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#1
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Weight saving exercise.
I have to begin making a few decisions on how to drop a few pounds (off my
butt and my airplane!) For one, I'm considering making the composite tank as outlined in Tony Bengelis' book. This would be the foam/glass sandwich he describes. Questin is, is it lighter than the aluminum tank specified in my plans? I'm sure part of it is how much resin you lather on, but is it possible to save a couple of pounds here? Leaving the wieght aside, it's an attractive looking propostion. By the way, the tank is a removable wing tank, about 4'by 2' by 5". Next, what's the lightest practical covering? Biplane, weighs about 1450 lbs, redlines at 150 mph. In other words, what's the lightest system for a cub type machine? Finally, Wheels and brakes. They need to be reasonably robust and the plans call for cessna type axles, wheels and brakes, but can imake any significant savings by subsitituting something else? I don't want to put plastic wheelbarow whels on , by the way! I'm talking about maybe substituting cub, luscombe,whatever might be suitable which will give me a few pounds. any suggestions aobut these or any other tricks anyone might know greatly appreciated! |
#2
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Hi,
I don't think you save weight by using glass/foam, maybe if you use the Kevlar/glass combo fabric. For wings use dacron 2,4 oz and not to much paint. use a wood or composite prop not aluminum for the rest of the body, use meat, fat, egg, fish, vegetable, fruit. stay out of rice, potatoes, pasta, bread (Atkinson method) Jan Carlsson www.jcpropellerdesign.com "Fortunat1" skrev i meddelandet ... I have to begin making a few decisions on how to drop a few pounds (off my butt and my airplane!) For one, I'm considering making the composite tank as outlined in Tony Bengelis' book. This would be the foam/glass sandwich he describes. Questin is, is it lighter than the aluminum tank specified in my plans? I'm sure part of it is how much resin you lather on, but is it possible to save a couple of pounds here? Leaving the wieght aside, it's an attractive looking propostion. By the way, the tank is a removable wing tank, about 4'by 2' by 5". Next, what's the lightest practical covering? Biplane, weighs about 1450 lbs, redlines at 150 mph. In other words, what's the lightest system for a cub type machine? Finally, Wheels and brakes. They need to be reasonably robust and the plans call for cessna type axles, wheels and brakes, but can imake any significant savings by subsitituting something else? I don't want to put plastic wheelbarow whels on , by the way! I'm talking about maybe substituting cub, luscombe,whatever might be suitable which will give me a few pounds. any suggestions aobut these or any other tricks anyone might know greatly appreciated! |
#3
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"Jan Carlsson"
: Hi, I don't think you save weight by using glass/foam, maybe if you use the Kevlar/glass combo fabric. For wings use dacron 2,4 oz and not to much paint. use a wood or composite prop not aluminum for the rest of the body, use meat, fat, egg, fish, vegetable, fruit. stay out of rice, potatoes, pasta, bread (Atkinson method) He he, thanks,. I've been poking around th eAircraft Spruce site trying to figure out how much a bare composite tank is and it loks to be almost exactly the same as an aluminum one. I might still do it because I don't realy want to build an aluminum one and the composite loks easy. The prop's a done deal, though, Fairly large Ham Standard ground adjustable! Very heavy. If I don't get the performance out of it, I might try a wooden one though if this one doesn't work out. The fabric and finish sound god though! thanks |
#4
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Bryan Martin
sednews:BE693745.3CE41%bryanmmartinNOSPAM@comcast. net: You probably won't save any weight with a fiberglass tank. Homemade fiberglass lay-ups tend to be a lot heavier than aluminum for the equivalent strength. The big advantage of fiberglass isn't weight, it's the ability to easily form it into complex shapes. OK, thanks. I wasn't actually thinking of a layup, but a foam core construction made of foam sheet coverd in two layers of glass cloth each side amd made up into box. Looks like it should be light enough, but I can't tell how much epoxy i'm going ot need. The tank would be about 23 Sq feet in surface area, one side, of course, si double it and add a bit for baffles and I need to glass and epoxy about 50 sq. feet of 1/4 inch foam. any notion how much epoxy is needed? I've only ever done little patching jobs with epoxy |
#5
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You can probably make a little bigger tank in composite, I have made 2 using
wet lay-up over a foam plug, ((one with plastic cover material for buildings) and one I put gasoline in the foam and scraped the gunk out) no foam sandwich in the walls, and a couple bulkheads in the tank, and a large sump with drain and outlet for the fuel line. Used 3-4 layers of 300-400 gram fibre glass, the epoxy is about the same amount as the glass. Jan "Fortunat1" skrev i meddelandet ... Bryan Martin sednews:BE693745.3CE41%bryanmmartinNOSPAM@comcast. net: You probably won't save any weight with a fiberglass tank. Homemade fiberglass lay-ups tend to be a lot heavier than aluminum for the equivalent strength. The big advantage of fiberglass isn't weight, it's the ability to easily form it into complex shapes. OK, thanks. I wasn't actually thinking of a layup, but a foam core construction made of foam sheet coverd in two layers of glass cloth each side amd made up into box. Looks like it should be light enough, but I can't tell how much epoxy i'm going ot need. The tank would be about 23 Sq feet in surface area, one side, of course, si double it and add a bit for baffles and I need to glass and epoxy about 50 sq. feet of 1/4 inch foam. any notion how much epoxy is needed? I've only ever done little patching jobs with epoxy |
#6
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How did you get to this point in the first place, maybe based on that
we can make some suggestion. Was the design overweight by design or was it over built? How close is the empty weight to that of the prototype? |
#7
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#8
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Richard Riley
: On 25 Mar 2005 09:07:19 GMT, Fortunat1 wrote: :Bryan Martin :sednews:BE693745.3CE41%bryanmmartinNOSPAM@comcas t.net: : : You probably won't save any weight with a fiberglass tank. Homemade : fiberglass lay-ups tend to be a lot heavier than aluminum for the : equivalent strength. The big advantage of fiberglass isn't weight, : it's the ability to easily form it into complex shapes. : :OK, thanks. I wasn't actually thinking of a layup, but a foam core :construction made of foam sheet coverd in two layers of glass cloth :each side amd made up into box. Looks like it should be light enough, :but I can't tell how much epoxy i'm going ot need. The tank would be :about 23 Sq feet in surface area, one side, of course, si double it :and add a bit for baffles and I need to glass and epoxy about 50 sq. :feet of 1/4 inch foam. any notion how much epoxy is needed? I've only :ever done little patching jobs with epoxy Figure, as a rule of thumb, the epoxy will weight 50-60% of the glass. But for a tank, that fraction goes up, since you want the inside laminate very wet and no leaking dry spots. Aluminum will be lighter. OK, thank you very much.. Sold. |
#9
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"Jan Carlsson"
: You can probably make a little bigger tank in composite, I have made 2 using wet lay-up over a foam plug, ((one with plastic cover material for buildings) and one I put gasoline in the foam and scraped the gunk out) no foam sandwich in the walls, and a couple bulkheads in the tank, and a large sump with drain and outlet for the fuel line. Used 3-4 layers of 300-400 gram fibre glass, the epoxy is about the same amount as the glass. OK thanks. Nice to have a few figures to work with. I can see there's no weight advantage, definitely. Thanks again to all! Any other weight saving suggestions welcome, though! |
#10
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"Fortunat1" wrote in message
. . . so I'm going to have to learn to build an aluminum tank.. Anyone know of a resource to show me how? The books by Tony Bingelis have excellent tips on this. http://www.amtbooks.com/sport_plane_...on_techniq.htm Rich Shankland |
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