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DH84 Dragon

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Chris Reid23/04/2018 15:19:35
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216 forum posts
95 photos

The nacelles are done. There was some design work to do as their build advanced and, if the project becomes a magazine plan, I will simplify what I had to do to get things to come out as they should. That said, I am well pleased with the outcome. After final finishing, they will look the part.

nacelles finished 2 rs.jpgnacelles finished  1 rs.jpg

Timo Starkloff23/04/2018 21:02:59
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351 forum posts
787 photos

Very nice!

Chris Reid26/04/2018 09:07:40
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216 forum posts
95 photos

Now the engine nacelles are finished, I have got back to the bigger bits. The wing mounts are in, and I've got to planning the wiring of the lower wing which will carry leads for motor power, esc, and aileron servos outboard of the wing joint. I have made up the battery wiring with plug connectors, but inevitably I didn't have enough male 4mm plugs for the female ESC connectors so Ebay will be supplying more. I've also installed the ply plate that will carry the undercarriage on the lower centre section.

A step forward with the fuselage was adding the 1/16" sheet sides. The windows were glazed on the inside after painting the window edges red to match the red hobbyfilm covering to be added later. I made an experimental window and found that the film can be ironed on to the window edges and then the glazed area exposed by careful removal of the film with a sharp blade.

The next tasks will be the wing joiners, sorting the closed loop cables for the elevators and rudder, and sheeting the fuselage top and bottom.

fuselage side 2 rs.jpg

fuselage side rs.jpg

michael harper 228/04/2018 12:04:14
14 forum posts
5 photos

Looking good and a big fan of DeHavilland aircraft. I'm looking to start the Dale Tattam DH Tiger Moth and the Dumas Dragon Rapide. If you want any help drawing up plans, give us a shout, can do it on computer using Microstation.

Chris Reid29/05/2018 12:40:58
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216 forum posts
95 photos

1st assy 1 rs.jpgThanks for the offer Michael, maybe I'll take you up on it. I have flirted with CAD in the past but like all software, learning it in the first place, and then not forgetting the detail is a pain. Also, I can't cope with designing on a small screen, so big sheet of paper and a drawing board it is. I learnt engineering drawing nearly 60 years ago and I'm now too old a dog for new tricks.

The Dragon proceeds. The cockpit has been glazed, it was a bit fiddly but it has come out well. The secret was to use very thin material which coped with the curves. I use Pacer Formula 580 Canopy Glue. It's thin like water, dries transparent, and really holds well.

The basic undercarriage fixing to the lower wing has been designed and built, and the 16 wing joint fixings for the plug in outer wings done. I'm using alloy tube and carbon rod as joiners. The pic shows the first fix with cyano to locate everything in position. The tube/rods are now bonded to the spars with glass cloth and epoxy.

Big day this morning with a first assembly of all the bits. Everything goes together OK, and the model does look like a Dragon. Lots of work still to do with detail fitting, wiring, and finishing, but the end is in sight.

wing join 2 rs.jpg

Chris Bott - Moderator29/05/2018 13:45:45
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Ooh isn't that nice!
Percy Verance29/05/2018 16:02:40
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8108 forum posts
155 photos

NIce indeed! I much prefer the Dragon over the Rapide with it's frighteningly pointed wingtips.

Looks a nice handy size Chris. Biplanes always seem to look larger in any given size than a monoplane.

What's it weigh just now Chris?

Chris Reid29/05/2018 16:25:15
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216 forum posts
95 photos

I haven't weighed it yet Percy as there's still quite a lot to do. I tend to overengineer my designs a bit, which is a mistake as crashproof models can't be done. So it may weigh a bit more than it could. However, I always build in plenty of electric grunt which cures all ills!

Edited By Chris Reid on 29/05/2018 16:30:13

Edited By Chris Reid on 29/05/2018 16:31:04

Percy Verance30/05/2018 06:14:49
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8108 forum posts
155 photos

Hi again Chris

A friend I often fly with has built what I think may be one of your designs. The Agritug? He has commented on how well it flies. He widened the fuselage by about 8mm just to make radio installation a tad easier.

Again the Dragon looks impressive. Might you be making the plan available Chris?

Chris Reid30/05/2018 09:35:53
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216 forum posts
95 photos

Hi Percy, Agritug is indeed one of mine, and one of my most regular fliers for its nice airborne manners. My latest," Mignon", is another up coming favourite for the same reason; although to be fair it is a steal from Chris Foss's Wot 4. I am coming to favour smaller simple models, although "close to scale" aircraft (as is Agritug) have featured a lot in my past.

I'm guessing that Dragon may be my last go at a pretty complex model. I have been taking build photos and writing up the construction methods with a view to publication, although the detailed drawing required will be a big task. David Ashby has encouraged me so I think it will become a project later this year. I will have to fly Dragon first, and with several holidays coming up, completion won't be for a while. Biplanes do look larger, and its not to much of an illusion because they have twice the wing that they really need. An outcome of their wire braced box structure. Dragon is 60" span because she has to fit into the back of my SEAT Arona. (I prefer smaller cars too).

Percy Verance30/05/2018 14:02:46
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8108 forum posts
155 photos

Hi Chris

I seem to be moving to smaller models for some of my flying too. Oddly Chris, I was looking at the Mignon plan feature just yesterday afternoon!

I've never really been a big model fan, as I find the enjoyment of flying is the same even with a smaller model. Plus smaller models are more economical to build. The attraction of the MIgnon for me would be the fact that, should I find myself at a loose end for an hour or two, I could just pop the model in the boot of the car and drive the couple of minutes or so to my flying field on the outskirts of my village.

I'll be watching the Dragon closely Chris. It would make a good winter project I think.

michael harper 204/06/2018 20:03:51
14 forum posts
5 photos

Looking very good Chris. I started drawing on a drawing board years ago and saw how it was changing to computers, so I did a course on AutoCad. The company I was working for installed Microstation which is so easy to use. Never looked back. Just send me a message if and when you need a hand.

Cheers

Mike

Chris Reid05/06/2018 08:27:24
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216 forum posts
95 photos

Hi Mike. How would you work? RCM&E CAD my pencil plans, but I have to do the drawing and annotations. I guess I would have to do the same for you?

Chris Reid11/07/2018 14:55:51
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216 forum posts
95 photos

aileron servos 3rs.jpgaileron servos 2 rs.jpgIt's amazing that six weeks has passed since the last build update. There's not much to show for the time either as I'm at the stage where small details take a long time to do. The top and bottom of the fuselage are now sheeted and the fairleads for the closed loop tail surface control cables installed. There is a lot of work to do to finish the wings, but I have installed the aileron servos using a favourite, fix them on their sides to a thin ply plate, method. The wings now need final sheeting of their centre sections, installation of all the wiring with plug and sockets at the joints, struts sockets, and getting a precision fit where they join the fuselage. The engine nacelles will need the same care to fit them to their position on the lower wings. Beneath them, I have to make up the dummy oleos for the undercarriage. They will be close to scale in appearance, and will have some springing as I know from experience that inflexible undercarriages don't work well.

Looking ahead. With the demise of Solarfilm, the model will be covered with Hobbyking film - a good product that shrinks well, albeit it doesn't stretch as well as Solarfilm. I have been trying to find a paint to match the red film as Hobbyking don't make exactly matching paints like Solarlac. A Humbrol red in either enamel or acrylic looks like it will do. It will be needed for the wing struts, and possibly the nacelles if the compound curves prove too difficult to cover with film.

An aside reflecting modern times. Yesterday afternoon at 1430 I ordered some servo extension leads on eBay. They were delivered at 1100 this morning!

I have been chatting with RCM&E editor Graham Ashby and have pretty well agreed that I will offer the Dragon as a plan for the magazine in due course. In parallel with this blog, I have been taking build pics and writing construction notes as the build progresses. I hope it flies!

Percy Verance11/07/2018 17:12:57
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8108 forum posts
155 photos

Hi Chris

Well I'll certainly look forward to the Dragon appearing as a plan in RCM&E Chris. It has all the makings of an absorbing winter project.

Looking at those little blue servos. They look identical to a handful I bought a few years back, ans as with all new servos I buy, I put them on my servo tester 3 at a time on continuous cycle. Within minutes they got very warm on a 4.8v pack. I held back from using them as I just felt they didn't inspire confidence. Do yours get warm on test Chris?

Chris Reid13/07/2018 21:04:38
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216 forum posts
95 photos

I've used lots of the Hobbyking cheap small servos Percy, mainly the HXT 900 and 500. I don't do deep cycling just run them a little on the servo tester to ensure they work properly. After all, in the air, they aren't motoring most of the time. Buried in the airframes I've never bothered to check for warmth. I have only had one fail and it ran away to full deflection on an aileron on a first flight - see my Vickers 151 blog elsewhere here. Hobbyking admitted that they had had failures due to poor quality gears, my failure, and refunded the cost. This was a whole $2.50! My scottish ancestry means that I tend to buy at the cheaper end of the equipment market. Almost everything we buy these days is made in China, and by and large we get great value for money. In the early electric days I bought a small brushless motor and esc package at a special Show price of £90.00! I'd just sold a design which paid for it. The same outfit would be a quarter of that today.

Chris Reid27/09/2018 16:52:19
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216 forum posts
95 photos

It's been a long glorious summer, but it's meant that the Dragon build has slowed down. Holidays with grandchildren, and repairs to parched grass have taken their toll on the work rate.l.

However, I've now got back to the build and I'm on to the fussy final fitting stage which always takes much longer than you expect. The metal tube components of the undercarriage oleos are done but now need their streamlined fairings. The servo wire connections for the ailerons across the wing separation joint are also 90% complete. I've used the system I used on my DH60 Moth. The centre section female connector is glued into a small slot in the joint rib. The outboard, removable, bits of the wing have a small box built into their inboard ends with a larger slot in the rib within which three inches of servo cable with the male connector can be stowed. When the wings are joined, the carbon rods are slid into their tubes and the cable extended to plug into the centre section socket. When plugged in, the wing can be closed up to the joint, and the excess cable tucked into its little box. I haven't sorted how I will lock the wings in position yet, but a wire U shape like a large staple that will insert vertically across the joint is a favourite idea.

Two small other jobs done are fitting in the 16 pieces of 1/2" balsa with a small slot in them which will take the 8 wing struts. These will be made from streamlined metal tube with 1/16" ply ends. Once the wings are finished and covered, the slots will be opened up and the wings assembled on the fuselage. The struts will then be plugged in and secured with a dab of cyano, or maybe PVA. Each strut will have a small hole drilled at its end through which I will thread some bright silver cotton simulating the stainless steel bracing wire of the full size. The model is too small for proper bracing wire end fittings, and in any case the wings will not need bracing for rigidity.

Finally, I've started finishing the nacelles with sanding sealer and dope prior to painting them. I decided that Hobbyking film won't stretch around the compound curve shapes. A Halfords aerosol of Fiat orange red looks like the right shade to match the film. However the full size aircraft has different shades of red on various bits so it will be sort of scale if it doesn't quite match.

aileron connection 2 rs.jpgaileron connections 1 rs.jpg!

michael harper 229/11/2018 11:22:59
14 forum posts
5 photos

Any updates on build ?

Chris Reid29/11/2018 14:32:40
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216 forum posts
95 photos

Slowish progress Michael, but some has been made, and all of the woodwork is finished. This latest pic shows the final build with the ailerons installed and, not visible the lower rears of the nacelles. The undercarriage oleos are on board with their streamlined fairings, and all the wiring to aileron servos and motors is in place. The oleos have springs inside their aluminium tube structure as I discovered when building my Scottish Aviation Pioneer that rigid dummy oleos deform if landings are heavy. All that remains now are the 4 inner and 8 outer wing struts and covering. I'll use red and white Hobbyking film, and have found that Humbrol 19 red enamel is a good match for the film so I will probably hand paint the nacelles rather than mask up and spray with an aerosol. The decals have been made by my local friendly sign maker. The struts and dummy rigging will be installed after covering when the centre sections of the wings will be fixed semi permanently in place, and the outer wings plugged in in pairs for flight. I've done a "show and tell" session at my Club when the model was well received. It's been fun to do, but taken rather longer than I expected. I suspect I'm slowing down as anno domini advances!2nd assy 1.jpg

michael harper 202/02/2019 11:08:31
14 forum posts
5 photos

Looking good.

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