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Landing light lens questions

propsync

Well Known Member
Hi Group,

I've read a few threads re landing light lens's but still have a few questions.

First, page 15-08 would have me attach the leading edge of the wing to the spar before page 15-09 has me install the landing light lens. I'm guessing its probably best to do the lens before attaching the leading edge to the spar, do you agree? Is there a reason I should attach the LE to the spar first??:confused:

Next, as far as installing the lens is concerned, Step 1 basically says the following- "Be aware of curled edges on the lens". What are they driving at here?

Then it goes on to say to place the lens on the outside of the leading edge (over the leading edge). I notice right off the bat that it fits over the outside of the LE better one way than it does the other way. I presume I should use the better fit correct? Here are two pics.

14lo39.jpg


4u6mgy.jpg


And final question, the directions essentially say to trace a line 3/4 inch. What about where the rivets will be, it seems that 3/4" is not an exact enough measurement to take the rib into account? See pic.

18dds0.jpg


As always, thanks for you help!
 
Work slow and you can trim away more plexi as needed if it doesn't quite fit. It does fit one way better than the other, so use that orientation. Also, use a plexi bit or a dulled drill bit to drill the holes or you risk a crack. I went through 4 lenses before I was happy with the fit; the shape and thickness of the plexi is such that it is REALLY hard to get a snug fit at the very leading edge. Pull the lens in super tight while drilling. I settled for a bit of a gap between lens and the very tip of the LE, but would like them to make a thinner, more flexible lens that would conform to the shape better. The lens on the 172 I fly is about half the thickness, so I know strength isn't an issue. When you're done, don't overtighten the mounting screws or you risk cracking the lens as well (ask me how I know); I probably should have countersunk the plexi a bit more but was concerned about widening the hole and loosening the fit even more. I have no idea what they mean about curled edges, maybe just the way the plexi curls up when cut.
 
Work slow and you can trim away more plexi as needed if it doesn't quite fit. It does fit one way better than the other, so use that orientation. Also, use a plexi bit or a dulled drill bit to drill the holes or you risk a crack. I went through 4 lenses before I was happy with the fit; the shape and thickness of the plexi is such that it is REALLY hard to get a snug fit at the very leading edge. Pull the lens in super tight while drilling. I settled for a bit of a gap between lens and the very tip of the LE, but would like them to make a thinner, more flexible lens that would conform to the shape better. The lens on the 172 I fly is about half the thickness, so I know strength isn't an issue. When you're done, don't overtighten the mounting screws or you risk cracking the lens as well (ask me how I know); I probably should have countersunk the plexi a bit more but was concerned about widening the hole and loosening the fit even more. I have no idea what they mean about curled edges, maybe just the way the plexi curls up when cut.

Do you know if there is such a bit for dremmels?
 
I'm not at this step so I don't know, but would it be possible to heat the plexiglass with a heat gun while pulling it in to get a good fit? Or perhaps would that damage or make the pleixiglass too brittle?

That may be a good idea, I may try that. For now the wings are sitting in the cradle mostly done, so I may wait until near the end of the build. For all I know the one for the -14 may fit much better, but I was never 100% satisfied with the fit in the -9.
 
Hi group,

One of the RV9 builders commented on my log that his duckworth lenses came with a gasket type material to fit between the lense and leading edge. I don't see any mention of this in the plans or inventory that I'm aware of.

I have to believe that even if you get a perfect fit, 200mph water is going to make its way in there without some kind of gasket.

Thoughts?:confused:
 
Hi Group,

I've read a few threads re landing light lens's but still have a few questions.

First, page 15-08 would have me attach the leading edge of the wing to the spar before page 15-09 has me install the landing light lens. I'm guessing its probably best to do the lens before attaching the leading edge to the spar, do you agree? Is there a reason I should attach the LE to the spar first??:confused:

Next, as far as installing the lens is concerned, Step 1 basically says the following- "Be aware of curled edges on the lens". What are they driving at here?

Then it goes on to say to place the lens on the outside of the leading edge (over the leading edge). I notice right off the bat that it fits over the outside of the LE better one way than it does the other way. I presume I should use the better fit correct? Here are two pics.

14lo39.jpg


4u6mgy.jpg


And final question, the directions essentially say to trace a line 3/4 inch. What about where the rivets will be, it seems that 3/4" is not an exact enough measurement to take the rib into account? See pic.

18dds0.jpg


As always, thanks for you help!

Pick up your L.E. assembly and note that it can be twisted along its length. If it is twisted while you fit/drill the lens, the lens wont fit once the L.E. is attached (rigidly) to the spar.

The curl is referring to the left and right edges of the lens, that can get a curl on it during the forming process. Some are worse than others. Lay a straight edge on the surface span wise in a few places and you may be able to see it.

Look at the airfoil shape from the wing tip end. It is not a symmetrical shape, so the lens will only fit properly one way.

Read through the entire process first (highly recommended for the entire airplane build). I think the 3/4 is an initial rough cut that will be finished to a closer fit near the end.
 
I settled for a bit of a gap between lens and the very tip of the LE, but would like them to make a thinner, more flexible lens that would conform to the shape better. The lens on the 172 I fly is about half the thickness, so I know strength isn't an issue. When you're done, don't overtighten the mounting screws or you risk cracking the lens as well (ask me how I know); I probably should have countersunk the plexi a bit more but was concerned about widening the hole and loosening the fit even more. I have no idea what they mean about curled edges, maybe just the way the plexi curls up when cut.

1/16 thick material has been tried. It is much more fragile. Cracks much easier while drilling and machine countersinking. Cracks much easier if screws are over tightened. The only way to have a more flexible lens is to use a different material. The more flexible material would require a lot more screws to keep it laying tight, and it would scratch more easily.
 
Now might be a good time to invest in some plexi drill bits. I found the grinding instructions to make a plexi bit from a standard one, but decided to buy them from Avery's. They worked great!. I have cracked many pieces of plexi in the past with standard drill bits.

I can send the grinding instructions if you want them. edit: Go to sport aviation.org and the april 2013 issue. there is a picture of the bit, but "original" and "modified" are labeled backwards.

Happy Building!

http://www.bertram31.com/proj/tips/drill_acrylic.htm
 
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Hi group,

One of the RV9 builders commented on my log that his duckworth lenses came with a gasket type material to fit between the lense and leading edge. I don't see any mention of this in the plans or inventory that I'm aware of.

I have to believe that even if you get a perfect fit, 200mph water is going to make its way in there without some kind of gasket.

Thoughts?:confused:

Any comments on a gasket? That's why I revived the thread.
 
Be careful when using a gasket. If you get a nice tight fit without, then add it, the lens can be a lot more prone towards cracking.
If you do use something, make sure it has very low compression resistance.
 
also as with any plastic lens... light tight, do not crank down the screws and lock them down, you will crack the lens gasket or no gasket. :)
 
Reviving an old thread.

I just did the lens on the first of my QB wings - followed instructions to the letter. When I match drilled the lens to wing, I pulled it up very tight to leading edge, but after all the subsequent steps, when I screw lens in there's a 1/16 or so gap at the leading edge - a bit more inboard.

I don't see how this could get better with another part as I have already drilled the wing holes to #27 and dimpled them. I may try deepening the lens material countersinks a bit - but the main question is what would be a good way to seal the edges where there is a gap?

I'm assuming that there's more experience with this now.

Thanks!
 
Me Too!

Reviving an old thread.

I just did the lens on the first of my QB wings - followed instructions to the letter. When I match drilled the lens to wing, I pulled it up very tight to leading edge, but after all the subsequent steps, when I screw lens in there's a 1/16 or so gap at the leading edge - a bit more inboard.

I don't see how this could get better with another part as I have already drilled the wing holes to #27 and dimpled them. I may try deepening the lens material countersinks a bit - but the main question is what would be a good way to seal the edges where there is a gap?

I'm assuming that there's more experience with this now.

Thanks!

I also ended up with a small gap on on the leading edge lens to skin fit. Like you, I had the lens pulled/pushed as tight as possible when match drilling the skin holes to the lens. At that time the lens fit very tight with no gap. However; after final drilling, countersinking, attaching mounting brackets, and installing, I ended up with the gap. Mine is mostly on the leading edge lower side. Both left and right wings ended up about the same. If I had to do it over again, and I might:), I would ensure (thought it was this time) the drill bit is perpendicular to the skin when match drilling (or even angle the bit slightly aft on the lens). Not sure, but if I decide to leave as is, maybe a very small bead of black RTV after paint and final installation might not look too bad.
This is not final installation, and things still need dressed up bit. Also,I used the longer screws for the nutplates as initially called for in the plans. The screw call out has since been changed to shorter lengths so very little threads will be visible.
Still trying to figure out how to post pics, but here goes.
https://photos.app.goo.gl/Kig4IVBJxgwLAFfg2
https://photos.app.goo.gl/KhhSpZNDw30KujIK2
https://photos.app.goo.gl/gLAYN5wjuMAwkY5I3
 
I also ended up with a small gap on on the leading edge lens to skin fit. Like you, I had the lens pulled/pushed as tight as possible when match drilling the skin holes to the lens. At that time the lens fit very tight with no gap. However; after final drilling, countersinking, attaching mounting brackets, and installing, I ended up with the gap. Mine is mostly on the leading edge lower side. Both left and right wings ended up about the same. If I had to do it over again, and I might:), I would ensure (thought it was this time) the drill bit is perpendicular to the skin when match drilling (or even angle the bit slightly aft on the lens). Not sure, but if I decide to leave as is, maybe a very small bead of black RTV after paint and final installation might not look too bad.
This is not final installation, and things still need dressed up bit. Also,I used the longer screws for the nutplates as initially called for in the plans. The screw call out has since been changed to shorter lengths so very little threads will be visible.
Still trying to figure out how to post pics, but here goes.
https://photos.app.goo.gl/Kig4IVBJxgwLAFfg2
https://photos.app.goo.gl/KhhSpZNDw30KujIK2
https://photos.app.goo.gl/gLAYN5wjuMAwkY5I3

Pretty much what I was thinking - or some foam tape around the edges so it won't be so hard to remove lens to service lights down the road. I was pretty careful to stay perpendicular when drilling - I had an assistant so plenty of hands. I think it's just the tolerances, ability of screw/dimple/countersink alignment to slip a bit and the inherent shape of the lens "stacking up". I talked to Vic Syracuse about it as well and he suggested some kind of seal around the edge - mentioned Duck Works kits having a seal for this sort of issue. I probably won't think about it much until final install.

Another question - what did you use to adhere backing plates to lens? I initially tried double-sided tape but it has some thickness that allows the nutplates to "sag" against lens when screws are snugged up. What's safe to use on plexi?
 
Another question - what did you use to adhere backing plates to lens? I initially tried double-sided tape but it has some thickness that allows the nutplates to "sag" against lens when screws are snugged up. What's safe to use on plexi?

Turner-

You really don't need anything to secure the backing strips to the lens. I used waxed cord to temporarily hold the strips in place while a couple of screws could be installed. Below is a link with photos showing how I installed the lens/backing strips in the wing of a RV-12.
http://www.dogaviation.com/2016/08/landing-light-lenses-instillation-woes.html

Happy building,
 
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Turner-

You really don't need anything to secure the backing strips to the lens. I used waxed cord to temporarily hold the strips in place while a couple of screws could be installed. Below is a link with photos on how I installed mine.
http://www.dogaviation.com/2016/08/landing-light-lenses-instillation-woes.html

Happy building,


The string idea is pretty slick. I had the same issue with the double sided tape, so I just ended up holding it in place with my fingers until I got two screws started.
 
Originally Posted by mturnerb
Another question - what did you use to adhere backing plates to lens? I initially tried double-sided tape but it has some thickness that allows the nutplates to "sag" against lens when screws are snugged up. What's safe to use on lexi?

Turner,
I used proseal. Not sure I would do it again though. I did a little research and couldn't find much on the subject of compatibility with the plexiglass long term.
To check adhesion, I did a test using some of the scrap plexi trimmed from the lens and a piece of aluminum. I scuffed the plexi pretty good and cleaned with naphtha. After the test piece cured, I pulled the pieces apart. Definitely enough adhesion to hold the pieces together, but not like when bonding aluminum together..as expected.
For final assembly of the lens, I applied the proseal to the brackets using an acid brush with trimmed bristles and then clecoed in place with silver clecos through the nutplates. After the proseal set up slightly, I removed clecos and screwed lens in place in the leading edge.
Like I said probably wouldn't do it that way again. Even though I had the lens taped up to prevent proseal where I did't want it , I still had a bit of a mess when the proseal squeezed out from the clecos and screws. I still have a bit of cleanup to figure out there.
Looking back, I think this is a good case for the "kiss" principle. I like John-G's string idea,...especially if you're able to get your fingers on the backing plate to hold some light pressure when tightening the screws.
 
Leading Edge Profile is the Culprit

Hi All,
I'm slow-building my wings and I've just gotten to the step where I'm installing the landing light lenses. As others have mentioned, I too have a gap at the leading edge no matter how hard I push from the inside. I made sure to orient the lenses correctly, i.e. there is definitely a right side up, but I think I understand now why the lenses don't fit better-it's the shape of the wingskin leading edge. At least it is on my wing. A closer look reveals that the radius of the skin leading edge is tighter than that on the lenses (and the ribs for that matter). I don't know about the rest of you, but when building my outboard leading edges I had to push pretty hard to get the ribs far enough forward to get the rivet holes to line up with those in the skin. The same phenomena is happening with the lense where the leading edge skin has a tighter radius, therefore the lense will not fit tight up against the inside of the skin. Picture trying to get the curve of a baseball flush with the curve of a golf ball; it simply won't fit flush.
I've already done all the trimming so the next step is to match drill the holes for the backing plates. I think I'm going to ask someone to help with this step so that one can drill and the other can hold the lense against the leading edge as hard as possible, but I know there will still be a gap. There is no way around it if the radii of the leading edge and lense are different.
 
Landing lights

Working on the landing light bracket, for those of you that have installed the Baja designs squadron pro lights how did you mount them to the brackets thanks Dennis
 
Working on the landing light bracket, for those of you that have installed the Baja designs squadron pro lights how did you mount them to the brackets thanks Dennis

Mine already had the halogen lights mounted. I enlarged that hole as needed and mounted the Baja on a cover plate that is screwed to the bracket. It's all painted flat black so is hard to see any difference through the lens.
 
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