Bladder Buster tanks from Reed Mfg

[Doug]

Zip archive here:

https://www.dropbox.com/sh/5w86t9dob...L07adz1Sa?dl=0

[rvbuilder2002]

Originally Posted by cccjbr6

I would think and extra 18 inches of wing span would increase useful load somewhat.

If you are assuming that the gross weight is based on meeting a minimum climb rate (like in FAR23) that would be true, but RV's have never had any problems meeting the common minimum performance requirements.

Originally Posted by Bubblehead

Be careful here. Extending the wings increases bending moment at the root, and increasing load will do the same (plus increasing shear load).

This would be the main reason to be careful.
If you increase the span you would automatically increase the bending moment slightly (longer lever arm), even if you used the same max. gross weight value.
If you increase the span and increase gross weight, the bending moment on the wing goes up even more.

[GrayHawk]

Originally Posted by Bubblehead

The link is not working for me. Any suggestions?

Sorry for the link not working. We were forced to change upstream isp and naturally IPs, znd chose to do it today (Sunday).

Everything should be back to normal tomorrow after new DNS ripples out.

GH

[cantrma]

Pardon me opening an old thread, I'd like to build similar tanks. But I don't believe that adding weight on the end of the wing increases the bending moment at the wing root. In fact I believe, if it doesn't by its shape generate enough lift to make no difference, it will create a negative moment (relative to the moment at the wing root) in the last few inches or foot of the wingtip.

When not flying, there will be more negative (relative to flying upright) moment at the wing root but this is minor compared to the negative G rating or load under inverted or turbulence load (both of which I think are minor due to the location of and the shape of the tip tank).

I do understand that the moment around the Z axis at the wing root will be increased due to the drag of the wingtip tank, but I don't believe this is what was being referred to. Although I also have no idea how to analyze this relative to the strength of the front spar/back spar attachments.

I have a civil engineering degree but 40 years in IT has corroded any real knowledge I may have had. How should I visualize the impact of the tip tank on wing loading?

Thanks,
Mark Cantrell

[rvbuilder2002]

Originally Posted by cantrma

But I don't believe that adding weight on the end of the wing increases the bending moment at the wing root. In fact I believe, if it doesn't by its shape generate enough lift to make no difference, it will create a negative moment (relative to the moment at the wing root) in the last few inches or foot of the wingtip.

I think the discussion was about an extension of the wing that did match the airfoil shape of the wing so it would produced lift. That additional lift is further outboard so it would increase the bending moment on the wing.
During times when the tank contains fuel, its mass would reduce the bending moment, but it would be higher when the tank is empty.