HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old May 24, 2006, 04:09 PM
Registered User
airdawg's Avatar
Encino, CA
Joined Apr 2006
109 Posts
Discussion
How come most bluecor/depron wings are built w/out an airfoil?

Greetings,

I'm new to the whole cad plans and self fabrication, I've just recently started to make a few from plans I've drawn up. I've noticed that most people use flat depron/bluecor wings with no airfoil. It can't all be about weight savings? Does a 2 piece wing with airfoil make much if any difference in bluecor/depron projects in reguards to in flight performance? I've also noted everyones about a flat fuselage too. Since its the norm what are the compelling reasons to build this way? Doesn't an airfoil help at all?
airdawg is offline Find More Posts by airdawg
Reply With Quote
Sign up now
to remove ads between posts
Old May 24, 2006, 05:18 PM
Obsessive Compulsive
CptanPanic's Avatar
Lake Worth, FL
Joined Feb 2005
99 Posts
The reasons for no airfoil is not to save weight, but it is way easier, and with an airplane so light if flies on flat wings fine.
CptanPanic is offline Find More Posts by CptanPanic
Reply With Quote
Old May 24, 2006, 09:22 PM
brennanj2
brennanj2's Avatar
Australia
Joined Mar 2005
380 Posts
Airdawg,
You can always build with an airfoil, either single sided ie out of one peice of depron or cellfoam or double sided out of 2. You can also shape an airfoil out of blufoam. There are lots of threads explaining how to do this.

If the motor has enough power it will pull a flat bit of ply through the sky, we used to do that with control line flying in the old days. But for an aircraft to fly "correctly" you need an airfoil of some discription to generate the necessary lift to keep the model in the air and to counteract the forces of drag and gravity.

The idea of a flat fusulage is that it has the correct profile and from the side looks like the intended plane. It is quick, cheap and easy to build. Where this type if model "falls over" is when viewed from the front and or back. Then it looks like what it is a "profile model".

Look at some other plans there are masses around most can be converted to creation in foam. It is just another building material.

Hope that helps.

John
brennanj2 is offline Find More Posts by brennanj2
Reply With Quote
Old May 25, 2006, 12:10 AM
BOSS
j_z_123's Avatar
New Jersey (excl EWR), United States
Joined Apr 2002
4,984 Posts
A flat wing is still an airfoil.

It's just not as efficient at producing lift. Thus, the plane needs to fly at a slight angle of attack. This is why many foamies are no where near as precise while flying, compared to a similar plane with a conventional airfoil.

Build time, ease of construction, and weight all play a factor as to why they became so popular. If the plane your planning on building uses a flat wing, it should still fly fine. It will just not fly as precise and or as fast as the same plane with a conventional airfoil.

Hope that helps.

Jon
j_z_123 is offline Find More Posts by j_z_123
Reply With Quote
Old May 25, 2006, 03:51 AM
Registered User
elfwreck's Avatar
United States, CA, Oakland
Joined Dec 2002
2,336 Posts
Hey now,
How 'bout this. FFF models got trendy about the same time 3D got trendy. In the high alpha games like 3D and the very slow speeds they do fly at, the renolds numbers are so low it doesn't make a lot of difference.
So, since many folk wre building FFF as 3D trainers it didn't make sense to build airfoils, same with the profile fuse, it works good enough for a trainer. The fasion just caught on.

If you really want an airfoil a cheap and sleasy one I like is to use the fold in the FFF as the leading edge, mount a spar about a third of the way back and glue the trailing edges together. You can cut them with an electric knife to half the original thinkness before you glue hem so the ailerons match the trailing edge. Takes ten minutes to build and makes a nice, clean symetrical wing as thin or fat as you make the spar.
RobII
elfwreck is offline Find More Posts by elfwreck
Reply With Quote
Old May 25, 2006, 09:22 AM
Crash Master
Gene Bond's Avatar
Indianapolis, IN
Joined Sep 2001
16,632 Posts
The flat-panel airfoils are fine for narrow speed ranges, where they are actually a symetrical airfoil. The problem comes when you want to fly slow and fast with the same plane, as the CoL shifts with speed w/o a thicker airfoil... I suppose bubble separation and all that techo-stuff are the reasons, but regardless, it's a tough blancing act as you pick up the speed.

We've been doing profiles for longer than I have been involved in the hobby. The GWS Stik series, and the Roadkill Series are just a few examples. These have single surface underchambered airfoils (not quite so with the balsa Roadkills, but close enough). These underchambered airfoils are actually pretty efficient for lift/drag/weight. Covering the bottom of the wings decreases lift and drag, but increases weight... so the will fly faster, but won't fly as slow. Thus you begin the trade-off game. What's the goal? Design for it.
Gene Bond is offline Find More Posts by Gene Bond
Reply With Quote
Old May 25, 2006, 11:29 AM
Or am I...
Bournemouth, Dorset, UK
Joined Jan 2005
2,461 Posts
Ok. Steve/Jetsett44 has explained this many times in his parkjet threads in the pusher jet sections. A search there may yeild more spesific results. But a flat plate is just a very thin airfoil. There is no part of it which you can say that makes it not. By sanding the front of the LE round you smoothen the airflow and decrese drag and get a slight airfoil effect. And even if you dont sand it its still an airfoil. Its just at the sizes "we" build the effects arnt too noticeable to make any diffrence. but the time it takes to build it goes up alot with a standard rib wing when compared to a flat one. and its also a lot easier to repair
im-sad is offline Find More Posts by im-sad
Reply With Quote
Old May 26, 2006, 07:58 AM
gpw
“There’s no place like Foam”
gpw's Avatar
United States, LA, New Orleans
Joined Jul 2002
24,161 Posts
The Flat airfoils were also extremely efficient for the manufacturers , as they didn't have to do anything (like bottled water)except the decorating , and packaging ... On a piece of flat foam ...
That's why you see so many flat wing kits and very few airfoiled ...advertising ...money...profits
HOWEVER , at the Rn that we fly at , a slightly undercambered airfoil is MOST efficient (Scientific Testing )... I've found GeneBonds 4% to be an ideal airfoil for our size planes ...They fly even well inverted...and as he mentioned , have a broad speed range and better than average glide ratios...
The flat planes do however act more neutral in full blown 3D maneuvers , at very low (indoor ) speeds....That however is all they do ....at speed as Gene stated , they get squrriley ...TRUE!!!! ....
For super EASY airfoiling , make a BendFoam jig ,outta' two broomsticks and some scrap wood ... you'll never regret it ...
gpw is offline Find More Posts by gpw
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Help! How come there are no Canadian Depron suppliers? iam Foamies (Kits) 13 Mar 30, 2004 10:36 PM
how come the lithium cut off points are different on different speed controls? nugulator Power Systems 7 Dec 11, 2003 11:10 AM
How come there are no wooden props in E-flight? FX1SUB Power Systems 10 Aug 04, 2003 01:59 PM
How to secure servos in Terry w/out epoxy? DennisG Foamies (Kits) 1 Sep 01, 2002 03:25 PM
Rave How to get the most out of your IT Department al_b Humor 0 May 16, 2002 04:56 AM