Logo
Builders' Plan Gallery  |  Hip Pocket Web Site  |  Contact Forum Admin  |  Contact Global Moderator
December 18, 2017, 05:18:17 PM *
Welcome, Guest. Please login or register.
Did you miss your activation email?

Login with email, password and session length
 
Home Help Search Login Register
Pages: [1]   Go Down
Print
Author Topic: building wings with taper ribs  (Read 1356 times)
0 Members and 1 Guest are viewing this topic.
trev188
Nickel Member
*

Kudos: 0
Offline Offline

United Kingdom United Kingdom

Posts: 2

Topic starter


Ignore
« on: October 28, 2013, 11:47:00 AM »

    >:(Hi every body. I am really struggling with the rib set for an APS U2 by warburton. There is only the tip and root ribs on the plan and I hate this nonsense making two templates and stack sanding to get the rib shape. surely there is a better way than this.
cheers all trev   
Logged
Starduster
Platinum Member
******

Kudos: 29
Offline Offline

United States United States

Posts: 1,199




Ignore
« Reply #1 on: October 28, 2013, 12:59:55 PM »

One possible solution:

1) Scan the root airfoil into your computer.

2) Measure the chord of the root rib

3) Measure the chord of the next rib outboard of the root (from the plans)

4) Divide the chord of the second rib by the chord of the root rib. This is the scale factor.

5) Open the scanned image of the root rib and select Print

6) Change the Scale of the print from 100% (Might say "Full Size") to the scale factor. You may have to look through the printer properties page in order to find the Scale button).

7) If the wing is a simple single or double taper, just change the scale for as many ribs as there are on the plan.

For example: Let's say the root rib has a Chord of 5 inches. The first rib outboard has a chord of 4.5 inches. 4.5 / 5 = .9. I change my Scale to .9 and print. The easiest thing to do then is to simply change the Scale by 10% for each rib. So, If I had a total of 5 ribs, first (root) rib = 100%, 2nd rib = 90%, 3rd rib = 80% and so on...

At least that's the way I'd do it (and have done it, BTW)

Logged

"We have done the impossible, and that makes us mighty..."
Elmas
Nickel Member
*

Kudos: 0
Offline Offline

Italy Italy

Posts: 1



Ignore
« Reply #2 on: December 03, 2013, 04:59:47 AM »

With programs like these is very easy.

http://web.mit.edu/drela/Public/web/xfoil/

http://www.rc-soar.com/hardsoft/profilerev.htm

http://www.profili2.com/eng/

But generally I use the two ribs method......
Logged
greggles47
Gold Member
*****

Kudos: 11
Offline Offline

Australia Australia

Posts: 270




Ignore
« Reply #3 on: December 03, 2013, 05:51:22 AM »

    >:(Hi every body. I am really struggling with the rib set for an APS U2 by warburton. There is only the tip and root ribs on the plan and I hate this nonsense making two templates and stack sanding to get the rib shape. surely there is a better way than this.
cheers all trev   

Trev,

What is the problem with doing the ribs in this way?

I've never built a tapered wing, but all the aerobatics fliers I know build this way, and have been doing so for many years with no issues.

The tips they have passed on is not to include the centre ribs in this method, and once sanded to shape dismantle the set and sand each rib so that it doesn't have the angled surface.

Greg
Logged

There must be some way out of here, said the joker to the thief,
There's too much confusion, I can't get no relief
algy
Silver Member
****

Kudos: 6
Offline Offline

Australia Australia

Posts: 193



Ignore
« Reply #4 on: December 03, 2013, 06:06:26 AM »

Trev,

I have built my tapered wings just using the tip and root ribs as templates with blanks in between. Works great. It's how I build strait wings as well.

Never seen it as any problem and actually a time saver since you only need to actually cut out two template ribs.  After sanding all to shape I cut any spar slots etc,etc, take out the pins and off you go.


Cheers

Algy 
Logged
OZPAF
Titanium Member
*******

Kudos: 39
Online Online

Australia Australia

Posts: 3,601



Ignore
« Reply #5 on: December 03, 2013, 05:27:37 PM »

Using the root and tip ribs as templates to sand the blanks, as advised by Algy, works well. I would also advise using a strip of masking tape on the long sading block where it runs over the ribs.Glue the rib blanks in position and sand gently in a chordwise direction.
Try to keep the sanding block on an imaginary line connecting the same chordwise points on the root and tip templates to maintain an even profile change from root to tip.
Its not hard but needs to be done carefully.
The scaling approach is more accurate if both airfoils are the same - if not then one of the programmes mentioned will be required.
Providing the taper is not too severe then the sandwich system is stiil ok and the the bevelled edges on the ribs can be removed by sanding carefully with a long block after gluing up the wing. I prefer to use the inside of the bevelled edge as the rib outlie when using this method which requires the first rib to be replaced as mentioned by Greg(greggles47).
John
Logged
TimWescott
Gold Member
*****

Kudos: 12
Offline Offline

United States United States

Posts: 864



Ignore
« Reply #6 on: December 03, 2013, 09:12:45 PM »

Hey Trev:

For scratch-building, I too like the stack-cut method.  I think it's about the most accurate way to hand-cut ribs for a tapered wing.  The only place where my advice differs from other people's is that if the wing construction is good for it (i.e., no spars or whatnot in the way), I prefer to put the wing together with the ribs as they come out of the stack, then sand them to match with a long sanding board.  If the wing has capstrips or sheeting you need to do this before such stuff goes on.

If you just can't bear the thought of stack cutting, I suggest looking around for a laser-cut rib set.
Logged
Mike Rolls
Bronze Member
***

Kudos: 0
Offline Offline

United Kingdom United Kingdom

Posts: 18



Ignore
« Reply #7 on: August 18, 2017, 09:52:49 AM »

The Profili programme is very good - I've used it for a number of tapered wings over the years. One thing to bear in mind over the 'stack' - you'll also see it referred to as 'sandwich' - method is the it's OK if the taper isn't very great and there a fair number of ribs, but in fact the system if used without modification, will always give a root rib that is slightly too small and a tip rib that is slightly too big.
Mike
Logged
F4FGuy
Bronze Member
***

Kudos: 4
Offline Offline

United States United States

Posts: 43



Ignore
« Reply #8 on: December 02, 2017, 06:11:01 PM »

Trev,

  All the methods noted above will work. But my favorite is Bob Hunt's "lost foam" method.It's fast, accurate, and can generate ribs at any location or angle.The only hard part is that you have to have access to a foam wing cutter, which, if you don't have one, is easy to build.   Generally, you cut a foam wing to generate the overall shape, mark the shucks where you  want ribs, and cut the foam core with a hot wire at the desired locations. Use the core pieces as templates for the ribs. A molded  LE, and TE spar complete the basic structure, which can subsequently be fully sheeted or capstripped.

The photos should give a  fair idea of the process. The wing was for my 1/2A "Lil' Zero. Note also the molded wing tips.

Ron Burn (F4FGuy)
Attached files Thumbnail(s):
Re: building wings with taper ribs
Re: building wings with taper ribs
Re: building wings with taper ribs
Re: building wings with taper ribs
Re: building wings with taper ribs
Re: building wings with taper ribs
Logged
Big G
Bronze Member
***

Kudos: 1
Offline Offline

United Kingdom United Kingdom

Posts: 81



Ignore
« Reply #9 on: December 03, 2017, 09:17:57 AM »

Trev, the Yatsenkos use the 'sandwich' method to make ribs, and if it's OK for them it should be OK for anyone! Take a look at their fascinating article on wing construction: http://discovery-aeromodels.com/en/assemblage-wing-of-classical-construction.html

G

Logged
F4FGuy
Bronze Member
***

Kudos: 4
Offline Offline

United States United States

Posts: 43



Ignore
« Reply #10 on: December 04, 2017, 06:16:37 PM »

 
Big G,
  Most fascinating is the fixturing. Once the basic structure is made, you can sand all ribs to perfect alignment. The one problem I see is the inability to do a geodetic structure which has much more structural stiffness in both beam and torsion,and can be built lighter.

 Ron Burn (F4FGuy)
Logged
Big G
Bronze Member
***

Kudos: 1
Offline Offline

United Kingdom United Kingdom

Posts: 81



Ignore
« Reply #11 on: December 05, 2017, 05:29:04 AM »

Rob, I really fly stunters just for fun, so I ain't no expert. I can't recall seeing a stunt model in recent years having geodetic wings, but obviously some have been built this way, I'm sure. FF models still use geodetic wings in many cases, but these are still mostly built flat on the board. The full-depth spar and D-box construction of many stunt model wings would appear to be stiff enough without the use of geodetic ribs. A matter of personsal preference, maybe.The Yatsenko jig method really is simplicity itself. What I do have are lengths of aluminium angle with various grades of sandpaper bonded to the outside surfaces, for getting everything nice and flat once the glue has set. Not rocket science.

G
Logged
F4FGuy
Bronze Member
***

Kudos: 4
Offline Offline

United States United States

Posts: 43



Ignore
« Reply #12 on: December 06, 2017, 01:08:43 AM »

 
Big,

 I think you mistook my intent. I agree, the concept of the jig is great and simple.

The jig doesn't care how the ribs are generated, sandwich method, plotted individually, or lost core.

As to the geodetic structure, sure, it's a matter of choice. However, it can produce a lighter, stronger,  more warp resistant wing.

Ron Burn (F4FGuy)
Logged
OZPAF
Titanium Member
*******

Kudos: 39
Online Online

Australia Australia

Posts: 3,601



Ignore
« Reply #13 on: December 07, 2017, 05:10:08 PM »

If a jig is used and it can be rotated to work on both sides of the wing then rectangular blanks can be placed in the jig with accurate rib templates at each end. A trammel sander similar to what Big has mentioned can then be used to sand the intermediate ribs to size.
The end ribs can be cut directly off the templates.
This method gives the correct bevel at the edge of each rib and is most beneficial when the taper is severe.
I have used this system and it works well but does need a bit of attention to keep the trammel sanding bar on the corresponding points on the root and tip templates.
For a moderate taper the sandwich system works well, and direct plotting is always an alternative using the methods mentioned.
Happy building.
John
Logged
F4FGuy
Bronze Member
***

Kudos: 4
Offline Offline

United States United States

Posts: 43



Ignore
« Reply #14 on: December 08, 2017, 12:26:11 AM »

John,

 Again I must point out, I think the jig as a concept is great. Once things are in place in the jig whether rectilinear or geodetic, a sanding bar can be used to true the rib surfaces. The jig has nothing to do with the design of the structure.

 As far as the method used to develop the rib shapes, the most accurate is to plot them. this is a straightforward procedure for any competent draftsman. If pencil, paper and triangles are not your thing, there are numerous computer programs out there that do a much better job than the sandwich method. Really, however, it makes little difference. Accuracy is in the eye of the beholder. A careful builder can make a well aligned, accurate wing using any workable system. A sloppy builder can screw up regardless of how good the system might be.

  Ron Burn (F4FGuy)
Logged
Big G
Bronze Member
***

Kudos: 1
Offline Offline

United Kingdom United Kingdom

Posts: 81



Ignore
« Reply #15 on: December 08, 2017, 05:08:33 AM »

Going off the subject of stunt wings for a moment, years ago many FF models had geodetic wing structure, covered usually with doped tissue. They were considered reasonably stiff, but as engine power, towline technique and rubber quality improved, geodetic wings were found to be too flexible during the power or release from the towline stage of the flight, and were still prone to warps. So wings based on strong spars plus a sheet balsa D-box were next, these being much stiffer than a simple open structure. Most D-box wings used straight ribs. Things moved on rapidly via metal-covered D-boxes, kevlar and carbon D-boxes, carbon spars and TE, etc., etc. I think these days most F1C wings are made from foam covered in carbon cloth (I may be a bit behind the times here). The resistance to twisting of any wing (which is what we're aiming for) is rooted in the spars and in the structure in front of the spars. The TE supplies very little torsional strength to a wing. My old F1B wings have either metal-covered balsa or carbon D-boxes, carbon spars, straight ribs with carbon capping, carbon TE (the latter being only approx. 2.5mm x 0.8mm IIRC) and are stiff. Even after more than 10 years storage they are as built, no shifting at all. All I'm saying is that if the rest of the wing is correctly designed and built it doesn't really matter if the ribs are straight or geodetic.

G
Logged
Pages: [1]   Go Up
Print
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.21 | SMF © 2015, Simple Machines Valid XHTML 1.0! Valid CSS!