Mounting Rapiers in Models
Generally, our 'one shot' Rapier motors are inserted into paper/cardboard tubes attached to our models.
These mounts are simple and effective, and can be commercially available, or 'own rolled'. In either case they have a wire retaining clip at one end and a balsa plug the other . These can be refined to resemble like 'weapons pods' beneath a profile model and really look quite authentic:
Above: a motor mount is ready to be glued to my profile Corsair II. Note the two short lengths of cocktail sticks to key the mount in the fuselage and ensure (as far as possible) that the mount doesn't come off in a hard arrival. I've also rounded the nose and applied a couple of coats of grey enamel paint.
Above: the latest Corsair II with finished mount and motor in place. Note the foil protection and the thin metal thrust tab behind the motor Rapier exhaust is HOT!.
Rapier motors are these days quite reliable, much better than they were a couple of years ago, when duff motors were not uncommon. Nevertheless, burn-throughs, blow outs, whatever you like to call them, can still happen.
Below is my MiG-19 for L-1. It's a fine flyer and I'm very fond of it:
But this is what happened on its first flight:
OK, not too serious, and profile models are much more robust than a proper scale model, but even so it is upsetting.
More serious is what happened to my Hawker Hunter a few years ago:
Rapiers are pretty good these days, but one would hesitate to put one of the older motors we all have at the bottom of our flight boxes (or given to us by a generous rocketeer who has (alas) 'moved on') into our latest superscale creation.
As can be seen in the case of the MiG-19 and Hunter, card/paper motor mounts give little protection and allow the hot exhaust to quickly attack a precious model. Built up models are, as can be seen with the Hunter, more easily damaged.
So, is there a better way? Time for some thought ...
I have in my possession some genuine Jetex asbestos paper from many years ago:
Above :Jetex asbestos paper and a commercially available mounting tube for an L-2. The L-2 shown is used, and though scorched, it did not, I repeat not, burn through in fliight.
I wondered if a motor mount fashioned from asbestos would be more robust. I glued light 'Bank' paper to the asbestos with PVA glue, and wrapped it around the cardboard mount:
Above: rolled tube and motor.
Above: Asbestos/card motor mounts (or tubes) cut to size after drying overnight.. There are two thicknesses of asbestos paper next to the cardboard. Note the balsa plug and wire clip.
I was quite pleased with these and the asbestos only added a gram or so.
I then mounted one of the new mounts in my test rig:
Note I drilled a small hole in the Rapier L-2about an inch below the nozzle to ensure a 'blow-out'.
Now for the crucial experiment. I ignited the motor:
Above: we have ignition! The motor(which went first go) is giving a healthy 13 grams (a little under 1/2 oz) of thrust. Looking good ....
The flame then reached the drilled hole:
A case of, "Houston, we have a problem!
Above: Through the smoke you can see that the thrust dropped immediately as the flame came through the motor case. After a further couple of seconds, the blow torch-like exhaust seared through the motor mount. Not quite what I was hoping for ...
I let everything cool down:
Above: Here is the motor and mount at the end of the experiment. Glad I hadn't tried it in a model!
I was disappointed the asbestos burned through so quickly, but this is an extreme case, and in real life a Rapier a 'burn-through' is never this bad.
So the results are not clear. I'm inclined to believe asbestos can offer your precious model some protection from a duff motor. Asbestos, which these days has a bad reputation, is probaby not now the best material to use. Thin metal sheet I'm not sure is the answer - perhaps there is modern plastic out there which is better. Nomex, perhaps?
I'm open to suggestions!
The Jetex Dan Dare Spaceship
Were there any two names more evocative than 'Dan Dare' and Jetex' for the technically-minded 1950's schoolboy? I can't think of any.
Peter Cock of Wilmot Mansour (Jetex before it was taken over by Sebel) designed this shapely model in (I think)1953/54.
Above: Jetex Space ship on display, and on its fearsome spring-loaded launch pad. (Both photos from Mike Ingram's archive).
Above: One of Jetex's most brilliant designers was Peter Cock. This photo from the 1950's shows Peter at one of the many meetings where Jetex products were demonstrated.
Peter, seen above with his equally famous Interceptor, told me he built three prototypes of the Spaceship to make sure it worked properly.
The body was moulded balsa sheet, a feature of the Jetex 'Tailored' models. The scary plywood catapult was designed by Joe Mansour himself. All in all, it was a pretty complex model and an expensive kit (more than a year's pocket money) at the time. It was powered by the newly developed Jetex '50R':
As long as this was properly loaded with grooved pellets and a yard (1M) or so of fuse, it could deliver about 5 oz ) thrust (about 1.5N for up to 5 seconds.
This was enough to propel the spaceship to a couple of hundred feet before the spring-loaded catch opened and the parachute was ejected.
Above: The catch opens and (hopefully) the parachute comes out. In its review, the Aeromodeller was highly impressed with the quality of the kit, but thought it was one for 'experts only'. Eagle, as will be explained below,were not impressed. Or amused.
There is more about the Spaceship's history at:
When the Spaceship was first marketed, Jetex associated it with Dan Dare, the astronaut hero of that wondeful boys' comic at the post-war years, Eagle:
However, Eagle for some reason objected to the appropriation of Dan Dare, its 'Pilot of the future'. lawyers were called in, litigation was threatened and, not without great regret, all reference to DD was removed and Dan Dare had to be content, for the time being, with his Sondar-designed Anastasia. So the box most modellers associate with Peter Cock's wonderful creation looks like this:
Which is how it appears even in a recent AeroModeller. An original box has proved difficult to track down, so I was delighted to receive to receive high quality scans of a Dan Dare box from Robert England (thank you, Robert).
Robert's father had been a printer in the 1950's and had kept these test printings in his garage for over sixty years. They only came to light when Robert was clearing his father's house.The quality of these prints is amazing, here is Robert's scan of the original box top for comparison to the bowdlerised version above.
I am thrilled Robert's father (blessed be he!) thought to preserve these unique artefacts, and, calling upon all my skills in Paintshop pro, I have now prepared a montage from Robert's excellent scans:
Printed in glorious Technicolor and suitably mounted, this work of art will make a grand addition to any Jetex enthusiast's workshop. It can be printed (on quality photo pape)r at either A3 (recommended) or A4.
Please tell me if you would like a copy, which will only cost you only 5 GBP (cheap) to cover printing, and 3-6 GBP postage (expensive) depending on where you live.
Onwards and upwards!
Recent Jetex Articles for the Society of Antique Modellers
In a previous life, I published more than a hundred Jetex and Rapier-related articles in SAM (35) Speaks, the prestigious monthly journal of the Society of Antique Modellers in the UK (chapter 35).
Copies of these were available month by month on the Jetex.org website, and PDF copies were sent out by email to jet modellers all over the world.
I would also add that a data disc of all my 'Jetex' articles, from 2002 was put together, and is still available for a small fee.
Earlier this year I resumed writing articles about the UK 'small jet scene' and these have been published by the estimable Colin Hutchinson, the new editor of SAM (35) Speaks. The response to these has been quite favourable, so I am offering PDF's of my new scribblings to any interested modeller.
Here is the first page of the Spring 2015 article:
And here is a taster of last summer's offering:
There are two more, autumn and winter, articles in the pipeline.
My articles are of course UK centered, but I'm hoping to include more 'international' news via a wider distribution of these which will result in feedback from the many jet modellers overseas.
If you would like copies, please contact me with your email address. In time, I will compile a subscription list, and the latest 'Jetex and Rapier' can be sent out to all those on the list automatically.
Any comments about the articles, and contributions to future articles, are very welcome.
Mounting Rapiers in Models Part 2.
Intro: My previous blog on this subject was about the use of asbestos in a Rapier mount to see if this would prevent a model being damaged in the event of a Rapier case burn through. Experiments showed (you will remember) a mount with two thicknesses of asbestos proved ineffective.
The need for a robust motor mount was made even clearer when I tested a batch of Rapier what turned out to be L-2 LT motors:
Above: the thrust is adequate for a light model; however, there is a thrust spike towards the end of the (very nice 20 sec plus) burn time. The cases of two motors burned through at this point, with enough heat and flame to damage a model.
I wouldn't put one of these motors in a model, and certainly wouldn't provide them to even a brave modeller!
Following previous blog, I was contacted by Rob Mcconaghy, who suggested a ceramic or metal mount would resist the heat of Rapier propellant.
In the first instance, Bob offered to make some metal tubes of various aluminium alloys and one of stainless steel that I could test with Rapier L-1 and L-2 motors.
Rob was as good as his word, and a few days ago some beautiful tubes arrived by post:
Above: these alloy tubes are sized for L-1 and weigh only 0.6g. Those for L-2 were larger: those made of alloy weighing 0.9-1.2g, the stainless steel one weighed in at 2g.
And very beautifully machined they are too It almost seemed a pity to test them!
I first tested the stainless steel tube with a standard L-2. This had a small 1 mm hole drilled through the case to ensure a 'blow-out':
Above: We have ignition! The tube glowed red-orange but did not burn through and the model would have been protected.
I repeated the experiment with one of the suspect L-2 LT motors. The tube remained intact:
Above: The stainless steel (303SS) tube withstood L-2 blowouts. The L-2 on the left was predrilled to ensure a 'blow out'. Nasty. The L-2 LT on the right is scorched but intact.
So far so good!
Rob had high hopes for the lighter alloy tubes. He hoped their good conductivity would prevent them being melted.
This is the actual experiment with a prepared L-2:
Above: The Rapier ignited easily, gave a good thrust (about 160 mN) then a 'blow torch' flame on the right appeared.
And here's the alloy tube post-run:
Above: The Rapier 'blow-out' has burned a neat hole through the alloy. The model would not have been protected.
This was disappointing. I then tried an alloy tube with L-1. These motors are smaller. But do they burn as hot as an L-2? After two runs with prepared L-1s, this was the result:
Above: L-1 alloy tube with a Rapier L-1 on the left. The alloy (6061-T6 Al) has been melted through. This implies the Rapier burns hotter than 550 degrees Celsius.
Conclusion: no scientific experiment is a 'failure' if it gives a clear result. In this case it is: alloy is not effective; stainless steel is the way to go. A layer of ceramic tape around a stainless steel tube will be needed to protect a model from the high temperatures. I think we can live with the extra 2g weight.
My thanks must go to Rob for making and posting these tubes.
As an aside, turning to the actual models:
I have been protecting my profile models with self adhesive metal tape behind the motor:
Above: The Corsair II ready for its maiden flight. Note the metal foil and the down-thrust tab (made from the thin metal off a coffee can top).
Caution: (red alert!) The self-adhesive metal tape currently sold by, for example Halfords (in the UK) is too thin. This stuff is far better:
Above: this works fine for me. Available on eBay.
I look forward trying out ceramic mounting tubes, and trying a stainless steel Rapier mounting tube in a model.
Watch this space!
Dan Dare Exhibition, Herne Bay 29 April - 1 July 2017
Howard Smith has just told me about an exhibition he is organising that I think will be of great Intest to many Jetex flyers. Here is the poster :
And here are the details:
This promises to be a most exciting event! For those who doubt there is a 'Dan Dare-Jetex connection, this will remind you:
If any forum member gets there before I do (I don't travel too well at the moment) plese tell all of us about it.
Onwards and upwards,
Added 05/07/17: I've just had this from Howard:
Here’s a photo of the Spaceship – not that great a shot. I have the main plans alongside if and not displayed I also have the Launcher plans and building instructions.
Currently into first week and much has happened with people coming forward with items never seen and stories of relatives who were involved.
If any of your Jetex colleagues come to the show, get them to contact me beforehand and I’ll meet them and bring the other plans along:
This looks to be a great event - if any Jetexinista visits please tell us!
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