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Old Feb 02, 2005, 06:06 PM
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sr-71 foamy park jet

im trying to start from scratch here to build a flyable sr71 foamy hopefully i can get it to look some what close to the real thing here "a 3 dimensional look" i want to stay away from the whole shock flyer type single sheet fuse and wing type thing any help will be apreciated in this project
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Old Feb 02, 2005, 06:12 PM
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Bergen, Norway
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Drawings that might help....

Dryden Flight Research (NASA)

The EPS files are scalable without loosing quality!

Will be watching this one closely...

Any thought on power setup?

Ben_E
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Old Feb 02, 2005, 06:33 PM
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Stonewall, MB, Can
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Ever see how the Estes SR71 rocket is built?

If I ever build one IMHO I think that construction method would result in an awesome looking SR that is strong and light. They used 3 rocket tubes (which are light and readily available) and joined them with balsa for the structural wing parts. The wing between fuse and engine pod is extended all the way to the front to form the chine. We could use CF reinforced Depron or FFF easily enough. To get the curved fuse top and bottom they simply glue on some light card stock over the fuse and meeting the wing/chine on each side. Again we could substitute 1mm depron or whatever.
Should be plenty of room to hide gear inside quite nicely depending on how big you build it. Each engine pod tube would be a great setup for a twin pusher or even a twin tractor config. EDF's are a natch.

I could post a pic of my Estes SR if you like.
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Old Feb 02, 2005, 06:42 PM
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im gona try a pusher type with brushless himax 2024-4266 4.3-1 gr and a 3 cell 2600 li-poly however i just need a some help figuring out the proper size to make it "wing size " ive got a pretty good idea as to how im gona build it i just need to figure what would be the best dimensions to build it..
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Old Feb 02, 2005, 06:53 PM
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Quote:
Originally Posted by Hepdog
Ever see how the Estes SR71 rocket is built?

If I ever build one IMHO I think that construction method would result in an awesome looking SR that is strong and light. They used 3 rocket tubes (which are light and readily available) and joined them with balsa for the structural wing parts. The wing between fuse and engine pod is extended all the way to the front to form the chine. We could use CF reinforced Depron or FFF easily enough. To get the curved fuse top and bottom they simply glue on some light card stock over the fuse and meeting the wing/chine on each side. Again we could substitute 1mm depron or whatever.
Should be plenty of room to hide gear inside quite nicely depending on how big you build it. Each engine pod tube would be a great setup for a twin pusher or even a twin tractor config. EDF's are a natch.

I could post a pic of my Estes SR if you like.
yup good idea im thinking of a solid one piece wing that goes either aroung the fuse or over top and around it reinforced with balsa corners then layering foam on the sides top and bottom of the fuse to get the shape and sanding to contour in .. i just need best over all size for my setup or for a park flyer i have a good picture of top ,bottom, side viewthat o got off a thread where some one built one for a larger glow engine i just dont have a way to size them to what i would need once we come up with a good size,, i can go from there off top botom and side views
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Old Feb 02, 2005, 07:16 PM
PIV
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Lesmurdie, Perth, Western Australia
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This will be cool. As Jetset44 suggested for 100W, about 260 to 300in2 is about right, scale that up for the power plant you have. How much power? See Motocalc. Im off for a week but when I get back I might ProE model the fuse to get the waterlines. Once done I can scale to any size.
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Old Feb 02, 2005, 07:47 PM
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Quote:
Originally Posted by PIV
This will be cool. As Jetset44 suggested for 100W, about 260 to 300in2 is about right, scale that up for the power plant you have. How much power? See Motocalc. Im off for a week but when I get back I might ProE model the fuse to get the waterlines. Once done I can scale to any size.
acording to moto calc the power plant i have will work with a 300 sq in wing area.i listed the wing span to be 28" this may not be correct cause i dont know how many sq inches of wing area i am going to have if i scale up my drawing to have a 28" wing span i dont know how to calculate it on this wing however it listed my motor with a smaller gear ratio and prop than what i have to get sport type performance.

useing electric motor calculator i got these results
motor himax 2025-4200 4.3-1 gear ratio
10-8 apc prop
3 cell li-poly

comes out to --- 21 amps 209 watts in 166 watts out max efficiancy 79.5%
static thrust 47.3 oz
inflight thrust 22oz
prop pitch speed 58.9
this is the drawing i have
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Old Feb 02, 2005, 08:14 PM
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Jacksonville, Florida, United States
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Quote:
Originally Posted by Ben_E
Drawings that might help....

Dryden Flight Research (NASA)

The EPS files are scalable without loosing quality!

Ben_E
Sorry but I don't recognize EPS files...what reads them please?
lafjax
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Old Feb 02, 2005, 11:52 PM
PIV
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Lesmurdie, Perth, Western Australia
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Wing area for a delta is half times span (of projected leading and trailing edges for this wing) times chord at the centreline (project the leading and trailing edge in). Its usual to not count the fuselage area, but we could count the strake area, but I wouldnt, the bit extra area wont hurt. looks to me like about 25in span will be OK, please check.
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Old Feb 03, 2005, 02:24 AM
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that is 312 sq inches on this plane right ? please check not including the strake or loss of area from the fuse witch i dont think will matter to much ,,however the engine bays take up alot of wing area..about if im correct a little more than 87 sq inches loss of lifting surface on a 25 inch span this would put the actual wing area around if i am right some where around 225-226sq inches .. scale the rest of the plane to fit that wing size ... Whoa 50 " tip to tip sheew thats a long plane if i am right.. but she will be thin so hopefully this will help keep the weight down, if this is right and you guys think it can be done with these measurements i think i can start i just need a way to scale this drawing up to the right size 25 " wing span..50 " length .. man this thing wont like to fly slow and with a 25 inch span shes gona be touchy in the roll axis im sure ,,some how i think its gona be touchy up and down as well with the long strakes on the front im gona have to have to use realy low throws all the way around i think . Any body out there able to blow that drawing up to that size so i can get started?

any additional thoughts so far? im thinking mabe i should ad an inch or two to the width of the wing and mabe keep the nose scale width and shorten it a tad bit what do you think? im thinking this may help to make the plane fly better as a park flyer..
let me know .. im dieing to get started on cutting some foam ..
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Old Feb 03, 2005, 08:23 AM
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Take a copy of the file to Kinko's they do great work.
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Old Feb 03, 2005, 09:15 AM
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Quote:
Originally Posted by lafjax
Sorry but I don't recognize EPS files...what reads them please?
lafjax
Any cad program, Corell Drwa, Adobe illustrator. What format can you handle - I could convert them for you!

Ben_E
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Old Feb 03, 2005, 09:28 AM
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Got it!! Thanks
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Old Feb 03, 2005, 10:35 AM
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i do have auto cad 2000
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Old Feb 03, 2005, 11:08 AM
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SR -71 dxf file - You should be able to open it with Auto Cad 2000!

Ben_E
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