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Just another Ballerina

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Peter Miller21/01/2016 18:19:38
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I don't mind if the scallops are not cut, that is purely cosmetic.

Chris Barlow24/01/2016 03:01:37
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Posted by john stones 1 on 21/01/2016 18:04:26:

He's probably noticed you've not scalloped those infills yet, but he's too polite to say owt, as am I teeth 2

John

Thanks John! Just been grassed up by the teachers pet! crying wink

Done a bit more over the last couple of days but the build is now slowing down as it's getting to the fiddly, finickey bits!

First up is the issued of the gap at the rear of the tail. With the tailplane repositioned up to F10 there will be a bit "missing"

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Just needs a small triangle of 1/4 balsa to fill it in, leaving enough room for the elevator joiner.

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The fillets for the tail were laminated from a piece of 1/2" and 3/8" balsa, marked off F10 and planed/sanded to shape.

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To get the correct spacing for the tail plane and fin a piece of 1/4 balsa was cut as a temporary spacer.

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The ailerons have also been hinged...

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And aileron servos installed.

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The aileron servos are mounted onto 3/8 x 1/4 spruce posts glued to 1/16 ply. 1/4 sq spruce is fitted between the ribs and the ply is then drilled and screwed to the spruce bearers.

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Some 1/16th strips will be needed to close off the servo bays to enable the covering to be ironed around the opening for the ply.

With the leading edge fitted and planed to shape the whole wing was rough sanded to level all the joints. It will need finer sanding before covering!

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Chris Barlow24/01/2016 03:51:06
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The next bits are a bit more critical and will require a degree of measuring and accuracy.

The hole for the front wing dowel is drilled slightly higher than the slot cut in the part ribs on the plan. This is to increase the amount of wood below the hole in F2. The hole must be drilled as level as possible and 90 degrees to the leading edge. A 1/4" dowel is cut and glued in the 6.5mm hole with 5 minute epoxy. In the next photo the pen line indicated the end of the dowel and how far into the wing it is drilled. This is to prevent the dowel from pulling out of the top of the wing during high positive G maneuveres.

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Two wing bolts are screwed into the wing bolt plate from the wrong side which for this model is very easy to do and show!

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With F2 drilled accurately to accept the wing dowel the wing is fitted to the fuselage and pinned at the trailing edge. Before marking the bolt positions it's very important to ensure the wing is square to the fuselage first. This is done by attaching a piece of string to a centre point at the tail and marking off one wing tip.

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The string is suspended over a pin in the tip and marked with pen

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without removing from the centre point at the tail the string is then moved across to the other wing tip and suspended over another pin. If the wing is square to the fuselage the pen mark will line up with the tip. If not a second pen mark is made on the string and the desired position is exactly half way between the two marks.

Somehow, probably by fluke chance, my wing lines up first time. crook

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String tension is kept consistent by allowing the string spool to hang, tensioning the string the same on both sides with it's own weight.

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With the wing pinned in the correct position the reversed wing bolts can be screwed in through the stringers and with a little pressure on the wing will mark the balsa, indicating where to drill.

When screwed in backwards the wing bolts were pretty much perpendicular to the fuselage so the wing will be drilled at 90 degrees to the underside. This will ensure the bolts aren't bent when they pass through the wing and into the wing bolt plate.

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A 1/16th ply plate is then glued over the holes, which are re drilled through the plate. This is to prevent the wing bolts from pulling through the balsa in the wing. The wing can now be bolted to the fuselage.

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The wing seats are not too bad.

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And the cut down wing bolts just protrude through the captive nuts

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Another step closer! laugh

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Chris Barlow24/01/2016 04:14:16
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1858 forum posts
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Now the wing has been accurately fitted in position the tail plane can be fitted. Some people prefer to cover the tail surfaces before fitting but for solid sheet surfaces I have no problem covering them fitted to the fuselage.

I always do a dry run first before applying any glue. This ensures that I haven't forgotten anything, everything is ready for glueing and I can spot any problems in advance.

Happy that everything was going to go smoothly I mixed up some 20 minute epoxy and applied some to the tailplane seat. The tail plane was then fitted and pinned in place. The edges of the fin were then glued and that was also positioned and pinned, Finally the two fillets either side were glued up and fitted in both corners where the fin and tailplane meet. Because the fillets have been cut square I don't have to worry about the fin being 90 degrees to the tail plane.

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It's now clear where the gap would be that I filled with a small 1/4 thick triangle.

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During the trial run I found it was going to be possible to pass the elevator joiner through the gap behind the tailplane, otherwise I would have smeared it with some petroleum jelly (vasaline) and left it loose in the gap ready for fitting the elevators.

Working quickly, but not rushing, the tail plane was checked against the main wing to ensure they were level with each other and checked for square to the fuselage as the wing before. I used the remote glow plug at the front and marked the string at the outside trailing edge of the tailplane, then did the same for the other side, just like I did with the wing. This time it was 5mm difference so I marked the second line and then a final line between the two and adjusted the tail plane.

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I then checked that the fin was in line with the fuselage by sighting down it to the nose. It wasn't! With the fillet blocks in the correct position and flush with the stringers and F10 the fin was pointing of appoximately 10mm to the right of the nose! The fillet blocks and front of the fin were unpinned and the fin repositioned untill it lined up with the remote glow at the front. The fin and fillets were then re pinned.  Note that the fin cannot be adjusted at the rear as the rudder has to be hinged to the end of the fuselage, which must be in line with the fin!

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Unfortunately this now means that the fillets are not flush with F10 and will need re sanding to fit, but getting the fin in line with the fuselage is much more important!

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It looks like the top centre stringer is not exactly on the center line which has tricked me when marking the fillets but the tail is now straight, square and true and left for the epoxy to harden over night. laugh

Edited By Chris Barlow on 24/01/2016 04:18:06

McG 696924/01/2016 07:51:15
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2716 forum posts
1019 photos

Great build, Chris,

... and very educational for us newbies. smiley

One question, please: why not aligning your wing & tail fin before carving and sanding the two infill blocks?

Thanks also for taking the energy & time to post all those pictures.

Cheers

Chris

BRU - BE / Blog Control (on a early Sunday morning... surprise)

 

Edited By McG 6969 on 24/01/2016 07:52:59

Peter Miller24/01/2016 08:37:13
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10323 forum posts
1231 photos
10 articles

This is a master class in how to do it. All Ballerina builders should read this one.

Just one of my own ideas. I have two short, headless wing blts which have been sharpened to points in a pencil sharpener.

These can be screwed into the blind nuts so that when the wing is positioned they will mark the location of the holes. for drilling. Useful when you can't get at the back of the nut plate.

Chris Barlow24/01/2016 16:01:26
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1858 forum posts
1266 photos

Thanks Peter. blush

I think I'll make a pair of M6 and M5 marker bolts! I have akways used the nylon wing bolts which are usually quite tight to screw in. Not a problem with the ballerina but with most fuselages you have limited space and end up screwing them in 1/8th of a turn at a time with just finger tips, then have to get them out again! Steel bolts would be much easier!

Chris, the fillets can be made after the fin and tailplane are fitted but you'd need to make sure the fin is square to the tailplane when gluing up. The fillets will also be harder to sand flush with the tail empenage in place. Shaping them whilst pinned on temporary 1/4 blocks is much easier to do and get right.

AndyD24/01/2016 16:31:37
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712 forum posts
503 photos

ive given up worrying about wing seat gaps as for many years i lay a piece of film on the wing then had a smeer of car body filler to the fuz and bolt the wing in place,as soon as the fillers gone off and not lleaving it to long to go rock solid remove the wing trim with a knife job done,perfect fit.

McG 696924/01/2016 16:37:00
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2716 forum posts
1019 photos

Thanks, Chris.

Of course, it's (again) so easy to understand with the proper explanation.

Just hoping to get a little less stupid each & every day...

Cheers

Chris

BRU - BE / CTR Stupidity Control

Percy Verance24/01/2016 17:49:16
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8108 forum posts
155 photos

I'd echo Peter's comment. An object lesson in how to build a model aircraft............ yes

Peter Miller24/01/2016 18:23:07
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10323 forum posts
1231 photos
10 articles

I like the idea of metal marking screws. Must get a couple made!!

Neat idea for getting perfect seating for the wing too!!

john stones 124/01/2016 18:50:24
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Yes I agree with Peter a Master class, best give you a star star

John

Chris Barlow25/01/2016 23:55:11
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1858 forum posts
1266 photos

Thanks John. You'll be pleased to hear the scalloping has been done between the stringers now. At the same time I wasn't completely happy with the shape of the cockpit sides so they have been re cut as well.

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Tonight I spent an hour looking at photo's of vintage and classic air racers to get some ideas and inspiration for a colour scheme and I think I'm a bit closer to a design although I'm still not sure what to do with the tail.

Just a hour in the shed tonight so I concentrated on sorting out the extensions for the wing servos. I cut the plugs off the servo leads 6" from the ends. These were then soldered to a single 6 pin multiplex plug.

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Two 6" lengths of servo wire were then soldered to the other side of the multiplex plug and female servo plugs crimped onto these. Another 2 lengths of servo wire were cut and one end soldered to the lead from the servo and covered with heat shrink tubing. The other ends were fitted with male servo plugs. This makes a soldered servo extension from the servo to the fuselage which will plug into the multiplex plug which will plug into the RX.

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I could have used a single "Y" lead or two servo extension leads from the RX but I prefer to be able to adjust each wing servo independently and retain the option of spoilerons or flaperons, not that I foresee using them but old habits die hard! The miltiplex plugs also simplify setting up at the field and reduce the possibility of reversing the servo plugs costing time to take the wing off again to swap them over!

Peter Miller26/01/2016 08:51:57
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10323 forum posts
1231 photos
10 articles

Using ailerons out at the tips as flaperons is asking for instant and massive tip stalls. Don't DO IT!!

john stones 126/01/2016 16:25:27
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10759 forum posts
1481 photos

Piece of tape on leads of a matched pair is how I do it, going separate channels for ailerons as well, I doubt i'll get horns over the hinge line so I can dial it correct, and put in any differential it may need. You putting some piping around cockpit cut out when covered ?

John

Chris Barlow26/01/2016 17:41:44
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1858 forum posts
1266 photos

My flaperons are usually reserved for strip ailerons and I doubt the Ballerina is going to need them anyway looking at the wing! I'm expecting it to just float in. laugh

John yes, coaming around the cockpit with padded head rest, instrument panel etc. Going to have loads of time to tinker with the details bit!

Chris Barlow28/01/2016 02:34:19
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1858 forum posts
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Started applying a few bits of covering this evening. Still not completely sure what I'm going to do but I figured if I start putting on some colour something will pop into my head! crook

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AVC28/01/2016 07:01:47
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539 forum posts
147 photos

Very nice building blog Chris, a lot to learn here!

I still don't know how I will finish mine. I have some purple at home and bough some yellow last week, but this green you're using is quite smart, and I've never had a green model, so I may try something with it...

john stones 128/01/2016 14:45:09
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10759 forum posts
1481 photos

Ah you do the covering different to me, I do sides then top as single piece, your way has less joins, green looks a nice colour Chris

John

Chris Barlow28/01/2016 16:44:20
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1858 forum posts
1266 photos

I'd recommend your way John. Having the joint down the centre line entails quite a bit of patience and heating/stretching of the film. I was expecting to mess it up, cut it back to just the sides and then do the top with a third piece but fortunately it has worked.

The green is Solarfilm dark green. I was kinda thinking British racing green sort of scheme?

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