Quantcast

Wrapping Fiberglass around Aluminum t increase strength?

HomeBuiltAirplanes.com

Help Support HomeBuiltAirplanes.com:

rotax618

Well-Known Member
Joined
Oct 31, 2005
Messages
970
Location
Evans Head Australia
Wrapping a section of large diameter (5-6”+) thin walled alloy tube in fibreglass will increase its resistance to buckling failure irrespective of the bond or no-bond between the glass and the tube, this is a good way to re-inforce the junction of a tail boom with the forward fuselage of a pod and boom pusher at the maximum bending moment, the thickness of the fibreglass would be tapered to lessen the shear force where the tube exited the glass.
 

cheapracer

Well-Known Member
Log Member
Joined
Sep 8, 2013
Messages
6,277
Location
Australian
conducting an "experiment" out of ignorance just to see what happens.
... is great fun.

Microwave oven, super glue, vulcanised rubber, X-rays, insulin, ..... it's a long list.


You're making a lot of assumptions about our experience.
If you had ever wrapped a tube with fiberglass, you wouldn't be trying to dismiss me, clearly you have never had experience with it based on your post.

However when ever I need to know about nails in wooden spars, that you devoted a whole irrelevant paragraph too, I see you're the man.


I've experienced personally what happens to mixed structures when the temperatures fluctuate.
You have experienced open ended structures where separation will be and likely to be experienced, in fact guaranteed with fiberglass on aluminium, but we are talking about fiberglass completely encapsulating a metal tube, do you understand the difference?

.............. Oh, heck, I just remembered another plane that uses steel landing leg tubes encapsulated in fiberglass, stupid me as one of those planes belongs to me, and is sitting in my factory.

Here is the build of them, I'm sure Billski will be interested http://www.foxcon.com/Manuals/Build Assist - Kit Assembly HK3a.pdf
 

Toobuilder

Well-Known Member
HBA Supporter
Log Member
Joined
Jan 19, 2010
Messages
4,905
Location
Mojave, Ca
What seems to be lacking in this entire thread is the context of what the OP is trying to accomplish. Most of us went straight to "primary structure" and that warrants all the caution we can muster. If we are discussing stiffening up some steel gear legs, that takes it way down on the list of things to worry about.
 

rv7charlie

Well-Known Member
Joined
Nov 17, 2014
Messages
939
Location
Jackson
We already see stuff like aluminum leading edges pulling loose from their nails in wood structures, and I've seen that in old Champs, too. There's also an AD against Champs/Citabrias with wood spars, where the spars crack where the aluminum ribs are nailed to the spar. The spar not only shrinks with age, but the rib expands and contracts and puts stress on the nails, separating the grain.
While I'm not disagreeing with the difficulty of merging 'glass & metal for structure, I think this one has more to do with the basic nature of wood & nails. That concept was certified by someone with a degree in pencils.

Show me a wooden deck with the deck boards attached with nails, and after a few years, I'll show you nails that have backed out. On my deck at my house, I used a single nail in each end of each board, purely as positioners to align the boards on my deck, followed by pairs of screws on every joist, including the nailed ones. I've probably pulled out a dozen nails that are climbing out of the wood, even though the screws are holding the decking to the joists. Heat-cold; wet/dry; load/unload....nails loaded in tension are coming out. It's just a question of when.

edit: I should add that my 2nd ride in small plane was in a Decathalon, before I even thought I could get a pilot's license. When the owner told me that the plane had to be checked periodically for pulling nails, I wondered about the wisdom of acro (or even flying) in something built like that.
 

BBerson

Light Plane Philosopher
HBA Supporter
Joined
Dec 16, 2007
Messages
13,810
Location
Port Townsend WA
That Foxcon has embedded steel tube gear legs. I haven't seen embedded steel dissolve from intragranular corrosion like embedded aluminum. The 40 year Grob has embedded steel, wood, acrylic, foam and aluminum. Only problem is aluminum. The steel apparently only gets surface rust but doesn't dissolve that quickly.
 

pictsidhe

Well-Known Member
Joined
Jul 15, 2014
Messages
8,650
Location
North Carolina
Wrapping a section of large diameter (5-6”+) thin walled alloy tube in fibreglass will increase its resistance to buckling failure irrespective of the bond or no-bond between the glass and the tube, this is a good way to re-inforce the junction of a tail boom with the forward fuselage of a pod and boom pusher at the maximum bending moment, the thickness of the fibreglass would be tapered to lessen the shear force where the tube exited the glass.
When you need to stiffen something like that, the ideal way is to use a tapered aluminium sleeve. In this case, that is a royal PITA to do. So you sigh, and take the weight hit of the far easier glass wrap. Sometimes, the dark side is just too tempting.
 

rotax618

Well-Known Member
Joined
Oct 31, 2005
Messages
970
Location
Evans Head Australia
There are many instances where it would be beneficial to wrap an aluminium tube frame with fibreglass in an aircraft structure.
It would be the best way to bond a composite skin to a tubular frame, directly bonding a composite skin to alloy tubes is virtually impossible because of the nature of the materials and the point contact, rivets and bolts introduce point loads to the skin (not good) and holes in the tubes introduces points of failure.
In alloy frames members are often adequate to resist tensile loads but have to be sized much larger because of slenderness ratio resistance to compressive buckling - wing struts on very light aircraft are a case in point where a round tubular strut is used, wrapping that strut with glass and encapsulating it in a teardrop shaped foam glass skin can both decrease the slenderness ratio and provide streamlining.
In both the above examples it matters not if the fibreglass is bonded to the full length of the tube (allowing for thermal expansion ) to provide the necessary reinforcement.
 

Topaz

Super Moderator
Staff member
Log Member
Joined
Jul 29, 2005
Messages
14,250
Location
Orange County, California
What seems to be lacking in this entire thread is the context of what the OP is trying to accomplish. Most of us went straight to "primary structure" and that warrants all the caution we can muster. If we are discussing stiffening up some steel gear legs, that takes it way down on the list of things to worry about.
This. Without this context, every reply here is little more than speculation. Perhaps the OP will chime in and narrow down the possibilities here.
 

mcrae0104

Well-Known Member
HBA Supporter
Log Member
Joined
Oct 27, 2009
Messages
3,452
What seems to be lacking in this entire thread is the context of what the OP is trying to accomplish.
Isn't the OP's goal made clear in the thread title? Wrapping fiberglass around aluminum is simply dead weight that does not add strength. Billski et al addressed it as thoroughly as that question could be answered. (And pictsidhe gets the week's brevity prize for post #2.)
 

Jet787

Active Member
Joined
Sep 3, 2020
Messages
39
Location
Northern Va
So back to your original question, I’m not sure what you mean by “help the integrity of the strength”? Do you mean increase strength or prevent corrosion or something else?
Is the original strut/tube strong enough to meet the design loads? If it is then you may be adding weight without significant increase in strength and may alter the load profile of the designed part.
 

Yellowhammer

Well-Known Member
Joined
Feb 21, 2020
Messages
220
What seems to be lacking in this entire thread is the context of what the OP is trying to accomplish. Most of us went straight to "primary structure" and that warrants all the caution we can muster. If we are discussing stiffening up some steel gear legs, that takes it way down on the list of things to worry about.

Nose gear landing strut.
 

Yellowhammer

Well-Known Member
Joined
Feb 21, 2020
Messages
220
Gentleman,

I would never post questions if I thought anyone might go back and forth at one another.

I should have clarified my intent at first but was really curious across a broad spectrum.

My original question really has to do with the nose gear strut and if wrapping it in fiberglass would result in a stiffer/ stronger strut.

Thanks to all for their input. I truly value each and every one of you!
Yellowhammer
 
Top