Hey guys,

I have a Kangaroo with a modified engine mount, so i need to figure out the down thrust angle of the turbine, and from the manual, they only tell you to add washers under the rear bolts of the original mount, which i obviously cant, since my mount is significantly different than stock.

anyway, can anyone tell me what is the maximum and minimum down thrust angle of the turbine ? i will be checking my mount with a Robart incidence meter.
Is there a recommended angle by those who flew this plane before ? please bear in mind im not a begginer pilot.

thanks.

Hi.

I say about 5 deg. up thrust is good. (rear of turbine up)
Take a look at the picture below. The angle of the turbine on that plane was spot on.

The angle doesn't really matter when you have good airspeed, but since the the engine is quite a bit above the centerline it wants to push the nose down when you trottle up on take-off or at low airspeeds.
Most people I see with Roo's have too little up-thrust on the turbine and what usually happens is the when they are on approch and find out they have to add power to reach the runway, the plane is pushed down to the ground by the thrust. This is a classic on aborted take-off's.

OK guys i forgot to mention my mount is much lower, it has been recessed into the fuse.

Shall i put it at a more shallow angle then ?

Not needed with low...or std setting!

Leave it level.

Dave Wilshere

OK guys here are a few pics of the mount to make things more clear, what do you think now ? shall i keep it level or angled ?

My Roo has a lower mount and the turbine is paralel with the wing mounts, and there is not pitch trim change at any speed or throttle setting.

My guesstimate for your particular setup is about 2 degrees of up thrust to minimize the Roo pitch down tendency, or better yet, try to mount the engine lower.. you´ll get a much finer flying machine.

Enrique

erbroens, im not sure how i could mount the engine lower than it is already in the pics ?

i3dm

I would fly it the way it is and see if you like it. You may not need to do anything. It's kind of a personal preference thing anyway.
There is a pic of mine in my gallery. If you'll take a look at the pic, I don't think my turbine is as high in the back as Staale's, but I loved the way it flew.

Don't fix it if it ain't broke.

Well, I think it is worth doing it even if that means punching holes or glueing blocks in your great paint job.. first of all you need to saw that single point mount.. then you put the turbine a little aft and lower. Here are two pics of options you can do it. Of course, this is also a refinement that you can add later, tilting the rear of the turbine up like Sap2000 suggested will make you get almost the same results.


Gary.. I done some mods on my Roo even if I was happy the way it flew. by doing this I ended with a much better and capable airplane. In fact, right now I don´t fancy any other available sport jet design, and that was not the case when I was flying the Roo on its standard configuration.

Enrique

Enrique

I just don't like telling someone that they need to modify their airframe, when in reality, it may fly just fine the way it is. And if I ever own another Roo, I probably won't modify it. Like I said.....personal taste.

Well, if someday you get a holyday in Brazil I will let you do a flight on my Roo.. then you will tell me if you liked them or not!


Enrique

The lower you mount the motor the less up thrust you need. If you have lot of tarmac, you can accelerate slowly and then nose wheel does not tuckin as badly. I put a Hotspot(that expired on the first flight!) mount onto mine and the motor is level. The biggest problem with the high mount is the takeoffs. I flipped mine on the maiden flight. Fortunately only dented ego, scratched wingtips and bent undercarrige. The Wren Supersport on mine is an awsome combo and only carry 1.75 litres of fuel. Does 300 km/h too!

Jet Doctor, your turbine seems to be in about the same height as mine - is it angled ?

Hi i3dm

Mine is not angled. It is parallel to wing mounting tubes. The Wren pushes out in excess of 17 lb of thrust and I have had no steering problems since I changed to the lower mount. I have taken out the Gyro that I used with the high mount now as well.

Zane