How many ribs do I need in a 60 inch wing?  
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All Forums >> RC Airplanes >> Scratch Building, Aircraft Design, 3D/CAD >> How many ribs do I need in a 60 inch wing?
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How many ribs do I need in a 60 inch wing? - 3/24/2002 12:15:55 PM   
Someone11-RCU



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From: Fresno, CA, USA
Status: offline 		How many wing ribs are best for a 60 inch wing? How long do you think they should be for a 40 sized plane?

Thanks-Brian

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How many ribs do I need in a 60 inch wing? - 3/24/2002 12:27:44 PM   
RC_Eflyer-RCU



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Status: offline 		Unfortunatly this is a pretty broad questions, well the answers could be. A little bit of info about what type of plane it will be is going to be needed. Fill us in on all the details, then I'll get back to you.

--Paul

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How many ribs do I need in a 60 inch wing? - 3/24/2002 12:46:38 PM   
Someone11-RCU



Posts: 394
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From: Fresno, CA, USA
Status: offline 		Right now it is only drawn at half the actual size. This is my first time designing an airplane. I only have a trainer The Fuse is about 50 in and wings are 60 in. Here is a picture of what it looks like..... (A Screenshot)



I need lots of work on it.... especially the airfoil. Its a never ending project

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How many ribs do I need in a 60 inch wing? - 3/24/2002 12:48:12 PM   
Someone11-RCU



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Status: offline 		I'm in a drafting class at high school, where we learned autocad, but most of the stuff i learned was trial and error

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rib spacing - 3/24/2002 1:31:06 PM   
majortom-RCU


 

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Status: offline 		My rule of thumb is rib bays at least 3" wide, no more than 4". For 10-12" chord I would use 1/8" thick ribs and stay closer to 3". With a 60" wing, assuming a one-piece wing, that would be 20 rib bays, ten per side. Depending on what else you need in the wing (landing gear, retracts, aileron servos, etc.) you can maybe go 9 per side if things fit better that way. Some designs work better with an open bay centered in the wingspan to accommodate one wing servo, fuselage fastening structure, etc.

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Rib Spacing - 3/24/2002 3:29:07 PM   
Ollie


 

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Status: offline 		There are two considerations to rib spacing. They are covering sag and strength. How much covering sag depends on the curvature of the area being covered and the spacing between the ribs. The wider the spacing and the more the curvature the more the sag. If there is no leading edge sheeting then the ribs must be very closely spaced to prevent excessive sag and to preserve the airfoil. The area behind the spar isn't so highly curved and greater rib spacing can be tolerated. The Ribs must be spaced close enough so that the trailing edge isn't distorted by the tension of the covering. So the rib spacing also depends on the stiffness of the trailing edge.

If the leading edge isn't sheeted, then a one inch rib spacing for a 10 or 12 inch average chord is in order. If the leading edge is sheeted and the trailing edge or aileron support spar is at least 1/4 inch stock, then a 3 inch rib spacing can usually be tolerated behind the spar.

< Message edited by Ollie -- Mar 24 2002 10:46AM >

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Thanks for your help! - 3/24/2002 9:34:05 PM   
Someone11-RCU



Posts: 394
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From: Fresno, CA, USA
Status: offline 		Ok, then I'll go with leading edge sheeting, 1/4in. stock in the trailing edge, and 3in. spaced wing ribs. How far should the leading edge sheeting go up on the wing? My rib has a 13in. length.

Is there any thing else I need to know about desiging/scratch building a plane?

THANKS THANKS THANKS- brian

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scratch design - 3/24/2002 11:58:27 PM   
majortom-RCU


 

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Status: offline 		Brian, your design project looks pretty ambitious for a first attempt/high school project, but that's OK as long as you understand that even experienced experts find that their first version of a new design has many problems that need to be worked out before the model is capable of stable flight. There are only a few thousand other things you need to know about scratch design, but one good way to learn them is to get started with something and then address the problems as they come up. If I had your ambition when I was in high school I'd probably be a rocket designer by now.

If you were a hangar rat in my shop, I think I'd get you to buy yourself a popular model kit (not an ARF) and build it (and fly it) as the perfect structured learning exercise for the first thousand things you need to know about scratch building. Study the plans, study the instruction book, think, build, learn. Every time you learn something new in your building project, put it in your scratch design notebook. Keep lots of notes, work out lots of trial solutions with your CAD software. Get an afterschool job (or a rich father) so you can buy lots of tools. I can tell you are a guy who will need lots of tools. Get the Tower catalog, learn your way around the Tower website, and you'll be plane crazy in no time.

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Design Philosophy - 3/25/2002 1:29:42 AM   
Ollie


 

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Status: offline 		Don't be discouraged when you run into a problem. The essence of design is problem solving. Often this is the resolution of a conflict in objectives like low weight versus high strength. The consequences of a mistake are limited to one design if it leads to knowledge of how to avoid it in the future. The consequences of solving a problem stay with you for the rest of your life.

A 3 or 4 inch wide sheet at the leading edge will allow 3 inch rib spacing. The sheeting should be connected between the top and bottom at the aft edge by shearwebs between the ribs. This will give the wing great torsional rigidity and prevent warps from developing after construction.

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How many ribs do I need in a 60 inch wing? - 3/25/2002 4:16:57 AM   
Someone11-RCU



Posts: 394
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Status: offline 		A problem that I learned is that it is hard trying to help people with this kind of stuff just by typing. It would be a lot easier if someone close to where I lived could show me. I know that there are a lot of guys in Fresno that can help me with this stuff, but I don't have a car yet, and I need to get a job to buy my 2nd airplane for the summer.


My Trainer: I had a Tower Trainer 40. At the airfield on the 6th flight all of a sudden the plane went dead. I was connected by buddy box to our club's flight insturctor. My transmitter battery ran out of juice, and down comes the plane. I had lots of altitude so I could recover from a mess up, but in this case altitude wasn't my friend. It went straight down, it seemed like forever..... once I got to the crash nothing was left. The servo cases were broken, balsa bits everywhere, and luckily I found the engine under what was left of my wing. I didn't get mad, I just felt sick. It was really my first day of continuous flights too. Luckily since I was flying with my club's designated pilot trainer he helped me out. Since I bought a Tower Trainer, and they guarantee flying success with a certified AMA club instructor. It was still inder warranty, so I was very lucky. I sent it Friday form California so it will take a while to come back, but we'll see what they do.

I don't know why, but I wanted to tell the story. Sorry moderators if this is off-topic, but I was in the mood to type

Thanks to everyone for the help and knowledge!

-Brian

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How many ribs do I need in a 60 inch wing? - 3/25/2002 6:18:24 AM   
majortom-RCU


 

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Status: offline 		Brian, we've all been there. This is what makes it a sport! Browse the crash forum for commiseration.

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ribs - 4/2/2002 11:03:31 AM   
TGoodwin



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From: LAS VEGAS, NV, USA
Status: offline 		TWO. One at the root. One at the tip and a foam core in between.

Ted

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ribs - 4/2/2002 12:41:37 PM   
ProfLooney



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Status: offline 		I usually space my ribs abt 2 to 2 1/2 inches apart or would say abt 10 ribs to a side

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Re: ribs - 4/3/2002 8:11:26 AM   
Someone11-RCU



Posts: 394
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From: Fresno, CA, USA
Status: offline 		[QUOTE]Originally posted by TGoodwin
TWO. One at the root. One at the tip and a foam core in between.

Ted [/QUOTE]

Foam Core? I haven't heard much about this, but I do know it will make it very light! How would I go about doing this? I never considered this for my plane..... are there any drawbacks when using a foam wing core?

Thanks! - Brian

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How many ribs do I need in a 60 inch wing? - 4/3/2002 8:22:02 AM   
majortom-RCU


 

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Status: offline 		Brian, you just opened a can of worms. But, maybe you're a robin! Check out http://www.rcfaq.com/answers/modelbuilding/foamcutting.htm.

Built up balsa is the way all models used to be built, and many still are, and many still consider it the best way. The other way is foam core, which has its adherents, and most experienced modelers will do it both ways. It's good to learn both, but learn one before you tackle the other. You can build a balsa wing with simple tools. You can build a kit that supplies foam cores ready-cut and sometimes ready sheeted. Cutting your own foam, which is where this method leads, gets to be a bit more involved.

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How many ribs do I need in a 60 inch wing? - 4/3/2002 8:42:20 AM