The Whisper.. and other Carbon rod and Film/Fabric models, including indoor RC kites - RC Groups
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Feb 02, 2013, 06:27 AM
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The Whisper.. and other Carbon rod and Film/Fabric models, including indoor RC kites

NOTE.....CF rod constructions are proving to end up lighter than depron or epp build, which means good performance...and they are showing good damage reaistance..they bounce very well as I have found
Their lightness is giving them the ability to fly very slowly....and thats not just high alpha flight ..thats flying properly...they also can fly fast because of their low drag, thin wings...
Whilst the film covering can get cut up in a mid air collision, the frame has taken that sort of punishment ok... and thats only using 2mm spars and and 1.5mm frame rods... the other guys prop frame was fine....
The menace later went on to shred a mini vapor model....the CF there is just too small...

My flying buddy wanted a very easy flying model, suited to use the parts taken from the parkzone micro SU...

My easiest indoor flier is without doubt the Vapor, so the design was taken as the basis for my new model, but it is scaled up to use the more powerful motor from the Sukoi...

The basic Vapor flying at 18gms has 98sq" of horizontal area....
The Sukoi fies at 35gms..with 52sq" area
Other models are flying at 40+- gms, using SU guts, with no trouble..
So that sort of 40 gms AUW... is my target .. and to keep the wing loading low for a nice slow flier I needed to double its area or there abouts..

my first job was a sketchup design..
1.....a rough size job is easily done tracing over the image of the Vapor..
2....the model is resized... and given extra rods for a bit more strength at its larger size
Last edited by davereap; Feb 18, 2013 at 04:52 AM.
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Feb 02, 2013, 06:28 AM
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Construction techniques...

Nothing is difficult...
All rods are cut 1/2 to 1" overlength..... they are crossed over or under each other and tied/lashed with thread... the rods are adjusted for position and angle with regards to the lines on the plan, and the thread is fixed with CA glue...
I use an upholstery thread, its a not stretch, very strong polyester.. this can be purchased at a fabric, sewing, shop...

Rod selection.. pick from what youve got, but the idea is to keep things supelight.. I am still learning to use lighter materials that I am used to.. and gradually I am getting better with my choices...

On the model..rod sizes used...
Fuz... is 2.5mm rod, its a bit easily twisted but this is fine... flex up to a degree is ok.....The vapor uses a tiny box section which is much stiffer and lighter
Tail assembly... tubes and rods.. outer tubes from small snake pushrod sets were used..these are a good fit for a 2mm CF stubb rod allowing an easy turning of the rod
Wings ..... center long spar is 1.5mm ...remainder is all 1mm
Tailplane/elevator and Tailfin/Rudder are all 1mm
Last edited by davereap; Feb 02, 2013 at 07:14 AM.
Feb 02, 2013, 06:35 AM
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When laying up the design, its important to think about...
.. keeping the structure as flat as possible... do not put rods up above on one joint and below on the next..example pic 1 the two uprights are crossed on to the left of the fuz rod and to the left side of the ceter top ribrod
This is important, even more so on the wings which want to be warp/twist free..see pic3 all the spar lengths are on one side of the wing.. it doesnt matter if its top or bottom, but when you make the other half, it must mirror the first, so on the other half the spars will be on the same all along the top and the ribs all below... get muddled and you will be making a twisted wing..

Double check as you go, cause its too easy to get things wrongly placed... or build in slight twists when your angles are off, get a joint fixed wrong and you need to do it again.. but thats easy its just a thread fixing that slices off..

.. Bending rods ... never bend a rod to its maximum of the slightest impact will make it shatter...
When bending a curve , hold the tension with strong thread.. non stretch like fishing braid, dacron or the upholsterers thread is good... do not remove the bow line, lash a curve in place, like on the end of the wing, leave the thread on...
If you remove the thread the tension of the curve will distort the rest of the frame work as it tries to spring open..
If your rod wont make the bend, go down in diameter till it does it easily... use two rods if extra strength is needed on big models...

...The tailfins are all simple loops ... bend the rod till its the shape on the plan.. being accurate on size vs, the plan, is not vital, except you must get the two tailplane haves to be the same... my two tailplanes used 18" x1mm rods, overlapped by 1/4 at the join, lashed and fixed...some shape adjustment can be made by changing the angle of the cross over, then fixing the binding with CA.. some more shape adjustment is possible as you fix the center spar across the loop...
The center spar is trimmed tight to the loop and is bound and fixed to the stub axels.... lash it on tight, then adjust the rods to get it at right angles/level to the fuz... wiggle the rods to get the sections lined up before you add CA....
obviously the two tail plane sections need to be flat and level with each other... and the tail fin needs to be up at 90 degrees to them... so fiddle this correct before you add the CA...
While the CA sets hard it is still possible to finely adjust the angles... But if you get it wrong, chop it off and do it again....

The U/C is a simple triangle, fixed at the top to the fuz rod, before the depron is added.. a brace goes back from the center of the axel rod to the fuz a few inches behind where the triangle is fixed.. Wheels are 6mm depron with a 3/4" plastic tube hub..the tube is hot glued in place on the depron..the tube is deliberately long to stop the wheel wobbling much when the axel is a loose fit through the tube

Horns are made from bits of plastic dental flossers, heat bent and drilled to fit your connectors.... I use Z bends made from small paper clips... you cant get much cheaper, and they are more than strong enough on small models as well as being a good fit through tiny servo arm holes.. the Z bends are lashed and CA'd to CF push rods...more on that later..
Last edited by davereap; Feb 02, 2013 at 11:58 AM.
Feb 02, 2013, 06:45 AM
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Pushrods are made from 1mm CF ..they have a Z bend at the rear and a different bend at the front.. both bends are made with paperclip wire..

Sometimes these tiny servos have too small a hole for the easy way to open up a hole is to use the connector wire, with a point at one end .. get the point in the small hole and use a soldering iron to heat up the wire near the arm. the wire gets hot and melts open a perfect size hole through the plastic....great care must be taken not to melt anything else with that soldering iron...
I used that method to make another hole in the rudder fin arm, I needed a closer in hole to get more movement on the surface..

The pushrods are guided/supported about every 3 inches.. this stops the long rod from flexing ... and the surfaces are better controlled

With these on board servos the travel is limited so its of vital importance that you get the connectors accurately placed.. when you fix their positions the control surfaces should be where they need to be...

On a double check my rudder bend had to be repositioned so the rudder was nicely straight... had to cut it off and refix.. this can be fiddly , but is worth the effort..
Last edited by davereap; Feb 03, 2013 at 05:07 AM.
Feb 02, 2013, 11:59 AM
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The model is now covered... with it ready to fly using a 5x3prop and a 160 lipo the AUW is 45gms....1.28ozsqft
The target Vapor is 0.91ozsqft
Last edited by davereap; Feb 03, 2013 at 09:53 AM.
Feb 02, 2013, 12:58 PM
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Things to come...

A small model with all moving wings , tailplane and tail fin..
based on the carbon traveller, I hope this will be highly maneuverable at ultra slow speed..
Feb 02, 2013, 01:00 PM
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Ive been getting further into the build, and have already deviated from my original lines

changes ...going with rectangular wings... they are less fussy than curved tips
I altered the fuz vertical rod positions , and I realised that having both wings with no stagger would be simpler
The rear fin and tailplane are as before with a couple of rod bracing added
changes are on the drawing.... close up perspective looks a bit weird in some of the shots, but the shape is as per the plans
Last edited by davereap; Feb 04, 2013 at 10:49 AM.
Feb 02, 2013, 01:00 PM
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starting on the wings....a very simple rectangular shape ..try to remember the bearing tubes and to make matched pairs with rod placements
Last edited by davereap; Feb 06, 2013 at 04:25 AM.
Feb 03, 2013, 07:13 AM
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Good work on these projects!

Jim R.
Feb 03, 2013, 09:47 AM
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thanks jim... the CF builds do seem a bit more durable than light weight depron. but the game is to get the weight down so they fly well... 45gms is just acceptable
Feb 05, 2013, 12:23 PM
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great build thread

thanks for the awesome build thread, descriptions and pictures. I hope to do this soon, but with 2.5mm bamboo...I know it will be heavier but cheaper, and my motor is stronger and slightly heavier. I'm looking for an AUW around 60-70gm, I want to be able to fly it in a medium size living room, so high alpha and very good slow speed handling is a must.
Can the vapor design do high alpha? Just increase the elevator throw...surface area?
What did you cover with, wrapping paper ? Have you tried grocery bags?
Feb 05, 2013, 05:09 PM
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Yes you can fly the vapor with the nose up a bit and it flies very slow. I do it all the time and I the battery is all the way back.

Feb 06, 2013, 03:16 AM
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Originally Posted by JohnC
Yes you can fly the vapor with the nose up a bit and it flies very slow. I do it all the time and I the battery is all the way back.

ah thanks

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