Windshield tips

[aviator79]

I'm being a little bit ambivalent about getting my windshield installed. I'm kind of terrified of cracking it or trimming it incorrectly. The instructions for the initial fit are a little vague about how to trim around the forward carrythrough tube. does anyone have any tips, pictures, tricks, or assistance to share about how to do this successfully?

Specifically:

-It appears to me that I need to take some material off to clear the bottom of the carrythrough tube, but I'm not sure how far to go back on top. The manual seems to say that you should go back far enough to get the hardware in, but that's a lot of material to take off. I'm wondering if through-holes would be better.

-Would it be a good idea when removing material under the carrythrough tube to put a nice round relief in to help prevent cracking during handling?

-During initial fit with the vertical edges of the windshield outside the mounting angles, I'm worried that pushing the top of the windshield into position will crack it. Those that have been successful, how did you get everything into place for the intial fit?

[Esser]

My thoughts. The windshield is way stronger before being trimmed. Getbit pretty much installed so that you won’t have to remove it again. Then take a die grinder with an aggressive sanding drum to start trimming atbthe carey through tubes. You need to take out lots there for the spar to have enough room to pivot in.

[jmodguy]

I believe the vertical edges go inside the angles. I was also wondering about not relieving the corners and just making a hole for the forward pin to go through... I don’t think I will ever fold the wings so that feature is not important to me.

[aviator79]

My thoughts. The windshield is way stronger before being trimmed. Getbit pretty much installed so that you won’t have to remove it again. Then take a die grinder with an aggressive sanding drum to start trimming atbthe carey through tubes. You need to take out lots there for the spar to have enough room to pivot in.

I definitely have to do some trimming prior to getting in on, as it interferes with the forward carrythough tube and can't seat in place as-is. I wouldn't mind seeing photos of the completed area around the carrythrough tube if you have any or wouldn't mind removing the root fairing and snapping a few.


I believe the vertical edges go inside the angles

They do, but when you first put it on, it won't fit between the angles. I believe you mark the aft edge of the angle on the windshield with the windshield on the outside of the angle, trim it, and then fit it inside. I could be mis-remembering the instructions though.

[jiott]

I agree, don't force the vertical edges behind the angles before you have trimed them at least somewhat close to final dimension. I have heard of several cracking incidents trying to do this too soon. Bottom line, you should never have to apply much force to flex the windshield into place.

Also, as was asked, yest you should never leave sharp corners, but always use smooth radiused corners, and smooth and round all rough edges to eliminate stress risers.

I had to take my windshield on and off about 5 times to get it right. Its no problem if you are careful and don't flex it in the process; 2 people make it much easier.

The trimming around the front carrythru tube- just trim enough so the tube and spar (when folding) don't touch the acrylic and allow for thermal expansion. Large gaps are not required. I used a generous clearance hole thru the acrylic for the front spar pin. The photo below shows this, but it may not be real clear.

[aviator79]

Thanks Jim, that's very helpful.

[efwd]

I laid the thing up and used a marker to draw where I thought the cuts would be made around the cross tube. Ended up I was wrong on the geometry. I could have removed far less. The good thing is, the root cuff panel covers it. The way I see it, there is no need for the extra glass that would remain over your front spar bolt should you think you would just like a through hole drilled in it. The root cuff panel covers the entire area anyhow. The dremel sanding drum is what I used as well. It will make short work of the process.

[jmodguy]

Huh... I couldn’t get mine outside the angles. I was afraid it would snap! It is an older part (95 vintage).

[Hockeystud87]

If I needed to replace my window on my model IV is the glass a special plastic or can I just grab a similar Plexiglas and find a outline to trace?

[Guy Buchanan]

For the acrylic windshield:


I would remove as much material as possible from around the forward carry-through tube. This reduces the stresses in the corner which are the nemesis of all Kitfox windshields. You can remove everything covered by the root cuff, minus whatever overlap you want. (I did about 3/8" overlap.)
Make sure you polish the edges before you apply any load.
Use holes to insert wing bolts.
Use acrylic drills (0 rake angle) and step drills to drill holes. Never a standard drill. Polish hole interiors, if possible.
Use a Dremel with diamond wheel to rough cut. Dremel with sanding wheel for female corners. Sandpaper for straight edges and male corners.
You may need to remove the aft corners a bit to clear the wing when it folds.
You know about the fastener clearance holes.

For the polycarbonate (Lexan) windshield:


I switched to polycarbonate when I saw how easily my acrylic window shattered on impact. The polycarbonate is much, much tougher; used on F-16's. Unfortunately it's also not as clear and scratches much easier.
Polycarbonate is much easier to fabricate and install because it doesn't need to be (indeed can't be) heat formed. You just cut it and bend it as required.
I did most of the same stuff above with my polycarbonate windshield.

[efwd]

Dang, that last post should be put into the builders hints and tips Guy.

[aviator79]

I received some photographs sent privately from a couple different reliable sources, and trimmed mine as they had done. Here is a picture for anyone else wondering what these should look like.

https://lh3.googleusercontent.com/8KHRy9qBP_5--m5F-Jk0iRwCGEkYCyKhdvb3AgAADGfF3DMgh30XbTgzMQudjh2Tmuh zmDM23hH0t9N-GCaOP5rfuykAA0ow_PdMU9g_KTlwbBX0zb6w5ykxw2Qt6MmEYw o3p3fh71Y=w600

[David47]

Thanks for posting Brian. I'm working this area within the next couple weeks so good to see what others are doing. The tight forming of the w/shield in this area has bothered me since the day I match drilled it at fit-up.

[klamberth27]

I received some photographs sent privately from a couple different reliable sources, and trimmed mine as they had done. Here is a picture for anyone else wondering what these should look like.

https://lh3.googleusercontent.com/8KHRy9qBP_5--m5F-Jk0iRwCGEkYCyKhdvb3AgAADGfF3DMgh30XbTgzMQudjh2Tmuh zmDM23hH0t9N-GCaOP5rfuykAA0ow_PdMU9g_KTlwbBX0zb6w5ykxw2Qt6MmEYw o3p3fh71Y=w600

Thanks for this. My manual states to use pop rivets but I think that is with the Polycarbonate. I purchased the molded one for my Kitfox IV build and am looking for the screws and nuts everyone is using for mounting. Also what type of washer is that. Looks plastic.

[Kitfox Pilot]

Thanks for this. My manual states to use pop rivets but I think that is with the Polycarbonate. I purchased the molded one for my Kitfox IV build and am looking for the screws and nuts everyone is using for mounting. Also what type of washer is that. Looks plastic.


I believe mine were #8 stainless machine screws with lock nuts under. You have to be careful and not drill to close to the center because you won't have room for the nut. The plastic washers can be bought at aircraft spruce.

[klamberth27]

I believe mine were #8 stainless machine screws with lock nuts under. You have to be careful and not drill to close to the center because you won't have room for the nut. The plastic washers can be bought at aircraft spruce.

Very good. Thanks!

[bbs428]

I ordered the new ss7 style windscreen and install kit from kitfox a few years back and it came with all the hardware. I ended up using double the amount of the seal tape to clear the wing.

[jiott]

Caution about the black seal tape, especially double layer: A number of folks have seen the tape soften up in hot weather and squish out of position to the side.

[bbs428]

Caution about the black seal tape, especially double layer: A number of folks have seen the tape soften up in hot weather and squish out of position to the side.

That's not good...thanks for the heads up Jim!

My windscreen fasteners are just snug with very little pressure, so I hope that's not the case for me. I do have some gray uv stabilized tape that's 3/32 thick if the summer heat does the stock tape in. That black tape would be a serious pita to remove now or after the heat distorted it.

[3kdscf]

Caution about the black seal tape, especially double layer: A number of folks have seen the tape soften up in hot weather and squish out of position to the side.

Yes, this is me. I hangar my kitfox in the desert where the hangar gets 140F in the summer. My black tape is halfway out and I am not quite sure how I am going to deal with it. Attempting to remove the windscreen and redo the seals would almost certainly result in cracking it. My current plan is to simply caulk it using the same type that is recommended to seal it to the boot cowl.