Today's Message Index:
----------------------
1. 03:35 AM - rum rum (Ted Cowan)
2. 04:37 AM - Re: rum rum (Richard Girard)
3. 04:38 AM - Re: dynamic balancing (zeprep251@aol.com)
4. 05:16 AM - prop tip speed and noise (Thom Riddle)
5. 05:16 AM - Re: dynamic balancing/Center Section/Cockpit Noise (John Hauck)
6. 06:03 AM - Re: prop tip speed and noise (John Hauck)
7. 06:43 AM - Re: prop tip speed and noise (Jack B. Hart)
8. 06:57 AM - Re: prop tip speed and noise (lucien)
9. 07:05 AM - Re: prop tip speed and noise (robcannon)
10. 07:30 AM - Re: prop tip speed and noise (lucien)
11. 07:38 AM - Re: prop tip speed and noise (Thom Riddle)
12. 07:58 AM - Re: rum rum (b young)
13. 08:07 AM - Re: Re: prop tip speed and noise (Richard Girard)
14. 08:26 AM - Re: prop tip speed and noise (Thom Riddle)
15. 09:07 AM - Re: rum rum (John Hauck)
16. 09:56 AM - Re: prop tip speed and noise (robert bean)
17. 10:49 AM - Reason for use of Silk Thread (jerb)
18. 01:46 PM - Re: Reason for use of Silk Thread (frank.goodnight)
19. 02:06 PM - Re: Reason for use of Silk Thread (Bob)
20. 02:08 PM - Ted's harmonic noise (Mike Welch)
21. 02:53 PM - Re: rum rum (b young)
22. 03:54 PM - Re: Reason for use of Silk Thread (frank.goodnight)
23. 04:56 PM - Re: rum rum (zeprep251@aol.com)
24. 04:59 PM - Re: Reason for use of Silk Thread (robert bean)
25. 05:05 PM - seeking Firefly dimensions (Bob Kravis)
26. 05:05 PM - Re: Re: prop tip speed and noise (Richard Girard)
27. 05:22 PM - Re: Reason for use of Silk Thread (John Hauck)
28. 05:22 PM - Re: rum rum (John Hauck)
29. 06:40 PM - Re: Kolb-List Digest: Spray foam 02/02/10 (dsmald@aol.com)
30. 07:04 PM - Re: prop tip speed and noise (Jack B. Hart)
31. 07:09 PM - Re: rum rum (Richard Pike)
32. 08:03 PM - Re: Re: rum rum (John Hauck)
33. 08:04 PM - Any one know anything about this outfit (jerb)
34. 10:00 PM - Pre-construction advise wanted (Nick Cassara)
Message 1
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I have synchronized the carbs four times. I tied it down and ran it until
it made the harmonics and carefully opened just one carb. stalled and
skipped, did not stop it. I pulled the filter on both and carefully lifted
one barrel at a time and still no good effect. I do not believe it is the
carbs. I was always wondering if the timing on one side is somehow
different but that is not how the timing works. It would have to be
different on each set of plugs but I dont think that would do it either.
Wondered if I had one piston not doing its job or lagging but compression
check says they are all pretty much the same. Had to pretty much just suck
it up and live with it. Friend has a plane coming up here with a Hurth.
Says if I fly with him I wont be able to HEAR my plane. Talked to Ronny
Smith and he says to just live with it. (same answer I got two years ago).
Says it is a combination of airframe, engine, set-up, exhaust and blades. I
dont really buy that. I think that any sound can be changed, no matter
where it comes from. Besides, I have went from no prop spacer to four inch,
three inch and now a two inch and that works about best for flying. SAME
NOISE. I guess I am going to see about a muffler from the exhaust people.
May not stop the rum rum but mayb, just maybe it will be less audible. What
the heck, only another six to eight hundred bucks. No big thing, right?
Sorry for the longoo. my bad. Thanks everyone. Ted Cowan oh yeah, not
really going to squirt that foam in my wings, just thinking out loud.
Message 2
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Ted, Perhaps TNK can tell you who supplies the engine mount dampers. You
could see if they have different hardnesses of the rubber. You also might
try making up some small bags of lead shot and lay them on various frame
components to damp out any possible source of the vibration. How do the
strut and wing mount holes look and fit?
Rick Girard
On Wed, Feb 3, 2010 at 5:12 AM, Ted Cowan <tc1917@bellsouth.net> wrote:
>
> I have synchronized the carbs four times. I tied it down and ran it until
> it made the harmonics and carefully opened just one carb. stalled and
> skipped, did not stop it. I pulled the filter on both and carefully lifted
> one barrel at a time and still no good effect. I do not believe it is the
> carbs. I was always wondering if the timing on one side is somehow
> different but that is not how the timing works. It would have to be
> different on each set of plugs but I dont think that would do it either.
> Wondered if I had one piston not doing its job or lagging but compression
> check says they are all pretty much the same. Had to pretty much just suck
> it up and live with it. Friend has a plane coming up here with a Hurth.
> Says if I fly with him I wont be able to HEAR my plane. Talked to Ronny
> Smith and he says to just live with it. (same answer I got two years ago).
> Says it is a combination of airframe, engine, set-up, exhaust and blades. I
> dont really buy that. I think that any sound can be changed, no matter
> where it comes from. Besides, I have went from no prop spacer to four inch,
> three inch and now a two inch and that works about best for flying. SAME
> NOISE. I guess I am going to see about a muffler from the exhaust people.
> May not stop the rum rum but mayb, just maybe it will be less audible. What
> the heck, only another six to eight hundred bucks. No big thing, right?
> Sorry for the longoo. my bad. Thanks everyone. Ted Cowan oh yeah, not
> really going to squirt that foam in my wings, just thinking out loud.
>
>
Message 3
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| Subject: | Re: dynamic balancing |
Rob/all,
I used a sound absorbing 1/2 thick foam(densofoam) from High tech Foams,on
every surface of the of the center cover.It has a peel and stick side,whi
te color and black on the other.Doubled on the spar carry through.I really
believe it helps.G.Aman MK3C 2200 Jab
510hrs
-----Original Message-----
From: robert bean <slyck@frontiernet.net>
Sent: Tue, Feb 2, 2010 9:12 am
Subject: Re: Kolb-List: dynamic balancing
Don't do it. -At least if you are considering the "stuff" in the little
cans.
I tried it in a motor vehicle once and it wicks and holds moisture. Ruste
d out faster than ever.
BB
On 2, Feb 2010, at 8:50 AM, Mike Welch wrote:
> By the way, has anyone ever put the
> spray in foam into the wing panels close to the root through the inspect
ion
> holes? Ted
Ted,
Although the foam might be a good idea, you do have to be careful. Ther
e are 3 grades of the stuff (at least three that I know of). The grades
vary by how much expansion pressure they have. The weak grade is for win
dow gaps, etc. It doesn't distort the structure. The strong grade can an
d will spread apart the structure gap, like in a door frame gap. It can
actually ruin the door fits to where it won't close anymore.
If you were to try using this foam, I'd recommend the middle expansion
foam, and try it in a test area first. It would not be wise just to star
t spraying blobs of foam everywhere, only to find you've now got wings wit
h bulgy muscles. :-(
Mike Welch
Do not archive
Your E-mail and More On-the-Go. G229/direct/01/' target='_new'>Sign up
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href="http://www.matronics.com/Navigator?Kolb-List">http://www.matronics
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Message 4
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| Subject: | prop tip speed and noise |
This has nothing to do with Ted's rum-rum but rather the amount of noise (db levels)
from props.
I don't know how much of the prop noise one gets in the cabin of a Kolb is due
to prop tip speed but believe that the tip speed is a major contributor to it.
I normally fly my Slingshot w/ Jabiru 2200A engine at 80 mph which is 2,712 rpm.
The 64" diameter prop at this speed has a rotational tip speed of 516 mph
plus the advance speed of 80 mph equals 596 mph total tip speed.
My memory (which could be wrong) is that John H normally cruises at similar airspeed
at 5,000 rpm with 72" WD prop and 2.43 PSRU which gives a rotational tip
speed of about 440 mph plus the 80 mph equals about 520 mph total tip speed.
Therefore my prop tip speed at normal cruise is about 14-15% higher than John H's.
I have no idea how much more noise (db level) that difference makes but do
know subjectively that when I fly at an engine speed (
--------
Thom Riddle
Buffalo, NY
Kolb Slingshot SS-021
Jabiru 2200A #1574
Tennessee Prop 64x31
We refuse to believe this country, so powerful to defend its citizens abroad, is
unable to protect its citizens at home.
- Ida B. Wells
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=284696#284696
Message 5
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| Subject: | Re: dynamic balancing/Center Section/Cockpit Noise |
That is a good looking center section. I'd like to have one like that.
I think I finally realize why my mkIII is louder in the cockpit than it
was prior to building a new center section a couple years ago.
To save weight, and give it a longer service life, I used no lexan,
covered it with .025 aluminum sheet.
My previous center section was constructed with lexan, then overlapped
with .020 aluminum sheet.
Now I realize the lexan was probably reducing some of the engine and
prop noise, and/or the sheet metal is amplifying the noise.
Guess I need to get me some of that Densofoam and cover the inside of
the top of my center section.
Thought my ANR headset was going south, my hearing was getting worse,
and my radio was not putting out enough volume, when it may be I have
constructed a very efficient drum to sit under.
john h
mkIII
titus, alabama
Rob/all,
I used a sound absorbing 1/2 thick foam(densofoam) from High tech
Foams,on every surface of the of the center cover.It has a peel and
stick side,white color and black on the other.Doubled on the spar carry
through.I really believe it helps.G.Aman MK3C 2200 Jab
Message 6
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| Subject: | Re: prop tip speed and noise |
> I don't know how much of the prop noise one gets in the cabin of a Kolb
is due to prop tip speed but believe that the tip speed is a major
contributor to it. I normally fly my Slingshot w/ Jabiru 2200A engine at 80
mph which is 2,712 rpm. The 64" diameter prop at this speed has a rotational
tip speed of 516 mph plus the advance speed of 80 mph equals 596 mph total
tip speed.
>
> My memory (which could be wrong) is that John H normally cruises at
> similar airspeed at 5,000 rpm with 72" WD prop and 2.43 PSRU which gives a
> rotational tip speed of about 440 mph plus the 80 mph equals about 520 mph
> total tip speed.
>
> Therefore my prop tip speed at normal cruise is about 14-15% higher than
> John H's. I have no idea how much more noise (db level) that difference
> makes but do know subjectively that when I fly at an engine speed (
>
> --------
> Thom Riddle
I think you fired a round before you were ready. By the way, I am flying
with a 71" prop now. Have flown with 70 and 72" props. John W flew with a
68" prop. Wonder if that helped give him a little more edge on cruise speed
than me with the larger props?
Every notice how quiet a tractor 912ULS with Warp Drive Taper Tip Prop is
compared to the same engine and prop on a Kolb? Same engine, same prop,
same rpm, but none of the nasty noise we have deal with in our pusher.
Got an idea most of the noise is being produced as the prop blades gnaw away
at the air as it is disturbed by the engine, wing, flap leading edge,
inboard end of flap, anything that disturbs the air in front of the prop
blades.
Only way I know to fix that is protect myself from it. I don't know how
else to reduce the noise except convert to tractor configuration.
john hauck
mkIII
titus, alabama
Message 7
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| Subject: | Re: prop tip speed and noise |
At 05:16 AM 2/3/10 -0800, you wrote:
>
>This has nothing to do with Ted's rum-rum but rather the amount of noise
(db levels) from props.
>
Thom & Kolbers,
Propellor tip shape can be a noise contributor too. See:
http://jackbhart.com/firefly/firefly100.html
and:
http://jackbhart.com/firefly/firefly111.html
This is a nice way to reduce cockpit noise without adding any weight.
Jack B. Hart FF004
Winchester, IN
Message 8
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| Subject: | Re: prop tip speed and noise |
My titan is I think the only plane I've ever flown that was louder inside the plane
than my FSII was. Even with the 3.47 C box turning the 68" WD slow, the prop
noise in the cockpit was absolutely deafening. I could hardly even hear the
cooling fan scream above it.
There was no extension and the prop blades were only a few inches away from the
back of the cage and the TE of the wing.
Talk about rum-rum..... but vibration-wise it was completely silky smooth and gave
really good performance. I just stuffed earplugs in under the headset and
turned the radio up as loud as it would go.
Wish I'd had my telex 50-D back then. It's a miracle-worker on noise.
The other titan on the field is configured almost exactly like mine and I can hear
him all over town when he's up. he's still audible at the airport when I hear
him call the tower that he's made it outside the class D. I've been told I'm
also similarly audible from miles away.
We have a Lockwood Aircam with 2 912ULS's based here as well and I can hear him
pretty good too.
There're a couple tractor 912 equipped LSA's that fly in here from time to time
and they're so quiet they almost sound like they're running electric motors.
And one of those has a 3 blade prop.
I think it's that big ol airplane in front of the prop disk that does it for us....
LS
--------
LS
Titan II SS
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=284713#284713
Message 9
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| Subject: | Re: prop tip speed and noise |
When I was researching which prop to put on my mark II HKS with a 3:47 gearbox
I talked to alot of people about airplane noise. My goal was to be as quiet as
the 85hp fleet canuck (cub like canadian plane), that flies out of my home strip.
What I learned was that it is a combination of tip speed and pitch which determines
noise. (and pusher or tractor) Basically the smaller the "bite"out of
the air, each blade takes, the quieter you are.......so, more blades, less diameter,
less rpms, = quieter. I have been told by pretty much everyone that hears
my plane that it is the quietest plane they have ever heard......it sounds
really nice!!!
It has a four blade 68 inch powerfin, with the 3;47 gearbox. Does the 912 not
have the option for a higher ratio gearbox ?
Although I realize performance is rather subjective, I am very happy with my
combination. Empty weight = 550 lbs HP = 60 Solo climb = around 1000 fpm.
Cruise = faster than vne of 75 mph.
...............so, I believe now that Kolbs can be made quiet, with enough money
and effort put into them........providing you can slow the prop down. I'm
not sure what the gains would be seen by simply adding more blades with reduced
pitch, without slowing the prop down, but I'd love to hear about someone experimenting
with that.
At the Wallaby ranch in Florida they use Dragonfly ultralights to tow hangliders,
and they use two stacked three blade Ivo props, which they say gives them
the best combo of quietness and thrust (they dont care about airspeed). cheers,
Rob Cannon
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=284714#284714
Attachments:
http://forums.matronics.com//files/021_389.jpg
Message 10
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| Subject: | Re: prop tip speed and noise |
robcannon wrote:
> When I was researching which prop to put on my mark II HKS with a 3:47 gearbox
I talked to alot of people about airplane noise. My goal was to be as quiet
as the 85hp fleet canuck (cub like canadian plane), that flies out of my home
strip.
> What I learned was that it is a combination of tip speed and pitch which determines
noise. (and pusher or tractor) Basically the smaller the "bite"out of
the air, each blade takes, the quieter you are.......so, more blades, less diameter,
less rpms, = quieter. I have been told by pretty much everyone that
hears my plane that it is the quietest plane they have ever heard......it sounds
really nice!!!
> It has a four blade 68 inch powerfin, with the 3;47 gearbox. Does the 912 not
have the option for a higher ratio gearbox ?
> Although I realize performance is rather subjective, I am very happy with
my combination. Empty weight = 550 lbs HP = 60 Solo climb = around 1000 fpm.
Cruise = faster than vne of 75 mph.
> ...............so, I believe now that Kolbs can be made quiet, with enough
money and effort put into them........providing you can slow the prop down.
I'm not sure what the gains would be seen by simply adding more blades with reduced
pitch, without slowing the prop down, but I'd love to hear about someone
experimenting with that.
> At the Wallaby ranch in Florida they use Dragonfly ultralights to tow hangliders,
and they use two stacked three blade Ivo props, which they say gives them
the best combo of quietness and thrust (they dont care about airspeed). cheers,
Rob Cannon
When I was learning to fly trikes, the trainer I flew in had a 582 with the stacked
6-blade IVO prop on it, with 4:1 C box. I think the prop on it was louder
than my FSII was with 3-blade 3.47:1 C box. It was one of the loudest combos
I think I'd ever heard on a 582 in fact. I have no idea why that combination is
so popular on tow planes. Must be really thrusty?
More blades means a higher frequency noise which adds to percieved loudness. So
I'd say that probably needs to be taken into account too.
I love my powerfin 3-bladed (70" model F) on my 912ULS titan, but it's louder than
the WD (68") that was on the plane for a while by a significant margin.
The WD taper tip is actually a pretty quiet prop in flight compared to something
like our powerfins which have the big square blade ends. I wouldn't use anything
other than a WD on a Kolb personally, tho I love my powerfin the WD is just
the ideal there.....
LS
--------
LS
Titan II SS
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=284719#284719
Message 11
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| Subject: | Re: prop tip speed and noise |
Jack,
Your measured difference of 1 db between 2 and 3 blades of the same diameter and
rpm was interesting to learn and unexpected, by me at least. I wonder if the
lessor pitch was the actual cause of the slightly reduced noise level or the
different beat. I suspect it was the change in blade pitch, as Rob stated. My
prop is cut in a scimitar shape so the tip angle is a lot more laid back than
the modified tip on yours.
John,
No question that the pusher configuration is MUCH noisier than tractors, but I
can't control that factor as long as I'm flying a Slingshot. What I am thinking
about though is going to a shorter prop with more pitch like Gary has on his
Jab powered mkIIIX. BUT if additional pitch also adds to the perceived noise
then it might be for naught.
--------
Thom Riddle
Buffalo, NY
Kolb Slingshot SS-021
Jabiru 2200A #1574
Tennessee Prop 64x31
We refuse to believe this country, so powerful to defend its citizens abroad, is
unable to protect its citizens at home.
- Ida B. Wells
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=284720#284720
Attachments:
http://forums.matronics.com//files/scaled_jabiru_rt_rear_175.jpg
Message 12
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I have synchronized the carbs four times. I tied it down and ran it until
it made the harmonics and carefully opened just one carb.
>>>>>>>>>>>>>>>>>
Just thinking out loud here... could it be a possibility that it is the
positioning of the prop blades in relation to the pulse from the exhaust?
The gear box having a 2.27 to 1 reduction will put the prop blades at a
slightly different position every time it fires. Cyl 1 for example will
fire every 2 turns of the engine,,,,, and the .27 will be quite close to
the .333 of a turn for the next blade to be in position, multiply this by
4 with all four cylinders firing, and rum rum.... if an exhaust pulse is
echoed off a blade as it is going past, then no echo when no blade is not
present. Maybe if you could terminate the exhaust further away from the
prop arc.
Just a thought.
Boyd Young
mkiii
Message 13
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| Subject: | Re: prop tip speed and noise |
Rob, For what It's worth I have the exact same engine and prop setup on my
trike. One of the comments I get at fly ins and EAA chapter events is that I
can't be heard in the pattern. Personally I think it really is prop tip
speed as much as anything else. I have a 4:00 to 1 C gearbox with a 66" 3
blade Warp Drive on my 582 Mk III and my neighbor across the runway
complements me on how quiet it is, too.
Rick Girard
On Wed, Feb 3, 2010 at 9:04 AM, robcannon <leecannon@telus.net> wrote:
>
> When I was researching which prop to put on my mark II HKS with a 3:47
> gearbox I talked to alot of people about airplane noise. My goal was to be
> as quiet as the 85hp fleet canuck (cub like canadian plane), that flies out
> of my home strip.
> What I learned was that it is a combination of tip speed and pitch which
> determines noise. (and pusher or tractor) Basically the smaller the
> "bite"out of the air, each blade takes, the quieter you are.......so, more
> blades, less diameter, less rpms, = quieter. I have been told by pretty
> much everyone that hears my plane that it is the quietest plane they have
> ever heard......it sounds really nice!!!
> It has a four blade 68 inch powerfin, with the 3;47 gearbox. Does the 912
> not have the option for a higher ratio gearbox ?
> Although I realize performance is rather subjective, I am very happy
> with my combination. Empty weight = 550 lbs HP = 60 Solo climb = around
> 1000 fpm. Cruise = faster than vne of 75 mph.
> ...............so, I believe now that Kolbs can be made quiet, with
> enough money and effort put into them........providing you can slow the prop
> down. I'm not sure what the gains would be seen by simply adding more
> blades with reduced pitch, without slowing the prop down, but I'd love to
> hear about someone experimenting with that.
> At the Wallaby ranch in Florida they use Dragonfly ultralights to tow
> hangliders, and they use two stacked three blade Ivo props, which they say
> gives them the best combo of quietness and thrust (they dont care about
> airspeed). cheers, Rob Cannon
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=284714#284714
>
>
> Attachments:
>
> http://forums.matronics.com//files/021_389.jpg
>
>
Message 14
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| Subject: | Re: prop tip speed and noise |
Rick,
Assuming your cruise rpm is about 5800 your prop tips are rotating at only 284
mph plus your airspeed of 50-60 mph I would guess for a total tip speed of about
330 mph or so. That is a whopping 45% less than my tip speed. That has got
to be a BIG factor.
How does it sound to you while flying it?
--------
Thom Riddle
Buffalo, NY
Kolb Slingshot SS-021
Jabiru 2200A #1574
Tennessee Prop 64x31
We refuse to believe this country, so powerful to defend its citizens abroad, is
unable to protect its citizens at home.
- Ida B. Wells
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=284728#284728
Message 15
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> Just thinking out loud here... could it be a possibility that it is
the
> positioning of the prop blades in relation to the pulse from the exhaust?
> The gear box having a 2.27 to 1 reduction will put the prop blades at a
> slightly different position every time it fires. Cyl 1 for example will
> fire every 2 turns of the engine,,,,, and the .27 will be quite close to
> the .333 of a turn for the next blade to be in position, multiply this
> by
> 4 with all four cylinders firing, and rum rum.... if an exhaust pulse is
> echoed off a blade as it is going past, then no echo when no blade is not
> present. Maybe if you could terminate the exhaust further away from the
> prop arc.
>
> Just a thought.
>
> Boyd Young
> mkiii
Boyd/Gang:
I don't know if it is caused by exhaust and prop or not.
If Cowan is running a 912UL with a three blade WD prop and Titan Exhaust,
why aren't all combos like this, with many of them operational in the field,
having the same problem?
Some time ago I related the problem Ronnie Collins had with his Sling Shot
powered by a 582 turning a 3 blade Warp Drive. The harmonic racket on
Ronnie's Sling Shot is exactly the same as the harmonic racket produced by
Cowan's Sling Shot. I have listened to both of these aircraft fly. The
harmonic in both aircraft is loud and very much the same. May be a little
difference because of different gear box ratios, but hard to tell the
difference.
Ronnie's harmonic was caused by disturbed air produced by loose fabric which
billowed up on the inboard aft corner of the right wing. If this is what is
causing Cowan's Sling Shot harmonic, then the left inboard aft corner of the
wing would be suspect because the 912 turns opposite the 582.
After securing the loose rib stitching in Ronnie's wing, the harmonic
mysteriously disappeared. To me, this proves if part of the wing surface,
or other part of the aircraft, produces disturbed air, it can also produce
harmonic noise.
I flew Ronnie's Sling Shot before the fabric was reattached and before we
discovered that this was the problem. Not only was the harmonic loud in the
cockpit, it also created a vibration that could be felt in the airframe. It
was bad enough I would not fly the airplane unless the problem was fixed for
fear of damaging the aircraft.
I believe I shared with the List what I would do if it was my airplane.
1 - Pull the gear box and insure it is shimmed correctly and snugly as
possible. Shimming controls how the dogs perform to overcome torsional
vibration. Could loose shimming cause the blades to constantly change phase
enough to produce the harmonics that are so loud and so obvious?
2 - Some part of the aircraft is producing disturbed air, which, in turn, is
producing the harmonic as the prop blades drive through it.
This is an isolated problem with Cowan's engine, prop, exhaust system
combination. There are many, many more like combos flying with no
harmonics.
Many years ago when I was flying with my 912UL 80 hp, I picked up a harmonic
in the airframe at cruise flight, 5000 rpm. Immediately I suspected the
prop, so I insured all blades were flying with the same pitch. Did not
help. Warp Drive props normally do not have a balance problem. My harmonic
did not feel like an imbalanced prop. Flew down to Ronnie Smith's, pulled
the gear box, to find washers and shims had worn over the hours. Reshimmed
as snugly as possible and the harmonic also disappeared.
Hope Cowan can get his problem corrected. A problem like that would turn me
off to the flying that airplane. I got turned off to my airplane when the
exhaust system I was using caused different engine performance on different
days. Take off and climb 5400 normally. Next morning take off and it would
only pull 5200. Drove me nuts until I replaced the Rick Thomasson STE
Exhaust with a new Titan Exhaust. First take off with the Titan Exhaust and
I had a new engine. Now, every time I fly the 912ULS performs exactly the
same, 5400 climb. Again, I look forward to flying my airplane.
john hauck
mkIII
titus, alabama
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| Subject: | Re: prop tip speed and noise |
Try a dovetail saw for that precise cutting job.
BB
On 3, Feb 2010, at 9:17 AM, Jack B. Hart wrote:
>
> At 05:16 AM 2/3/10 -0800, you wrote:
>>
>> This has nothing to do with Ted's rum-rum but rather the amount of noise
> (db levels) from props.
>>
>
> Thom & Kolbers,
>
> Propellor tip shape can be a noise contributor too. See:
>
> http://jackbhart.com/firefly/firefly100.html
>
> and:
>
> http://jackbhart.com/firefly/firefly111.html
>
> This is a nice way to reduce cockpit noise without adding any weight.
>
> Jack B. Hart FF004
> Winchester, IN
>
>
>
>
>
Message 17
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| Subject: | Reason for use of Silk Thread |
What is the purpose of placing a piece of silk thread along with
sealant when joining the two cast halves of an aircraft engine. Is
this done on all engines or just Continental and Lycoming, what about
4-stroke Rotax.
jerb
Message 18
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| Subject: | Re: Reason for use of Silk Thread |
Hi JERB<
Many years ago my favorite A&P told me , that on a good set of cases
the silk thread is all the seal needed. and with other sealant
[ permatex type ] there was a danger
that the excess that is squeezed out inside the engine MAY lodge in a
oil passage and cause serious problems. I don't know if this is the
gospel or not. However I have put
a couple of continental engines together using just #60 silk thread
and they did not leak. I think it was # 60 I remember that it looked
awfully small to me. Sorry I can't remember better
but it was a long time ago.
Frank Goodnight
Firestar2
Brownsville, TX
On Feb 3, 2010, at 1:44 PM, jerb wrote:
>
> What is the purpose of placing a piece of silk thread along with
> sealant when joining the two cast halves of an aircraft engine. Is
> this done on all engines or just Continental and Lycoming, what
> about 4-stroke Rotax.
> jerb
>
>
Message 19
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| Subject: | Re: Reason for use of Silk Thread |
One of the classic reasons is to assure a minimum thickness of bond
line...just like a scrim cloth in a composite bond....may be others as well.
Bob
----- Original Message -----
From: "jerb" <ulflyer@verizon.net>
Sent: Wednesday, February 03, 2010 12:44 PM
Subject: Kolb-List: Reason for use of Silk Thread
>
> What is the purpose of placing a piece of silk thread along with sealant
> when joining the two cast halves of an aircraft engine. Is this done on
> all engines or just Continental and Lycoming, what about 4-stroke Rotax.
> jerb
>
>
>
Message 20
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| Subject: | Ted's harmonic noise |
Ted=2C Kolb guys=2C
In my years of experience (or approx. 684 hours) I have had to chase down
several odd noises. I learned early on that a noise comes from an exact s
pot. It isn't some nebulous auditory output that appears out of thin air
=2C like an echo from a distant canyon!!
If you want to find a noise=2C secure a hose "CLOSE" to where you think t
he noise is coming from. If that location doesn't nail it=2C then relocate
the hose. It may be helpful to keep a journal of various location=2C plus
assign a number from 1-10 on the scale of noise. The noise will either be
louder or more quiet. Keep moving the hose until it's output is dead-on.
I know darn well many of you mechanic types have found dozens of engine n
oises and countless other noises with this method. It ain't exactly brain
surgery.
My hearing is all but gone. For me to watch TV it has to be so loud the
neighbors complain (little joke=2C but not much). Maybe it is 40% of when
I was younger. My wife darn sure complains. When I was living in my shop l
ast year (while building my house) and didn't have access to my TV headphon
es in storage=2C I hooked up a 1/2" plastic hose to be near one of the TV's
speakers. Sound came in loud and clear=2C almost too loud. Then I had to
turn the TV way down or it blasted me out!!
Wherever a noise originates=2C a hose will transmit that noise originatio
n point to your ears better than almost ANY other method. Even with my dim
inished hearing=2C I'd be shocked if a hose didn't pinpoint the noise. D
one it a lot=2C can't see why it wouldn't work for Ted.
Mike Welch
deaf basterd
_________________________________________________________________
Hotmail: Powerful Free email with security by Microsoft.
Message 21
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Boyd/Gang:
I don't know if it is caused by exhaust and prop or not.
If Cowan is running a 912UL with a three blade WD prop and Titan
Exhaust,
why aren't all combos like this, with many of them operational in the
field,
having the same problem?
john hauck
mkIII
titus, alabama
>>>>>>>>>>>>>>>>.
john / gang
when the air is still and smooth and when you feel like you are in a
suspended state, totally relaxed with just one finger on the control
stick, (you know my kind of flying), you hear every little noise and
feel every vibration. I have heard the rum rum a tiny bit at certain
rpm. I have never felt anything, if I take my headset off the rum rum
is overcome by the other noise. I am trying to paint a picture in your
mind here,,,,, if you have to think about anything, an extra movement
in your arm to right the plane from a thermal that rolls the plane 5
deg. just the noise of the gears turning in my head, any and all of
these distractions will cause me to loose track of the rum rum that I
hear
now if the rum rum is large or loud enough that you cant get away from
it,,,,, that is another story.
I don't know if you could plot the rotation of the prop as a sign wave
maybe with a different line for each prop. then post a vertical line
through the sign waves for every pulse of the exhaust, then see what
the timing would be at the given 2.27 to 1 timing of the gear box. then
add to the mix the position of the blades as they pass through disturbed
air caused by the airframe etc.
just hit delete, this is kind of out on a limb.
Boyd young
mkIII Utah
do not archive
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| Subject: | Re: Reason for use of Silk Thread |
Hi JERB,
I cut myself off before I was finished. I don't know if the silk
thread was used on any engines other continental , I built up a 65
and a 85 it may be that with modern chemistry, and with better machine
work the rules have changed. Don't know anything about Rotax [wish I
did]
Frank
On Feb 3, 2010, at 1:44 PM, jerb wrote:
>
> What is the purpose of placing a piece of silk thread along with
> sealant when joining the two cast halves of an aircraft engine. Is
> this done on all engines or just Continental and Lycoming, what
> about 4-stroke Rotax.
> jerb
>
>
Message 23
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Boyd,
Tried that too.I think it helped some.Can maybe see the exhaust in this ph
oto.
G.Aman
-----Original Message-----
From: b young <by0ung@brigham.net>
Sent: Wed, Feb 3, 2010 9:58 am
Subject: RE: Kolb-List: rum rum
I have synchronized the carbs four times. I tied it down and ran it until
it made the harmonics and carefully opened just one carb.
>>>>>>>>>>>>>>>>>
Just thinking out loud here... could it be a possibility that it is th
e
positioning of the prop blades in relation to the pulse from the exhaust?
The gear box having a 2.27 to 1 reduction will put the prop blades at a
slightly different position every time it fires. Cyl 1 for example will
fire every 2 turns of the engine,,,,, and the .27 will be quite close to
the .333 of a turn for the next blade to be in position, multiply this
by
4 with all four cylinders firing, and rum rum.... if an exhaust pulse is
echoed off a blade as it is going past, then no echo when no blade is not
present. Maybe if you could terminate the exhaust further away from the
prop arc.
Just a thought.
Boyd Young
mkiii
========================
===========
========================
===========
========================
===========
========================
===========
Message 24
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| Subject: | Re: Reason for use of Silk Thread |
That's an oldie. I did that on an 85 continental once and maybe an A65. Don't
remember if it helped.
Those engines had a lot of places to leak: pushrod tubes were common. Could only
re-swage them so many times.
O-ring at the tach drive will seep just enough to dirty the belly.
The low pressure developed by the puny oil pump kept a huge leak from occurring.
BB
On 3, Feb 2010, at 2:44 PM, jerb wrote:
>
> What is the purpose of placing a piece of silk thread along with sealant when
joining the two cast halves of an aircraft engine. Is this done on all engines
or just Continental and Lycoming, what about 4-stroke Rotax.
> jerb
>
>
>
>
>
Message 25
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| Subject: | seeking Firefly dimensions |
I need some dimensions for the simulator model. If anyone has a tape rule,
a few minutes and their plane is nearby...
1. Wing chord
2. distance from trailing edge to top of tail boom
3. length of tail boom (exposed only)
4. horizontal stabilizer width and root cord
5. elevator chord
6. vertical stabilizer height and root chord
7. rudder chord
8. fuselage max. width
9. height of fuselage at aft end
10. prop axis to tail boom
11. prop to trailing edge of wing
BTW one list member who owns a FF has dusted off his X-Plane software for
his computer and downloaded the first iteration of the model. If anyone is
similarly inclined I would be glad to assist.
bk
Message 26
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| Subject: | Re: prop tip speed and noise |
Thom, The only time I see 5800 RPM is on climbout. If I need a workout
pulling the control bar in I'll cruise at 5400, normally I use 5200. Those
figures are with the little wing. With the 19M I cruise at 4700 when I have
my wife with me and 4300 when flying it solo.
I wear a Shoei full face helmet when I fly it without any ear plugs. It's a
little louder with the visor open than when closed but it's pretty quiet.
Rick
On Wed, Feb 3, 2010 at 10:23 AM, Thom Riddle <riddletr@gmail.com> wrote:
>
> Rick,
>
> Assuming your cruise rpm is about 5800 your prop tips are rotating at only
> 284 mph plus your airspeed of 50-60 mph I would guess for a total tip speed
> of about 330 mph or so. That is a whopping 45% less than my tip speed. That
> has got to be a BIG factor.
>
> How does it sound to you while flying it?
>
> --------
> Thom Riddle
> Buffalo, NY
> Kolb Slingshot SS-021
> Jabiru 2200A #1574
> Tennessee Prop 64x31
>
>
> We refuse to believe this country, so powerful to defend its citizens
> abroad, is unable to protect its citizens at home.
> - Ida B. Wells
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=284728#284728
>
>
Message 27
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| Subject: | Re: Reason for use of Silk Thread |
> The low pressure developed by the puny oil pump kept a huge leak from
occurring.
> BB
Bob B/Gang:
I am fortunate with my leak/ooze in that respect. I am dealing with
crankcase pressure of 3 to 5 psi in the gear box. Thank goodness it is not
the engine oil pressure or I would be dealing with about 50 psi.
1936 John Deere D, if the oil pressure needle comes off the peg, it is good
to go. ;-)
john hauck
mkIII
titus, alabama
Message 28
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Gary/Gang:
Got a bigger photo?
Thanks,
john hauck
mkIII
titus, alabama
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| Subject: | Re: Kolb-List Digest: Spray foam 02/02/10 |
________________________________ Message 4 _____________________________
________
Time: 06:32:25 AM PST US
From: robert bean <slyck@frontiernet.net>
Subject: Re: Kolb-List: dynamic balancing
Don't do it. -At least if you are considering the "stuff" in the litt
le
cans.
I tried it in a motor vehicle once and it wicks and holds moisture.
Rusted out faster than ever.
BB
On 2, Feb 2010, at 8:50 AM, Mike Welch wrote:
> > By the way, has anyone ever put the
> > spray in foam into the wing panels close to the root through the
inspection
> > holes? Ted
>
> Ted,
>
> Although the foam might be a good idea, you do have to be careful.
There are 3 grades of the stuff (at least three that I know of). The
grades vary by how much expansion pressure they have. The weak grade
is
for window gaps, etc. It doesn't distort the structure. The strong
grade can and will spread apart the structure gap, like in a door fram
e
gap. It can actually ruin the door fits to where it won't close
anymore.
> If you were to try using this foam, I'd recommend the middle
expansion foam, and try it in a test area first. It would not be wise
just to start spraying blobs of foam everywhere, only to find you've
now
got wings with bulgy muscles. :-(
>
> Mike Welch
> Do not archive
I used to "shoot" polyurethane expanding foam into brand new Cadillac car
bodies before final assembly.
2 shots on each side went into the plenum (area behind the dash) 4 went
into the rockers on each side, and 2 on each side into the sail panels.
The engineers said it adds a LOT of strength to the hollow cavities and
also deadens sound.
It is similar to the Great Stuff spray can foam available at hardware stor
es but is a 2 part resin and catalyst heated to 190 degrees and would expa
nd many times it's original volume
and be fully cured in 60 seconds.
I personally would not use any spray foam and expect it to adhere to wing
fabric, but you will never get it fully out of your coveralls!
I can't say anything about it wicking moisture, but if it is used in a re
latively sealed and rigid area like tubing, I wouldn't think it would be
a problem.
Also, for anyone who knows Bill Pickett in Midland, MI., check this link
below. He did my written test for ASC ... Know your ice thickness!!
http://www.wnem.com/video/22405251/index.html
Darren, FS1, temporarily soaking up some FL sunshine!
Message 30
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| Subject: | Re: prop tip speed and noise |
At 12:47 PM 2/3/10 -0500, you wrote:
>
>Try a dovetail saw for that precise cutting job.
>BB
>
Not all tractor aircraft are quiet.
When I was working for a living, RCA Corporation, I used to travel to the
RCA Labs located at Lancaster, PA. To get there one had to fly to
Newark and then board a commuter to Lancaster. The commuter was an
Irish built Short Skyliner, a dressed up version of a little slab sided
cargo hauler that mounted twin turbo props. Looked like a pregnant guppie
with a very wide landing gear. I dreaded those trips, because when the
pilot took off, it was like being inside a drum. You could not keep your
hand on the wall unless you wanted to experience extreme wrist pain. You
just had to guts it out until he got to cruise altitude. One learned to sit
in the extreme tail to get as far away from those propeller blades as possible.
By today's standard, they would not allow anything living to be shipped in
such noisy environment. But back then that was the only way to travel to
Lancaster and get back home in the same day.
Jack B. Hart FF004
Winchester, IN
do not archive
Message 31
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John Hauck wrote:
>
>
>
> Ronnie's harmonic was caused by disturbed air produced by loose fabric which
> billowed up on the inboard aft corner of the right wing. If this is what is
> causing Cowan's Sling Shot harmonic, then the left inboard aft corner of the
> wing would be suspect because the 912 turns opposite the 582.
>
> After securing the loose rib stitching in Ronnie's wing, the harmonic
> mysteriously disappeared. To me, this proves if part of the wing surface,
> or other part of the aircraft, produces disturbed air, it can also produce
> harmonic noise.
>
> I flew Ronnie's Sling Shot before the fabric was reattached and before we
> discovered that this was the problem. Not only was the harmonic loud in the
> cockpit, it also created a vibration that could be felt in the airframe. It
> was bad enough I would not fly the airplane unless the problem was fixed for
> fear of damaging the aircraft.
>
>
> john hauck
> mkIII
> titus, alabama
John, you have jump started my brain to add another "what if" to the mix:
Using a 582 and B box, my MKIII developed damaged fabric along the right side of
the fuselage below the right wing. The Stits paint cracked along the outside
over the diagonal steel tube, and I ended up laying extra fabric tape along both
the inside and outside fabric along the diagonal tube on that side to spread
out the pulses off the prop and keep the fabric and paint from deteriorating
any further.
Point is, there is a pulse produced by the prop that interacts with the airframe,
and depending on the weight and tautness of the fabric, may be a factor.
Perhaps duct tape something to the inside of the left fuselage fabric wall to dampen
things down and go for a test flight? Be like feeding crackers to a dead
man - couldn't hurt anything.
Richard Pike
MKIII N420P (420ldPoops)
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=284787#284787
Message 32
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> Perhaps duct tape something to the inside of the left fuselage fabric
wall to dampen things down and go for a test flight? Be like feeding
crackers to a dead man - couldn't hurt anything.
>
> Richard Pike
That's right, Richard/Gang:
A lot going on back there with the prop on our pusher Kolbs.
And...everything in front of the prop affects its performance, good and bad.
My mkIII had a fabric tail cone initailly, like the original Firestar,
lasted about 100 hours before the 582 with 3 blade GSC wooden prop beat it
to death. That is why I replaced it with sheet metal and haven't had a
problem since, nearly 2,900 hours ago.
This is just the hunch of an old guy that has been around Kolbs a long time.
It is pretty obvious the noise/harmonics is being produced by the prop
because of some other problem with fabric tautness on wing, fuselage,
radically disturbed air flow created mechanically in front of the prop
somewhere on the engine or fuselage, like open rear quarter windows,
parachute canisters mounted in front of the engine on top of the center
section, faulty shimming of gear box torsional vibration dampening system,
and about anything else one could think of.
I can see disturbed air fed into the 3 blade prop causing those blades to
really move back and forth in the dogs and ramps of the gear box. Seems it
would be easy enough to get the right frequency to cause the very
undersirable, noisy harmonics that Cowan's SS experiences. If he ever
discovers the problem, I have a feeling it will be something simple that he
looks at everytime he looks at that airplane, but hasn't identified yet. I
hope he does.
john hauck
mkIII
titus, alabama - Gantt IAP, 60 sm west of Circle C, Ted Cowan's beautiful
airstrip and homestead.
Message 33
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| Subject: | Any one know anything about this outfit |
Hi Folks,
I have a friend that ask if anyone on the list may be familiar with
or have any experience with
<http://www.barnstormers.com//contact_seller.php?to=83456&id=405635&title=TOO+MANY+503%27s+SOME+GOT+TO+GO+&return=%2FEngines%2B-%2BPiston%2C%25202-Stroke%2520Classifieds.html>Rotax
Rick -
<http://www.barnstormers.com//contact_seller.php?to=83456&id=405635&title=TOO
MANY 503's SOME GOT TO GO
&return=%2FEngines%2B-%2BPiston%2C%25202-Stroke%2520Classifieds.html>RED
GOLD ROTAX ENGINES & OVERHAULS, Broker - located Naples, FL. They
sell Rotax engines with red shrouds. Since this isn't directly Kolb
related if you don't mind please reply to me direct. I have never
heard of these folks yet they claim to sell a lot of engines.
jerb
Message 34
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| Subject: | Pre-construction advise wanted |
Kolbsters,
I am just about to start piecing together my wings, and then tail. Over time
I have picked up a few hint about possible improves to avoid weak areas of
design, or maybe I should say weak materials. I have read enough to know
these are great plane, but does anyone have a list of thing they would
change or materials they would upgrade if they were doing it all over
again.?
Thanks as always,
Nick Cassara
Palmer, Alaska
Proto type Kolbra is going to have wings again!
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