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#21
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Why no plywood monocoque homebuilts?
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#22
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Why no plywood monocoque homebuilts?
Ernest Christley wrote: wrote: If you designed an aircraft to leverage modern production lines, what would it be made of? Thanks! Matt Fairy dust 8*) You have to consider the economics of the thing. Modern assembly lines are set up and expected to produce hundreds of thousands/yr if not millions/yr of a product. We're talking a yearly volume on the scale of the entire US GA fleet. One airplane for every registered pilot. The most you could hope with any airplane design is more on the order of 100s/yr. The type of tooling you speak of takes as much R&D as an airplane design. All that cost has to be amortized somewhere in a reasonable amount of time. You very quickly get to the point where you can roll off airplanes that have never been touched by human hands, but they're so expensive to pay for the tooling that no one can afford them. I understand your argument, and it is absolutely valid. But humor me for a moment, and lets assume that a market could be found. Call me an optomotrist, but I think there might still be a market, even if the pilots don't exist at the moment. And just having the work done by a machine doesn't get you home free. Machines break. They are usually out of calibration, and they rarely work as designed the first time. So now you're paying people to watch the machines. Machines that makes airplanes that can't be sold any faster than it took the people to make the machines. Understood. But speculation is the inbred half stepbrother of invention, (or something), and I might speculate that their is an abundance of machines being discarded as modern factories go to third and fourth generation robotics, and that much of it can be had for a song. SA gave a tour of the Cirrus factory a month or two back. I think they have it right. Automate the simple things. Have humans do the complicated things. Design the airplane with the lowest possible parts count. I suspect that they will slowly add more automation as the capitol budget allows. What parts did they automate? -Thanks! -Matt |
#23
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Why no plywood monocoque homebuilts?
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#24
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Why no plywood monocoque homebuilts?
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#25
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Why no plywood monocoque homebuilts?
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#27
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Why no plywood monocoque homebuilts?
wrote in message oups.com... wrote: Suprisingly I keep coming back to wood as material for mass production since the whole of the structure could be made of one material. There are obvious logistic benefits there, and I think most wood techniques could be practically achieved robotically. Wood, especially good wood, is getting scarcer all the time. Consistently good wood is hard to find. It's the reason ladder manufacturers went to aluminum and/or fiberglass a long time ago. The big Sitka Spruce and other types of trees that gave us good aircraft-grade wood mostly went to build houses a long time ago when it seemed we'd never run out of the stuff. What's left is protected in parks. The airplanes mentioned in the original post were, I'm pretty sure, cold molded - a very labor intensive process of laying individual strips of veneer - each trimmed to shape - over a plug and either stapled of vacuum bagged until the laminate cures. But other methods exist to build wood stressed skin structures. e.g. "Constant Camber" is a boat building method where full sheets of veneer are placed in a somewhat generic female mold and vacuum bagged - the mold does not have compound curves, but by changing the position of the layup, you get different shaped panels that then can be assembled into whatever. Another option is "tortured plywood" where thin plywood is forced into a compound shape. Amateur boat builders are also using a "stich and glue" technique to make plywood hulls - I wonder how long before someone tries it for an airplane? Or - consider a structure like a KR-2 - a plywood box with some sticks to reinforce. Not a swoopy looking as a Mosquito bomber, but it works and it doesn't require "premium" lumber The hard part would be to come up with a reasonable replacement for the spars in the wings. To avoid the big expensive spruce planks, one might have to consider an engineered product like Laminated Veneer Lumber (LVL)... -- 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. |
#28
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Why no plywood monocoque homebuilts?
"Capt. Geoffrey Thorpe" The Sea Hawk at wow way d0t com wrote The hard part would be to come up with a reasonable replacement for the spars in the wings. To avoid the big expensive spruce planks, one might have to consider an engineered product like Laminated Veneer Lumber (LVL)... Have you ever used those? They are HEAVY, with a capital "H". More fitting would be something like an engineered product such as "silent floor" joists, which is best described as a wood "I" beam. A cheaper wood, like fur could be used, because the wider flange top and bottom of the "I" is the only part that is real wood, and there is not that much volume of wood to incur very much weight penalty. Holes can be put in the plywood web to help lighten it, with very minimal strength loss. Of course, this is a practice very similar to what is currently being used in some homebuilt designs, today. g A box spar is one of the best uses of strength to weight for spars, not using a solid plank. The amount of real wood, top to bottom and spanwise varies, so there is no extra wood where it is not needed, thus giving maximum strength to weight. Also, you do not have to use expensive Sitka Spruce, and if you do, you can cut up smaller (cheaper-no waste) pieces, and splice them, and laminate them, to get all of the grain going in the right direction. This all gets a bit labor intensive, but semi-skilled labor can be taught to make spars, with enough repetition for mass production to be cost effective. I like the idea of wood mass produced airplanes, but I fear there are too many advantages for other materials, and pre conceived notions against wood airplanes to make them fly. (pun intended) g -- Jim in NC |
#29
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Why no plywood monocoque homebuilts?
Morgans wrote:
"Capt. Geoffrey Thorpe" The Sea Hawk at wow way d0t com wrote The hard part would be to come up with a reasonable replacement for the spars in the wings. To avoid the big expensive spruce planks, one might have to consider an engineered product like Laminated Veneer Lumber (LVL)... Have you ever used those? They are HEAVY, with a capital "H". SNIP -- Jim in NC Jenny Craig strikes again :-) I am still very intriqued by filament winding. Spars would probably be most obvious use of this technology. Take a look at the pictures on this page to get an idea why. http://www.boatdesign.net/forums/sho... t=1774&page=2 Doesn't that kindof suggest the ability to make a whole spar, wing, fueselage or control surface in one shot? I am presuming scaled composites uses something similar but bigger. I've seen pictures of the system NASA uses for booster casings, they stand about 20 ft. tall if I remember correctly. I will be checking the local yellow pages to see if there are any mast-makers where I live. I'd like to take a closing look at a system like this. -Matt |
#30
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Why no plywood monocoque homebuilts?
In article .com,
" wrote: Morgans wrote: "Capt. Geoffrey Thorpe" The Sea Hawk at wow way d0t com wrote The hard part would be to come up with a reasonable replacement for the spars in the wings. To avoid the big expensive spruce planks, one might have to consider an engineered product like Laminated Veneer Lumber (LVL)... Have you ever used those? They are HEAVY, with a capital "H". SNIP -- Jim in NC Jenny Craig strikes again :-) I am still very intriqued by filament winding. Spars would probably be most obvious use of this technology. Take a look at the pictures on this page to get an idea why. http://www.boatdesign.net/forums/sho...11160b889f2560 2fba&t=1774&page=2 Doesn't that kindof suggest the ability to make a whole spar, wing, fueselage or control surface in one shot? I am presuming scaled composites uses something similar but bigger. I've seen pictures of the system NASA uses for booster casings, they stand about 20 ft. tall if I remember correctly. I will be checking the local yellow pages to see if there are any mast-makers where I live. I'd like to take a closing look at a system like this. -Matt Actually, filament winding would be a poor choice for spars, as the filaments should run primarily parallel to the spar and be concentrated at the top and bottom. You do need some in the webs, to handle shear loads, but an "I" section is the most efficient. A tubular spar for a wing is also a poor choice, as it concentrates a lot of its tensile strength at its center, where it doesn't get much loading. A mast is a different story, as it is expected to take similar bending loads in all directions; a spar does not. |
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