Today's Message Index:
----------------------
1. 06:33 AM - Re: Rotax engine mount plate (racerjerry)
2. 07:29 AM - Re: Rotax engine mount plate (Jay Dub)
3. 07:56 AM - Re: Rotax engine mount plate (Stuart Harner)
4. 08:19 AM - Re: Rotax engine mount plate (Dan)
5. 04:26 PM - Re: Rotax engine mount plate (jaydub)
Message 1
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| Subject: | Re: Rotax engine mount plate |
I built my Firestar II around '94 - '96. The plans / instructions page 1 was copyrighted
Dec, 1991.
Engine mount drawing (p15) is dated Jan 1993. This page shows two engine mount
setups; one for the 447, other for 503. Both have two separate nearly identical
mounting plates; but it says the 447 requires circular cutouts between the
two plates to clear bottom of engine case. Otherwise, there is no difference
between the two plates other than required hole spacing.
The "hourglass" shape mounting plate is NOT shown at all in my plans; but that
is what I received in MY kit and it apparently accommodates BOTH engines. In
other words; THERE IS NO DIFFERENCE in engine position.
In any event, don't be overly concerned with engine position / attitude as long
as your prop clearance to boom tube is sufficient. INSTEAD, pay a lot of attention
to WEIGHT an BALANCE calculations; with YOU seated in airplane. Someone
else must read scales. THIS is what can KILL YOU; not a slight difference in
engine position / attitude.
While I am on my soapbox, I need to caution you about first flights in draggy ultralights.
WITH a high mounted engine pusher type ultralight, when you suddenly chop power
- TWO things IMMEDIATELY happen: Nose goes UP and airspeed goes DOWN, quickly
stalling the airplane. You MUST be spring loaded to PUSH STICK FORWARD in order
to maintain airspeed and prevent a stall.
Regardless of prior flight experience, it's best to have at least SOME instruction
in a similar configuration two-place pusher type ultralight. A CUB, for example;
reacts MUCH differently.
Jerry King
--------
Jerry King
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=510630#510630
Message 2
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| Subject: | Re: Rotax engine mount plate |
Hi Jerry,
Thanks for the reply. So your plans engine plate must be different than the plates
I have from about 1990. I don't know if you could see in the photos mine are
just 2 plates. but the rear one has a bit of a notch machined out of it for
the gearbox drain. Mine don't appear home-made at all nor do mine have any clearance
holes. Plane #1 kit may be older than 1990 as I know when I built a CGS
Hawk in 1991 I had bought the frame kit first, the fabric kit second, and the
engine kit last. I don't know if Kolb also sold them that way too? If so my
fuselage/engine mounts could be earlier than the engine.
My big concern with the engine position is solely that it puts the prop much closer
(2.5-3 inches) to the aileron tubes because the engine sits further forward
in relation to the trailing edge of the wing. I did measure the distance between
the main spar tang and the drag link mount on both my new wings and the
old wings and that dimension didn't change nor does it appear to change from the
drag link attachment to the trailing edge of the wing. That means the engine
is further forward for sure putting the prop that much closer to the aileron
tubes. If the prop hits the aileron tubes that could kill me that's what I am
concerned with.
In my newer manual it does state that if you are using an ivoprop (which flex forward
and aft) you must add the 2.5" prop spacer which I bought and installed
with my ivoprop from plane #1. I didn't get a spacer with plane #1 so that might
be why. I had thought maybe that had gotten lost but maybe the earlier models
didn't need it.
I'm well aware of the importance of w&b and how to measure and calculate (tomorrow
I'll be helping a buddy do his kitfox) as I have done them many times for
new and altered homebuilts and have done hundreds of w&b calculations in my career
as a professional bush pilot because I had to do them for every flight. I'm
well aware of the differences between flying GA planes and light pushers as
I also have over 450 hours in a 447 powered CGS Hawk which is very similar to
the Firestar. I appreciate the heads up but I recall vividly how different they
fly.
Jay
Sent:Sunday, April 16, 2023 at 7:33 AM
From:"racerjerry" <gnking2@verizon.net>
To:kolb-list@matronics.com
Subject:Kolb-List: Re: Rotax engine mount plate
I built my Firestar II around '94 - '96. The plans / instructions page 1 was copyrighted
Dec, 1991.
Engine mount drawing (p15) is dated Jan 1993. This page shows two engine mount
setups; one for the 447, other for 503. Both have two separate nearly identical
mounting plates; but it says the 447 requires circular cutouts between the two
plates to clear bottom of engine case. Otherwise, there is no difference between
the two plates other than required hole spacing.
The "hourglass" shape mounting plate is NOT shown at all in my plans; but that
is what I received in MY kit and it apparently accommodates BOTH engines. In other
words; THERE IS NO DIFFERENCE in engine position.
In any event, don't be overly concerned with engine position / attitude as long
as your prop clearance to boom tube is sufficient. INSTEAD, pay a lot of attention
to WEIGHT an BALANCE calculations; with YOU seated in airplane. Someone
else must read scales. THIS is what can KILL YOU; not a slight difference in engine
position / attitude.
While I am on my soapbox, I need to caution you about first flights in draggy ultralights.
WITH a high mounted engine pusher type ultralight, when you suddenly chop power
- TWO things IMMEDIATELY happen: Nose goes UP and airspeed goes DOWN, quickly
stalling the airplane. You MUST be spring loaded to PUSH STICK FORWARD in order
to maintain airspeed and prevent a stall.
Regardless of prior flight experience, it's best to have at least SOME instruction
in a similar configuration two-place pusher type ultralight. A CUB, for example;
reacts MUCH differently.
Jerry King
--------
Jerry King
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=510630#510630
Message 3
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| Subject: | Re: Rotax engine mount plate |
I'll add a tiny bit to the prop spacer issue.
Bryan at Kolb told me that with the IVO prop the spacer was a must on a
2013 Firefly with a Rotax 447. The reason was the flex of the prop made
it at least slightly possible that the prop could hit the aileron tubes
and the spacer eliminated that possibility.
However, I went with the Warp Drive and it is is much stiffer. We had
quite a conversation about it and after a while Bryan recommended that I
use the spacer on the Warp Drive as well. His reasoning was that it will
help lower the pulsations of air on the trailing edge if the prop is a
little farther back. This should help with the longevity of the covering
and in general just put less stress on the plane and lower transmitted
noise as well.
I followed his advice and can say it all works better than I expected.
It does sound like somewhere along the line they did move the engine
forward, probably to help W&B, but that created the need for the spacer.
Tradeoffs, always tradeoffs....
Stuart
On 4/16/23 09:28, Jay Dub wrote:
>
> Hi Jerry,
> Thanks for the reply. So your plans engine plate must be different than the plates
I have from about 1990. I don't know if you could see in the photos mine
are just 2 plates. but the rear one has a bit of a notch machined out of it for
the gearbox drain. Mine don't appear home-made at all nor do mine have any
clearance holes. Plane #1 kit may be older than 1990 as I know when I built a
CGS Hawk in 1991 I had bought the frame kit first, the fabric kit second, and
the engine kit last. I don't know if Kolb also sold them that way too? If so my
fuselage/engine mounts could be earlier than the engine.
>
> My big concern with the engine position is solely that it puts the prop much
closer (2.5-3 inches) to the aileron tubes because the engine sits further forward
in relation to the trailing edge of the wing. I did measure the distance
between the main spar tang and the drag link mount on both my new wings and the
old wings and that dimension didn't change nor does it appear to change from
the drag link attachment to the trailing edge of the wing. That means the engine
is further forward for sure putting the prop that much closer to the aileron
tubes. If the prop hits the aileron tubes that could kill me that's what I
am concerned with.
>
> In my newer manual it does state that if you are using an ivoprop (which flex
forward and aft) you must add the 2.5" prop spacer which I bought and installed
with my ivoprop from plane #1. I didn't get a spacer with plane #1 so that
might be why. I had thought maybe that had gotten lost but maybe the earlier models
didn't need it.
>
> I'm well aware of the importance of w&b and how to measure and calculate (tomorrow
I'll be helping a buddy do his kitfox) as I have done them many times for
new and altered homebuilts and have done hundreds of w&b calculations in my
career as a professional bush pilot because I had to do them for every flight.
I'm well aware of the differences between flying GA planes and light pushers
as I also have over 450 hours in a 447 powered CGS Hawk which is very similar
to the Firestar. I appreciate the heads up but I recall vividly how different
they fly.
>
> Jay
>
>
>
>
>
>
> Sent:Sunday, April 16, 2023 at 7:33 AM
> From:"racerjerry" <gnking2@verizon.net>
> To:kolb-list@matronics.com
> Subject:Kolb-List: Re: Rotax engine mount plate
>
> I built my Firestar II around '94 - '96. The plans / instructions page 1 was
copyrighted Dec, 1991.
>
> Engine mount drawing (p15) is dated Jan 1993. This page shows two engine mount
setups; one for the 447, other for 503. Both have two separate nearly identical
mounting plates; but it says the 447 requires circular cutouts between the
two plates to clear bottom of engine case. Otherwise, there is no difference
between the two plates other than required hole spacing.
>
> The "hourglass" shape mounting plate is NOT shown at all in my plans; but that
is what I received in MY kit and it apparently accommodates BOTH engines. In
other words; THERE IS NO DIFFERENCE in engine position.
>
> In any event, don't be overly concerned with engine position / attitude as long
as your prop clearance to boom tube is sufficient. INSTEAD, pay a lot of attention
to WEIGHT an BALANCE calculations; with YOU seated in airplane. Someone
else must read scales. THIS is what can KILL YOU; not a slight difference in
engine position / attitude.
>
> While I am on my soapbox, I need to caution you about first flights in draggy
ultralights.
>
> WITH a high mounted engine pusher type ultralight, when you suddenly chop power
- TWO things IMMEDIATELY happen: Nose goes UP and airspeed goes DOWN, quickly
stalling the airplane. You MUST be spring loaded to PUSH STICK FORWARD in order
to maintain airspeed and prevent a stall.
>
> Regardless of prior flight experience, it's best to have at least SOME instruction
in a similar configuration two-place pusher type ultralight. A CUB, for
example; reacts MUCH differently.
>
> Jerry King
>
> --------
> Jerry King
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=510630#510630
>
>
>
>
>
Message 4
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| Subject: | Re: Rotax engine mount plate |
Jay, I got an email meant for Jerry. Just thought you should know. Dan
Kolb Mark ll
-----Original Message-----
From: Jay Dub
Sent: Sunday, April 16, 2023 10:28 AM
Subject: Re: Kolb-List: Rotax engine mount plate
Hi Jerry,
Thanks for the reply. So your plans engine plate must be different than the
plates I have from about 1990. I don't know if you could see in the photos
mine are just 2 plates. but the rear one has a bit of a notch machined out
of it for the gearbox drain. Mine don't appear home-made at all nor do mine
have any clearance holes. Plane #1 kit may be older than 1990 as I know when
I built a CGS Hawk in 1991 I had bought the frame kit first, the fabric kit
second, and the engine kit last. I don't know if Kolb also sold them that
way too? If so my fuselage/engine mounts could be earlier than the engine.
My big concern with the engine position is solely that it puts the prop much
closer (2.5-3 inches) to the aileron tubes because the engine sits further
forward in relation to the trailing edge of the wing. I did measure the
distance between the main spar tang and the drag link mount on both my new
wings and the old wings and that dimension didn't change nor does it appear
to change from the drag link attachment to the trailing edge of the wing.
That means the engine is further forward for sure putting the prop that much
closer to the aileron tubes. If the prop hits the aileron tubes that could
kill me that's what I am concerned with.
In my newer manual it does state that if you are using an ivoprop (which
flex forward and aft) you must add the 2.5" prop spacer which I bought and
installed with my ivoprop from plane #1. I didn't get a spacer with plane #1
so that might be why. I had thought maybe that had gotten lost but maybe the
earlier models didn't need it.
I'm well aware of the importance of w&b and how to measure and calculate
(tomorrow I'll be helping a buddy do his kitfox) as I have done them many
times for new and altered homebuilts and have done hundreds of w&b
calculations in my career as a professional bush pilot because I had to do
them for every flight. I'm well aware of the differences between flying GA
planes and light pushers as I also have over 450 hours in a 447 powered CGS
Hawk which is very similar to the Firestar. I appreciate the heads up but I
recall vividly how different they fly.
Jay
Sent: Sunday, April 16, 2023 at 7:33 AM
From: "racerjerry" <gnking2@verizon.net>
Subject: Kolb-List: Re: Rotax engine mount plate
I built my Firestar II around '94 - '96. The plans / instructions page 1 was
copyrighted Dec, 1991.
Engine mount drawing (p15) is dated Jan 1993. This page shows two engine
mount setups; one for the 447, other for 503. Both have two separate nearly
identical mounting plates; but it says the 447 requires circular cutouts
between the two plates to clear bottom of engine case. Otherwise, there is
no difference between the two plates other than required hole spacing.
The "hourglass" shape mounting plate is NOT shown at all in my plans; but
that is what I received in MY kit and it apparently accommodates BOTH
engines. In other words; THERE IS NO DIFFERENCE in engine position.
In any event, don't be overly concerned with engine position / attitude as
long as your prop clearance to boom tube is sufficient. INSTEAD, pay a lot
of attention to WEIGHT an BALANCE calculations; with YOU seated in airplane.
Someone else must read scales. THIS is what can KILL YOU; not a slight
difference in engine position / attitude.
While I am on my soapbox, I need to caution you about first flights in
draggy ultralights.
WITH a high mounted engine pusher type ultralight, when you suddenly chop
power - TWO things IMMEDIATELY happen: Nose goes UP and airspeed goes DOWN,
quickly stalling the airplane. You MUST be spring loaded to PUSH STICK
FORWARD in order to maintain airspeed and prevent a stall.
Regardless of prior flight experience, it's best to have at least SOME
instruction in a similar configuration two-place pusher type ultralight. A
CUB, for example; reacts MUCH differently.
Jerry King
--------
Jerry King
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=510630#510630
Message 5
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| Subject: | Re: Rotax engine mount plate |
Thanks Stuart,
>From looking at the bracing differences on the rear engine mount U channel, I'm
guessing they moved the engine forward so they could better brace the U channel
for the rear mounts.
I remember reading something in the archives that people added bracing to that
channel down to the boom tube/fuselage bolt on both sides when using a higher
powered engine. I'm thinking maybe the factory moved it so it could be better
braced.
You can see how it's braced on my plane #2 vs no extra bracing on plane #1 in the
photos.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=510638#510638
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