Official Black Horse Fieseler Fi156C Storch 2850mm ARF Discussion Thread

[TonyF3A]

Alpha: I already had the cowl cut out, just left it off to adjust the carb if needed. I found the carb diaphram was stuck, so it was easily removed and the problem corrected. Engine then started right up, no adjustment to carb needed. I used an aftermarket Gas tank. I'll supply pics later today or tonight..

However, the maiden flight without the nose weight resulted in a tail-heavy aircraft and required some coordinated rudder to turn. Not much fun to fly like that... So, after 2-3 minutes I landed and took it home to re-check balance. Needed the 1-1/2 pounds to balance, per the note on the picture above. Installed the cowl, made a nose spinner out of an old Tru-Turn spinner and took it for another test flight. The airplane flew MUCH WORSE!. It was so nose heavy, that I didn't have enough elevator on landing that it resulted in cracking the cabin plywood formers all around... I apparently didn't get the CG right. I had my son help me and we were very accurate using the 110 mm from the LE as the CG point, per the instructions. I put it on my balance rig and hooked a cup on the firewall to add led shot into until it balanced. I normally use lead shot and then mix with epoxy and pour into the nose area of the aircraft. easy to do and works well. I didn't go back and verify before I flew, but I am sure it was correct.

I am currently repairing the damage and will have it ready to fly in a day or so... I am going to re-check the CG but have already taken some lead out.

I would like to get a good CG point from someone who has theirs flying well.... Like Terminator 007... Can you tell me where your balance point is? The instructions also say 10 mm travel for the elevator... I find I want more like 25mm....

[Terminater007]

The CG point to use

115mm from LE of the Slat..NOT the leading edge of the wing...

The plane needs to have

coordinated Rudder with Aileron I have it mixed and set to 50% on the Futaba J10

Also I Used Closed loop for the Rudder connection instead of the pushrod as the plastic tubes where all ready in the fuse - saved a bit of nose weight..

[TonyF3A]

Thanks, Terminator! The book I have shows 110mm from the LE of the Slats, but the wording states 110mm from the LE of the Wing at the root. That's about 1-1/2" difference! I'm gonna have a discussion with Motion RC and let them know of the contradition in the instruction manual so nobody makes the mistake I did in the future.... Also good to know that you are using rudder mix. I am not so sure I was that tail heavy on the first flight. I had to use coordinated rudder in the turns as well.
Another issue I found was that the control horns on all control surfaces are really too short. I had to come all the way in on my servo arms and then cut my aileron down to about 40% travel and I still had double what the book called for. It also makes for terrible servo centering with that much of a mechanical disadvantage. I am going to replace all the control horns on the control surfaces with some aluminum U channel that I got from McMaster-Carr. It is just about exactly the same shape and size, but is 1" tall, allowing for a higher hookup point for the ball link. That will allow me to get back to 100% travel on my endpoints and have much better servo centering.

[TonyF3A]

I spoke with Motion RC and they are going to add an addendum page to the manual to show the correct CG location. I will re-assemble mine tonight and see where my CG is since I removed about 1 lb of lead from the nose....

[TonyF3A]

Well, the plot thickens....
I went home during my afternoon break and did some measuring. It is 80mm from the leading edge of the slat to the front of the cabin, with the front window removed. If I use the 115mm you suggest Terminator, the CG is just behind the back edge of the front wing tube. Looking at the picture you provided, you show 115mm to be just a bit in front of the wing mounting screws. That would be just about the right place if you use 115 mm from the LE of the wing, not the slats.... So, I would like to ask you to please check the CG and measure back to be sure you are at 115mm from the front of the slat, not the front of the wing... I have included some pictures....

One shows 80mm at the front of the cabin... that would be 80mm to the front of the slats, and then back to 115mm put

[TonyF3A]

sorry, didn't finish... the last sentence should be puts the CG just ahead of the back of the front tube. If I use the wing LE, that is 40mm in front of the cabin area, so going back gets you just in front of the wing mounting bolts, which looks about right to me. that works out to about 32% of the wing cord, which is also about right. When I flew my first test flight, I was probably at about 20mm FURTHER BACK than this 32% point and so I added weight to get TO this 32% location and the airplane was WAY TOO NOSE HEAVY.... So, I'm back to square one... Where really is the balance point on this airplane???

[TonyF3A]

Tonight I will put the airplane completely back together and get an accurate CG balance where I am now, with 1 lb of the 1-1/2" lbs of lead that I added removed. I'll report that number to this discussion area as soon as I get it done early this evening and hope I can get some responses!

[Alpha]

I'm looking through my flight records for exact numbers for this Storch (I fly most BH birds at or near the main forward spar), and we've contacted Black Horse for additional clarification. Granted, it's 4:00am here now, so, it will be a bit before they respond. The Storch has been on the market for years, too; perhaps other pilots will chime in. Either way, we're post information here as we reconfirm it. Thanks, guys.

[Terminater007]

That picture was just a quick representation of where I measure from not the actual location on the fuse , just use the 115mm from the slat and it will be fine , mines had about 90 flights so far and still going strong..


Also movements on the Elevator I have about 25mm each way and the rudder 50mm each way..

[TonyF3A]

Well, I checked the balance. I put some blue painters tape on the wing and mark 110mm back from the LE of the Slat, 110mm back from the LE of the wing. I then checked where my CG was with the 1.5lbs of lead and it was at about 120mm back from the LE of the wing. Remember, that was the CG when I crashed from being way too NOSE HEAVY. I didn't have enough elevator to stop the decent. I now have removed about 1 lb of the lead, and that brings be to about 135mm back from the LE of the wing. THis is probably just a little forward of where it was for my first test flight when I thought it was tail heavy. Upon checking, this measurement is just about exactly 110mm from the LE of the wing, AT THE POINT WHERE IT MEETS THE FUSELAGE! The LE sweeps back when it meets the fuselage. I now wonder if this is where the CG is supposed to be? The picture with the blue tape across the fuse and wing is the 110mm from the LE of the wing at the fuse. This works out to just about the back edge of the box that surrounds the wing mounting bolt, or about 15mm behind the wing bolt.

[Terminater007]

Its not LE of wing at Fuse , its 115 mm from LE of The Slat which works out something like approx. 6 - 7 mm past the front wing Joiner tube that's where I fly it and it flies well ….
anyways not much more I can say so good luck....

[TonyF3A]

My airplane balanced at 175mm back from the LE of the slat out of the box. It took 1.5 lbs of lead in the nose to get it to 150mm back from the LE of the Slat, and the airplane was so nose heavy that I didn't have enough elevator control (30mm up travel) to stop the decent to land. I would estimate that I would have to add 3-4 more pounds of lead to get it to the 115mm from the LE of the slat... That would be a total of 5-6 pounds. I'm not goinna do that. I understand that Motion RC is reaching out to Black Horse to get a positive location on the CG of this airplane. In reviewing (again!) the instructions, they say 110mm back from the LE of the wing AT THE FUSELAGE. The picture shows from the LE of the Slat. Just need to get the numbers from Black Horse....

[TonyF3A]

In doing the repair work on the airplane, I found it necessary to get some paint for touch ups. I went to my local Lowes and had them custom mix a quart of exterior house paint. They did a great job and it maching the dark green and light great perfectly! Attached are pictures of the can and the mix should you want some for yourself.

[3RedPapa]

Its not LE of wing at Fuse , its 115 mm from LE of The Slat which works out something like approx. 6 - 7 mm past the front wing Joiner tube that's where I fly it and it flies well ….
anyways not much more I can say so good luck....

I can confirm this CG as I bought mine in Europe a few years ago and after lots of digging got my CG from the Brits who were flying this at 1/4" behind the front wing tube. That's at 115mm from LE of the slat. I added 1lb of lead sheeting to get this CG with an OS GF40 and it flies great.

[TonyF3A]

Well, I flew it this morning at the 110 mm from the LE, and it flies like crap! A real handful... Now with a 2nd person (thanks 3RedPapa!) verifying that the CG should be 110-115mm from the front slat, I am going to put whatever amount of lead it takes in this thing to get it to that CG. By my measurements, I have to move the current CG 45mm forward to get to that point... I suspect it will take 3-4 pounds of lead, but I am gonna try to see if I can somehow attach it to the front of the engine mount to get it as far forward as possible. I'm gonna try to get it all done tonight and put in another test flight tomorrow...

[TonyF3A]

OK.. so last night I put the airplane on my CG machine with the balance point at 110mm behind the LE of the Slat, as first recommended by Terminater007. It took an additional 4 pounds of lead mounted to an aluminum plate which is attached to the front mounting screws on the R/H side of the DLE 35. I made a mold for the lead, and poured up 3 pieces and bolted them to the plate. I got done about 7PM last evening and had a window of time where it was not raining much, so I took it to the field to fly. IT FLIES GREAT! It required about 1/4" of up elevator trim at the back of the elevators to fly with the flaps up, so I would like some feedback on that. When I put the flaps down about 30mm, the model flies smooth and easy, and very slow and scale-like. Landings were easy and it flairs out great.

So, the big question has been answered! Balance at the 110-115 mm from the front of the Slat, or about 7mm behind the back edge of the front wing tube. I will pass this along to the good folks at Motion RC so that they can get the instructions modified. I also believe that I can make a much lighter stab-fin brace to save 3-4 ounces which would be about 3/4 -1 pound up front. By converting the rudder to pull-pull cable will also save nose weight. I also believe I will convert the elevator push rods to Carbon Fiber rods (still in the sleeve) and that will also help.

Once again this forum proves to be invaluable! Thanks to Terminater007 and 3RedPapa for convincing me to add the weight! Now, hopefully Black Horse can do some mods to how they make the kit so that future owners won't have to add so much weight!

[axerhand1976]

so what was the total weight of the plane with all the weight added? thx.

[Terminater007]

I recommended 115mm..anyways at least u got it flying now :)

[Aros]

Thanks Tony, I have updated the online manual accordingly. :Cool:

[TonyF3A]

I have not weighed the aircraft since, but I suspect is it around 26 pounds or so. I'll see if I can get a weight on it in the next few days... Motion RC's support staff said they would be updating the instruction manual and possibly making some production changes to lighten-up the tail of the airplane so it didn't require so must nose weight. I appreciate Motion RC's help throughout this issue!