Darn Edge distances ...

Post by **Spike** » Wed Mar 02, 2005 12:44 pm

I was working on the rudder the other night and trimmed the Rudder Horn brace (R-918) as per the plans.

The problem though is that I didnt make the edge distance minimums for the flange rivets. I find this to be quite frustrating as your almost forced to trim it this far down due to the way that Van's prepunches holes in the part to use as scribes.

Anyway, I managed to talk to a friend of mine building an 8 and he had the exact same problem. He called Vans when he did this and they suggested that he add a transverse row of 3 rivets to each side of the part that would meet edge distance requirements. I looked at how it turned out and was happy with their solution so I used it. The results:

The only thing that is not spec about this fix is that the parallel centers of the two rows dont quite meet minimum pitch spec, though I'm not really worried about that as the part is squarely secured now and all rivets have at least the minimum edge distance in the axis of loading and the new transverse rows have the spec'ed distances in all axis.

If you havent fabricated this part yet, make sure you go slow and check progress after each subsequent cut. Dont just jump into the water using Vans prepunched holes as guides.

-- Spike

tshort · Post by **tshort** » Wed Mar 02, 2005 7:47 pm

I cut that part right before I left on vacation - I cut thru the center of the holes, so I think I should be OK (only problem, there will be little "divots" on the edge of the part...) ... it looked like it was enough distance.
On your mirror picture, it shows that there really isn't much leeway - much longer and it would butt against the channel of the rib... seems like it would have been better not to prepunch the holes in the rib and let us make the edge distance correct.
Thanks for the pictures!

Thomas

Post by **Spike** » Wed Mar 02, 2005 7:59 pm

I completely agree Thomas. When I trimmed the part I did it just enough to get rid of the punched holes that they provide. That was too much though. I had thought about just cutting them in half like you did but frankly thought that wasnt reasonable as the amount of effort that it would take to properly edge prep the remaining hole halves didnt seem to fit their intent. You will most likely end up with a better part than I, just make sure you prep those hole remains well.

-- John

captain_john · Post by **captain_john** » Wed Mar 02, 2005 8:11 pm

Good fix!

Tell me, as I recall... the original holes line up with skin rivets. I expect you will fill them with the intended rivets.

The new holes... will they be dimpled and sit flush underneath the skin or penetrate all three pieces?

Either way is good. Just wondering how you plan on doing it.

CJ

Post by **Spike** » Wed Mar 02, 2005 8:36 pm

D@mn CJ, maybe they did. Maybe thats what they were for. If so im a dope.

I plan on dimpling all of the holes. The 3 new ones will only go through the bottom rib and the brace. They will be set before I put the skin on. From the outside of the aircraft you will only see the original 4 that were supposed to be there.

-- Spike

Post by **Spike** » Wed Mar 02, 2005 8:47 pm

Now that I think about it CJ, if those holes were prepunched to match the skins then the isometrics on the plans are incorrect. The instructions call your attention to the detailed drawing of the part for guidance on where to trim it. Those holes are placed improperly according to the isometric drawing if they are to be kept. I wonder if this is a case where they have used a rudder brace from the beginning and failed to update the detailed drawing when the punch machines came along.

-- John

captain_john · Post by **captain_john** » Wed Mar 02, 2005 8:52 pm

There ya go!!!

Nobody will be the wiser!!!

Word to the wise...

When drilling (and subsequently riveting) the bottom rib to the skin... be cautious not to bend the trailing edge by doing one entire side and then the other. This will pull the skin to one side and deform the trailing edge (which I KNOW you will NAIL on the FIRST TRY!) and cause it to bow.

I drilled the skin to the SPAR first, then the skin to the ribs, starting from the leading edge and going back. I riveted in the same order.

Hope this helps!

CJ

captain_john · Post by **captain_john** » Wed Mar 02, 2005 8:55 pm

BTW, I didn't build your rudder. I built the old style folded edge rudder.

Not sure what you mean by isometrics, but I didn't cut mine short and am not sure why. If it can be screwed up, I usually do it!

CJ

tshort · Post by **tshort** » Wed Mar 02, 2005 9:08 pm

Don't have it in front of me, but those holes were for cutting guidance only - they weren't anywhere near the rest of the holes (assuming those are the ones you're talking about...) - I checked before cutting!

Thomas

Post by **Spike** » Wed Mar 02, 2005 9:10 pm

Isometrics are the cute type of drawings that they put on the big plans pages.
As for the order of drilling things, I clecoed the whole entire rudder together before I match drilled any of the holes the skin. Im pretty anal about such things. I typically do a complete assembly, then remove a cleco at a time to do the match drilling and then put them back before moving on.

-- Spike

captain_john · Post by **captain_john** » Wed Mar 02, 2005 9:12 pm

OH!!!!

I see the confusion!

No, those holes are for cutting.

They are not intended to line up with the skin.

I was asking if you planned on drilling all 7 through the skin.

I would just do the 4 that are supposed to shoot through the skin.

CJ

mustang · Post by **mustang** » Thu Mar 03, 2005 3:18 am

Spike,
I noticed the same thing when I built mine. The holes on the brace were a little close to the edge. I did trim the piece properly so I was a bit disappointed. However, I riveted them in place and carried on. The inspector looked closely at the parts but did not mention anything wrong.

I looked at the RV-4 rudder the other day and it didn't have all of the bracing that the "eights" do. In fact, there was a hole right through the rudder where our brace is placed. So, not ot sweat this too much.
Cheers, Pete