Today's Message Index:
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1. 11:33 AM - how not to crack your yak52 fuel tanks (Olivier Vigneron)
2. 11:55 AM - Re: how not to crack your yak52 fuel tanks (A. Dennis Savarese)
3. 06:31 PM - Re: how not to crack your yak52 fuel tanks (cjpilot710@aol.com)
4. 10:21 PM - Re: how not to crack your yak52 fuel tanks (Jeff Hove)
5. 11:37 PM - Re: how not to crack your yak52 fuel tanks (Olivier Vigneron)
Message 1
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| Subject: | how not to crack your yak52 fuel tanks |
Hi All
I encounter some difficulty with reccurents issues about gas tanks that are
leaking.
An aero welder told me that are the results of hard aerobatics with half
full tanks . As the fuel is able to hit the tank wall.
Yesterday a lituanian mechanic told me that are the results of bumping on
grass field with full tanks on hot days.....
Who's says the truth? The welder? The lituanian? both? :-)
This discussion is about to make an aerobatics policy to avoid tank
cracking !
Thanks
Olivier
Message 2
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| Subject: | Re: how not to crack your yak52 fuel tanks |
It is my opinion the problem with the Yak 52 fuel tanks is the flexing
of the tank metal due to vapor expansion during hot weather. This is
prevalent in all Yak 52's with the single vent tube on the belly of the
airplane and very rarely seen on Yak 52's with dual vent lines exiting
the belly of the airplane. (Post 1989 manufacture). If the Yak 52 is
left in the sun without venting the fuel tanks by loosening the fuel
caps, the expansion of the fuel vapor causes the very thin fuel tank
metal to expand, thus flexing the fuel tank. The constant flexing and
contracting during hot weather ultimately causes the tank to fracture.
Many (more than 50%) of the leaks appear around the weld points on the
bottom of the tank where the interior baffles are welded to the exterior
metal.
I seriously doubt hard aerobatics would cause the tank to fracture
because the tank has several baffles inside the tank which prevent the
fuel from sloshing back and forth.
I also doubt bumping on a grass field with full tanks would cause the
metal to crack.
The constant flexing of the tank metal due to a very poor tank vent
system design is more likely the cause of the metal fracturing.
Dennis
A. Dennis Savarese
334-285-6263
334-546-8182 (mobile)
www.yak-52.com
Skype - Yakguy1
On 6/10/2012 1:29 PM, Olivier Vigneron wrote:
> Hi All
>
> I encounter some difficulty with reccurents issues about gas tanks
> that are leaking.
>
> An aero welder told me that are the results of hard aerobatics with
> half full tanks . As the fuel is able to hit the tank wall.
>
> Yesterday a lituanian mechanic told me that are the results of
> bumping on grass field with full tanks on hot days.....
>
>
> Who's says the truth? The welder? The lituanian? both? :-)
>
> This discussion is about to make an aerobatics policy to avoid tank
> cracking !
>
> Thanks
>
> Olivier
> *
>
>
> *
Message 3
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| Subject: | Re: how not to crack your yak52 fuel tanks |
Test 1234.
I'll go along with Dennis views. But I would like to add one more which I
really think it is the primary cause for cracks showing up. Vibration,
constant and rather high amplitude vibrations. At times these vibrations can
hit harmonic resonance with the different parts of the metal structures,
that hardens or crystallize though the metal and that usually shows up as
cracks particularly around weldments. These are areas where stress tends
concentrated. Most of this vibration comes from the engine. If the shocks in
the engine mount are old, bottomed out, the vibration from the engine can
be incredible throughout the airframe. Particularly in acrobatics. A
friend of mine who is a test pilot for Extra, can actually feel a shock
bottoming out while doing outside snaps.
While fuel sloshing around in the tank during acrobatics sounds logical,
but because of where the fuel is located (usually near the CG), I do not
believe there is enough room in the tank for fuel to build up some inertia
against a tank wall. Especially with any kind of baffling inside.
I would look at the total time on the airplane. The longer it is exposed
to these vibrations I believe you will see more cracks. Vibrations can be
very insidious. In the mid-50s a number of Lockheed Electra's (four engine
turbo prop) had wings come off in cruise flight due to harmonic vibrations
set up by the outboard engines. It was my understanding as a young
teenager that harmonic vibration caused the spar at the center section of the
wing, basically to become work harden and crack. A little more complicated
than that but basically that. To this day, Lockheed, the Navy and a number
of firefighting companies, have a joint program monitoring the wing
conditions of the Elektra. The fix if I remember correctly was a change in the
engine mounts and thicker wing skins.
Like Dennis I doubt bumping on a grass field with full tanks caused the
fuel tanks to crack UNLESS that airplane is pretty tired already.
Jim "Pappy" Goolsby
In a message dated 6/ aerobatics would cause the tank to fracture
because the tank has several baffles inside the tank which prevent the
fuel from sloshing back and forth.
I also doubt bumping on a grass field with full tanks would cause the
metal to crack.
The constant flexing of the tank metal due to a very poor tank vent
system design is more likely the cause of the metal fracturing.
Dennis
A. Dennis Savarese
334-285-6263
334-546-8182 (mobile)
www.yak-52.com
Skype - Yakguy1
On 6/10/2012 1:29 PM, Olivier Vigneron wrote:
> Hi All
>
> I encounter some difficulty with reccurents issues about gas tanks
> that are leaking.
>
> An aero welder told me that are the results of hard aerobatics with
> half full tanks . As the fuel is able to hit the tank wall.
>
> Yesterday a lituanian mechanic told me that are the results of
> bumping on grass field with full tanks on hot days.....
>
>
> Who's says the truth? The welder? The lituanian? both? :-)
>
> This discussion is about to make an aerobatics policy to avoid tank
> cracking !
>
> Thanks
>
> Olivier
> *
>
>
> *
Message 4
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| Subject: | Re: how not to crack your yak52 fuel tanks |
How hard is it to modify a single-vent Yak-52 to the newer dual-vent
system? Are instructions or a kit available?
Jeff Hove
On 6/10/2012 1:49 PM, A. Dennis Savarese wrote:
> <dsavarese0812@bellsouth.net>
>
> It is my opinion the problem with the Yak 52 fuel tanks is the flexing
> of the tank metal due to vapor expansion during hot weather. This is
> prevalent in all Yak 52's with the single vent tube on the belly of
> the airplane and very rarely seen on Yak 52's with dual vent lines
> exiting the belly of the airplane. (Post 1989 manufacture). If the
> Yak 52 is left in the sun without venting the fuel tanks by loosening
> the fuel caps, the expansion of the fuel vapor causes the very thin
> fuel tank metal to expand, thus flexing the fuel tank. The constant
> flexing and contracting during hot weather ultimately causes the tank
> to fracture.
>
> Many (more than 50%) of the leaks appear around the weld points on the
> bottom of the tank where the interior baffles are welded to the
> exterior metal.
>
> I seriously doubt hard aerobatics would cause the tank to fracture
> because the tank has several baffles inside the tank which prevent the
> fuel from sloshing back and forth.
>
> I also doubt bumping on a grass field with full tanks would cause the
> metal to crack.
>
> The constant flexing of the tank metal due to a very poor tank vent
> system design is more likely the cause of the metal fracturing.
>
> Dennis
>
>
> A. Dennis Savarese
> 334-285-6263
> 334-546-8182 (mobile)
> www.yak-52.com
> Skype - Yakguy1
>
>
> On 6/10/2012 1:29 PM, Olivier Vigneron wrote:
>> Hi All
>>
>> I encounter some difficulty with reccurents issues about gas tanks
>> that are leaking.
>>
>> An aero welder told me that are the results of hard aerobatics with
>> half full tanks . As the fuel is able to hit the tank wall.
>>
>> Yesterday a lituanian mechanic told me that are the results of
>> bumping on grass field with full tanks on hot days.....
>>
>>
>> Who's says the truth? The welder? The lituanian? both? :-)
>>
>> This discussion is about to make an aerobatics policy to avoid tank
>> cracking !
>>
>> Thanks
>>
>> Olivier
>> *
>>
>>
>> *
>
>
Message 5
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| Subject: | Re: how not to crack your yak52 fuel tanks |
Hi Jim
What you wrote sounds strangely accurate to me....! My yak52 is my first
one and my first plane too.
I fly very often with a friend that had a yak52 and he was always
complaining because "my plane was so shaky that he lost all his teeth" :-)
As it's my first yak52, I had no comparaison at all...and I talked about
those vibrations to the lituanians mechanic. He started the engine and
found that was really shaky so he tested the prop balancing.
The vibrations was very high and after prop balancing it is now perfect.
So, now, I'm not surprised about cracks as result of heavy vibrations.....
Thanks
Olivier
2012/6/11 <cjpilot710@aol.com>
> **
>
> Test 1234.
>
> I'll go along with Dennis views. But I would like to add one more which I
> really think it is the primary cause for cracks showing up. Vibration,
> constant and rather high amplitude vibrations. At times these vibrations
> can hit harmonic resonance with the different parts of the metal
> structures, that hardens or crystallize though the metal and that usually
> shows up as cracks particularly around weldments. These are areas where
> stress tends concentrated. Most of this vibration comes from the engine.
> If the shocks in the engine mount are old, bottomed out, the vibration from
> the engine can be incredible throughout the airframe. Particularly in
> acrobatics. A friend of mine who is a test pilot for Extra, can actually
> feel a shock bottoming out while doing outside snaps.
>
> While fuel sloshing around in the tank during acrobatics sounds logical,
> but because of where the fuel is located (usually near the CG), I do not
> believe there is enough room in the tank for fuel to build up some inertia
> against a tank wall. Especially with any kind of baffling inside.
>
> I would look at the total time on the airplane. The longer it is exposed
> to these vibrations I believe you will see more cracks. Vibrations can be
> very insidious. In the mid-50s a number of Lockheed Electra's (four engine
> turbo prop) had wings come off in cruise flight due to harmonic vibrations
> set up by the outboard engines. It was my understanding as a young
> teenager that harmonic vibration caused the spar at the center section of
> the wing, basically to become work harden and crack. A little more
> complicated than that but basically that. To this day, Lockheed, the Navy
> and a number of firefighting companies, have a joint program monitoring the
> wing conditions of the Elektra. The fix if I remember correctly was a
> change in the engine mounts and thicker wing skins.
>
> Like Dennis I doubt bumping on a grass field with full tanks caused
> the fuel tanks to crack UNLESS that airplane is pretty tired already.
>
> Jim "Pappy" Goolsby
>
>
> In a message dated 6/ aerobatics would cause the tank to fracture
> because the tank has several baffles inside the tank which prevent the
> fuel from sloshing back and forth.
>
> I also doubt bumping on a grass field with full tanks would cause the
> metal to crack.
>
> The constant flexing of the tank metal due to a very poor tank vent
> system design is more likely the cause of the metal fracturing.
>
> Dennis
>
>
> A. Dennis Savarese
> 334-285-6263
> 334-546-8182 (mobile)
> www.yak-52.com
> Skype - Yakguy1
>
>
> On 6/10/2012 1:29 PM, Olivier Vigneron wrote:
> > Hi All
> >
> > I encounter some difficulty with reccurents issues about gas tanks
> > that are leaking.
> >
> > An aero welder told me that are the results of hard aerobatics with
> > half full tanks . As the fuel is able to hit the tank wall.
> >
> > Yesterday a lituanian mechanic told me that are the results of
> > bumping on grass field with full tanks on hot days.....
> >
> >
> > Who's says the truth? The welder? The lituanian? both? :-)
> >
> > This discussion is about to make an aerobatics policy to avoid tank
> > cracking !
> >
> > Thanks
> >
> > Olivier
> > *
> >
> >
> > s such se, --> - MATRONICS WEB FORUMS -**
>
>
> *
>
> *
>
>
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