Problems with HS skin and ribs

[hugo]

Hello fellow builders,

After assembling the horizontal stabilizer with cleco's, I noticed that the skin was not completely flat against the flanges of the nose-ribs. You could see that the clecos pulled the skin to the ribs. I suspect that this situation makes it very hard to rivet the skin to the nose-ribs.
I disassembled the complete HS, with only the front spar and nose ribs attached. If I remove the clecos from the nose-ribs, you can see in the picture that the skin is not flat against the flange of the ribs ( even with all the clecos of the front spar installed ). The force that is needed to push the skin to the flange is quite substantial.



I tried to bend the skin a little more ( very carefully ! ), but this was almost impossible.

Somebody out here with the same problems ?

regards

hugo

[Spike]

No sweat Hugo! By the way, welcome to the group!!

First, take it all apart. Then what you need to do is to flute the front of the nose ribs between the upper and lower flanges such that you can cleco the forward most holes on the nose ribs. Then you cleco those ribs in front to back. After that is done, then you cleco in the main spar, then the ribs (still working front to back) then the rear spar. Note that to get the initial nose rib in there its much easier to have another person help you. I had my dad cup the skin in his hands and squeeze them together while I set the clecos in the middle nose rib. After that it goes much easier. Just make sure you work front to back when fitting that assembly up.

-- John

[arffguy]

Exactly what Spike said. I just saw it for myself last week. The fluting is the trick. Put the flute in where the forward tooling hole goes to the front of the rib. And yes it does feel like you're trying to jam the rib into the skin.

[hugo]

No sweat Hugo! By the way, welcome to the group!!

-- John

Thank you Spike,

I am sure that fluting the ribs will help, but my concern is , because the force of the skin pulling outwards, there will be 'dips' close to the rivets. I did some rechearch on the Matronics (RV9 , November 2001 )list and found some interesting discussions about nose ribs and skins .
One of the sollutions was the following , and i quote :
[ I bent the hor. stab. quite a bit more
(around a 3/4" pipe fastened to a piece of angle iron
for stability.). I bent the skin so that laying on the
bench the top of the skin was about 14 to 15 inches
above the table at the rear edge. The skins ended up
smooth. You have to bend it around something to keep
from reducing the radius at the leading edge.

Bruce
RV-9A wings
Castro Valley, CA
]

Do you see 'dips' close to the clecos on your HS skin ?
Maybe i am too picky about this.

Hugo

[Spike]

Do you see 'dips' close to the clecos on your HS skin ?

Nope. You are right in that the skin does not want to be bent quite that far, especially at first. If you take the skin off and put it back on, starting at the nose and ending up at the tail, by the time you are finished that tendancy to pull away from the ribs will be just about gone. When its all said and done that force will be distributed across many many clecos/rivets and it will be just about non-existant. Give it a try and let us know how it goes

-- Spike

[hugo]

Ok,

After some research and work on the nose ribs I reassembled my HS together again. I fluted the ribs a little more, and sanded some material away from the top corners of the nose-ribs with my Scotch-brite wheel.I also bent the skin a little more around a 3/4" tube.
After that I could install the nose ribs without any effort and everything fitted very nicely.
I am going to use same m.o. for the left H.S.

hugo

[Spike]

Congrats!! Glad we could help out.