Build a Folding Wing FT Plane

[Craftydan]

What prevents it from rotating when the spar is pinned like the mechanism above? what keeps the wings from folding upward the moment they lift the aircraft?

With the elastic lined rod method you can place a smaller peg that will slip into the leading edge of the wing, and when you pull the wing out of the collar it will clear the peg as well, then fold back flat along the fuse, with the elastic keeping it attached to the fuse. with the pinned method the wing can't pull out of the fuselage to disengage any lockinh pegs.

Tent poles are generally fiberglass, but no reason these couldn't be carbon arrow shafts (cheap and easy to find). The beauty of the elastic method is you won't have to cut holes in the spar, just cut it to size. Only hard part you'll have to source is a stiff collar that will slip around the arrow shaft.

 

[eagle4]

I only just found this thread now. I love folding aircraft.

Glad that my folding wing got a mention.

Some of the things you'll have to combat with your folding wing is any twisting force on the wing. you will need at least 2 points joining each wing, as if its only the spar you'll have it as a pivot point for the wing to twist on.

 

[rcspaceflight]

What prevents it from rotating when the spar is pinned like the mechanism above? what keeps the wings from folding upward the moment they lift the aircraft?

There is a pin that goes straight down through the rod and into the plywood base. That pin will prevent any rotation. The two pins being 90degrees from each other prevent any folding upwards. Granted the pins are going to see a lot of stress. But I imagine these wings would be for a high wing trainer, not a fast or aerobatic plane. I also image that the battery size would be limited because it couldn't handle as much weight as a typical sized plane.

And with the tent pole idea, what prevents the arrow shaft from spinning inside of the collar? Or would you have three "paint stirrers" with one sliding inside of two and a bungee holding it together?

I don't want to poo poo the tent pole idea too much because it is a great idea. But I don't think a bungee cord (or any elastic) is a good idea. Elastic wears out and eventually breaks. Using string would be better. It's the same thing, but you have to pull it and tie it some how (probably use a clip). Also, I imagine that the bungee trying to force the two wing halves together will eventually crease the foam board when they're folded. A string will let the wing halves just dangle.

 

[rcspaceflight]

Does anybody remember those toys where you would press down on the base and the animal would fall apart. Let go of the base and it will reassemble it's self?

Those use string and a spring in the base. Not elastic. That concept would work great for folding wings. (As mentioned in last post.) But get rid of the spring and just have a way to pull the string and hold it in place (preferably with a clip).

 

[Craftydan]

There is a pin that goes straight down through the rod and into the plywood base. That pin will prevent any rotation. The two pins being 90degrees from each other prevent any folding upwards. Granted the pins are going to see a lot of stress. But I imagine these wings would be for a high wing trainer, not a fast or aerobatic plane. I also image that the battery size would be limited because it couldn't handle as much weight as a typical sized plane.

Ok, I'm seeing the pin in the locked position now. couldn't see the hole for it in the unlocked . "A lot of stress" is an understatement. If the spar were to rest in a saddle in the locked position it should take the stress off the locking pin in flight, and it *might* work (up and to the first loop), but it would probably fail next at the hinge. whatever material you choose, avoid something with a lengthwise grain. it will split on these pins under stress.

And with the tent pole idea, what prevents the arrow shaft from spinning inside of the collar? Or would you have three "paint stirrers" with one sliding inside of two and a bungee holding it together?

That was actually addressed -- you place a permanent alignment post in the fuse, that when the arrow shaft locks in the collar, the post will lock in the leading edge.

I don't want to poo poo the tent pole idea too much because it is a great idea. But I don't think a bungee cord (or any elastic) is a good idea. Elastic wears out and eventually breaks. Using string would be better. It's the same thing, but you have to pull it and tie it some how (probably use a clip). Also, I imagine that the bungee trying to force the two wing halves together will eventually crease the foam board when they're folded. A string will let the wing halves just dangle.

That's what the spar and collar are for. they hold the shape, and take most of the stress from the elastic when the wing is locked. If the wing starts to pull out the elastic is stressed but until then it's only under light tension. the elastic won't cause the wing to bend and fold -- the spar will bend *less* with the elastic installed because the elastic down the middle of the shaft will keep it evenly stressed. if the spar bends in any direction, that will increase the length of the elastic inside the spar, which the elastic will resist. when the wings are folded, all the stress is between the collar and the end of the spar. As far as dangling, with the pinned hinge, those wings will flop down any time you pick up the model.

Those use string and a spring in the base. Not elastic.

But don't you see? the spring is *inside* the elastic in the tent pole. In the toy, it's outside the chord, but it's still there. you still use a spring to set the tension on the cord. You *could* manually tension the cord with a clip or knot, but if the clip or knot were to ever slip ever so slightly, the tension would drop rapidly and the joint would loose all it's strength. the beauty of having a spring in the system is if the cord retainers slip the spring takes the slack instead of the load bearing joint, and you instead have a gradual weakening of the structure . . . and some warning.

 

[RAM]

Putting this here for reference. Still thinking how do we get the two halves supported. If we use something like this extension plank we should have enough strength even with foam spars. Just let them criss cross through the fuselage area where our bbq skewers normally cross sides. We could just pin them all together with a skewer front to back direction through the middle of the fuse. Might not be the best idea for a folding wing, time will tell.

 

[rcspaceflight]

The problem I have with elastic is not when the plane is put together. It's when the plane is apart and ready for transport. The elastic is going to want to pull the wings together. It defeats the purpose of having folding wings if the elastic is going to get stressed and eventually break during transport. When it breaks, you're going to have removable wings. It also defeats the purpose if you have to store the plane with the wings in place. If you're going to have foldable wings, wouldn't you want to be able to store it with the wings folded?

 

[rcspaceflight]

Right now I'm playing around with an "improvement" of the pin and aluminum arrow shaft idea. What if I got rid of the pin that holds the spar to the plywood plate. Instead I could extend the length of the spar so they almost meet in the middle, and then add a second plywood plate on top of the first plate. The two plates would clamp onto the spars. The spar wouldn't spin or pull out because there would still be a spar in front of the other that is clipped in place. (And can rotate inside of the clip when the top plate is removed.)





The wings will have to fold down before you could rotate them. But that was true with the system anyway.

It would actually, probably, be a lot better to use wooden booms instead of arrow shafts for the wing spars. (Which do not need to extend to the wing tip, just a few inches into the wings.) If you had a square spar, instead of round, it would clamp between the two plates better. You just need the round arrow shaft for the rotation point.

 

[RAM]

The problem I have with elastic is not when the plane is put together. It's when the plane is apart and ready for transport. The elastic is going to want to pull the wings together. It defeats the purpose of having folding wings if the elastic is going to get stressed and eventually break during transport. When it breaks, you're going to have removable wings. It also defeats the purpose if you have to store the plane with the wings in place. If you're going to have foldable wings, wouldn't you want to be able to store it with the wings folded?

The way I have it pictured in my mind, the elastic would not pull once the wings are out. How to describe it though?????

The folding wings will butt up against the fuse (or top of the fuse to a wing like structure).

Since the wings will butt up against something, it's the spar like structure that will continue on to the inside of the fuse (like fingers interlaced ???)

So,,, the shock cord will be loose/free to move when the wing ends are pulled apart from the fuse and all should fold easily once they pull past the side of the fuse. The reason they can fold unstressed is because the cord will just slip through a "finger" opening.

 

[rcspaceflight]

Apparently I have nothing better to do today. I like to follow "KISS". Keep It Simple, Stupid. I also want to stick to common, easy to find parts. Let's call this design #3 and it consists of two 6" long .5" x .5" wooden booms. One 5" long .5" x .5" wooden boom. Two .5" long wooden boom. A 5" x 5" piece of hobby plywood (or whatever for the base). Four bolts/nuts. And finally a small hinge. Like a cabinet hinge. Hopefully it's easy to find one small enough to work. Oh, and possibly four magnets mounted on a couple of clips.





Rotate the plywood clips. Possibly add magnets to them so they don't spin during flight.


The spars fold forward by use of the hinge. (Then the wings fold back on the bolts that attach the spars to the hinged boom.)


It is impossible with this system for the wings to fold up because the booms lay flat against the plate. The clips prevent the wings from falling down and prevents the wings from rotating. Flying inverted would probably be a bad idea (but possibly fine).

Instead of clips you could use a second 5" x 5" plywood plate that you could screw on top of the entire thing. Or some sort of clips to hold the plate in place. But spinning two clips held in place with magnets sounds easier and quicker than four screws.

 

[eagle4]

if you fold those latches outwards you can extend the rods inwards further, increasing the strength you'll have when its in its extended form

 

[rcspaceflight]

I was having a difficult time deciding what to build next. I settled on a "slo-stick" and when shopping for some square dowel I figured why not try out my folding wing design. I bought all the stuff and I just thought I'd let you guys know that I plan on building it.

 

[RAM]

I was having a difficult time deciding what to build next. I settled on a "slo-stick" and when shopping for some square dowel I figured why not try out my folding wing design. I bought all the stuff and I just thought I'd let you guys know that I plan on building it.

Can't wait to see the build!

 

[rcspaceflight]

I eyeballed a lot of it and it's a bit sloppy, but I have the wooden folding mechanism done. Already I can tell that the pivot point bolt is going to keep loosening it's self whenever I use it. But that's what lock tight, CA, or a double nut is for. It would also help if I actually used washers.

Materials:


Materials:


"(no aircraft use)" LOL I'm pretty sure it says that because it's Poplar plywood, not Balsa and that company/brand also sells balsa wood for model airplanes. All of the wood I bought is Poplar because I want the extra strength and I don't mind the extra weight.


Wood cut up. I cut the 12" by 6" into roughly two 6" by 6" pieces. The 1/2" square dowel is cut into roughly a 10" piece, and two 13" pieces.


I placed the two plywood pieces ontop of each other and eyeballed four holes. I installed four bolts in the holes (I plan on gluing them in place).


Then I can just put one plywood piece onto the other.


Then use Wing Nuts to quickly install the top plate.


I also eyeballed the wing spars. It's more important that the wings are square with the plane than with the plywood so I didn't bother measuring it out.


I used three of the 3/4" hinges.


Even though I did pre-drill holes for the brass screws into the plywood, I kept stripping them and ended up only using one screw per hinge. This ended up being the most difficult step.


All done!


I think I said it before, but I'm going to make a "slo-stick" which is what that 3/4" Poplar wooden dowel is for. It's probably over kill for the fuselage, but again I want the extra strength and I don't mind the weight.

I just weight it and I might have thrown caution to the wind a bit too much since what's pictured in the last picture weighs 295 grams. The stick I'm using for a fuselage weighs 125grams. But the total flying weight should be around 800-900grams. I plan on a 4' wingspan so it should still fly great.

 

[RAM]

Looks good so far. You can probably use the plate to hold your landing gear as well.

 

[rcspaceflight]

Looks good so far. You can probably use the plate to hold your landing gear as well.

That's what I was thinking. I have a pair of 2" wheels that I bought, but that might look a bit weird on such a big plane. But the plane is going to look weird no matter what.

I'm also going to bolt the fuselage stick to that plate. I mean, might as well. Only using CA seems like a bad idea. Two bolts and CA will make it stronger than it needs to be.

I've never built a multirotor, but this build feels a lot like a multirotor build.

I have yet to decide on a wing design.

 

[RAM]

I was having a difficult time deciding what to build next. I settled on a "slo-stick" and when shopping for some square dowel I figured why not try out my folding wing design. I bought all the stuff and I just thought I'd let you guys know that I plan on building it.

I found some inspiration. Watch the 30sec mark, might just work with your design, a hinged top cover.

p.s. I think we should send Josh on a roadtrip to interview these guys.

 

[AkimboGlueGuns]

Or terrafugia, considering they have actually flown their design.

 

[RAM]

Or terrafugia, considering they have actually flown their design.

I saw that one but it didn't fold the way I was imaging we could do it. rcspaceflights prototype could work with the full wing of the aero. I've been stuck on how to hold it all together. Now it's clear how simple that could be done with a hinged top cover. Some pins, some holes in the spars, and your off.

 

[rcspaceflight]

It's been too long, but I actually worked on it some more.

Locked in "flying mode".


Locked in "storage mode".


Yes the wings are pink. I bought some colored "Flip Side" foam board and it looked like the best color because of how visible it is.

I went with a 60" wingspan, but it's actually bigger than that since each wing is 30" long and there is over 12" of space between the wings. It's probably complete overkill, but I know it's going to be heavy so a bigger wingspan will keep the wing loading low.