Preparing for the 2016 Mass Build

[Biggles' Elder Brother - Moderator]

Yeah, but it depends on the fuselage sides! The loads should be taken by the reinforced wing mount if the fuselage sides are just balsa in that area. But of course if the sides are reinforced with doublers there (as was the case with the Tucano) then they can be used as restraints in the roll direction and strictkly speaking then you only need one bolt. As I say it depends on the fuselage construction and how much you want to use it as a restraint.

BEB

[Geoff S]

As I see it the reason for 2 bolts is because it isn't a single one-piece wing as you build it. It's a lot easier to have a bolt in each side than try to contrive a single bolt through the part where the 2 wing sides are joined. Of course, if you were really determined to have just the single bolt you could have it in one side only Suffice to say I'll stick to a single dowel and 2 bolts which will probably be 5mm/2BA nylon.

I note that Peter suggest fitting some brass tube to hold the wing dowel so that it can be replaced at the field if there's an acrobatic rather than a ballet style landing which results in its being broken. In my vast experience of acrobatic landings I find that if they're so severe that the dowel breaks then there's always a lot more needs to be replaced/repaired than the wing dowel

I'm thinking of making the fuselage sides in 2mm liteply (which I happen to have in stock) and not bothering with doublers. It's a 48" length which means I can easily extend the sides to a more forward firewall to accommodate the electric motor. I'll probably cut lightening holes in the rear fuselage if I do that. IIRC it was how Precedent constructed the Hi Boy trainer. Not sure about the relative weights but it's just an idea as I build the wings.

Geoff

Geoff

[Bob Cotsford]

I've been looking at the plan too. My first mod will be to extend the TE sheet back to form a V and leave off the 3/8*1/8 TE strip. Why? Because I have plenty of 1/16 sheet but not the triangular TE strip.

I quite fancy a side mounted engine and the VW/Lycoming boxer engine look. I'm wondering how close an AcroWot cowl would be to fitting, otherwise maybe a dummy cylinder sticking out on the left?  Anyone got a dead LA40 or 46 going spare - I have the hacksaw

 

Edited By Bob Cotsford on 17/01/2016 10:27:24

[Biggles' Elder Brother - Moderator]

Posted by Martyn K on 14/01/2016 16:57:40:

Are we going to change the name of the topic 'The 2016 Ballerina Mass Build' because we are back on a one design again

Just my OCD catching up with me...

M

As you may have noticed - this has been done!

BEB

[Lucas Hofman]

Posted by Geoff Sleath on 16/01/2016 23:33:57:

As I see it the reason for 2 bolts is because it isn't a single one-piece wing as you build it. It's a lot easier to have a bolt in each side than try to contrive a single bolt through the part where the 2 wing sides are joined. Of course, if you were really determined to have just the single bolt you could have it in one side only Suffice to say I'll stick to a single dowel and 2 bolts which will probably be 5mm/2BA nylon.

Geoff, you are up to something here. One bolt is fine if you design the wing so that the forces (which are higher compared to 2 bolts) and the moment they create can be absorbed in the wing structure. In the glider I build which had finered wings there were hardwood inserts the with of the fuselage into the wing, and the joint was covered by glass.

I stick to Peters design for this one, probable M4. Does anyone know of nylon m4 bolt with heads one can grip with bare fingers? Or nylon M4 wingnuts? (then I insert the bolt from the top down).

Lucas

[Bob Cotsford]

Modelfixings have a range of nylon thumbscrews

Edited By Bob Cotsford on 19/01/2016 15:22:25

[Peter Miller]

I would suggest 5 mm bolts myself. or one 6 mm if you really want to go that way.

[Lucas Hofman]

Looked at the plan last night and noticed the grain on the bottom of the fuselage drawn accross. Can somebody explain why the grain in this direction is better then lengthwise?

I would expect that - like the sides- grain lengthwise would give a stronger fuse with regard to bending in the vertical plane. Obviously I miss something here, or is this a drawing mistake too?

[Peter Miller]

The grain of the bottom sheet is across because that helps prevent the fuselage from splitting lenghtwise in a hard "thump"

It may not do much but it helps.

[john stones 1 - Moderator]

Colour schemes giz a clue what to google to help find one

I typed in " colour scheme for my Ballerina" it came back...you always do em Yellow

John

[Peter Miller]

Try Airshow aircraft, racing aircraft and Homebuilt aircraft

[john stones 1 - Moderator]

Thanks Peter

[Chris Barlow]

I googled "Vintage racing aircraft" and "Classic racing aircraft"

Saw some good ideas, enough to give me a start on my own.

[Lucas Hofman]

Last night I glued the back of the fuselage together. When dry I trial fittet F7-F10 and found that they are much wider than the natural flow of the sides when the sides are closed at the rudder post:

It is probably possible to force the sides to fit the formers as drawn on the RCME plan out but is there any point in doing so? I am inclined to take of 2-4 mm of each former. Better or not?

Edited By Lucas Hofman on 27/01/2016 08:07:33

[Peter Miller]

In fact the formers on the plan are drawn too wide This has been mentioned elsewhere. From F-6 back they are about 3/16" too wide.

Also the tailplane buts up agaainst F-10 so cut the sides back tothere.

Don't ask me why these changes have been made by the draughtsman. I think he likes to feel that he is a designer. I think he is a pillock

[Lucas Hofman]

Thanks Peter, I will trim down the formers until they fit nicely.

By the way, I am encountering words on this forum I have to look up. Did you know pillock is believed to be of Norwegian origin?

[Peter Miller]

No, I didn't know it may have been of Norwegian origin. It is not very commonly use here but I like it so use it quite a a bit.

I just looked it up. Hopde the moderators don't 

Edited By Peter Miller on 27/01/2016 08:44:53

[Martin Dance 1]

I'm puzzled by the references to the over wide formers from f7-10. When I first saw this I measured the drawing comparing the widths of the formers to the width of the drawn fuselage at each former position. On my drawing only f7 was wide by about 2.5mm. I've just about completed the fuselage. I make the formers by copying them on my printer/scanner spray mounting them on the balsa/ply then cutting them out when complete all of them fitted between the fuselage sides on the drawing. When fitting them in position having followed Peter's building sequence I needed to apply slight pressure to bring the fuselage sides into contact with the formers f7-10. Then the fuselage followed the drawn plan exactly.

Two explanations occur to me. One is the printing process. Were there two print runs using different printing plates? Were there two different rolls of paper used with differing moisture contents?

The second is the building environment. I build in a dry and heated man cave/ shed! So my plan would have stabilised to the humidity of the shed which is low.

I did notice that the axis of the printed formers on the plan is at 90 degrees to the axis of the plan view longitudinal axis of the plan view. As the paper has a 'grain' and expands more in one direction than the other could this explain the discrepancies rather than the employment of a freestyle draughtsman?

[Lucas Hofman]

No Martin, these differences are much more that printing errors or stretch of the paper would be. The drawing as published by RCME is internally consistent (with the possible exception of F7), that is the width of the formers fits with the top view of the plan.

However the fuse as drawn is much fatter (i.e. wider longer aft) that my fuselage when I glue that sides together at the fin post with only F1-F6 in place. That may differ dependent on the stiffness of the balsa used for the sides.

Peter's prototype, and his drawing, also has a more slender fuselage after F6.

I just wanted to know if there was any point in forcing the sides outwards to fit the formers. Apparently not so I will trim them down until they become a natural fit.

[Chris Barlow]

I didn't change mine from the plan. They do make a fatter, more curvy fuselage but I think it looks quite nice.

[Bob Cotsford]

I've just checked the parts from my cnc/laser cut kit against the plan:

F1-F9 are all a shade narrower than they are shown on the plan view by 0.5-1mm, F10 is correct. Comparing them to the outlines drawn gives the same result.

Lucas, remember that there is a balsa wedge used to join the rear fuselage sides, you may want to actually make this about 1mm wide at the rear so that you are putting your bottom rudder hinge into balsa rather than trying to slot into the ply doublers. Also are you sure the clamp in your picture isn't pinching in the fuselage sides distorting what wants to be a gentle convex curve back from F6?

[Bob Cotsford]

ps - for reference, if you are planning an inverted engine installation an 8oz Sullivan slant front tank is the same length as a 10oz, it's just slimmer! Both the 8 and 10 oz tanks I have are an exact fit behind F1 ending flush with the rear face of F2.

[john stones 1 - Moderator]

I put a tapered piece of softish balsa between the ply doublers for the hinge 1/8-1/16, you can sand the outside to match the rudder.

John

[Martin Dance 1]

I agree Lucas, the plan is internally consistent, except perhaps except for f7. You are pointing out that the fuselage aft of f6 is slimmer than the drawing. Assuming the drawing is correct when I pulled the rear fuselage together onto the stern post the formers all fitted, after a minor adjustment of f7 requiring just light pressure to keep the formers in place so my fuselage is a tad fat. I guess that the stiffness of the material used for the fuselage sides and the precise section of the stern post accounts for the difference between our two models. he only slight adjustment I made before fixing the stringers was to sand the tops of the formers to bring them into line. Again this was only slight and accounted for by accumulated errors in making the formers. Just about to start the cowling. Initially I was going to use an old OS40 FS of 1970's vintage but a test run suggested this would not be a good choice. I acquired an unused 48 Surpass on ebay. They are very similar in dimensions but when place on an engine mount they are different by about 6-8mm. The difference is accounted for by the intake manifold! sharp right angled bend on the 40 but a curving bend on the 48.So my Ballerina will be a few mm longer than the prototype.

[Peter Miller]

The old .40 FS was gutless. The 48FS will be nice.

You can go either way with the forzmers. IT works ifbuilt as the magazine drawing shows so no reall problem.

The tailplane does need to be\ moved foreard to F-10 though.