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DB Cirrus Moth build

Electric conversion.

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Dwain Dibley.19/02/2017 23:26:37
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1268 forum posts
1267 photos

I thought i would share my efforts building the DB sport and scale Cirrus Moth.

I am going to chop it about and make it leccy powered.

The kit itself is very comprehensive, delivery was the very next day, Kudos to Richard for that. There are a few issues, the ply formers are a bit warpy, but a night under some weight sorted that out.

One of the other main formers was slightly short at the bottom stringer, but again, an easy fix with some scrap.

By mentioning these few issues, i am not having a go, but merely highlighting the simple solutions, as its too easy to lay blame, and I don't want things to descend into a slanging match

Wood is by its very nature,susceptible to moisture in the atmosphere, and needs to acclimatize to our workshops/sheds/dining rooms etc.

Political shpeel over.

Here's the progress so far.

G194019/02/2017 23:51:10
3523 forum posts
1 photos

I've got one to build as well and mine will be electric, too. 4S with a EMAX GT3526/05 710kv. I have a DB Tiger Moth (as in my picture) with a similar motor but the higher kv version which is also on 4S and flies well on a 12x6 prop.

I had to put lead in the Tiggie to get the CoG right so make sure to get the battery as far forward as possible. I'm thinking of making mine a moth Major which has a similar cowl to the Tiggie just help in getting the battery near the front. Perhaps as G-ACNS on page 179 of Stuart Mackay's DH60 book if you have it.

Geoff

Dwain Dibley.20/02/2017 00:03:36
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1268 forum posts
1267 photos

First Job is to cut the copy plan into sections.

Plan cutting

Sort through the bits.

Parts laid out

Glue the doublers in place making sure we make two opposite sides not two the same.

I use Aliphatic glue at this stage, and a bit of weight.

Fuz sides

Sustenance.

The Snack

Test fit a few formers to check the fit and spacing of the doublers.

Formers

Having built the starboard side we have to make an identical port side. The easiest way is to build it over the first one. So a sheet of plastic is applied to stop it all sticking together.

second side

It fits.....smiley

The diagonal braces are placed away from the outer edge of the fuz.

good fit

Below you can see the sliver of balsa i had to add to make up the bottom of the former F6.

times 2

Another test fit. All seems well.

mock up

Mock up of the power system just to see how drastic the chop will be. seems like an easy fit so far. these are not the items i will be using BTW.

battery

More doublers and the engine bearers, I still fit these for strength and to hang my fabricated fire wall on.

doublers

Yet another test fit. I am a bit of a belt and braces type....blushsmiley

F1

Cheers

D.D.

Edited By Dwain Dibley. on 20/02/2017 00:09:02

Dwain Dibley.20/02/2017 00:17:52
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1268 forum posts
1267 photos

Hi Geoff,

The 4 Max set up I was looking at for this seems a bit under powered, your motor has a lower KV and a 4s lipo, George suggests a 1190 kv motor on 3s 2600 i think. this is about a 600W setup. He knows his stuff tho so i will investigate more.

Re schemes, I like the two tone fuselage look.

Cheers

D.D.

G194020/02/2017 00:47:24
3523 forum posts
1 photos

The set up for my Tiggie is:

All up weight is 3.14kg with a 4S 4000 mAh LiPo installed. EMax GT3526/04 870 kv motor with a 13x4 prop. Cruise current about 20 amps and max recorded during the flight about 50 amps. I changed the prop for a 12x6 which seems to suit it better though the take off run is slightly longer but still short. So max power is 750/800 watts and cruise is about 300 watts. IIRC the esc is a 60 amp one.  I usually fly for about 8 minutes and there's still plenty left in the battery. I think 10 minute flights are quite possible.

I decided on the motor with a lower kv for the Cirrus Moth so that could run a bigger prop for the same current. It's well over the top for the Moths but I'd rather have a big motor and battery than more lead. I certainly wouldn't go down to 3S. I've reduced the lead a bit and moved the CoG further back and it's still very stable.

Geoff

 

Edited By Geoff Sleath on 20/02/2017 00:50:38

Dwain Dibley.21/02/2017 00:01:37
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1268 forum posts
1267 photos

Below is the type of scheme I am hoping to go for. I know this is a flight sim pic but its pretty nice.

14314-dehavilland-cirrus-moth-g-cauazip-2-25308010.jpg

 

Edited By Dwain Dibley. on 21/02/2017 00:05:02

G194021/02/2017 01:02:10
3523 forum posts
1 photos

Well it's certainly a scheme that should make the model visible in the air. Very good choice and makes a change from the more common silver wings and red fuselage like my Tiggie.

Geoff

Former Member21/02/2017 01:04:45
3578 forum posts

[This posting has been removed]

Jonathan M21/02/2017 07:26:03
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671 forum posts
275 photos

Good progress Dwain.

I've got the 20E kit and an OS 30FS for the right vibes (for me), and look forward to following your build!

smiley Jon

Dwain Dibley.22/02/2017 01:04:23
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1268 forum posts
1267 photos

Thanks Geoff. laugh

Yes Tom it's bigger than I thought too, after doing some research as you do. surprise

Jonathan, I Do love the sound of a Four stroke, and I still have a lancer with a 40 fs, and an sc 70 on the shelf, but find glo/nitro such a faff these days....sad

But it's whatever floats your boat matey and it's all good.

Here's the progress for tonight despite having to stay at work an extra two hours, I managed to glue some more bits on and get the thing jigged up.

Cheers

D.D.

Got the rear deck on to see what it looks like.

img_20170222_000452.jpg

Top formers.

img_20170222_000604.jpg

Front end.

img_20170222_000528.jpg

I have left this former loose so that I can use it as a template for the extra firewall for the out runner and/or a top hatch.img_20170222_000514.jpg

Front end, laminated from a ply former and 2 X balsa formers. All this meat will be sanded to profile towards the end of the build of the fuz. The cowl is a vac form item made up of two halves, I could make this into access to the motor and speedo, and also fit a dummy engine. Lots to think about when doing an electric conversion, some of which needs to be done en route so to speak....Well it's easier that way, although some time you have to back track.....Don't ask me how i know....blush

img_20170222_000548.jpg

G194022/02/2017 11:59:52
3523 forum posts
1 photos

Are you going for scale closed loop controls for rudder and elevator? If so, now's the time to organise the wire routes through the fuselage for the elevators (there's 4). The rudder's not a problem because the wire is all outside but install the the centrally pivotted lever mount as soon as possible.

I was given my Tiggie part built and it was quite difficult to arrange the wire routes through the fuselage when it was already covered. I run them through snake outers to exit in (roughly) the scale positions. So think about it now.

Geoff

Dwain Dibley.22/02/2017 15:06:21
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1268 forum posts
1267 photos

Were you outside my work shop this morning Geoff ??? wink It's as if you were listening to the conversation I just had with my mate Johnny.

I was just saying that I am doing the pull pull external rudder, I dunno about the elevator yet tho.

Well, I found another tiny niggle today, not the end of the world but could be annoying if you don't have spares knocking around the workshop, as it would or could delay the build a bit.

The book of words says add the M4 captive nuts, but there are only M3 nuts supplied with the M4 Bolts. Also the holes in the bottom wing retaining former are drilled for M3 nuts. I chose to redrill for M4 and use the supplied bolts in my spare nuts. You could of course replace the bolts for M3 ones but I think (imho) that they would be a bit small.

Cheers

D.D.

img_20170222_135559.jpg

img_20170222_135715.jpg

Dwain Dibley.22/02/2017 15:20:20
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1268 forum posts
1267 photos

The next step was to add more doublers to fuz sides to aid the location of the servo bearers.

I always make my own removable servo trays for ease of maintenance but it is not compulsory. wink

I simply screw these down onto the bearers.

While the bearers were drying, glued with Aliphatic, I made up the wing retaining plate, and sanded the servo bearers to size, about a 16th off each one.

I also made up the skid and pulled the rear of the fuz together, I made a stronger bottom fill piece to take the buffeting from our patch.

img_20170222_140331.jpg

img_20170222_142534.jpg

img_20170222_142900.jpg

Edited By Dwain Dibley. on 22/02/2017 15:23:30

G194022/02/2017 15:24:38
3523 forum posts
1 photos
Posted by Dwain Dibley. on 22/02/2017 15:06:21:

Were you outside my work shop this morning Geoff ??? wink It's as if you were listening to the conversation I just had with my mate Johnny.

I'm surprised you didn't spot me peering through the window

You got to go for closed loop elevator control with separate, unjoined elevator halves. It's compulsory if you're doing that for the rudder. It's not really all that difficult. I just put both top wires on one side of the servo horn and both bottom ones at the other with tension adjustments at the control surface horns.

On the Tiggie there are 3mm metal bolts holding both wings in place. They're easier to hide at the top and it works fine. I wouldn't bother with nylon bolts.

Geoff

Dwain Dibley.22/02/2017 15:38:46
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1268 forum posts
1267 photos

The plan has 4mm bolt for bottom wing and 3mm for the top wing, and yes, I will be using metal bolts from my spares box. However, if anyone reading is wondering.... there is a reason for using nylon.....in the event of an arrival they will shear and possibly save some repair work.

re the elevator servo, I had imagined having to put it on its side , that is to say the arm ( big double) would be in the vertical plane, is that how you did it ? Like an aileron servo..

Cheers

D.D.

G194022/02/2017 15:48:25
3523 forum posts
1 photos

I don't think nylon bolts work quite so well with biplanes because, with the 2 wings joined, it's a very rigid structure anyway so there are are lots of strong points that the nylon 'fail safe' bolt doesn't really protect. Of course, I've been known to be wrong as my wife will tell you.

Anyway, as guide, here's a picture of my servo layout. The Savox elevator servo may be a bit over specified but it was one I had in stock for a project that never came to fruition.

 

db servo view.jpg

 

So you see, there's no need to fit the elevator servo in any special way. You can thank Gordon Whitehead for the rudder lever idea. It was seeing his own, slightly bigger (and much better) model of G-ACDC at the Ashbourne fly-in in 2015 that inpired me to get mine finished after several years in limbo.  The lever is made from a bit of old fibre glass printed circuit board.

Hope it helps a bit.

Geoff

Edited By Geoff Sleath on 22/02/2017 15:50:57

Dwain Dibley.22/02/2017 16:09:20
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1268 forum posts
1267 photos

Cheers it does. wink it's got to done,,

For a proper bit of redundancy you could hook up 2 servos on the elevator one for each side, with a little mix in the TX.

I've gone into Anorak zipped right up mode blush

Cheers

D.D.

Chris Whalley22/02/2017 17:04:49
17 forum posts
1 photos

Hi guys coming to the end of my build, I am trying to insert a photo of it, hope this works out aok

Chris Whalley22/02/2017 17:07:24
17 forum posts
1 photos

DH 60The photo seems to have ended up in the wrong place, will have to study the add a photo part of the forum

Edited By Chris Whalley on 22/02/2017 17:09:50

Dwain Dibley.22/02/2017 17:10:19
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1268 forum posts
1267 photos

upload to an album from pc, you will have to create one, then click camera icon at the top of the thread and choose pic from album drop down list, to add to thread.

Bit long winded but works ok.

Cheers

D.D.

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