Probably true also. If engineered to take maximum advantage of the material. Cost effective in both material cost and build time. There is a trade of between finish and build time and maybe also minimum weight and build time.
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Neither, really, or at least not nearly as much as what "everyone knows" about moldless composites. When you save "finishing" for last, there's definitely a giant "bow wave" of work you've pushed back to last, and a lot of time spent filling and sanding, then rinse and repeat. But, if you follow the correct procedure and consider "finishing" from the very first moment hot-wire touches foam, the amount of "finishing" labor throughout the build is absolutely minimized. So much so, in fact, that I've heard it described as absolutely comparable to finishing and painting a sheet-metal airplane.
Most of the "thousands of hours of sanding" horror stories are from people who simply did it wrong, and thought "finishing" was something done at the end of the build.
TFF
Well-Known Member
I think a lot of original EZs were carved with an electric kitchen knife and then sanded. 1975 auto body work was about Bondo. Today we have dentless repair. What we know today makes it easier to do it right; the reputation is made the first few years when everyone was hungry for EZs. The belief of not having to be precise seems to be the biggest factor in all "new and easy to build designs" Usually the designers were masters of what they use, and could not believe anyone would be less.
I do largely agree, done right the finish will be just fine. Weight too. Designing for the material and process the finished item will look and preform really nice. Still, if examined closely it will show that the airplane is designed to be built quick and cheap by using the selected material and process. And that may not be a bad thing.
Hephaestus
Well-Known Member
If done following the techniques in FFF RC aircraft, it can be a bit of both really... When your fuselage is made up of 32$ of foam and a bottle of gorilla glue, and a serious defect is found - it's easier to rationalize scrapping the whole piece, and starting over. When it's thousands of dollars of material from AS&S - will take weeks to replace and months to rebuild - it changes perspectives.
Tab A into slot B just like an old die crush model, very simple tools, big slab sides that are perfect if you keep them that way...
The challenge becomes the hard points, it's not a huge challenge, but takes some extra thought. Finish like the little foamies can be 20/20 (20ft or 20mph, either way looks good enough) to show quality. Depends on the builders skills and desired finish. Some people want to fly, some people want to show off their "mad skills yo!".
And really it comes down to the fit and finish of joints & working the foams natural qualities while bending. Some will work the details some will just slap it together. One might look infinitely better, but does the air really notice the difference? (Ok yes it does, but it might not justify spending another decade on the build)
pictsidhe
Well-Known Member
This thread and another has me pondering a Coroplast ultralight... build up a coroplast wing and slide it over a carbon spar. Thermal expansion means it can't be bonded one.
I harvested a few dozen small pieces of Coroplast when it was in bloom last year, maybe it's time for me to start playing with it! Challenge number one, hot moulding it. Steam or hot air? I'll want to mould full 8'x4' sheets eventually so I need to think big. A bit of googling found one guy used his domestic oven at 320F to do a compound curve. Jury-rig a water heater for steam? That idea makes me nervous, though... Wallpaper steamers don't seem to be pressure capable. 0.024 mild steel or 0.032 5052 sheet is pretty cheap for moulds, especially if I can reuse the sheets for several moulds. Gentle curves won't deform them. Leading edges will.
I harvested a few dozen small pieces of Coroplast when it was in bloom last year, maybe it's time for me to start playing with it! Challenge number one, hot moulding it. Steam or hot air? I'll want to mould full 8'x4' sheets eventually so I need to think big. A bit of googling found one guy used his domestic oven at 320F to do a compound curve. Jury-rig a water heater for steam? That idea makes me nervous, though... Wallpaper steamers don't seem to be pressure capable. 0.024 mild steel or 0.032 5052 sheet is pretty cheap for moulds, especially if I can reuse the sheets for several moulds. Gentle curves won't deform them. Leading edges will.
Guess I missed this controversy ...
Missed the "other" , was Coroplast in DIY's airplane? I did not see that. I think that stuff is impossible to glue? Do you really want a duct taped aircraft? I think Lazar still uses double sided foam tape, .....not for me. Whats wrong with .016 2024-t3 alum. ?
Tiger Tim
Well-Known Member
That sounds like a lot of effort for not a lot of return. I've pondered corrugated plastic before and I wonder if the thicker stuff would work okay for tail feathers. If you were really daring you could even just cut open a cell on one side and use the other side as your hinge. As for wings, at UL speed you might just be able to get away with a faceted airfoil with a bunch of kinks in the surface.
Mark Stull had a thread called " lexan sheeted wings".
https://www.homebuiltairplanes.com/forums/showthread.php?t=3553&page=5
https://www.homebuiltairplanes.com/forums/showthread.php?t=3553&page=5
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pictsidhe
Well-Known Member
The other thread was about Acrylic sheeting Acrylic sheeting
I'm pondering draping coroplast over a hot sheet metal mould. The mould is a 8x4 sheet of thin metal, heated likely with steam. The mould only needs a few wooden ribs to get it's shape. Hopefully, i can reuse a metal sheet several times. leading edges are going to be single use. Gravity drapes the coroplast over it. Coroplast ribs, maybe cut with CNC, it wouldn't need many as the coro skin would be pretty stiff anyway. I've never built an airplane, but have built many other things. Low parts count and simple shapes really, really speeds things up. Moulding the coro is the current big hurdle. if I build a CNC, the ribs will takes seconds to cut, as will ply ribs for the wingskin moulds. plan B on moulding the skins is to get UV resistant black correx, drape over metal again, but heat the coro with infra red lamps. Plan C is to build a giant oven, might be simplest, though bulky and my paranoid side is telling me to do that outdoors... Over in Europe, foamed concrete blocks are a big thing and would be ideal. They can be stacked dry. Over here, I'd likely have line a wooden box with fibreglass batts.
Coroplast can be glued a few ways, but you do need special glues. There are a couple of hot glues that work well. I'd favour these where it's possible to use them as you get full strength in seconds. Some fairly simple gluing jigs from straight bits of wood should produce a useable wing. There are a couple of CA adhesives that work too. Might be needed when I can't get a glue gun to the joint. Coroplast has the surface activated by corona discharge. This really helps stuff like CA glue and paint stick. My current crop of Coroplast is a year old and the treatment has likely dissipated, but they'll do for moulding tests.
4mm coroplast is 0.143lb/sqft. For a 150sqft wing, that'd be around 45lb of skin. Not too hideous as it's won't need half as much support as fabric. 5mm is .204lb/sqft, 6mm is 0.284 lb/sqft, getting a bit heavy for sheeting the whole thing, but might be good on leading edges.
For hinges, I was thinking of squishing the coro flat for the hinge section with a suitably weighted bar when it is being draped, the stuff has some impressive fatigue properties
This thread is a inspiring as it's about model airplane tech being used for a man carrier.
I'm pondering draping coroplast over a hot sheet metal mould. The mould is a 8x4 sheet of thin metal, heated likely with steam. The mould only needs a few wooden ribs to get it's shape. Hopefully, i can reuse a metal sheet several times. leading edges are going to be single use. Gravity drapes the coroplast over it. Coroplast ribs, maybe cut with CNC, it wouldn't need many as the coro skin would be pretty stiff anyway. I've never built an airplane, but have built many other things. Low parts count and simple shapes really, really speeds things up. Moulding the coro is the current big hurdle. if I build a CNC, the ribs will takes seconds to cut, as will ply ribs for the wingskin moulds. plan B on moulding the skins is to get UV resistant black correx, drape over metal again, but heat the coro with infra red lamps. Plan C is to build a giant oven, might be simplest, though bulky and my paranoid side is telling me to do that outdoors... Over in Europe, foamed concrete blocks are a big thing and would be ideal. They can be stacked dry. Over here, I'd likely have line a wooden box with fibreglass batts.
Coroplast can be glued a few ways, but you do need special glues. There are a couple of hot glues that work well. I'd favour these where it's possible to use them as you get full strength in seconds. Some fairly simple gluing jigs from straight bits of wood should produce a useable wing. There are a couple of CA adhesives that work too. Might be needed when I can't get a glue gun to the joint. Coroplast has the surface activated by corona discharge. This really helps stuff like CA glue and paint stick. My current crop of Coroplast is a year old and the treatment has likely dissipated, but they'll do for moulding tests.
4mm coroplast is 0.143lb/sqft. For a 150sqft wing, that'd be around 45lb of skin. Not too hideous as it's won't need half as much support as fabric. 5mm is .204lb/sqft, 6mm is 0.284 lb/sqft, getting a bit heavy for sheeting the whole thing, but might be good on leading edges.
For hinges, I was thinking of squishing the coro flat for the hinge section with a suitably weighted bar when it is being draped, the stuff has some impressive fatigue properties
This thread is a inspiring as it's about model airplane tech being used for a man carrier.
Coroplast works with contact cement. I suspect solvents would work too...
pictsidhe
Well-Known Member
I don't know of any solvents that will touch Coroplast. It's a polypropylene-polyethylene copolymer, very inert stuff.
When I've joined polythene and polypropylene before, I've always welded it. Probably why I favour hot glue on Coroplast, It's a bit thin for me to weld easily but should give all the strength.
I've seen some reports on solvent type glues failing abruptly at low temps after being otherwise strong. A freezer test is therefore in order for any glues used.
Actually, I lied about only welding, I've used a duct tape a few times. It's glue could be worth investigating. Some stick far better than others.
When I've joined polythene and polypropylene before, I've always welded it. Probably why I favour hot glue on Coroplast, It's a bit thin for me to weld easily but should give all the strength.
I've seen some reports on solvent type glues failing abruptly at low temps after being otherwise strong. A freezer test is therefore in order for any glues used.
Actually, I lied about only welding, I've used a duct tape a few times. It's glue could be worth investigating. Some stick far better than others.
TFF
Well-Known Member
From building models, I would want mechanical fasteners. It is tough stuff. Like before, I would experiment with 3M VHB tape. I have not tried it on CP but I probably would have, if I thought of it when messing with the stuff. My friend really liked the stuff because he could build a new model every 2 weeks. Lots of thick CA, which you would clamp, and then after a min or two maybe 5, hit it with the accelerator. You had to wait to get the glue in the pores, what small ones there were. It would pop apart if you did it faster. We cleaned the stuff with acetone; it just smiles right back.
Contact cement, tape, other glues, tape is probably your best, as you can hopefully see it start to fail and hit the parachute. No thanks, If you want to be at 100 ft in any craft you need to know it is going to stay together. Now aluminum and rivets........016 .23 lb/ft sq. Aluminum ribs, and fabric lots less weight. Testing and proving rivets/large washers and Coroplast might be an interesting project.
Coroplast is quite heavy, and not very stiff. But.. I think it might have a longer exposed life than fabric.
H
Hole in the Ground
Writing this out seems silly now but I’m going to ask this anyway. So peter built up his ings using pink foam and a metal spar. I can see the purpose of that- Foam is light and can hold the aerofoil shape under flight loads better than a canvas wing with ribs would. But what benefit did he gain from using foam on the fuselage? He built up a wooden frame on the inside anyway. How much extra rigidity did he get from the foam covering compared to a wood and canvas or canvas type fuselage? Could he have made a similarly strong and simple fuselage using wood and canvas?
I love what he did and I think the great thing about this forum is that we have the expertise to identify the good ideas and the combined mental horsepower to improve on them. So I’ve been pondering how I would build a similarly simple aircraft. But I can’t understand the choice of foam for the fuselage.
Thoughts?
I love what he did and I think the great thing about this forum is that we have the expertise to identify the good ideas and the combined mental horsepower to improve on them. So I’ve been pondering how I would build a similarly simple aircraft. But I can’t understand the choice of foam for the fuselage.
Thoughts?
radfordc
Well-Known Member
- Joined
- Feb 5, 2008
- Messages
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Of course he could. He could have also used riveted aluminum sheet, welded steel tube, or fiberglass composite....but he didn't. He probably chose the materials he was most familiar with and most comfortable working with. He also may have chosen to emulate model airplane construction just to prove a point.
H
Hole in the Ground
I thought that might be part of the reason. But he did glass it and use a fair amount of metal work, both outside his modelling comfort zone. You are probably right though. His plane, his solution.
pictsidhe
Well-Known Member
It's tough stuff. it should be more resistant to nosey pokers as it bends an awful lot before being damaged. People tend to get nervous about something that clearly yields. A nice, light stiff carbon sandwich skin will suddenly go crunch after relatively little deflection. Nosey pokers confuse stiffness with strength.
It's really cheap, too!
While it isn't awesome stuff, it's still much stiffer than fabric.
I found some data on Coroplast, HDT is 194F at 66psi. That makes atmospheric pressure steam a viable heating medium for bending it
The 3mm has 0.008" thick flutes, 4mm is 0.009" 5mm is a jump up to 0.013". 5mm is tempting for leading edges.
It's really cheap, too!
While it isn't awesome stuff, it's still much stiffer than fabric.
I found some data on Coroplast, HDT is 194F at 66psi. That makes atmospheric pressure steam a viable heating medium for bending it
The 3mm has 0.008" thick flutes, 4mm is 0.009" 5mm is a jump up to 0.013". 5mm is tempting for leading edges.
