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Quote:
Already thinking on 2x lander 68mm alloy units.. |
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Australia, VIC, Melbourne
Joined Nov 2006
6,277 Posts
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1) Turnigy L2855's are too weak for the Su - though it is interesting that twin 5S L2855-2300kv CS10's scoot the 3.6Kg Me-262 along very fast. These are only 1000w each. But the twin 6S L2855-2100kv's in the Su were no better than stock (prob a bit worse by the looks of videos) but also ran to near 1200w and fried.....
So that is two aircraft of twin 70mm CS10's, very similar weights (mine), yet the 5S Me-262 kills the 6S Su-35. I guess the open nacelles of the 262 allow full CS10 thrust to be realised, whilst the very 'long' Su total ducting costs energy. It takes a pair of HET 2200kv's, and a fair amount more power (Watts) for the Su to match the 262. 2) See my blog for the Lander 6S Alloy CS10. It is great value.... $72 (or even $66).... 1900w capable (per one fan unit), but you would really use 1600W max area, and more like 1300w cruising.... and it can do it with ease, as it is 'big' 2960-220kv motor, with the alloy cooling too. If I didn't already have the HET's I would throw in a pair of these for sure!! A 6S 5000mAH 65C battery runs ONE with ease..... but drive a PAIR and even a battery of those high end specs will be taxed!! They will do 1.8Kg sustained, and 2.1Kg burst - if good batteries!! But I bet they will lose something like 0.3Kg to 0.4Kg in the Su. Plus the fact that even a very goo dbattery, needing to drive TWO of them, will not be able to maintain the voltage to produce those single unit test numbers. (not in any fan combo chosen also). 3) Use the new CS12-70mm.... no better power/load than the CS10 but the same price and a much stronger fan and housing. So if I was doing the HET path again I would use these. But the HET's are $75 EACH motor and you get the entire pre-assemblesd and balanced Lander for less!! Though the GRP CS12 is lighter than the Lander Alloy, and probably saves towards 200g total using this manner. But I myself have no problems with more weight, I LOOK for useful weight sources anwyay. 4) CS12 70mm's but with a cheaper motor.... there are a few more in the $40 area, thus more like $55 all up..... again not far off the Lander cost, but that lighter total again. At the moment the Lander is an impressive value, and result, combo.... so it is hard to pass up that option! Mind you if you have Power Capability, then you need Power SOURCE Capability too! Better, more expensive, batteries! eg 65C. Though even the HET's really need that - as they are basically the same power result as the Lander. And I would say there isn't much of a way to escape needing a fair amount of power in the Su anyway - it needs it more than a more conventional wide/swept wing (eg Me-262) needs. eg The Me-262 can get away fine, and be fast, on 2000W. The Su really needs more like 2200W (Or probably more... 2400w to be 'fast'). |
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Saw this on another thread that was posted by Twitzidbowler, its a new company that is now carrying FW planes and many other brands. They have the Su35 ARF/RTF & Kit version while having a flat rate shipping of $5. Also looks like they will carry spare parts at some point.
http://www.motionrc.com/freewing-su-...gray-camo-arf/ |
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Australia, WA, Perth
Joined May 2007
3,088 Posts
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Pete,
What torque are those servos? Might be worth moving the servo horn around a bit so when the LEF is up, the arm is straight - that way the servo doesn't have to fight the flap for the entire flight... (I do the same with trailing edge flaps) |
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Australia, VIC, Melbourne
Joined Nov 2006
6,277 Posts
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2.7Kg approx. There shouldn't be much force on them at all when up, even in heavy manuoevers. Flow, due to near equal curvature top and bottom, would be equalised in level flight, and at pitch rotations the levels against one side, over their small area, would be unimportant. (They are somewhat a total of some ahead of CofG, but not much)
The Starmax F-16 had issues because the joints are not perfect, with no gap, and also no 'covers' thus huge turbulence situations possible, and poor hinging. Then at that point, throw in the WEAK servo pushrods that bent under pressure and it totals "Disaster"!! But none of that is applicable here. |
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Australia, WA, Perth
Joined May 2007
3,088 Posts
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I know you don't like graphs, but...
![]() The airflow on top and bottom are both trying to move the leading edge in the same direction - very rarely do they cancel out. Because the centre of pressure (or lift) of that little wing section is in front of the hinge line, it will always be unstable. Your servo then has to do the heavy lifting. In constrast, TE flaps are stable. Imagine if you will, putting the taileron hinge on the trailing edge. That's what the LE flap is... |
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Australia, WA, Perth
Joined May 2007
3,088 Posts
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I used a couple of dots of foam safe CA, and a tiny amount of 2 part rubber (commonly mislabeled as 5min epoxy). I've since had to crack them off twice to adjust linkages, and the worst damage done was the paint delaminated where the glue held. No biggie, as it's all hidden in the join anyways!
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Australia, VIC, Melbourne
Joined Nov 2006
6,277 Posts
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hehe, I see some "arrows".....
The levels of the vector forces (those willy nilly arrow lengths in the pics) are not going to be any issue I am sure. I can use "Visualised prediction of forces" based on experiences for that determination! LOL Those tail 'bits of wood' can't really be screwed into the foam. But if you wanted to you could make some plywood inserts so that you had something substantial to screw into. I myself would also use captive nuts on that idea, and thus use 3mm bolts - 2 or 3. I haven't looked/checked but most likely slits from below, to feed the plywood plate/s into - X amount inboard of the sides (eg 5mm to 10mm - the more the better!). Thus the bolt forces pull on the plates which have a large area against foam. |
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