Discusion Thread: Raceair Skylite Build and sub-kit developments

[GeeZee]

After we hijacked erkki67’s thread about the Aerotique we started talking about Aluminum tubes for the Skylite. I have prices from Tube Service and thought this info would be better here in the Skylite thread. All 6061-T6 Drawn tube.
First off they left off the request for 2.250 x .083 tube. They probably just missed it. May call or request another quote.
qty 2: 2.250 x .125 x 12ft ($28.01/ft) = $672.24 (beefed up front spar that I’m considering)
qty 2: 1.750 x .083 x 12ft (14.56/ft) = $349.44 (rear spar)
qty 3: 1.500 x .035 x 12ft ($10.56/ft) = 380.16 (aileron spar need 2 and about a third so some extra here).
I included some other Al tube for the empennage, etc. quantities are just guesses right now. Anyway the entire order with taxes and some other misc charges was $2002.26. This is FOB Aurora CO. So shipping will be interesting. ACS wanted nearly $400 to ship this size material from Chicago to Indy. I’m guessing shipping would be $300-600 from Aurora to a freight warehouse in Indy? Another huge concern is packaging. would it be a long wooden crate or a giant mailing tube or just all the tubes wrapped together with stretch wrap? What will packaging cost. Need to call and actually talk to someone about that. Almost a week doesn’t go by that I hear of freight damage on something. So these prices are pretty high but compared to say a badlands kit it’s still pretty cheap. The cheapest Badlands kit was going to be $17k after taxes and shipping.

 

[addicted2climbing]

After we hijacked erkki67’s thread about the Aerotique we started talking about Aluminum tubes for the Skylite. I have prices from Tube Service and thought this info would be better here in the Skylite thread. All 6061-T6 Drawn tube.
First off they left off the request for 2.250 x .083 tube. They probably just missed it. May call or request another quote.
qty 2: 2.250 x .125 x 12ft ($28.01/ft) = $672.24 (beefed up front spar that I’m considering)
qty 2: 1.750 x .083 x 12ft (14.56/ft) = $349.44 (rear spar)
qty 3: 1.500 x .035 x 12ft ($10.56/ft) = 380.16 (aileron spar need 2 and about a third so some extra here).
I included some other Al tube for the empennage, etc. quantities are just guesses right now. Anyway the entire order with taxes and some other misc charges was $2002.26. This is FOB Aurora CO. So shipping will be interesting. ACS wanted nearly $400 to ship this size material from Chicago to Indy. I’m guessing shipping would be $300-600 from Aurora to a freight warehouse in Indy? Another huge concern is packaging. would it be a long wooden crate or a giant mailing tube or just all the tubes wrapped together with stretch wrap? What will packaging cost. Need to call and actually talk to someone about that. Almost a week doesn’t go by that I hear of freight damage on something. So these prices are pretty high but compared to say a badlands kit it’s still pretty cheap. The cheapest Badlands kit was going to be $17k after taxes and shipping.

Wow... materials prices are nuts right now... I was hoping Tube Service woudl have been cheaper than Spruce. I have not had a chance to search for prices on materials yet, but if I find lower prices will post here.

 

[GeeZee]

Wow... materials prices are nuts right now... I was hoping Tube Service woudl have been cheaper than Spruce. I have not had a chance to search for prices on materials yet, but if I find lower prices will post here.

I’m considering starting on the fuse and holding off on a decision on the wings as long as possible in hopes that this supply chain stuff will get better ( yea I know, you all can stop laughing).
1. Wing options are: just bite the bullet and pay the price for tubes.
2. build a wood spar wing (legal Eagle). Wood spars/ shipping may not be much better. Haven’t found a local source for wood yet.
3. Build a wing based on the Carlson extruded spars?

 

[addicted2climbing]

Been a while since I had any time to work on the Skylite design. I am about to have a fuselage built for me and prior to that wanted to make a quick change to the control column. The version for the Skylite and Lil bits are vastly different. The Skylite version had a large diameter aluminum tubes and 4130 brackets and gussets added to it with pop rivets. The Lil Bitts was all 4130 and used much smaller tubes and I feel that the all welded version woudl be better for longevity not having pop riveted main control horns. Anyhow, I finished it today and I woudl imagine what I have here is maybe just barely heavier if at all than the original version. Also it uses a lot of the same parts as the Lil Bitts now so there is commonality in bill of material items.

As you see it here complete (only missing cotter pins) is 2.2lbs. Welds are not added but I'm sure it will not add that much.



I wish my Tormach was running as I would CNC cut the angle uprights and build one of these now... When the Tormach is up and running I may build up a ready to weld kit for those building a Skylite. Or possibly a tac welded kit as the main yoke would benefit from being tacked in a jig.

Marc

 

[BoKu]

I wouldn't be loading a rod end shank in bending like this, not in a primary control circuit. Threaded rods do funny things in high-cycle fatigue. I'd suggest using the same leaves as at the other end of the walking beam.

 

[addicted2climbing]

I wouldn't be loading a rod end shank in bending like this, not in a primary control circuit. Threaded rods do funny things in high-cycle fatigue. I'd suggest using the same leaves as at the other end of the walking beam.
View attachment 124336

Hello Bob,

Thanks for the suggestion. In the plans the top of the reverser is the same see below.



The Elevator pushrod is like this:


I'm guessing Ed did not want 2 heim joints on each end of the elevator pushrod so that it could not spin. however per your suggestion that could put a lot of load on the 1/4-28 threaded portion on the Reverser. I think it makes sense to just add no adjustment at the top of the reverser connection to the pushrod and any adjustment can be made at the actual elevator connection Heim joint. This way all of the heim joints mostly have loads in Sheer in the axis of the thread.

your thoughts?

Marc

 

[addicted2climbing]

Bob,

Since the walking reverser linkage will sway back and forth with aileron movement and thus the elevator pushrod will sway as well maybe Ed wanted to take advantage of the ability for the heim joint to take off axis movement. If I have a direct connection, it may bind a bit or feel odd on the stick. I could use a spherical bearing captured in a rigid housing and get the same thing but not have large loads on a thread.

Thoughts?

 

[Victor Bravo]

The reverser can't spin with that bolt going through the middle of it.

 

[addicted2climbing]

The reverser can't spin with that bolt going through the middle of it.

I was talking about the elevator pushrod. Seems it make sense to move the reverser Heim to the pushrod, but doing so will open it up to spinning on the threads since there is a heim joint on the other end already. I feel I should only have one Heim joint and one non flexible joint on each end to avoid this and also to avoid having an off axis load on the 1/4-28 thread.

I actually have a bunch of these items below left over from the 3D camera systems I built and could still have some off axis flexibility and no loading issues if I put them in a rigid housing on one end if desired. I can hold it in with an internal circlip.

 

[TFF]

Many control tubes have a machined end on one side instead of a second rod end. The control tube has to have an insert on both sides anyway. Make one non adjustable.

 

[addicted2climbing]

I wouldn't be loading a rod end shank in bending like this, not in a primary control circuit. Threaded rods do funny things in high-cycle fatigue. I'd suggest using the same leaves as at the other end of the walking beam.
View attachment 124336

Bob,
I made a few changes but the more I study the plans the more I realize I need some sort of spherical joint where you circled in red. Reason is as the yoke sways back and forth the elevator connection needs to take up the miss alignment. The plans below show how its done.



So my question to you is are you saying because its threaded in that is the issue and it could work loose. Or is it the fact that I have so much threaded portion exposed for adjustment that it could fatigue over time and crack?

I have 2 solutions:

Easiest: I thread it all the way in so none of the thread is exposed. I can use RED locktite or even add a tack weld once its installed. I then adjust the lower ears to be equidistant from the pivot point ot keep the 1:1 ratio and weld. I would use a jig for this.

More difficult bore more robust. Part is not the easiest to make though for a home builder. I would need to supply it. I machine a keeper in Steel with a spherical bearing and its held in place with Circlips. It has a shank that then can be welded into the reverser tube. Same jig above would be needed. Red squiggles are welds. This seems a bit overkill when I think the easier method will suffice.

Your thoughts on this?

 

[addicted2climbing]

I might step up to a AN4 bolt and Spherica bearing since the AN3 size above only has 22 degrees if deflection so 44 degrees movement total. The AN4 size has 27 Degrees so 54 Degree total. However there is one on the other end of the pushrod at the elevator and it adds more compliance as well.

 

[User27]

Put the bearing in the end of the horizontal push rod rather the vertical reversing link? Achieves the same thing.
I agree that loading the thread in bending is not great in the long term.

 

[addicted2climbing]

Put the bearing in the end of the horizontal push rod rather the vertical reversing link? Achieves the same thing.
I agree that loading the thread in bending is not great in the long term.

To do that I need to splay out the mounting tabs on the reverser quite a bit to make room for the washers to allow full deflection in the spherical bearing when mounted in the elevator pushrod. But its doable if OK to have a heim joint on each end of the elevator pushrod.

 

[TFF]

RVs use rod ends on both sides of the push rod. They need lock nuts so it shouldn’t be a rotation issue. Although different applications, there have been crashes where rod ends were loaded perpendicular to the threads and the rod end break. As drawn probably solved other issues. With the breakages, it’s been a time in service catching up with the engineering. 70s-80s homebuilts are getting to the hours of aged aircraft and most owned not by builders.

 

[poormansairforce]

Why aren't you just using a square tube with the rod end drilled horizontally with the rod end pointed to the rear of the plane? Save a lot of fab time. Three holes and and relieve a space for the lower rod end and you're done.

 

[BoKu]

Note that the rod end in those original blueprints has 3/16" bore and 3/8" shank--a pretty beefy unit. Those Fafnir RE3M6-2N were WWII surplus and pretty cheap and common up to the 1980s, now they are rather pricey.

Overall, it is not good practice to load a rod end shank in bending unless you consider the long term fatigue properties. And when you do that, you usually end up upsizing the rod end so much that there are better and lighter solutions. In the case at hand I'd put the rod end on the push-pull tube so it reacts forces only along the shank axis.

 

[GeeZee]

Well, glad you are considering 4130. I missed that tube when ordering Al. I just order $1900 of Al tubes from Wicks. They had pretty decent prices and were offering an additional 10% off during sun-n-fun. Downside is shipping could be $400-500. I “think“ I have most of the tubes that need to be full length. Spars, struts and empennage. I ordered extra on several of the smaller diameter empennage pieces. I’m getting ready to get ready for the build. Still need to build some kind of a brake to form the rib C channels. I have most of the steel for that but still need to visit the local steel supplier.

 

[addicted2climbing]

Note that the rod end in those original blueprints has 3/16" bore and 3/8" shank--a pretty beefy unit. Those Fafnir RE3M6-2N were WWII surplus and pretty cheap and common up to the 1980s, now they are rather pricey.

Overall, it is not good practice to load a rod end shank in bending unless you consider the long term fatigue properties. And when you do that, you usually end up upsizing the rod end so much that there are better and lighter solutions. In the case at hand I'd put the rod end on the push-pull tube so it reacts forces only along the shank axis.

Bob,

While Fafner is mentioned in the plans there is no actual part number to say it has 3/8" shank. In fact elsewhere in the plans it shows a standard 1/4-28 threaded Ball end and McMaster has loads of them in various versions. The high strength version is still very affordable. Lil Bitts also uses same ball ends. See below for elevator pushrod with 1/4-28. I am gonna just add the rod end on both sides of the elevator as discussed. The suggestion to just use a Square tube is also good, but that may cause some collision issues with a cross brace in the fuselage with the rod ends terminating horizontally so going the above mentioned route is likely best.

 

[addicted2climbing]

Well, glad you are considering 4130. I missed that tube when ordering Al. I just order $1900 of Al tubes from Wicks. They had pretty decent prices and were offering an additional 10% off during sun-n-fun. Downside is shipping could be $400-500. I “think“ I have most of the tubes that need to be full length. Spars, struts and empennage. I ordered extra on several of the smaller diameter empennage pieces. I’m getting ready to get ready for the build. Still need to build some kind of a brake to form the rib C channels. I have most of the steel for that but still need to visit the local steel supplier.

If your gonna build a Skylite, keep in touch with me, I can supply you updated sub plans that deviate a bit from Ed's and you then can decide to adopt the mods or not. I am about to have a fuselage made for me since the person I found use to do many of the weldments for Bede, Bearhawk before they moved to mexico, Graham Lee, Vans and a few others. So needless to say he has way more experience welding then I do and he's retired and looking to keep busy.

Also since your gonna weld your own, I can supply you with the fuselage CAD model in a format you can use to just look at for visualization needs and no CAD skills required. You will be able to rotate the view into any angle to get a better idea of where a tube goes if you want more clarity when building.

Before he starts, I need to mock up the seating in the skylite with the cabane height. Ed says I need to increase the cabane height 2" for my height of 6' 4", but I want to be able to wear a helmet and may need 3". A quick wooden mock up will help decide that. Also if this happens I will bump up the cabane tube wall thickness to the next size up per Ed's suggestion. If I could find a human CAD model I could test it without a mockup, but I have yet to find a human model I can easily change the limb sizes. Plus physical mockup is easy and will likely tell me more anyhow.

Control Column in fuselage. The pillow blocks are simple place holders and will be 2 pieces.