Newton Airlines Big Box plane (aka Coroplast Tobledrone)

[DuncanM23]

I'm just starting out building this which I saw on Andrew Newton's channel: http://newtonairlines.blogspot.com/2023/04/big-box-plane.html
I'm using some coroplast I have getting in the way in the garage right now, plus whatever else is kicking around (includes some carbon arrow shafts).
When I've finished it, it's going to be decorated like this, with an extra D to make it a Tobledrone!

So far, I've just cut out the wing ribs and the wing panels. 14 ribs weigh 27g, and the wing panels are 187g each.

 

[DuncanM23]

With cutouts for the spar:

It's amazing how much progress you can make with hot glue.

 

[DuncanM23]

I taped up the outside of the wing, and then creased up the leading edge, but I wasn't sure which glue to use, so I made the fuse while an experimental gorilla glue piece dries!
The fuse is just a triangular tube (with a foldover for strength). And then I tried to fit a juice bottle to work as the nose, and once I squished it into the right place, I attacked it with a heat gun and it went from being square to being triangular. And this also had the side effect of attaching it - I can't remove it now!

198g for this bit. I was thinking I should reinforce it with carbon tubes in the top corners, but it seems super stiff, so maybe I can get away without it.
The wing (with the fuse in the background):

Taped but not glued:

And just placed together:

Once I have glued the wing, I need to create the V tail (that shouldn't take long), and then it's time to start on the conrol surfaces and the wiring!

 

[DuncanM23]

I sanded the upper surface of the wing and cleaned it a bit. Then added a load of gorilla glue on the trailing edge and on the ribs, and taped the edge shut before laying it upside down and putting a load of weight on it. I would normally put it the right way up, but if I did that I think the gorilla glue would flow down the inside of the coroplast and not stick to the top surface!

I'm going to leave it like this overnight and cut out the tail tomorrow. Hopefully I can do the ailerons and install the electrics on Friday as I'm off work and it's going to be too windy to fly. If it all goes swimmingly, I might get a chance to maiden it on Saturday!
(I might also print out some lettering to go on the sides of the fuse if I get a chance )

 

[DuncanM23]

I took the tape and the weights off this morning. It held the shape really well, but the trailing edge had cracks between the ribs where they hadn't glued together. So I filled those with a small amount of glue and clamped it all up:

I'll try to do the V tail parts at lunchtime.

 

[DuncanM23]

I made the V tail parts yesterday. They were pretty simple to cut out (they are basically just big rectangles), but rather than fold over the leading edge as Andrew Newton does, I added 2 bamboo skewers - one inside the flutes, and one on the leading edge (partly embedded in the plastic). I also inserted a skewer into the control surface (what do you call an elevator/rudder) so as to make that reasonably stiff, and I taped the hinge with white tape so it's not just relying on one plastic surface. You can see the skewers and the hing when I hold it up to the light like so:

 

[DuncanM23]

Today I made loads more progress - I roughed the surfaces and epoxied the tail feathers on, and then I put fillets along each join so hopefully it will be plenty strong enough. I managed to create a reasonable Tobledrone logo too, but the printer was playing up and would only do pink instead of red!

Fillets:

I also added some red tape on the upper surface, and some 9mm dowel to hold the wings on (I know 9mm is probably overkill, but it's pretty much the same size as the carbon arrow shafts I have, so I figured it was probably a good size to have):

I basically need to cut the ailerons and install all the electrics and it should be good to go, but that last little bit always takes me ages. Hopefully I will be flying tomorrow and Sunday, so it might be a few more days until this is actually ready. I have some 8x6 props and a 2016 1400kV motor, which is what it says on the plans, but it came with an 80A speed controller, so I'm wondering if that's overkill. The alternative is probably a smaller gold can 2200 motor with 7x5 prop, so I might just give the bigger one a go and see how it balances/flies.

 

[DuncanM23]

Yesterday I managed to mount the motor, and today was the ailerons. Cutting the ailerons was really hard, and so is taping up the hollow structure afterwards (I didn't want to go to the hassle of trying to fill in the gaps). I've cut both, but only taped one so far.
Motor first - screwed to the bottle top from the inside, and then the bottle top screwed onto the model. I guess I'll find out how sturdy this is in the fulllness of time!

Here you can see the inner structure of the wing and the ailerons:

I taped the rest of this one after taking the photo, but you can see how it works - one piece of tape from the aileron, and then another from the wing side, so there are 2 layers of tape in the join, even if they aren't stuck to very much. Once the servos and pushrods are fitted you won't be able to see this anyway, I'm not intending for it to have loads of travel. For the Photon I put the servos in sideways, but for this I'll probably just stick them in end up. It's a slow flyer with a large wing area and relatively deep wings, it's not some super slippery glider.
I'm gonna put end caps/plates on the wings, but I'm not sure whether I'm going to try to fill the gap at the inner edge. If I was really organised I would have put a rib there, but unfortunately I only worked this out after I had built the wing. If you are going to build one yourself - might be worth putting a double rib at the inner edge where the aileron will be cut out (could even cut the inner aileron line on the bottom surface before fitting the ribs - hell, you could even cut the ribs so you had a front and back portion and have more bracing in there ready for ailerons). It's amazing how much better the second one would be, if you were to do it a second time that is!

 

[DuncanM23]

Not much progress on this for ages, and then today I got a chance and I put the aileron and V tail servos in.
This shows the 2 V tail servos installed:

I'm not entirely comfortable with just glueing them to the coroplast, so I used a zip tie to hold them in place as well:

I forgot to take pictures of the aileron servos installed, they are basically just rectangular holes cut into the underside of the wing and glued in. Once everything was glued, I tried balancing it with everything held in pace with rubber bands. It just about balances on the spar (or a touch behind) with the battery as far forward as you can see here. I guess the best idea would be to run some servo extenders from the tail and try to put the receiver just in front of the wing.

I need to do some configuration on the receiver - it's a FrSky Archer SR6, so I should be able to have modes for regular flight, stability control (for use in wind), and auto self levelling. There are others too, but I would prefer just to keep those 3 - I hope to use the latter to help with hand launching it when on my own and stability will help if I try to fly in winds that are a bit too strong. I've not yet set one up with a regular tail configuration, so doing it with the V tail is an additional hurdle.
It's nice to make some progress on it though. I've been flying a fair bit with my foamie (whenever the wind would let me - the weather has been terrible here), and trying to configure some of my other planes, but I finally passed my A test so I can fly solo at my clubs and I don't need to concentrate on the test (and planes that would allow me to take the test).

 

[DuncanM23]

I followed the Painless360 videos that set up the SxR receivers, and it seemed to be fine for the SR6. I had to use a Y lead to get the ailerons to work, not sure why I couldn't make them function on channels 1 and 5, but now it's all balanced up (25% of wing chord) and bound with the V tail and the auto level and stabilize working.

The elastic bands were just to get everything in the right place. It's now all properly stuck/velcroed down and ready for glide testing prior to getting a prop... Now I just have to wait for reasonable weather when I'm not in work (this summer has been terrible).

 

[DuncanM23]

First test glides today. Looks pretty good to me:

PXL_20230818_155251710.TS

This is "PXL_20230818_155251710.TS" by Duncan Martin on Vimeo, the home for high quality videos and the people who love them.

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Especially since the control wire for the left V tail came off on the very first glide, so I couldn't have full stabilization on. The nose drops a bit as it loses speed, which is probably reasonably balanced when it actually has power.
There was no prop, so the next step after I fit a new control wire is to fit the prop and try to get it maidened...