Author Topic: Curved Windscreen (Read 7782 times)

Aerodude45 · « **on:** December 27, 2014, 01:59:31 PM »

I experimented with a sheet of 32" by 20" by .100" acrylic in my shop this past week and I think I've figured out how to make a decent windscreen that covers all of the front structure and is curved to provide less drag. I simply marked the center of the 32" dimension to get the middle of the curve, PUT ON MY WELDING GLOVES, and used my kerosene heater to heat the acrylic as I bent it by hand. To get the right bend radius I would occasionally fit the acrylic to the front of the plane until it fit right. I then used duct tape to secure it in position, marked the position of the tubes intersecting the corners with a straight edge, and cut them off with a plastic scorer. What I ended up with is a little small and might slightly reduce visibility. I may end up doing the same procedure later with a 30" by 32" piece of acrylic to cover the entire front. For now, however, I plan to cover the gaps at the top, bottom, and sides of the windscreen with .8mm plywood.

Below is a picture of the windscreen, and a picture of the heater I used.

I kept the protective plastic sheet on the acrylic while I bent it. I discovered through experimentation that you can start melting the plastic sheet and still peel it off later to reveal undamaged acrylic underneath.

Although it is possible to heat acrylic and bend it with a heatgun, it takes a lot of patience and I found it entirely too easy to damage the acrylic. If you do end up starting to melt the acrylic and getting bubbles, it's possible to sand them out with progressively finer grits of sandpaper and then polish it back to an optical finish with Novus plastic polish, but depending on the size of the damage it could take several hours and it might be more worthwhile just to get more acrylic and start over...

What I ended up with looks like it will work, but I don't know how it will hold up yet. I plan to use vinyl tubing around the front two tubes to protect the windscreen from engine vibrations. If I end up making the larger version of this, I might just build it large enough to not contact the front tubes at all.

Sam Buchanan · « **Reply #1 on:** December 27, 2014, 02:54:14 PM »

0.062" Lexan can be bent into shape without heat. This screen was just bent into shape by hand and secured with clamps:

Aerodude45 · « **Reply #2 on:** December 27, 2014, 02:57:43 PM »

Hm. Probably could have ordered some at aircraft spruce. Already had the plexiglass, but if I don't like my windscreen I'll try lexan.

Sam Buchanan · « **Reply #3 on:** December 27, 2014, 02:58:55 PM »

Quote from: Aerodude45 on December 27, 2014, 02:57:43 PM

Hm. Probably could have ordered some at aircraft spruce. Already had the plexiglass, but if I don't like my windscreen I'll try lexan.

Mine came from the aviation aisle at Lowes. Lexan (polycarbonate) won't shatter like acrylic and you can machine or drill it without worrying about it cracking.

Aerodude45 · « **Reply #4 on:** December 27, 2014, 03:04:02 PM »

Same density but thinner. Easier to drill. More resistant to cracks. No heat needed to bend. Geez, now I want to remake mine...

Aerodude45 · « **Reply #5 on:** December 27, 2014, 03:16:21 PM »

Scale says my windscreen is 2.25 lbs. That's with .100" acrylic. .062" Lexan would be the same density but 38% less material, meaning I would save .855 lbs. That's a lot of weight for a little airplane. I wonder why we used .100" acrylic in the first place... *scratches head*

Aerodude45 · « **Reply #6 on:** April 13, 2015, 10:13:24 AM »

Started working on my new new curved windscreen, this time with .060" lexan and 1/2" aluminum L-angles from the hardware store as supports. I drilled a bunch of lightening holes in the L-angles and shaved about an ounce of weight. I plan on using nylon hardware to attach the lexan to the L-angles. I currently have the braces zip-tied to the fuse, and I might just fly with them that way, otherwise I could pop some pop-rivets in. I'm also going to make the windscreen wider by running supports vertically along the rear of the windscreen and using a brace to hold the windscreen out up near the front wing mount. Pretty similar to what Joe did, I think. Just more holes. Didn't he just pop-rivet the lexan right to the L-angles? I don't mind wind in my face, but it was awfully hard for folks to understand me on the radio...

The .060" lexan is MUCH lighter than the .120" acrylic that was on the first flying iteration of the plane... If the windscreen was 6 sq ft. originally (about 32" by 28", which may not be an accurate estimate) then I've probably already saved 2 lbs just on the windscreen. If you're looking for a way to keep weight down, using the thinnest/ smallest amount of lexan material for the windscreen may not be a bad idea.

Does anyone know if .040" lexan would work if I used L-angle to support it? If so, is there anywhere I can buy lexan that thin in a 4' by 4' piece? The thinnest stuff on Aircraft Spruce is .060" and my local Lowes has nothing thinner than .080" (guess they don't stock the aviation section that well.)

Here's some pictures of what I have so far:

Aerodude45 · « **Reply #7 on:** May 07, 2015, 07:19:50 AM »

Got the windscreen installed. I used L-angle to support it along the sides and cut aluminum tubing lengthwise to provide support around its curvature. This will keep the windscreen lifted off of the front cabanes running to the engine mount. Last year I had issues there with vibration causing cracks. Hopefully the clearance will prevent that issue. I also used some L-angle at the top to hold the windscreen out a little farther from the sides. I drilled lightening holes in the supports. Pop-riveted the lexan right to the supports. For the time being have the supports zip-tied to the fuse. Might fly that way. Drilled lightening holes in all of the supports. It was a lot of work, but weight is weight.