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Thread: The Ranger, an easily built high wing LSA runabout

  1. #136
    Registered User Victor Bravo's Avatar
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    Re: The Ranger, an easily built high wing LSA runabout

    To answer Fritz' question on SWAG'ing the forces going through the ribs:

    OK, so you got 600 pounds times 4G, which is 2400 pounds of lift. 1200 pounds per side, and say 8 wing ribs per side is 150 pounds of force being put through each rib. Assuming the large majority of the lifting force is located closer to the thickest and most highly cambered part of the airfoil (near the maian spar), then as a guess perhaps we are dealing with 110 to 125 pounds of force being transferred through each rib to the spars at that chordwise location.

    HOWEVER, elliptical or bell-shaped lift distribution tells us that the amount of force will not be uniform over the entire semi-span, so there will be several ribs on the inboard side that will see more than the average share of force. So perhaps some of the inboard ribs will see 140-160 pounds of force and some of the outermost ribs may only see 60-80 pounds.

    But remember, being conservative people who want to live a little longer, we are putting in a 1.5 FOS, so instead of 2400 we figure 3600 pounds in a worst case situation, which is 1800 per side, averaging 225 pounds per rib in uniform distribution, and then we figure some of them go up and down 10-15% for the elliptical lift distribution. This would result in some of the ribs being asked to transmit 259 pounds of force from the outer skin into the main wing spar.

    But again, the majority of force may be located at the main spar location, but not all of it, so maybe we can back that 259 down to 210-225 pounds.
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  2. #137
    Registered User Victor Bravo's Avatar
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    Re: The Ranger, an easily built high wing LSA runabout

    Quote Originally Posted by erkki67 View Post

    The Ulf glider had foam ribs too,

    the Cricri or Cricket of Colomban had foamribs glued onto a Aluminium spar,
    The ULF-1 glider has ribs made from a million little sticks of wood, there is one sitting in a hangar at the gliderport two hours away from here. The ULF-1 is definitely a very complicated and high parts count construction project. This is why so few have been built, despite the excellent performance and desirability..

    The Cri-Cri is famous worldwide for being a very complicated, demanding, and fiddly building project. Even despite the incredible performance and efficiency of the Cri-Cri, with thousands and thousands of pilots wanting one, there were a relatively small number of Crri-Cri's completed.

    The Ranger is intended to be a very basic, easily constructed design. That is the opposite of building a Cri-Cri or a ULF-1 glider.
    "Everything in this book may be wrong."
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    "Common sense is so rare today, it should be reclassified as a superpower!"
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  3. #138
    Registered User FritzW's Avatar
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    Re: The Ranger, an easily built high wing LSA runabout

    Quote Originally Posted by Vigilant1 View Post
    Have you ever tried/seen something like your green cast material caps, but using thin FG and epoxy? The "C" shape should give plenty of rigidity and (esp) bond area with the foam, and we know epoxy will stay stuck to XPS for decades. It might be less fiddly than the thin birch strips, and maybe one less material type (if thin birch won't be used elsewhere but FG and epoxy will).
    The airplane is mostly Birch ply and there isn't any FG on/in it. FG would be great but it's messy and time consuming. The cast tape is FG but the resin is water activated. It's not as stiff as epoxy but you just dip it in water, put it on and it kicks off in about 60 seconds. It's not as easy or light as ply strips so I don't know if it's really worth messing with.


    Quote Originally Posted by saini flyer View Post
    I would appreciate it if you can pin down the aim for Ranger?

    Build time: Fast build but how fast is anticipated? <90 days'ish>
    Material of choice: Al boom and wood cockpit or Al boom and sheet metal or all sheet metal or.... <my plan is Al tube and wood pod, addicted2climbing is thinking about all al (the magic of open source)>
    Availability of Material: "I" beam spar availability Vs tube etc <I'm planning on I" beam spars but I guess there needs to be an Al L angle and sheet web version also>
    Payload and pilot size: Erkki67 <253.9999 empty and 600 GW>
    Plane type: ul(254) lbs and higher empty weight will be LSA <shooting for 103 but that's going to be tough to do>
    Cost to build: what is the anticipated cost? <shooting for a basic airframe minus gear and FWF ~$2,500. The gear could go from a couple of hundred bucks to $2000 depending on how lazy you are and how fancy you want to get>
    what else??? <it's the whole "kit on a thumb drive" concept and all that it involves. It's beyond the scope of a quick post reply this close to bedtime but there are pages and pages about it on the VP21 thread >
    Iēsous Christos, Theou Yios, Sōtēr

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  5. #139
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    Re: The Ranger, an easily built high wing LSA runabout

    I've long been interested in wood capped foam ribs like this, but have wondered: Why plywood? Seems like the cross grain portion would have very little strength in such a long, skinny part. Wouldn't solid wood be cheaper, lighter and stronger?

    Big pieces of aircraft quality wood are expensive, but I know that in about 20 minutes picking thru the pile I can find 2x4's that have 3-4 foot sections where about half could have 1/16"x1" strips ripped out that meet all the grain density/runout specifications of ANC-18.

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    Re: The Ranger, an easily built high wing LSA runabout

    has anyone tried foam ribs glued to alloy skin?I think the T51 Titan Mustang has alloy over foam in front of the main spar.

  7. #141
    Registered User FritzW's Avatar
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    Re: The Ranger, an easily built high wing LSA runabout

    Quote Originally Posted by Victor Bravo View Post
    ...so maybe we can back that 259 down to 210-225 pounds.
    Using those numbers that works out to about 8 psi on the glue joint between the foam and the aluminum and ply. 24 psi without the ply (that's pretty dang low).
    Iēsous Christos, Theou Yios, Sōtēr

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    Registered User FritzW's Avatar
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    Re: The Ranger, an easily built high wing LSA runabout

    Quote Originally Posted by bifft View Post
    I've long been interested in wood capped foam ribs like this, but have wondered: Why plywood? Seems like the cross grain portion would have very little strength in such a long, skinny part. Wouldn't solid wood be cheaper, lighter and stronger?

    Big pieces of aircraft quality wood are expensive, but I know that in about 20 minutes picking thru the pile I can find 2x4's that have 3-4 foot sections where about half could have 1/16"x1" strips ripped out that meet all the grain density/runout specifications of ANC-18.
    I think 1/16" pine would work fine. But to answer the question about "why plywood?"...

    The capstrips are either in compression or tension. *ANC-18 says Pine is good for 7300 psi ultimate tension parallel to the grain so a 1/16" x 3/4" capstrip is good for 342 lbs. The same reference says 1/16" Birch ply is good for 604 lbs per inch parallel to the grain (obviously the surface grain) so the same captrip would be good for 453 lbs. Solid pine capstrip in compression = 188 lbs, Birch ply = 266 lbs. ...but the real reason for using ply is (for me) it's easier to cut on the CNC machine.


    Quote Originally Posted by Geraldc View Post
    has anyone tried foam ribs glued to alloy skin?I think the T51 Titan Mustang has alloy over foam in front of the main spar.
    ...that would kill three birds with one stone: no capstrips, no covering and it would pop VB's foam rib circuit breaker

    If that would work think of all the drilling, clecoing and deburring you wouldn't have to do.
    Iēsous Christos, Theou Yios, Sōtēr

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  10. #143
    Registered User Victor Bravo's Avatar
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    Re: The Ranger, an easily built high wing LSA runabout

    As a time saver, perhaps you can cut and paste the aluminum gluing procedure from the Monerai and Moni into the instruction sheet on that thumb drive the builders will be using.

    OK, that was nasty even for me, I take it back.

    The PSI loading on the glue joint is not the issue, the issue IMHO is achieving a usable chemical bond between the glue and the metal. Once that is done, Home Depot Gorilla Glue will be strong enough for this use.

    I have it on good authority (from someone who genuinely has the scientific background to know this) that gluing aluminum is possible, but it does require a chemical procedure similar to Alodine. Acid wash, water rinse, specific chemical conversion coating, water rinse, dry. Then I understand you can get about 80% bond strength using epoxies and other adhesives.

    By comparison, .025" aluminum sheet metal is about $2.50 a square foot (ACS 2017 catalog on my desk, 6061, 4 x 12 sheet, $120.00 give or take). If each rib blank occupies a space of about 2 square feet (6 inch thick airfoil, 4 foot chord length rib), then the raw material for the rib blank is five bucks. 8 ribs in a wing is $40. Even if the foam raw material was one quarter the cost of aluminum, you would only save $30 per wing by using the foam. That doesn't count the small but additional expense of the wood and glue for the capstrips.

    The 3/4 x 3/4 x 1/8 angle for the aluminum spar caps, which is more cross section area than it needs, is $1.33 a foot (current ACS website). So for a 27 foot span single seater (2 12 foot long main wing panels, plus a narrow fuselage, plus some 12 inch non-structural wingtips) you are talking about 48 feet of extrusion, which is $64 for the main spars for two wings. Another 13 feet of 6 inch wide sheet for each wing gives you 13 square feet of aluminum for the shear web, or $32.50 for the shear web.

    2 13 foot span x 4 foot chord wings gives you 104 square feet of wing area, and doubling that gives you 208 square feet worth of wing skins. .016" aluminum (2017 ACS catalog, in 4 x 12 sheets) is $90 for a 48 square foot sheet. That's $1.87 a square foot, or $390... and thats's for an all metal fully sheeted wing (like the CH-701).

    So adding all this up : $390 for skins, $80 for the rib blanks, $32.50 for the shear webs, $64 for the spar caps... is $566 and change for the larger part raw materials to build two wings. Now let's add another 50% on top of that to account for the smaller parts, doublers, thicker attach fittings, rivets, stiffeners, etc. and you're at $850 for a pair of wings that will last a long time, able to sit outside, and don't need fabric or paint.

    The wing skins and the spar webs and the spar caps can all be pre-drilled to #40 holes on the CNC machine that cuts the parts. Only the holes in the rib flanges would have to be manually drilled. But the holes in ther skin save ALL the time of laying out the rivet pattern, you just use the skin holes as jig holes. The spars will already be close enough to Cleco together, and then once it is Clecoed you run the #30 drill through it to get a clean rivet hole. The biggest time suck is of course deburring the holes.
    "Everything in this book may be wrong."
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    "Common sense is so rare today, it should be reclassified as a superpower!"
    Derswede


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    Re: The Ranger, an easily built high wing LSA runabout

    Gluing aluminium is common practise in the automotive world these days.
    Glued joints out perform spot welds in steel
    https://www.repairerdrivennews.com/2...el-only-got-4/

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    Re: The Ranger, an easily built high wing LSA runabout

    Quote Originally Posted by Geraldc View Post
    Gluing aluminium is common practise in the automotive world these days.
    Glued joints out perform spot welds in steel
    https://www.repairerdrivennews.com/2...el-only-got-4/
    Has been for a long time. Back in about 1986 when I was working for VW of America we installed two automated lines that glued the inter and outer hood and rear hatch together of the Rabbit.
    Pops

    If its not there, it cost nothing, weighs nothing, and is 100% reliable.

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    Re: The Ranger, an easily built high wing LSA runabout

    I think adhesives, with good surface prep, are very common now. It's just getting the amateur to be be able to do this at home.
    In regards to the Cri Cri, according to Robert Cumberford Colomban's 9 year old daughter assembled, including bonding, the horizontal stab.

  14. #147
    Registered User Hot Wings's Avatar
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    Re: The Ranger, an easily built high wing LSA runabout

    Quote Originally Posted by Victor Bravo View Post
    I have it on good authority (from someone who genuinely has the scientific background to know this) that gluing aluminum is possible, but it does require a chemical procedure similar to Alodine.
    Your authority is both right....and wrong.

    They are right if you are making a structural bond between aluminum parts. If so the classic standard is BAC5555. It's a lot more involved than Alodine or FPLs phosphoric acid wash. There are companies that will do customer supplied parts and are licensed to use the Boeing process. Once the parts have been treated and primed they can be stored and shipped un-bonded. The subsequent bonding should be something that HBA level builders can do successfully.

    They are wrong, or more likely misinterpreted, in that it depends on what you are bonding to what. Bonding aluminum to foam needs to be looked at from a different perspective. Bond failures have basically 2 modes - adhesive and cohesive. Untreated aluminum bond joint failure can be either adhesive, or cohesive depending on several factors. Given good adhesives, loads less than the design limit and within temperature bounds failures are likely to be cohesive failure of the oxide layer. The standard wedge test outlined in BAC5555 and the equivalent ASTM standard demonstrate this failure mode.

    How does this all apply to aluminum foam bonds?

    It turns out that the cohesive failure mode of the oxide layer and the adhesive failure of the oxide/aluminum layer are both higher than needed to fail the foam in either tension or shear. This means that we should no longer be thinking in terms of bonding foam to aluminum but of foam bonded to the oxide layer.

    We still have to take the aluminum oxide layer into consideration because it is not a static layer. It can grow and 'move' over time. This could, theoretically, cause a bond failure, either cohesive or adhesive. The amount of degradation needed to be lower than the adhesive bond to the foam would likely be considerable.

    I have never found any papers of experiments with regard to this kind of oxide layer change effecting bond strength, other than one that claimed that oxygen could, and did, actually migrate through the aluminum to form an oxide layer under the bond if there was any moisture present


    Summation: Aluminum/aluminum structural bonds and aluminum/foam bonds are two different animals.

    Edit: After a good cup of tea; I should have noted that even with an aluminum/aluminum structural bond it's the oxide layer that controls the bond. The treatment process does not eliminate the oxide layer. It removes any existing layer and replaces it with one that is deposited in a controlled manner. That layer is then immediately primed to prevent any further oxide layer growth with a primer designed to be compatable with the bonding resin..
    Last edited by Hot Wings; March 2nd, 2019 at 01:58 PM.
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    Re: The Ranger, an easily built high wing LSA runabout

    This discussion is coming along quite nicely. I can even imagine what an airplane with glued aluminum wings might look like:

    http://www.bedecorp.com/bd-4c.html

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    Re: The Ranger, an easily built high wing LSA runabout

    All this talk of aluminum made me wonder whether aluminum HVAC sealing tape would be of any value for foam rib caps. I've used the Nashua for various tasks, although 3M and other companies also make it. I can attest to the toughness of Nashua's adhesive, given that I've had some that was exposed to extreme weather conditions for several years. It seems to stick to anything with stubborn tenacity.

    The thickness on Nashua's aluminum tape is advertised at 0.127mm (0.005"). One could go around a few times to build up a few layers; if it was absolutely necessary, 3 wraps would be about the equivalent of a 1/16" birch ply, if I'm calculating that correctly. The adhesive would add some weight.

    Nashua or 3M may carry a heavier tape. I haven't checked.

    I have one another comment. I keep seeing the term "XPS", which as I understand it stands for expanded polystyrene. On the other hand, I see photos in the discussion of standard styrofoam panels, which are not at all the same thing. I believe we're talking about styrofoam, and not XPS.

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    Registered User FritzW's Avatar
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    Re: The Ranger, an easily built high wing LSA runabout

    It's probably a moot point. On an design where your trying to shave off weight and cost it's hard to justify the shipping on 14' spars. Especially when you consider that both wing panels on the quick build wooden wing (including everything through *paint, even the struts) could ship in a single UPS box without any over weight or oversize charge. ...a QBWW with foam ribs is one option that ticks all the boxes
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