Cirrus Moth Build 2

Those little tiny clamps are really, really useful.

Not sure how I should have clamped the front half of the top ply. There’ s quite a lot of glue escaped. Very thin ply (nice peice of ply Eddie) just overlapped onto the balsa sides. Difficult now to smooth down.
It’s the cowl next.

The instructions suggest glueing the two halves together, but I’m not sure what sort of glue to use. I think it’s ABS plastic.

I though of just taping the two halves together and using them as a mould for making a fibreglass cowl. I’ve never done much fibreglassing but I’ve got a small kit, so that might be fun.

What do people suggest?
Put clear tape aka stickyback plastic aka sellotape over the join, on the outside, fold the two halves open, run a THIN thread of GORILLA glue along the edge, fold it shut, and wait three hours (+/-). Gorilla glue foams up as it cooks, so self-fills any gaps, (hence the clear tape on the outside!)

Gorilla glue sticks just about anything to anything, including fingers!, but doesn’t attack plastics or foam. If you get a run, it can be scraped off with an old credit card or blunt knifeblade, before it goes off.
I’ve heard about this ‘Gorilla Glue’ stuff, but haven’t got any.

StillI tempted to tape the two halves together and using them as a mould for making a fibreglass cowl. I’ve never done much fibreglassing but I’ve got a small kit.

What do people think of that idea? Would I need a releasing agent? Would I be able to buy a replacement cowl from DB if I screw up?
I followed the instructions, and glued the two halves of the cowl together, then reinforced with an extra strip of plastic on the inside of the join. I used some canopy glue I’ve got that says it’s OK for ABS plastic. Looks good but I’ve got a bit of a seam down the middle that doesn’t seem to want to sand out.

Just gone and bought an engine to put in it. I’ve treated myself to a Saito 72. Looks absolutely beautiful, but rather large (well, very large).

The instructions for the Moth just say something like ‘Install the engine’, and then elsewhere say something similarly unspecific like ‘plan the servo layout’. I’d have liked a couple of pictures or ideas for servo layout. The rudder and elevator lie straight but the throttle one has to travel an awkward route. Don’t know whether to lay the servo flat, and bend the wire, or lay the servo at an angle that allows a straight(ish) piece of wire. But then, as I’ve said before, it’s not a beginners model and I’m enjoying the challenge. It’s all part of the fun.

The kit includes all the parts for a closed-loop set-up for the throttle. I’d like to go down that route but can’t quite picture what to do with it. If anyone has any links to any photos of what other people have done I’d be grateful.
I’ve now set the servos in place.

– First the throttle, set at an angle so the wire, running through a piece of plastic tube, goes in a straight line to the throttle arm, which I’ve turned 180deg.- Next the rudder, which actuates a small aluminium bar which pivots on a piece of ply just behind the servo. This bar will, eventually, have the two wires attached for the closed-loop rudder control. If this doesnt work I can always rip it out and go direct from the servo!- Thirdly the elevator. This is likely to have a snake run down the fuselage, when I get one.I did take a photo but it didn’t work, I’ll take another tonight. Q’s.- Would you people still recommend a balsa push-rod for the elevator, or do you go for the more modern snakes?- If you like the snakes would you not also go for snakes for the rudder? Maybe two snakes for closed-loop control? – What about aileron control (months away at the snail-like speed I’m building at). The plans suggest a
metal rod from a single, common servo. Would people use snakes here? – Eddie, would you suggest one servo in the middle, or two, one in each wing?

This is how I’ve got the servos.

– throttle , top in picture, port side of fuselage, at an angle.

– rudder running pivoting bar.

– elevator running snake (not fitted yet)

Any comments or criticisms, make them quick, before I go much further.

Just testing the ‘panoramic’ function I just found on my camera. Lets you take 3 photos then joins them up to make one long one.

Quite pleased with the axle build.Welded the bars together, araldited a washer and tube on to the axle itself, and drilled a hole near the end of the tube for a split-pin..

Had to ream out the hole in the wheal just a tiny bit, to suit the tube O/D.

But I think that looks rather good.

No doubt there are other ways you old-timers would have done it different.

Comments always welcome.

Now learning how to fit the covering.

I wanted to wait and get a photo of the whole build in wood, before covering. But at the speed I’m going that may be some while yet.

I’ve finished the tail assembly so I’ve been covering that this weekend. And it’s actually come out really, really nice.

Only mistake here (I shouldn’t keep mentioning my mistakes; people will think I’m rubbish at this !) was on one surface of the elevator;- it was harder to stick down than the others, and it’s come out a little ‘bubbly’. Even where there shouldn’t be any bubbles at all. I can only think that I forgot to remove the protective plastic film from the sheet. But then I wouldn’t have done that because that would be really stupid !!!

I did have trouble with the mylar hinges. I trial fitted them all together (six in total). Then glued all six into the elevators. Then trial fitted again. Then put glue on the remaining halves, than had a mad panic struggle as one of them wouldn’t go in, as the other five were setting, very quickly. Rather than have all six stick only half-in I decided to push the five all the way in, and deal with the errant one later.
Seems to have worked fine in the end, but a bit of a panic at the time.

Rudder I did last, and therefore it went really well.

The fin was more difficult because of the concave front edge. I naïvely assumed that the covering would shrink round the curve, but of course it wanted to shrink to a straight line and not touch the leading edge of the wood at all. In the end I split it with a knife, and wrapped each side round the leading edge a little.

The rudder is hinged to the fin in two places, and there is also a hinge to go into the back of the fuselage itself. Not sure how that’ll work but it looks like it should go fine. That’ll be after the fuselage is fully covered and the whole tail assembly gets glued on.

Tail and wings are going to be silver. Not sure about the fuselage colour yet.

A piccy of two wings in progress.
I’m finding I can do two wings at once on my bench. Other pair willhave to wait.
I’m spending about 1/2 hour glueing, then leaving it 24 hours before being able to do the next bit.
The top and bottom trailing edge sheets went on fine.
(sign of a good design – the top and bottom t/e sheets are both 1.5″ wide, so just split a single 3″ sheet to make both).
I thought the leading edge might be more complicated, but it went on easily, took loads of those little clamp things to hold the very front down, because of the curve, but looks like it’ll be fine when I check tonight. (uses one whole 3″ sheet).
The instructions seem confusing on the glueing of the wing tip pieces. There must be a reason they tell you to glue the bits on in that order. Gluing them all together first, and then adding the sub-assembly to the wing looks easier.
Might do one wing my way and one wing as instructed, and see
Following the instructions for the wing-tips was easy.
Got a couple of questions now, hopefully for Eddie if he’s still watching the thread.
1. There’s a part on the plan (I think it’s No.244) that’s about 1/2″ wide and seems to fit along the root wing rib. I can’t see what it’s for (unless it’s just to stiffen this rib) and I can’t quite see where it goes.
2. There is a 1/4″x1/4″ hardwood piece which goes between two of the ribs, as a support for the inter-plane struts. Do you have any detail of how this attached to the ribs and/or leading-edge sheet. (ie a photo somewhere on your site)? ie on the bottom wing I suppose it glues directly under the sheet, but on the top wing does it attach level with the bottom of the wing? And how does it then attach to the strut?
I’m now going to look at Simon Webber’s build log to see if I can see any detail of these bits.
I can see where to glue the strut-retainer(s) now (top wing at bottom of rib, bottom wing at top of rib, glued directly to l/e sheet presumably). Still not sure how to attach the struts themselves, instructions say to drill a 1mm hole in the retainer for a split pin, then araldite it in. I’m sure that’ll become clear nearer the time.
Part 244 wasn’t clear but I see what you mean now. (all four wings, upper surface only).
Close-up of a wing tip.
The instructions say to cut off the spars at the tip rip,
I obviously cut off the leading edge as well !
Then I noticed that the plan looks like the last inch of the leading edge is used to blend in to the wing tip.
So I cut the leading edge back, at a shallow angle and added a new end, using a bit of 1/4″ hardwood as it was all I had available.
Doesn’t show much on the photo but looks quite neat.
Now the scary bit.
After spending many hours building a beautiful set of wings the instructions say to cut the back off to make the ailerons.
Photo shows it marked where to cut.
Time for a biscuit before I go any further.
Too late now.
I hope I’ve read the instructions right here.
And hope I’ve measured everything twice.
Ailerons now cut out and glued.
Hope it’s looking right, too late to undo it now.
Strut supports glued in. Forgot to put the metal hooks in first, hope I can do that later
I think I’ve now finished building, sanding, sanding and sanding the four wings.
I built the center sections about a year ago, when I first stared.
I’ve been putting off biting the bullet and aralditing the wing together but I’ll do it this week-end.
After building the lower center section I noticed that one of the ply wing support peices (the bit that sticks out  the side of the center section and glues into the wing) was split. I mentioned it to Eddie and he immediatelly offered to send me a replacement, But it was too late by then, I’d already glued it. So I’ve just cut down beside it and epoxied in a length of carbon fiber strip as a splint. Might have been strong enough, but I’d rather be sure.
I’ve cut slots in the inner wing ribs, to take the 4mm ply support thingies.
I’m aimimg for about 20mm dihedral.
Just to confirm Eddie (the plan’s not overly clear) that’s 20mm raised on EACH wing?
And is the dihedral supposed to be the same on the top wing as the bottom wing?
I’ve done some trial fitting, but it seems I can either get a nice 20mm at the wing end, but with the front higher than the back, OR get it nice and flat but with about 40mm at the tip.
The wing itself is nice and flat but doesn’t seem to want to fit the center properly.
Just needs a bit of persuasion !
First of the Upper wings glued to the center section.
Lower wings glued to center section.
Note: carbon reinforcement (bet the original moths didn’t have that !)

Also shows the small holes in the ribs for the servo wire. Think I’ll have to cut the wire and solder a join.

Top view of lower wing.
Glued to center section, showng ailerons cut out.
And showing (removable) servo attachment.