Horizontal Stab.-905 nose rib question???

[agirard7a]

Problem? Horizontal Stab.-905 nose rib question???

I am putting together the Horizontal Stab. I riveted the center 905 nose rib and discovered a potential problem, although not sure. There seems to be a very flat area in the center of the skin at the center rib. However, the profile matches the wood profile templates. I researched this problem and others thought shims where needed between the skin and the rib. The outboard and inboard forward ribs also riveted in also match the wood profile supplied by vans. The problem: the skin between the ribs bulges out in a wider profile. Thus giving the appearance of the flat profile at the center rib. A friend suggested that the skin taken out of the box needs to be bent more, thus hopefully eliminating the bulge between the ribs. I'm sure Vans designed a standard NACA profile and created the ribs to match this profile.

Have any of you guys experienced this problem? What is the fix? Does the skin need to be bent more? Appreciate some input.

Thanks, Al

 

[aarvig]

Normal...

Al,
Search the forums and you will find this to be a common problem. The ribs just aren't formed perfect enough and as a result you get a flat spot at the center rib when it is riveted down. It is not the prettiest thing but it is normal. Before fabricating and installing a shim I would talk to Vans about it. Frankly, I just adjusted the bend on the rib flange a little to make sure it contacted the skin better. It isn't perfect but it looks fine and will fly fine. You will find the more perfect you try to make something the higher likelihood will be that you will damage something or be forced to replace it until it is perfect. If you are building a show plane then by all means go ahead. Otherwise, it is normal, airworthy and strong...build on my friend.

Here is a picture of the inside of my HS and center nose rib. You can see the airspace between the rib and the skin. Shaped the flange a bit to make it fit and it looks fine. Also, make sure you are using the fluting tool on the nose portion of the rib so that it pulls the flanges in a bit. This helps to shape the rib even better. You can see the flute I placed in the following pic as well.

 

[Av8torTom]

Mine turned out OK

Hey Al,

I had the same problem - I didn't do anything about it, and it's not too noticeable. I don't see an issue putting in a shim if you want - but a check with VANs is always a good idea.

Keep on building,

T.