tappered wing and the sandwich method for shaping ribs
 

Ok i have a slight problem. I am making some wing ribs for a small aerobat called chilli breeze. The plan was with a magazine back in 1994. I understand the sandwich method for shaping ribs if the plan gives you a root and tip shape. the problem is that the wing is heavily tappered. it has a straight trailing edge but heavy tapper in the leading edge . when i form the ribs i am left with a bevel on the front edge. In my opinion i can not use those ribs. i thought of putting some spacers between the ribs when i form the sandwich so the bevel is less. how do you guys eliminate this problem?

RE: tappered wing and the sandwich method for shaping ribs
 

If there are not many ribs to cut, to reduce the bevel, I do both sets together and split them in 2 by taking every second rib etc . As I normally notch LE and TE to inset the ribs to give a better glued joint, I cut these to suit bevel. The purists will point out that I will have one wing slightly smaller than the other but as I am not a stickler for accuracy and where the difference is small -this can be taken out by the notching - who cares ??

for large tapers with small no of ribs - your adding extra spacer ribs is the solution unless you want to draft all the ribs and cut individually.

john

RE: tappered wing and the sandwich method for shaping ribs
 

I have built 1/5 scale wings with tapers from 17.75" at the root to 4.75" (see my avatar) and never tappered the ribs. Like John 38 I perfer to slot the Leading edge material to improve the glueing surface area. I then attach the rough cut leading edge material and then after everthing is dry shape it with a 44" sanding bar and several grits of sandpaper. I use rubber cement to glue a paper template to the stock and then rough cut the ribs by hand in pairs and sand them to the final shape. Sometimes I will choose to make two sets and I will cut all four ribs at the sametime using the same method. I can have two full sets in less than 8 hours.

RE: tappered wing and the sandwich method for shaping ribs
 

Rather than sandwich all the ribs between the templates, place the blank for the root rib outside the root template. Carve and sand. This makes all the ribs too large by the amount of the taper. Now make the second set of ribs, but make the stack as a mirror image. Now take each of your #1 ribs and put them together. Sand off the taper. You now have the exact pattern desired.
Chuck

RE: tappered wing and the sandwich method for shaping ribs
 

The rib stack does not need to mimic the taper of the wing. It's quite OK to stack the blanks and place the end templates so that the leading and trailing edges have the same slope.

For wings with radical taper I like to stack twice as many blanks to reduce the slope of the final "block". Once done I remove every other finished rib. I then replace the ribs I took out with the second set of blanks leaving the formed "spacers" as before. Once the second set is done I've got two sets of identical ribs. The rib like spacers I set aside for any future repairs if needed. If I need to use one I can sand it down to slightly reduce the size at the time.

If the leading edge or trailing edge is still too angled to get a good glue joint simply square or re-angle the with a sanding block as you place them.

I only ever had to do it this way one time. But it worked out well for that project. The rest of the time the designs I've done were fine with the ribs stacked without any spacers.

RE: tappered wing and the sandwich method for shaping ribs
 

thanks for the repplies people! thanks a lot.

RE: tappered wing and the sandwich method for shaping ribs
 

Put blue foam between the balsa blanks. It makes the ribs 'fair' into each other better. When done, use the balsa ribs as patterns to make the ones you will use for the wing. You can even make elliptical wings using this method. I have patterns made for a 1/4 Gordon Israel 'Redhead' that I'll build sometime next year. It has an inverted 'gull' and elliptical wing planform. I currently have a nice photo tutorial on RCAerotowing website under scale sailplanes builds forum which will get even more info on the pattern making, spar notch placement and etc. It is the 1932 BS2 'Balestruccio', an elegant Italain sailplane.

RE: tappered wing and the sandwich method for shaping ribs
 

ARUP, may we have a link please?

RE: tappered wing and the sandwich method for shaping ribs
 

I'm very ignorant of computers and attaching links and such. RCAerotowing.com is the site. Click 'forums' and then 'scale sailplane' build thread. The thread is entitled [1/6 Scale 1932 BS2 'Balestruccio']. I have a similar thread on RCScalebuilder and RCGroups.

RE: tappered wing and the sandwich method for shaping ribs
 

Thanks ARUP I will make a point to check it out.

RE: tappered wing and the sandwich method for shaping ribs
 

Here is a link to ARUP's build, he off to a good start.

http://www.rcaerotowing.com/forum/sh...2-Balestruccio