Black Horse Piper Cub & CG (Full Version)

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Squitherfool -> Black Horse Piper Cub & CG (9/14/2003 10:38:26 AM)

I have just test flown a Black Horse J-3 Cub and it was disasterous.
The model was a real handfull (very different from what I was led to expect). We were unable to trim the pitch and the model seemed very unstable.
Eventually the model went into a spin (not deliberate) from about 50ft and was unrecoverable.
Fortunatly the damiage is light (only the front end was smashed) so it should be repairable quite easily.

I suspect stongly that the CG position in the manuall was incorrect (100mm behind the LE)
Two members of the club have similar Cubs and have their CG a good 20mm futher forward.

I was wondering if anyone else had experience of this model, and if the instructions were incorrect wrt CofG ?

Also is the behiavior consistant with a CofG too far back, I know that this would make the model unstable in pitch, but would it also make the model prone to a spin (I undertands Cubs are not supossed to spin easily) ?



Montague -> RE: Black Horse Piper Cub & CG (9/15/2003 6:29:49 PM)

I have no experience with that plane.

But the behaviour, including the spin, is very consistant with a CG that is too far back.



Christie -> RE: Black Horse Piper Cub & CG (9/19/2003 2:15:00 PM)

In my experience Cubs are not that easy to fly to begin with. I only have experience with the TT cub, but I believe yours would also be much better with the cg around 25% of chord from the leading edge for test flights.

We also find that a bit of reflex in the ailerons and some rudder mixed in with the ailerons help. In slow turns it helps to do most of the turning with the rudder to prevent the ailerons from stalling the wing out.

Hope this helps

Christie



cabanestrut2002 -> RE: Black Horse Piper Cub & CG (9/21/2003 12:12:04 AM)

what % was the c/g at??



timo_uk -> RE: Black Horse Piper Cub & CG (4/16/2004 1:04:32 PM)

I am building the same plane at the moment, and I think the Graupner Piper Cub is 100% identical to the Black Horse model. (Can anybody confirm this?).
I downloaded the build manual from the Graupner website (www.graupner.de), and they reommend 70mm, not 100mm. They also say that experienced flyers can move it back by 10mm.
The Graupner manual is much better by the way (It's a PDF in German and English) , I am using a mix of both manuals to build the plane.

Timo



alasdair -> RE: Black Horse Piper Cub & CG (4/21/2004 7:33:49 PM)

That behaviour is entirely consistent with a CG that is too far aft.

As was said already, a CG at 25% chord is a better guess, but if you look up the "Tail Volume Coefficient" thread you will find formlae for working it out to suit your particular model. Instructions are wrong surprisingly often, it seems. The last 2 kits I built suggested a CG seriously far aft.

Alasdair



trusno1 -> RE: Black Horse Piper Cub & CG (7/6/2004 3:02:15 AM)

I'm looking for a Black Horse J 3 Piper cub, there hard to find in the USA...Does anyone know who presently has them instock.....Thanks.....Frank



tIANci -> RE: Black Horse Piper Cub & CG (7/8/2004 1:05:35 PM)

Black Horse CG cannot be trusted ... if they say 100-120 you have to keep it about 105mm. Nose heavy planes can land safely. The Cub has problems, I was informed by a friend who has one that the incidence of the wing is not the same as the horizontal stab!



fatboy_flying -> RE: Black Horse Piper Cub & CG (7/21/2004 4:19:35 PM)

I have one of these and have built it as per instructions and my one seems to fly really well.

One of the more experienced flyers from my club took it on its maiden flight and he said he enjoyed flying it.

I have since had a couple of flights in it and bar my lack of experience it seems a stable and fun plane to fly.



MerlinL14 -> RE: Black Horse Piper Cub & CG (7/21/2004 7:32:55 PM)

quote:

I am building the same plane at the moment, and I think the Graupner Piper Cub is 100% identical to the Black Horse model.

timmo, you are 100% correct [;)]



aerobi 46 -> RE: Black Horse Piper Cub & CG (11/19/2007 3:39:37 PM)

i am a beginer an my cub (blackhorse) was very tail hevy take my advice dont listen to the book put the cg 1 3rd of the wing back



Villa -> RE: Black Horse Piper Cub & CG (11/19/2007 4:51:17 PM)

What is the wingspan on this black horse J3- Cub. I have had three J3.-Cubs, all with 71 inch wingspan. I believe that the smaller ones are more difficult to take off and land. The J3-Cub can be a difficult plane to master. They love to snap roll on landing and take off. Mine all have ailerons and a rudder. You have to learn to use the rudder with a J3-Cub. I currently fly a SPAD CorCub J3-Cub. It is a handful and lots of fun. Have had 3-4 bad crashes and still no damage.



da Rock -> RE: Black Horse Piper Cub & CG (11/19/2007 8:04:50 PM)

Pretty amazing.......... this thread is 3 years old. I hope the originator worked it out.

Any CG on any model (or full size as well) can be safely and accurately placed by using this application:

http://www.geistware.com/rcmodeling/cg_super_calc.htm

All you need to do it is a yardstick and the model. And you can take the answer to the bank.



CBJUSS -> RE: Black Horse Piper Cub & CG (4/26/2008 5:21:08 AM)

There is totally wrong wing attach angle,you have to lower the trailing edge about half inch and then she is ****cat



HornetFitter -> RE: Black Horse Piper Cub & CG (5/10/2008 6:29:56 AM)

I have discovered that on my Hangar 9 Cub (80" wingspan) I put the Cg where H9 reccomended by adding 1 oz. of lead to the tail. I flew it a number of times and it was always really hard to get it back on the ground. It just wanted to hover along very slowly... Last week, I had a less than smooth landing and ended up drifting backwards in a moderate headwind. I kind of panicked and let it down quickly from 2 feet or so by getting off the elevator. It nosed over and I swear it sort of snap stalled at the last second. Also, the tail was sagging much lower and indicates that the angle of attack was very high and was very close to stalling, if it had'nt alredy occurred.
I read up on weight & balance to find that it was most likely too far aft. I removed the weight from the tail and test flew it tonight. 3 super smooth landings and zero bounce. It even had some nose down attitude on final, which was opposite to the way it would settle in before. As far as scale flying goes, it was amazing! It was flying at about 10- 15 mph and the tail stayed up on the roll out after landing until there was about 1-2 mph forward speed (winds were calm) ,which was very scale to watch.
I am guessing that Cg is better and easier to fly when it is slightly (5-15%) forward of the published datum.
The Cub sure does like coordinated rudder/ aileron turns too.
Cheerz,



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