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Rigging biplanes with stretched sprue

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  • Member since
    December 2002
  • From: United Kingdom / Belgium
Rigging biplanes with stretched sprue
Posted by djmodels1999 on Saturday, October 30, 2004 3:42 PM
Because Frosty asked how I did it, I though I'd share my 'way' of rigging airplanes. I'm using the 'conservative' approach of stretched sprue, with really little special skills or tools required, not even too much patience (because I haven't got much of that!). It's a 'technique' I actually 'stole' from a good friend, modeler, of mine who introduced me into WWI aircraft modeling a looong time ago (Hi, Thierry!)..Smile [:)]

There are other ways to do this, of course. I'm NOT saying this technique is the best, but it works, and it works well. I'm not the one to drill in holes in the airframe and rig everything from a single piece of thread... I've seen people using fishing line but I feel it's hard to get that thread to stay straight without using some stronger glue or risking destroying fragile biplanes! I've seen people using human hair, but hair vary in length with the humidity in the air..

I apologise for the quality of the pics. Not always good, but it's not really easy to photograph things as thin as stretched sprue!

Ok, here we go:

First, the materials needed: sprues from some kit you finished earlier on (if you have kits molded in black or dark grey plastic, keep those sprues preciously as they do not need painting!), a heat source (candle for me), hobby knife, toothpick (I can't do models without those!), liquid plastic glue, a piece of white paper, a bit of scrap plastic card, a fine pair of SHARP scissors or any sort of similar cutting tool (shown here, I have this sort of tweezer type of thingy with blades at the tip that works really well!).


Obviously, you'll also need a model to rig..! Rigging is for me the very last step, other than placing things that could prevent me from reaching difficult areas; therefore, in this particular case, with the Floh, I left the propeller off until after the rigging. Not much to say about stretching sprue, it's a fairly basic technique in itself, one that one gets with some practice. I'm obviously trying to get a 'thread' that is fine enough, keeping in mind that I'll have to coat it with paint at a later stage. The only thing that's important to keep in mind is that you may need lots of stretched sprue! I stretch as far as my extended arms will go, and for a typically small project such as this Floh, I stretch about 10 meters of 'thread'.


The next stage is important! As you stretch away, in order to keep the 'threads' as straight as possible, hang them. Place one extremity of the sprue high enough for the other extremity, at the end of the fine thread you just stretched to hang freely. This allows for the plastic to cool off as straight as it can.

Notice I'm a believer of the 'Force'...Big Smile [:D]

Once I've put the candle away, I retrieve each of my stretched sprues one at a time and cut the uneven bits off. I do this over a piece of white paper, as it allows for a better 'vision'. Discard what you do not need. I'm left with about 3 different thicknesses of stretched sprue, all available in enough quantity to complete the project. I then select the thickness I'll work with.


OK, we're off to cutting and glueing stretched sprue... Put a drop of two of liquid glue onto the piece of scrap plastic card. This glue will start melting away the plastic and soon becomes quite thick. Over the project, you'll keep adding a bit of glue time to time to keep the liquid 'liquid enough'... If it starts making stretched sprue, it's too gooey, add liquid glue! Cut off a bit of stretched sprue for the piece of rigging you want to represent. Do not try to cut too close to the desired length. Give yourself some plastic to 'play with'...


Holding onto one extremity of the thread you just cut off, dip the other into the glue/plastic mix. The glue mix start eating away at your bit of stretched sprue (that'one reason why you start with a bit that's longer than what you need!) and you'll soon get a little ball of melted plastic appearing at the tip (see pic). That little ball of melted plastic is the glue that will attach the sprue to your model. Chose carefuly which side of the rigging you're going to attach first. Once in place, let the melted plastic dry, but make sure the piece of sprue go in the 'general ' direction of where the rigging is supposed to go. This will save you lots of tweaking about and will help you keep the stretched sprue as straight as poss.


Now, with the scissors (or else), start cutting away at the unattached extremity of the sprue. This is time consuming, cut, dry-fit, cut again, re-dry-fit until you have just the right length. Then dip the tip of a cocktail stick into the glue/plastic mix and bring that little ball of melted plastic where the sprue will be attached (see pic). Deposit a bit of glue mix , then using the other tip of the tooth pick, bring the sprue in contact with the mix. This is why you need to think carefuly before glueing your first extremity of the sprue: some areas are easier to reach with a cocktail stick than with your fingers or even tweezers! Repeat for each sprue!


Here are two pictures showing how I approach the control 'horns'; I attach first on the tip of the horn, then let the 'cable' rest in the right 'general' direction, then I cut away little by little sections of sprue until I have the right length; add a little glue mix where the cable disappear into the aircraft fuselage and place the 'cable' into the mix.



Next step is the painting. Checking references pays; some 'rigging' appears silver, flat aluminium, black,.. I usually mix a bit of silver with black artist's oil, make a thick wash, which I apply with a fine brush. Another brush, laden with mineral spirit is kept on the side, just in case I need to 'erase' some black that's gotten where it was not supposed to be!



  • Member since
    May 2003
  • From: Central USA
Posted by qmiester on Saturday, October 30, 2004 4:44 PM
Your thread is informative and instructive but I would totally disagree with your statement - "rigging on a real aircraft have a little sag (the rigging keeps the aircraft together IN THE AIR)". I've been an aircraft mechanic for 35 years and have worked on or maintained several different types of bipes during that period, and the discovery of a loose flying wire was cause to start looking for a problem. If you found a loose wire on an inspection, the odds were pretty good that something internal was loose or broken.
You have to remember that the wings are not supposed to move in flight or on the ground, as that can have a very drastic effect on the flight charactoristics of the a/c which can ruin your whole day, not just that flight. The flying wires pull against each other, in effect holding every thing in proper relationship to each other.
Quincy
  • Member since
    February 2003
  • From: A Spartan in the Wolverine State
Posted by rjkplasticmod on Saturday, October 30, 2004 8:13 PM
I have used a technique very similar to yours, except I use white glue for the attachment. Takes longer to set, but easier to clean up if you make an error in placement ( I usually make my fair share of errors ). Also, I leave a little slack in the rigging wires & then come back with a heat source to snap them taught.

Regards, Rick
RICK At My Age, I've Seen It All, Done It All, But I Don't Remember It All...
  • Member since
    December 2002
  • From: United Kingdom / Belgium
Posted by djmodels1999 on Sunday, October 31, 2004 1:16 AM
Thanks for that Quincy..! I'll remove the statement from my original thread then. I learned something today! I guess the 'loose' wires I've seen wwere on museum aircraft which may have not seen the sky in many many years...

Rick, I've never tried the heat source trick to straighten sprues... Always afraid of doing something that could destroy my model..! And I simply do not have the patience to wait for wood glue to dry...Dead [xx(]
  • Member since
    September 2004
  • From: Henlow, England
Posted by Jeff Gunn on Sunday, October 31, 2004 3:31 AM
great set of photos and notes to go with them ....I think we all learned how to produce a 'how to' entry as well as doing rigging
JG Per Ardua
  • Member since
    February 2003
  • From: A Spartan in the Wolverine State
Posted by rjkplasticmod on Sunday, October 31, 2004 8:56 AM
For a heat source, I use a small portable hair dry blower on it's lowest setting. It generates enough heat to cause the sprue to snap taught with out endangering the model.

Regards, Rick
RICK At My Age, I've Seen It All, Done It All, But I Don't Remember It All...
  • Member since
    May 2003
  • From: Central USA
Posted by qmiester on Sunday, October 31, 2004 5:59 PM
Rick,

i've got a friend who used fireworks punks to tighten rigging on his models. When he got married his wife complained about the smell so he started using incense punks which his wife had no problems with. I myself use a lit cigeratte (yea, yea I know, but it works). Either way, with practice the smoke from your heat source will usually do the job.
Quincy
  • Member since
    February 2003
  • From: A Spartan in the Wolverine State
Posted by rjkplasticmod on Sunday, October 31, 2004 6:09 PM
Quincy, I've used cig. smoke, freshly extinguished matches, screwdriver blades heated over a candle, you name it. I picked up this little travel dry blower for about $5 a few years ago & it works great, giving very precise control ,spreading the heat more evenly over the sprue & reducing the tendency to melt the sprue that some other methods have.

Regards, Rick
RICK At My Age, I've Seen It All, Done It All, But I Don't Remember It All...
  • Member since
    January 2003
  • From: NE Georgia
Posted by Keyworth on Sunday, October 31, 2004 9:05 PM
Great thread, gang. I've always been afraid to rig my biplanes because they always turned out with disastrous results. I'll give your method a try first, Domi, and see where I wind up. Thanks for the info, guys.
"There's no problem that can't be solved with a suitable application of high explosives"
  • Member since
    November 2005
Posted by Anonymous on Thursday, November 4, 2004 12:49 PM
Domi:
thanx 4 this comprehensive tutorial !
i am now starting 2 learn 2 stretch spue... Big Smile [:D]
fully extended arms, wow !
so far i haven't managed 2 pull a piece longer than a couple of inches,
but they were pretty thin.
nothing quite like the smell of heated styrene, mom was like
"Phew, what's that horrible odor ???"
& i had the window open & everything !!
LOL !

frostySmile [:)]

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