Hangar 9 Carden 50cc Extra 300 flying in a nose high attitude.
 

Posting this for a hobby friend of mine. He recently bought a Hangar 9 Carden 50cc Extra and fitted it with an EME 60 with the stock muffler and the model flew great. He opted to fit a tuned pipe so he modded the lower half of the fuse making a tunnel to accomodate the pipe and also relocated the tail mounted rudder servo forward using a pull pull arrangement.

The model was rebalanced to ensure that the CG was as it was before, but now the model flies in a slight nose high attitude when flying level and requires a touch of down elevator trim to do so. He is pretty much at his wits end trying to figure up what might be the cause of the change in the model's flying attitude as nothing else was changed :confused: and we would certainly appreciate your thoughts on this. Thanks.

Assuming that the mods have made no changes to the angles between the tailplane and wing, and now the thing flies 'nose up' it would infer that whatever AOA it needed before the mod to fly straight and level has changed, and the wing needs more AOA or 'lft' than before. Perhaps the fuselage contributed quite a bit of lift prior to the mod, and cutting the tunnel has changed the amount of lift generated by the fuselage? I can't see moving a servo changing anything aerodynamically.
Evan, WB #12.

I believe that the nose is lifting some more now, inducing an aerodynamic nose-up pitch that your friend needs to compensate with some down-elevator trim.

For static balance, that additional lift forward of the CG (due to fuse reshape and/or tuned pipe) cannot be detected.

In other words, it is like if your friend had moved the wings forward a little bit, resulting in the CG being a little more aft than before (reducing the stability margin and getting closer to a tail-heavy condition).

The peculiar thing is that the nose up will increase with the speed of the airplane; so, it may not be noticeable for landing.

What did rebalancing require?

Are you positive the CG was corrected after the modifications to be where it had been before the mods?

Needing the trim you describe could come from a couple of different sources. The trim is needed because the horizontal tail is now carrying more weight due to a more aft CG. The tail's lifting ability has changed due to different airflow being encountered from the change in fuselage configuration and/or exhaust location.

Tailheavy---------

Hi Karol,

The tunnel and pipe change the weight distribution quite a bit to the rear. Are you certain it was rebalanced the same? Regardless, you might want to check with the maker regarding where to place the cg. It sounds tail heavy to me.....

Hello

Just thought I would add my 2 cent, the model has a 4inch opening in the first former that allows access for a canister with no tunnel built in.Out the box the plane was tail heavy on the aft range of the CG, this is with 2 2cell A123 2100mah up in the nose of the engine box

. The EME 60 which was awesome on the pipe in another plane was not so on the regular muffler with this 19lb plane, as such I made the decision to build the tunnel and install the pipe. Now with all the trying of different mufflers with this un-usual inside structure of the cowl I had to cut out 90% of the bottom of the cowl to fit the mufflers and as a result this now gives full access to the tunnel opening.

I forgot to mention that its a carbon fiber pipe and now the nose falls off quite nicely on the inverted 45 upline