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The Max II
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The Max II is second version of Max. It also uses Os Max .46LA with pipe also mounted at 45 deg. and is also mounted directly by screws on backplate to the firewall.

The model uses my new logaritmic device on flaps. It allows to move CG up to 15% MAC. It gives dead stable straight segments of maneuvers and lot of feedback to handle in round maneuvers, while still able to make standard corners, but definitely without waves.

Setup data:

The model is 1550g heavy. It uses 2 blade UCT BE prop 12x3.5. Aero products Brian Eather pipe at 400mm glow - first baffle. Carb: 7.2mm i.d. with 3.5mm cross spray bar. Lap time 5.2s at 10500 t.o. rpm.


Schema of logharitmic device on flaps

The main idea of the device is in its (almost) LOGARITHMIC function. It means decreasing character. The device is used on flaps unlike direct linkage to elevator. 

Here is the elevator (x) to flap (y) ratio as used on this model with the pivot at 55%. Series 1 is 1:1 ratio, series 2 is Logarithmic device.


The picture shows that flaps go more in range up to 22 degrees, while little less in defleflection 30 degrees in corner (compared to the elevator). The feedback from flaps to handle is in same ratio, so it is clear how it works:

1/ Model has nice strong feedback in level and round loops thanx to more flap deflection around neutral. It stabilizes the model in level and straight flight. It also makes loops much smoother and pretty round. The same function makes fly off from corners much better (suppress waves).

2/ 1:1 flap/elevator ratio is not optimal in sharp corners, so logarithmic device goes till say 27deg in corner instead of 30 in 1:1 ratio. So the model turns in corner easier itself. It allows to move CG much more to nose and it gives extra stability. This model has CG at 10% of MAC unlike similar Max at 19%.

3/ The device carries back much less feedback deflected than in neutral thanx its function. Thus it needs much less line tension to make the same corner than same model without it.

4/ The result of point 1/ 2/ and 3/ is model with better ratio between "turnability" in corner and stability in straight flight.

Yes, clear there are also disadvantages especially in construction or life time, but the model has only few flights now, so we will see later.



Side view

Some pictures from building


The foam win and bellcrank installation

Logarithmic device and its components

The device installed in fuselage

The engine mount

And some pictures


Table of dimmensions:

wing       wing    
span mm 1500   area m^2 0,42
chord root mm 270   aspect ratio   5,39
chord tip in mm 195   taper   0,69
chord tip out mm 195   C/4 sweepback deg 3,76
root flap mm 60   thickness of airfoil %   0,20
tip flap in mm 30   area flaps %   0,16
tip flap out mm 34   max. angle flaps deg 27,19
tip flap to tip mm 30   wing loading kg/m^2 3,59
thickness of airfoil root mm 60   CG %   10,58
thickness of airfoil tip mm 50   max. tension flaps pushrod N 43,78
      wing AC offset (level) mm 17,96
tail       wing AC offset (corner) mm 20,74
span mm 700        
chord root mm 100   tail    
chord tip mm 75   area m^2 0,12
root flap mm 90   area tail % wing   0,28
tip flap mm 65   aspect ratio   4,24
      C/4 sweepback deg 2,05
linkage       taper   0,74
bellcrank max deg 29   elevator % tail   0,47
bellcrank size mm 100   max angle tail deg 32,23
bellcrank arm mm 24   max. tension tail pushrod N 21,94
horn arm flap mm 24        
horn arm flap/elevator mm 22   tail/wing C/4   15,43
horn arm elevator mm 20        
      necessary line tension N 21,02
lines       centrifugal force N 47,81
diameter mm 0,36   line tension over head N 33,11
lenth m 19,5   drag lines N 2,15
lap time s 5,1   lines sweepback (level) deg 2,57
      lines sweepback (over head) deg 3,71
prop       lines to hinge(level) mm 171,32
diameter " 12   lines to hinge(over head) mm 156,37
pitch " 3,5   lines leadout to hingeline avg mm 163,84
rpm 1/min 11500        
weight g 20   speed m/s 25,87
fuselage       power to wingover (mass) w 242,12
prop-wing mm 300   power to wingover (drag) w 150,59
flap-tail mm 380        
CG to LE (root) mm 65   angle of attack prop deg -2,72
weight g 1500        
weight of wing ~ g 300   tip weight (wing asymetry) g 8,30
engine out deg 0   tip weight (lines/2) g 15,48
engine up mm 22   tip weight (fuselage) g 17,68
engine down deg 0   tip weight (sum) g 41,46
fuselage offset right mm 10        
landing gears height mm 150   engine out (effective) deg 1,69
wing mass assymetry g 0   arm of engine out mm 10,74
      arm of engine down mm 22,00
corner radius m 3,50        
      overall engine momentum (level) (down) Nm 0,00
wing cx level   0,008   overall engine momentum (corner) (down) Nm 0,08
wing cx corner   0,016        
tail cx level   0,01   needed cy wing (corner)   1,80
tail cx corner   0,04   needed cy tail (corner)   0,52
wing cm corner   0,2        
tail cm corner   0,15   speed lost in corner m/s 0,68
      corner recovery (level) deg 0,00
logh. device pivot at % 55   corner recovery (level) m 0,00
      corner recovery (overhead) deg 0,00
      corner recovery (overhead) m 0,00
      lines retire (level) m 0,00
      lines retire (overhead) m 0,00
      angle of attack wing before corner deg 17,36
      angle of attack wing in corner deg 7,21
      reserve of wing cy in corner   0,01
      CG front neutral point mm 170,09
      momentum CG to neutral point mNm 90,70
      momentum to mass   6,05
      static reserve of stability in the circle 46,51
      static reserve of stability % 28,45





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Last modified: júna 05, 2002