Building the Kelula

[Hai-Lee]

This thread is to document my attempt to build a 1200 mm wingspan Alula clone in standard thickness FB. Plans will be included eventually for those that wish to attempt to build one. This is also a lightweight bird with a leaning to slope soaring. Later in the documentation a version with a tail boom and standard control surfaces will be built, (as per special local order).

More later!

Have fun!

 

[Grifflyer]

This thread is to document my attempt to build a 1200 mm wingspan Alula clone in standard thickness FB. Plans will be included eventually for those that wish to attempt to build one. This is also a lightweight bird with a leaning to slope soaring. Later in the documentation a version with a tail boom and standard control surfaces will be built, (as per special local order).

More later!

Have fun!

What modifications would it need to make it a DLG? Would it just need a beefier spar?

 

[Hai-Lee]

What modifications would it need to make it a DLG? Would it just need a beefier spar?

I was going to be using a solid 5 mm thick Balsa spar in each wing with dual bent paddle pop stick dihedral braces to join the spar. A double thickness FB laminated spar should be strong enough to handle some extreme flying and discus launches though I would make sure that the spar cannot de-laminate over time!

From the crash experiences with the smaller 3 mm FB version which included a few vertical nose impacts that really destroyed the nose.fuselage(?), The wing is quite strong. We actually drove the Rx through the wing LE and the nose cut through the wing LE and yet the spar wasn't cracked, detached, or even dented. Just dragged the crushed FB forward, glued, and fitted a new nose.

The reason for the number of crash events was that the owner is a newbie who is yet to even perform a solo on her other planes. It was her bird and so she got involved in the testing. Using a bungee launcher, (at less than full strength), and with her lack of reaction speed she managed to get over 20 metres in height on launch and then sadly a vertical dive into hard dry clay type soil. Note to self, I should never say to a newbie "give it a little up on launch to gain some height".

Have fun!

 

[Hai-Lee]

I have drawn out the Wing panels and well seriously this thing is HUGE. The elevon area alone is larger than some planes I have flown.

For structural reasons I may even reduce the elevon span which if it works will allow the simple inclusion of flaps when I build the version with a full fuselage and tail unit. Looking at structural elements at this time as well as whether I should go with either a single pieces or a two piece wing setup.

Later!

Have fun!

 

[PsyBorg]

If its as big as I am picturing may I suggest 3 sections. Portability may be an issue for some with tiny cars or like me who have to walk or some that take buses everywhere. That way an aluminum arrow shaft can be used as a spar AND as a mating point for better alignment.

 

[Hai-Lee]

If its as big as I am picturing may I suggest 3 sections. Portability may be an issue for some with tiny cars or like me who have to walk or some that take buses everywhere. That way an aluminum arrow shaft can be used as a spar AND as a mating point for better alignment.

Something to consider for sure, its either that or a wing that joins together firmly before the 2 piece fuselage is fitted.
The 2 piece fuselage is being considered as it allows me to remove the glider nose and fit a powered nose for experiments, or even the removal of the tail.fin section and fit a pusher fuselage fuselage rear.

This one has a few extra options. The person commissioning the build is already thinking of its use as a survey drone in the future!

The things I get involved in.

Love the input!

Have fun!

 

[FoamyDM]

with these short coupled planks. I'm finding them VERY challenging to get the Balance point correct.

 

[Hai-Lee]

with these short coupled planks. I'm finding them VERY challenging to get the Balance point correct.

I start with a CG point at around 10 to 15 % of mean cord. Ensure that I have plenty of elevon movement and start with hand launches. Later I move to bungee launches but the launch speed is increased only after success at lower speeds. Note with the short coupled nature of the elevon control you do need to start with plenty of expo and a gentle touch on the sticks! I am somewhat lucky as I started into planks with absolutely no knowledge and so I had to learn quickly and whilst challenging they can really perform. Having no tail means that they can really turn "On a Dime". If setup with differential the smaller span birds can do axial rolls at a rate that still astonishes me!

The reflex I start with is marginally above zero as it is initially better to have the craft want to dive SLIGHTLY. I hold the up elevon manually until I get a glide that I am happy with and then I adjust the reflex to be the same as I am holding for a good glide. Once glides are good and stable you can do your stall glide tests to check the balance point.

After the BEST CG/balance point is determined you can revisit the reflex settings and this should be the final adjustment.

On this bird the starting balance point is around 32 to 35 mm from the wing LE at the wing joint.

If you want a simple plank design, (accent upon simple build and good handling), I did a thread of a goblin like plank a while ago and I could search it out for you, (mine is still flying!). But then for a bit of extra complexity you could just build the FT Goblin, (a nice bird but a little heavy and complicated).

Have fun!