Hangar Flying => Hangar Flying => Topic started by: Charles Davis on February 28, 2005, 05:55:22 PM
Title: Lift tabs
Post by: Charles Davis on February 28, 2005, 05:55:22 PM
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
Title: Lift tabs
Post by: Daniel Tyrkiel on February 28, 2005, 08:55:48 PM
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.
Title: Lift tabs
Post by: Waiter on March 01, 2005, 06:50:32 AM
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
Title: Lift tabs
Post by: Dan Patch on March 01, 2005, 12:06:44 PM
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
Title: Alternate Lift Tab material
Post by: Joe Person on March 01, 2005, 11:34:15 PM
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
Title: Lift tabs
Post by: Charles Davis on March 08, 2005, 03:23:03 PM
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.
Title: Lift tabs
Post by: Anonymous on March 08, 2005, 08:23:40 PM
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.
Title: Lift tabs
Post by: Waiter on March 08, 2005, 09:13:14 PM
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
Title: Lift Tabs
Post by: Charles Davis on March 09, 2005, 06:40:51 PM
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!
Title: Lift tabs
Post by: Waiter on March 09, 2005, 08:17:02 PM
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
Title: Re: Lift tabs
Post by: Harry A on March 24, 2005, 01:24:57 PM
Charles, commenting on this older post ,
Quote from: "Charles Davis"
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.
Quote from: "Charles Davis"
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.
Quote from: "Charles Davis"
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.
Title: Lift tabs
Post by: Charles Davis on March 30, 2005, 12:53:15 PM
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.
Title: Lift Tabs
Post by: Arleigh (Bruce) Hughes on May 04, 2005, 09:02:35 AM
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.
Title: Lift Tabs
Post by: Joe Person on May 04, 2005, 09:14:41 AM
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!
Title: Is it possible to alodine after installation?
Post by: Anonymous on May 04, 2005, 01:48:14 PM
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....
Title: Lift Tabs - Alodine Application
Post by: Joe Person on May 04, 2005, 10:59:45 PM
Application of Alodine can be done in-situ, but one must exercise caution to ensure the solution does not find its way between surfaces that cannot be disassembled & rinsed. The Alodine 1200 or 1201 solution (the oft-used "gold" colored mix) is a ferro-chromic acid solution that performs a controlled chemical reaction / oxidation of the aluminum. The reaction is stopped by removal from the Alodine, and a rinse. If Alodine wicks into areas where it cannot be rinsed off, a decent corrosion problem can be established. Think of Alodine wicking up into the canard, on the lift tabs. One could not remove the Alodine up in the structure, and further etching would occur.
In the field, application of such treatments in-situ is often done with paper towels placed on the area to be treated, and wetted with the Alodine. It does work, but one still has to be careful. Any situation where gravity or unwanted capillary/wicking action must be eliminated when doing an in-situ treatment.
For anything on our airplanes that cannot be removed for treatment, I'd suggest applying a good primer (zinc chromate is very good) followed by a compatible enamel topcoat or epoxy paint. Or, simply use a good primer that is compatible with aluminum and the rest of the airframe, as part of the overall painting effort. Don't worry too much about Alodine application at this point. Also, in any areas where an aluminum part penetrates into a glass layup, use a good automotive urethane seal to fillet-seal the penetration. Do not use ordinary silicone (RTV), as the acids in the uncured mix are probably not good on aluminum. For completely enclosed inserts (e.g. the hardpoint inserts in the Long-EZ wings & center section spar), I would not worry too much about those rotting away - they are pretty well isolated from Ma Nature's fury.
For my VariEze wing fittings, they have complete periphery seals made from a chromate-based aircraft sealant (ProSeal). I do not ever expect any moisture penetration into the fitting-to-sparcap intrface areas because of this. Not everyone can get ahold of small quantities of such sealant (I work for Boeing...), hence the suggestion to use a good automotive urethane sealant (available at most auto body & paint stores).
Hope this helps some.
Title: Lift tabs
Post by: Anonymous on May 05, 2005, 05:56:34 AM
Thanks for the detailed and complete reponse.
ProSeal is readily available...the RV crowd uses it to seal their tanks. Van's has it, and so do the rest of the usual suspects. I think that Van's might have it in very small quantities.
Title: lift tabs
Post by: Charles Davis on May 10, 2005, 04:08:44 PM
I went ahead and machined mine from (.125) 304 stainless.
What swayed me wasn't so much the strength increase, but the resistance to bending, scratching, and corrosion of 304 vs 2024.
I am trying to be careful about weight inflation by adding "Just a few more ounces" here and there. This is one area that I chose to tolerate the extra weight and fabrication effort & cost.
Title: CRES Lift Tabs
Post by: Joe Person on May 10, 2005, 04:40:49 PM
And the 304 CRES is...
Annealed, 1/4h, 1/2H, 3/4H, Full Hard?
Plain, sulfur-containing, free-machining 304, or 304L?
If annealed 304, is there an understanding that the yield strength is 64% of the yield strength of 2024-T3?
After machining, is there a step to passivate, so as to remove potential corrosion cells (e.g. the embedded ferrous bits intrinsic to standard machining practices)?
What kind of bolts will be used to attach the tabs to the canard (internally)?
Just curious...
Title: Lift tabs
Post by: Tom on May 11, 2005, 12:05:57 AM
Charles,,
I can only beg that you stick with the plans and make the lift tabs out of the recomonded material. It is clear to me that your not an engineer and you dont understand what your doing..
Sorry to be so blunt, but it is the truth, and I'm sure others will agree.
if you have doubt in the design,, look at the pics here..
http://www.ez.org/cp45-p3.htm
Tom
Title: Lift Tabs
Post by: Charles Davis on May 11, 2005, 05:21:42 PM
Thanks for the responses. If you guys tell me to dig them out, I will.
I used .125" 304 Stainless steel sheet ordered from McMaster-Carr
Part Number: 9785K17 www.mcmaster.com
I picked an area of the sheet with no blemishes or scratches, and CNC machined the tabs so the grain direction of the metal ran in the "long" direction of the tabs (up-down).
The part was to thickness, so all I did was drill the holes and contour the OD.
To finish, I used a fine file on the OD to remove any machining tooling marks.
No other processes (heat treat, etc) were done.
Title: Lift tabs
Post by: 1 Glider pilot on May 11, 2005, 09:25:27 PM
Just something to think about the 304 stainless you selected has a Yield strength of 30,000 psi The aircraft grade Alum. has a Yield strength of 47,000 to 50,000 psi. The alum. is heat treated to a T4 condition and the stainless is Anealled, thats soft. 304 stainless can not be heat treated, it must be worked to make it harder as in rolling or forming. The problem that will be forever on your mind as you fly along over the city with your loved one in the back seat is which one of the modifcations to the plans will work and which one will fail. Doesn't make for very fun flying. If you are going to make changes don't just think something is stronger or better , Know it is or Stick to the plans! And have fun building and flying safe.
Title: Charles Davis
Post by: Charles Davis on May 11, 2005, 11:01:12 PM
Where were you guys a few months ago?
That's it. We're pulling them out and putting in the plans tabs. Thank you all for the very knowledgeable and honest responses. You may have well saved my life.
This is the only structural item where we deviated from the stock plans (other than well documented and proven mods, like the Davenport nose and brakes).
Lesson learned. :oops:
Title: Lift tabs
Post by: Waiter on May 12, 2005, 05:45:58 AM
Quote
Where were you guys a few months ago?
CD, Please reread all of the previous posts to this thread.
The stainless is OK, leave them in. You may be exposing your canard to higher risk by the act of making the change, rather than the materials being changed.
I think the point made from the last several posts, there's a lot more to this stuff than eyeball engineering. BUT, thats what this is all about, learning.
Waiter
Title: Lift tabs
Post by: 1 glider pilot on May 12, 2005, 08:56:14 AM
Learning at whos expense? your loved ones? or maybe your own life? You may want to have an engineer look at the numbers before replacing the lift tabs. Stainless is like carbon fiber, it looks great and strong right up to the point where it goes , Bang. Replacing the tabs is not a hard job, many were replaced many years ago when Brock supplied customers with tabs made of 2024-0 (dead soft ) material and recalled them. Don't make structural parts out of material that you can't identify as the correct material, as printed on the sheet. Watch out for surplus material it may be the incorrect printing on the material that landed it in the surplus yard. Suppliers make mistakes and the Mtr's ( Manufacturing test reports ) sent with the material can be sent with the wrong material. the guy who filled the order may be the lowest paid employee at the supplier. Those pieces of paper are for the Lawyers not the undertakers to argue over at some to be determined date. Have fun building and fly safe.
Title: Lift Tabs
Post by: Bruce Hughes on May 14, 2005, 09:15:22 AM
Hi Charles and others
If you have decided to remove the SS tabs and have not yet done so, email me direct at bruce@ywave.com
I just finished (early April) doing that job. May have a suggestion or 2.
It is not hard to do. Few minutes each day for a few days.
Title: Lift tabs
Post by: Gilbert DRIEUX on May 15, 2005, 04:00:59 PM
I recently weigh my VE, and whith 57lb lest at FS0, read on the nose wheel balance : 42 lb. With me at pilot seat 247lb 186 lb Nose wheel FS is quite the same as Canard LE FS.
That is to said that in flight the total effort in both tab is : 42 - 57 + 186 = 171lb........, 85lb each = 39 kg ! (sorry, I understand better kg' figures.....!). Don't change the plans. Tabs are far strong enough! :D Concidering 3g acceleration, 85 lb are 255 lb each. Don't need NASA's materials... Did you pay attention to the engine mount ? :roll: Do you remember to bind the engine to the fuselage with a chain ? As recommanded, to warrant CG position in "normal" range (and accordingly flight control ability.....) in case of engine mount collapse.... :shock:
I beg your pardon for my poor english practical.... :oops:
Title: Lift Tabs
Post by: niceez on May 15, 2005, 06:17:27 PM
I hope you did exactly as your post said and removed them. I repair composite airplanes part-time and have the engineering background to explain this into the ground as does Joe Person and others that have the technical background.
Rutan has a copy of my tape of the canard load tests. In that test it shows the steel frame (1/4" steel) failing under all the weight when the canard twisted. The lift tabs never failed with all the weight and it was well beyond 30 G's.
For Waiter - No one will never hurt the canard by replacing the lift tabs in the recommended way. The skin that is removed durring this process does not carry the major part of the load but rather the bottom spar cap (only as a refresher to get the gears spinning :) ). The larger top spar cap is in compression and the bottom spar cap is in tension taking most of the load. Since the cut (1" X 3") is in front of the lift tab there is no weakening of the shear web, top or bottom spar cap that carries the load.
The three new plies of UNI the span over the top to a well sanded surface are in front of the lift taps and is more then enough to re-constitute the strength before the cutting, - as long as it is done correctly.
Thank you for the original poster asking the forum. You more then likely saved your own life. You do not know how many times during the repair of a canard airplane I find deviations from the plans. It just cost the owner money for me to put it back to the way it should be.
Dale
Title: Lift tabs
Post by: Charles Davis on May 16, 2005, 05:51:15 PM
Yes, we are definitely replacing them.
I didn't quite understand the implications of changing this material. People tried to tell me in earlier posts, but I wasn't listening.
That's why I really appreciated the blunt talk and solid facts regarding the stainlesss vs. aluminum tabs.
That's what it took for it to really register with me.