Zulu ET

[Joe Hull]

Thanks for the info Lindsay.

I would appreciate your further advice on wing building.

 

I am just starting on wing construction and wondered if I could use 2.7mm Lite Ply instead of balsa. Sorry to keep harking back to my newly acquired Seagull but it is a tough plane made mostly of ply. I lost control of it when training and it went out of range and ended up 20 foot up in high branches of an oak tree. We managed to recover it by using long jointed GRP poles.

 

It suffered some damage to the leading balsa edge but it was repairable and is still flying dispite me also hitting a low flying hedge!! trying to land it.

 

Compared to the Seagull the ribs on Zulu look very flimsy but I realise that ply will compromise the weight and perhaps the flying characteristics. I realise that once the composite wing is covered its structural integrity is much improved but as a trainee it is damage limitation when crashing I am concerned about!!

 

Please see my 1st attempt at using Lite Ply rib. but before I make another 15, I would value your opinion on whether you think I should use them. I have weighed  the balsa design which weighs about 0.6 grams and my ply version which weighs 3.5 grams so a significant weight gain. 16 ply formers would weigh 56 g and 16 balsa ones would weigh about 9.6g.

 

Is this weight gain enough to compromise the flying characteristics do you think?

 

Cheers Joe

 

 

Edited By Joe Hull on 15/11/2010 18:43:24

[Lindsay Todd]

Joe, this hobby is about experimenting. Lite ply will increase the weight a bit but should not unduly compromise the flying. Just make sure you keep to the cg position or even a little (5-10mm) forward if you are still learning.

 

Linds

 

 

[Joe Hull]

Ok thanks, I think I will try this.

 

It will be interesting to weigh my finished plane to see how it compares to yours.

 

By the way, I was reading your original Zulu ET article in RCME and it says wing area is 432 sq feet, this must be a misprint

 

I guess it should read 432 sq inches

 

regards

 

Joe

 

Edited By Joe Hull on 15/11/2010 21:21:36

[ian ludwell]

Hell every body,making progress,good to have these pics to help.

[ian ludwell]

Hello all,some very interesting builds i have to say,as i said earlier to Jim quite a challenge for the grey cells,but good fun,as you can see from my pics i am using my Futaba S3003 servo's,not sure whether to try the Aileron route or just go for Rudder/Elevator,thinking maybe go for R/E now and build another wing for Aileron later,any thoughts on that?

Also another build for the winter months is the Keil Kraft Scorpion pictures are of a friends model i am copying, this is for those calm summer days,have to go now as my cottage pie which i have just eaten has made me rather full.

 

 

 

[Lindsay Todd]

Ian, the model has never been tested as rudder only, your on your own with that one. If you go that way i would move the cg a little further forward to increase stability say 5 to 10mm.

[ian ludwell]

Thanks for the advice Lindsay,the only reason i suggested the R/E route was in your article you mentioned it maybe would lend itselfe to that choice and also i am back into r/c gliders after a 35 yr gap and Ailerons are new to me as i fly R/E with my gliders only,but maybe is now the time to start with something new,just a word of thanks for those pics of yours that have helped in cases that seem to stump me,as they say a picture paints a thousand words..many thanks again..ian

[Kit Davidson]

My Zulu is completed! All I have to do now is wait for the rain to stop. This was my first balsa aircraft since Messrs Vernon and Keil Kraft half-built them for me in the 1950s. I have been really absorbed in this hobby since I started in August this year. I have discovered slope-soaring, powered flight and now building from scratch! Shortly after achieving my A certificate, my club examiner was admiring a Piper Cub I had bought on ebay. "Did you make that? he asked. He was disappointed with my reply and he walked off muttering to himself "Why doesn't anybody make anymore?" He seemed oblivious to the is ARTF Extra he was carrying. I hope he is at the club when I take my Zulu down for its test flight!

 

Thank you Lindsay Todd!

 

Minnie the MInx? It refers to my reading material when I was last involved in aero-modelling. 

Edited By Kit Davidson on 17/11/2010 13:23:52

Edited By Kit Davidson on 17/11/2010 13:25:01

[Biggles' Elder Brother - Moderator]

Very exciting Kit - don't forget to tell us how she flies once you manage to get out there without the rain. Mind you looking out of the window here that doesn't look to likely in the near future if you have weather like ours here in the North West!

 

BEB

[ian ludwell]

Looking at Kit's finished model and i must say it looks very striking,i like the transfers on the wing and fuz,where did you get those transfers,i was contemplating a similar colour,i have a quantity of Giant Cod solid  Orange and transparent Red covering left which to some one like me who is colour blind should look ok,i am in West Yorkshire it's not raining but it is cold and windy,good luck with your flying,look forward to hear how it all goes.

[Kit Davidson]

Watcha Ian!

 

I did a Google search for the cartoon I wanted. I used the crop tool in Google's free Picasa software. I inserted, copied and pasted in Microsoft Word. I printed the resulting images at varying sizes on special decal paper available in the model shop or by mail order. I did the final editing with scissors.

 

Inkjet printing needs waterproofing or fuel proofing. I use Artists Fixative but clear matt varnish or similar would do the same. 

 

Kit 

[Jimbo565]

Nice job Kit   well done

 

Jim 

[Joe Hull]

Well done Kit looks very good, be sure to tell us of your flying experience with her.

 

I too have some limited experience flying and building model planes as a boy in the 1950's and have just joined an RC club to learn to fly.

 

I am just about to start building the wing. Can you or Lindsay confirm the number of ribs in the wing. I have studied the plan and the blog and I think my understanding is correct but I would like someone to confirm it please.

 

The plan says 16 wing ribs but mentions two central ribs, initially I assume the 16 ribs included the central ones but now I think the central ones are in addition.

 

I assume there are 18 ribs in total including the centre ribs these are shortened and glued together when you join each wing half.

 

When you make the 1st half of the wing Lindsay mentions using  the 9th rib,  I assume this is the central shortend rib.

 

Is my understanding  correct?

happy flying Joe

[Kit Davidson]

Joe,

I have delayed replying in case Lindsay replied first and because I am having a job remembering. (I am 65, played too much rugby without a helmet and can't even remember what I did yesterday) However I have looked again at the plan and do remember that it was a bit confusing. It says on the plan to cut 16 ribs but you are right there are 18. Also there is another leading edge rib named 1A that one is invited to cut but is not otherwise marked on the plan with its part No. The 17th and 18th ribs are the centre ribs - one to each half wing. Note that these are made from 3mm material. I used balsa.  Its coming back to me! I made the half wings up with 8 x 1.5mm balsa ribs and one x 3mm balsa rib. I then cut the centre 3mm rib to fit the spar. I fitted rib 1A (3mm balsa) afterwards.

 

The 6mm "rib" that you can see confusingly on the plan lying immediately outboard and at an angle to the centre ribs is the wing support and part of the fuselage. 

 

I didn't worry about an angle to accommodate the dihedral on the centre rib. The spar takes care of the dihedral and the difference between 90 degrees on a properly set rib and the small angle required to offset the centrer rib from normal is less than building tolerance on all the other ribs. Epoxy glue filled any accidental gap.

 

I cut my ribs in 2 batches of 8 and one batch of 2 (centre ribs) with a scroll saw. 

 

I hope this helps.

 

Kit 

  

[Joe Hull]

Thanks Kit, this confirms my thoughts.

 

I am going to use 3mm Lite Ply ribs throughout. This will add some weight but I hope this will not significantly alter flight characteristics.

 

I also cut 16 ribs in one go from info seen in RCME mag.

 

I made two templates and used 2 bolts to clamp the other 14 rough size rectangular ply  together, then shaped them as a block, worked quite well, no differences in measurements - they are all identical.

 

Crashed my Seagull Innovator badly today, I took off but did not get high enough before turning and lost control -- bad mistaka to maka!!

 

This RC stuff is more difficult than it looks!!

 

It is a tough plane and I hope I can restore it OK with good old super glue

 

Best of luck with your Zulu ET it looks like you have done a fantastic job there.

 

Joe

[Kit Davidson]

Joe - It wouldn't be fun if it was easy! I am taking pride in coming home from the slope with fewer models in binbags. Take a look at this: http://www.youtube.com/watch?v=MvNd6vmSCcc

 

Smart!

 

Kit 

[Kit Davidson]

Well, I have completed my test flight this morning and it was successful - ish! Even with that qualification I was pleased. A couple of taxi tests and it was time to go for it. I heaved back on the elevator and up she went. Minnie the Minx immediately banked to port and flew over the clubhouse and the member's car park. I was the first there this morning - so no bother. I was feverishly applying starboard aileron and correcting the trim with my other hand. The Minx flew for about 5 minutes, always wanting to bank to port and turning to starboard with marked reluctance. She flew comfortably on half throttle. But I had run out of starboard trim on my transmitter.

 

Time to land. With starboard stick applied, I throttled back and otherwise left the aircraft alone. It came in for a perfect 3 pointer on the grass but stumbled because the grass was a tad long and the wheels were smallish.

 

I should say that I was always cautious about my ailerons, which I had made on a belt sander.. It was difficult holding the light thin balsa on the big belt without taking the tips of my fingers off. I knew that their profiles were not perfect and rigging the aircraft was difficult. Time for another flight. I lengthened the push/pull rod on the starboard aileron and shortened the same on the port. When I next took off, I crashed. The Minx banked to port again and came down on prop and port wing from about 10 feet. The motor was ripped from its mounting but otherwise there was no other damage. It bounced well!

 

I have less than half an hours work for the repair and perhaps another couple making and fitting new ailerons. I went straight from the airfield 35 miles to the nearest model shop to buy stock section balsa. It was only my impatience that stopped me from doing that properly during the build.

 

It flies! But please take my word for it. Unfortunately I enlisted my wife to video the event. With a video camera, she's about as much use as a one-legged man at a bum-kicking contest. Nevertheless for what its worth you can see it here: http://www.youtube.com/watch?v=3EMcx87gNvg&feature=youtube_gdata

 

 

 

 

Edited By Biggles' Elder Brother - Moderator on 19/11/2010 23:00:44

[Lindsay Todd]

Kit, I notice you have decide not to fit the finstrake, not a problem but combined with larger power than original? you may think of adding a little right thrust. My online blog build has a 320 watt motor throwing an apc 11x4 and need a little rudder right trim, now removed by adding a couple of washers behind the mount.

I am sure you have but check for warps in the wing, the short couple keeps her agile so worth a check. I fly most of my model quite sensitive with expo dialled in.

 

the remaining photos of the build , some video tocome asap

Nothing clever with the radio gear, reciever sitting between servos

Glazing from acetate and fixing with small screws

commercial tail wheel fixed to rudder with rubber band

Motor installed is emax 1200 320w throwing an 11x4apc

 

She has now had three flights, I have added a little right thrust, a result of larger motor and bigger prop than prototype and will post some video asap.

 

Lindsay
 

[Darrell Bullard]

Kit

I got a good chuckel from yor wifes video, it was like the cartoon where elmer fudd is looking for bugs bunny,...which way did he go????

 

 

[Kit Davidson]

Lindsay,

 

Good advice! "Modified by Kit Davidson" was not such a good idea after all. The finstrake will help directional stability. It is probably more than the cosmetic touch I thought. I will restore it. Similarly, one of my friends who turned up and saw my Zulu fly, was surprised that there was no bias on the thrust. On full power Minnie seemed to climb at an impressive attitude and I needed to hold it down with by throttling back if I remember. I am now going to try a little right and downward thrust bias as well as new ailerons and bigger wheels.

 

I have no wing warps and the short couple commented on by  Jet and one of my club members did not present any problems for even me, flying with Welsh green P plates.

 

I am still reliving my short test flight with pleasure. Dare I say it? The wing incidence from the plan must be spot on!

 

Kit 

Edited By Kit Davidson on 20/11/2010 12:54:07

[Kit Davidson]

I have completed my second test flight. It was less successful than the first. Most of the failure was my own fault. I relate what went wrong here for the benefit of any other new builders approaching the same stage.

 

It was fine and sunny this morning with a wind of about 6mph. Conditions were perfect. Minnie the Zulu had new larger wheels, new ailerons and the propeller was biased to the right with 2 washers (1.2mm) under the port cruciform engine mount. I had also biased the propeller downwards by placing one washer underneath the upper cruciform arm. (0.6mm). (My cruciform mount is fitted in the crucifix orientation, not the X ) One of my chums had remarked that the 10 x 5 propeller was largely masked by the large frontal section of the aircraft. I listened but for reasons not entirely known to myself I fitted an 11 x 7 propeller. I still had not fitted a finstrake.

 

Time for take-off. Minnie shot off and unstuck at less than half throttle, There was no veer to port this time and I was able to control the bank. But I could only liken it to a Sea Harrier leaving the ramp of HMS INVINCIBLE. It was as much supported by thrust as lift from the wing. I could have done some prop-hanging if only I knew how! Relatively small changes in throttle position produced alarming aircraft attitude shifts. I was nervous. I decided that discretion was the better part of something I can't remember and decided to put it down where it was, over a freshly harrowed field. In glide without any thrust effect the Zulu behaved itself. But it came to a sudden stop on landing in soft earth.

 

I picked up the undamaged aircraft and took it back to change  to a 10 x 5 propeller. When I was connecting up the battery again, I saw that the heavy 3s Lipo had torn the battery tray away from its mountings. The glue joints had not failed but the balsa had sheared along its grain. My battery tray was not hard up behind Frame One as per the plan but had space to move 5mm forward in the deceleration on landing. 

 

I now think my first test flight problems were caused by uncorrected thrust and not an aileron problem. After repairing the battery tray and its mountings, I plan to fit a sensible propeller and remove one of the right motor bias washers. The new 70mm wheels were much better on take-off from the rough surface than the original 50mm wheels. They look right too.

 

I am learning every day! 

 

[Joe Hull]

Thanks for the feed back on Zulu ET

 

Glad to hear your flying tests have been reasonably successful..

 

I am working on the wing at the moment.

 

Joe

[ian ludwell]

Moving along slowly,some filling in to do,small parts to fit,then on to the wings,as Lindsay suggested about the Ailerons i think i will put them in place instead of R/E as i was origionally thinking.

Kit,sounds like you had a great time with your flying day,you never know whats going to happen until you push that throttle and of she goes.

I have had the same problem trying to video members flying models,if you lose sight for 1 second it's hell trying to re-locate it,and you forget that the sound is picking up all your mutterings.

Well tomorrow and Sunday is the Harrogate modellers fair,so will go and see what is on offer,look forward to some more build/fly pics.

 

 

[ian ludwell]

Hello to one and all,this weather is playing havoc with the flying good job i enjoy building,now started the wings,steady away,trouble is it's colder in the garage than outside,maybe i should take my bench out in the garden,problem is clearing all the snow off the plan.

Just a word to maybe those who havent got one(Balsa Stripper).

Best thing i ever bought,an Aluminium slide into which fits a plastic handle with spacers and blade,fit the spacers to suit the size of strip you require,fit the blade and cover,3 knurled plastic nuts to retain the blade,drop this into the Ali slide,place your sheet balsa behind the protruding blade,draw blade towards you,blade cuts through balsa,job done,saved me so much time and money

Handle can be seen to left of tailplane.

 

.

[Joe Hull]

Yes I bought one a few months ago in our nearest model shop - they are great, I have cut a lot of 6mm sq for Zulu ET with it. made by SLEC I think.

 

I am on the wings and have some more work on the fuselage as well.

 

Joe