• This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn more.

Burnelli UB-14

eagle4

New member
#1
Hey gang, for many years i've been fascinated by the lifting body fuselage designs by Burnelli, and I've recently decided to give it a crack at building one of them. I'm going to be making the Burnelli UB-14.
burnelli_ub14.jpg
This is what Its hopefully going to look like

20130421_093918.jpg
I made some thin strips of foam to design the aerofoil for the fuselage, took a couple of goes until i was happy. The plan is to have the fuselage 20cm wide, and as long as i could get it with 30 inches of foamboard.

20130421_095043.jpg
I then cut my plans out, the fuselage sides fold up using an A style fold like the ones flitetest uses (or is it a B style...)

20130421_101057.jpg
I then covered the outside of the fuselage in packing tape, I should have done this first. oops

20130421_103338.jpg
Started glueing the sides up and bending the foam.

20130421_104150.jpg
It was tough getting it glued in one go, but I managed. and I present to you the start of my fuselage.

20130421_113507.jpg
After a lot of playing with numbers and sizes i came up with a shape for my wing, its going to be tapered, but not nearly as tapered as the real one. my tip chord is almost twice what it is ment to be. i figured the extra wing area cant hurt ;) the wing dimensions are 20cm root chord, 10cm tip chord and 40cm length per wing. I made a template which helped me draw it onto the foam

20130421_123952.jpg
The wings drawn onto the foam. On top of my dimensions above i added some ailerons and flaps, the depth of which is that of my ruler, so just over 1 inch

20130421_142341.jpg
My wing pannels cut out and taped on the other side


The next steps are to get some tube and some dowel rods. my plan is to have the wings removable, for easy transport. i plan to mount a carbon tube inside the fuselage and have wooden dowels in the wings which can plug into the tube. (unless you guys have a much better idea for me.

Then I'll build the tail booms and the rest of the tail. I plan to cut out two notches out of the nose of the fuselage so i can mount some wooden motor mounts. Any advice is appreciated. as this is my first plane where i'm really just working it out as I go
 

eagle4

New member
#3
I did some more work on the plane this weekend, this time I was working on the tail section, as I'm still sourcing parts for the wings and the way i'll mount them.

i drew up a template for the tail boom sections and cut them out, i figured two pieces of foam should be strong enough for this tail (i guess only time will tell). on the inner pieces of the tail boom i added a couple of little tabs that line up to some new holes i put in the fuselage, i figured this would help with alligning them and keeping it in place.
20130427_092406.jpg 20130427_101819.jpg

I cut out the horizontal stabiliser and because i am horrible at cutting/drawing round corners i decided to go with some straight edges. (so sue me)
I did the same for the verticle stabilisers. my plan is to not have rudder control on this plane so the rudders are just drawn on ;)
20130427_113722.jpg

Once I built my tail assembly I've put it asside for now, I dont plan on glueing it onto the fuselage until much later. I figure it will be a ton easier to mount the motors and the wings without having a delicate tail boom section sticking out the back, just waiting for me to break it.
20130427_130001.jpg 20130427_144245.jpg
 

eagle4

New member
#5
im contemplating what power setup i should use for this plane. i dont have too much experience with different motors or props.

i'll have about 16-17cm of distance between the two props, so i think a 6x or a 5x prop should be ideal. would you have any thoughts?
either this http://hobbyking.com/hobbyking/store/__11329__6x3_Propellers_Standard_and_Counter_Rotating_6pc_.html
or this
http://hobbyking.com/hobbyking/store/__11328__5x3_Propellers_Standard_and_Counter_Rotating_6pc_.html

as for the motors, i was thinking just a couple of simple 1300kv motors, maybe something like this
http://hobbyking.com/hobbyking/store/__2069__hexTronik_24gram_Brushless_Outrunner_1300kv.html

I doubt it'd draw much current (i could be wrong) so i was thinking a couple of 18A esc's would be good

I plan to have this running off either my 1300mah 3s battery or my 2200 3s battery.

What do you guys think?
 

eagle4

New member
#6
i'm thinking of putting some retracts in this. i've done a quick mockup of how i think they should work, what do you think?
landing retracts concept01.jpg landing retracts concept02.jpg
 

eagle4

New member
#9
great idea pgerts. I'm thinking if I also put in a v Ben's in the landing struts it should help take some of the shock of landing, without putting all that force onto my servo. what do you reckon?
 

pgerts

Old age member
Mentor
#10
Flexible struts are always good. Don't know the v Ben's you are talking about.
yy10103.jpg

The force on the servo will not be hard if you rest the gear on to a hard beam when out and pull the gear forward into the motor pods
 
#12
I marked out and cut off some sections of the front where I could glue my motor mounts. This was nerve racking, as I didnt want to much up my fuselage that I am so proud of. The nose feels quite strong, not sure if i'll need some extra reinforcing though. we'll see.
20130511_090150.jpg 20130511_092616.jpg

I also added a piece of bbq skewer to the leading edge of the stabiliser, this is purely for strength and rigidity.

I then started making my wings. I had two 0.5 inch wide spars that i laid along side of the dowel. i then laid a 1.5 inch piece over the top, the 1.5 inch piece had its paper removed so it could bend to wrap around the dowel. I didnt run the spars all the way to the wingtip as I wouldnt have had enoujg space infront of it to bend up the front. I measued halfway between the spar and my fold line and removed the paper from that mark all the way to the other side of the top half. my plan was to have a tapered wing that had the aerofoil change along its length. I figured this might help the plane. who knows. this is still kind of an experiment
20130511_113808.jpg 20130511_113824.jpg

The dowel rod in each wing is removable, my plan is to have a 1m long removable spar through both wings and the fuselage, that should remove any weak points, as my original plan was to have each wing have its own dowel spar and join them in the middle.
I put a hold in each side of the fuselage and popped the wings on as a test.
20130511_121702.jpg

my next step is to add a small piece of gift card the back of the wing and cut a small corrosponding slot in the fuselage, this way it'll stop the wings from twisting at the gift card slots into the slot. I also am going to make some struts to go from the wing to the fuselage, i've worked out a simple locking mecanism for them. should be simple, easy and not too heavy. fingers crossed it worked.
 
#13
Not much done this weekend. I finished the wings. I cut in the ailerons and the flaps, and added the servos. I built some wingstruts out of bbq skewers, tape and gift cards. they attach to the fuselage with my simple latch design, this does a good job of holding the wing from flying off, and to adding some extra strength to the plane. i may need some extra strength to help hold the wings securely attached, but we'll see how that goes.
20130520_162948.jpg

Hopefully by next weekend my motors and final elecronics will arrive. so fingers crossed i should be able to get this finished next weekend :)
 
Last edited:
#14
Well the motors arrived, along with the rest of the electronics. I've installed everything, and the CG is pretty much right on the spar, I'm hoping this is correct, I'll get around to doing some glide testing soon before i take her up for her first flight. the two 6x3 counter rotating props have about 1.5cm clearance between them. I have some 6x4's but they are not counter rotating, i'll give it a go on the 6x3s first, might upgrade to the 6x4s, we'll see. All up the weight is 774 grams, I'm thinking about building some landing gear for this too, not sure if i'll do my retracts design just yet, i just want to get this into the air, and it'd be tough to hand launch as you cant really grab the fuselage in one hand, like a standard tubular type fusealge.

I present to you, my Burnelli UB-14
20130526_110054.jpg 20130526_110108.jpg 20130526_110141.jpg 20130526_110203.jpg 20130526_110328.jpg
 
#16
wow, ok, so lots of life and bad weather got in the way of me giving this a maiden. i actually had 3 planes to maiden on the same day, here is the video of them all


Skip to 8:06 to see my Burnelli UB-14

I would really like your options on it. I need help with it, you'll see why pretty clearly in the video
 

earthsciteach

Moderator
Moderator
#17
It has CG issues. You have a plane with a very blunt nose and a horizontal stabilizer. The down force from the horz stab amplifies the rearward cg. You need more weight as far forward as you can get it with the configuration. Or, consider making a "flying tail" - a horiz stab that generates lift.
 
#18
A nice build but your Burnelli would certainly seem to have a very rearward CofG so the question is - where is it currently?

With a broad chord wing, smallish tail plane and a short tail moment it may be very sensitive to CofG position.
Do keep us posted.
 
#19
earthscitech, a flying tail? i've never heard of that before, but looking into it, i can see the advantages, although i wonder how it'd go if i got into a dive, it would be making it almost impossible to pull out of i'd imagine.

Guorneng, the CG is sitting right on the wooden dowel spar that i have running through the wings. you might be able to see it as i am showing off the plane. my plan is to try to just add weight to the front and keep chucking it until it balances. as not really sure that balancing it on its wings (like i did before) would give me an accurite flying position.
 
#20
eagle4
That dowel would appear to be at about 1/3 of the wing chord which if that is where it balances would be to far back, particularly with the wing section you are using.

With a complex wing/fuselage shape such as the Burnelli the correct CofG is go to be a bit of a guess anyway.
I would set it at no further back than 1/4 of the outer wing panel chord, at least to start with.
Much better to be a bit forward than a bit far back.