
Here is experience from tcj of the Kitfox forum:

My Kitfox has the nose tank with the filler neck right in front of the windshield. I use a Mr. Funnel and there are always tiny droplets splashing out. I just wiped them off and had no problems for about 8 years. Last year those tiny droplets started leaving spots that would not clean off with any method I tried. then a larger drop hit right near the bottom of the windshield and it instantly cracked about 2 or 3 inches long.

[PA1195]

Re: Original 4 panel flat windshield and wind screens

My experience with uncoated Lexan is it will crack as noted along the edge of any cut from fuel. Auto fuel primarily or an auto-100LL blend. I've sometimes used 20-80 mix to simulate 80/87. Seems like there's a sudden shrinkage of the material that creates a stress fracture. I've replaced the material with plexiglass on other planes and keep fuel away from my seaplane doors on the Taylorcraft.

Gary

[Clark]

Re: Original 4 panel flat windshield and wind screens

I have a question/s born out of what I've found in cleaning and dismantling my project 1940 BL 65. I removed the blown wind shield, it was held in place first of all by the head of screws over edge of windshield. The edge was then filled in with what looked like ordinary white window glaze (hardware store variety). Along the bottom edge this was covered by a strip of fabric attached by dope to the cowl and the windshield. The edges of the windshield was attached with aluminum strip folded over and held in place with two screws and no sealant at all on each side, not going through windshield which I believe would be correct, although more screws would lead to more confidence. The top had a line of screws through a strip of aluminum into the wood on the back side of the cross tube with sealant along back edge. After removing the windshield I went about removing the top dash panel. This appears to be formica.

In reverse order, I cant imagine that formica was approved, my 1946 had an aluminum panel and I assumed this would too. Next the manual is woefully short on instructions on installation of windshield whether flat or blown. As I recall there was a aluminum strip along bottom edge on the inside and a strip along bottom edge on the outside bottom edge securing windshield. And if I remember there was felt on the inside between metal and windshield. Has anyone any knowledge of technical material on fabricating such and what is field approved and what requires a higher level of oversight.

The blown windshield I believe is perfectly serviceable and will be considered airworthy, however it's installation, seems a bit ...? If all else fails a flat windshield seems a perfectly more suitable solution. GAthering information at this stage.

[3Dreaming]

Re: Original 4 panel flat windshield and wind screens

the 4 piece windshield sat in a groove in the boot cowl around the bottom, with a "U" shaped rubber seal. The only place it was anchored to the boot cowl was where the metal strips joining the 4 panels were. It was secured on the sides with a folded metal piece and clamps around the door post. There was a metal strip that attached to the wooden piece across the top of the fuselage, with the screws also going through holes in the upper windshield panel.

[Hank Jarrett]

Re: Original 4 panel flat windshield and wind screens

I took a LONG look at the pre-war T at the museum at Sun-N-Fun and copied how it was done. I have a bunch of photos of how I did it but it wasn't nearly as easy as it looked at first. To start understand that the big flat piece up front is the "Windshield". The two side pieces between the windshield and the A Pillars (the tubes the door hinges are welded to) are called Windscreens. I have never seen the original name used for the top piece between the Windshield and the fuselage top.

If you decide to build an original transparency system note that the vents were originally in the WINDSCREENS, not the door windows. Be prepared, you will break a LOT of windscreens getting them bent in place. You have to use heat (I used a tile gun with a fan tip) and the heat is "just below" what is needed to bubble the plastic. I bubbled a lot of plastic and broke a lot more curving it. At least it wasn't expensive.

If you decide to use the original 4 piece I can't see where any paperwork should be required. It was what the factory used originally.

Hank

In my opinion, the 4 piece REALLY adds to the character of the pre war planes. I would never go back.

[Clark]

Re: Original 4 panel flat windshield and wind screens

The boot cowl I have has a rounded dimple that matches the round shape of the windshield. My next question is whether the boot cowl has been modified to fit the "Blown windshield," or has the "Blown windshield," been cut to match the the groove/dimple. I'll attach pictures tomorrow. I am intrigued by the flat windshield and being original and if I'm going to be in a six of one half dozen of the other situation I am going to seriously consider returning to it.

[Clark]

Re: Original 4 panel flat windshield and wind screens

The boot cowl I have has a rounded dimple that matches the round shape of the windshield. My next question is whether the boot cowl has been modified to fit the "Blown windshield," or has the "Blown windshield," been cut to match the the groove/dimple. I'll attach pictures tomorrow.