Today's Message Index:
----------------------
1. 03:12 AM - slingshot thrust line (Ted Cowan)
2. 05:13 AM - Re: Another video.. (Thom Riddle)
3. 06:53 AM - Re: Re: Another video.. (Jack B. Hart)
4. 06:56 AM - proper thrustline (Mike Welch)
5. 07:17 AM - Re: Another video.. (Thom Riddle)
6. 09:13 AM - Re: proper thrustline (John Hauck)
7. 09:44 AM - Re: Slingshot thrust line/angle/HKS (McCarthy Tom)
8. 10:54 AM - Re: Kolb-List Digest: 12 Msgs - 10/24/10 (Bob Green)
9. 05:21 PM - Re: SPOT Working (Roger Lee)
10. 10:46 PM - Re: slingshot thrust line ()
Message 1
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| Subject: | slingshot thrust line |
I am going to jump in here because I believe the SS has the engine thrust
line too far back. I hope you get this pic of my SS with the 912. The 582
had about the same thrust line as my 912 only adjusted for the power. If
you dont raise the back of the engine on the mount you will be virtually
pushing the nose over. The entire airframe will be fighting. You MUST
raise the rear mounts from 3/4 to maybe 7/8 of an inch (one guy went more
than that) in order to correct the angle of attack. I bet you have a really
heavy stick or a lot of bungee stretch to compensate. At 7/8 at the rear of
the mounts, you will be able to fly virtually hands off at your regular
cruise rate and not have to fight it on take off. I bet you got a handful
when you firewall the engine at take off. Not just my opinion, fact on this
one and if you dont believe, well, fight it in the air. Raise the rear of
the engine a little at a time and you will see the difference in the first
quarter inch. You will notice the angle of the blade in relation to the
boom. This really works. Trust me. Ted Cowan, Slingshot, 912UL, zoom zoom
Message 2
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| Subject: | Re: Another video.. |
Richard,
I wish it were that simple. The Jab motor mount attaches to the standard Kolb motor
mount plates with matching plates which would require beveled shims under
the front and rear mounts to be done right, as well as the correct length AN
bolts. I'd like to get close to the right answer the first try so I don't have
to fabricate several different angle/thickness shims and purchase several different
length AN bolts.
I think I'll just assume that the correct angle for the thrust line is parallel
to the horizontal stabilizer and go with that. That angle has got to be better
than what it is now.
--------
Thom Riddle
Buffalo, NY (9G0)
Kolb Slingshot SS-021
Jabiru 2200A #1574
Tennessee Prop 64x32
Everyone is entitled to his own opinion, but not his own facts.
Daniel Patrick Moynihan
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=316943#316943
Message 3
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| Subject: | Re: Another video.. |
Thom,
I agree with Richard Pike. If one assumes the wing aoa is six degrees and
your engine is set 3.5 degrees on top of that, and using the cosine of 9.5
degree, it indicates that 98.6 % of your thrust is pushing in the direction
of the relative wind. The other right angle thrust component is being used
to help hold up the plane. Agreed 1.5% loss is not very much and your plane
should climb better than if the thrust vector was set in the direction of
the relative wind. By reseting the engine, you should gain some cruise
speed, and reduce cruise power factor and fuel flow with less trim.
The question is, is it worth the effort to capture a couple of horsepower?
Jack B. Hart FF004
Winchester, IN
Message 4
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| Subject: | proper thrustline |
Thom=2C
(I changed the subject line to correctly reflect the topic)
One year ago=2C our fellow comrade John Ratcliffe and I had several priva
te messages
regarding his wing's incidences on his MkIII Xtra. John drew up a nice com
puter generated
stick figure Xtra with ALL the appropriate digital angles that the Xtra is
supposed to have.
(tailfeathers=2C boomtube=2C motor mount=2C etc)
One thing he and I were NOT completely sure of is=3B if you rotate that s
tick drawing for
say...the tailfeathers to be zero degrees=2C this will give you a certain n
ew reading for the
rest of the planes angles.
Now=2C what if you rotate that stick figure instead from the main wing's
as you pivot point=2C
to where the main wings incidence is now zero? Will that give you an exact
change in the
tailfeather's incidence as you got with the main wings? I am NOT sure.
What I'm getting at is that it MAY not be as simple as adding or subtract
ing one angle setting
from another by simple mathematics. Frankly=2C I'd need proof that by simp
ly rotating the airplane
from the wheels as a pivot point that ALL other angles change in an equal a
mount compared to
if you rotated the plane by the main wings.
Between John and I=2C we never really did figure out if it mattered. May
be it doesn't matter whether
you pivot the plane by the wheels=2C or the tail=2C or the main wings (to g
et all the different incidence
readings).
What I'm getting at is unless I saw for my own eyes that by simple additi
on and subtraction
you could figure out one reading compared to another=2C I would have to phy
sically reposition
the plane=2C and take a reading=2C before I'd accept that that were true!
Maybe it's just me=2C but I
want proof!!
Your example of=3B
Tail Boom = 5 degrees (front higher)
Horizontal Stabilizer = 5 deg. (front higher) parallel to boom
Wing Bottom = 12 degrees
Engine Thrust Line = 15.5 degrees
Therefore=2C relative to the Horizontal Stabilizer....
Wing Bottom has a 7 degrees incidence (12 - 5)
Engine Thrust line has 10.5 degrees incidence (15.5 -5)
Unless I saw this was the case=2C I wouldn't automatically and necessaril
y believe it.
One thing I can guarantee I'd do=2C if it were me=2C I'd go with the fact
ory recommendations on
how to set up your planes angles. On the MkIII=2C you set the motor mount
to zero=2C and all other
angles go from there. I imagine the SlingShot does too.
After all=2C unless you first establish that the motor mount is zero=2C a
nd then take all your reading=2C
for all you know=2C maybe the engine thrust line is correct and the main wi
ng's incidence is wrong!
The photos supplied by Chris show his plane in the initial factory recomm
ended position=2C where
all other incidences are to be set. I'd do that first=2C and then determin
e where to proceed. (You
probably were going to do this anyway)
I could be completely in the dark on this=2C but that's how I see it. (
you appear to have a digital
level) I also wouldn't change a thin washer without taking precise (!!) re
adings of where
everything is at the moment!!
This is a good topic=2C with lots of experiences pilots weighing in. Pro
per Kolb flying surface settings
are always an important topic for me.
Mike Welch
MkIIICX
Message 5
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| Subject: | Re: Another video.. |
Jack,
I did the math too and that is the reason I've not been in a hurry to do the work,
but think I will eventually get around to it.
The other problem with this that Chris alluded to is that the point and angle at
which the thrust is acting is so far aft of the CG that it results in a significant
nose down pitching moment when adding power, more so I believe than if
the thrust was parallel to relative wind. The net result of this torque about
the CG is an effectively heavier wing (at CG) requiring more tail down force
to counter. So the loss in direct thrust is only part of the net negative effect.
Relieving the wing of the extra thrust angle induced load and the extra HS
loading is worthwhile also. Perhaps I am visualizing this all wrong, so if you
would like to correct me with your excellent vector diagrams, I'm all ears and
eyes. Or if I am correct, your confirmation is welcome too :-).
When I get around to doing it, I'll report the qualitative and quantitive results,
if any.
--------
Thom Riddle
Buffalo, NY (9G0)
Kolb Slingshot SS-021
Jabiru 2200A #1574
Tennessee Prop 64x32
Everyone is entitled to his own opinion, but not his own facts.
Daniel Patrick Moynihan
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=316962#316962
Message 6
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| Subject: | Re: proper thrustline |
Mike W/Gang:
I agree with the statement below, build the Kolb according to plans and
instructions. Test fly it, get some hours on it, get the feel of the
airplane, then make minute changes. However, make one change at a time,
then test fly to verify what you changed.
Many of you all are building Kolbs, have never flown one, and, for sure,
have never flown the airplane you are building. Making a lot of changes
based on what someone else did to their airplane, especially another
model Kolb, is not wise, in my humble opinion.
You will not know how your particular Kolb will fly until you fly it.
However, if built to plans, it will fly well. Maybe need a tiny bit of
tweaking, but not much to please the builder/pilot.
When experimenting with angles of thrust, don't forget the attitude of
the engine on the ground, with the engine stopped, will not be the same
as the angle of thrust when the engine is flying at and producing cruise
power. Depending on the engine, Rotax two or four stroke, or other
engines, the prop will be turning either clockwise or counter clockwise.
The thrust will cause the rear of the engine to rise and depress the
front of the engine, more left front or right front, depending on which
way the prop turns. Depending on the desity of the Lord Mount (on a
standard Kolb configured engine mount) the change in angle of thrust
will be significant. If you doubt me, then tie down your Kolb, while
observing the engine, go to full power and watch the engine change
position on the mounts as you change power settings.
Recommend you insure you have the most dense Lord Mounts on your
airplane no matter what engine you are flying with.
Take care,
john h
mkIII
Rock House, Oregon
One thing I can guarantee I'd do, if it were me, I'd go with the
factory recommendations on
how to set up your planes angles.
Mike Welch
Message 7
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| Subject: | Re: Slingshot thrust line/angle/HKS |
Thom,
I have done a lot of experimenting with thrust angle and thrust height
on my slingshot. Most of it started after I installed the Rotax 532 on
my Slingshot and received help and advice from Ted Cowen. If you email
me your ph# and a good time to call, I will talk about it off list due
to the amount of content involved. As far as the testing with the
Slingshot/HKS is going, I'm kind of at a stand still. I'm having
problems with EGT and CHT going to high. I think it is due to my custom
exhaust or a ram air effect due to a forward carb style. Work and
weather are slowing progress down as well. If it were not for the high
temp problems, my experimenting would be complete. I have turned the
gear box down, added more height to the rear mount bringing it up about
1 1/2" total, so the thrust line is parallel to the flight line, and
the 68" 3 blade Warp prop is about 3/4" from the boom tube. The result
is very nice. I will report the actual numbers when I confirm with a
GPS. Early numbers are 4800rpm, cruise at 55mph, 5800rpm, cruise at
80mph, with climb 700fpm, with only slight back pressure through out the
power range(no trim tab yet)
Tom McCarthy
N514 TM Zenith 601HD
N414 TM Kolb Firestar
N863 GB Kolb Slingshot
Message 8
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| Subject: | RE: Kolb-List Digest: 12 Msgs - 10/24/10 |
So glad your friend survived the car crash. Muchas gracias por la informacin en
cuanto a SPOT. Cul Kolb tienes?
Tengo (en via de construccin) una Mark IIIX.
Chow.
Bob Green
Time: 07:22:17 AM PST US
Subject: Kolb-List: SPOT Working
From: "henry.voris" <henry_voris@yahoo.com>
22oct10
Tuxtla Gutierrez, Mexico
Fortunately at the time of the crash the emergency helicopter was overhead. So
by the time we reached the wreck they had cut our driver out of the car and evacuated
him to the hospital in Tuxtla (unconscious with a broken leg, bruised
and cut).
I have included Before and After photos...
Worth what you paid for it... and I hope your mileage will differ...
Aloha
--------
Henry
Firefly Five-Charlie-Bravo
Message 9
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| Subject: | Re: SPOT Working |
I'm flying to Yuma, AZ again tomorrow, Tuesday at 0830 Mountain Time or AZ. time
today. You can track me as I go. I will leave at 0830 and arrive in Yuma at
approximately 1030.
I come home Friday late afternoon at 1530 hrs. and will be back in Tucson at 1730
hrs. mountain time.
You can follow me by clicking on the link above where it has my Spot Tracker link.
http://share.findmes...4WO25eB0VkBu5Iv
--------
Roger Lee
Tucson, Az.
Light Sport Repairman - Maintenance Rated
Rotax Repair Center
520-574-1080
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=317034#317034
Message 10
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| Subject: | Re: slingshot thrust line |
Yep that worked for me on the MK111c. Packed the back up with 2 washers.
There is a slight pitch up when you throttle back from cruse rpm by about
200 rpm . The pitch up is so slight that it is no more than a "be aware this
will happen" it is normal, when some one is flying the Kolb for the first
time . I was trying to get the prop away from the boom at the bottom to
reduce noise. Not sure that worked , but I like the way it fly's now . I
have never measured the angles . Just changed things a little and went
flying .
Down under
MK111c
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