HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Jul 05, 2009, 04:01 PM
Registered User
Joined Jul 2009
14 Posts
Help!
Challenge

Hey guys, I have to make 5 lb UAV or just say, RC plane with less than 3 feet wingspan. I am also choosing a conventional design rather than flying wing or anything thats almost impossible. It's a design project, so have to cut airfoil and choose prop system and have to meet the payload and endurance requirements.
Is there any foam material out there which I can use rather than using somthing complex like balsa, or fiberglass? There is no limit on spending. Just throw ideas or names of the foam that I can use.

Thanks.
Nekster is offline Find More Posts by Nekster
Reply With Quote
Sign up now
to remove ads between posts
Old Jul 05, 2009, 04:14 PM
"I Am The Animal!" in training
helifryer's Avatar
Winston-Salem, NC
Joined Sep 2008
1,008 Posts
depron.
epp.
FFF (fanfold foam)

i think that someone did a plane that was a heavy lifter or something like that.....search for it.
helifryer is offline Find More Posts by helifryer
Reply With Quote
Old Jul 05, 2009, 04:24 PM
it WILL fly! someday....
Richard_s's Avatar
Slovakia
Joined Aug 2008
448 Posts
you mean 5lb ~ 2.3kg and 3ft ~ 91,4cm ??
Richard_s is offline Find More Posts by Richard_s
Reply With Quote
Old Jul 05, 2009, 04:44 PM
Registered User
Joined Jul 2009
14 Posts
yeah, limit is 3 feet = 91.44 centimeter, and 5 lbs = 2.27 kg, which includes powerplant and payload. Also am wordering what would be the foam's weight for that much airplane, which will also add some weight (especially if it is high density foam).

Thanks
Nekster is offline Find More Posts by Nekster
Reply With Quote
Old Jul 05, 2009, 05:30 PM
it WILL fly! someday....
Richard_s's Avatar
Slovakia
Joined Aug 2008
448 Posts
This won`t answer your question, just some of my thoughs.

First, I would get mass of all payload and powerplant. Then I`d calculate wing loading for conventional form, delta, and flying wing. With payload near 5lbs, you will end up using a lot of wood/carbon/fiberglass anyway. And about flying wings - they are more effective than any other aircraft, just because they have no tail, which in fact, adds no lift - only a drag, mass, and needs fuselage to be fixed on. Flying wing has about 20-25% higher lift coefficient than conventional airplane. But with such high wing loading.... dunno . I`d go for either delta with max possible wing area, or build a tandem/triplane
Richard_s is offline Find More Posts by Richard_s
Reply With Quote
Old Jul 05, 2009, 06:34 PM
Registered User
Joined Jul 2009
14 Posts
Quote:
Originally Posted by helifryer
depron.
epp.
FFF (fanfold foam)

i think that someone did a plane that was a heavy lifter or something like that.....search for it.
Yeah there was SAE Heavy lifting competition, but they had like 10 feet span.
Nekster is offline Find More Posts by Nekster
Reply With Quote
Old Jul 05, 2009, 06:45 PM
it WILL fly! someday....
Richard_s's Avatar
Slovakia
Joined Aug 2008
448 Posts
3ft triplane = 9ft, that might work
Richard_s is offline Find More Posts by Richard_s
Reply With Quote
Old Jul 05, 2009, 06:53 PM
Registered User
Joined Jul 2009
14 Posts
Quote:
Originally Posted by Richard_s
This won`t answer your question, just some of my thoughs.

First, I would get mass of all payload and powerplant. Then I`d calculate wing loading for conventional form, delta, and flying wing. With payload near 5lbs, you will end up using a lot of wood/carbon/fiberglass anyway. And about flying wings - they are more effective than any other aircraft, just because they have no tail, which in fact, adds no lift - only a drag, mass, and needs fuselage to be fixed on. Flying wing has about 20-25% higher lift coefficient than conventional airplane. But with such high wing loading.... dunno . I`d go for either delta with max possible wing area, or build a tandem/triplane
I guess there is no compressibility effect here at low reynold's number, so will just a rectangular wing with no sweep

But, do you think so I will have to use Balsa, Fiber, Carbon? Becoz all these years I have paid enough attention to Aerodynamics and propulsion classes, but have not paid attention to Structures. And I have taken this challenge to design a UAV in one month of July. So, have to do something easiest. What you think about EPP or Depron like what Helifryer is saying in the second reply.
Nekster is offline Find More Posts by Nekster
Reply With Quote
Old Jul 05, 2009, 06:53 PM
Registered User
Joined Jul 2009
14 Posts
No dude Triplane of 3 feet is crazy
Nekster is offline Find More Posts by Nekster
Reply With Quote
Old Jul 05, 2009, 07:13 PM
it WILL fly! someday....
Richard_s's Avatar
Slovakia
Joined Aug 2008
448 Posts
Epp is springy, needs lots of stiffening, and it doesn`t break in crash. I build with depron, stronger, but breaks easily (quick repairable anyway). To be honest, I dunno what kind of structure would withstand 5lbs. Count payload mass and from that determine wing loading with stall speed you can handle, and from that you can get aspect ratio. From my calculations, with 3ft wing with constant chord of 12" and 5lbs total mass, you get about 26oz/sqft wing loading and about 25mph stall speed. that seems pretty fast, and I don`t know how that wing aspect ratio will behave... tough task dude
Richard_s is offline Find More Posts by Richard_s
Reply With Quote
Reply


Thread Tools