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DB Cirrus Moth 40 Electric build


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Nice job Martin ? 

I've had one of these in the refurb pile for years and there's a nice article in an early Aviation Modeller International which shows a great improvement in scale looks can be had by adding rib capping strips and dummy rib capping strips to the leading edge. These then give the correct number of ribs and just look nice under the covering. I'll watch this thread with interest. 

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  • 2 months later...

Ok so another couple of months have past and i am cracking along to finish of the Moth build, it has not been the most enjoyable of builds due to the poor fit in a number of areas, this is no reflection on the current D.B laser cut kits, by all account they are a great fit with good wood selection. My guess is that this kit dates back to the 70`s by the box and sparse instructions, the ply parts are also delaminating with age! These disappointing areas have caused me to lose interest on several occasions and push it to one side for long periods, i am sure it will look the business once finished and fly great as all the D.B Moths do. I have a couple of kits i am itching to get on with but i am determined to finish the Moth before i get going on something else otherwise it will never get finished! A lot of work has been done in the last few days and construction WILL be finished by the end of next weekend and covering will then be started, i enjoy that bit so i am only a week away. I rested the top wing onto the cabane assembly to get a bit of inspiration, it is starting to look like a bipe now. 

moth test fit.jpg

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The thin ply rear decking fought me all the way despite wetting and banding it round some foam pipe lagging for several days, making sure it was glued down all the way along the sides was a real pain but as you can see i think i now have it pegged! ? Work is now concentrating on the interplane struts, sanding to shape and adding the fixing points which are split pins through a hole drilled in birch wood beams glued into the wings. Fuselage is upside down in this shot, just so you know i haven`t put it on the underside instead of the top!

pegged rear deck.jpg

Edited by martin collins 1
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Cabane struts bound and epoxied last night, i used cotton, hope that should be strong enough with the epoxy, it holds the cabane wire structure to the top wing in effect as the wing is slotted into the two arms at the front and bolted at the back. Instructions say use piano wire (somehow i missed that bit!) Do you think it will be strong enough to cope with a few loops? If not i will drill some more holes and use some fuse wire to strengthen it............

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No piano wire in my kit Jonathan, this one came out of the Ark, i guess it wasn`t supplied back then. A number of parts i have seen on other peoples builds are nice and laser cut, here they are given a part number in the sparse instructions but you have to make it yourself by using scrap wood and shaping. It will also have some balsa added underneath over the binding which will be the shaped underside of the dummy fuel tank in the centre of the wing, which will add a small amount of extra strength in preventing any thoughts of separation in that area.

Edited by martin collins 1
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Martin,

You have built this correctly. I think you are misinterpreting the instructions (unless they are written wrongly...).

The piano wire parts are the two U-shaped parts that you have bound to the ply wing platform and to the spruce struts using cotton. You would not use piano wire (even thin stuff) to bind the struts to the platform. Cotton is fine, the epoxy gives it the strength.

I had one of these models for many years and it never failed structurally. It would have had over 1000 flights, it eventually fell to bits due to fuel soakage at the front end. I have a replacement (of the later version) from a past club member that requires a bit of work to get flying.

Brian.

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Thanks for the extended flight test using cotton Brian ?, the instructions with this kit do actually say` Drill holes in the cabane platform for the piano wire binding` But following the structural integrity shown by your model i am happy that it will do the job sufficiently.

The wetted plywood front decking is currently bent over a round cardboard tube for a couple of days to help bend it to shape for gluing to the fuselage as it was all wobbly in shape due to age and dampness from storage. Jobs today are trimming the cabane struts so the top wing sits square to the bottom one and drilling the holes in the top wing for the fixing bolts and epoxying the brass tubing that the bolts fit through, i will also bend the elevator joiner wire to shape........M

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Hi Martin,

 

It's just different interpretations of the wording of the instructions... they do really mean "Drill holes in the cabane platform for the binding for the piano wire".

 

Even using (say) 22swg piano wire it wouldn't be possible to thread it through all of the binding holes and bend it sufficiently tightly over the 8swg (or whatever it is) wire struts. I can't find my original plans and instructions for the DH60 but do have them for their Tiger Moth (virtually identical structurally) and the instructions say "sew the wire struts onto the platform".

 

It will be plenty strong enough... also bear in mind that the bottom of those cabane struts just glue into slots in the fuselage sides and they are strong too.

 

Your model is looking good, keep the tailplane and fin / rudder as light as possible as they are solid balsa. The later ones are built from laser cut parts.

 

Brian.

 

 

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  • 3 weeks later...

Getting close to the end of the build now, sitting on it`s undercarriage it looks a lot more complete, got the fin to add, all surfaces have been slotted for the hinges, motor and esc are in so we are almost at the covering stage. Once the cockpit area is covered the top wing can be glued on, that is all finished with the cabane struts already mounted.

Moth on undercarriage.jpg

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Ply top decking trimmed to clear the cabane struts, happy with the fit now so tomorrow the covering can finally begin ?

I will be using Polyspan with thinned non shrinking dope before painting. The top decking will get covered first followed by the rest of the fuselage, this will also be painted before the cabane struts are glued on as it will make it awkward to paint the area between them once in position.

 

DH 60.jpg

Edited by martin collins 1
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  • 2 weeks later...

Quick update on the Moth, i have been plugging away in the background and tonight i finished the covering which has all been done with Polyspan. Tomorrow i hope to get a couple of coats of thinned non shrinking dope on it which will then just leave the scale paint scheme to do and attaching of the control services and balancing, it could finally be finished by the end of the week ?

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  • 3 weeks later...

The Cirrus Moth build is basically done now, it has the Silver on it but the two secondary colours will have to wait to be done outside when it is warmer in the spring (too much spray dust indoors even with sheets down!), after that some scale detail will get added such as exhaust, instrument panel and pilot. It was test flown today with three sorties in blustery condition and it just needed three clicks of down trim, even that may come off on a calmer day. It balanced right on the marks with no added lead, flying weight at the moment is a tad over 6lbs, no more paint needs to go on the rear end so lead won`t be required after the rest of the paint is done. The build has been frustrating at times due to the problems associated with a 1970`s kit where holes were drilled incorrectly and instructions minimal but i got there in the end and am looking forward to getting plenty of flights on it over the winter months. I will update here in the spring once it has all the paint and detailing on but that is it for now.  

Maiden flight Moth.jpg

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  • 4 months later...

I've given the exhaust pipe problem a little thought. 

 

A couple of weeks ago I needed a lightweight tube to give some guidance to a screwdriver for the wing removal on my Peter Miller Rans Chaos (it's mid wing and the 6mm wing bolt screws upwards from the bottom with about a 3" gap).  I hit on the idea of making from papier mache, using a piece of aluminium tube, protected by some cling film, as a mould.  I used newspaper and watered down PVA as the adhesive (as opposed to the flour and water I used at junior school 70+ years ago!).  It worked really well and is very light.   The straight part isn't a concern - it's just longer than the 3" one I made for the Chaos. The curved part is a bit trickier but, as weight isn't an issue it might be possible to use copper plumbing bends.  After the paper/PVA has dried it's just a matter of slicing it open with a scalpel, removing the tubing, then glueing back together.

 

Not thought it through properly but I think it'll work.  The short piece I made is surprisingly stiff and strong as well as weighing next to nothing.

 

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Edited by Geoff S
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Nearly done now, just got the exhaust, a bit of undercarriage detailing and the wheels to paint. My scheme is that of Lores Bonney, she attempted to become the first woman to fly solo from Australia to England, her first attempt ended in a forced landing in a storm and much damage to her Moth. Whilst it was being repaired Amy Johnson did the trip but in the opposite direction. Undeterred Lores flew Australia to England to be the first solo woman to make the trip in that direction, her aircraft was named My little ship. Pictures taken today just before i flew it again.

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Edited by martin collins 1
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