Flipping fuel tank baffles around.

[Gregg Brightwell]

Ok guys, I am posting this here, because I am guessing that the 3/4/6, (if not the 7/8/9 also) are all similar. My -4 wing kit is an older kit. Well the spars are older, but most of the other parts are new. The forward facing flanges on the spar web USED to be the same height as the tank baffle. (Tank baffle faced forward as well) On the newer spars, the forward facing flanges are about 1/32" shorter than the tank baffle to allow the baffle flanges to go OVER the spar web flanges, and then the tank skin goes over the baffle flanges. (Total of three layers, hope I am painting a clear enough picture here) Tank baffle faces aft.

Since I have older spars, and new tank parts, the baffle and spar web flanges are exactly the same height. (Cannot slide baffle over spar web or it causes a bulge)

So, here are my options as I see them:

1- Flip the tank baffle over flanges forward, and notch the ribs to accommodate the baffle flanges.
2- Leave the baffle flanges facing aft per plans, and cut off .5" of the flange to make the baffle flanges.5". This will butt up the baffle and spar web flanges.

I have called Vans, and they said either option is fine, and that there are MANY older rv-4s out there with forward facing baffles. To slightly make it more challenging, the new skins are pre-punched, which permits nearly zero margin for error with respect to edge distance. I am leaning very strongly to option 2, but I would like to see if anyone else has experienced this issue. Thankfully, very little else has changed with the rv-4 wing in the last 20 years.

I hope I have described this well enough. Anyone have another idea, solution other than what I have come up with?

Thanks

Gregg

[DaAV8R]

I'm not the right person to answer this but since Gregg and I are acquainted, I'll take a stab. Maybe someone experienced with the -4 will jump in.

I'm not sure if this is helpful but here is a snapshot of the -8 attachment. As you can see it is very different from what you describe. The main spar flanges face rearward. While the only portion of the tank that swallows the spar is the tank skin, the baffle is also attached to the main spar via the Z brackets. The Z brackets are in alignment with the nose ribs.

It sounds like the design change in the -4 tank attachment also provided for a connection between the baffle and the main spar.

If you are certain the early designs didn't utilize a connection between the baffle and the main spar and Van's isn't concerned about this connection I probably wouldn't be either. Otherwise you will need to devise your own connection since your spar is too tall to accept the baffle.

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[Gregg Brightwell]

Thank you Robert!

Well, I had forgotten about the Z brackets on the later models. I stood at the wing for a bit today, with new AND old plans, and am confident that I have a plan.

I am shortening the flanges, and facing them aft. This will kind of be a hybrid installation between new and old.

Thanks!

Gregg