RBC Dornier 335

[Erfolg]

I have been looking more carefully at the rear moulding as supplied, and have come to the conclusion, it deviates from scale, noticeably. It is the sort of thing that passes me by, that is normally, not this time.

The full size aircraft had side opening doors for radiator cooling air. The kit omits these, but has potentially a large (ish) opening where the TE would be.

I am now thinking of opening this up for a cooling air outlet, then creating reverse side openings, to let air in.

As I am not a rivet counter, I can live with this non scale aberration, to scale aficionados.

I have noted a discrepancy with respect to the nose moulding, a radiator on the real thing. Again, practicalities matter more than absolute scale.

As it has now started raining, I will content myself in marking out where all the various holes should go. Then wait for a good day, to go outside to work on the GRP.

In the mean time I am still pondering suitable motors.

[Erfolg]

I have been trawling through the HK site looking for suitable motors. They seem to have nothing remotely in the sizes I use. Although I have purchased one that may be OK. My present plan is to install motors that could do the job, although not as ideal as I would like, with a view to replacement in the future. To that end my motor fixings need to be easily replaced.

I have been waiting months for HK to restock, I suspect that motors are either in short supply in China, or that motors are not a high priority for HK, or there maybe a cash flow issue, where money is being directed to the highest margin and sales items.

In the mean time I am dealing with the things that appear to be wrong with the kit, or maybe how I have built it.

The first bit that seemed wrong was the cockpit area. Their was a curious bulge by the cockpit. I have poured over numerous pictures, my trusty Airfix model, on the full size it does not appear to be there. So I marked the line which appears to be near enough correct to my eye.

Then just removed the offending material and re glued.

I will now sit down and consider what should be my next logical things to do and the relationship or order. I have a feeling that much of the bare airframe is now done, but a lot of time consuming things need to identified and done. In my case not made easier by not always remembering what I have done and why, for the later stages of building. It all seems so logical at the time.

[Erfolg]

This turning out to be a slow build. The lack of HK stock being one of the issues.

I have decided to go a slightly different way than intended and that is to use a motor combination that i have used previously. One of the motors coming from a TH Clean Sweep (which I crashed).

These are high torque inrunners of relatively low Kv.

It was only after some lazy thinking, when it suddenly dawned on me, that I could have bent the motor shaft. On this type of motor, the shaft is not replaceable. Sticking on the original spinner on i could see that it was running out. But was it the shaft or the spinner? I have no fancy equipment that many model engineers have in their workshop, only some basic stuff. So I have to improvise.

In this case some vee blocks to hold the motor, a DTI mounted on my scribing block. Everything was moving, so a couple of pieces of lead to keep stuff in place. There is a little run out, of a couple of thou, which is possibly the prop adapter. Running on the shaft, there appeared to be none, although the flat on the shaft complicated things, hence the adapter.

To mount the motor is less simple than with an outrunner, although I have two options I am considering. Both are not straight forward. Both use approx, the same stuff

more work is required, although I have some confidence I can get it to work. Outrunners would be so much easier. This set up has ruined my plan of how to actuate the rudders. I think it will now be visually messy.

I will use the same motor as the pattern to make the front mounting, whilst I wait for the HK motor

Edited By Erfolg on 18/03/2020 02:06:01

[alan p]

Cincinnati machine tools a good old firm. Blast from the past

[Erfolg]

After consideration of the planned method of mounting the rear motor, I came to the conclusion, although I believed I could make it work, with careful setting up and gluing, it would be clunky. I was not very happy.

Luckily I woke up, the next morning with a possible solution.

Which is above. it works quite well, still more work to finish, including the purchase of a couple of spinners.

I intend installing the front motor in a similar way, although, the installation will be a little better, in that the motor assembly will not be cantilevered or overhung to the same degree. The only problem is that I am in the age group of self isolation, so cannot go out and buy an endcap, to modify.

[Erfolg]

It probably seems that I have not been doing anything with this model. I have but it has been slow going.

The first thing I noticed that the rear cowl did not fit as well as even I like.Rectifying the issue took some time and work, Then I noticed that the thrust line may not have been as ideal as is necessary. Yet more time with the cowl. The thrust line is now pretty much along the centre line. Unfortunate the cowl is less than a perfect fit, it will have to do.

Next I noticed that the fins were not quite at 90 degrees to the tailplanes. Yet more work. To get the back end within acceptable limits seems to ba an iterative process, which is beyond me in single operations.

I have finally glassed the body with with 1.5 oz cloth. The fins, tailplane in 1/2 oz cloth. Does any one know the metric equivalent, as i will need to buy some more for the future. I used Ronsons Hardglaze as the varnish adhesive.

I am now waiting a motor for the back, now I have paid PO handling fee, plus about £4 in vat. It just occurred to me that most of the vat is the PO handling fee, as the motor was £16. I could not get what I wanted in the UK.

I will make a few bits of trims, then probably put it to one side, and work on it in bits, as we are now getting to the fiddly, slow bits.

[Erfolg]

It has been getting on for 9 months since I made any material progress with this model. Why is the question that i have asked myself?

There is a set of reasons, the first is that I needed some spinners a lot bigger than i had available. This meant ordering some. The second that Covid had just become a reality, rather than something some distance away, also that the disruption would compromise modeling supplies. In short my spinners were on back order.

Whilst waiting I set about building an Aeronca Sedan. This became along the lines of the Mercury kit model, which I have a kit. This ended up as a redraw, putting the kit to one side. The original intention was to build a kit which I had, and still have. Then I have built a KK Mermaid a quick build boat.

So when the spinners finally arrived, I finished what I had started.

The next big surprise, that all the work I had done to install the motors was for nought. The differences between my normal spinners and these and how I would mount them is totally different. I have started a revision process, where the front motor is about 60-80% done.

Here are some random photos of where I am at.

For the first time in 60 years I used a scribing block ,and then a DTI which I have not used above 4 times in the same period. I can say with honesty, I had to think hard on how to use the equipment effectively and also how to jury rig the bits and pieces i have.

Hopefully i will press on now.

Plus finally finish many of the models I have put to one side needing detail finishing, before starting something else.

[Erfolg]

After such a long time since working (if that is what it can be described as) on the model, I no longer remember with any clarity what the next steps were going to be. The spinners do give a clue of what was planned, assuming that all the jobs I intended undertaking whilst awaiting there arrival have been completed.

On that basis I continued on the rear motor set up.

I have made so many motor tubes (now), that making a new one was not such a time consuming or fraught job. The first picture shows the tube prior to it being shortened.

You will probably notice there are some quite big gaps between the spinner and the cowl in both installations. This is quite deliberate as these inrunners need to allow air from the integral fan to exhaust, and be drawn in.

I am now wondering why I picked such a heavy motor for the rear assembly as I do not want a CG issue, requiring a Cathedral roof to remedy. These two motors are quite powerful compared to the original motors used, which appear to be HET, although some of the photos seem to show bigger motors.

Anyhow I am now thinking about the linkages to the rear tail surfaces, as again the photos show a very complicated, almost Heath Robinson installation, to keep the back from looking cluttered. I think my model will look cluttered.

[Martin Harris - Moderator]

Interesting project Erf. I assume you'll be turning the prop round for flight?

[Murat Kece 1]

You are progressing very well. I am sure it will be a great plane. I hope this gives you further inspiration.. A model from Americas..

Edited By Murat Kece 1 on 20/01/2021 15:48:41

[Erfolg]

Martin

I am glad you have pointed out what I have done, I hope that turning the prop around causes no problem. It could as the prop has an insert for centering, which will no longer be against the collet datum face. I will see.

You would be surprised how many times I have been told that the prop is wrong on my small 335, not getting it operates as a pusher , initially.

[Erfolg]

It is 4 years since I did anything on the 335. Why, hmm, it was the exhaust stacks. The RBC plan does not show location or the detail necessary to produce them.

 

I have allowed myself to become distracted on other new models, just now I had started building a He 162, designed a Douglas X3 all from Depron. I have become diapointed with the Depron I now have, finding it a pain and of poor quality (from a modelling perspective). So these went on the back burner.

 

I then started to think about all the models I have not finished for a whole variety of reasons. I the case of the Dornier it was a lack of information of the real aircraft. I have seen the full size, when in Munich, of course I did not note the exhaust or take any pictures. It was the size of the thing, a rather, or is that a vey large fighter. More the size of the Hampden bomber (the one at Cosford). I now have a whole pile of books with details of aircraft in them. 

 

It seems that unlike a Spitfire the exhaust stacks do not stick out very much from the body. That there is an internal shroud or baffle that separate the pipes from the the rest of the internals. A external cover then seals the exhaust, with the pipes barely sticking out. I had assumed that pipes were round, but they transition into a rectangle.

 

Eventually I sketched up what was wanted, only to realise that I did not now how to 3d design the things. Rather than seek perfection, I have drawn up as near as I can manage the items and then printed them.

 

Installing them has not been a two minute job of sticking them on the outside. It is about letting the items in.

 

My next job is the Fuel injection inlet. Yet again, a pretty much bulky item.

 

Everything else will just have to wait.

 

 

[Tom Gaskin 1]

If this flies as well as my Black Horse version you will be well pleased with it.

 

Tom