Today's Message Index:
----------------------
1. 06:35 AM - Re: HDS Speed Problem (lack of) (Jim Belcher)
2. 03:23 PM - Re: HDS Speed Problem (lack of) (FLYaDIVE)
3. 04:08 PM - Cortec (Gordon Arbeitman)
4. 04:53 PM - Re: HDS Speed Problem (lack of) (Paul Mulwitz)
5. 07:44 PM - Re: HDS Speed Problem (lack of) (Jerry)
6. 08:37 PM - Re: Cortec (JohnDRead@aol.com)
Message 1
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| Subject: | Re: HDS Speed Problem (lack of) |
This is what you'd expect, I think. As I recall, the HDS used smaller, less
draggy wings, to increase airspeed. That means less lift, and less glide.
On Monday 18 October 2010 19:22:35 you wrote:
> <larry@macsmachine.com>
>
> Hi Don,
> I've flown an HDS just like mine with full HD wings and the climb and glide
> are far better, although the cruise speeds are also a bit slower, by 15 -
> 20 mph.
>
> Larry McFarland
>
> -----Original Message-----
> From: owner-zenith-list-server@matronics.com
> [mailto:owner-zenith-list-server@matronics.com] On Behalf Of Don Honabach
> Sent: Monday, October 18, 2010 4:53 PM
> To: zenith-list@matronics.com
> Subject: RE: Zenith-List: HDS Speed Problem (lack of)
>
> --> <don.honabach@pcperfect.com>
>
> >> PPS. He also says that the sink rate is very high when practicing engine
>
> failures...any comments?
>
> I believe this is fairly common on the HDS and I've read others indicate
> that glide rate during power off is high on this model. I'd be curious if
> those flying with HD wings have the same sink rates.
>
> Thanks,
> Don
>
>
> -----Original Message-----
> From: owner-zenith-list-server@matronics.com
> [mailto:owner-zenith-list-server@matronics.com] On Behalf Of Scotsman
> Sent: Sunday, October 17, 2010 10:36 PM
> To: zenith-list@matronics.com
> Subject: Zenith-List: HDS Speed Problem (lack of)
>
>
> Quick question to the list and especially for anyone with an HDS operating
> on 100 hp.
>
> A friend of mine in South Africa is having difficulties getting anywhere
> near the advertised speeds for the HDS on the Zodiac website (135 mph
> cruise). Has anyone else had similar difficulties and if not:
>
> - What prop are you running
> - What hp is your engine
> - What pitch is it set at
> - What is your empty weight
> - What speed to you achieve at sea level with full throttle - straight and
> level
>
> And to anyone else on the list if you have any recommendations for trouble
> shooting please send them through. Any help would be appreciated.
>
> James
>
> PS. I will send though a picture of th aircraft shortly but the owner has
> recently changed prop to see if that will fix the problem and has the spats
> (wheel fairings) on the aircraft.
>
> PPS. He also says that the sink rate is very high when practicing engine
> failures...any comments?
>
> --------
> Cell +27 83 675 0815
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=316128#316128
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
--
=======================================
Jim B. Belcher
BS,MS Physics, Math, Computer Science
A&P/IA
General Radio Telephone Certificate
Instrument Rated Pilot
Retired Aerospace Technical Manager
=======================================
Message 2
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| Subject: | Re: HDS Speed Problem (lack of) |
Jerry, Paul & Gaggle:
I am learning about ROTAX & Jab engines, I do have a lot of experience with
Lycoming.
So when I read about the Static RPM being 5200 & 5400 RPM my ears perked up.
Question: Is there a Static reading required by the manufacture?
Question: What is the Red Line?
With Lycoming the static for an O-320 is 2100 to 2250 RPM.
Red Line in flight is 2700 RPM.
With a two blade aluminum prop the rule of thumb is: Every inch (1") of
pitch your Static will be reduced by 50 RPM.
So, to get the MAX CRUSE you would want the MAX PITCH. YET! You MUST stay
within the "Approved" Static range. And Approved pitch of the GA prop -
DANG the FAA
An example: Let's say you are getting 2350 RPM Static.
By doing the math... 2350 - 2100 [Min Static] = 250 RPM
250 RPM divided by 50 = 5
That means you can increase your Pitch by 5 inches. And still be able to
pass the Min Static Requirement for Annual... OK, I know you guys don't do
an Annual.
Now some say the RPM per Inch is 100
So 250 divided by 100 = 2.5 or an increase of 2.5 Inches.
I like a safety margin - Especially if you are starting with a NEW engine.
Over time the compressions get low and it becomes harder to reach the
required Static.
Some split the difference and use 75 RPM per inch.
Next step:
If you continue with the math there is a percentage difference between Red
Line and Min Static.
For 2100 Static it is: 2100 divided by 2700 = 22.2% lower than Red Line
For 2250 Static it is: 2250 divided by 2700 = 16.6% Lower than Red Line
Can you guess where I am going with this?
Continuing with the math there is a percentage difference between Red Line
and Min Static, that I would like to apply to your engines.
For 5200 Static it is: 5200 divided by 5400 = 3.8% lower than Red Line <--
5400 is that Red Line?
For 5400 Static it is: 5400 divided by 5500 = 1.8% Lower than Red Line <--
55000 is that Red Line?
Those percentages are quite low. There does not seem to be much of a load
on the prop due to pitch. So, next question:
Has anyone EXPERIMENTED with obtaining a MAX Pitch for the Min Static RPM?
That would give you MAX CRUSE.
Of course Altitude / Density Altitude has a bit to do with it also. Those
at high elevation airports or in hot areas and both, have more of a problem
and a less range to play in.
I'm interested in hearing your comments and learning the WHY of those
numbers posted.
Barry
Message 3
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Hi;
I'm just starting work on a Zenith 750 kit and would like to buy some
Cortec. If anyone in the area of Central
Florida has too much Cortec and would like to sell some, please let me
know. Thanks.
Message 4
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| Subject: | HDS Speed Problem (lack of) |
Hi Barry,
I think I have a headache from all those numbers . . .
The Rotax world and ground adjustable propellers is apparently quite
different from the lycosaurus world with fixed metal propellers.
The Rotax 912-ULS is essentially an automotive technology engine with a
gearbox (and liquid cooling, and dual carburetors, dry sump). The critical
numbers are 5800 RPM redline with 5500 maximum continuous power. I don't
remember the definition of how long you can run between 5500 and 5800 but it
is something like a few minutes for takeoff and initial climb. The RPM
numbers refer to the crankshaft rather than the propeller. I think the
gearbox is something in the neighborhood of 2.5 to 1.
The Sensenich ground adjustable propeller I have on the Tecnam Echo doesn't
tell you anything about pitch in inches. It has index marks numbered from 1
to 5. Each is only about a millimeter from the next one so it is very
difficult to get a reading more accurate than 1/2 or maybe 1/4 of an index
mark. You loosen the clamping bolts and rotate the blades (which are kept
at similar angles by some mechanical arrangement) to your desired index mark
and then tighten the clamping bolts and torque them. The nominal setting is
3.5. I simply don't have a clue how this might translate to inches of
pitch.
The gear box changes all the torque issues about minimum static RPM and
maximum pitch. I think in all cases the issue here is whether or not your
engine can produce enough torque with a given pitch to get the plane off the
ground and climbing. This depends not only on the engine and pitch but also
on the weight and wing loading of the plane. If you set the pitch too high
you might get a great cruise speed but crash into the trees at the end of
the runway on takeoff. Also, if the pitch is too high the engine can't turn
it fast enough, because of torque load, to achieve the suggested airspeed.
You just don't get a linear response from pitch changes to cruise speed.
The Jabiru 3300 engine is more like a Lycosaurus engine - direct drive, air
cooled, single carb. Its max. RPM is 3300. I am not aware of a well
defined maximum continuous power setting but there might be one specified by
Jabiru or any given airframe manufacturer. Maximum continuous power might
be set by cooling issues rather than the tendency of the engine to fall
apart due to internal forces.
My experience with the Rotax says the propeller setting can be varied only a
very small amount. Too small a pitch and it gets way too easy to exceed
maximum RPM. Too steep and you can't get the plane off the ground. I
started at the nominal setting of 3.5 and was able to get a full range of
performance choices with only 1/2 to 1 index mark in each direction.
I haven't tried any of this with the Jabiru. My XL with Jabiru has a wood
fixed prop, and I haven't yet started the engine.
I wish I could tell you more, but I'm afraid we just aren't speaking the
same language.
Paul
Camas, Wa
From: owner-zenith-list-server@matronics.com
[mailto:owner-zenith-list-server@matronics.com] On Behalf Of FLYaDIVE
Sent: Tuesday, October 19, 2010 3:20 PM
Subject: Re: Zenith-List: HDS Speed Problem (lack of)
Jerry, Paul & Gaggle:
I am learning about ROTAX & Jab engines, I do have a lot of experience with
Lycoming.
So when I read about the Static RPM being 5200 & 5400 RPM my ears perked up.
Question: Is there a Static reading required by the manufacture?
Question: What is the Red Line?
With Lycoming the static for an O-320 is 2100 to 2250 RPM.
Red Line in flight is 2700 RPM.
With a two blade aluminum prop the rule of thumb is: Every inch (1") of
pitch your Static will be reduced by 50 RPM.
So, to get the MAX CRUSE you would want the MAX PITCH. YET! You MUST stay
within the "Approved" Static range. And Approved pitch of the GA prop -
DANG the FAA
An example: Let's say you are getting 2350 RPM Static.
By doing the math... 2350 - 2100 [Min Static] = 250 RPM
250 RPM divided by 50 = 5
That means you can increase your Pitch by 5 inches. And still be able to
pass the Min Static Requirement for Annual... OK, I know you guys don't do
an Annual.
Now some say the RPM per Inch is 100
So 250 divided by 100 = 2.5 or an increase of 2.5 Inches.
I like a safety margin - Especially if you are starting with a NEW engine.
Over time the compressions get low and it becomes harder to reach the
required Static.
Some split the difference and use 75 RPM per inch.
Next step:
If you continue with the math there is a percentage difference between Red
Line and Min Static.
For 2100 Static it is: 2100 divided by 2700 = 22.2% lower than Red Line
For 2250 Static it is: 2250 divided by 2700 = 16.6% Lower than Red Line
Can you guess where I am going with this?
Continuing with the math there is a percentage difference between Red Line
and Min Static, that I would like to apply to your engines.
For 5200 Static it is: 5200 divided by 5400 = 3.8% lower than Red Line <--
5400 is that Red Line?
For 5400 Static it is: 5400 divided by 5500 = 1.8% Lower than Red Line <--
55000 is that Red Line?
Those percentages are quite low. There does not seem to be much of a load
on the prop due to pitch. So, next question:
Has anyone EXPERIMENTED with obtaining a MAX Pitch for the Min Static RPM?
That would give you MAX CRUSE.
Of course Altitude / Density Altitude has a bit to do with it also. Those
at high elevation airports or in hot areas and both, have more of a problem
and a less range to play in.
I'm interested in hearing your comments and learning the WHY of those
numbers posted.
Barry
Message 5
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| Subject: | Re: HDS Speed Problem (lack of) |
Barry,
I have a Warp Drive 3 blade carbon fiber ground adjustable 72 inch prop.
Like Paul posted the redline on the Rotax is 5800 rpm. The Rotax is
also not to be operated wide open throttle for more than 5 mins. It is
also not to be operated above 5500 rpm. The gear reduction is 2.47:1.
My prop is now set at 14.5 degrees of pitch measured at the tip of the
prop. This gives me 5400 rpm static. I also found that 1 degree change
of pitch makes roughly a 100 rpm in static rpm in the narrow range we
are interested in. This was a number that has been posted on the Rotax
Matronic forum in the past. This rpm means you do not hit redline as
the prop unloads during the takeoff roll, so you don't have to monitor
the tach closely. Also at 5400 rpm I also achieve 5650 rpm WOT at 3000
ft.
I was also a little uncomfortable with the high rpm, but the Rotax is
designed to run in 5000 to 5500 rpm range. At 5000 rpm the Rotax
published fuel burn is 4 gal/hr and at 5500 rpm it goes to 5 gal/hr at
5800 it is 6.1 gal/ hr. I climb at 5400 rpm and usually cruise at
5000rpm. I could cruise a little faster if I ran the Rotax at 5500 rpm,
but I like the 4 gal/hr fuel burn. I also run on auto gas my cost of
operation is really nice when compared to traditional aircraft motors.
This is important to me since I'm retired.
Jerry
On Tue, Oct 19, 2010 at 3:19 PM, FLYaDIVE wrote:
Jerry, Paul & Gaggle:
I am learning about ROTAX & Jab engines, I do have a lot
of=C2-experience=C2-with Lycoming.
So when I read about the Static RPM being 5200 & 5400 RPM my ears perked
up.
Question: =C2-Is there a Static reading required by the manufacture?
Question: What is the Red Line?
Message 6
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Zenith will sell you a quart. do not archive.
Regards, John
CH701 - Colorado - Jabiru 3300
Cell: 719-494-4567
Home: 303-648-3261
In a message dated 10/19/2010 5:09:53 P.M. Mountain Daylight Time,
gordona23@earthlink.net writes:
--> Zenith-List message posted by: Gordon Arbeitman
<gordona23@earthlink.net>
Hi;
I'm just starting work on a Zenith 750 kit and would like to buy some
Cortec. If anyone in the area of Central
Florida has too much Cortec and would like to sell some, please let me
know. Thanks.
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