Flap Twist

[jtsmith]

Hello;

Is it normal to have twist in a flap prior to riveting the bottom skin to the spar?
I can weight the flap down and it will lie flat on the table. Will the twist disappear after riveting the bottom skin to the spar if the flap is kept flat against the table? Has anyone tried laying the flap on the table upside down, drilling and clecoing the trailing edge to the table. Weighting down the flap and then using blind rivets to attach the bottom skin to the spar? Would using blind rivets be acceptable for attaching the skin to the spar?

Thanks;
Jearld
91066

 

[Mel]

Just make sure that the flap is straight while riveting. Blind rivets are approved on RVs anywhere except the wing main spars.
Mel...DAR

 

[rv9aviator]

I weighted my flaps down to a flat table and drilled the trailing edge right onto that table, clecoing as I went. I then prosealed the trailing edge together using clecos and weights to hold it flat on the table. I left it that way for 4-5 days and then back riveted the trailing edge. It is nice and straight. You can see the flaps clecoed and weighed down on my website. Look at the wing section. www.jimsairplanes.com

 

[mikehoover]

Blind rivets okay?

Use lots of weight. I bought three 25# bags of lead shot (total 75#) from the local hardware/sporting goods store, divvy'd them up into 12# sacks of muslin cloth from Walmart so I could spread the wieght over the 2x2 board used along the length of the flap to make it lie flat. This worked great. The little weight sacks have come in handy since then to hold parts in various ways while working with them.

Question on the blind rivets:

Blind rivets are approved on RVs anywhere except the wing main spars...

I used the blind rivets (MK319BS - the 1/8" grip should be ample.) on the flaps on the bottom skin/spar because I had such a terrible time trying to buck those. The rivet holes were a little large and the rivets kept bending over - smaller ones yielded too tiny shop heads. So I popped them all along the bottom skin to spar. I asked Vans if okay on two occasions. First call said to buck them; second call said it was okay if not stronger due to the bit of steel mandrel left inside the rivet. So I still kinda worry whether this is okay. Comments? Thanks!

 

[Mel]

Mike,
You say that the rivet holes were large. This is no place for blind rivets. Since blind rivets do not expand in the hole like driven rivets, they MUST be used where the holes are the proper size. If the hole is oversized, to use blind rivets, you must go to the next size.
Mel...DAR

 

[rv9aviator]

Mel, I bet they were a little large for the regular rivet. He would have had to drill them out slightly bigger for the 319 rivet so hopefully everything is OK.
Just being optimistic!

 

[mikehoover]

Blind rivets

It's been over a year ago, but the best I remember is that the blind rivets formed a good head with the "ball" on the tip of the mandrel still exposed a bit and were nice and tight. The holes weren't overly enlarged, but countersinking did enlarge some of them, as is typical when countersinking the minimal thickness of metal. I think the flap spars are 0.040 thick so there is that tendency to have the hole a little bigger than desired. But like Jim said, I did actually have to go in with the 7/64" drill to make sure the holes (thru all layers) were large enough to get the blind rivets inserted. So I imagine the blind rivets are okay IF if is okay to use them in this situation. Certainly it would be great to think they are fine, but I'd rather know for sure and get them right. I'd hate to have to drill them all out and pop bigger ones in there (and have little rivet drillings rattling around inside) but I will do that if required. Is there any way to tell on the finished flap whether or not those blind rivets are acceptable? Thanks!

 

[N916K]

Hello;

Is it normal to have twist in a flap prior to riveting the bottom skin to the spar?
I can weight the flap down and it will lie flat on the table. Will the twist disappear after riveting the bottom skin to the spar if the flap is kept flat against the table? Has anyone tried laying the flap on the table upside down, drilling and clecoing the trailing edge to the table. Weighting down the flap and then using blind rivets to attach the bottom skin to the spar? Would using blind rivets be acceptable for attaching the skin to the spar?

Thanks;
Jearld
91066

You should be able to attach both skins to the spare without too much trouble. If you are having trouble getting a bucking bar it there maybe it's time to expand your bucking bar collection. I think I used a very small bar, about the size of a deck of cards that had a cut out on one end that you put your fingure tips. Something like an Avery 615.

To keep the twist out I riveted the skins to the spar before I drilled the trailing edge. I used the method you described. I held the flap down on a flat table upside down then drilled and clecoed the trailing edge to the table. Also work slowly and flip the flap over a few times when riveting the trailing edges. I used no proseal and the trailing edges came out very straight. You just have to go slow.

Good luck, I'm sure it will come out just fine.

 

[alpinelakespilot2000]

Just make sure that the flap is straight while riveting. Blind rivets are approved on RVs anywhere except the wing main spars.
Mel...DAR

Mel-
I'm not sure if you are talking about a particular set of rivets on the main spar, but Van's specifically indicated to me, and I know to a number of others, that LP4's or CherryMax's of the appropriate lenght are perfectly acceptable for the leading edge rib to spar rivets. If somebody at Van's gave me (and others) bad advice, I'd certainly be interested in knowing that.
Steve