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Geoff's DB DH60 Moth

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Geoff Sleath14/02/2018 22:08:50
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2604 forum posts
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Thanks Simon. I've actually bitten the bullet and 'invested' in a 5 metre roll of Cub Yellow Solartex (just a few days before Solarfilm announced their closing) so that's what I'll be using on this build. However, I seem to have got into building scale models from the so-called golden era (the late 1920s/1930s so not quite as golden as we like to think) so I could well take advantage of your research.

Pretty all I build these days is electric or electric conversions so fuel proofing isn't an issue. However, I have a Hurricane build in the offing which will be Laser 80 powered so fuel proofing will be needed in that case.

thanks again.

Geoff

Geoff Sleath16/02/2018 13:26:33
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2604 forum posts
198 photos

A little more progress. Whist cogitating on the motor mount/battery access modifications I made an effort to reduce the number of parts still in the box by building the tail components. I did bui;ld over the drawing but really with CNC cut parts it's more a matter of assembling and using the drawing as a guide as to which part fits where. I think, apart from waiting for the aliphatic glue to set, it's as quick as solid sheet because the parts just fit neatly together. I added a couple of extra corner pieces cut from left over scrap balsa to the fin post. Probably unnecessary but that fin post carries a big powerful rudder and the extra weight is negligible. The tail is very light which will help the GoG.

fin_rudder.jpg

tail plane.jpg

Having cogitated, I trimmed the 9mm x 15mm plywood engine plate supports by 5mm each (except where they pass through the former) to give a bit more room for the motor. Then hacked out a motor mount plate from 6mm ply. Once the fuselage is almost complete, I'll decide where it needs to go to put the prop in the right place and then I can determine the offset to bring the prop into the middle with the required right thrust (I think it's around 2 degrees).

fuselage 6.jpg

Geoff

Geoff Sleath16/02/2018 14:39:45
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2604 forum posts
198 photos

This puzzles me a bit. The instructions state:

"The 3x5mm diagonals 123 are set back from the external surface of the fuselage."

I can't see why that should be unless it's some scale feature but there's lots of scale features that are ignored (closed loops for the rudder and elevator or the tail plane struts for instance). I think I'm going to ignore the instruction and just fit the diagonals pinned to the board.

fuselage 5.jpg

Actually the next line says little about a lot

"Build the port side in a similar manner"

Not so easy as it involves actually cutting strip to fit accurately rather than simply assembling CNC cut parts as for the tail. Dwain mentions building the port side over the starboard with an intervening sheet of film (I use cling film) to stop joining them together.

The build isn't too difficult for someone with a little experience but I would think it quite difficult for a total beginner. At least I know the end result will be a good flyer.

Geoff

Geoff Sleath23/02/2018 15:22:03
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2604 forum posts
198 photos

I'm trying to fit the cabane but there is a discrepancy between the parts supplied and the drawing. All the drawings I was involved in at work were circuit diagrams but they used the same paper as mechanical ones and all bore the legend in big letters "Do Not Scale". In view of the dimensional uncertainty of those old smelly blueprints perhaps that was sensible but we aeromodellers have no alternative because the drawing we work to are usually undimensioned. We have to scale the prints themselves.

cabane fitting.jpg

It seems to me that the supplied cabane piano wire supports are 3mm longer than the drawing (which is the thickness of the top wing platform. The platform has cutouts in the corners which have no purpose unless the spruce parts of the cabane extend upwards to glue in them. In fact the front corners have bigger cutouts which I guess are to accommodate the angled front support.

I'm just steeling myself to cut 3mm off the ends of the piano wire before glueing the spruce and wire together so I can fit the top wing.

Another difficulty I'm having is how to ensure the top wing is exactly symetrically positioned wrt to fuselage and in line with the bottom wing (which is now fitted and with tips equi-distant to the tail). I was expecting to fit the platform and cabanes then put the wing in place held at the front by the wooden hooks. It would then be possible to swing the wing slightly to get it exactly right, then drill the holes for the captive T nuts. Unfortunately, the T nut holes are predrilled which means the only method of minor adjustment is to move the whole platform a fraction.

It may be OK assuming my building is accurate to a degree I'm not normally guilty of If not, I'll make another platform and drill the holes after assembly.

In the meantime here's a picture of the fuselage as it is so far:

fuselage 9.jpg

The rear cabanes are held in place temporarily with cocktail stick dowels, which hold it surprisingly well.

The motor is fitted at the correct down and right thrust. I had to make a new front plywood former but just had to fettle the balsa front a lot for the motor to be far enough forward. When glow engine is used the hole only need to be big enough to allow the prop shaft through but the motor itself needs to be close to the front in this case.

motor fitting 4.jpg

 

motor fitting 5.jpg

 

There were a few adventures earlier which I won't bore you with. Suffice to say progress is being made

Geoff

Edited By Geoff Sleath on 23/02/2018 15:28:31

Dwain Dibley.23/02/2018 16:01:09
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917 photos

Geoff,

I think I made a slot for the extra piano wire in the side of the fuselage Mate, as I too was reticent to cut them.I then made the aluclad plates to cover them, to replicate the plates on the full size.

D.D.

Geoff Sleath23/02/2018 16:45:49
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2604 forum posts
198 photos

That's slightly reassuring, Dwayne. I thought you'd had an issue with the cabane fitting but I couldn't find it on your build blog. At least I know I'm not deluded (at least in this respect!). I've just finished cutting mine .

How did you fix the platform? I'm not super keen on the stitching method as it doesn't allow any minor adjustment to get the wing correctly aligned assuming you can't do it by moving the wing on the platform (which you can't with the CNC cut parts). Perhaps it won't be necessary. I'll find out soon.

Geoff

Geoff Sleath23/02/2018 18:20:30
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2604 forum posts
198 photos

Managed to do a trial fit and actually have something that looks a bit like a bi-plane, even a DeHaviland bi-plane.

first assy.jpg

The bottom wing is properly fitted but the top wing is held with a combination of clamps, elastic bands and will power. Surprisingly, everything seems to be quite square. The top wing is parallel to the bottom one and both are square to the fuselage. The distance between the wing tips is about 4mm different (in 260) but considering the jury rigging I think that will be fine when it's all assembled with inter-plane struts etc.

One item of concern is that the piano wire fixing to the wing platform runs right along one of the lines of holes intended for stitching rather than between them on both front and rear, which means the stitching won't work so it will have to be glued on.

Geoff

Percy Verance23/02/2018 19:19:51
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6479 forum posts
110 photos

Hi Geoff

As I recall, the cut-outs in the ply top wing platform are intended to take the top ends of the cabane struts. And yes, the forward ones need to be slighly elongated to take the angled struts.

Stitching the platform on is absolutely fine Geoff, mine didn't shift in 20 odd years. Sure, there is no adjustment but none is needed. Just get the angles correct Geoff and all will be fine. Boddo knew his stuff!

I'd drill some new holes for the stitching Geoff. Don't be tempted to bend the wire, although as you've glued the cabane struts in place, you won't easily be able to re-bend the wires..... Stitching and a liberal application of pva or aliphatic Geoff, and it'll not shift mate......  I glued some 1/4 sheet to the underside of the wing platform, and then sanded it to an airfoil-like section Geoff.

 

 

Edited By Percy Verance on 23/02/2018 19:25:50

Geoff Sleath23/02/2018 20:14:51
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2604 forum posts
198 photos

Thanks Percy. As I mentioned, it all turned out to be square anyway but it would have been nice to have a little wiggle room if necessary to get the wing at the correct angle.

I guessed the cutouts were supposed to take the wooden part of the cabane struts (as did DD) but with the supplied piano wire being too long (even by only 3mm) making them too short to fit in the cutouts it threw me for a while. It's not shown - or at least not clear.

The instructions suggest covering the piano wire with masking tape and epoxying to the underside of the platform as an alternative to stitching. Certainly masking tape works well as an interface for glueing things like snakes and it certainly sticks well to the wire on the upright section of the struts. I've no real problems with the stitching except that the ready drilled holes are exactly covered by the piano wire so I'd need to drill 2 more rows which might weaken things too much. I certainly won't try bending the piano wire.

Once I've got the cabane sorted out I'll put it on one side and fit it after I've almost completed the fuselage. Battery hatch and mounting; cockpit openings; cowl etc etc. Still plenty to go at and these problems make the build more of a challenge and add interest.

Geoff

Percy Verance23/02/2018 20:47:29
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6479 forum posts
110 photos

Geoff.

The idea of recessing the diagnals on the rear fuselage is so that the covering doesn't adhere to them, as I don't think they're scale in any way. It's an often used *cheat* to add rigidity to a structure without it being visible on the finished model. I have yet to try the masking tape trick to bond piano wire to wooden parts, but I understand it works well.

Again, I can't recall any issues with the length of the cabane wires, although I made some card templates up to ensure I got the top wing platform just where it was intended to be. I'm sure that if the wires had been slightly over length, I'd have just lost the extra length in the fuselage cut-outs or snipped it off.

If you do decide to drill new holes in the wing platform Geoff, just fill the redundant holes up with aliphatic to restore some strength. 

 

Edited By Percy Verance on 23/02/2018 20:55:05

Dwain Dibley.23/02/2018 23:11:28
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921 forum posts
917 photos

img_20170413_163639.jpgimg_20170416_160352.jpgDitto to all that Percy has said...........I will just add that I think I bolted everything up with the wires stitched on( I had the same hole probs, but used them anyway) got it all square, as PV says it is pretty accurate, then I Glued the twine with CA, this turns it to Iron. I then dismantled it all and used aliphatic on the stitching, once that was dry I added the Balsa and sanded to shape.As you say Geoff, fit it for good after all the fiddly bits.

D.D.

img_20170224_164215.jpg

Edited By Dwain Dibley. on 23/02/2018 23:20:04

Geoff Sleath24/02/2018 00:11:07
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2604 forum posts
198 photos

Thanks, Dwaine. I suppose if I don't bother too much about the wooden pieces tightly butting up to the platform cutouts then the stitching will work. I have some perfect twine for the job - thin and very, very strong. I think my wife brought a whole cone of it from work, where they made clean room overalls. Can't think what they used it for, all I know is that there must be miles of it - literally.

I notice you put the wing retaining hooks at the outside rather than towards the centre as in the drawing. I don't suppose it matters. I put mine as per the drawing partly because that's where it is on my DB Tiger Moth.

One thing I did do differently from the instructions was to fit the 0.4mm ply decking before the cabane struts. It was quite easy to cut the slots accurately as no doubt you found as well. I rolled it up and left it overnight to take shape. It worked a treat and was straightforward to fit. Sadly, when I tried the same trick on the tapered piece for the rear fuselage it split and I had to make a new piece - after ordering a sheet from SLEC crying

I have most of the material to make the sprung undercarriage.  I ordered some springs today.  It's this design by Gordon Whitehead.

undercarriage drg.jpg

 

Onwards and (eventually) upwards.

Geoff

Edited By Geoff Sleath on 24/02/2018 00:17:34

Dwain Dibley.24/02/2018 09:19:45
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921 forum posts
917 photos

Yes, I found that I got a closer fit on the struts by gradually removing the ply.

Wing retainers.....just put them out of the way of the Stitching in case repairs/adjustment was needed, the added bonus being it was less wobbly.

That undercarriage will be the Mutts Mate.  thumbs up

D.D.

Edited By Dwain Dibley. on 24/02/2018 09:20:49

Geoff Sleath24/02/2018 11:13:39
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2604 forum posts
198 photos

Having seen yours, I wish I'd put mine further out. It's a better position both for keeping clear of the stitching and, being wider based for stability. I should have read your build thread more carefully

No building today. Got a load of stuff to organise for a swap meet. I keep building and I need to clear out planes and engines that I'll never use. I hope to get home with an empty car ... that's if I don't buy something myself - but Avice will be with me to keep her tight hold of the family purse strings devil

Geoff

Percy Verance25/02/2018 07:14:09
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6479 forum posts
110 photos

Hi again Geoff

I fixed my wing retainers on the top wing plate just where DD has his. I also used a countersunk screw from underneath in addition to the glue. It didn't shift or break loose in 20 odd years. Mind you, not crashing the model helped! My Moth was one of the nicest flyers I ever had, and it was with regret I parted with it. I must have had hundreds of flights over the 20+ years I flew it, some of those being at the Scale Weekends at OW. I feel better since I bought a new kit from DB Sport & Scale while Eddie Stocker was at the helm. A far superior kit compared to my 1990 die-crushed original. However, despite the less than perfect quality of the very early 90's DB kits, the basics were always spot on - cheers Boddo - and they fly very well!

Edited By Percy Verance on 25/02/2018 07:18:40

Geoff Sleath25/02/2018 15:29:14
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2604 forum posts
198 photos

The drawing shows countersunk screws as fixings for the wing retainers but doesn't supply any in the kit so I used some servo screws instead. I must have 100s of various sized wood screws/self tappers but none the right size. The screws will be hidden by the dummy fuel tank that's glued under the platform so it doesn't matter much.

I'm in the process of sewing the cabane struts to the platform and I'm sure it will be fine. Even though the cutouts for the struts aren't quite right I'm sure it won't be noticeable.

The swap meet wasn't all that successful from my point of view because returned home with most of what I'd taken but the arduous 5 mile journey and the cost of a table was more than offset by the sales. There were a few familiar faces there including Paul Marsh but I didn't see him leave with another model so perhaps he won't be adding to his tally on the 'New Models' thread If nothing else, it was a good social event and even my wife enjoyed it.

Geoff

Edited By Geoff Sleath on 25/02/2018 15:29:59

Jan Luethje03/04/2018 00:46:42
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Hi there, I’m a modeler from Berlin and just wanted to say thanks to everyone for the great advice I received here, while building my DB Sport & Scale Cirrus Moth 20 E. It’s a nice kit an fun to build, but obviously not very widespread in Germany, because I couldn’t find any German build thread.

I started building last november, overtaking some mods from Martyn Johnston (e.g. „fake riplets&ldquo, also developed some own mods, and now I’m more or less at the same stage like Geoff with his Cirrus Moth. It’s really interesting to see, that he and I came to pretty much the same solutions for similar problems.

Like him, I decided to attach the lower wing section with screws instead of rubbers and reinforced the lower center correspondingly. Like him, I made a new plywood front former for the electric engine, instead of building „a box in the box“ for mounting the motor.

There are still some points to be sorted out, but I’m quite confident to maiden the bird at the end of the season. And also hoping to see the original in flight at Shuttleworth Collection during the summer

Geoff Sleath23/05/2018 16:55:27
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2604 forum posts
198 photos

My Cirrus Moth is (almost) finished and flying (over a dozen) but I'm afraid I got a bit lazy and stopped posting progress reports. However, I did take a few photos and I'll try to add a few of them in the hope it might help subsequent builders. There's a few dodges I used that may help others like installing snake outers as guides for the tail closed loops (2 for the elevator halves) and ignoring the warning of using a simple pivoted bar for the rudder control (the out of tension wire just goes slack and there's no problem).

Another dodge was to make a motor safety/arming plug in one of the motor feeds using HiFi 4mm gold sockets and a short wire with 4mm plugs. It works perfectly and has the advantage that the controls can be checked without the motor starting inadvertently. Coupled with a throttle disable switch on my transmitter there's very little danger of damaging the motor and avoids any potential problems with extended battery leads.

Geoff

g-aamt - 1.jpg

However, I still have a little problem - the exhaust pipe. As you can see here, my model lacks one.

pict0114.jpg

I bought some thin walled plastic pipe about 10mm diameter which would look OK but I can't think how to create the double bend where it snakes round the cabane supports. Are there any suggestions? It looks OK pipeless but I'd like to get it a bit nearer scale even though it is, at best, sport scale.

Geoff

Percy Verance23/05/2018 17:05:49
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6479 forum posts
110 photos

Jan

You will enjoy the Shuttleworth Collection. It's an amazing place to visit. Look out for the Me 163 Komet tucked away in a corner of one hangar.

Oh, and welcome to the forum! yes

PeterF23/05/2018 18:54:19
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322 forum posts
546 photos
Posted by Geoff Sleath on 23/05/2018 16:55:27:

 

However, I still have a little problem - the exhaust pipe. As you can see here, my model lacks one.

 

I bought some thin walled plastic pipe about 10mm diameter which would look OK but I can't think how to create the double bend where it snakes round the cabane supports. Are there any suggestions? It looks OK pipeless but I'd like to get it a bit nearer scale even though it is, at best, sport scale.

Geoff

 

Geoff,

On my Tiger Moth exhaust I used thin wall plastic tube for the exhaust, although that only has a single 45 degree bend at the outlet end. I bent it using a hot air gun to soften it, but first, I put a piece of thick wall silicone tube inside that was a good fit. This meant that as the tube was bent, the silicone maintained the shape and stopped the bend collapsing. In your case if you tried this, the silicone tube may end up stuck as a permanent fixture.

Peter.

PS, nice looking model, love the colourful schemes available on the Moth series.

Edited By PeterF on 23/05/2018 18:58:29

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