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English Electric Canberra

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Colin Leighfield03/02/2015 07:03:32
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6001 forum posts
2504 photos

It looks the part, doesn't it? Sounds it as well! You keep on proving that you know exactly what you're doing Simon.

Erfolg03/02/2015 10:10:03
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11781 forum posts
1340 photos

Congratulations Simon.

I was amused at the frantic button pushing (the trims), as I think we have all been there. I think you are spot on that the CG is to far back.

I am intrigued at what the wind speed was.

Another personal aspect, I could not have coped with a black model, I would have gone for the Orange or yellow striped versions.That is because I have a need to see a model clearly, particularly if it is doing its own thing from time to time, I start doubting that what it should be doing in my opinion (the sticks) is the same as to what is happening.

One of our club members must live within a mile of you, he lives near the canal, not far from the cross. I know I missed you last time you came to our club, and I know that the BMFA membership is an issue for you (that is your right), I would still like to see some of your models flying either at I assume the High scholl playing fields or at our club site as a casual learner visitor. Perhaps one of your next outings?

I must confess that the Canberra is one of the few (which include the MB aircraft, Helston racer, Spiteful) UK aircraft I have wanted to build and was most certainly outstanding. Although in my case i am attracted to the USA (Martin) version, mainly because the engines being much bigger in diameter and the extra wing area.

Well done again, now what you need is more power.angel 2 bigger battery and strengthened wings. What, It wont fly as wellcrying 2

Simon Chaddock03/02/2015 12:28:48
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5738 forum posts
3034 photos

Erfolg

Just a point but as a BFMA county member so I do have insurance.

I would certainly like to fly as a casual visitor at your club. I will PM you.

There was very little wind on the day of that video but then even 2 or 3 mph is quite significant on a plane that can fly at just 5 or 6!

Toni

My 808 managed to lose the time and date and now stubbornly refuses to reset it despite going through exactly the same routine as I used to set it in the first place!

With a bit of nose weight the Canberra is now flying a bit better (video to follow) so I will completely rework the battery box again to move the battery still further forward.

Andrew Price 203/02/2015 12:38:48
821 forum posts

Simon. That looks great. The last Canberra I saw was at RAF Marham, probably 5/6 years ago. It looked as good as when I first saw one, at Farnborough, many years ago. They all looked good, as does your fantastic model. Well done You.

Simon Chaddock03/02/2015 16:11:57
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5738 forum posts
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As promised today's video.

Better but it still needs the battery moving still further forward.
It will mean a new hatch but in some respects it will be structurally better as it will remove the current hatch which creates a weak point in the fuselage..
Erfolg03/02/2015 16:42:21
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11781 forum posts
1340 photos

Yep, it still seems to have a phugoid (when landing), or is that elevator stick induced?

Was this the reason you were considering altering the incidence between the tail plane and wing? I guess you had thought that a inverted camber tail plane was also a potential attenuator? I have seen it on early RC models, although i thought to get planes to self pull out of dives, when the controls were neutral.

If it is is a phugoid, the model is not as slow as some FF models that could be seen exhibiting the trait.

I do not think i have seen one (if that is what it is) with a RC model.

Simon Chaddock03/02/2015 18:12:57
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5738 forum posts
3034 photos

Erfolg

I suspect the CofG is very close to being unstable, particularly at low angles of attack.. You can see in the video just the slightest touch of up elevator produces a very pronounced pitch up yet at slow speed and higher angles of attack it is nothing like so 'twitchy'.

The tiny radius of the loop (and it was not even full up!) would also indicate a rearward CofG.

It was a similar problem on landing. The approach was reasonably constant but as it got close to the ground I expect I instinctively pulled back a touch and it ballooned up probably made worse by the ground effect on the Canberra's broad low aspect ratio wing.

Modifications under way to provide a new battery position & hatch much nearer the nose.

Battery hatch mod1

The battery lead will have to be extended and then the old hatch can be sheeted over maybe leaving just a small hatch over the radio just in case it has to be rebound. wink 2 On 35meg crystal sets I was quite happy to completely build in the rx!

john stones 103/02/2015 18:22:50
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11600 forum posts
1517 photos

Looks to fly o.k. to me Simon, like you say elevator seems sensitive

John

Erfolg03/02/2015 18:35:18
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11781 forum posts
1340 photos

You could have always have tried strapping some lead on, in various amounts to see what happens.

A rearward CG is always a mistake. When I restarted modelling (with electric gliders), I initially tried to fly my models with a rearward CG, (33%) to avoid any lead ballast, as I knew the models had already gained a little wiight. A bad error, as the models would be unstable in pitch with the slightest disturbance.

I now fly with the CG no further back than 30%, makes all the difference.

I have had something similar, although not on the same scale, when trying to fly to near the stall, when landing, trying to stop it in the air, a little more speed, no problem. Although in my case, the period of one cycle a lot longer, relatively easily killed with a dash of down and adopting a "S" type approach.

Although, you seemed quite fast, in the approach, so probably different. I think the CG move will make all the difference.

Simon Chaddock08/02/2015 13:06:49
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5738 forum posts
3034 photos

The revised battery position.

Battery hatch mod2.Just a long thin 'slot' for the battery that is a good 2" (50mm) further forward.

There is a small hatch over the radio for re-binding if required.

The revised CofG certainly improved the flight characteristics considerably enough to give confidence for so low passes for the camera..

It is still pretty 'twitchy' on the elevator to the point where it seems to want to pitch up or down significantly with even the slightest elevator movement yet it is no worse when more movement is applied.

This got me wondering about the substantial scale elevator aerodynamic balance and the effect it might be having on the rather flexible Depron elevators.

With the new forward CofG it is flying with the elevators exactly 'neutral' whereas before they were significantly down. Does this now mean that with the slightest elevator input the aerodynamic balance was twisting the outer part of the producing a stronger effect than the actual input from the control horn at the elevator root?

I could build new stiffer elevators but the simple test is to simply cut off and fix the aerodynamic portion of the elevator directly to the tail plane.

Elevator tip mod No longer scale but if it has the desired effect (but too foggy at the moment to fly) then it will be worth building new stiffer elevators.

Simon Chaddock10/02/2015 15:05:33
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5738 forum posts
3034 photos

As I hoped the revised elevator has really made a difference to the handling. It now flies really smoothly especially with the elevator low rate set at 80%.

An edited video of this morning flight in cold, damp but almost still conditions.

The 3 axis gyro was not switched on.
Just a bit of paint touch up and its done!
Colin Leighfield10/02/2015 15:27:47
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6001 forum posts
2504 photos

Excellent Simon.

Ian10110/02/2015 22:03:36
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226 forum posts
323 photos

Yes, excellent. Looks like it flies really well now you have sorted it.

The way you build is fascinating and very educational.

Ian

Edited By Ian101 on 10/02/2015 22:04:08

Simon Chaddock10/02/2015 22:29:37
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5738 forum posts
3034 photos

Thanks for the kind words.

In truth I am rather embarrassed as when I put the Canberra's figures into a CofG calculator the suggested position is more or less exactly where I currently have it!.blush

I could have saved myself quite a bit of bother! wink 2

chris Ibbotson11/02/2015 01:00:11
72 forum posts
434 photos

Simon,

I've being following your build with interest. Your videos are a great testament to you and your diagnosis and correction of the flying qualities of the aircraft are superb.

As you know I am in the process of building a 74" depron (1/10th scale) Canberra B2 (on hold due to radical surgery on my leg, about 3 months).

I have a question to ask if you don't mind.

Do you put your "twitchy" Canberra (forget C/G) down to a "flexible" depron elevator that you built or do you advocate adapting/converting the elevator as you did?

Thank you for a fantastic build and looking at the last video she flies like a dream.

Regards ,

Chris

Jim Stewart11/02/2015 08:23:52
13 forum posts
22 photos

Excellent build!

Makes my 6 mm depron efforts look agricultural!

Can I ask what glues and paint you used? Also, was there any preparation apart from rubbing down?

Would like to try something a little less ambitious for a first scale type.

Cheers

Jim

Simon Chaddock11/02/2015 14:00:01
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5738 forum posts
3034 photos

Chris

One of the penalties (and benefits!) of Depron is its flexibility so a single thickness 'plank' as a moveable control surface is bound to flex a bit if driven from one end and even more so if there is an aerodynamic balance at the other.

With my very light planes I have no qualms about using small servos and relatively flexible control surfaces as a way of limiting the maximum stresses that can be imposed on the airframe - almost the equivalent of the rising stick forces with speed physically limiting how many 'g' a pilot can pull. wink 2

In the case of my small Canberra I will probably leave the elevator as a 'strip' without the scale counter balance but on a larger plane I would stick to scale for appearance if for nothing else although on both my rather larger Skyray and FD2 I have removed the counterbalances because as belly landers the counterbalance tips kept getting damaged.

Jim

The paint is nothing more than household emulsion (match pots). Homebase Dove Grey and Black Magic in the case of the Canberra. The semi gloss finish comes from a light coat of spray Simonix Clear Acrylic Laquer although this has to be applied very sparingly in several coats as a thick 'wet' layer will penetrate the paint and effect the Depron.

Sanding Depron is a mixed blessing as once you remove its 'skin' the surface is very porous and needs filling and/or coats of paint to give the same surface finish as bare Depron. It is all too easy to 'fill and sand' only to find you have exposed bit more underlying Depron in the process!

The really important aspect is UHU POR although an strong glue is very 'rubbery' so is difficult to sand and doing so tends it tends damage the surrounding Depron more than the POR!

To avoid this on the Canberra I stuck each plank to the formers with POR but used thick PVA (which dries hard and can be sanded) to stick each to its neighbour.

Obviously if the whole structure is covered in something like brown paper as Tony does this problem disappears although there is a modest weight penalty.

If you pick a suitable plane with little double curvature building true scale in Depron can fairly trouble free.

As a example my 40" all Depron Super Cub has one piece skins for the top and bottom wing surfaces. The tail feathers are flat, as they are in the full size, and the fuselage is basically a hollow box built up from 6 sheets over formers.

Simon Chaddock23/02/2020 17:57:20
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5738 forum posts
3034 photos

My B2 Canberra came out at 246 g although to be honest not sub 250 by design, in fact the sub 250 g class was not an issue when I built it in 2014. smile o

With tiny 35 mm EDFs I knew it was going to be short on thrust so one possibility was to build a Martin RB57D. It still was a Canberra but had a considerably increased wing span. With a lower wing loading the hope was it would fly slower and thus use a bit less power. In the end I stuck with the standard Canberra wing.

Now the 250 g class has meaning I wondered if I revisited the big wing span could it still keep within the weight limit? I like a challenge.

This compares the original Canberra wing against the RB57D.

rb-57d split

Of course this was not the ultimate big wing the RB57H went even further but only the fuselage remained as the tail plane & fin were significantly revised and with completely different engines.

Rather than build a new Canberra I wanted to do a 'Frankenstein' and simply remove the old and add the extended outer wing panels.

Having read through this thread it shows the fuselage nose has been significantly rebuilt three times so a complete new RB57D nose, with a single seat cockpit, might actually save a few grams.

The original B2 wing build plan.

B2 build plan By a bit of judicious 'cut & paste' the RB57 wing build plan.

B57D build plan

I have cheated a bit and made the ailerons a bit wider and longer than true scale.

To make life easier I printed out a set of rib 'masters' that would act as guides when cutting out the 2mm Depron ribs.

Rib masters

Really a bit of overkill as there are only 2 ribs required of each size! They are a true scale symmetric section.

I built the original wing using a rather odd technique, build the D box section first and then add the rest of the structure onto the back of it 'free hand'. smile o

The D box has 4 surfaces, top, bottom front and back with 7 half ribs inside all in 2 mm Depron.

D box spar 1

The first D box spar complete.

D box spar 2

Remarkably stiff both in bending and torsion. It weighs just 6.8 g.

Next is the tricky bit, turning it into a wing. wink 2

Edited By Simon Chaddock on 23/02/2020 17:59:32

Simon Chaddock24/02/2020 20:45:57
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5738 forum posts
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The RH B57D RH outer wing panel.

Outer wing 1

I have cheated just a bit and made the aileron a bit bitter than scale.

In this state it weighs 10.1 g. Now to do the same for the other wing D box.

Before it can be tissue covered the ultra micro 2.1 g servos will have to be ;extracted' from the old Canberra wings.

Simon Chaddock25/02/2020 14:24:50
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5738 forum posts
3034 photos

Moving on the extended wings against the original B2.

Outer wing 2

The additional diagonal bracing (2mm sq Depron) is to resist the effect of the shrunk tissue.

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