Jerry Hey wrote:

Paul,  can  you give me the exact locations for the lower center
engine
attach points?   Are there clearance issues I should be aware of?
Thanks,  Jerry

Here is your drawing and a drawing of what I did.
My drawing shows the holes inside the front motor mount brackets
but it will work just as well with them out side the brackets.
Here too is the firewall dimensions that came with the KIS
Cruiser.

Unfortunately I don't have the drawing on the position of the
brackets
here so perhaps Charlie can send you a sketch. Maybe later today I
can get

that

info.

Paul Lamar

If I understand the drawings, it looks like a high posibility of
interference with the Cruiser nose gear and linkage. I would
strongly suggest a mock up to check this - Vance.

I'll do a 3D shortly Vance but mine clears fine with the diagonals
inside the two nose gear brackets. See the pictures I just up
loaded.

And here are yet more pictures.

Paul Lamar

Is there anything that would cause interference if you put the two
interior diagonals outside of the lower gear attach points.  As it
is, it has to be basically a precision fit to make it fit inside
those brackets.  I'd like to make things easier on Jerry if it is
possible.

Charlie
KIS Cruiser 4021

The draw back is the brace angles for the diagonals are less than
ideal. Again
it also tends to put an S bend in the firewall itself when side loads
are applied.
However side loads are small unless you go about kicking the rudder a
lot or do
aerobatics. This is mostly theory as the Kis firewall is very beefy
indeed
in this area and will accept considerable local bending loads.

Paul Lamar

This is giving me a head ache. The engine mount must be completely
adequate for any load generated by rudder forces or aerobatic
maneuvers
  that the plane is designed for plus a considerable safety margin.  I
am certainly not qualified to determine this.  Nor will I build any
engine mount the design of which is not guaranteed by a qualified
engineer.  In this case that means either Paul or Vance.  Regards,
Jerry

Don't worry about it Jerry. The stock bolt hole locations are fine.
I am just anal when it comes to structural design :) Sometimes
I get carried away. Also it is mainly hindsight. I see a structural
design
and automatically start thinking of ways of improving it.
Same thing happened on the Ruttan pushers. I saw no reason to
connect the lower motor mount  tubes to the firewall when there
was a landing gear hard point only inches away. I am always thinking
in terms of the shortest load path. Do it the way Vance designed it.

Paul Lamar

Good!  and running the diagonals just outside of the gear structure is
O.K. too?    Jerry

Sure.

Paul Lamar

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