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Thicker Windshield idea!

J

judoka5051

Well Known Member
Hey Guys and Gals,

I recently responded to a post concerning windshield thickness, and was generally against the idea, mainly because of weight. Then I had an epiphany while trying to go to sleep. Why not make a doubler for just the windshield out of clear plexiglass? The process goes something like this:

Fit everything up as usual, but before the final install of the windshield, install a slightly small windshield of clear plexiglass underneath the main windshield. If everything is kept clean during the install and there's a good seal around the edges to keep moisture, dust, etc out, you'd never even notice the second windshield. I'd strongly recommend sicaflex (at least for the windshield) to make sure it stays put if a bird strike ever occurs.

I'm pretty sure that 3/8 (before forming, varies afterward) will stop anything under 5 lbs, but I'm going to be testing my theory using the imperfect canopies I made while leaning the process.

Unfortunately, I'll only be able make these 'bird stoppers' for canopies I can currently make (RV8, RV4, RV3)

If theres interest in this idea I'll make a form to make just the windshield portion of the canopy, so let me know!

Also, I should be advertising here shortly, I sent Doug what he needs (I hope).

Thanks, Lance
 
I've not long finished Sikaflexing my windscreen and frankly it's a dog of a job. Multiply this by a factor of two at least if you want to add an additional layer. That's two dogs, which by anyone's standard it a dog too many.
My suggestion would be to buy a bone dome if you want secondary impact protection.
Respectfully,
Tom.
 
Are you talking about adding a small shaped inner layer that would be bonded to the inside of an existing canopy?
My questions are:
1. How to ensure no bubbles in the bonding process or are you only bonding the outer edges which are mostly out of the field of view underneath canopy bows or glare shield.
2. I am curious regarding the effects to 2 layers of an imperfect surface on optical quality. Would you notice in increase in distortion?
3. How "perfect" does the shape of the inner piece have to be reference the outer bubble in order to not cause any issues.
4. Will they be retrofittable to an existing canopy or only available when a new bubble is ordered from you?
Interesting concept. I like it.
 
Hey Tom and Sam,

In response to Tom's comment, I realize that not everyone will feel the need to do this, but some folks are 'belt and suspenders'. Remember, I originally politicked against this! Then again, I don't live where there's lots of birds on the field. I might feel differently if that were the case. As far as the gluing,,, I did mine with sicaflex, and it was a little messy, but not a show stopper. It wouldn't add much work to do what I'm talking about. Once the pieces are cut to size, then you install the smaller piece, run a bead of sicaflex, then install the main windshield as usual.

In response to Sam's questions:

1. Only the outer edges, with an small air space in between. I think it would be a tremendous mess if you tried to 'glue sandwich' them!

2. Luckily, the windshields I'm talking about are blown, not drape molded, so no imperfections are transferred from a mold. In other words, the view through the windshield look like nothing's there. So, 2 X 0.

3. Thus the air space! Plus, I would be concerned about fretting if they touched.

4. I would say only for a new install, but I'm sure someone could prove me wrong.


Thanks for the food for thought guys,

Lance
 
Dual-pane window

drdriddle said:
Would there be any condensation issue? perhops betweeen the two in the gap?
Click to expand...

My thoughts exactly. How do you keep this from happening?

fogged-double-pane-window.jpg
 
judoka5051 said:
Hey Guys and Gals,

I recently responded to a post concerning windshield thickness, and was generally against the idea, mainly because of weight. Then I had an epiphany while trying to go to sleep. Why not make a doubler for just the windshield out of clear plexiglass? The process goes something like this:

Fit everything up as usual, but before the final install of the windshield, install a slightly small windshield of clear plexiglass underneath the main windshield. If everything is kept clean during the install and there's a good seal around the edges to keep moisture, dust, etc out, you'd never even notice the second windshield. I'd strongly recommend sicaflex (at least for the windshield) to make sure it stays put if a bird strike ever occurs.

I'm pretty sure that 3/8 (before forming, varies afterward) will stop anything under 5 lbs, but I'm going to be testing my theory using the imperfect canopies I made while leaning the process.

Unfortunately, I'll only be able make these 'bird stoppers' for canopies I can currently make (RV8, RV4, RV3)

If theres interest in this idea I'll make a form to make just the windshield portion of the canopy, so let me know!

Also, I should be advertising here shortly, I sent Doug what he needs (I hope).

Thanks, Lance
Click to expand...

MythBusters Chicken Gun | MiniMyth: https://www.youtube.com/watch?v=sCQ2oZtVNpg

An idea like this might get some traction if their was data to support the concept.

Will the double (thicker) windscreen stop an average sized goose? Who knows but I hope I never find out.
 
judoka5051 said:
Hey Tom and Sam,

In response to Tom's comment, I realize that not everyone will feel the need to do this, but some folks are 'belt and suspenders'. Remember, I originally politicked against this! Then again, I don't live where there's lots of birds on the field. I might feel differently if that were the case. As far as the gluing,,, I did mine with sicaflex, and it was a little messy, but not a show stopper. It wouldn't add much work to do what I'm talking about. Once the pieces are cut to size, then you install the smaller piece, run a bead of sicaflex, then install the main windshield as usual.

In response to Sam's questions:

1. Only the outer edges, with an small air space in between. I think it would be a tremendous mess if you tried to 'glue sandwich' them!

2. Luckily, the windshields I'm talking about are blown, not drape molded, so no imperfections are transferred from a mold. In other words, the view through the windshield look like nothing's there. So, 2 X 0.

3. Thus the air space! Plus, I would be concerned about fretting if they touched.

4. I would say only for a new install, but I'm sure someone could prove me wrong.


Thanks for the food for thought guys,

Lance
Click to expand...

OK, now that I understand the idea and process.
If it were me doing it I would build up a test article and spend a lot of time testing it.
1. If you are sealing the outer edges but leaving an air gap between the two pieces you need to ensure condensation does not occur between the panels with temperature and humidity variations that happen all the time with altitude change. You could possibly help prevent that by flooding the gap with a dry gas (nitrogen?) before sealing it but as anybody who has dual pane windows will attest, they all eventually leak and condense between the panes.
2. That brings up a second issue. If you are bonding the outer edges with an air gap between the panels now you have a sealed cavity that has to structurally deal with pressure changes. How much pressure change (altitude) does it take before something gives, what is the failure mode and is that acceptable. Also, how do you ensure that field installations are standard enough from one aircraft to the next to have a common level of performance.
3. An honest question for you regarding the blow mold process because I know nothing about it beyond the most basic details. Can you reliably repeat a shape accurately? From a production standpoint, could you alter the shape of the inner panel to allow for mitigation of any structure or fogging issues discovered during testing?
It's still an interesting idea.
 
Last edited:
Windshield

... We had a guy that flew his plane (RV-7A) to our facility in Redlands, Ca. to get all his wheels modified with our sealed bearings Etc. We noticed his windshield molding was carbon fiber and removable with screws. In talking to him about this we also discovered that his windshield was 1/2" thick Lexan. He stated that it was very expensive to have made, but not nearly as much as plastic surgery or a funeral. How do you argue with that? I guess his friend took a bird through a windshield, lost an eye and required lots of reconstruction surgery. He said when he got back home he would forward us all the contact information about the installation and the fellow that did it. Still waiting! I was very impressed with this, and want to check into it more. I will post any new info we get. Thanks, Allan..:D
 
Another consideration

Just a thought here since it hasn't been mentioned....

If you take two solid objects...seal them together at the edges....what happens to the trapped air as you climb? Lance, if you go this route, I think consideration should be given for small air relief holes.
 
Hwood said:
Just a thought here since it hasn't been mentioned....

If you take two solid objects...seal them together at the edges....what happens to the trapped air as you climb? Lance, if you go this route, I think consideration should be given for small air relief holes.
Click to expand...

....This potential problem was mentioned in an earlier post and is easily addressed by pulling a vacuum between layers prior to sealing. End of issue!...:D
 
Windshild

Piper tried the double side windows in the 60's in Commanche, Twin Commanche and Aztec. They didn't hold up very well. The standard since in many cases is much thicker windows, especially the windshield. 1/2" thick windshields are quite common on Bonanzas.
It would probably take more than 1/2" to survive a bird strike at 200 m/h.
Lear 23 does not have a certified bird proof windshield. Many years ago Lear 23 hit a large bird on takeoff killing the captain.
Convair 580 which is certified bird proof, large bird went thru the windshield. I never found out what happened to pilot.
Birdproof certification means windshield survives a certain weight chicken carcass fired out of a cannon. I does not mean the windshield would survive impact with a larger bird.
It would probably take 2" of lexan to stop a large bird, even at 200 m/h.
 
I don't know the veracity of this, but I've read that because Lexan is so 'elastic', it's not really suitable for windshields. Explanation was that it will stretch so much that the projectile can push it back, into your face, and then the plastic just recovers its shape. Anyone know what's actually used in jets?

Really hard to imagine the optics of a 2 layer 'blown' windscreen being good enough to see through safely.

Charlie
 
Two points...

1) I've witnessed chicken cannon testing on a transport-category aircraft with a center aluminum dividing pillar between the left and right windshield halves. It was the pillar attachments which failed in this case - that's riveted aluminum structure we're talking about, not plastic windshield!

2) I've owned a salvage aircraft which hit a dirt berm at 80mph. The builder of the aircraft had opted to install a standard-thickness windshield but had chosen to use Lexan. In the crash sequence the fire extinguisher which had been mounted on the aft baggage bay bulkhead broke free from its plastic mount (plastic fire extinguisher mounts are outlawed in Canadian aircraft for just this reason) and became a projectile in the aircraft. It traveled forward and hit the windshield which clearly bowed forward with the impact, then was relaunched downward and aft, caving in the top of the aluminum glare shield before traveling all the way aft to take out the baggage bay bulkhead.

These experiences make me believe that a Lexan windshield of any thickness is a bad idea. They also make me understand that beefing up the windshield itself may cause impact loads to fail other structures which have not been similarly beefed up.
 
Somebody should just invent a HUD for RV's with a secondary impact resistant / bird deflection capability.
 
Round two...

Two bits of news friends!

First, while I'd still like to investigate the two layer idea, which I will, even if only to do a compare/contrast; Meanwhile, I am also going to test 3/8 plastic for a single thickness option. I might as well get the most out of the 'chicken cannon'.

In other news, I've bought a machine to do drape forming and plan to start making canopies for the 6, 7, 9. It's going to take a little while to get tooled up for that, but I expect to have it up and running by December.
 
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