Zulu ET

[Tony Hudson]

Hi>>

I have finished the build and have had 2 unsuccessful flights.>>

In the first flight it barely left the ground and keeled over to the left , wing hitting the ground and snapping the wing bolt and breaking a horn on the wing. Analysis by my fellow club members that it was under powered. Back at the hanger a Watt meter revealed that I was getting barely 190Watts. It was suggested that I fitted a larger prop. I purchased a 11x4.7 prop and now got 243Watts on the Watt meter.>>

Took it to the field for a second flight. This time it managed to leave the ground, but again veered to the left and headed for the ground, this time demolishing the cockpit and snapping off both F3 and F4.>>

This time it was thought that it was tail heavy, even though I had put several oz of lead in the nose. I must add that my build somehow ended up overweight at 48oz.>>

When I returned to the hanger and started to rebuild I noticed something that I had not checked before. On the spec at the end of the article the fuselage length was stated as 38 inches, but the plan it measures 36.5 inches ( and so does my model). >>

What is the right dimension as the 1.5 inch difference would make a great deal of difference to the stability of the model?>>

Since writing this (I had trouble posting it), I have found what was causing the crashes. The right wing was 6mm higher than the left wing. However I would like to clear up the anomily regarding the fuselage length.

 

Tony Hudson

[Lindsay Todd]

Hi Tony, I had not noticed the length discrepancy, the model has quite a short tail moment anyhow so it your not used to this It can be a little sensitive if the CG is not correct. The cg can be moved forward by up to 10mm and this might be worth doing.

Also worth a cheque is that you have no left thrust, a degree or so of right thrust, when viewed from above a nd behind the model has proved useful by some people.

hope that helps the plan version in the build blog on here flew fine so all should be well in the end.

 

[Kit Davidson]

Hi Tony,
The leftward flight took me by surprise too. As soon as I had placed a washer under the left (from aft) arm of the cruciform mount and another under the upper arm to get some downward thrust, my Zulu flew perfectly.

[Tony Hudson]

Thanks Guys for the replies

 

Lindsey, You did not clarify which was the correct length? I assume that the plan is right!

 

Kit, Had noticed that it was not in line so have packed out as you did.

 

Working on rectifying the wing, so will test fly after Southern Show.

 

Tony Hudson

[Lindsay Todd]

Sorry Tony, the original was longer than the published plan, but the one built from the plan on the blog here flew just as well, I could not define any difference from memory it was a while ago now but I don't see any reason for concern providing the cg is correct.

[Dan Sadler]

Hi again. I fixed my last problem by making the former slightly wider and have made good progress since then.

I'm at the point where I need to bend the two pieces of balsa that go from the outside front edge to the middle. I have soaked the balsa for about an hour and then stuck the base in place on the outside of the fuselage then tried to bend the wood over a few minutes later once it has stuck. I have done it slowly and carefully but both times I have tried it cracks on the outside edge and I'm left trying to cut the newly stuck wood off again.

Any tips please before I waste any more wood and effort?

Thanks

Dan

[Alan Cantwell]

use ammonia to bend the wood, the ammonia soaks in, and you could tie knots with the stuff, when the ammonia evaporates, thr wood stays the shape you put it in,

[Kit Davidson]

Hi Dan,
In my other life I make double bow Windsor chairs www.welshwindsors.com I use steam for this. But beware, think of wood being a bundle of laminated tubes full of residual moisture. The steam is used to heat this moisture and make the polymers more pliable. If my wood is kiln dried, steam bending always fails. The steam does not make the wood wetter, it is just the medium to surround the wood with sufficient heat. Balsa is very dry. Try putting the balsa pieces into hot water. I also use soaking like this for smaller chair pieces.
You can also try scoring the balsa on the outside surface with a scalpel. The scores should go with the grain (I have assumed that you are running the grain from fore to aft on your model) if you have not done that, it could be the reason your balsa is cracking. But back to the scoring; don't cut right through but half way. Your balsa will now bend. The scores may be filled with surface filler because they will gape insignificantly as the wood is bent around the frames. You are going to cover the fuselage anyway.
I hope this helps.

[Viking42]

Hi,

This is just to tell you that I also fell for the ZULU-ET, but decided to use Depron as much as possible. I had to use wood for the wingfix and and main frames to hold wing and landing gear, so there is practically little weight gain. I had to strengthen the wing with a carbonfibre tube, I also divided the aileron to have some flaps and added winglets for groung loop protection a.o. Unluckily I got ill when this odd kite was ready for flight, so this yet has to come. I include a picture.

 

Regards

Peter G

[jeff w]

hi everyone. i'm just getting to the end of the build of this plane (first one ever) and now waiting for suitable weather to maiden her. i've enjoyed the build and would like to have a go at building the low wing sportier version that was a free plan in feb 2009. has anyone got a back issue they would like to sell? i am relatively new to model flying but i think it far to say i'm hooked!

[William Dargie]

Hi,

I'm very interested in building the Zulu ET !

But I had a question : do you think it's possible to buy 6x6 balsa (or pine) sticks, rather than have to buy more 6mm balsa sheets and a balsa stripper ? If so, approximately how many sticks do you think I'd have to buy ?

I'm asking this because I'm buying the materials with my pocket money and I don't want to spend too much lol !

 

Thanks !

 

William

 

 

[Lindsay Todd]

Hi William, to be honest if you are looking at building the balsa stripper would be an excellent investment, of course you can always use a steel ruler and sharp scalpel but I would go for the stripper. Pine is suitable for the wing spars for which you will need 4off for the main spars. The fuselage uses quite a bi of 6mm square and at a quess 10 to 12 lengths are probably required.

Linds

 

[William Dargie]

Thanks Lindsay ! I've gone for the stripper and ordered all the materials. I'll post some photos next week of my progress !
William

[William Dargie]

I was looking on the internet for the motor of the Zulu ET and I had a question : what is the motor's "kv" ??

[Andrew Bourne]

The kv is the revs per volt. EG for a 3 cell (3S) lipo with approx o/c charged voltage of 11 volts and a motor rated at say 1600 kv the max revs would be 17,600 (11x1600) RPM.

Real test is with selected prop, matched ESC and a wattmeter.

[Mike Robey]

Hi All,

I started building one of these two years ago, got to the wings and got distracted. I am now back into finishing it but I am concerned about how heavy mine is turning out to be.

Lindsay's is around 1kg according to the RCM&E review. Mine with motor, battery, servos but WITHOUT covering, esc, prop, landing gear and other bits and pieces (e.g. velcro) is 995grams. I am thinking that will put it way overweight when I am done.

I have scratch built a lot of foamies but this is only my second balsa scratch build. Point being should I stop now? I don't want to spend the money and time finishing it if it is going to end up 50% overweight.

The big variable in predicting the final weight is the covering. I can estimate the weight of the other bits and pieces but I have no clue how much the covering will weigh. The covering I have is from hobbyking.

Any advice would be most appreciated.

[ian ludwell]

Hello Michael,

I shouldn't worry too much about being overweight.

The actual AUP weight from the October mag is 2lb 6ozs.

The wings are fairyl big for this model and will have plenty of lift.

If i rember when i built mine,it also was overweight and surprised me how quick the plane got off the floor.

I recently built the Pix-e mjor,AUP weight from the mag 13.5 oz,mine 17oz,no problem with the extra weight.

Lets have som pics.

enjoy the build............Ian

[Mike Robey]

Thanks Ian,

That sure makes me feel better. Can you remember what your all up weight was?

Anyway, as requested, here is what I have completed so far. I'll post more photos when I get her all finished. I have really enjoyed the build so far.

[Mike Robey]

Slowly but surely getting closer.

[Dan Sadler]

Hi,

After a break from building I have returned to start again and remembered why I stopped in the first place.... Wing Incidence.

I haven't got a clue how to mount the wing properly. I have managed to sit it in place and get it to measure very close to the same to each wing tip from the centre of the fuselage, but how do I know what the wing incidence should be, and then how do I set it?

Thanks in advance.

Dan

[Mike Robey]

Hi Dan,

My memory is that Lindsay's advice was to make sure that the wing seats on the top of the fuselage match their position on the plans. He said if you did that the the wing is at the correct angle.

If you lay the fuselage on the plans you should be able to check that. If it doesn't line up then you can either sand it or pack it depending which way it is out.

Hope that helps you get sorted.

[Dan Sadler]

Thanks for the quick response Michael. I will give that a go... From what I could see one side of the wing was a little higher than the other from a table beneath it as well so I am guessing somethig is a little off somewhere.

A member of my local club has lent me a robart incidence meter but I'm not really sure how to use it and he isn't the best at explaining it unfortunately.

[Charlie Raley]

Hi,

Unfortunately I am unable to upload photos, however I am in the later stages of the build with only the fuselage left to cover. The Zulu has been an ongoing project, my first RC plane build.

I have installed a mystery 1400KV brushless motor with a 30A ESC that has a built in BEC, when testing the electronics recently the motor would seem fine and perform well but after so long in would speed up to full throttle for no reason I put it down to the wrong ESC setting however it has happened 3 times now once whilst taxiing around the garden.

I am very excited about getting it into the air however this problem is proving a nightmare as testing is dangerous.

Can anyone help me out on why this may be happening and also give a bit of advice as what electronics would be the best for such a plane?

Thank you

Charlie

[Mike Robey]

Hi Charlie,

If its randomly going to full throttle then I think its either the ESC, a loose connection or somekind of receiver issue. I'd check your connections first and if nothing shows up I'd try swapping out the ESC. Probably a good idea to test it with the prop off so you don't end up with a runaway plane.

I am no expert by any means so the above is just what my best guess. I hope it helps.

[Radge]

BHi Charlie, Good advice there from Mike. When you connect the battery are you keeping the throttle stick AND it's trim all the way down? If rudder is on the left stick, check also when turning in your garden that the throttle and it's trim aren't being moved also. Basic stuff I know but we can all do it. (Welcoming Smiley)

Bless