This is my story about a Nube Tube that wanted to be a glider!
It all started a few months back when I dusted off my old RC equipment after a dozen or more years in the box. To my astonishment after charging the RC unit and Lipo it all worked fine. My son is five and we have been very interested in craft projects with cardboard, hot melt, and mechanics, but I always wanted to learn to fly, so we searched the web for the slowest RC plane with foam board that we could find and came across the FISH https://www.youtube.com/watch?v=kobJpBQO3hs and together we built a copycat version. Surely I can fly a slow plane?
We went flying with the FISH and I can say that it does fly, but we also had some issues. Seems we stripped the servo gears probably with stiff elevators so it only turned left and crashed - not to mention the water damage from a dewy lawn. I think we got about 10 flights (crashing gently each time), but we are now hooked! The FISH is all patched up and ready to fly with a new 10x5 slow-fly prop and plenty of tape on the front to fix the dings and hopefully weatherproof the card.
Its winter here in New Zealand and the weather has been rough, so I thought why not build a second plane while we wait for a calm day!
So here is my baby based on the Nube Tube from Experimental Airlines that meets the Simple soarer from Flitetest. nube.pdf The Nube2 is 1500mm x 750mm and I squeezed it out of three sheets of foam board (four sheets if you include the errors). Even though I wanted it to be a simple build, I like to think it has nice lines including the polyhedral wing.
The first job was the fuselage.
If you have looked at the Nude Tube from Experimental Airlines you will know Ed's technique for forming the tube. I wanted to try a slight derivative to include the tapered tail and integrate the joining strip.
To do this I have constructed three sides (two sides have the tail tapers) that fold cleanly, and then I have the half sides to join the fuselage split to allow the tapered section to fold.
My technique was to have 6mm of paper removed on all folds. I started by bending all the faces with one 'level' on the fold line and another 'level' underneath used to make the bends. I then added the joining strips (with paper removed) to one set of half tails. I used hotmelt on the half tails (front then rear to create the taper) and folded them to set the bends (I used the 'level' to ensure the bends are 90 deg). The next step was to glue, bend, and set the adjacent side to complete half the fuselage shown below.
To complete the fuselage, I glued, bent, and set the third side, and then finished the final half sides onto the joining tab using two 'levels' and two clamps loosely fitted allowing me to hold and align the seam. It worked quite well and if you follow the steps is easy to glue as you go. The hot glue gun was quite hot so the glue did not set too quickly allowing time to get everything aligned.My plan was to make the tail section flaps using woven tape hinges, so that helped me to get all the pieces out of the scraps. For tape covering there are plenty of tips on youtube and I am certainly not the best at it after one try, but if you are careful you can get a half decent job! I added a slot into the horizontal stabiliser so the vertical stabiliser could have a blade that passes through to help align it at 90 deg.
For the tape hinges, I used fibreglass tape strips approx 25mm x 25mm and joined two pieces face to face overlapping 6mm. After completing the hinges I covered them with matching red packaging tape.Cut the rear of the fuselage to match the tail angle.The tail section will eventually be hot glued into place lining up with the slot cut at the end of the fuselage. I'm thinking I will add the tail servos with short pushrods directly into the rear of the fuselage using long servo cables to connect to the radio gear in the front.The wing structure is using the Flitetest system which has three bends to create the aerofoil section and uses two thicknesses of foamboard strips as spars. I decided to make four wing sections and hot glue each one together to form the polyhedral wing. I taped the bottom flat surfaces of each join before opening the two pieces like a hinge, adding the glue, and then refolding to set the angle with the template to check the angle.
The wing tips are the same and like the Flitetest method, the aerofoil section is only 50% of the length. To Make the angles between the wings I followed the Flitetest method taking a small wedge of material from the top surface until I achieved my target angle (trial and error and holding your tongue right). Unbelievably the glued wing balances in the middle and the polyhedral turned out to be very symmetrical. I taped all the glued joints well and then added edge tape to the whole wing. I should have taped the underside of the exposed sections of the wing before folding, so that was a bit tedious in hindsight! I decided to add a popsicle stick at the rear of the wing to better support the rubberbands.
Here are the raw pieces sitting together and looking pretty good!Next stage was to make the wing mount, motor mount, RC hatch, and add the servos to the tail. The plan is to cut a section from the fuselage, add some side stiffening for the rubber band mounts, and then glue in a top plate that matches the centre wing angle. I hope this will provide more structure and help with the wing alignment.
I decided to reinforce the underside of the wing support with popsicle sticks
I removed some tape to allow the tail to be hot glued foam to foam.
So far so good, however, the vertical stabiliser while nice and straight, is quite flexible so I needed to think on that! I ended up bending two gift cards to right angles and glued them either side of the stabiliser (you can see them taped over below) - I think that next time I would make the vertical stabiliser an aerofoil section to make it easier to mount with more surface area onto the horizontal stabiliser.
I also wanted to do a quick test for the CG by placing the fuselage with the motor in place over the wing and adding the battery. It balances pretty well and there seems to be plenty of room up front so I added the tail servos before making the final placement of the battery and receiver. This build is a test build, the aerodynamics are basic and so for the rear controls, I chose to mount the servos exposed in the rear of the fuselage using short push rods. Next time I might likely build a rear hatch to hide the servos if it all works out this time!
It was surprising how much tail weight the rear servos added, so the battery will likely have to be pushed forward to balance! The battery hatch is cut and I think the next challenge is to build a bulkhead to hold the battery from flying out the front through the motor mount in a very likely crash!I decided to extend the nose 35mm to ensure the CG would work without adding any extra weight and then hot glued the motor mount into place.Time to tidy up the hatch cover for the battery, radio, and ESC then its done!
Yay, it's finally assembled and balanced for flying. I have really enjoyed making this plane and all the preparation required in advance. So far everything seems to be working (testing the system) but from a little more research I think I will reduce the degree (angle) of flap movement by shortening the connection of the push rod wires to be closer to the servo centres before taking to the air. Its still raining and blowing outside these days so we have our fingers crossed for when the weather settles.
I had this crazy idea to add aileron flaps to the wings but rather than use them for turning, I was thinking to connect them in unison and switch them to be level or down to slow the wing for landing - the technical term is 'crow' braking, but I am certainly getting ahead of myself and certainly my flying skills, so that will have to be for another day!
I wonder if it will fly!
Todays the day, a beautiful winters afternoon for what could be my first flight of the glider! As I mentioned before I am an absolute beginner, so I expect to crash - I'll put the FISH up first as a sacrifice!
Sadly the FISH incident broke the prop, so today we can only test the NUBE's glide performance (which in hindsight is probably a good idea). Ready, set, GO
With the prop breakages I decided to get a folding prop, without knowing any better, I ordered an 11x6 which was the closest to my broken 10x5 slow fly prop. With a quick prop test, we are ready to go when the weather settles again!
with a 1.5m wingspan and fully loaded with gear it is weighing in at 1kg.