Building Popsie

[sparks59]

By way of a brief introduction, I'm a bit of a born again modeller who has 'returned to the fold' just over a year ago. I'll save the rest of this for my profile but suffice to say I had built a couple of parkflyer kits and was looking for something to make from a plan...

 

There are so many great designs to choose from, the 'to build' pile is very rapidly escalating to something to equal the butter mountain, however, earlier this year I laid my hands on a copy of Vic Smeed's plan for the Popsie, in pdf format, and the style of it immediately reminded me of my first free flight and rc planes of my youth.

 

I did a bit of research and found so many positive comments about its gentle flying characteristics, chubby good looks and all round attraction by many modellers.

 

During the research, I found that Replikit designer ' Vintage 1' had done a partial re-design of the Popsie and had posted up pdf's of the plan which had been digitised on CAD. Incidentally, I understand that Replikit produce a laser cut kit for the Popsie, or 'Aesop' as it has been renamed, but I preferred to cut my own timber for this build, and I shall honour the tradition of a great British model designer by keeping the name of the original model.

 

Starting out

 

I printed off two sets of the plan sheets, one for building over and the other in various pieces suitably arranged to allow rough cutting out a set of templates which I then card backed with the old gluepen and trimmed them all to size. My fingers were sore for a week after all the scissor work, but it was worth the effort in the end...I now have a set off templates just in case..

 

I then set about cutting wing ribs, I don't know why, but I have always preferred to start a model by making up the main wing, I find cutting ribs is almost therapeutic after a mentally tough day in the office.

 

I got them all cut out as blanks and then clamped them together into a block and using a small file, formed the cut outs for the spars. Then after slotting in short pieces of 3/16th to keep everything in line, I sanded the outer edges to get them all smooth and uniform then filed the leading edge notch. Lovely Jubby! Time for a cup of tea, before we get onto the better stuff ...to be continued

 

sparks

 

[Stephen Grigg]

Good start to the thread sparks and we are already on the edge of our seats for the next instalment and the pics you promised

[sparks59]

Thanks Stephen,

here's the next post! Some of the thoughts in here are taken from my build blog, and bits of email correspondence with my flying buddy who is now in Angola, such a lucky guy. Anyway, onward and downward..

I cut out the tips, leading and trailing edge and spars for the rh wing .Still have the ones for the lh and centre section tonight, then we might even get some real building done.

I was checking the plan to count up the ribs and spotted a potential monumental faux pas, good job I did, 6+1short rib on the left, 5+1 on the right, whoops, must have had a mental lapse when piecing together the plan sections! That would have gone well on anther thread on here I think! Popsie would have had some interesting flight characteristics if I had built it up eh!

 

Anyway, no problem, I had just stuck the plan together in the wrong place, doh!

The old Pops is going to be fairly heavy I reckon with all of the heavy duty balsa on her. I’m thinking about reducing the dihedral a tad as it looks to have lots.

 

Anyway, I’ll check it against the Debutante and also the MicroSquire then decide. If its near I’ll probably leave it as is and be thankful for the stability even if it is

 

After cutting the spars and trailing edge I got to thinking about building a bigger wing for Pops’ as the more I think about it, the more I realise that it will probably fly well with an extra four inches on the span, without losing the chubby Koi  carp look too much. Anyway, I have cut the balsa now so I guess it’s too late to change. Anyway it gives me an excuse to build a bigger version, or another wing later. Might even build one with less dihedral and slide ailerons into the design..

 

Didn’t get much else done, had to re-cut two wing ribs, the outers, as I must have cut the template from a smaller plan I had printed accidentally whilst doing the 'parts plan'. No problem really, I found the correct plan section and soon had them sliced out of 1/16^th. Memo to self - keep only the plan size you are going to build when making copies!!

 

Here's a photo of the RH wing, just checking out the fit of the pieces.

Set out the rh wing and glued the ribs to the 2 bottom and the top spar. Then notched the TE to suit the precise positions of the ribs and CA glued that in place.

 

Assembled, pinned and stuck the Wing tip pieces together, just need to sand / trim them a bit to fit properly and then put them and the LE on.

 

I’ll set about the LH wing as well, most of the pieces are already cut and sanded, just got to do the TE. so far it looks ok.

 

 ok, i'm taking 5 for a cup of tea and sort out the next photo to slide in

sparks

 

[sparks59]

On we go with the progress on the Pops' wing construction.

 

Finsihed adding bits and shaping the LH wing, then set about building the RH wing, got all the ribs, spars LE and TE stuck together, just the fiddly wing tips to do now. These are a bit of a problem if, like me you aren't thinking straight. The differential offset between the flat TE and the mid section LE means that the tips need to accommodate the difference. I didn't want to create wash-in so I brought the top of the wing tip up to the underside of the leading edge. This means that I had to add some fillets between the leading edge, last rib and the wing tip. It's a bit fiddly, but comes good after a good bit of sanding to blend everything in and to shape.

 

I also added some balsa fillet pieces to link the tips to the LE which is a bit of a faff and could have been designed better. I also added a little extension to the top of the outer rib to help keep a nice uniform section from the last big rib to the wing tip, its still not perfect but I think it will look ok when the covering goes on.

 

It really should have been done differently on the original design!

When I looked again at this, I think that the wing tips should have been more inclined at their outermost edge as I think this would have been a bit better to connect it all together.

 

It seems to be coming out alright, the thing that I think really helped ease wing construction, was to put all the ribs together in a block, with a set of short spars. Then sanding them to get them all about the same. The spars fit nicely in and the slot for the leading edge can also be filed / sanded to suit. That way, all I needed to do was pin the spar on top of the plan and slot the rest together, before dribbling the Cyano in! easy!

 

 

 

[sparks59]

Now to set about the centre section and the dihedral brace. Cannot find the photo's I took of this, but its straight forward, just have to remember the reduced size of the ribs, to accommodate the sheeting, and the split ribs around the dihedral brace. I'll route through my notes, as there's something else about this that needs a bit of care...

back later,

sparks

[Myron Beaumont]

sparks 59

May I suggest to put vertical webbing between the top & bottom wing main spars .It increases rigidity to an extraordinary extent --maybe 1/16 " stuff ? Grain vertical of course .

Lovely to watch a proper build by the way .  .

[sparks59]

 

 

 

[Stephen Grigg]

Lot of writing going on tonight Sparks,really enjoying you thread

[sparks59]

Got the Pops wings nearly finished, dihedral brace made and fitted them together, haven’t compared with the other high wing models but its close to the others, I reduced the recommended dihedral a little, maybe 8mm reduction at the tips I should try to work out the angle for reference I guess. 

 

Just got to fit the trailing edge, centre and the leading edge links to cut and fix, then she's sorted and I can get cracking on the tail and cutting out all the fuse formers!!!!

At this stage I was really wishing that I had made a double size or anyway a bigger Popsie now, a 48 incher or so would have been so much more majestic when bumbling past on a slow fly by. Anyway, the wings are done now, and at least there will be room for it in the flat!

 

okay, seeing this photo reminds me of the little error in my build, well one of the little errors, note the top centre spar. This is wrong, the top wing spars should follow through all the way, and the top one trimmed to sit on top. This gives greater strength to the wing and might save a fold. When I realised my mistake, I added fill pices at each side of R1 and R2's, epoxied or PVA glued to mate with the spars, ribs and dihedral former. Loads of strength returned, with only a small weight penalty.

 

I also added the leading edge connectors, these are not well described on the which indicates 2x 3/16 fillets.  I didn't think the fillets gave the right size or shape, so I made them a bit bigger, with 3/16 sheet, top and tailed with 1/8th sheet, suitably trimmed to fit snugly with the LE's but also flush with the R1 riblet back to the spar, lots more strength with no significant weight penalty.

 

Here's another shot to show the fiddly leading edge, it takes a bit of care with the sandpaper to get the shape formed, but its rewarding when it's done.

 

Now put this aside for sanding and centre sheeting later.

 

spark out

 

[sparks59]

Posted by Myron Beaumont on 14/07/2010 20:07:42:

sparks 59

May I suggest to put vertical webbing between the top & bottom wing main spars .It increases rigidity to an extraordinary extent --maybe 1/16 " stuff ? Grain vertical of course .

Lovely to watch a proper build by the way .  .

 Thanks Myron, couldn't agree with you more about the strength increase with mid spar webbing. Any way it's done now.The reason I didn't add it on my build was the size of the two 3/16 top and bottom spars. I think you could make this wing with 1/8th (or 3/32) spars and get better strength with mid spar webbing. Someone on here will probably be able to calculate the strength difference I'm sure.

sparks

[sparks59]

Decided to do the tailplane next as I'd already cut the ribs, I didn’t have any 3/16 x 1/4 for the LE, and could not really be bothered to rip some from sheet, so I decided to use 3/16sq, it seems ok, and there's plenty of strength!

The more I look at it, the more I think that uncle Vic put the elevator on the wrong side, I mean the leading edge seems to be where the TE might be.

 

Maybe its just me, apart from the wing tips, I think it looks like it should be the other way around, the ribs are of uniform section and the spars are biassed to the rear, not the front. And the wing tips curl into the LE, not the TE as they do on the main wing, anyway I decided to keep it as designed! Just need to sand it up a bit now.

 

pic's to follow ...

[Stephen Grigg]

What wing span is it Sparks

[sparks59]

Posted by Stephen Grigg on 15/07/2010 16:33:45:

What wing span is it Sparks

 It's 37", or 940mm if you prefer metric notation. The standard should have been 38.5" from memory without looking at the plan, but the copy that I produced finished up slightly smaller, but it's near enough for me.

sparks

[sparks59]

So, here's the TP. Pinned and glued, but needing some shaping which can wait until I make up the elevators. Some of the joints finished up a bit 'rough' so please don't look to close. 

sparks

 

[sparks59]

Another shot of the tail plane

[sparks59]

When I look at it now, with the elevators. I realise that I was wrong about the apparent reversal. It has reasonable symmetry. This is most probably due to the evolution from a free flight.

 

Onwards to the fin, or vertical stabiliser if you prefer,

but i'll leave the assembly of the tail and control surfaces until later.

 

 The fin base is made up from 3 pieces of 1/16th, well 4 actually, to leave a slot for the rudder torque rod to feed through. I half lapped the internal cross braces and slotted them top and bottom to get a good purchase add strength. Fins and T/p's always seem to be the bits that get knocked and finish up a little loose or flappity. So I thought a little bit of help to make them robust would be a good thing.

 

sparks

[sparks59]

 Just in case  there is anyone else out there looking in on this lonely monoblog.

 

Next up. The fuselage sides.

 

Simple construction of 3/16 stick. Lapped some of the cross-members for extra strength

 and here's two..

.

 Next up, fuse box assembly, later though.

sparks

 

[Bruce Richards]

  Watching with interest Sparks.I was just looking at the tail plane incidence on my plan and was wondering if it should be reduced a bit (not sure how) but yours looks the same as my plan. Does it fly OK like this?

[sparks59]

The tailplane incidence is set by the main central longerons at each side of the fuse. Remember that the tail will have some lift. And yes, it flies well.

sparks

[sparks59]

The original plan has the majority of the formers in solid balsa / ply. If you are building for ic, then this is probably best to stick to stock. But if you are building for 'lecky, then you don't need all that timber in the build to survive a Mills .75. Lovely as the old Mills is, any IC engine is a comparative vibratory hammer compared with a modern smooth running electric system.

 You should probably have a look at the 'Aesop' plan and may want to take on board some of Vint's design ideas. Not having access to a laser cutter, I didn't cut out the same level as detail myself, its hard enough cutting a square section out of 1/.8th ply! If nothing else, this reduces some weight, especially behind the CofG. You don't want to be adding bits of York Minster in the cowl now do you?

 

Anyway, (as Ronnie Corbett might say)I digress...Take care  when setting the formers up, as the cabin sides are parallel, but not perpendicular to the formers. You'll note the rearmost one is half a tad smaller.

 

I found it better to set the fuse upside down, ie wing mount down onto the plan and align, pin and peg everything before adding glue.

 

Once I was happy that everything was in alignment, including a check to make sure that the rear ends would pull together in alignment, I wicked the CA in. I later wiped down the joints with a little PVA ( some habits never leave us). The secret here is to measure, view, check and check again that everything is square and even before getting the adhesive out of the box!

 

As my Dad used to tell me when I was a young lad, covered in balsa cement and sawdust, measure 47 times, cut once, or glue once in this context.

 

Once that was all good, its time to add in the rearward formers, 3/16sq cross-members and bring the rear together. I left out the latter (tailwheel) former at this stage, to enable a steerable one to go in.

 

Edited By sparks59 on 16/07/2010 12:59:41

[sparks59]

I have no idea why the first two paragraphs came out bold and underlined. I tried to edit the post, removed them to an editor, changed font, format painted..but as soon as I replaced them... B and UL, c'est la vie!

sparks

[sparks59]

Here's another view of the Fuselage, with some of the formers and other cut parts on the board ready:

 

Then added the cabin rear  supports, wing dowel, upper longerons, with spruce spine

 

And a cross-piece to nicely finish and tidy the ends of the longerons at the tail....to follow

 

 

[sparks59]

This is the trim strip.

 

[sparks59]

..and I added a couple of 1/16th cross grain braces to beef up the half former..

 

 

[sparks59]

Now to work on the front end, cutting the ply formers is a real test of character!

Made up the UC wire, drilled the formers, then slotted it all together and glued it up.

 

Then loosely tied the undercarriage in, bound with a copper wire strand and soldered it up before putting all the thread stitching. Finally, coated the lot with a good coating of regular slow drying epoxy. Solid.

 

 

And added the cabin roof cross member trim