Graupner Race Rat C.G.
 

Hello,

Some years ago I brought Race Rat model, and now I lost
almost all documentation that came with it.

Originally it was designed for electric power, but now I converted
it to the OS .15 (2,5 ccm).

I am interested where must be the proper C.G. of this model.
Does someone still flying this model ?

Can't wait to see how it would perform with OS .15, but I am not
very shure about it's C.G.

Best regards,
Kristijan Kljucaric

RE: Graupner Race Rat C.G.
 

Hi, I have a Race Rat with a set of drawing, the CofG is 10mm aft of rear face of shear-web/spar or on the fuselage it is 215mm aft of front face of front bulkhead.
Mine is electric : motor is kyosho magnetic mayhem, 8 cell's RC-2/3SC and prop is 6x6. So far the plane has been spotted at around 141kph, it is quite stressfull plane but it does only last 2min flat out!

RE: Graupner Race Rat C.G.
 

Hello Amaury,

Thank you for response.

As there some period passed by from the time when I started this thread,
I made several test flights to find the proper C.G , and I found out that
this model is not too much critical of C.G.

Finally I left the C.G. at the beginning of the cannopy, like marked at one
picture below.

Also, I made some changes to the Race Rat, and it is quite modified
to gain much more speed.

Now it have Glass/Carbon/Kevlar fuselage, foam/glass/balsa wings
and MH-24 wing profile.

Original one was designed around Graupner Speed 600 DD electric set,
but I could not resist to modify it to glow power.

At first I used OS .15 (2,5 ccm), It flew much faster than electric,
and it performed really great.

After that I finnaly tried OS 32 SX (5.23 cc) engine (BTW a really great engine !)
on 8x8 APC prop.
With this combination the performance is simply outstanding !!! [sm=lol.gif]


Kristijan Kljucaric

RE: Graupner Race Rat C.G.
 

Good looking model! I'm curious - what does the name "ultra brick" mean? In the US, it might describe the glide characteristics. In Zagreb, it may mean something different. :D

RE: Graupner Race Rat C.G.
 

Hi kristijan,

Are you planning to make any more kits to sell?
What is the empty wheight of each part?
Do you make the parts in a mold?
Could you describe me a bit more the lay-up of the wing ( any renforcing?)

Thank you.

RE: Graupner Race Rat C.G.
 

Hello,

I am sorry about this little delay on my reply, as I was away.

Glad to see that someone also still fly the Race Rat model.
It is a really great speed model when slightly modified to the
glow engine, especially if also changed wing profile.
I tried this model with various motor combinations, and the
best I like so far is with an OS .32 SX and 8X7 APC prop,
it fly like rocket !

The original plastic fuselage is of a bad quality material,
and it can be very fragile during the winter, and during the summer
it is just too soft to be safe, especially the rear side where is
horizontal stabilizer.

I have the mold for the Race Rat fuselage, but it is not a direct
replacement.
It is modified for glow engines, and there would be hard to
modify it back to the electric motor, as the front of the fuselage
is altered.
Also there is no anymore air inlets and outlets for electric
motor cooling, as they are completely useless for the glow version.

I don't know what is the weight of the each part, as I never weighted
them.
This is why on the one verisin is label 'ultra brick', one of my friend made
this joke and I simply printed it to the model ... :D
But, the model is not heavy, with engine off it even glides almost like a
glider, and because of this I never bordered myself about the weight.

The wings are of styro-balsa, or of another model styro-abachi, and
there is 80g glass fiber cloth between them.

The fuselage is of glass-carbon-kevlar construction.

Best regards,
Kristijan Kljucaric