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Old Sep 29, 2012, 08:35 PM
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I agree totally the less weight the better i flying orni's and it is a real issue especially as you stop flapping there is no thrust but enough about orni's.I have sourced all i need to build but 3mmin white 2.5mm in black was all i could source so a a bit more weight it has to be but hey . Taking on board what you have said above i will try to lose weight where i can cheers Brian
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Old Sep 30, 2012, 02:46 AM
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Originally Posted by therealthing691 View Post
I agree totally the less weight the better i flying orni's and it is a real issue especially as you stop flapping there is no thrust but enough about orni's.I have sourced all i need to build but 3mmin white 2.5mm in black was all i could source so a a bit more weight it has to be but hey . Taking on board what you have said above i will try to lose weight where i can cheers Brian
I'd suggest using only the 2.5mm and then adding colour with tapes (black planes can be very difficult to see properly in the sky, especially on an overcast day). Maybe use the 3mm for the spar and spar doubler.

Here are the approx changes I made for the Funjet Light (in Sketchup) - may help you decide where you can save weight.
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Old Oct 02, 2012, 09:59 AM
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More motor tests

I had a chance to do some more testing of performance with other motor/prop combinations (all on the light version of the funjet):

Emax 2822-1200KV with 9x4.7" prop: Best park flyer combination so far - stable and easy to fly, but still very agile. Not the same top speed as the earlier prototypes, but really was fun to fly (helped that there was not a breath of wind)

Turnigy 2826-2200KV (Hobbyking's 2212/06 2200KV parkjet equivalent) with a 6.5x6.5" and then a 5x5" prop: Definitely a lot faster, but started to become less predictable...kind of like a Mugi. Low speed manoeuvres not as good as with the lower KV motors. Got the feeling that the Funjet Light was just a little too light for this power setup (but its perfect for the slightly heavier standard version). [EDIT 29/11/2012: Flew the same setup but with a 2200mAh LiPo and performance was much smoother and more predictable - not unexpectedly the resulting higher wing loading must be helping the plane to handle turbulence etc better]

Turnigy 2826-1400KV with 9x6 prop: Back to being a true park flyer, but a bit more 'souped up' than with the E-max motors - nice top speed and good handling at all speeds

These result suggest the following rules of thumb:
1) For a trainer setup build a light version and use a motor in the 2810 to 2812 range that can turn an 8" or 9", low pitch prop (~1200-1400KV)
2) For a speed machine build a standard funjet and use a 2812 motor that can turn a 5" to 7", high pitch prop (~1800 - 2700KV)
3) If you want to use a bigger motor such as the Papsnoek's 2836, build a larger version - probably 110% to 125%.

PS: There may be some confusion over motor sizes. Different motor manufacturers use slightly different numbers to describe their motors. So a Turnigy 2826 has a 28mm outside diameter and a motor length of 26mm (excluding the shaft). The Suppo 2212 parkjet motor has exactly the same dimensions, but the 22mm refers to the stator diameter and the 12mm to the stator length...or something like that.
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Old Oct 05, 2012, 12:49 PM
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Tiled plans

Tiled plans for the light version attached - should work for making templates. Original version can be made by simply not making the cut outs (new wing shape looks better, so I'd recommend using it)

Looking at the Blucore wing thread, it seems as if they use the same folding technique to create the wing aerofoil - I'd encourage someone to try and use bluecore instead of correx for this design (bluecore is not available in SA). There should be a weight saving, plus the pool noodle should protect the blucore from most crash damage.
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Old Oct 13, 2012, 05:06 AM
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Did my build build ended up using 3mm but total weight rtf loaded with battery 2200mah 40c constant battery is 940 grams with the 10x5e prop it produces ample thrust will madien it tomorrow weather permitting here is some pictures cheers Brian

could have been lighter but hey is damn strong will use 2mm next time if im not happy with performance happy flyin guys regards Brian
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Old Oct 13, 2012, 10:53 AM
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Excellent - good to see the funjets multiplying (Papsnoek maidened his last weekend). What did you use for the fuselage? It looks a lot larger than a pool noodle!

~950g is not overly heavy for a 150% funjet. My 110cm Vulcan (which is really just a jazzed up funjet/mugi weighs in at ~1100g, and I think my 150%Mugi was close to 1000g

Good luck with the maiden - hope it goes well
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Old Oct 13, 2012, 11:10 AM
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It still flies!!

Prototype 2 had a serious mishap this am when my younger nephew lost orientation near a large tree...the impact was clearly heard several hundred meters away. Apart from the large bite out of the wing, the left wingtip and vertical fin came off as well.

Remarkably, after getting it out of the tree, we just threw it and continued flying! Had a bit of left yaw, but was still capable of rolls and loops...

Time to help graft in a new section of wing....its owner is not too happy that his pride and joy does not look quite as flashy as it used to.
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Old Oct 13, 2012, 10:11 PM
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i ended up doing it 130 % and the fuselage is pool noodle maidened it had a succesful flight then a pretty hard crash that made the nose of the fuse bust but glueing it as we speak cheers Brian

was a bit over confident but was great fun and pretty damn fast from gliders and ornithopters
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Old Oct 14, 2012, 05:16 AM
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second lot of flights few successful flights i will add here that its the first time i have flown a jet with mixing while flying slow and sedate all was good but because of very large throw on the flap like 70 degrees up and down it is very touchy on the controls . Well i thought lets speed it up and do sum stunt s well another nose plant and was amazed no damage . when i repaired it i taped it as well the speed it hit the ground spiraling i was really amazed. Anyhow after this i think i will adjust the throw to about 30 or so degrees till i get used to flying it . Also with the 10 x 5e prop it can fly slow but is rather fast to.All in all a lot different experience to gliders and ornithopters but heaps of fun and very very durable cheers Brian
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Old Oct 14, 2012, 12:35 PM
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70 degrees! Quite impressed that you managed to fly it at all!! My throws look to be about 15 degrees each way (I measure 12-15mm max deflection each way on my 100% versions - about 20mm should be more than enough for your 130% version - maybe use dual rates to give slightly more deflection for low speed flight). Full deflection on my Mugi is a only few mm each way

Prototype 2 is now repaired (took all of half an hour) and its owner is very happy with the new trim (used to cover the repair seams). Got to love correx - hard to break and so very easy to repair.
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Old Oct 15, 2012, 12:55 AM
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70 degrees! Quite impressed that you managed to fly it at all!! My throws look to be about 15 degrees each way (I measure 12-15mm max deflection each way on my 100% versions - about 20mm should be more than enough for your 130% version - maybe use dual rates to give slightly more deflection for low speed flight). Full deflection on my Mugi is a only few mm each way

Prototype 2 is now repaired (took all of half an hour) and its owner is very happy with the new trim (used to cover the repair seams). Got to love correx - hard to break and so very easy to repair.
Well EXTREME i like a challange as for setting dual rates i only have a cheap 4 channel radio with mixing .I have never needed anymore with what i fly.As i metioned it is the first time i have flown using the mixing function on my radio as none of my glider have vee tails.
Anyhow i really enjoyed the funjet and thought it would be good to learn on and after i reduce the throws a bit it willl fly a lot more sedate.I find it a lot different to flying gliders as it is all good fun regards Brian
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Old Oct 17, 2012, 03:17 AM
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This one is HOT!

Had some spare time this weekend, so made some design changes aimed at improving the high speed performance. Took some design cues from the Radjet as well as pylon racer designs....the result is the Correx FastJet.

Maiden was a blast - needed some up trim, but otherwise it was very fast and totally predictable. However, this definitely is not a design for beginners - it has no self correcting tendancies and orientation is hard, given that it very quickly becomes a small dot in the sky. Speed now probably exceeds that of my Mugi, but the FastJet goes where you point it (as opposed to the Mugi, which sometimes seems to have its own ideas of where its going).

Needless to say it won't fly as slowly as the Correx Funjet.

Maiden set up was Turnigy 2826-2200KV, 5x5 prop and 1300mAh 3S Lipo. AUW was ~450g. (this has increased to 500g with the vinyl colour scheme).

I think it has potential to take a larger motor (I see on the Radjet thread that they are using 2836 motors with 4S lipos)...but I think I need some time to get used to the speed before I try to increase it!

When I get some spare time I'll draw up some plans and post details of the specific construction changes made to improve high speed performance.
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Old Oct 19, 2012, 05:16 AM
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looks get IMO i think building with correx is a great idea cheap and strong what more could you ask for
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Old Oct 19, 2012, 12:15 PM
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looks get IMO i think building with correx is a great idea cheap and strong what more could you ask for
You missed out v quick and simple to build and repair!

BTW, I estimate that the materials for each Funjet airframe costs about R50 in SA, including vinyl covering and glue, but excluding electrics and associated mounting items. Thats not much more than US$5 per plane!

2mm correx, 70mm pool noodles and vinyl sheets are readily available and dirt cheap here; unfortunately I can't say the same for foam or balsa
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Old Oct 23, 2012, 02:41 PM
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FastJet construction

Here are some details of the changes made in the fastJet:

1) Wing aspect ratio increased and sweepback reduced (reduces drag)
2) Wing profile made thinner than the FunJet - 15mm vs 25mm (reduces drag)
3) Correx spar shortened and no doubler used; instead a full length CF spar added (wing profile now too thin for the correx spar to give the required strength)
4) Servo mounted on its side inside the wing (thinner wing profile and tapered wing shape meant that the servo position had to change)
5) Motor mounted so that thrust line is in line with plane centre line
6) Elevons constructed using a double layer of correx with a sharp trailing edge (add torsional rigidity for high speed and reduce drag) (I'll post the details of this mod separately)
7) Fins positioned outside of prop arc (I needed to keep the fuselage clear for a larger ESC)
8) Nose cut to taper in both vertical and horizontal planes (looks better)
9) Modified wing tip profile - deeper and flatter section (reduce risk of tip stalls)
10) Thinner wing section means that I had to cut right through both layers of the correx doublers to fit the battery.


Some pics of the changes attached:
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