George Lendich wrote:
Paul,
I was looking at the Kis firewall to day and took notice of
the
Thrust
Line and felt if you needed extra room at the top, you could
drop
that
thrust line 3 to 4 inches, if it was OK'd by the
designer.
Just a suggestion!
George (down under)
Vance is the designer. What about that Vance?
IMHO the landing gear is not long enough :)
On the other hand some time Vance flips flops :) Quote!
"Paul - I have a problem understanding why you want a smaller
prop
dia.
With the 2.85 reduction and the curves you have provided, the
tip
speeds
are very
modest. Smaller diameter is going to have a perf penalty
everywhere,
and
most
heavily at static and climb."
Paul Lamar
All things in moderation. The thrust line on the Cruiser is not
carved
in
stone
but dropping it down without lengthening the gear would put the
prop
dia
one would like with this size plane and power - in jeopardy for
prop
strikes. Raising the nose gear height would probably involve
significant
(tho quite possible) hardware changes - Mains could rise by
blocking
in the gear fuselage cut our. This is why I view the concentric
nature
of
the
planetary reduction a minor disadvantage - Our TR-1 with the
Subaru,
and Ross box just shortened his prop tips with a slight drainage
depression out by the hanger, - Vance
Vance and Paul,
Sorry Vance, I was just thinking engine installation at that point
in
time
and forgetting that the Kis is a KIT with all premade parts
supplied. It
struck me at the time that the thrust line was quite hight
compared
to
other
designs.
Would larger diameter wheels help or would that also add to other
problems.
One thing I know is the problem of changes to existing designs -
been
there
done that, on other projects.
George (down under)
"thrust line quite high compared to other designs"?? What other
designs?
the
location is quite classic for flat six and four aircraft engines
and the
line relative
to the windsheild is probably within an inch or so of all RVs,
Cessna
Piper
etc. Vance
Not an RV4 for sure Vance. Tracy can clear an alternator on top of
the
engine using the stock RV4 cowl. There are other RV's out there with
just as much room on top. Now on Lancair 320, 360 and legacy I'll
probably
agree.
The Tailwind is also pretty tight.
Paul Lamar
Paul and Vance,
I don't want to start an argument and was only trying to help! as the
top of
the Kis installation is very tight, as you have stated so many times
before
Paul.
Like you said the RV's have a better chance of fitting everything in
especially the manifold, over the top of the engine.
To state some figures the Tailwind is tight with it's thrust line at
6.75"
( I believe) - which is exactly the same as the Vision.
Having said that the Kis is 8.5" - a good 1.75" lower.
Advice to me is that the lower the engine weight the better!
Engine weight lower = thrust line lower, unless you use an off-set
PSRU.
Like you said Vance 'thrust lines are not set in cement' - and in the
case
of the Vision the Thrust line can be anywhere from 6.75" to 10.75" or
4 "
lower. I would suggest this MIGHT also be the case for the Tailwind,
Jerry.
Having said this very few planes are designed for the Rotary
installation,
except for the Cosman I don't know of any others which specifically
target
the Rotary installation.
To my knowledge most aircraft are designed to accommodate the
Lycoming or
Continental - industry standard !?
The Kis being a relatively new aircraft, I thought might consider
automotive
installations and make the thrust line lower, with the facility to
raise it,
thereby providing for more prop clearance, with sufficient in the
worst case
scenario. I was surprised to find this wasn't the case.
Anyhow there you have it, all the information available to me - to my
way of
thinking if you need the room and you can lower the thrust line, the
lower
engine weight is better.
George (down under)
George, When you say the thrust line is at a certain height we need
to know the reference water line or else what are we talking about.
To talk about the Tailwind the center of thrust is 10 inches below the
top longerons and 15 inches above the bottom longerons at the firewall
station of course. This does not tell us much about clearance above the
engine because the firewall top is above the top longerons and the
bottom is below the bottom longerons. If I needed another half inch
above the engine, I would add more height to the firewall. Nearly
every TW built in the last ten years has had the firewall height
extended. I added 2.5 inches to mine. It makes the windshield lay
down for better aerodynamics and provides room on top of the engine too.
I would not hesitate to lower or raise the engine to get the room
needed. The limiting factor is prop clearance. We are going to be
generating so much power with the p ports and turbos and 2:85s that
the 3 blade prop will be a necessity anyway. That ought to get back a
couple of inches of ground clearance.
Jerry
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