Skylight

[S Lathrop]

Kevin;
The outside and inside pieces of aluminum for your skylight are each made out of a single sheet of aluminum, and put a joggle (recess) all the way around the inside piece to capture the plexiglass? That last step might be a bit beyond my current metal working skills, but the result sure looks nice.

One term for the process used to shape the aluminum is "upset joggle". The challenge might be more of a wood working problem.

You have a piece that is the shape of the skylight. This is the male die. The next piece, the female die, has a hole cut that is the shape of the outside of the skylight plus a gap of maybe 1/4 inch or larger to from the upset across. The male and female dies are the exact thickness of the skylight material. Next you get metal frame and the 2 dies aligned properly and then press the 3 parts between 2 flat surfaces. When I do large parts like this I work the part around in my press until I have the finished shape I want. I used a similar process to do the flanges on all my ribs and to make the frames for my rear windows, D shaped.

Looks like I am going to do this again for the skylight. I really like what Kevin D did. One advantage I can see is that when it becomes desirable to cover the skylights to block the sun, the covers will be much easier to do.

[AZBearhawk272]

So the dirty little secret is this. The skylight surface contour is in 3 plains, the outer two crown down to the side as well as fore and aft, a compound warped surface. But you think not a big issue, cause the hole in the panel is huge, it should be really floppy! Well,
NOT after the offset joggle. Which then required stretching and shrinking in TINY amounts in various locations to have the
entire panel drape smoothly over the top hump.
I would do it again as the end results is worth it.

Kevin D # 272

[whee]

Nice job Bearhwk272! You skylight looks like a great way to for for those that don't want a 1 piece skylight.

[BravoGolf]

Rob - I like your thought process and end results. I am a long way away from a skylight but I plan on incorporating your design during the build process.

[svyolo]

Kevin D. I was a fan when I saw the pictures, but knowing what you had to do to get there makes me even more so. Trying to do the same on mine would result in way too much perfectly good aluminum being turned into scrap aluminum. I think I will be fairing out the hump and using a flat piece of glass.

But awesome work.

[lamarglobe]

So, bottom line is that all modifications must be welded in some form to attach to the existing structure?

[AZBearhawk272]

Just to answer the thread question, is welding needed for skylight. Clearly the answer is no welding needed!
I verified today that either a two or three panel skylight
can be floated within the normal fabric installation of a Bearhawk. The installation I verified has been in service
for 15 years with no issues. The 1/16 inch thick skylight
is sandwiched between the inner and outer aluminum frames. The inner frame was installed on the inside of the covering with a lip on the frame captured between
the covering and the stringer. Holes drilled in the inner frame allow the fabric and frame to be rib stitched to the
stringer. Rib stitching spacing is 1 in. The interior frame is also glued to the covering fabric. The frame assembly is only attached to the structure on the stringers and the side edges. The fore and aft edges are just floating on the fabric with screws and nuts holding the sandwich together.

Kevin D. #272

[Archer39J]

I removed the hump, attached a crossbar and formers for a flat sheet of tinted acrylic, .118” thk, without any welding

[Mark Goldberg]

Looks quite strong Dave. Mark

[Nev]

This looks really good Dave. How do you plan to attach the skylight?

[Archer39J]

Just locking nuts and CRES bolts through the formers, I haven't drilled the outboard most ones on the fuse. I'm still working out how to close out the front lip, you can see my first idea in the first photo, but I need to find a thinner seal if I go that route since there's not quite enough room for the windshield with that one. I probably won't finalize this design until the wings are on, since I won't be able to position the windshield as I'd like before then.

[svyolo]

Dave;
You used aluminum channel. It looks like 3/4 X 3/4 X 1/16. I haven't decided on channel or just some angle. I have a shrinker and can shrink the angle to shape. I don't have a tubing roller. Were you able to bend the channel a little at at time until it was the correct shape, or did you use a roller to shape the aluminum channel?

[Archer39J]

Dave;
You used aluminum channel. It looks like 3/4 X 3/4 X 1/16. I haven't decided on channel or just some angle. I have a shrinker and can shrink the angle to shape. I don't have a tubing roller. Were you able to bend the channel a little at at time until it was the correct shape, or did you use a roller to shape the aluminum channel?

Yep, 3/4" x 3/4" x 1/16" 6063-T5 extruded channel from metal supermarket in Everett, I recall it being fairly cheap. I was stumped for a bit figuring out how to bend these, I finally just clamped them to the frame and did it by hand, that worked quite well. I did end up making a couple before I got it perfect, if you're too aggressive with the bend you can get some buckling in the leg like in the last photo, which wouldn't be a structural issue in this application, just cosmetic. Make sure the clamps line up with the supports on the wing former, don't want to go bending that, or the fuse tube for that matter.


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[Archer39J]

Come to think of it for an easier time I could have shaved off 1/4" from the legs on my table saw. Bending 1/2" legs would have been easier and plenty strong, I'd do that if I were making these again.

[svyolo]

My thought was bending square tube would be easier, then cut off one end. I have never tried to bend channel. Angle is easier, but I think channel looks better.

For the aft "capture" for the trailing edge of the glass, I was going to use a piece of the kit aluminum stringer with the end cut off. I will either bond that to a piece of aluminum angle, or something similar. Next week.

[robcaldwell]

My thought was bending square tube would be easier, then cut off one end. I have never tried to bend channel. Angle is easier, but I think channel looks better.

For the aft "capture" for the trailing edge of the glass, I was going to use a piece of the kit aluminum stringer with the end cut off. I will either bond that to a piece of aluminum angle, or something similar. Next week.

That's what I did. I took square 4130 and bent it. Came out very well.


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[Nev]

Anyone planning to bond the skylights in place instead of fasteners? (Or a combination)

[Archer39J]

Anyone planning to bond the skylights in place instead of fasteners? (Or a combination)

I definitely wanted it to be easily replaceable, so mechanical fasteners for me. I'm floating it on a layer of 1/16" EPDM foam as well, using rubber faced washers to seal it up too.