Lift tabs

[Charles Davis]

I've always been queezy about the lift tabs, as I know loosing a canard would be catastrophic.

I'm considering machining the lift tabs from .125 Stainless rather than Aluminum.

Does anyone see any problem with this?

Thanks

[Daniel Tyrkiel]

I can't tell you now a specific URL but you can find a Canard Pusher newsletter with a photo of an EZ canard load test with the canard hanging from it's lift tabs. It's reasurring... Also, Just follow proper aluminum machining technics (no kinks or bumps to start a crack!) and you'll be fine. Duraluminum has a better strenght to weight ratio then steel that's why you use it on airplanes. You do need more material (by volume) than steel in high stress areas so if you have a high load to transfer you're better off with a smaller piece of steel than a bulky piece of aluminum. Go with the plans and you'll save some weight.

[Waiter]

I've been involved in a couple EZ accident investigations over the years. When the canard rips off, it takes F22 with it, the attach points are still on the canard, along with portions of F22.

I think the true test of a canards (and attach points) strength is surviving a flyin or airshow were your EZ is on static display.

Sit back and watch (in horror) as kids use the canard as a diving boards, a tetter totter, seat all the family for a group photo (how nice)  and Mr Mustle man can really pick up the entire plane from the end of the canard.

Waiter

[Dan Patch]

I'm considering machining the lift tabs from .125 Stainless rather than Aluminum....

This was discussed a number of months ago rather extensively on the Canard Aviator's forum.  If you want the gory details, search the archives.

Short answer is that the "weak appearance" of the lift tabs has bothered a lot of 'eye ball engineers'.  The fact is, however, that the tabs, as designed are 'way, way over adequate' and have never been known to fail.  Changing their strength without substantially modifying what they are attached to is completely useless if they are the 'strong link in the chain' (and they are).  Changing what they are attached to (e.g., spar layup schedule, bolt diameter, etc.) has very significant potential consequences that are outside the realm of 'it just looks stronger so it's better' (e.g., flutter response, torsional stiffness of the canard, load transfer issues, etc.).  I would GUESS that changing the tab material would not do any significant harm other than adding a little weight, but I NEVER GUESS when thinking about modifying a key structural component of the airplane.  

IHMO, bottom line(s) are to go with the design, as is, don't fret the tab strength, build this part of the plane with your best workmanship, and get on with building.  

Best

[Joe Person]

The stock, 2024-T3, .125 lift tabs are good for about 30 g's in the VariEze installation, and a bit less (of course) on a Long-EZ.  They are quite well overdesigned for either airplane.  As previously stated, you will obliterate the F-22 bulkhead in overload well-before the lift tabs become the weak link.

An alternate material like CRES (Corrosion REsistant Steel) is really not necessary, nor will it necessarily be a desireable substitute for aluminum.  One has to worry about proper passivation (controlled development of a satisfactory oxide layer on the surfaces of the CRES) prior to any bonding or embedding into composite structures.  Suffice to say, an improperly passivated CRES surface can actually corrode rapidly at bond or protrusion zones, due to lack of a properly established oxide layer.

Stick with the plans.  There is nothing wrong nor weak in the canard attach configuration.

-Joe Person
Tech Counselor 4418
Structures & mech systems (aircraft) engineer

[Charles Davis]

I read a post on the old forum regarding damage (bending and scratches) on lift tabs on older EZ's.

Our thinking now is to go with 3/16" 2024-T3 and hard anodize them, or go with 1/8" 203 stainless.

Sorry to keep beating this, but I'd appreciate any thoughts you experts out there may have.

[Anonymous]

Other inquiring minds would as well like to know if there would be a 'problem' with going stainless, even though the conventional wisdom states that it isn't needed.

[Waiter]

If it will provide the builder with piece of mind, that is a benefit. I added stuff and put extra layers of glass here and there for exactly that same reason, It will be a little stronger, hence, my piece of mind.

If I had it to do all over again, I would watch every ounce. I know I could probably cut 100 lbs off. Wow, what a difference 100lbs makes in performance. My planes performance totally changes just by adding an additional 10 gallons of fuel.

Making the tabs out of stainless probably wouldn't hurt anything.

Waiter

[Charles Davis]

Waiter,

Very interesting and useful comments.
What engine are you using?
What is your Basic Empty Weight?
What would you change if you had to do it over?

Thanks!

[Waiter]

To be fair to myself, I think I turned out a remarkable machine, considering I didn't know anything about any of this stuff when I started.

The problem is, you don't know about these things until you've already done it, then seen the results.  Also Economics changes and so does technology.

Weigh is the biggest performance factor. I would adopt a stringent weight control program and stick to it.

Here is my wish list. Note, some of these things I'm doing now.

Put the lightest weight instruments I could find. All my steam guages are gone and replaced by two electronic displays.

I'd do full retracts from the start.

IO360 (200hp) with constant speed prop ( I currently have O-320 (160hp))

All those extra layups and strengthing, didn't need it.,

I would attempt to either Vacumn bag or at least do the LowVac method on all my layups

The Strake/wing junctions would be cleaner, and need almost no fill.

The wing and canard cores would be cut better, and need almost no fill.

I'd move the strake baggage compartment in about three inches, and get more fuel.

No external sumps

No winglets

internal rudder bellcranks.

heavy duty brakes.

Downdraft cooling.

It will be very interesting to see what the weight difference will be. I'm guessing no change, because I'm able to do some weight reduction, in conjunctioon with adding the heavy gear.

Waiter

[Harry A]

Charles, commenting on this older post ,

I read a post on the old forum regarding damage (bending and scratches) on lift tabs on older EZ's.

 I would bet any bending and scratches on lift tabs are from abuse rather than normal use.

Our thinking now is to go with 3/16" 2024-T3 and hard anodize them, or go with 1/8" 203 stainless.

Anodizing actually reduces the strength of aluminum minimally and hard anodize is great for abrasion resistance but actually makes it more brittle, at least at the coating.

Sorry to keep beating this, but I'd appreciate any thoughts you experts out there may have.

From a non-expert. Stay with the as plans tabs.

[Charles Davis]

McGyver,

I just checked my private message regarding anodizing affecting the fatigue life of aluminum.

I REALLY appreciate your frank and expert knowledge.  Thanks for taking the time to help me!

Your advice is understood and I'll follow it.

[Arleigh (Bruce) Hughes]

Guys be careful what you are thinking/saying.

Aluminum for aircraft is ALODINED.

Aluminum in ordinary consumer products is ANODIZED.

They are NOT the same thing.   Anodizing reduces the strength
of the aluminum.   Both processes increase the corrosion
resistance.

Steel treatment is a 3rd process.   Not the same as the other 2.

Use ALODINE on all aluminum for airplanes.   I bought someone
else's project and I have a lot of examples of what happens to
bare aluminum over a few years.   IT AIN'T PRETTY.

[Joe Person]

And aluminum for aircraft can be anodized (MS20001-( ) extruded aluminum hinge is often anodized as part of the manufacturing process).  The nice little aluminum "AN" fittings for hoses, etc., are anodized too.  The big reduction factor with anodizing is the reduction in FATIGUE strength, and that varies with the type of anodizing performed.

Application of chemical film treatments (i.e. Alodine) or anodizing (anodes, cathodes, acid solutions & electricity) are both acceptable treatments for aluminum used in aerospace applications, BUT, one has to understand what each process does to the base metal in order to assess the suitability of the process for whatever widgit is to be treated.  Terry Schubert willing, there will be a write-up in a forthcoming CSA newsletter on this issue.

Cheers!

[Anonymous]

Posit: You buy a project that has had all of the embedded aluminum already installed (e.g. hard points in the spar for the wing bolts, lift tabs in the canard, etc.).

It has been built per original plans, which IIRC do not specify alodining or doing anything other than floxing the aluminum in place.

Question: Is it possible to prep and alodine the exposed aluminum, or is that a waste of time?

Follow-on question: If it is not possible to treat the exposed aluminum in this way, what preventive measures would you employ to keep it nice and minty-fresh?

(sorry for the "guest" id... I really must get around to registering here....