DH86 Refurbishment

[Danny Fenton]

Thanks John, yes made from chemiwood on the lathe.

[RottenRow]

Hello John,

 

I mentioned yesterday that I'd post a couple of pictures of the strut screw fixings on my Rapide, here they are in case they are of any use to you. When screwed right down the heads are flush with the surface.

 

The rigging brackets are fixed to hardpoints in the wing panels using small self-tapping screws. These will be replaced by small countersunk screws but I didn't have them at the time. I have since bought those from ModelFixings.

 

I'll send another post in a minute as I can't figure out how to get the cursor underneath these photos to continue typing on a slightly different topic!

 

Brian.

[Danny Fenton]

Type as you would normally, place the cursor where you would like the picture and click the uploaded picture at the bottom of the window. Carry on typing and again click the next picture to add it.

If you do not they all get added in a line at the end. A carriage return between pics makes it easier to read.

Cheers

Danny

[RottenRow]

Hello again John,

 

I was also interested to see your glass lenses for the landing light in the nose of your model, as I am just working on that part on mine at this time.

 

I made mine from clear polypropylene film, 0.020" thick, which I moulded over the nose which had been previously carved and sanded to shape, then given several coats of sanding sealer and smoothed with fine paper. The film was just clamped onto a piece of ply with a 2" diameter hole in it, it was then heated with a hot air gun until it sagged a little, when it was quickly forced over the nose (the model's not mine!). It took a few attempts to get the right shape. The original nose was then cut off and bored out to take the light.

 

The light itself is the front part from a cheap LED torch as sold on eBay. They are focusable but, as bought, each time they are powered up they come on in a different mode: bright, dim and flashing. A quick bit of soldering and the dim and flashing modes are removed. The front aluminium bezel on the one in the model has yet to have some excess material cut away. These are cheap off eBay (I just bought 5 for under £10 from an English seller). Being LED they are pretty bright but don't produce a lot of heat.

 

I haven't fixed the lens yet but will be doing so with a rim made from lithoplate and tiny screws (Mick Reeves), the full-size has this arrangement so it will look ok.

 

Your glass lenses look good though, that may be a better option (and quicker than the moulding method, which I can't repeat easily now that the nose has been cut off). The glass lenses will be tougher too.

 

Brian.

[RottenRow]

Thanks Danny,

 

Like This...

 

 

And this...

 

 

Got it now! I had tried all sorts of combinations! I've also worked out how to reduce the size so they are no so "in your face".

 

Thanks for explaining.

 

Brian.

[John Rickett 102]

Quote

 

Thanks for the pictures Danny and Brian, as is often the case they reveal interesting details other than the focus of the topic. One of my lifetime regrets is not learning how to use a lathe and I marvel how something as innocuous as a gunsight can lift the sense of realism in a cockpit.

I also very much like the Rapide seats, the cushions have captured a sumptuous look not often achieved when we try to reproduce upholstery, well done Brian.

Back to the landing light, I'd advise, if you haven't already done so, to go outside on what you consider to be an otherwise suitable flying day and try the light again, standing as far away as possible from the model and see if you are satisfied with the power, If you are, then that's fine but I've been disappointed up to now with leds. They are convenient and stay cool but really don't compete with halogen in the lumen stakes.

I made a mistake earlier when I said my lamp was 50w, I was confusing myself with another model, its actually 35w (12v). I'm retaining it as it's bright but also it works in conjunction with a ground signalling lamp installed under the front fuselage which I was going to cover later in the restoration.

Brian, if you would like one of these cabochons I'm happy to post one to you, while I always like to keep reserves of anything I'm unlikely to need a further 19. If nothing else it won't get crushed if you tend to store models by standing them on the nose.            

[Trevor]

On 12/03/2021 at 17:11, RottenRow said:

. . It will have the BEA livery of the full-size that currently lives at Old Warden but belongs to Philip Meeson.

Brian, I was lucky enough to have a good look around this beautiful example when it was hangared at Bournemouth and based my own Rapide on it:

http://www.bartonhewsons.uk/home/modelflying/scale/rapidediary.html

 

I always try to make a point of going to say hello to it when I get to visit Old Warden. If you need photos of any particular aspect, I'd be happy to look back and see whether I've got anything that would help.

 

Trevor

[RottenRow]

Hello John,

 

Thank you for your comments regarding the seats, they are just balsa and Plastruct tubing. Actually I only included them here to try out Danny's advice on how to embed the photos in my test.

 

I take your point with respect to the landing light, and as it's sunny today will do exactly as you suggest. A friend has used these LED torch fronts as the landing lights in a 1/4 scale Super Cub (in the wing) and I remember they were alright. I haven't been impressed by other type of LED torch (the ones with multiple LEDs but just a clear plastic disk on the front). I have found them of very little use even as a torch! These ones use CREE LEDs with a boost circuit, a focusable lens and are similar to the modern lights some cyclists now use. Some of the eBay ones are of better quality than others.

 

I may well take you up on your kind offer to send me a one of your cabochons. I store my models in all sorts of ways wherever I can find space (sometimes on their noses) and hadn't considered that with this one. Many are hanging up from the garage roof, I'm not going to manage that single-handed with this one. Even building it is tricky due to lack of space, let alone storage when it's finished.

 

Brian.

[EarlyBird]

I am in awe, speechless as I am obviously in the company of master craftsmen. I have so much to learn, but that is where the fun is for me. 

[Danny Fenton]

I will vouch for the cree units, i have them in both my Chipmunks, and as they swing onto finals the light is very visible even in sunlight.

I know the cub you mention, it was Ady that put me on to the CREE.

Cheers

Danny

[Danny Fenton]

John, i bought a Myford ML7 and just started figuring it out. I calculated that first prop washer cost me about a grand. But each prop washer gets cheaper ?

Trouble is whenever i use it, the credit card is involved. A hobby in its own right, and you always need something else......

Edited March 14, 2021 by Danny Fenton

[RottenRow]

3 minutes ago, Trevor said:

I always try to make a point of going to say hello to it when I get to visit Old Warden. If you need photos of any particular aspect, I'd be happy to look back and see whether I've got anything that would help.

 

Hi Trevor,

 

That is a lovely model. I have just looked up the link that you provided and realised that I had read that a year or two previously. Your moulding of the landing light lens was what probably (subconsciously) I remembered and did in a similar way! The same probably partly goes for the seats too.

 

I am in the very enviable situation of living close to OW so (covid excepted) get to say 'hello' to the Rapide and all of the other aircraft there on a regular basis. I had been regularly popping in for inspiration and photos. Winter 2019-20 (prior to covid) the Rapide was in the maintenance hangar so I had some interesting views then. One of the technicians took my camera into the cockpit and photographed that for me.

 

I am a member of the OW model flying club that very luckily gets to use the airfield when there are no public events taking place. I always feel very priveleged to be able to do that, but don't do it often enough. Also a good place for coffee and cake in the restaurant! Hopefully that will be possible again soon!

 

Thank you for the offer of the photos.

 

Brian.

[RottenRow]

15 minutes ago, EarlyBird said:

I am in awe, speechless as I am obviously in the company of master craftsmen. I have so much to learn, but that is where the fun is for me. 

 

Thanks EarlyBird but don't count me as one of them, far from it..... the learning is indeed a large part of the fun and we are all still learning.

 

13 minutes ago, Danny Fenton said:

I will vouch for the cree units, i have them in both my Chipmunks, and as they swing onto finals the light is very visible even in sunlight.

I know the cub you mention, it was Ady that put me on to the CREE.

 

Yes that's the one. It was Ady that put me on to them initially, and I got him to modify them to give just the single high-brightness mode, as his used to go into whichever mode they fancied! I often call for Ady at the BMFA scale comps.

 

I have one in a (yet to be completed) Seagull Chipmunk, which I bought as a crash damaged model.

 

8 minutes ago, Danny Fenton said:

John, i bought a Myford ML7 and just started figuring it out. I calculated that first prop washer cost me about a grand. But each prop washer gets cheaper ?

Trouble is whenever i use it, the credit card is involved. A hobby in its own right, and you always need something else......

 

My ML7 came from the factory I used to work at just before it was demolished. It doesn't get used nearly enough (turning down the CREE LED front bezels is one of those uses!) and mostly just for odd jobs on my models and classic cars. As Danny says, a hobby in its own right and one that can become addictive and time consuming......

 

Brian

[RottenRow]

Here are the results of the outdoor landing light tests on the Rapide. The day here (Bedfordshire) started sunny but has since overcast, so I have tried this in both light levels.

 

As mentioned, the lights are focussable (is that a correct word?) and that makes a lot of difference to the shape of the beam and therefore the perceived brightness and different angles. A fairly narrow beam, is more intense and I would say more akin to the full-size. The focus is simply a sliding in and out of the light source with respect to the lens so I will experiment more with this when the model is more complete. Once I am safisfied with the setting it will be locked in place with a blob or something suitable but removable such as silicone sealant.

 

With a 1.5V AA cell (not too relevant as the light increases this to whatever the LED takes, a little over 3V I think), and the beam set to 'long', I am very happy with the results. Having watched the full-size on a few occasions I'd say the model light is if anything brighter, in fact brighter than the photos suggest. The only slight down side is the colour temperature (a bit 'cool', like modern car headlights).

 

Sunny from about 15 feet.

 

 

Sunny from about 50 feet

 

 

Overcast from the same distance

 

 

John, I'm sorry for highjacking your topic somewhat with this. I'd like to try one of your glass lenses if I may, though I'm not sure what effect that may have on the beam pattern. In exchange I'll send you one of the torches I just received, you will be able to assess it for yourself to see if you can make any use of them in your models. Failing that it will be useful as a small torch for looking inside fuselages for those dropped servo screws etc...

 

I think I can send you a personal message and we'll go from there.

 

The overcast sky is getting greyer, so I'd better go outside and bring the model back in!

 

Brian.

[John Rickett 102]

Ok Brian, I'm pleased you've satisfied yourself that the brightness is to your liking, its best to try these things before all is glued in permanently - I've learned the hard way! A reply has been sent to your personal message so can get a cabochon winging its way to you.  

 

[John Rickett 102]

Before adding the captive nuts in the interplane struts for the left wing, I thought I'd better assemble the model (minus the interplane strut) to make sure the outer wings lined up with the stub wings in the fuselage. Alas, on the left upper wing force was needed to slide on the wing and this made the leading edge rise and the trailing edge fall, obvi ously not a satisfactory state to be in.

 

 

 

Closer investigation showed that during the previous hasty repairs, probably when I tried to remove as little covering and sheeting as possible, I had ended up gluing in the replacement tube out of line.

Now with all the covering stripped away I felt much less reticent in removing sheeting to effect a decent repair.

The picture below shows the offending joiner removed from the wing stub and a new joiner in place with doubler ribs glued in for support

 

  

 

Finding the correct position to drill the new hole was achieved by inserting a piece of sharpened wire which was slightly longer than the joiner depth into the outer wing 

 

 

With the rear joiner in position as a guide it was a fairly easy job to line up the wing and then gently press the point into the wing rib to mark the spot. After that, using the same sharpened wire inserted into a slotted brass tube to hold the position, a neat hole could be cut for the new joiner.

 

 

 

A few load bearers made from 1/8" ply

 

 

Two of the ply squares were added, plus a capping piece, glued with slow cure epoxy and warmed with a heat gun to make the epoxy fuse into the balsa. Some 1/16" supports were glued to the underside of the existing sheeting as supports for the infill piece.

 

 

The infill is now in place and the associated imperfections smoothed with lightweight filler. The filler is wonderful stuff - I think the makers of lightweight filler have missed a trick by not selling it in Boots as a cosmetic aid, it hides every known crease, wrinkle and ding! 

      

        

[Jon H]

Bit of news from the engine shed. I have finished and fired up the two 62's and both run well. One is a tiny bit faster than the other but generally they are both doing fine. 

 

They need a good bit more running to really come on song but they behaved really well on the bench. If at all possible, i would set up a wot4 or something like that and give each engine an afternoon of thrashing before refitting to the DH. If thats not possible, give them a tank on the bench using a 12x6 and really give them some abuse. Plenty of high power runs and lots of acceleration from idle. 

 

I hope to give the 50's a go soon. 

[John Rickett 102]

Ok Jon,

Thanks for the reply. That's really good news about the 62s.

 

I don't have a model that will readily accept a single 62 so will do as you recommend and run them hard on the bench before refitting them.

 

Let's hope the 50s come out the same, then that's another hurdle crossed.

 

Once they are all done I will take a trip and collect.  

[Jon H]

I have managed to get the 50's done and they are mostly ok. 

 

Those replacement rings were a fair bit oversize and both engines were really tight. I was hoping they would come in when i ran them and while one was ok one engine was still really tight even after the run so i had to adjust the ring gap a little to try and help it out. Both engines run ok and spit out the same peak rpm (9300 on APC 12x6 vs 10000 flat from the 62's) but compression is pretty poor when hot which is a bit of a shame. 

 

They do run happily though and didnt show any signs of giving up the ghost so i would run them as they are. 

 

What you could try is the old italian tune up. Fit them to the model and use a smaller prop, 11x6 or something like that. Fire one engine up a thrash it to within an inch of its life for about 5 minutes. Warm it up, then tune/hold max rpm for 15-20 seconds or so followed by another 10 seconds at a throttle setting 1000rpm lower than the full power rpm you see. Then, 15-20 seconds at idle to cool it down. After that some hard acceleration up to full power and back down, 4 or 5 of those really slapping it open and then hard shut back to idle. After the 5th, hold open for another full throttle blast. After 5 minutes of that sort of thing shut it down, do the same to the other, and then back to the first for round 2. Repeat until bored (2 runs like this per engine should do the trick, but keep going if you want!). 

 

Giving the 62's a similar treatment wont hurt them either and at the very least it may help you feel confident in the engines. In all honesty, you could probably just fit them and forget all about it. They will trundle along at mid revs without fuss i am sure. But, i dont like to settle for mediocre so i would give them a thrash and see if they raise their game. If not, you have not lost anything...other than perhaps your hearing. 

 

 

[John Rickett 102]

It’s been 6 months since adding to this topic, spring suddenly arrived and with it all the outdoor jobs and activities as well as a satisfying amount of flying, consequently there’s been no progress on the DH86. Running concurrently with this refurbishment has been a 25 year old DB SE5 getting similar treatment, although not as extensive as the DH86. I had continued with that model during the summer to get it painted during fine weather; it’s now complete so with the arrival of autumn and few other distractions, time to continue with the DH86.

Now reunited with 4 rejuvenated little Lasers thanks to Jon at Laser Engines I thought I’d continue with the engine departments including the fitting of cooling baffles as recommended.

The first job was to remove all the softened paint in the engine bays and cowls. Nitromors paint stripper doesn’t seem to be available anymore, but No Nonsense stripper available from Screwfix gets good reviews so I bought a couple of bottles and applied it liberally. It did a reasonable job and after an hour of soaking, then scraping and reapplying to the stubborn areas most of the paint came away. The remaining paint was removed using 180 grade wet and dry cloth.

 

Finally, a wash in warm water brought the parts to a good base condition.

 

Looking decidedly in need of TLC 

 

Not bad considering the softened paint. The engine bays had been given a coat of fibreglass resin during the build and this has undoubtedly saved the wood. Its all good,  just doesn't look very nice. I think another coat of fibreglass resin, warmed with a heat gun to flow into all the crevices, will afford a bit more protection, then a liberal coat of 2K paint     

 

When the model was originally built, I hadn’t discovered a truly fuel-proof paint or lacquer. The paint was Humbrol enamel sealed with Tuffkote, sadly it didn’t work very well. Wherever there was an edge, fuel or exhaust residue would wick its way in and it wasn’t long before the paint was lifting. In the difficult to clean areas the paint just softened, I’ve since discovered Klass Kote which is effective so will use this with its satin catalyst for the new finish.

As an aside 2K car refinishing paints are excellent, fuel proof, available mixed to whatever colour is required and not as expensive as Klass Kote. The one I’ve used is Lechler from Humberside Paints, online its Paints4u. This paint gives the highest gloss I’ve achieved with my domestic spraying equipment but it wouldn’t be in keeping with a 1930’s fabric covered aeroplane so I’ll pay the extra and use Klass Kote.

 

The paint beginning to bubble

 

This is the other outer panel but it shows how the surface can be rescued. 

 

While painting the SE5 during the summer and with paint mixed, I thought I might as well do some bits on the DH86, it all helps with maintaining enthusiasm.

 

Props getting the paint remover treatment

     

 

Refinished as aluminium lookalikes

          

[EarlyBird]

Good to see this progressing again those props look like new. 

[Manish Chandrayan]

Thanks for the latest updates. Good to see some progress ?

[John Rickett 102]

A bit of experimenting to find a suitable baffle shape for the outer engines

A block of balsa was glued up, cut to shape and then covered with parcel tape to act as a release agent

 

A few layers of 80gm cloth provided a shape of sufficient rigidity, I thought

 

 

The first stage of trial and error sanding to get the baffle to fit in the cowl

 

This is what the baffle has got to do!

 

Cylinder area cut away to allow the engine to slide in

 

It may work but I think its too close a fit and won't provide much cooling to the silencer.

 

I think the method proves the concept so I'll start again and make the shape about 1/2" wider at the back. As it is, the baffle is only just large enough to clear the grub screws that hold the carb and exhaust and may make fitting the cowls awkward, so a bit more clearance should help without letting too much cooling air to bypass the fins.  

[Jon H]

thats a neat idea for a cooling shroud and it should work nicely provided the air can escape out the cowl. With the shape of the cowl that large hole on the bottom may act as and inlet and not allow the hot air out. 

 

As a simple guide, mount the cowl on the model and prop the tail up so the model is in its level flight attitude. look at the cowl straight on and see if you can see the hole. If you can, so can the air and it will become an inlet and not an outlet. 

[John Rickett 102]

You are probably correct that the outlet isn't very efficient. In the picture I've set up the wing with an incidence of 4 degrees to the table, Its a guess that this is the angle of attack when flying but probably not far off. I've then tried to take a picture head on, (you can just see the filler tubes poking out) the outlet hole is just visible.

My train of thought is that much of the air entering the inlet is going straight over the rocker cover so if I can redirect some of that through the fins it will be an improvement. The model has already had over 100 flights without the engines showing distress so the cooling only has to be improved marginally.

I'll try to keep the mixture on the rich side, there's no call for all the power these little machines can supply.