Jetex Blog

An online resource covering the technical and historical aspects of small sustained thrust micro rocket motors for use in model airplanes and other craft.

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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:

JJJ first page

 

 

And here is a taster of last summer's offering:

SAM Summer page 1

 

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.

 

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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:

Aug blog 1 

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:

Aug blog 2 

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!

 

Experiment time:

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':

Aug blog 3 

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:

Aug blog 4I 

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:

Aug blog 5 

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:

Aug blog 6

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:

Aug blog 7

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:

Aug blog 8

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:

Aug blog 9 

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!

 

 

 

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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. 

Spaceship 4

 

Spaceship 5

Above: Jetex Space ship on display, and on its fearsome spring-loaded launch pad.  (Both photos from Mike Ingram's archive).

 

Peter Cock 

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':

J50R

J50R 2

 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.

 Spaceship 6 

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:

http://archivesite.jetex.org/models/kits/kits-other.html#spaceships

 

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:

Eagle logo

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:

Spaceship 1 

 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.

Spaceship 2 

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: 

Spaceship 3 

 

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! 

 

 


 

 

 

 

 

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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: 

Corsair II 1 

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.

CorsairII Mount 

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:

MiG 19 1

But this is what happened on its first flight:

MiG 19 2

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:

Hunter damage

 

 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: 

exp 1 

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:

exp 2 

exp3

Above:  rolled tube and motor.

exp4 

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: 

exp5

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:

exp5A

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:

exp6

 

A case of, "Houston, we have a problem!

exp5B  

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:

The end

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!

 

 

 

 

 

 

 

 

 

 

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Those who have read my latest postings on the forum will realise that I am now, with a refurbished set of heart valves working as about as well as a mint condition (though antique) Jetex 50 or, perhaps, a new Rapier L-2X,  ready to give Jetex.org the attention it deserves.

 

Folk that I meet on the flying field are appreciative of the website.  This nice - it is there for the free flight rocket flyer - and it is my hope to add to the site and make it an even better resource for those, young and old, who want to fill the sky with smoke trails, and not the thrumming of the latest ARTF drone.

 

I have not been altogether idle during my enforced months of convalescence, and I have put together several new designs, including this 'semi-profile' T-38 Talon:

Talon 1

 

T38 1 

 

T38 2 

T38 5

Above:    My latest models were designed, if that is the right word, by modifying  3-views retrieved from the Internet.  After some manipulation of the flying surfaces, templates were then refined and decorated using 'Paintshop pro'.  

The printed templates were then transferred to (generally) 1/16" light balsa.

 I made two versions of the T-38 in the livery of the USAF aerobatic team (the 'Thunderbirds'): number '1'  to check everything went together OK, (note the square fuselage) and no '3', where the fuselage is 'fleshed out' and a lot more rounded.  

Both await their  'rocket pods' (for Rapier L-2) and  trimming. 

 

Well-known rocket-flyer and 'prime pilot' Andy Blackwell has recently 'beta tested' this design for me:

AB T-38 

Above: Andy was quicker finishing his T-38 Thunderbird (no 2') than I was with numbers 1 or 3!  Here he is after its first very successful and spectacular flight.

 

Next, something for the Francophiles (you know who you are!): 

Mirage 2

 

Mirage 3 

Above: Following the success of my semi-profile F-106 Delta Dart, I couldn't resist trying a  Mirage III.  If it flies as well as the Delta Dart I will be well pleased.  This is 'printed paper over balsa', which allows for a more rounded fuselage.

 

Back to the US: 

CorsairII 1

CorsairII 2 

Above: The Corsair II has all the proportions of a very stable model - large flying surfaces and plenty of fuselage side area.

 

And now for something completely different: 

Cutlass 3

 

Cutlass 1

Above: The Cutlass was let down in real life by its poor engines.  In miniature it presents a challenge, but I'm hoping that my version, powered by a Rapier L-2X, will show what the original could have done for the US Navy.

The Corsair II and Cutlass are printed 'Dark T-shirt' heat activated transfers over balsa.  This allows for a colourful model - note the balsa doesn't show through, but fuselsges are best left with square edges. 

 

Designing and building all (balsa) sheet models was therapeutic, but by this time I was fed up with staring at the computer screen, and hankered after something' stick and tissue' that needed a little more building: 

Hawker Hunter 2 

 

Hunter 1

Above: My original Skyleada Hawker Hunter was wrecked by a Rapier 'blow out' in 2008.  Here it is brought back from the dead and ready for covering.  Note the attention paid to the jet pipe, which looked a little 'naff' on my first one.

 

Here it is again, canopy fitted and ready for airbrushing - not my favourite procedure:

Hunter 2015 blog

Above:  It is covered in white 'Starspan': green Modelspan would have been better, as I hope to finish it in the 'eu de nil' ('duck egg green') of WB188, the first prototype.

 My building skills don't approach those of ubermodellers Mike Stuart, Peter Smart, Richard Crossley et al, but it's the best I can do.

I also cannot build light:  at the moment the Hunter a little over 26g without paint, motor mount or nose weight.  So think '32-34g' ready to fly.  It will probably need all of the 160 mN of thrust an L-2 X can provide.  We shall see.

 

 

Howard Metcalfe, too, has been taking a break from profile models:

HM Cougar 2 

Above: Howard's Cougar.  This is Andy Ray's design.  I do hope it will be finished before the end of the 2015 Flying Season.

 

If any reader is interested in any of the new profile models, I can supply templates that you can print out and attach to balsa, for example:  

Cutlass blog 

 

Or a set of finished balsa parts.  These, though, will cost you £17.50 including postage.

 

So there you have it: I'm all set for the 2015 season.  I would love to hear from you about your own models, especially 'work in progress'.  Please email me with a picture or two and some words.

 

I also hope to meet you on the flying field  - my next meeting is Middle Wallop in mid June.

 

 

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Ducted fans to power scale jet models have been around since the early 1960’s and Veron’s kits and Impellers fetch high prices on eBay.  The Fairy Delta 2, especially is still a sought-after plan.  But most the i/c motors of the age were never comfortable at the high speeds ducted fans required, (Phil Smith confessed his FD2 was little more than a 'powered glider') and even though there were a number of successful semi-scale plans and model kits (like the Telasco Skyray) it was a specialist niche  and was never going to be very popular.

Electric motors are much more comfortable at high revs ducted fans require: Stephen Glass showed the way EDF (electric ducted fan) was going to go years ago.  Motors got smaller and more powerful, batteries became lighter, and suddenly, it seemed, kits like Aerographic’s 20" span Hunter with a KP fan, controller and LiPo batteries became a viable prospect for the average modeller.  (And I very much include myself in this category).

Expert modellers like Steve Bage were quickly off the mark  and his MiG 17 is a fine of example what could be achieved with the new technology:

 

mig 17SB

 Above: Steve Bage's sophisticated Mig-17 for an internal 32mm KP EDF unit.  Note the paper-lined jet pipe.  Beautifully built, this model also featured 'R/C guidance', and was, alas, lost in a flyaway.  The plan can be supplied on request.

Chris Richards has demonstrated his less ambitious but eminently practical Depron La-17, which has an internal 24 mm fan, to me several times:

 

CR LA17 new

 

Above: Chris Richard's LA-17, built as a 'proof of concept' for unbelievers like me.  Flies OK in a steady fashion, but has a liking for trees!

 

A very nice EDF version of the Telasco Skyray was also flying at Old Warden recently (sorry, no photo!). 

But I remained curiously unmoved by these models – yes they flew ‘free flight’, and pretty well, but they were bigger  than the Keil Kraft and Jetex ‘Flying Scale’ models of my youth and somehow didn’t ‘hit the spot’.

 

What I craved was a little EDF the size of a Jetex 50 that would fit in the trough of an old Jetex model.   The good news is that the redoubtable Derek Knight in the UK  has developed such a unit: 

DK Fan

 

Above: Derek's prototype of his miniature EDF unit.  The package is 'all in one' containing motor, fan, controller, timer and batteries.

 

The complete package will cost perhaps as much as four packs of Rapier L-2's.   The bad news is that the package – motor, fan, timer, and speed controller is not due for release for some months.  But it will be worth the wait!

 

Derek showed off his new EDF 'power train' at Old Warden recently, and made several nice sorties with his Skyleada Mystère:

DK Mystere

 Above:  Derek's Mystere is built exactly as the Skyleada kit of sixty years ago.  It's a bit heavier, but the  wing area can handle this.  The EDF unit fits in the Jetex trough.  Note the thrust tab.  The EDF makes an interesting jet like whine in the sky.

 

The flights, short as they were, were  impressive: this was a ducted fan model I could (at last!) be interested in.  It is certainly the ‘right size’ for me, and the fact the complete ‘power train’ will just slot in an established model will mean the transition from rocket power to fan power should be relatively painless.

Now the model(about 65 grams) is (at present) about twice the weight of a Jetex model (say 30-35 grams) but the thrust of the fan (up to 40 grams) is more than sufficient to give a nice climb out and a quite fast circling flight at about 30 feet.

OK, where’s the brisk acceleration, the smoke, the excitement and unpredictability of Jetex or Rapier?

But the very lack of a chaotic flight pattern makes EDF less traumatic, and will suit some temperaments.  It will also make some ambitious scale projects – a Bristol 188 or a French Trident, models one would hesitate to put a Rapier of uncertain specification in – more attractive. 

Trident 

Above:  the interesting Trident - two small jets on the wing tips and a rocket in the fuselage.EDF enables ambitious jet models to be contemplated without fear of an uncertain power supply.

Now here’s an exciting possibilty ,  A Trident with two 18 mm ducted fans on the wing tips could be launched into the sky with confidence.  At height a Rapier L-2 in the fuselage could be lit …. Just a thought! 

Trident 2

 

 To conclude: If Derek's plans come to fruition, we should soon  have an alternative means of flying those old evocative Keil Kraft, Veron and Skyleada Jetex models.  But, as I said, Derek’s package is still under development, so please be patient.

 

Am I a heretic, but  could  the ‘Jetex future’ really be micro (or ‘nano’) EDF? 

 

KP Sabre EDF

 

Above: Derek with his Keil Kraft Sabre (coloured as a 'Fury', very nice) built without modification.  Note the tiny EDF unit in the trough where the Jetex 50 went.  It is a bit heavier than one with a Jetex or Rapier, but, by adding another battery, you can up the watts and have a bit more thrust to play with.

 

 

 

 

 

 

 

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I have now tested some of the latest L-2 and L-1 motors collected from Dr Zigmund by our very own 'Nighthawk'. 

Dr Z's  nominal thrust ratings are:

70Mn for L1
130Mn for L2
150Mn for L2X
200+Mn for L2HP
 
We have, as yet, no examples of the 2014 'L-2 HP' or L-3 motors.  
 
In actual tests, and these were in duplicate or triplicate to be sure I wasn't measuring a 'one off' rogue motor, this is what I found for the motors we do have in stock:
 
L12014 thrust
 
 
Above: note the 2013 L-1 motor tested with the others.  Thrust is a bit down from when I tested these in 2013, but still very usable.
 
 
L2 2014 thrust
 
 
 
L2 X2014 thrust
 
 
 
The first thing thing to be said is that these thrusts bear little relation to dr Z's 'nominal'  ratings, and I really don't know how Dr Z arrives at his figures.  But mine are what I found, and I have the videos of the thrust rig to prove it!
 
 
 
However, the good news is that the output of the 2014 L-1 motors is healthy, a bit higher than those from 2013, but great for  profile scale models of 8-10" span.
 
The 'standard' L-2 motors are disappointing, the thrust is low, and though the run time is gratifying, the motor cases did come close to 'burning through':
 
L2 2014
 
 
They are of too low a thrust for the old 'Flying Scale' models and though suitable for profile models, I did find them difficult to light.  They needed extensive 'boring out' with a 1mm reamer and the addition of 'fairy dust' (ground up match heads) to get going.  I would advise these are used with caution.  In the right (light!) model the long burn time could give a splendid flight and a long walk!
 
I hope that when Dr Z visits in July he can bring some standard L-2's of a more useful specification.
 
 
The good news is that the 2014 'L-2X' motors are quite close to what I found for the 2013 examples:
 
L2X Blog
 
Above:  L-2 X motors tested in 2013.  This graph is included for comparison.  Ace flyers like Mike Suart found them very useful, and my larger F-100 Super Sabre liked these motors a lot!
 
 

 

Note the  shorter, though still acceptable, burn time of the 2014 motors.  The 2013 L-2X  motors worked well in built up models, and  larger profile ans semi profile models (like my F-100) and I hope these 2014 motors will be the same.

 

The less than good news is that stocks of these 2014 L-2 X's are limited - so order now.  

 

For those who want to fly Rapiers this year, and are starting out - my advice would be to buy some L-1's (of which I have good stocks ) and put it them in a (colourful) profile model (see the Jetex.org store!).

 

I hope  talk to Dr Z in July  so we can get some good L-2 motors of 120-130 mN, but until then we do have to, as in years gone by, work with what we've got!

 

As an 'addendum' to the above, here are some photos taken during the actual tests, just to prove I'm not making any of  this up!L2 test

 

Above: a standard L-2 in the middle its run.  Note the reading hovers on '11 grams'.  The weight of the motor at this point can be calculated to be about 3-4 grams.  The exhaust is barely visible.

 

L2 2014 thrust end

 

Above: a standard L-2 at  the end of its run.  Note the reading, seen through the smoke, is now '0 grams'.

 

By subtracting the weight of the motor at each time point (the motor looses about 5-7 grams during the power run ) it ca readily be calculated that the thrust of these standard L-2 motors is, at best, below 100 mN.  Note the charred motor case.

 

L-2X thrust

 

Above: an L-2 at mid run.  Note the reading hovers on '27 grams'  If the motor at this point weighs about 4 or do  grams it means the (static) thrust is over 200 mn.  

This is a useful amount of grunt, but not the 150 mN' specified.  Note the rather impressive glowing exhaust which contrasts with the more feeble exhaust of the 'standard' L-2.  The L-2 X was a lot louder, too!

 

I must emphasise that these simple static thrusts  are useful in the comparing of motors, and the thrust in a model in high speed flight will be different.

 

 

 

 

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Tis Spring, and in the spring, an old aeromodeller’s fancy turns to thoughts of trimming all those models built during the dark damp days of winter.  Readers will remember my current penchant for profile models, and I have just returned from the local recreation ground with a spring in my step and a bag of no less than five newly trimmed scale jets: 

 Profiles March 2014 3

Above:  new profile models for 2014.  All glided well from a strong hand launch, needing only a little nose weight and little adjustment of adjustable rudders (Mig-19 and Alpha Jet) or elevons (F-106).  They now just need motor mounts and a calm day!

 

For lots of good reasons profile scale models (‘PSMs’) make a lot of sense for us jet jockeys.  There are a lot of excellent designs, new and old, available at the click of a mouse; they are easy to make, fly well and if you lose one due to a dubious motor it’s no big deal.  They are great, too for experimenting with unusual planforms. 

RS 0709 707 

Above:  Roger Smith at Old Warden, September 2013.  The sadly undecorated profile Avro 707 was a lot of fun and flew splendidly with a (side mounted) Rapier L-2HP.

 

But I did have a problem with profile models in the old days,  though, believing the term ‘profile scale’ was an oxymoron.  To me they were crude and unsophisticated, even if (to repeat) they were quick to build, light, easy to adapt to a range of thrusts, and, if damaged by errant motors, were easy to repair or replace.  I couldn’t, somehow,  accept them as legitimate.

Part of the problem was that in my early rocketeering days I saw, and was attacked by, some very lacklustre models launched by quite prestigious modellers.  I was very unimpressed by their pale wooden bodies and great lumps of Blu-Tac stuck on their noses (the models, not the modellers). 

 

 

Fortunately, I was converted by the wonderfully decorated models of Howard Metcalfe: 

Howards profiles 

Above:  a selection of Howard's profile models from a few years ago.

 

HB 508

Above: Howard’s more recent Supermarine 508.  Note the meticulously painted (sprayed, I believe), finish and the thrust tab.  The butterfly tail is quite unusual.

HM Skyray 

Above:  Another of Howard's more recent models.  This is what Bill Dean's Skyray should look like!  Howard prepared the templates using CAD.  These were then printed on tissue which was then affixed to sheet balsa before assembly. 

 

Others, too, showed me what PSMs could look like: 

WS Javelin 02 10 

Above: Walter Snowdon’s fine Jetex Javelin.  Such beautiful paintwork takes more skill and patience than I can easily muster! 

So it was that I started the ‘Campaign for real PSM’s’ whose members eschew bare wood, will crush, dismember or surreptitiously eliminate any examples of, say,  Bill Dean’s Skyray or Hunter that lack national markings and fin flashes.  

The old Veron and Keil Kraft ‘ARTF’ profile kits like the Sea Hawk came pre-decorated, and looked good on the flying field without too much effort from the builder.  Though they are easy to recreate using computer graphics programs, they appear only to appeal to old guys like me who remember them from the first time round!  This is a pity as they still make an excellent introduction to rocket flying.

 

George Foster, like many older modellers,  prefers to design his own models.  But, I am pleased to say,  he obviously aggrees with the principles of CRPSM:

GF Provost naked 

 

GF Provost 1

Above: George’s Depron Jet Provost before and after decoration with felt tip pens.

 

But for me, there was a  ‘problem’: finishing the bare wood (or Depron) requires skills with paint (or  felt-tip pens) that I don’t find easy.  I lack the patience and artistic acumen to do this well.  

So I prefer the ‘printed paper on balsa (or Depron)  methods which have  been all but perfected by Rob Smith: 

F-100 Pair April 2013 

Above: it’s easy (and quick) when you know how.  Rob’s two Super Sabres.  Take your pick!

 

This method can be taken as far as you want to go, if one is happy with a square fuselage the templates can be transferred directly to balsa or Depron sheet: 

MiG-19 sq 

 

Alpha Jet sq 1

Above: two examples of my profile models ‘just off the press’  with square '3D' fuselages.  Here, printed templates are transferred directly to sheet balsa. 

 

Alternatively, you can complicate matters by going for a rounded fuselage: 

MiG-19 rd

 

Alpha Jet rounded 1 

Above: also ‘just off the press’ - two models with rounded fuselages.  Here, templates are transferred to the balsa surfaces after construction.  Not easy! 

 

Is rounding the fuselage  worth the effort?  Probably not, even though it saves a little weight.  The  square ones seem to fly equally well, and in the air, who is to notice?  And all the extra complication rather goes against the received wisdom that profile models should be ‘quick and easy’.

 

John Rigby is another member of CRPSM, and uses (I think) printed tissue on his true profile models:

JD MiG-21

Above: John’s very nice MiG 21.  Hadrian Tucker has ponted out that tissue on balsa is not particularly light, and printing directly on balsa would be better.  Yes, but how? 

 

 Chris Richards, too, believes in properly decorated profile models:

Mig29 L2

Above: Chris’s MiG 29 triumphed at the 2014 Peterboro' Flying Aces.  Built from sheet balsa, templates could be transferred to balsa sheet before building.  But this is more than a simple profile model:  perhaps ‘semi profile model’ is an apt description?  

 

Meanwhile, I carry on with my own obsession.  Here is the latest:

Tiger 1

 

If anybody would like to join the CRPSM, please contact me.  Members could receive a T-shirt and a badge, and a full set of felt tip pens to use on any bare bodied models (I know, I know) they find on the flying field! 

 

Oh yes: if anyone can suggest an easy ways to transfer printed copies of computer generated templates of models to balsa, or knows of a reasonably priced flat bed printer that can handle 1/16" sheet balsa, please let me know.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Every organisation, well the ones I’m familiar with, like the Society of Antique Modellers, the British Model Flyers Association and the Village Tidily Winks Team,  share a grave (and I use the word ‘grave’ with its morbid resonance advisedly) common concern: “Who will carry on after we are gone?”

A trip to model flying events, especially  free flight, shows that the vast majority of flyers are either in, or are approaching, what are, one chap said, their ‘twilight years’.  Hmmm. 

There is the occasional youngster on the field with granddad, but of 15-20 year olds (the group amongst whom modelling was so popular in the 1950s-1960s), there is little sign. 

So are we the last free flight sport modellers, and, more pertinent to Jetex.org, the last ‘Jetex’ modellers?

Perhaps young modellers (under the age of 45) fly the splendidly cheap R/C RTF models – park flyers – and the like?  But if they are, I don’t see them.  Perhaps they are busy on their simulators, and will one day graduate from this solipsistic obsession to the real world.  We can but hope.  And that, having crashed their first real model, they don’t look for the ‘reboot’ key!

In the spirit of, “It is better to light one candle than bemoan the dark” the BMFA promotes a number of cheap and cheerful models suitable for the fledging flyer. 

One of these, the Aerojet delta, might go well with a Rapier … this got me thinking: in the main, the simple Jetex kits suitable for the beginner, like the Veron Sea Hawk or Keil Kraft Shooting Star, are over fifty years old and (apparentlu) attractive only to those who remember them from their youth.  The Jetex.org ‘part kits’ are, I think, very nice, but sell only to those happy to part with a small proportion of their pension:

Jetex org Sea Hawk

 Above: the Jetex.org Sea Hawk.  It is a faithful replica of Phil Smith's original Veron 91950?) kit for Jetex 50.  Only bought today, alas, by modellers of a 'certain age'!  

 

So to try attract youngsters I thought I might try something more colourful; a MiG-19 for example:

 

MiG19 1

 

Above:  The prototype MiG-19, inspired by the Japanese Tiger kit of 1958-1960. It is more modern than the Sea Hawk, but will it still be seen as desparately old fashioned?  

 

I then thought, what else is out there likely to attract the young Jet Jockey?  Jason Wentworth, similarly concerned to evangelise modelling in general and rocket flying in particular, sent me examples of a little chucky popular in the US that he thought might just be suitable for an L-1: 

DD Chucky blog

 Above: readily available in the US, Jason thought these near-unbreakable chuckies might go well with an L-1. Perhaps, though they are a trifle small.  Could be a lot of fun, though.

 

Perhaps, I thought, there are some more suitable 'quick and easy' models  out there?  A quick survey of the giganormous Hobby King site  came up with a few suitable  candidates:

Alpha Jet HB

 Above:  Hobby King's all Depron Alpha Jet.  At only a few ponds I expect they sell well.  But will the young jet jockey graduate from this to something a little more challenging?  

 

Sukhoi 2

 Above: Hobby King's SU-11.  An exciting model, and at just a few pounds (though don't forget the tax and the (quite steep) postage) it costs less than the kits available on Jetex.org. 

 

OK, and according to my friend André Bird the Hobby King jets  can be rocket powered, given a bit of serious ‘fettling’ (his Raptor needed two Rapiers mounted atop!):

AB F22

 Above: Andre showed off his adaptations of the Hoby King F-22 Raptor and F-18 at the 2014 Peterboro Flying Aces.  He says they do fly (though he declined to do so in the wind we had) but are more than a little tricky to trim. 

 

And this is the point worth emphasising.  I can produce an Alpha Jet nearly as tasty looking as that offered by Hobby king:

Alpha Jet 1

 Above: My prototype (and unfinished) Alpha Jet.  Being all-balsa  the flying surfaces are very stiff, and trimming with a Rapier L-2 should be straightforward.

 

It does, of course, need more 'building' than Hobby King's models, but it will (I hope) fly in a fast and in a smoky way with a Rapier motor ‘off the shelf’. This justifies the asking price, but will the punters see it that way?

To conclude: has  anyone else out there attached Rapiers to Hobby king’s products?  And finally, how can the joys of Jetex and the rewards of Rapiers be evangelised to the next generation?  Any thoughts?   

 

 

 

 

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We've just added some more models into the Jetex Store ? if you go to the Store you can scroll to the bottom of the page and then navigate to the second and third pages which also now display models :)

You can now choose between L1 and L2 power for your new model. Simply click next to the power of your choice.

Other profile and semi-profile models are in the pipeline, including a MiG-19 and
F-102 based on the vintage Japanese Tiger models, and an original Alpha Jet.

migs

 

Please contact Jetex.org for the latest availability of Rapier motors.

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Our intrepid contact with Dr Zigmund (‘Nighthawk’) will soon be collecting Rapiers for the 2014 flying season.  He asks what types we would like him to collect, so I told him, “A repeat of the 2013 types please”.

These motors were favourably received by rocketeers, as the L-2X motors were perfect for models like the Aerographics Bell XS-1, Bluebottle Bell X1E, Mike Stuart’s Thunderstreak, and the larger profile models like Bill Dean's Hawker Hunter or my own F-100.

The L-2HP is potent enough for the older larger Flying Scale models and the Aerographics Sukhoi SU-11 or Steve Bage’s MiG 21,and the latest L-1s are just perfect for smaller profile models.

 

Rapier Shinden 3

 

 

Above:  Rob Smith's unusual Jet Shinden flies splendidly with a Rapier L-1.

 

 

My thrust-time graphs I produced for the 2013 motors are shown below:

L2X Blog

 

 

Above: L-2X

L2-HP 2013

Above: L-2 HP - pretty potent!

 

L1 2013

Above:  The latest L-1s - a really great motor!

 

So (a) think about what jets you should be building this year, secure in the knowledge that, at least on this side of the pond, you will have something to power them with (b) ask yourself what motors you would like this year. 

And you could always  phone up SAMS Models in the UK and encourage  George to restock with his Rapier kits!

 

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I recently bought some very nice vintage Tiger kits from a gentleman in Japan:

mig1901

Tiger profile kits, made in Japan in the 1960's were nicely presented.
The F-102 Delta Dagger and MiG-19 are I think unique, and well worth replicating today.

Today's modeller has access to many computer techniques simply unknown in 'the old days' so that the parts of an old kit -– and the vast majority of 'Jetex' kits are old and date from the 1950's – can be scanned in, cleaned up and replicated. The trouble is, most of the modellers interested in such kits also date from the 1950's. We have problems getting the best out of sophisticated drawing/painting programs – well I do anyway – and modern modellers who can make the latest CAD or version of Paintshop sing and dance are not interested in granddad's latest antediluvian model. So I struggle on, cutting and pasting on bits here and there until that classic and evocative Jet from 1951 looks 'half right':

 

mig19a

A Hawker P 1081 – the precursor of the Hunter - for Rapier L-2, designed and drawn using a popular 'Paintshop' program. Reproducing the 'eu de nil' pale blue/green caused an outburst of 'computer rage'.

 

But it takes hours, what a young expert can do in minutes takes me hours, and I end up truly pixellated. 'Never again' I say, until I find the next evocative prototype on the Internet.

 

Since first writing this, I have been putting together templates for an Alpha Jet, MiG 19 and an F-106 Delta Dart (which initially I derived from the Tiger Kits F-102 Delta Dagger).

 

Silver/grey is particularly tricky to reproduce - 'Fiffty Shades of Grey' isn't in it as it becomes blue/green  on printing and transferring to balsa with heat transfer paper.  Any suggestions?

 

F-106 Blog

 

Above:  progress so far with the F-106 for Rapier L-2.  All 'profile models' tend to be caricatures, and  note the wings are enlarged, but are the various shades of grey here 'over the top'?

 

 

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It seems strange to me that Jetex stuff is apparently sold on eBay and, by all accounts, posted off to the lucky winner, without the restrictions that apparently apply to Rapiers. I have bought motors and pellets on eBay with good results.

Fuse, though, is definitely dodgy – to buy and to post – and some of the old stuff doesn't burn very well. I am told that Dr Zigmund is 'on the case' so if I hear anything I'll let you know. Meanwhile, I guard the good fuse I do have – the test is to see if it stays lit through a Jetex nozzle – and hope somebody clever comes up with an electric igniter.

ebaypurchase

This nice item appeared on eBay recently, but will the fuse (right) still work?

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Another modelling technique Joe Mansour experimented with was 'paper over balsa'. This is a method well suited to profile jets, and, using computer programs not available to the old guys in the 1950's, very colourful models can today be designed and put together very quickly:

draken01

Draken designed by Rob Smith using CAD. Construction is printed paper over Depron and balsa.

draken02

These models make a very good introduction to rocket flying, as they are robust, light, easy and inexpensive to build. Also – a consideration given the nasty weather we have been having – another can be printed off if the first one flies away in a thermal or crashes because of turbulence.

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One of the inventors of the original Jetex motors, Joe Mansour, explored innovative ways of building models – for example the 'Tailored' series with internal motors:

hawkerhunter01

An original Jetex Tailored Hawker Hunter rescued from eBay and beautifully restored by Ian Hobbs.

 

A feature of these models, the fully moulded balsa fuselage, is not too difficult to reproduce, for example this Draken:

drakken01

Draken for Rapier L-2. The fuselage is moulded; the wings and tail are built up.

 

The trick is to use the very lightest balsa available, and I can fully recommend online suppliers like
http://www.slecuk.com/catalogue/sitemap.html

The Draken is a little over 30g – much lighter than an old Tailored model and should fly well, but, what with the weather at meetings we had last year, has not been fully trimmed out.

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b2ap3_thumbnail_lansen1_20140123-112134_1.jpg

Flying small model aeroplanes with rockets is a thrilling activity, one open to all, but in the last couple of years there have been questions about the availability of Rapier motors, and their reliability and performance when you can get them.

Although they are not now sold by model shops like the splendid 'SAMS Models', who nevertheless sell models for them, see: 

http://www.samsmodels.com/acatalog/copy_of_AEROGRAPHICS_KITS.html

Rapiers are still made by Dr Zigmund in the Czech Republic and available in this country. They can be collected at meetings or by personal delivery. The situation is not unlike that of the more powerful motors for model rockets. But, if you want 'em, you can get them, and the latest 2013 batches are well worth having.

The latest L-1 motors put out 100mN for 10 sec, giving my Swedish Lansen (above) a sparkling performance:

The latest L-2 motors are also pretty potent, and so far, I've had no blowouts. So we can build and fly with confidence!

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b2ap3_thumbnail_cougar03_20140123-112259_1.jpg

 Welcome to the first of what I hope will be regular 'Jetex and Rapier related 'blogs'. As this is my first foray into the 'blogosphere' it will take me time to find my niche, so please bear with me.

These will of course be full of interesting observations about the modern 'small model jet plane flying' scene which will motivate a loyal cadre of enthusiasts to keep up with the latest news about motor availability, upcoming meetings and how to take part in what I hope will be a growing part of the free flight aeromodelling scene. Note the 'free flight' bit. I have nothing to say about those marvellous and sophisticated RC jets that we see showing off at meetings. However, free flight EDF is pertinent to our hobby and is one way of keeping our models flying. We shall see!

What with the winter weather – my own flying field is more suited to hydroplanes than aeroplanes at the moment – I have been designing some new models for the new flying season. These are simple 'semi-profile' models like the Cougar above  suitable for the latest batch of Rapier L-1 and L-2 motors.

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