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#1
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substitute aluminum for 4130?
Plans call for wing spar to fuselage carry through attach fiitings to be
7/8x1/8 4130 steel. Advisability of using 9/16x 3/16 6061-T6 aluminum as I have it on hand. Your thoughts please. I have plans for another ship which uses the 6061-T6. Thanks |
#2
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substitute aluminum for 4130?
On Sun, 21 Jan 2007 23:01:03 -0800, "Robert Loer" wrote:
Plans call for wing spar to fuselage carry through attach fiitings to be 7/8x1/8 4130 steel. Advisability of using 9/16x 3/16 6061-T6 aluminum as I have it on hand. Your thoughts please. I have plans for another ship which uses the 6061-T6. You're going to bet your life on advice from an anonymous USENET source? Brrrr...... Ron Wanttaja |
#3
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substitute aluminum for 4130?
Robert Loer wrote: Plans call for wing spar to fuselage carry through attach fiitings to be 7/8x1/8 4130 steel. Advisability of using 9/16x 3/16 6061-T6 aluminum as I have it on hand. ---------------------------------------------------------- Hahahahaha! Good one. This IS a joke, right? Trolling for the sim's? Because it isn't the material but the load it has to carry, which I couldn't help but notice was not mentioned. -R.S.Hoover |
#4
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substitute aluminum for 4130?
Robert Loer wrote: Plans call for wing spar to fuselage carry through attach fiitings to be 7/8x1/8 4130 steel. Advisability of using 9/16x 3/16 6061-T6 aluminum as I have it on hand. Your thoughts please. I have plans for another ship which uses the 6061-T6. At the maximum design load, how much deflection do you have with each? What is your factor of safety with each? If you don't know, don't substitute. -- FF |
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substitute aluminum for 4130?
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#6
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substitute aluminum for 4130?
wrote in message ps.com... Robert Loer wrote: Plans call for wing spar to fuselage carry through attach fiitings to be 7/8x1/8 4130 steel. Advisability of using 9/16x 3/16 6061-T6 aluminum as I have it on hand. Your thoughts please. I have plans for another ship which uses the 6061-T6. At the maximum design load, how much deflection do you have with each? What is your factor of safety with each? If you don't know, don't substitute. -- FF Wing attach fittings on a 1953 Super Cub wing presently undergoing rebuild in our hangar are 6061-T6 aluminum but quite beefy. Two quarter-inch plates are bolted to each side of each of the spar webs at the wing root. Interference fit steel bushings are then pressed through the plates for the 5/16" diameter wing-attach bolts. The new PA-18's built in Yakima are probably built with the same alloys, just my guts feeling. Wing attach fittings on the fuselage are steel. I don't know if they're 4130 or not but suspect they are 1025 steel. Some of the fuselage tubes are 4130, but most of them are 1025. One lift strut is 1025, the other 4130. |
#7
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substitute aluminum for 4130?
Earlier, Robert Loer wrote:
Plans call for wing spar to fuselage carry through attach fiitings to be 7/8x1/8 4130 steel. Advisability of using 9/16x 3/16 6061-T6 aluminum as I have it on hand. Your thoughts please. I have plans for another ship which uses the 6061-T6. Thanks **** Disclaimer: I'm not an engineer. This is not engineering advice. This is stuff anyone with high-school physics oughta grasp. /disclaimer **** Executive summary: normalized 4130 steel is good for 90000 psi in tension. 6061-T6 aluminum is good for 42000 psi in tension. Do the math. Just for grins, let's take a swag at the proposed substitution. For the sake of this swag, let's start by guessing that the fitting is a simple tang loaded longitudinally through a 1/4" bolt in a hold drilled through the middle of the metal strap. The cross-sectional area of the steel strap is (7/8)/8=0.109in^2. The hole subtracts (1/4)/8=0.031in^2, so the area at the hole station is 0.078in^2. If we say that the ultimate tensile strength of the steel is 90000 psi (90 ksi), that drilled strap might be good for a longitudinal tension of 90000*.078=7030 pounds force (lbf). For the proposed aluminum substitution, the cross-section area of the strap is 9*3/(16^2)=0.105". The hole subtracts (3/16)/4=0.047in^2, leaving a cross-sectional area at the hole of 0.058in^2. If we wanted to, we could stop right there. Since the aluminum strap has less cross-sectional area at the hole than the steel strap, and since aluminum is generally softer, weaker, and more elastic than steel, and has less forgiving fatigue properties, we know that the proposed substitution cannot be as strong in simple tension as the steel original. That doesn't mean that it isn't strong enough, but we have way too little information to figure out exactly what "strong enough" is. All we have to go on is "as strong as the original design," so that has to be our guide in this. However, just for grins let's look at how much weaker: The proposed substitution has a cross-section at the hole of 0.058in^2. If we say that the ultimate tensile strength of 6061-T6 is 42 ksi, that means that our drilled strap might support 42000*.058=2440 lbf. That's only about a third of what the original will do in simple tension. Oh, and it gets worse, much worse. Since we're talking about a major structural attach fitting, there is no guarantee it is only loaded in simple tension or compression. In fact, it is almost certain that it is loaded in bending as well. Bending strength and stiffness are related to the cube of the depth times the width. I could go on and on about this, but I think we've already made as many guesses and suppositions as we ought. Without specific details of the design and how it is loaded we can do no more meaningful analysis. In fact, the analysis I suggest above is highly suspect without knowing how the strap is installed and secured. To wrap this up, I'll not say that you should never consider such substitutions. After all, homebuilt aircraft are all about making what you need out of what you can get. However, it oughta stand to reason that when you substitute weak stuff for strong stuff, you're going to need a lot more of the weak stuff. Trying to trade straight across isn't ususally a good idea, and trying to get away with even less of the weak stuff than that is probably a bad idea. Thanks, and best regards to all Bob K. http://www.hpaircraft.com/hp-24 http://www.hpaircraft.com/glidair |
#8
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substitute aluminum for 4130?
"Bob Kuykendall" wrote in message
ps.com... Earlier, Robert Loer wrote: Plans call for wing spar to fuselage carry through attach fiitings to be 7/8x1/8 4130 steel. Advisability of using 9/16x 3/16 6061-T6 aluminum as I have it on hand. ... However, it oughta stand to reason that when you substitute weak stuff for strong stuff, you're going to need a lot more of the weak stuff. Trying to trade straight across isn't ususally a good idea, and trying to get away with even less of the weak stuff than that is probably a bad idea. Thanks, and best regards to all Bob K. http://www.hpaircraft.com/hp-24 http://www.hpaircraft.com/glidair So, like, you are suggesting that he should go with the Handyman's secret weapon? Would he have to use the whole roll to make it strong enough? -- Geoff The Sea Hawk at Wow Way d0t Com remove spaces and make the obvious substitutions to reply by mail When immigration is outlawed, only outlaws will immigrate. |
#9
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substitute aluminum for 4130?
Earlier, Capt. Geoffrey Thorpe wrote:
So, like, you are suggesting that he should go with the Handyman's secret weapon? Would he have to use the whole roll to make it strong enough? Heh, I hadn't thought of it that way. Some interesting material for thought there! One of the things I've been doing for fun lately is proof-loading bits of rock climbing gear to see what they do under load. My latest test was this series on a Ukrainian (sp?) camming anchor: http://www.rockclimbing.com/cgi-bin/...15428;#1515428 However, I have seen no such test results for good ol' duct tape. What are its ultimate and yield strengths in ksi and kn? It's Young's Modulus at 0- 45- and 90-degrees? Peel strength? Which brands are strongest? Weakest? Inquiring minds want to know! Once we have that data in hand, we can build a substitution table that shows how many plies it takes to substitute for various thicknesses of 4130, 2024-T3, 6061-T6, and 7075-T6. An Akaflieg student (a real one, I mean) can write a thesis on computational methods for analyzing duct tape laminations, specifically addressing the previously hard-to-quantify factors of tooth marks, thumbprints, and those places where it folds over and sticks to itself. AC43.13 change 2e will address the repair of duct tape laminates, with specific reference to brand-name materials that went off the market in 1974. Or something like that... Thanks, Bob K. |
#10
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substitute aluminum for 4130?
In article om, Bob Kuykendall
says... Earlier, Capt. Geoffrey Thorpe wrote: So, like, you are suggesting that he should go with the Handyman's secret weapon? Would he have to use the whole roll to make it strong enough? Heh, I hadn't thought of it that way. Some interesting material for thought there! One of the things I've been doing for fun lately is proof-loading bits of rock climbing gear to see what they do under load. My latest test was this series on a Ukrainian (sp?) camming anchor: http://www.rockclimbing.com/cgi-bin/...15428;#1515428 However, I have seen no such test results for good ol' duct tape. What are its ultimate and yield strengths in ksi and kn? It's Young's Modulus at 0- 45- and 90-degrees? Peel strength? Which brands are strongest? Weakest? Inquiring minds want to know! Once we have that data in hand, we can build a substitution table that shows how many plies it takes to substitute for various thicknesses of 4130, 2024-T3, 6061-T6, and 7075-T6. An Akaflieg student (a real one, I mean) can write a thesis on computational methods for analyzing duct tape laminations, specifically addressing the previously hard-to-quantify factors of tooth marks, thumbprints, and those places where it folds over and sticks to itself. AC43.13 change 2e will address the repair of duct tape laminates, with specific reference to brand-name materials that went off the market in 1974. Hmmm I guess we would need to know the section modulus as well and the moment of enertia of th section .Maybe a composite of duct tape and cardboard would give better stifness .Ahhhh the possibilities are endless :-) Chuck (tape 'er down boys tape 'er down ) S |
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