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In preparation for lock downs four too five and to utilise Flying Flynn's laser CNC design.

I have once again probably bitten off more than I can chew with complicated monocoque build that's going to require a jig.A magnetic or large board jig will swallow up the last few square inches in my tiny shed/workshop.So I need something small and mobile that I can put on a shelf or hang from the wall at various build stages when my bench space is required for other tasks.

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I was on the look out for a nice straight piece of 6"1 plank to use .But that would be far too easy for a masochist such as my self.So I've set about on a doomed mission to reinvent the wheel.A length of 2040 aluminium extrusion with 3D printed adjustable sliding attachments.

Hours of Fusion 360 doodles and failed prints later it's starting to get somewhere.

Only after printing and actually attempting to use the adjustable bit's and pieces have the short falls come to light.Which is parr for the course I find with any design I attempt.The yawning chasm between my ideas and the practicalities of the real world.

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The two clamps in the centre with 3D printed threads work surprisingly well and fastened nice and snug on  printed 12mm 1.25 threads.The printed threads were slowly worked through with a little vaseline in the manner of tapping a thread.I was intending to sink a bolt into the bases and use steel bolts.But I found these leave indentations in the soft Ally. How ever a taller vice faces will be added to V15.The contraption on the left is a height adjustable clamp holder. I'm still undecided as to whether this is of any practical use.The feet I stole from Flying Flynn's CNC STL's? 

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It is all work in progress what with this being my first build from plan.And I expect all the clamps and gubbings will change with each stage of the build.The side supports being the part of the plan that won't get a second outing on the print bed.I was guilty of over thinking in that department.Using a notched rail to adjust width and a lack of height on the clamp making its uses limited.

 

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The obvious way for these side guides/clamps to be fitted is a slot and a simple nut n bolt.Blindingly obvious after struggling with CAD and a six hour print.

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So before embarking on any more wasted CAD and printing time do any jig users have any suggestions as to what may help turn this daft idea into something usable?I realise a plan over a steel build plate is probably the better option.I will have to measure the distances for the remaining tail sections but hopefully all will provide a straight base to build from  for my first foray into planking a fuselage.

 

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that's a beast of a jig

 

all the jigs I have seen before seem to be of three sorts;

 

holding the formers directly:

* using a length of square alu tube to slide the formers on

or

* a flat board with some square & true uprights to clamp or screw formers to

holding the outside of the sides:

* a SLEC style jig with lots of adjustable width clamps - really good for balsa box type shapes, not so much for planked curved shapes

 

no particularly useful suggestions but following along to see where you end up with it!

 

 

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It's the SLEC style width clamps are what I'm working on now.The only thing slowing me down is the print times.A reasonable amount of internal structure is needed for strength.This simple but clever sliding clamp found thingyverse takes two and a half hours.A neat design with an eccentric  cam for locking it in place.But adapting this design for a 2040 section extrusion profile will push my limited  CAD knowledge.

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It looks very ingenious but I wonder whether it achieves what is needed in a plane- i.e. that the wing seat is parallel to the tailplane seat.  Your jig might allow twisting.   Sometimes simpler is better and a plane built on a flat board might be more accurate.

 

Edited by kc
typing error
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One of the things with jigs is to use whatever commercial items are available easily/cheaply.  The routing people ( as in woodworking!) have all sorts of items such as 'bristol' locking handles which are used for jigs.   But unless you mass produce items it's not usually worth spending too much time making special jigs.   Personaly i use threaded nut inserts ( from Toolstation or Screwfix ) set in a flat board to form a conventional fuselage jig but the principle could be used to fix other itms for special fuselages.   But it's normally better to make formers or wing ribs with suitable tabs on to bring them down to a flat surface. 

Aeromodellers often use just two types of jig - a fuselage jig and a wing jig - and they are usually very  simple and useful for many different models.      The wing jig could have been used for your fuselage - if the formers all had the suitable holes designed and drilled in at an early stage.

 

Having said all that I do understand why Bob wants to use his brains to produce something special!  It's the challenge to produce something better than the last chap...

Edited by kc
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I agree with your points kc.It's mostly easing lockdown boredom this project.Creating a overly complicated solution to a simple problem.The apocryphal story of the one million dollar development budget NASA space zero G pen.And the Soviets using a pencil springs to mind. But the alternative (checks TV listings) is Loose women.

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A little further down the road with this side project.A few varying clamp designs fitted to the rail and a few improvements being made as I test the latest components.This work is mostly extending the clamp heights.The side clamps are now fastened with bolts(sourcing some wing nuts for theses).

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My requirement for a space saving mobile build jig are getting there .The extrusion rails give a good centre line for alignment and a flat surface for reference to T squares,spirit levels and the like.The ability to pick up a build in progress and turn it around for access ,or store it away was my principle aim.

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It can be placed on a shelf or hung from a wall when the precious  bench space is needed for other work.And the addition of being able to hold it like a rifle and view the build from a down the "gun sights" angle is a bonus I didn't think of.I can now leave the jig hung up and set the CNC up in its place to carry on cutting the plan.No  doubt as the build progresses the  design  will change.

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I’m sure I saw it on a video tour of somewhere like seagul. Lines of straight poles with formers slid on, and longerons people building 20 at a time. I once had an extra which had a hole near the bottom which wasn’t big enough for an exhaust can, and not boxed it, took me a while to work out what it was...twas where it slide off the jig.. very simple

Edited by extra slim
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