Model Forum / Radio Controlled / Air Models / November 2005

You'll need to select a motor mount, e.g., a Great Planes, and then
follow its instructions (you find the instructions on a PDF at their
site). Generally, there will be a template with the mount that you'll
line up with vertical and horizontal center lines drawn on your
firewall; however, this is the simplest case. If you're in doubt and
can't fathom the instructions, you might contact the mfg of your model
(Sig?).

For the two degrees of down thrust, you can build a plywood plate that
is epoxied over your original fire wall, or you can build  a new
firewall. I don't like the idea of washers, but it too is a solution.
I'm surprised you have to build in the down thrust. On many models,
this is already built into the firewall.

I can't comment about Saito engines, but I suspect they are good
quality. Frankly I prefer OS; however, you should follow the engine
size, either 2 or 4-stroke, recommended by the model maker. An
overpowered model is often difficult to trim out.

Ciao,

Mr Akimoto

Ted shuffled out of his cave and grunted these great (and sometimes not
so great) words of knowledge:

Yes, that is correct.  I suggest either a mount designed especially for
the Saito 72/82 or a Great Planes adjustable mount.  If you get the GP
mount be sure you get the one with the long mounting beams since a 4
stroke sits further forward from the firewall than a 2 stroke.

Also it says I will need 2 degrees of downthrust. Do I get that by

There are several ways of doing this.

You can make a shim and epoxy it behind the motor mount.

Redo the firewall in the plane (I would not suggest this since it is too
easy to screw it up and then you will have bigger problems).

Use washers.  I suggest the washers and there are 2 ways to do them.

If you look in the fastener section of your local hardware store you
will find a variety of washers in different thicknesses.  You can mount
them behind the motor mount (between the motor mount and the firewall).
 If you decide to go this way get the largest diameter washer in the
thickness you need.

The last method (suggested method ) is to put washers between the rear
mounting lugs (beams attached to the engine ) and the motor mount
itself.  This way if you need to adjust the amount of down thrust it is
a simple matter to change the washers.

Before mounting the motor mount give the firewall and surrounding areas
a coat of thinned epoxy (I thin it about 10% by volume with acetone ).
This will fuel proof the area and also harden the firewall somewhat so
the washers will be less likely to imbed themselves into the wood.

Also I am going to use a Saito 82A 4

Saitos are awsome engines.  The 82 will have plenty of power to haul the
plane.

A couple of things with 4 strokes - USE A TACH TO SET IT UP ( there are
VERY FEW people that can accurately set a 4 stroke by 'ear' ), another
thing is that if the engine is not producing smoke at all speeds it is
running lean, and the last thing is that Saitos can easily handle higher
nitro fuel (30%+ nitro ) so you don't need to be afraid a high nitro
fuel.  I suggest 15% nitro.  In any case be sure you have a minimum of
16% oil.  Many people say to only run synthetic oils.  I run a
synthetic/castor mix.  Yes, the castor does leave some staining on the
muffler, but I prefer the knowledge that IF I get a lean run, the castor
is going to give me some protection.

My Saito 72 is very happy with 15% nitro and produces excellent power.
At present I have it in a 60 size Bingo (early 4 Star clone ) and it
will do just about anything I want along with a decent vertical (not
unlimited, but decent ).  I am running an APC 13x6 prop on the engine,
and normally fly at 1/2 - 2/3 throttle.

With a Saito (most 4 strokes for that matter ) you will either need to
get a linkage for the throttle OR reverse the throttle servo in the
transmitter since the linkage works backward from a 2 stroke.

  Hope this helps.