Scott Gettings wrote:

Gentlemen,

I'm extremely interested in using a 13B in my Glass Goose, which is a
composite, pusher biplane amphibian.

<<<<<< MAJOR SNIP>>>>>>>>>>>>>>

Thanks again for comments and participation.

Scott
Gettings

As you move the main mounts further forward the load on the main mounts gets
higher and higher. The reason this is so is the front mount is now called
upon to hold the front of the engine down. In effect you are cantilevering
the engine off the main mounts. The loads on the main mounts are now
the sum of the engine weight plus the tension loads in the front mounts.

Perhaps the approach you should take in the Glass Goose is use one
large rear mount as far back as you can get it and two widely separated
front mounts using the 12A front cover to react the prop torque.
The single rear mount will then accept only 90% of the engine weight.
Beef up the structure a bit if the skin is thin in that area.

In that case you cpuld  use a Barry Controls 2003-12 for the rear mount.

Paul Lamar

The approximate pylon dimensions are: 16" wide (I.D.) at the aft 
end of the 13B block, and down to a max of 14" wide at the
motor plate location.  (The engine sits higher than the pylon, 
so width higher up is not an issue.)  Going farther forward,
there is 24" at the center of the engine.  My structural 
engineering buddies say that a cantilevered bridge supporting the motor
plate area should be possible, going forward and down to the lower 
wing shear web for vertical support.  However it would only
be 14" wide, giving two mounts a maximum of about 11" center-to-center.  
Is this wide enough to be considered for two mounts?
If not, as Paul suggested, the motor plate area can only 
support a single mount.

If a single rear mount is used, how wide apart should the 
forward mounts be?  As wide as possible?  Would 1"x2" 6061  be
adequate for a forward beam from the case to two mounts?

Scott Gettings

As wide as possible. Yes a 1 by 2 6061 T6 forward beam would be adequate.
It might not be high enough to bolt to a 12A front cover however.
You might want to make it 1/2 by 2.5 or 1/2  by 3. Do you have a 12A
front cover?

Three mounts are a minimum. There is nothing wrong with four mounts
as long as you realize the aft two take 90% of the load if they
are located near the motor plate or rear end housing. Moving them forward
of this location increases the load on these mounts as well as the front 
mounts. I am sure your structural engineering buddies are aware of this 
as long as they know you are using a gear box and prop.

Paul Lamar
 
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