 |
Matronics Email Lists
Web Forum Interface to the Matronics Email Lists
|
| View previous topic :: View next topic |
| Author |
Message |
Fox5flyer
Guest
|
 Posted: Thu Apr 26, 2007 7:31 am Post subject: alcoholic gas tanks-structural? |
 |
|
This wing tank business has gotten me to thinking which can sometimes be
dangerous. To me, this is a "chicken and egg" question. Are the wing tanks
really a necessary structural part of the wing? Having built both a M2 and
S5 Kitfoxes, my experience with them has given me cause to wonder about what
this actually means. My full question is are the wing tanks actually a
necessary structural part of the wing or do they become structural when
they're installed? As I recall, the early Kitfoxes had no standard wing
tanks at all, but were optional, relying on the tank behind the instrument
panel. Some had a six gallon tank on one side and nothing on the other and
others had a thirteen on one side and a six on the other, but I think this
was later in the evolution. My M2 had optional aluminum six gallon wing
tanks and prior to selling it at about 400 hours I hadn't had any problems
with them leaking, but I understand that the new owner eventually had
leaking problems due to cracking at the welded seams. The cracking problem
is well known because the wing flexes so much and by anchoring the tanks in
there rigidly, in turbulence, something eventually has to give.
I can definitely see the merit in the tanks provided by Steve Winder. They
just sit in a cavity and essentially float so that they aren't affected by
flexing. By dividing into two separate, but connected tanks, any amount of
tank flexing is further reduced, IMO. Personally, I think it's a better
concept because they still allow the wing to flex through it's full length
where the standard thirteen gallon tanks don't flex at all which means the
there might eventually be a problem with stress in a local area of the spar
just outboard of the tanks.
Good post John! Keep us in the loop on the process.
Now, if we could do something about that price! 
Deke Morisse
NE Michigan
S5/Soob/CAP
| Quote: |
Bob, When I pulled the factory-installed tanks (Sky Star '94) out of a
Series 5 factory-built wing, I noticed that 90% of the adhesive designed to
|
bond the tank to the spars was cured without any contact with the spar. This
was because of the large gap between the tank's front and rear surfaces and
the spar surfaces. With almost no adhesive bond, how strong could that be?
It was mostly just the small tank flanges glued to the top surface of the
spar (most of which was also loose). The fabric is glued down to the top of
the tank, but how strong could that be? Anyway, the new tanks connect with
small aluminum tubes connected between the spars, plywood over and under the
tanks - glued all the way around, and expanding foam filling the voids. I've
built houses, surfboards, worked on boat construction, etc. And all I can
say is that this APPEARS that it will be at least as strong as what was
there. And that's just an opinion, I'm not an aero engineer. As you say,
info on the net !
| Quote: | is worth what you pay. But ours is an experimental hobby by nature. Steve
of "WingTanks.com" says that other experimentals are flying with this type
|
of tank and similar wing construction - I believe he said "Just Aircraft"
are using this type of tank.
| Quote: | John Sandt / Series 7 / tri-gear / Corvair / Ridgecrest, CA
<<As the tanks are load-bearing structurally, how do you know the new
tanks will do that job?>>
|
| | - The Matronics Kitfox-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Kitfox-List |
|
|
|
| Back to top |
|
 |
rexinator(at)gmail.com
Guest
|
| Posted: Thu Apr 26, 2007 8:33 am Post subject: alcoholic gas tanks-structural? |
|
|
When I took apart my broken right wing the 13 gallon wing tank was in
place and IMHO was acting mostly as a wing form for the fabric covering.
I don't think the tanks were designed to be structural as in "load
bearing", but rather to take the place of the rib that must be omitted
to fit them in the wing.
Of course I'm no engineer and as always advice from the interenet is
worth what you paid.
Rex Hefferan
SE Colorado / K-II / 582-C / still waiting repairs
fox5flyer wrote:
| Quote: |
This wing tank business has gotten me to thinking which can sometimes be
dangerous. To me, this is a "chicken and egg" question. Are the wing tanks
really a necessary structural part of the wing? Having built both a M2 and
S5 Kitfoxes, my experience with them has given me cause to wonder about what
this actually means. My full question is are the wing tanks actually a
necessary structural part of the wing or do they become structural when
they're installed? As I recall, the early Kitfoxes had no standard wing
tanks at all, but were optional, relying on the tank behind the instrument
panel. Some had a six gallon tank on one side and nothing on the other and
others had a thirteen on one side and a six on the other, but I think this
was later in the evolution. My M2 had optional aluminum six gallon wing
tanks and prior to selling it at about 400 hours I hadn't had any problems
with them leaking, but I understand that the new owner eventually had
leaking problems due to cracking at the welded seams. The cracking problem
is well known because the wing flexes so much and by anchoring the tanks in
there rigidly, in turbulence, something eventually has to give.
I can definitely see the merit in the tanks provided by Steve Winder. They
just sit in a cavity and essentially float so that they aren't affected by
flexing. By dividing into two separate, but connected tanks, any amount of
tank flexing is further reduced, IMO. Personally, I think it's a better
concept because they still allow the wing to flex through it's full length
where the standard thirteen gallon tanks don't flex at all which means the
there might eventually be a problem with stress in a local area of the spar
just outboard of the tanks.
Good post John! Keep us in the loop on the process.
Now, if we could do something about that price!
Deke Morisse
NE Michigan
S5/Soob/CAP
|
| | - The Matronics Kitfox-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Kitfox-List |
|
|
|
| Back to top |
|
|
lcfitt(at)sbcglobal.net
Guest
|
| Posted: Thu Apr 26, 2007 1:23 pm Post subject: alcoholic gas tanks-structural? |
|
|
Before quick-build in the days of no tanks, wing lockers, 6 and 13 gallon
tank options there were several ways to lay out the wing on the jig for
assembly. My guess is that since quick build wings became available, the
most frequent configuration was the 13 gallon tank on both wings, so maybe
that is the configuration most are familiar with.
I pulled out my builders manual and there are three wing diagrams for laying
out the diagonal braces (drag-anti-drag tubes). The first with wing locker
only, the second with 6 gallon tank and the third with the 13 gallon tank.
The only diagrams that doesn't show the diagonal braces in all the rib bays
is when the tanks are in place and then the brace configuration varies so
that the diagonal braces are always terminated at the outboard side of the
tank.
With the wing locker, the brace passes through the locker - essentially no
unbraced wing bay.
The Rans airplanes have the tanks sitting above the diagonal braces, so the
braces
are continuous throughout the wing structure - a major limiting factor for
theie relatively smaller fuel capacity.
The diagrams tend to indicate a structural component to the
tank, essentially replacing the drag-anti-drag tubes in that area.
I scanned the page, but feel reluctant to post it as it is clearly
copywrited by SS.
In the event the tank / wing locker configuration doesn't allow for the
braces to continue to their logical termination at a wing spar, the unbraced
segment of wing is at the wing tip. This suggests that at the root of the
wing, diagonal bracing is important. With regard to the RTV 90% unattached
to the wing, I suggest that was a builder issue rather than a design issue.
Lowell Fitt
Cameron Park, CA
Model IV-1200 R-912 UL Warp
1998 850 hrs.
---
| | - The Matronics Kitfox-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Kitfox-List |
|
|
|
| Back to top |
|
|
josandt(at)verizon.net
Guest
|
| Posted: Thu Apr 26, 2007 4:53 pm Post subject: alcoholic gas tanks-structural? |
|
|
Lowell, Good point. However, keep in mind that the guy I bought the wing from flew it for 10 years, and it is in great condition today.
No stress cracks, signs of warpage or fatigue, etc. If the tank had been designed as a structural member, wouldn't there have been some consequence to the spars from years of flying without it adequately glued in? P.S. I'm not going to have it dissected and subjected to microscopic analysis - don't go there.
<In the event the tank / wing locker configuration doesn't allow <for the braces to continue to their logical termination at a wing <spar, the unbraced segment of wing is at the wing tip. This <suggests that at the root of the wing, diagonal bracing is <important. With regard to the RTV 90% unattached to the wing, I <suggest that was a builder issue rather than a design issue.
John Sandt / Kitfox 7 builder / tri-gear / Corvair / Ridgecrest, CA
| | - The Matronics Kitfox-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Kitfox-List |
|
|
|
| Back to top |
|
|
Bob
Joined: 24 Oct 2006
Posts: 89
Location: Damascus, Maryland, USA
|
| Posted: Thu Apr 26, 2007 5:44 pm Post subject: Re: alcoholic gas tanks-structural? |
|
|
Lowell made some good observations about the bracing and it fits with John McBean writing:
Posted: Wed Apr 11, 2007 8:16 pm Post subject: Fuel tanks
I have been trying to stay away from this discussion but have found it necessary to point out a few issues that I do not believe are being considered. The Kitfox wing was structrually tested with the current tanks and the tanks ARE part of the wing structure… unlike many other designs where the tank is cradled beneath the surface. The tank IS part of the airfoil shape of the TOP part of the wing. It is also part of the Drag/Anti-drag component of the wing. Safety of Flight - Kitfox does not endorse or promote the use of aftermarket tanks for safety of flight issues. I can go on… but those are the highlights… Fly Safe !! John McBean 208.337.5111 www.kitfoxaircraft.com "It's not how Fast... It's how Fun!"
With respect to the lack of bonding of the tanks to the spars in one airplane, I'll agree that it was probably one builder's installation and add that it's not what the construction manual shows. Compression bracing doesn't take much structure, but structure does need to be there and in the correct orientation, especially as you approach Vne. We could reverse-engineer to see how much margin this may have had left, or argue that these airplanes are indeed legally exerimental and you could use toilet paper on yours if you'd like to. However, the reality is that we are actually dealing with kits that were engineered to place specific pieces of structure where each is needed. Not knowing whether some additional engineering basis existed for the different tanks was why I asked whether there was something to substantiate them. So far, I'll stick with John's advice.
Bob S.
A&P, Aero Eng
Damascus, MD
Series 5 Vixen Kit #27 in-work with no engine yet.
| | - The Matronics Kitfox-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Kitfox-List |
|
_________________
Remember that internet advice may only be worth what you pay. |
|
| Back to top |
|
|
Guy Buchanan
Joined: 16 Jul 2006
Posts: 1204
Location: Ramona, CA
|
| Posted: Thu Apr 26, 2007 7:32 pm Post subject: alcoholic gas tanks-structural? |
|
|
At 02:23 PM 4/26/2007, you wrote:
| Quote: | The diagrams tend to indicate a structural component to the
tank, essentially replacing the drag-anti-drag tubes in that area.
|
It is true that the tanks could possibly act as drag braces in their
bays. It is also true that some amount of drag bracing is required,
though it is not clear how much. You really are in "experimental
land". I hope that if you can't prove the new tanks are at least as
strong as the old that you'll use some kind of parachute for the
initial envelope expansion.
(I am a structural engineer, but the information's still only worth
what you paid for it.  )
Guy Buchanan
San Diego, CA
K-IV 1200 / 582-C / Warp / 100% done, thanks mostly to Bob Ducar.
Do not archive
| | - The Matronics Kitfox-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Kitfox-List |
|
_________________
Guy Buchanan
Deceased K-IV 1200
A glider pilot too. |
|
| Back to top |
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|
Get Email Distribution Too!
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
