S

skidmk

Well Known Member
okay, go the left aileron back from Vans, installed it today and was about to do the flap and hinge,,, I just realized that I've installed the flap gap already and I forgot to dimple the skin and the flap gap. :(

now,, I could drill out the pulled rivets (although there are 3 cherry max yuck) and re-do it... or could I just machine the countersink in the skin?

M
 
Not sure what you mean

So the flap brace is riveted to the spar web, but not to the skin? Is that what you mean?

If so, you can probably just dimple the brace and the skin simultaneosly. They're both pretty thin, and I'd bet they dimple well together. Failing that, can you bend the brace out of the way and dimple them separately?

Of course, if I misunderstood you, just hit the "Ignore this!" key and move on.
 
yup you hit it on the head,, the brace is riveted to the spar web. Not the skin... I'll try the simultanous dimple...

what a great idea,, I didn't even want to contemplate drilling out the cherry max's....

M
 
Definitely just dimple the two layers together. This works basically just as well as doing each layer separately, particularly if they are thin layers. I've "triple-dimpled" before by accident, and even that worked out just fine. Occasionally this trick will come in handy when you botch a rivet and decide to go up to AN426AD-4 rivets assuming you can still get the squeezer on the hole. Good luck.
 
skidmk said:
what a great idea,, I didn't even want to contemplate drilling out the cherry max's....
Click to expand...

Oh, boy, yeah...pulled rivets in general are easy to install and a nightmare to take out! Half the time they just spin with the drill bit.
 
Mike you're not the first one to do it :) Good luck dimpling that.. it is thick! gap brace is at least 040, I'd guess and skin is 032.. so it'll be interesting :) Don't forget the piano hinge goes there as well.

I consulted with Vans regarding this and they said -- carefully countersink 032 skin (can be done!) for normal rivets and there are a few holes in 025 outboard skin that can be countersunk for oops rivets...

just a thought...
 
Radomir said:
Mike you're not the first one to do it :) Good luck dimpling that.. it is thick! gap brace is at least 040, I'd guess and skin is 032.. so it'll be interesting :) Don't forget the piano hinge goes there as well.

I consulted with Vans regarding this and they said -- carefully countersink 032 skin (can be done!) for normal rivets and there are a few holes in 025 outboard skin that can be countersunk for oops rivets...

just a thought...
Click to expand...

Yeah, Mike, you might want to try one hole first. The dimpling advice I gave you was based on the RV-9 flap/aileron brace. Not sure how thick the skin and brace are on the -8, but the -8's may be thicker. Still it's worth a try in at least one hole first. Countersinking an .032 skin is OK as well (we do this on fuel tanks, remember) but the depth has to be almost perfectly set. Whichever you end up doing, let us know how it turns out. Good luck.
 
Fellow Colonial

Mike, i wouldn't feel to bad about it. The Builder Manual was pretty thin in this area.
I seem to remember being instructed to machine counter sink some ridiculously thin sheet in this area. I dimpled it.
What you might try is gently bending the flap brace back and dimpling one skin at a time.
Pete.
 
Just worked on this area recently. After the flap hinge is mounted, you end up with a three layer "sandwich", with the flap hinge on the inside, the flap brace in the middle, and the skin on the outside. If you "double dimple" the skin and flap brace together, you'll have to countersink the soft hinge, which is apparently not preferred, and would almost certainly complicate fitting the flap hinge. If it were me, I'd countersink the skin, and I don't say that lightly, since I really don't like countersinking all that much. The combined skin (0.032) and flap brace (0.040) should give you plenty of pilot hole to keep the countersink bit running true, and a countersink is an approved process for a -3 rivet in an 0.032 skin. If you've only done the one wing, you can revert to the normal dimpled skin, countersunk flap brace, and plain flap hinge on the other.
 
Three layers = Dimple - CS - Nothing

While it doesn't say what to do in the instructions, Chapter 5 indicates that when three layers are all fastened together, the outside layer should be dimpled, the middle layer countersunk, and the inside layer should be left alone.

So in this case, you should ideally dimple the skin, CS the brace, and leave the hinge alone. In reality, the hinge may get a very slight CS if the brace material is not think enough for the CS.

I tend to think this is a fairly high stress joint, since it's the only thing holding the flap on the wing, and we all know that having that thing out at 100 IAS will be quite a bit of stress. I think I would try to bend the brace enough to dimple the skin and CS the brace. If that's not possible, then I would drill them out.


OR: It's on the bottom of a low-wing airplane. No one is going to see this. Consider using universal heads. I know it's ugly, but at least your flap won't be....flapping in the wind. Excess drag would also be very small. Cessnas, Pipers, etc are almost ALL universals.

Best of luck!
 
vmirv8bldr said:
OR: It's on the bottom of a low-wing airplane. No one is going to see this. Consider using universal heads.
Click to expand...

That's what I did. I have a quickbuild, which meant I couldn't cleco the brace to the spar to fit the flaps because the skins were already riveted on. So I riveted the brace to the spar first and then fit the flaps. I've never heard of anybody else complaining about this issue on a quickbuild. I don't know how everybody else gets around it. I figured the universal head rivets would make for a stronger assembly than countersinking the skin.
 
I just did this last week, and dimpling the two layers is absolutely no problem. I fitted and drilled the hinge first, using a technique that I stole from someone else on the forum :rolleyes: The suggestion was to stick a reduced head rivet in every other hole of the gap seal/skin combo to maintain their alignment. The hinge clamps over the heads, then you drill the holes that don't have the rivets stuck in them. Finally, remove the rivets, cleco the holes, and drill the rest. Worked beautifully. Thanks to whoever came up with that idea :)

Once that was drilled, I dimpled the skin/gap seal combo, and also dimpled the hinge. I believe Van's prefers that you NOT dimple the hinge material, but I've never seen it cause a problem, and it makes better sense to me than machining off so much of the material.

Good luck,
Rusty (flying in a few weeks)
 
Mine is a quickbuild as well. I clecoed on the flap brace, match drilled it to the spar and the skin, then dimpled the skin, and countersunk the flap brace. I then riveted the flap brace to the spar. To fit the flap, I put a couple of alignment "oops" rivets in backwards (head inside the flap brace and tail sticking out from the skin, and not set, of course) to keep the flap brace and skin correctly aligned, clamped on the flap and hinge and started adjusting. When I had the flap positioned correctly, I drilled one hole through the flap hinge, reaching inside through the lightening hole to keep the hinge from pushing back (thanks Orndorff video!) and clecoed it. I then worked outward in both directions from that hole using light pressure and a fast turning drill. When the majority of holes were done, I removed enough clecoes to be able to pop out the alingment rivet/dowels, clecoed it back down and finished up the match drilling.
As for your existing "problem" wing, the universal head rivets are certainly a viable and reasonable choice, but with that 0.040 brace in there and the close rivet spacing, I really don't think that a properly countersunk skin would cause any problems.
 
Well,,, looks like I've taken abit of info from everyone. I was able to dimple the skin and the brace together with my pneumatic. worked like a charm. fitted the hinge and drilled. it. Now, I'll speak to vans tommorrow and make sure this is all kosher,, but it looks like riveting it all together should work fine.

M
 
CSK the hinge?

skidmk said:
Well,,, looks like I've taken abit of info from everyone. I was able to dimple the skin and the brace together with my pneumatic. worked like a charm. fitted the hinge and drilled. it. Now, I'll speak to vans tommorrow and make sure this is all kosher,, but it looks like riveting it all together should work fine.

M
Click to expand...
I will have this same issue. Did you countersink the hinge for the dimples?
 
I left the hinge alone, (3rd layer) in accordance with chapter 5... dimple skin, cs brace (which i dimpled of course) and hinge left alone.

M
 
skidmk said:
I left the hinge alone, (3rd layer) in accordance with chapter 5... dimple skin, cs brace (which i dimpled of course) and hinge left alone.

M
Click to expand...

If you dimpled the skin and flap brace, then you'll need to either dimple, or countersink the hinge or it won't lay flat against the brace.

Cheers,
Rusty
 
Dumba** of the week

Is me I'm afraid.

Having finished the RV I'm now catching up on all the other chores.

So wrenching a very large nut on my tractor I used a very unsafe extension bar which if it let go was going to hit me right in the "Bang"...Forehead...Blood everywhere...

"Don't go down in the shop...no body is home"...Get out and get help.

Staggard out of shop to neighbour's house, got taken to ER room...About 30 stiches and the mother of all 4 day headaches I'm all set for Halloween!


Needless to say I haven't done much flying since!

I bet the deductable part of the bill would have paid for a nice set of PROPER wrenches.

Should have seen the lecture the scary RN gave me about what permanent facial damage I would have had if the bar had not hit me square in the forehead.


Lesson.....TOOLS ARE CHEAP...buy 'em or don't do it!

Frank
 
Frank,,, ouch!!.....glad you're okay. As for the hinge,,, I'll have to CS it like Rusty says... another lesson... learned go slower (thought I was already good and slow)

M
 
Indeed

But I'm sure I dimpled my hinges and they came out fine.

Frank
7a and a headache.
 
I'm glad I read this thread. I have not installed my flaps yet but was planning on c-sinking the hinge. Is the .040 brace enough to accept a .032 DIMPLED skin? I know you can c-sink for a rivet head no problem but a dimple in the skin requires a much larger c-sink. Or is it ok to enlarge the hole in the flap brace a little?
 
my problem was trying to fix a stupid mistake. I had pop riveted the brace to the spar b4 I dimpled and cs'd everything. The way to do it properly... is dimple the skin.. cs the brace and leave the hinge alone. mea culpa mea culpa... I didn't do it that way,, I'm having to dimple the skin, and brace together and then cs the hinge. (or dimple)... and I'll be cs'ing the darn thing

M
 
briand,

Yes the 0.040 flap brace can be countersunk to accept the dimple. I used a piece of 0.062 scrap with a #40 hole in it to keep the cutter pilot straight. Cleco it to the flap brace, then side clamp it down, remove the cleco, and countersink. Got great results, and the cutter would just barely kiss the underlying pilot piece.
 
skidmk said:
my problem was trying to fix a stupid mistake. I had pop riveted the brace to the spar b4 I dimpled and cs'd everything. The way to do it properly... is dimple the skin.. cs the brace and leave the hinge alone.
Click to expand...
What is so frustrating, and is true of a number of places in the manual, is the lack of instruction. These planes are being built by first time builders with no previous experience, and some with very little engineering or manufacturing experience. A single warning sentence in the manual would have avoided this, but if you follow the manual exactly (and why wouldn't you?) then you end up with this problem. And yes, I'm in the same boat too. Grrrr. :-(
 
I feel your pain. I dimpled the skin and brace together with my pneumatic and it worked well. take your time, go slow and you should be okay. Afterwards use some scrap and cleco the scrap and the hinge together for a pilot hole and cs.....

as for the manual.. not the first time or the last time I'll bugger up I'm sure...

maybe its just us colonials that don't get this stuff <VBG>
 
Not too deep

William Slaughter said:
briand,

Yes the 0.040 flap brace can be countersunk to accept the dimple. I used a piece of 0.062 scrap with a #40 hole in it to keep the cutter pilot straight. Cleco it to the flap brace, then side clamp it down, remove the cleco, and countersink. Got great results, and the cutter would just barely kiss the underlying pilot piece.
Click to expand...

William..... if you just kiss the underlying scrap, you are creating a countersink that would set a regular rivet 0.008 to 0.010 inches deeper than the surface.
Even the "tank dimple dies" don't go this deep. I would aim for only 0.003 to 0.005 inches deeper than a flush rivet fit.
While a slightly deeper countersink might look like a "better fit", simple geometry prevents the skins really clinching up tight.

Just for clarification... I'm talking about 3/32 rivets...

gil in Tucson
 
CSK the flap brace in place?

I just had a quick look, and I reckon that after I match drill the hinge and everything, I should be able to flex the flap brace away from the skin enough to countersink with a mini-cage. I'll probably need a helper though. I'm going to investigate that option first before countersinking the hinge. Of course, once I've started that course of action I'd better be certain its going to work out. I'll tackle it when I get to that stage. I was going to leave fitting the flaps until the wings were on the plane, but I reckon I'll need to tackle this sooner than that while access is easier...
 
Add a back-up strip

AntiGravity said:
I just had a quick look, and I reckon that after I match drill the hinge and everything, I should be able to flex the flap brace away from the skin enough to countersink with a mini-cage. I'll probably need a helper though. I'm going to investigate that option first before countersinking the hinge. Of course, once I've started that course of action I'd better be certain its going to work out. I'll tackle it when I get to that stage. I was going to leave fitting the flaps until the wings were on the plane, but I reckon I'll need to tackle this sooner than that while access is easier...
Click to expand...

Jeff ... if you do countersink the hinge, you may loose some strength due to the "knife edge" being created in the soft hinge material. The shop head would be bearing on a reduced thickness of this softer material.

A easy fix would be a back up strip - say 0.032 by 5/8 - as a fourth layer in the stack-up - with no dimples or countersinks. With the flaps deployed at high speed, I bet there are large forces involved trying to rip this hinge off the brace. With turbulence, etc. ... I would also bet that the forces are not in a nice shear direction on the rivets in question. Just look at a deployed flap shake around during approach... :)

The added weight would be negligble, but a lot of strength would be gained.

I'm assuming that the softer hinge is the top most layer in the three layer stack-up...

gil in Tucson
 
Countersink the flap brace

Hi Gil,

thanks for the comments, and I agree. I don't wish to countersink the hinge and I think I can flex the flap brace away from the skin enough to get a mini-microstop in there and countersink the flap brace, leaving the hinge intact. Thus the skin would be dimpled, the flap brace countersunk to accept the dimple, and then the hinge left as is.

If I can't do this, then I'll have to dimple the skin and flap brace together and countersink the hinge. I think in this case your idea of a backing strip is a good one that I'll definitely run past Vans. Certainly makes sense to me though.

Hopefully, I'll be able to countersink that flap brace in situ... we'll see.

Cheers,
 
I just went back and reread my instructions for building the flap (I looked at the flap too but since its half of the hinge is already riveted on I couldn't see much). It says to leave the hinge on after you match drill it to the skin and spar and use the hinge as a guide for the c-sink cutter. I don't see why I couldn't do the same when c-sinking the flap brace too. Removing the skin first obviously.
 
Hi Gil,

The countersinking I described was to accept the dimpled 0.032 skin, not just a rivet. To set the countersink depth, I dimpled a piece of 0.032 scrap to make a gauge, then gradually worked the countersink tool deeper until the "shoulder" of the gauge just barely sits down onto the surface surrounding the countersink, while the protruding portion of the dimple still fits snugly in the countersink. This does result in a slightly larger/deeper countersink than for just the rivet alone, for the same geometric reasons you mentioned. My point in mentioning that the countersink might have just touched the underlying guide was not that that would/should happen, but that the hole in the 0.040 flap brace would not be enlarged inordinately by the countersinking, as would be evidenced by the countersink cutter really getting into the guide piece. Sorry if my initial quick description was misleading.
 
well,,, i bit the bullet. ordered 2 new braces and some rivets. Practiced drilling out the pop rivets... piece of cake.. the non-cherries are real easy, and the cherries are easy if you take you time.... not one oversized hole. Sooooo.......... fitted it all and drilled it all and CS'd the brace woohoo!... tommorrow, I'll finish drilling the hinge.

M
 
Good going....

skidmk said:
well,,, i bit the bullet. ordered 2 new braces and some rivets. Practiced drilling out the pop rivets... piece of cake.. the non-cherries are real easy, and the cherries are easy if you take you time.... not one oversized hole. Sooooo.......... fitted it all and drilled it all and CS'd the brace woohoo!... tommorrow, I'll finish drilling the hinge.

M
Click to expand...

Mike ... sounds good... glad you could do it the recommended way.... :)

gil in Tucson
 
Well,,, after all the boogie man stories about drilling cherry max rivets,,, I found a site that gives you a step by step way to do it. Once I practiced a little bit, I found removing the pop rivets was very easy.. no spinning,, and no over drilling....

M
 
You must log in or register to reply here.