In the development of the Sirius we realized that we would need a new airfoil. The Sirius is intended for competition level flying why it needs to be reliable and durable and we have had serious problems with aileron flutters on our previous models.
With our experiences from AG series as well as other soaring designs we started to iterate some different ideas in X-foil to find an airfoil which could respond to our main characteristics.
To get the ailerons more resistant to flutter we have
- put the relative thickness to 7.5%
- increased the thickness of the rear part of the airfoil (compared to AG-series)
- designed the aileron width to 27%
The HM51 (Hammarskiöld-Mattias) is based on RG14 and SD7003. The thickness, camber etc is then changed in X-foil to meet our design targets. As many new designed airfoils the bottom has its “normal” position while the upper side has a negative flap setting and vice versa.
The thickness is 7.5% and the camber is between 1.8-2.3% depending on flap setting.
Below you can find Cl/Cd polars for some typical Re numbers and flap settings.
Coordinates HM51
1.000000 0.000257
0.993057 0.001280
0.978841 0.003152
0.963466 0.005130
0.947852 0.007023
0.932193 0.008766
0.916448 0.010418
0.900661 0.012007
0.884836 0.013552
0.869006 0.015055
0.853168 0.016521
0.837318 0.017952
0.821464 0.019360
0.805609 0.020744
0.789746 0.022101
0.773893 0.023424
0.758033 0.024715
0.742175 0.025975
0.735847 0.026471
0.732928 0.026703
0.725068 0.027435
0.710997 0.028744
0.695155 0.030197
0.679311 0.031627
0.663469 0.033034
0.647632 0.034421
0.631793 0.035791
0.615955 0.037137
0.600114 0.038470
0.584278 0.039779
0.568444 0.041063
0.552613 0.042329
0.536782 0.043567
0.520956 0.044786
0.505138 0.045981
0.489308 0.047152
0.473492 0.048296
0.457676 0.049408
0.441850 0.050479
0.426038 0.051507
0.410240 0.052479
0.394441 0.053381
0.378653 0.054208
0.362866 0.054954
0.347088 0.055608
0.331314 0.056167
0.315565 0.056623
0.299824 0.056967
0.284093 0.057196
0.268391 0.057300
0.252702 0.057268
0.237033 0.057093
0.221401 0.056762
0.205807 0.056256
0.190259 0.055562
0.174771 0.054654
0.159346 0.053502
0.144000 0.052075
0.128762 0.050346
0.113664 0.048273
0.098735 0.045815
0.084019 0.042925
0.069594 0.039523
0.055604 0.035562
0.042175 0.030957
0.029856 0.025754
0.019029 0.020028
0.011164 0.014740
0.006342 0.010605
0.003278 0.007272
0.001997 0.005763
0.001407 0.004805
0.000775 0.003479
0.000245 0.001917
0.000009 0.000330
0.000190 -0.001103
0.000664 -0.002312
0.001242 -0.003256
0.001775 -0.003921
0.002861 -0.004835
0.005248 -0.006362
0.008727 -0.007933
0.013955 -0.009719
0.021769 -0.011728
0.032077 -0.013666
0.043938 -0.015302
0.056568 -0.016598
0.069571 -0.017573
0.082789 -0.018292
0.096155 -0.018804
0.109623 -0.019146
0.123165 -0.019347
0.136768 -0.019429
0.150419 -0.019409
0.164100 -0.019309
0.177820 -0.019137
0.191562 -0.018902
0.205324 -0.018615
0.219117 -0.018286
0.232943 -0.017923
0.246793 -0.017537
0.260675 -0.017134
0.274591 -0.016717
0.288537 -0.016290
0.302511 -0.015862
0.316504 -0.015433
0.330515 -0.015008
0.344542 -0.014589
0.358584 -0.014181
0.372630 -0.013783
0.386695 -0.013396
0.400777 -0.013012
0.414870 -0.012636
0.428958 -0.012264
0.443037 -0.011894
0.457103 -0.011523
0.471164 -0.011149
0.485217 -0.010766
0.499254 -0.010377
0.513285 -0.009979
0.527309 -0.009570
0.541331 -0.009150
0.548903 -0.008921
0.558518 -0.008625
0.568839 -0.008303
0.582300 -0.007882
0.595479 -0.007463
0.609377 -0.007020
0.622975 -0.006583
0.636576 -0.006146
0.646162 -0.005840
0.655181 -0.005551
0.663783 -0.005275
0.677458 -0.004838
0.691126 -0.004407
0.696998 -0.004224
0.699974 -0.004133
0.702047 -0.004068
0.706277 -0.003939
0.718810 -0.003560
0.726272 -0.003336
0.728760 -0.003266
0.729614 -0.003250
0.730041 -0.003236
0.731867 -0.003173
0.735519 -0.003068
0.746549 -0.002756
0.760402 -0.002374
0.774255 -0.002005
0.788108 -0.001649
0.801965 -0.001306
0.815826 -0.000984
0.829689 -0.000675
0.843553 -0.000390
0.857425 -0.000133
0.871295 0.000095
0.885166 0.000289
0.899047 0.000447
0.912926 0.000568
0.926810 0.000652
0.940694 0.000695
0.954581 0.000691
0.968445 0.000611
0.982063 0.000494
0.994087 0.000301
1.000000 0.000257