RBC Dornier 335

[Erfolg]

This is a model that has been on the go now since New Year 2019. Being a kit I thought it would be a straight forward build. The reality is that for me it has been a struggle. To the extent that it seems that any excuse is used to put it to one side. In essence it has taxed my build experience and also my skills.

There are not many photos of the build, primarily as the kit comes with a CD with hundreds of pictures. There are some issues in that the pictures and the plan and kit contents do differ in places. On reflection I can understand why. I guess that two of the model was built, the single seater and the double seat tandem with the high second cockpit.

obviously the wing. The plan calls for pneumatic UC, I am using electric. On reflection I should have beefed up the UC mounting, as it seems a bit light weight to me. It is probably my landings that require a really robust UC.

This shows the wing mounted to the body. It is worth noting that the body is built on a light plate crutch. I drew a line along the bits that make up this crutch, so as to build it straight, otherwise it would probably been a banana.

I had another problem in that the body is planked with sheets. The tension from this process has resulted in a slight bend along the crutch od about 1/16" from end to end.

The upper part of the body now needed to be added.

Upper body being added.

Adding the tailplane has been a nightmare for me. I have used a 1 meter rule to establish a datum line relative to the wing and body. For me this has really been a struggle, in that I have pondered for hours how to get the "Z" axis od the tailplane in the correct (as near as , dammit) that I can achieve. Again the steel rule along the CL of the body and and a 90 degree set square was used. All sounds dead easy, for me a struggle, with much internal debate, as to how effective this process has been and so on.

The tailplanes have been temporarily joined to aid alignment, in addition to the datum lines.

I have just glued the tailplanes into position and I am waiting for them to set. The bits of extrusions have been used to ensure (as near as I can achieve, with aging eye sight) that they are both parallel to each other as well as the various datum lines.

Perhaps unsurprisingly that my brace did allow about a degree or so relative movement. I just eased them into alignment.

I can imagine for the Danny Fentons and Gordon Whiteheads of this world it is a easy peasy build. For me a step change from the PM and TH. everything done and sorted for you type of build.

MY next issues revolve around both the elevator and rudder drives, as there are two very different approaches from the disc to the drawing,. I am guessing that the disc version with its great complexity, had issues with respect to installation and operation. The drawing version on the other hand lacks detail, beyond a lot of snakes are involved.

You may wonder why I am building a second bigger 335, it is like many things. The first is great, bigger will be much better. As one who has built 4 versions of a FW 190 and its variants, you get sucked into building a model which initially you do not aspire to build at all.

[Colin Leighfield]

That’s a great choice Erfolg, I share your interest. I’m sure your careful approach will pay dividends in the result.

[Erfolg]

Colin, I have another mistake, by me. I was viewing the CD pictures, which contains hundreds of images of the build. The pictures relate to at least 2 models, probably three. I found additional discrepancies between my kit and the photos, where the rear motor is mounted, yet the real, OMG moment, is when I realised that my tailplane differed from the CD. A quick look at the drawing supplied confirmed that the plan of the tailplane is not shown on the drawing.

So tomorrow, now having located the additional bits, I will stick the bits on, that at present are missing.

Having a partial drawing, does potentially make life a bit more difficult. I hope that I would have spotted that there were additional bits with a plan view, rather than just a side view of the body.

Now I have the tailplane in place, one of the intended solutions to driving/controlling the elevators (being in two halves, is probably not practical, it is the width of the rear Fuz that complicates things a bit and the mounting of a pusher motor. c'est la vie

This is going to be an even slower build going forward than what has been done.

[Colin Leighfield]

You can’t be slower than me. On a project like this though you need time to think it through. I’ve always thought that the general dimensions and design of the Pfeil combined with the torque reaction cancelling effects of the contra rotating motors make it a perfect subject for a scale model. Could be your “piece de resistance”! (Stuck Widerstand?) I’m happy to wait. The Seafang is still sitting in the shed ready to go again when I get around to it. I kicked that off in 2015!

[Erfolg]

I have been undertaking some work on the tail area.

Although pretty accurate in the parts supplied, it has been necessary to make some adjustments, to get the fins in the right places.

In the shadowy light I can see that the side of the cockpit probably needs some work, to get the side profile to follow the same line as the rest. I am not anticipating that this will require a lot of adjustment, although, the famous last words go along a similar thread.

I will now turn my attention to the underside of the wing, where it blends with the body, as part of the underside of the body.

Perhaps a little disturbingly, I still seem to have quite a bit of wood in the kit box.

[GeeW]

Erfolg

Sorry for the thread drift, but what is the yellow model in the above image with '45' on side of the fuselage?

Regards

Gordon

[Piers Bowlan]

Miss Demeanour (semi scale Cassutt racer) a smaller version of Miss Deeds also designed by Peter Miller, here.

Edited By Piers Bowlan on 17/12/2019 20:24:06

[Trevor Crook]

Keep us posted Erf. What size is it?

I built an RBC Harvard a few years ago and while the quality of the wood provided was excellent, the plan and instructions left a lot to be desired, and like you I struggled. Probably why nearly all of my current warbird fleet are foamies!

[Erfolg]

GeeW

Piers is correct, it flies well. Flying even better is the PM 1/4 scale semi Scale Cassutt.

This version has been built with a pretty scale width than the PM plan, which is a bit to narrow for my liking. Which is about aesthetics and just as importantly sticking stuff, like Lipos inside. The big version has now been flown by two of the clubs top flyers, who have been really impressed with the model. Both into aerobatics, where one also flies a wide variety of scale models.

This guy has also flown now the Nitro Models Do 335, which surprised him with its good handling.

Trevor the RBC kit is 1.4m span. Which is 55" . Perhaps unusual for many military planes the chord is very broad, low aspect ratio. I knew that there were many proposals and a few sub sets built, I did not know that a large span version did get built, as a one of, I think by Heinkel. I was really surprised at that. If the plan was better I almost certainly would already be into building one.

[Erfolg]

GeeW

Perhaps I should mention, that the PM small Cassutt was drawn as an IC model. Both myself and a Scandinavian built them as electric. This did require some changes from the original plan, in detail. Both of us worked hard to reduce the weight, I lost. For me it was not the easiest of conversions, if I were to build another I would do it differently.

In the case of the 1/4 scale, I built my model from a plan that PM sent for electric. I do not remember what was published in RCM&E. All I can say it went together without a hitch. It is a straight forward, adhering to proven methods etc. No decisions need to be made, unless you want to change things. As with any PM model, they both cut the mustard.

[Don Fry]

A bit of an historical query, but is there a reason why a very late model piston fighter still has a canopy like early and prewar monoplane fighters, rather than bubble tops as the rest of the world had moved to. I remember that the change to bubble tops was pilot driven, to improve visibility, and I always thought the Germans were good at design consultation, if not in tactical use.

And that's looking very nice Erf. Before you kick yourself, just remember what's out of sight on the finished job didn't happen.

[Erfolg]

I cannot answer the question directly. Although the aircraft did not approach service until very late in WW2, its history as a project (something near to the 335) goes back before WW2 started. Indeed its role as a concept went through many iterations, put forward in many guises, to meet what ever tender specification that the Luftministerium issued. In addition to unsolicited submission. For dornier the push me pull you or tandem drive goes back to pretty much WW1. I believe that the UK/USA/French/Italian alliances had at least one tandem engine aircraft.

It is a while since I read the history of this aircraft, several years back now.

Perhaps one aspect not fully appreciated, is that Germanys manufacturing capabilities, started out limited and for some things remained capability limited until the end (WW 2). I suspect that blown cockpits was one. Raw materials were yet another area of limited availability. Then as WW 2 progressed, person power in all areas reduced.

It is probably not appreciated by many that, that reparations were being paid by the Germans in both money and goods into the thirties, 1931 I believe. France invaded the Rhur about 1923 to cease what it said was owed. Then came the depression. Although the image is often portrayed as a technological and manufacturing giant, the reality was that when WW2 started the general capabilities were limited.

Cor, I amazed there was even a cockpit Canopy.

[Trevor Crook]

Erf, I forgot to mention in my somewhat negative report of the RBC Harvard that it ended up flying rather well. I'm sure your 335 will too. One of the many, many types flown by "Winkle" Brown. I gather the ejection sequence was rather perilous.

[Erfolg]

I have the book Wings of the Luftwaffe, where a description of the ejection sequence is described. It does read rather long winded.

I have another more recent book, with descriptions from 335 test pilots, where the sequence could be truncated. I will look for the book and remind myself as to what it actually says.

I have seen a German ejection seat, in the Deutsche museum, compared to a Martin Baker seat, it is extremely basic. It was fitted to a lot more aircraft than i was aware. Again there are a number of accounts of it being used successfully. However it was a very low powered arrangement. The other aspect is that many pilots were seriously injured bailing out, using the then conventional methods, often striking some part of the airframe. Again, part of the German problem was that they were also running out of pilots, even inexperienced ones, On that basis the ejection seat was an improvement.

As ever, there were and ejection seats and ejection seats. The German one could well be the first in operational use, however limited its capability seems.

I must admit that it seems very strange to me that a lot more is now known about the 335, than when William Green wrote about it. Now most of, if not all, of the Engineers and pilots etc., are either dead or have memories that are not necessarily reliable. I am guessing that the written stories and images were out there, of the procurement, design, manufacture, piloting and operation, they just were not collated and made into a well rounded coherent story.

[Erfolg]

This is apparently the ejection seat fitted to the 335, He 162, He 219 (Uhu), He 280. . One of the He 280 test pilots, Helmut Schenk, became the first person to escape from a stricken aircraft with an ejection seat on 13 January 1942 after his control surfaces iced up and became inoperative. The German system used propellant cartridges to propel the chair out of the aircraft, via pistons within chambers built into the chair.

Next to it by memory is an early Martin Baker Seat,

Next to that an early USA ejector Seat, from I think Convair, using a rocket motor, to avoid damaging the pilots spine, as with the German system and the early MB system.

Although I gather there were lots of ejector systems before, and simultaneously to all three.

[Max Z]

Seen at a big scale meeting in La Ferté-Alais, France in 2005. I love the scene, set in the period after cessation of the hostilities, of a german pilot explaining the workings of a 335 to his collegue/former adversary pilot:

[Erfolg]

I wonder why it was not based on the Munich Deutsche Museum example, in that it was the only one left. Now it is in the Smithsonian I am told. Opportunity to take photos etc.

One thing is for certain it is a very big aircraft as a fighter for that period. Bigger probably than the Hampden in Cosford Museum (being renovated).

Apparently some of the size is a function of standing patrol/action duration. Where Spitfires and 109 even with drop tanks were more limited. Another aspect is the weapon load and fire power, per sec. Not as good (weight per sec) as a Me 263, but not far short

Edited By Erfolg on 19/12/2019 14:53:18

Edited By Erfolg on 19/12/2019 14:53:58

[Erfolg]

A bit more progress has been made. Although over the Christmas period I have been busy and also ill. It is the ill bit that i noted the most.

probably the most obvious things are the wing tips, which are "Blue Foam" rather than the very thin vacuum formed mouldings, which are quite thin. I suspect they would have been a bit flimsy for my taste.

The other thing done is the wing underbody fairing. The bits in the kit would have produced a bit of a pregnant look. I used these bits as templates, then cut down some new ones I made, finished of by planking, 3 planks I think.

My next job will be to recontour around the cockpit side, to remove the curious bulges, as I am sure that the full sized ones, did mot have it.

Perhaps the bit I am a bit concerned about is the nose and tail mouldings, these are again a very thin plastic. It is probably +30-40 years since i have tried to make a female mould. The other issue is that Epoxy resin is not as easily obtained as it was in the day, so yet another issue.

[Erfolg]

Today I decided that my next stage would be the purchase of two motors for the 335.

I trawled through both my file of equipment specs i have bought and the book with the results of testing. For some one who thought they had recoded everything carefully and logically filed the test results. Examination seems to reveal a need to be more careful. I am guessing that changing the propellor has resulted in a spread of results, relative to power consumed.

Anyway the most consistent results seem to be from a Propdrive 35-42 motor, providing 700 w drawn. I also know from observation that this motor provides bags of flying umpf, with long flight times, being used in my PT19 and 1/4 scale cassutt.

There is a fly in the ointment, they are out of stock at HK. A cursory glance at the D3548 types, are also out of stock. What is going on at HK?

I will now continue with producing some moulds for the cowlings at the front and back.

[BARRY Killick]

Very nice progress on the 335. We have a modeler over here working on a 60" lightweight balsa version, hopefully to be "cut" by Manzano later this year and I want !

Re RBC kits, have built their Skyray and P-80 and were both very frustrating builds, it always seemed like two steps forward and one backward and invariably I would find a major error that caused a lot of backtracking. I have their F-84 still in the box -- not sure if I want to go thru another one though !

Not sure I am good with having to make my own cowlings etc when paying for a full kit.

Keep plugging along the finish line will suddenly appear.

[Erfolg]

In defense of RBC, I suspect that kits produced are small in number. I also guess that not many have been built by RBC. RBC probably supply models that are not mainstream, a bit quirky, they are far more interesting.

It would not surprise me that this is just one guy, who has to design, build the prototype, cut the kit, source all of the kit materials, package the kit, deal with the accounts (cash flow) and tax.

By ARTF standards, the total build cost is far higher.

As for the 335, it is bigger than i thought. It is worth doing, although my model will not be as scale and detailed as the French example. I just feel it will fly, probably quite well, look good in the air, to my eye.

The down side is, i do wish i had beefed up the UC mounting, as our field imparts a bit of pounding.

I do hope you find the build interesting, even my cock ups, I always manage a few.

[Erfolg]

Whilst I wait for suitable motors to become available I have turned my attention to the nose and tail mouldings where the motors will go.

The supplied moulding unfortunately are very flimsy, akin to those often found in some of the early cheap far eastern imported kits. Perhaps they could be of even poorer quality. Certainly the worst aspect of this kit.

What to do about it? In the past i have made similar cowlings by building up a nose area.

Both of the cowls above were made by slightly different methods, they all work. All involve a layers of balsa wound onto formers then put in a drill an slowly sanded down, as in a crude cylindrical grinder.

In this case I have some mouldings which are a little less than I would really like. In this case I think I will give another method i have used in the past. Which is to use the mouldings as formers to create a mould. In the past i used Plaster of Paris, now finding a reasonable art shop requires me to travel. This time I decided to use finishing plaster as used on walls, I have used it previously for my grandkids school projects. The down side it does not set as fast, and probably uses more water. meaning it will be weeks before it is approaching dry, during the intervening time it's weak.

The mouldings are so flimsy that I need to support them to make them concentric/round.

I cut out corrugated cardboard discs which i inserted into the moulds whilst pouring, with internal weights to stop the mouldings floating.

I am not to concerned with the nose cone as it appears to be reasonably round and of the right shape. The rear cowling is another matter. I am not sure it is near enough to fit well, where its flimsy properties would possibly allow it to be pulled into shape. I also know i cannot mould this with to a heavy lay up, as weight at the back, has most unfortunate CG consequences.

In the case of the rear, I will try cutting and filing to get a good shape. If all else fails it will be a balsa and ply built up structure.

In the next week or so i will clean the inside of the mould out, then start wax polishing the inside. I the past i have found that 6 coats are over kill but work. I still have some old blue moulding PVA which I will try.

My intention has now moved to Polyester Resin, as I can buy a small quantity from Halfords.

 

Edited By Erfolg on 22/01/2020 12:32:33

[Erfolg]

The project had ground to a halt due to a number of circumstances, HK not having in stock the motors that I wanted. I have now forgotten which ones and why, it is an age thing. Then I have had one cold after another, that is three to date. A holiday in Lanzerote, glad I got back in the nick of time. Looking after a house rabbit, then a delinquent dog, that needed a lot of walking and of course Christmas.

In between I did what I could.

I also posted a number of threads with respect to moulding cowlings. From which I did get useful information, which to a large extent decided what I did.

In the dim and distant past, I have been involved in various GRP work. In addition in my early twenties I worked in a commercial plastic moulding company, that did injection, transfer, dough, and some steam moulding. Nearly every type of polymer you could think of was mixed, bought in etc. Of course I took a lot less notice than I thought. As a hobbyist I had some specialist tools for the stuff I did.

Today, the tools have gone, what I knew, is now forgotten.

I knew |I needed better cowlings than have been supplied with the kit, so the following is what I did.

This is a pattern for something

A length of hobby related cloth I purchased at 200 g per ft^2.

I pre cut all of the laminations I wanted

The mouldings as they have been pulled.

I may have described how I made the moulds, but here is a repeat. I made up a box to put the RBC cowls into. I then purchased some time expired plaster from B&Q. Filled the cavity and weighted the cowls down to prevent any lifting. Binned 90% of the plaster.

I then waxed the the moulds 6 times.

I then painted with blue PVA, the type used in moulding. It is 40 years old. Still works.

Debated if to used polyester or epoxy resin. I was convinced that Epoxy would be better. I purchased 500ml set. Ordering was a trial, then the order went missing. It was not Easy composites fault.

I found that what I once found to be no big deal, was for an old man, without any recent practice and remembered relevant knowledge.

What I learnt was (as recommended on another thread) weighing is much preferred to volumetric measuring. That I work a lot slower than I thought. That 60 ml goes of faster than i could work, approx 20 minutes. That for the cowling that 26 ml was just about ok. That the flexibility of Epoxy allowed me to ease the mouldings out of the mould, where with polyester it is far to stiff, for a similar moulding.

In the end I got there, but, golly gosh, it was a close thing a number of times.

[Erfolg]

I have now done a little bit more, the emphasis on bit.

I do not like GRP mouldings with bits of random glass sticking out of them, as they are surprisingly prickly. On that basis I took some measurements from the supplied drawing and set about creating a cutting line.

I taped a little masking tape in the area where the cut had to be made. Fortunately I have my fathers old scribing block. Again it just shows, do not throw out anything, even though you think you will not use it. I taped a pencil to the scriber as it marks more clearly than the scriber, with sufficient accuracy for what i need or can work to.

I was a little surprised and disappointed in that the rear cowl has virtually no waste on it.

I do not like GRP dust either so I donned my gardening gloves, coat, shoes and hat and headed outside. There I cut the waste of using a junior hacksaw. I did take a very fine (number of teeth) hacksaw blade, although it was not needed.

First stage now done.

Before I move on, it is time to clean and tidy my modeling room. Then cogitate how to mount the cowls, consider motor cooling. Any one who saw my PM 1/4 scale Cassutt will be aware what inadequate cooling ( two blanked of galleries) can achieve.

Also this week I will consider the motor issue.

[Erfolg]

After a little examination I found a problem with rear cowl. The problem being that the length of the cowl incorporated a little sweep upwards at the top and the bottom.

A little more scrutiny of the drawing indicated that the cowl is supposed to slip over the rear end of the Fuz. That may happen with the flimsy moulding supplied. With my light weight moulding that is is not going to happen, as it is to stiff, rigid. The other issue is that the supplied mould does not match well with rear bulkhead.

My solution is to lay up more laminations inside the problem areas, then sand the outer surfaces to shape.

 

To mount the front cowl I have made up a inner ring of light ply which then has a few layers of glass cloth layed up on top. When I have satisfactorily centred the cowl I will then tack the two bits together,

I ideally now need some motors. I was hoping to use Propdrive 35-42 at the front and a Turnigy D3536/6 at the rear (being fractionally lighter, although I am not sure the difference really matters). Both are out of stock. I considered a Turnigy 480L V-Spec, which is on offer, although due to a 23p excess over £15, could cost me over an additional £10, as has happened previously for 50p.

So I will now start looking for alternative motors which provide something like 1.3 kg static thrust (approx 2.5 kg combined).

Edited By Erfolg on 08/03/2020 14:31:06