Fi-156 "Storch" by BMI review and total mod

Fi-156  "Storch" by BMI  review and total mod 

Last year I purchased a Fi-156 Storch  by BMI . I would like  here to make a review of my idea about the model.

Here are some   information from the website

Hersteller: VMAR/BMI

Spannweite: 1943mm

Länge: 1250mm

Abfluggewicht: 1600gramm

Motor: Pichler Motor BOOST 40 [C2983]

Propeller:Aeronaut 13x8 [7234/57]

Ausstattung: Landeklappen

 After opening the massive box  , I found  the rather big hull and  the  split wings . Have a look here  to  see the basic fitting test I did . You may also see the massive wingspan . I assumed that I needed a bigger workshop ....

 The  fitting is  done  and I headed on to  the more technical construction . Have in mind that the model needs 

-1 servo (mini) for rudder

-1 servo (mini) for elevator

-2 servos  for the ailerons

-2 servos  for the flaps

The   wings are held together  with  two aluminum tubes (very lightweight  ) . Each time  I  have to install the wings  , I need to install the tubes  and  and to adjust all  servo cables  in the  hull . The whole  arrangement  needs lots of time . Double it  as I have to do the same  for assembling  and dissassembling  the model  for  transport. 

After construction , I  had some basic issues 

1. The wheel structure  is very flimsy 

2. wings  are  very flimsy

3. Aileron hinges are awful  giving a scale look  but a very bad movement effect . Also they need securing  with  glue and screws.

4. The company did not provide any info regarding the battery that should be used. Only about the balancing point . 

      At the field  #1

  The  test started  very bad . I went to the field  and   started fitting  all parts .  When everything was ready I  put  the battery and .. boom .. !!  The rudder servo   burnt ! 

   I changed it  and  we were ready for  the  first  power test . My  friend held it vertical   and I  pressed the throttle . I  momently heard a crack noise   and  then silence . The motor/motor mount system  flew many meters above our heads  and we run  here and there  for safety ... . 

    The  result was that the cowl  was ripped of  by the flying motor  . The motor   had  a bent shaft  after the hard landing  and  the whole model was in compolete mess  without being flown .

 

      At the bench #2

      I installed  a  harder  ply 4mm  firewall  and a  alloy  motor mount (instead of the wooden factory one) . I also removed  the bent shaft and installed a straight one from  stainless steel .  Some minor changes  at the wing fitting  made the whole arrangement a little  easier. Then I was trully happy  and sure about the constrution... yes .. of course... !

      At the field  #2

       The  second  try  was a little more successful.  I  launched it  and  had a 10 minute  flight time.  I  saw that it tended to tip stall so  I had to turn it with the rudder. Each time  I tried to turn with aileron/elevator  it stalled. And it stalled badly ! After  a low pass  I  felt that I had no power. What happened? The esc was burnt ! I made  a mistake and trieed to tunt it   while losing height  in order to gain speed. But is tip stalled  and feell of the sky . It broke  in the nose  and the center of the hull . Some pieces of the  wings also broke  but the overall view was of a model that could be repaired. 

     At the bench #3

      I first  wanted to  identify  why the model  tip stalled so badly . The philosophy of the model  is that  it should have very low flying speed , so why to tip stall  that way? 

      My test result saw me (after some investigation ) that  I trully had to reduce the flying weight . As I did not know  what battery  I should use , I used a 5000mah lipo  which is nearly as a brick ! I thought that  a model of this wingspan  could easily handle it . But philosoply (also) of the Fi156 is also of a ultralight plane ... . I re-balanced it  using a 2200 11.1v lipo  . I also removed soem other smaller parts  and I was sure that it lost some weight (more than 300gr) .

        At the field #3

        One again at the field...  I  wanted to  test  the result of the height reduction .  After take of , I tried to make  some flight test  of how iit handles and turns. The tendancy to stall was still there  but not  that much . Also I saw  that  it tended to be uncontrollable  if I throttled it deeply . Also  it  was not a  vstol plane  as I had to  land with lots of speed  as it tended to stall . 

So  I went  back to the bench ...........

        At the  bench  #4

        During my summer holidays  I had some time to  make an allover reconstruction  . My main goal was to  save some weight (in order to reduce wing load)  and to make my life easier  by making a better  wing arrangement.

 Here are some photos  I used for refference. The "storch" nickname came due to the unique way  the landing gear was hanging  during flying . When the plane was  on the ground , it  had the landing gear spread wide.  This is something that the  factory model  does not have . The landing gear  is has some kind of suspension  but it  holds the whole structrure ffirmly in tight angle. This is trully bad , technically , as  the model had  a tendancy to  be unstable during taxing, takoff and landing . I  replaced the landing gear  with my own structure . It kept its suspension  but  I achieved a wide  angle similar to the photo  above.

Here is  the model during the summertime restoration  and weight reduction plan.  I replaced all the internal wooden parts that were broken due  to the past faults  and hard landings. Then  I  coated  it with grey primer paint  and  I ironed  some  olive drab monokote . 

 The  true problem here came  as   I could not find  any similar  monokote color  to this parrticular  green that BMI used . So , I  used the olive drab and  then painted it with  grey primer. After the primer I was able to paint itt  with  two different coats of  green similar to  the splinter  colors of the rest of the model.

 All  lines  that represent the doors and other panels were made with  silver fine marker.

 here I installed the  new landing gear . All parts are compleetely made of stainless steel  as I needed  extra  suspension   and strenght.

The initial battery hatch was  in the lower part of the model below  the pilot. I  closed it firmly  and replaced it  once and for all  with  a hatch above. All of the front structure is removable .
Now the  access  is rather easy  and  the  preparation time is trully limited. I think that BMI should have done it that way . It is also safer for the modeller as  you  do not need  to flip the model  with  the battery power on.

 A closer photo  of the  landing gear

 In  this part of the construction  you may see  the  primer coated  wooden parts . You may also see  the epoxy  hatch  I scratch made  in order to have easy access  to the battery compartment .

 Here are some mode photos I used for  refference.

overall

Overall , until now I am not happy  with the model . It is trully   beautiful but hard to fly  and  strange . The whole construction is rather complicated   and very flimsy . Cannot be flown  in windy conditions  and there is no chance to fly it  as  a Vstol plane . It needs lots of runway to land  and plenty of speed . No  tight  turns are allowd as it tends to stol and cannot recover  nearly at all . The flaps may effect it  positively  at 20%    but  it  is trully  unforgiving . A small mistake  and it may hit the ground like   any other warbird .  Do not underestimate it as it is a high wing construction .