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TOPIC: Some thoughts about lighting and launching.

Some thoughts about lighting and launching. 4 years 8 months ago #127

  • ahmetcalfe
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The flying season is about to be on us and I am hoping to get some serious Rapiering and maybe even a little Jetexing in the next couple of weeks. So I have just finished modifying my new micro torch (Cook’s blowtorch by KitchenCraft www.kitchencraft.co.uk ) to make into a tool for igniting Rapiers and Jetex motors and I am delighted with it. It was a lucky find in a charity shop for only £3 against about £10 elsewhere and is many times better than my old one which looked very similar. Obviously my old one was a knock off copy as the new one does not leak gas, turns off fully and is better made all round so hopefully the piezo electric igniter will not give up the ghost after two seasons. It has the great advantage of being able to ignite Jetex motors as well although I have only tried it on a 50 so far. I still use the gauze but make a .1” dia hole in the centre of it, sometime the old pellets takes two three or even four prods but I have never failed to light one yet though.

Here it is

Close up of the business end

Heating up the .03” stainless steel probe

Inserting the hot probe into a used L2 Rapier. Note that a very small flame is left burning as I was not quick enough to swap hands and grab the camera before it would have been too dull to show up. In actual use the flame would be turned off fully before sticking it in the Rapier nozzle, you have got to be quick though before it gets too cool – we don’t want no burned up models do we?

Here’s a list of the mods needed,

.03 stainless steel wire probe held in place by a twist between two cooling fins and some fuse wire around the front of the nozzle.
Stainless steel gauze wind shield cut from an old tea strainer.
.03” aluminium wrap around the nozzle to hold probe and gauze together.
Bend a start/stop lever from .067” R/C control rod with heat shrink sleeve and tie wrap retainer for single handed operation, you need this as your other hand is holding the model!!

For comparison here are my two igniters together, electric and gas, little and large if you like, the electric one is a handy size to keep in a coat pocket but a bit weighty. The electric igniter is home made and takes four AA dry cells, shown here in the safe carrying mode with probe protector and contacts separator keeper. I find it very handy and convenient too and use it a lot with Rapiers, the gas torch is a stand by when the batteries go flat though!

Switch keeper and probe protector off and ready to use.

Press down on the red piece of ply and the hot end gets very hot.

Whichever you use, either of these tools takes a bit of organising to get the model off smoothly and quickly as the procedure is this: you hold the model with the left hand and light the motor the right hand! Once the motor is showing signs of running you have to put the igniter down somewhere safe, then swap hands and launch the model. I think I will try hanging the igniter on a lanyard from to my left wrist next time out so I can just drop it once switched off then concentrate on launching the model with my right hand.

Up until now I usually kneel down to ignite the motor, put the igniter down on the ground then stand up to launch, however as an alternative I sometimes use a ‘cat stick’ (catapult stick) whereby the model has a peg under the nose and is held with the loop of elastic stretched to the other end of the stick with your left hand. Ignite the motor with your right hand and upon ignition just release your grip on the model and away it goes with enough speed and energy to allow the motor to build up to full power before it slows down.

Final tips, when it works properly the fuse method does have an advantage in launching as you have more time to swap hands while the fuse is burning down (but looses some motor run time over the catstick). However, I rarely resort to using either Jetex or Rapier fuse these days but when I do I only use the fattest round fuses for Rapiers. I don’t bother with the square ones as they are sometimes quite puny and are hopeless in cold weather so I have had to warm up the bit of fuse between my finger tips. I also find that the Rapiers run better in the winter if you keep them warm in your pocket from the moment you leave home, watch you don’t set light to your trousers though as your legs might take off in all directions!

Happy flying, Howard from Hants
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Last Edit: by ahmetcalfe. Reason: incorrect jpg

Some thoughts about lighting and launching. 4 years 8 months ago #128

  • PeeTee
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Hello Howard

C'est moi again, and well done Roger for resurrecting the Forum - much water has passed under the bridge since the days of Carlo and Benintucson :cheer:

I'm delighted to see that you've not given up experimenting and the igniters look sufficiently simple for home construction without recourse to a machine shop. So much so that I'm now incentivised to dig out my stash of Rapiers and cobble together a profile model.

I still have a fair stock of Jetex 50 pellets I acquired a few years ago (and stored in my spare bedroom much to my wife's chagrin), but may look to sell them later this year as I can't see me using them.

I look forward to seeing you again at MW before too long.


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Some thoughts about lighting and launching. 4 years 8 months ago #129

  • rogersimmonds
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Hi Howard,

this is very useful in view of reports that Rapiers from 2013, and more to the point, the latest Rapier L-2 motors, are 'difficult to light'.

Fuses are difficult to come by, so electrical ignition makes good sense, and 'Bovie Cauteriser Tools, available from SAMS Models in the UK, and on eBay, are popular. One criticism of these is that they are expensive, but they can be modified to take fresh batteries and Nichrome wire of 28-32 swg.

and the body extended to take three AA batteries instead of two.

This gives a nice healthy glow and will light most motors in a couple of seconds.

Some motors, for example L-1's from 2013, can go 'pop' just after lighting, and igniting the remaining propellant requires a longer filament, or the addition of 'fairy dust' (ground up match heads) before applying the igniter.

I have had few failures. As Howard says, doing all this one handed is tricky, and one can lose valuable time swapping hands, etc, so if a buddy can do the igniting bit for you, so much the better! :)

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