[avi8tor50]

Working on fitting the windscreen. Everything is lining up nicely except there is a large gap between the plexi and the aft portion of the forward skin (on the side) as it comes back toward the rollbar.
Anyone else have this problem and if so how did you solve it?

Peter K
9A QB

 

[erich weaver]

yup. I minimized the gap as much as possible by using relatively large spacers between the roll bar and the windscreen. After that, I was still uncomfortable with the gap between the skin and windscreen, so I epoxied in a piece of rigid foam to fill it in. Oversize the piece of foam, then sand it down till its flush with the windscreen and tapers down to nothing on the skin. Seal the exterior of the foam with more epoxy, then your fiberglass layups can go right over the top of it. Im getting compliments on my wind screen faring now. The foam is available from ACS but I dont know the part number offhand. Its blue in color and its easiliy cut with a band saw.

Helpful?

erich

 

[Rick6a]

....... a large gap between the plexi and the aft portion of the forward skin (on the side) as it comes back toward the rollbar.....how did you solve it? Peter K..

Just encountered a similar condition yesterday as I continue fitting the plexiglass on the -8....... I'll do what I did to address the ill-fitting gap on my 6A slider....stack washers as required.

 

[Ironflight]

....stack washers as required.

Hey Rick, another solution is to build up a fiberglass "wedge" between the plexi and the frame tube for the portion where it stands away from the tube. I think it gives better support that the "point solution" of the washers, and looked a little better to me....I used some trimmings from the canopy skirt, laminated then together into the thickness I wanted, then carved them down to the wedge shape I needed.

Just one more solution I stole from someone else...

Paul

 

[avi8tor50]

Erich-Do you have any photos of what you did?

Also-thanks to others for replying. My problem is between the SKIN and windscreen as the forward skin comes back to the rollbar. There is a large gap at the bottom of the plexi extending from the rollbar forward for about 6-8 inches. The plexi sticks out from the skin which would make it very difficult to get the fiberglass faring to go from the plexi to the skin in a pleasing fashion.

 

[erich weaver]

Avi8tor50:
I'll check my photos at home, but Im not sure that I have any photos other than from after I already did my fiberglass layups.

Here is a little more info:

I think this is the foam I used:

http://www.aircraftspruce.com/catalog/cmpages/styrofoam.php

It should be able to be shaped by sanding without much difficulty. If not, its the wrong stuff.

I temporarily glued sand paper to the skin in the problem area using spray adhesive. Then I took an oversized chunk of the foam and rubbed it against the sand paper on the skin in short, fore and aft/up and down strokes until the shape of the foam perfectly matched the curve of the skin. Remove the sandpaper and adhesive from the skin, then scuff the skin area with 60 grit. Then put a thick layer of epoxy resin on the shaped side of the foam block to seal it and permanantly attach it to the skin. Seal up the finished foam wedge with resin and you are ready to do your fiberglas layups, which will now be fully supported and perfectly shaped.

One detail: A small sliver of the foam wedge you created will be exposed between the windscreen and the interior glare shield, and may later be visible from the outside, or perhaps from the insided if one were to peek over the top of the glare shield (you will see what I mean when you are test-fitting and forming the foam block). Since the blue foam looks out of place and ugly there, I waited until I had the foam block perfectly shaped, and before attaching it to the skin, I painted the small area that will remain exposed black to match the top of the glare shield. You must seal the area to be painted with resin before you paint it or the paint will EAT the foam that you just shaped to perfection (ask me how I know this).

This really isnt too hard, nor does it take all that long if you dont count the time for the resin to dry. Dont be afraid to do a quick and dirty trial run (without epoxy) with some cheapo floral foam to get an idea of how it will go. I went from "very concerned" about my windscreen fit to "pleased", and the subsequent fiberglass layups were shaped the best where underlayed by the foam. I wouldnt terminate the layups on the foam - continue them so they overlap the skin below the foam to provide a measure of protection.

E-mail direct with more questions if needed

regards

erich

 

[Steve]

Pete,
Have you built and installed the aluminum clips along the lower edge of the windshield? They're pop riveted into the forward skin and subsequently buried in the fairing layup.

aft canopy skirts,
Steve

 

[Captain Avgas]

Erich-Do you have any photos of what you did?

Also-thanks to others for replying. My problem is between the SKIN and windscreen as the forward skin comes back to the rollbar. There is a large gap at the bottom of the plexi extending from the rollbar forward for about 6-8 inches. The plexi sticks out from the skin which would make it very difficult to get the fiberglass faring to go from the plexi to the skin in a pleasing fashion.

Peter, when the windshield/canopy is formed it has a "corner" forward of the roll bar. I have noticed that many builders do not trim back enough in that area to get a good fit of the windshield onto the forward skin near the rollbar base. If you do not trim that "corner" back enough (read lots) it sits as a high spot and then you end up with a gap where you have indicated. If you have to use significant local force to pull the plexi in at the bottom of the roll bar then you have probably not contoured the plexi enough in that location. Furthermore if you introduce any local stresses into the plexi you greatly increase the chances of cracking occuring.

But there's a trap here. You can't contour the plexi any further once you have drilled the windshield to the roll bar. When you change the contour you effectively change the hole positions. So make sure you are fully satisfied with the fit before you start drilling any holes.

 

[avi8tor50]

Bob-
I have been looking at that corner and I know exactly what you are referring to. Have been trying to find some photos to get an idea of just how far back I should trim. Trying to get some reference points either on the plexi or the forward skin to know how far back to go. I have NOT drilled the plexi at the rollbar yet so I can adjust as needed.
If you have any photos of how far back you trimmed that would be really helpful.
Thanks.
Peter K
[email protected]

 

[Guy Prevost]

Jim Daniels had a nice fix here: http://home.comcast.net/~jwdweb2/Canopy2/canopy2.html

Here's a photo stolen from (and hosted on) his site:

 

[Captain Avgas]

Bob-
I have been looking at that corner and I know exactly what you are referring to. Have been trying to find some photos to get an idea of just how far back I should trim. Trying to get some reference points either on the plexi or the forward skin to know how far back to go. I have NOT drilled the plexi at the rollbar yet so I can adjust as needed.
If you have any photos of how far back you trimmed that would be really helpful.
Thanks.
Peter K
[email protected]

Pete, it's impossible for me to give you a dimension that would mean anything. But the trimming of the windshield needs to be MORE in the area where the curvature of the forward aluminium skin is greatest. I simply did it by observing the area that seemed to be taking the weight of the plexi and then taking off a very small amount at a time with a portable belt sander until I was satisfied (works like magic...so easy and no chance of cracking anything....highly recommended) . If you do it gradually (1/8" at a time) you'll SEE the bottom of the windshield coming in.

But in the end there will always be SOME gap between the plexi and the skin in the area that concerns you. This is because there must ALWAYS be some gap between the plexi and the roll bar in order for the windshield to be co-planar with the sliding canopy at the base of the roll bar.

It might be possible to PULL the plexi in against the the skin with clips (and some people do exactly that) but that would introduce very high local stresses and I don't recommend that. I think the former recommendation of using a filler in that area is the only way to go. Of course if you don't trim the windshield enough your gap can be too big in the unstressed state and therefore the transition can be ugly.....many of them are!!!

 

[avi8tor50]

Did some more trimming this passed weekend and got the gap to decrease a bit. There is a little bit of tension when I pull the plexi to the rollbar which I think is probably normal. The gap is now acceptable and I will probably do the foam/fiberglass trick to bridge the gap. Thanks for your help.

Peter K