Glider Noises

[Jerz Rossignol]

Hi Guys,

My LS-6a makes some serious humming noises. Not wind noises, not
loose gap seal tape noise, not noises from the glider not being
aligned with the airflow, not noises from my gear doors. The noise is
like a loud revirberation or resinance or loud humming coming from the
rear of the fuselage. When both of my cockpit vents (canopy and nose
vent) are closed I hear the noise. When I go faster the noise just
gets much louder all the way to redline. As soon as I open either
canopy or nose vent the noise completely goes away. This has not
bothered me too much this summer but it's fall now and it's getting
cold. My choice to not be cold is to listen to that loud noise or
bundle up.

When the front nose vent is all the way closed there is still a fair
bit of air coming through the vent because of the animal hair as the
seal for the vent. I understand that this is done on purpose to keep
the canopy from getting fogged up and also to keep the
internal/external pressures the same. I am hoping someone has come up
with a solution to this problem I am having. If anyone can give me
some helpful advice to this problem I would really appreciate it.

I am curious if sealing the front nose vent with foam instead of
animal hair might help. I'm curious if sealing the rudder with
external seals would help.

Thanks for any help!!

Greg

[Bill Daniels]

Rudder or elevator gap seals?

"Jerz Rossignol" > wrote in message
om...
> Hi Guys,
>
> My LS-6a makes some serious humming noises. Not wind noises, not
> loose gap seal tape noise, not noises from the glider not being
> aligned with the airflow, not noises from my gear doors. The noise is
> like a loud revirberation or resinance or loud humming coming from the
> rear of the fuselage. When both of my cockpit vents (canopy and nose
> vent) are closed I hear the noise. When I go faster the noise just
> gets much louder all the way to redline. As soon as I open either
> canopy or nose vent the noise completely goes away. This has not
> bothered me too much this summer but it's fall now and it's getting
> cold. My choice to not be cold is to listen to that loud noise or
> bundle up.
>
> When the front nose vent is all the way closed there is still a fair
> bit of air coming through the vent because of the animal hair as the
> seal for the vent. I understand that this is done on purpose to keep
> the canopy from getting fogged up and also to keep the
> internal/external pressures the same. I am hoping someone has come up
> with a solution to this problem I am having. If anyone can give me
> some helpful advice to this problem I would really appreciate it.
>
> I am curious if sealing the front nose vent with foam instead of
> animal hair might help. I'm curious if sealing the rudder with
> external seals would help.
>
> Thanks for any help!!
>
> Greg

[Shawn]

Jerz Rossignol wrote:
> Hi Guys,
>
> My LS-6a makes some serious humming noises. Not wind noises, not
> loose gap seal tape noise, not noises from the glider not being
> aligned with the airflow, not noises from my gear doors. The noise is
> like a loud revirberation or resinance or loud humming coming from the
> rear of the fuselage. When both of my cockpit vents (canopy and nose
> vent) are closed I hear the noise. When I go faster the noise just
> gets much louder all the way to redline. As soon as I open either
> canopy or nose vent the noise completely goes away. This has not
> bothered me too much this summer but it's fall now and it's getting
> cold. My choice to not be cold is to listen to that loud noise or
> bundle up.
>
> When the front nose vent is all the way closed there is still a fair
> bit of air coming through the vent because of the animal hair as the
> seal for the vent. I understand that this is done on purpose to keep
> the canopy from getting fogged up and also to keep the
> internal/external pressures the same. I am hoping someone has come up
> with a solution to this problem I am having. If anyone can give me
> some helpful advice to this problem I would really appreciate it.
>
> I am curious if sealing the front nose vent with foam instead of
> animal hair might help. I'm curious if sealing the rudder with
> external seals would help.
>
> Thanks for any help!!
>
> Greg

It doesn't know the words. :-)

Seriously, perhaps a control rod seal is leaking.

Shawn

[Diederik]

At our gliding club we have a ls-4 which has exactly the same problem,
although it only manifests itself at high speed. I think it is
resonance of the air inside the fuselage (almost the same as blowing
on a bottle or a organ pipe). We haven't looked for a solution jet.
Would like to know if anyone has...

I could imagine that a restriction in the fuselage would help so that
you change the wavelength and therefore the resonance frequency.

Diederik

(Jerz Rossignol) wrote in message >...
> Hi Guys,
>
> My LS-6a makes some serious humming noises. Not wind noises, not
> loose gap seal tape noise, not noises from the glider not being
> aligned with the airflow, not noises from my gear doors. The noise is
> like a loud revirberation or resinance or loud humming coming from the
> rear of the fuselage. When both of my cockpit vents (canopy and nose
> vent) are closed I hear the noise. When I go faster the noise just
> gets much louder all the way to redline. As soon as I open either
> canopy or nose vent the noise completely goes away. This has not
> bothered me too much this summer but it's fall now and it's getting
> cold. My choice to not be cold is to listen to that loud noise or
> bundle up.
>
> When the front nose vent is all the way closed there is still a fair
> bit of air coming through the vent because of the animal hair as the
> seal for the vent. I understand that this is done on purpose to keep
> the canopy from getting fogged up and also to keep the
> internal/external pressures the same. I am hoping someone has come up
> with a solution to this problem I am having. If anyone can give me
> some helpful advice to this problem I would really appreciate it.
>
> I am curious if sealing the front nose vent with foam instead of
> animal hair might help. I'm curious if sealing the rudder with
> external seals would help.
>
> Thanks for any help!!
>
> Greg

[Avron Tal]

If it is a noize like holding a buttole in the wind then it is a
resonance inside the rear fuslage.
Try changing the size of the rear venting hole (at the bottom of
rudder).
For a test you can block the hole with tape (not good for performance,
the air will leak into the wings)

Avron

[G.A. Seguin]

(Diederik) wrote in message >...
> At our gliding club we have a ls-4 which has exactly the same problem,
> although it only manifests itself at high speed. I think it is
> resonance of the air inside the fuselage (almost the same as blowing
> on a bottle or a organ pipe). We haven't looked for a solution jet.
> Would like to know if anyone has...
>
> I could imagine that a restriction in the fuselage would help so that
> you change the wavelength and therefore the resonance frequency.
>
> Diederik
>
> (Jerz Rossignol) wrote in message >...
> > Hi Guys,
> >
> > My LS-6a makes some serious humming noises. Not wind noises, not
> > loose gap seal tape noise, not noises from the glider not being
> > aligned with the airflow, not noises from my gear doors. The noise is
> > like a loud revirberation or resinance or loud humming coming from the
> > rear of the fuselage. When both of my cockpit vents (canopy and nose
> > vent) are closed I hear the noise. When I go faster the noise just
> > gets much louder all the way to redline. As soon as I open either
> > canopy or nose vent the noise completely goes away. This has not
> > bothered me too much this summer but it's fall now and it's getting
> > cold. My choice to not be cold is to listen to that loud noise or
> > bundle up.
> >
> > When the front nose vent is all the way closed there is still a fair
> > bit of air coming through the vent because of the animal hair as the
> > seal for the vent. I understand that this is done on purpose to keep
> > the canopy from getting fogged up and also to keep the
> > internal/external pressures the same. I am hoping someone has come up
> > with a solution to this problem I am having. If anyone can give me
> > some helpful advice to this problem I would really appreciate it.
> >
> > I am curious if sealing the front nose vent with foam instead of
> > animal hair might help. I'm curious if sealing the rudder with
> > external seals would help.
> >
> > Thanks for any help!!
> >
> > Greg


Hi,
My LS6b has the same problem if I do not tape the horizontal/vertical fin gap.
Or if I do not seal the square opening on top the elevator.
S6

[Erik mann]

(G.A. Seguin) wrote in message >...
> (Diederik) wrote in message >...
> > At our gliding club we have a ls-4 which has exactly the same problem,
> > although it only manifests itself at high speed. I think it is
> > resonance of the air inside the fuselage (almost the same as blowing
> > on a bottle or a organ pipe). We haven't looked for a solution jet.
> > Would like to know if anyone has...
> >
> Hi,
> My LS6b has the same problem if I do not tape the horizontal/vertical fin gap.
> Or if I do not seal the square opening on top the elevator.
> S6

Ditto on my old LS4 and my LS8. I now have a piece of .040 clear
plastic film permanantly taped (hinged) in front of the access opening
as a cover. After the stabilizer is completely threaded on, the cover
is taped on the remaining three sides. Makes a nice, smooth surface
and allows you to see that the stabilizer has been locked down during
the critical assembly check. Common blister-packs for food make a
good source of the clear material (I think mine came from a package of
Proscuitto).

Also, I had low density foam all around the top of the stabilizer to
prevent airflow up into the tail; IIRC, my LS4 was completely free of
any howling, even at high speeds.

Erik Mann
LS8-18 (P3)

[Thomas F. Dixon]

..
> > >
> > > >
>
> Hi,
> My LS6b has the same problem if I do not tape the horizontal/vertical fin gap.
> Or if I do not seal the square opening on top the elevator.
> S6

I had the same thing with my LS6C. For some reason it stopped when I
closed the window and nose vent. When I put a cover on the square
area on top ot the fin where the bolt is, it stopped. Can not explain
the connection to the vents being closed and this cover. I used a
piece of clear plastic like you find on a manual cover, taped it
towards the front with a good long lasting tape so that it would hinge
forward. The after installing the tail and tightening the nut I taped
the other three sides with wing tape. Noise stopped and I could see
to check the bolt during pre flight. I always taped the
horizontal/vertical fin gap too.

Tom

Idaho

[Jerz Rossignol]

Hey Guys,

I found Günter Schapka's response to my question to be quite
interesting and informative. He is the original Rolladen-Schneider LS
Construction & Design guys. He is always very helpful.

Best Regards,

Greg

************************************************** ***********************

Greg,

Your description immediately reminds me of a weeklong search for a
humming noise in about 1987 or 89: We found the rudder sides of an LS3
vibrating. Checking this is easy: tape a 5or 6mm brass or iron tube in
flight direction to both rudder sides, one third from the lower end
and check the effect in flight. (Don't go up to max. speed, your mass
balance might be out of limits) These will stiffen the shell. I will
not try to comment on more possibilities unless you have checked this
one.
--
Viele Grüße/Kind regards and always happy landings

Günter Schapka
Konstruktion/Design