False ribs for stiffening wing skins?

[Marty_d]

Hi,

 

 

I've cleco'd the top rear skin on the right wing and turned it over to do the bottom skin. However before it all gets put together I thought I should add false ribs (curved L angle) between ribs to get rid of oil canning in the wings.

 

 

How have people done this? Did you run the L angle all the way to the front and rear spars, or have a gap between them and just rivet to the skin? Or instead of running curved L from front to rear, did you run straight L span-wise between the ribs?

 

 

Interested in all discussion on this.

 

 

Thanks, Marty

 

 

[Guest Nobody]

What do the plans show?

 

Adding extra material might increase strength but might also just result in extra unnesecary weight....

 

 

[AllanBendigo]

Hi,

I've cleco'd the top rear skin on the right wing and turned it over to do the bottom skin. However before it all gets put together I thought I should add false ribs (curved L angle) between ribs to get rid of oil canning in the wings.

 

 

How have people done this? Did you run the L angle all the way to the front and rear spars, or have a gap between them and just rivet to the skin? Or instead of running curved L from front to rear, did you run straight L span-wise between the ribs?

 

 

Interested in all discussion on this.

 

 

Thanks, Marty

Hi Marty

The 750 and 650 now have L angles between the ribs side to side (parallel to the spar)

 

Cheers

 

Allan

 

 

[djpacro]

Perhaps it is worth asking the manufacturer this question?

 

 

[cherk]

Perhaps it is worth asking the manufacturer this question?

That's how 'they' do it ............on the plans anyway!

 

 

[Marty_d]

That's how 'they' do it ............on the plans anyway!

Don't know about that - my plans have no false ribs shown at all, but I believe from anecdotal experience that many people add false ribs because of the large spans of unsupported 0.016" skin between the ribs (600mm). Apparently if you don't add them you get the banging noises as the skins "oil-can".

 

Hi MartyThe 750 and 650 now have L angles between the ribs side to side (parallel to the spar)

Cheers

 

Allan

Thanks Allan. Are they riveted to the rib flange as well, or just to the skin between them?

 

Thanks all, Marty

 

 

[djpacro]

So, if your plans don't have them I suggest that you ask the manufacturer - perhaps they will send the current drawing.

 

 

[rankamateur]

The stringers between the ribs only need to be L shaped across the span, the ends have the angle cut away to a flat where they go between the skin and the rib, the rivet goes through skin, stringer, then the rib, and they come in the kit, in Savannah Land anyway. Steve H...

 

 

[terryc]

Hi Marty, there is a variation signed by chis heinz showing the details. I'll see if I can find it. I think I saw it on the matronics website.

 

Terry

 

 

[bexrbetter]

Glue some stiff foam ribs across the drumming areas??

 

 

[Marty_d]

Thanks Terry, that'd be fantastic.

 

I don't mind going out on a limb sometimes and putting in my own mod (after a LOT of thought), but always much happier if it's signed off by the designer. (Or his son).

 

 

[Marty_d]

Glue some stiff foam ribs across the drumming areas??

That's another option, and certainly one I'm considering for the fuselage. However it seems easier just to use L (or Z) angles riveted to the skin rather than worrying about what type of glue to use, whether it'll eventually work loose due to vibration, etc etc.

 

 

[Kyle Communications]

The savannah has wing skin tensioners I have some photos I will find and post them for you

 

 

[AllanBendigo]

Marty

 

The L angles between the ribs do not attach to the ribs they are about 4 mm short

 

I will take a pic of the plans and email them to you

 

Cheers

 

Allan

 

 

[Marty_d]

MartyThe L angles between the ribs do not attach to the ribs they are about 4 mm short

I will take a pic of the plans and email them to you

 

Cheers

 

Allan

Thanks Allan, got that email. Thanks everyone for your advice!

 

Cheers, Marty

 

 

[Thruster87]

This is what I ended up doing .Cheers

 

 

 

[Kyle Communications]

You can see the right angle skin tensioners in the tip of the wing they are in 2 places in the top and bottom skins behind the main spar and full length of the wing skins except where the fuel tanks are of course to stop the oil canning. I also made up flat strips and sikaflexed them to the skin above both fuel tanks in each wing to also stop this they are not right angles but are locked between the skin and rib as the others are.

 

 

 

 

 

 

[Kevin McCune]

Kyle, that is the first time that I've seen them going in that direction, The one I've seen are 90 degrees to yours, parallel to the ribs. They are pretty common on 701s and CH just calls them stiffeners. But I have no idea what is allowed in your country as they are not in my plans. There are pics on the US Zenith site and I believe some in the old Zenair news as well. Almost forgot, the reason I replied, lengthways on the wing like yours is much easier to fabricate, I like it.

 

Kevin

 

You can see the right angle skin tensioners in the tip of the wing they are in 2 places in the top and bottom skins behind the main spar and full length of the wing skins except where the fuel tanks are of course to stop the oil canning. I also made up flat strips and sikaflexed them to the skin above both fuel tanks in each wing to also stop this they are not right angles but are locked between the skin and rib as the others are.

[AllanBendigo]

Hi Kevin

 

You to can do the same, the 650 and 750 now have L angles running parallel to the spar on the top and bottom wing skins.

 

Cheers

 

 

[Kyle Communications]

Kyle, that is the first time that I've seen them going in that direction, The one I've seen are 90 degrees to yours, parallel to the ribs. They are pretty common on 701s and CH just calls them stiffeners. But I have no idea what is allowed in your country as they are not in my plans. There are pics on the US Zenith site and I believe some in the old Zenair news as well. Almost forgot, the reason I replied, lengthways on the wing like yours is much easier to fabricate, I like it.Kevin

Hi Kevin

The wing skin tensioners are just that they give some hold to the wing skins top and bottom. They are basically no weight at all but provide a lot of torsional strength to the wing skins as they are riveted to the skins top and bottom. The ones I made for the top skins on my Savannah do not have the right angle bend as of course they won't fit between the wing skin and the top of the tank. I didn't rivet them either I sikaflexed them to the skin but they still lock under the rivet that goes into the top of the rib edge. This just helps the wing ribs remain where they are supposed to be. The outside panel on the top and the bottom outer section of the tailplane did not have any tensioners in one section either side out towards the tips on the tailplane. So I used right angles left over from the wing to do exactly the same and this made the tailplane so much stronger before you could press the skins in easily now you can not.