HS Completed! On to the VS with lots of questions!

Horizontal Stab. Completed! Thanks for everyone for their support, it won't be completed without your help!

Some minor issues popped up on completion of the HS.

1) I have a pneumatic squeezer and sometime I am getting offset shop/manufacture head result (see photo), I wonder what am I doing wrong here. I am still getting various comments on these rivet, whether I should replace them or leave them...



2) Sometimes the shop head is crooked and expanded the hole into an oval shape. If I replace the rivet, the replacement rivet's shop head will be crooked as well since it will try to fill the oval shaped hole...what should I do?



3) One of the rib to spar attachment leaves a gap, is this acceptable, can I do anything to avoid it? also, if I am to fix this, how do I do it to avoid the gap when I squeeze those rivets?



4) When I buck the 4-5 rivet, sometimes it forms a "skirt" shape shop head. I found the size 4 or above rivet is very hard to buck, I often has to use all my strength and often hard to control the bucking bar. Am I doing something wrong here? Is my 3X rivet gun not producing enough 'power'?



5) On my VS, attachment between the front spar and ribs, I crack one of the hole when I drilled out the defective rivet. I then tried to enlarge it to a size 5 hole but it still doesn't cover the crack. I decided to drill a new hole next to it and leave it open. However, how do I repair the crack as I don't think I can leave a crack open.



Thanks!
Hank

Thanks RVnoob, I got a few PMs, thanks! I do have one more question, I am using epoxy primer, and you can see in one of the photo, the primer cracks off when I dimple the skin....am I doing something wrong here or just this particular primer?

Thanks!

I am still open to any advice if anyone has comments on my problems, thanks!

Just a couple thoughts:

Why not prime after dimpling, not before?

The heavier the bucking bar, the better. Lots of folks use the tungsten BB's; I haven't tried one but those who have would trade their spouse for one if they had to replace a lost BB.

For 470 rivets, I found out after driving a lot of them that the longer rivet set doesn't bounce around nearly as much as the shorter ones. If space allows, I only use my 10 (?) inch set and my rivets are a lot better.

Squeezer: Hold it as straight as possible and squeeze it slowly. They are supposed to be used at 90 psi, but I turn down the pressure to about 50 for the 3/32's and 60 for the 1/8's. Run the ram up to just touch the rivet, make sure things are aligned, then squeeze the rivet. Won't work so well with long 1/8" rivets because the power maxes at full extension. When possible, have the moving ram work on the shop head with a small diameter set on it and use a larger one on the factory head. The small diameter set on the shop head side insures you are centered on the factory head.

On item 3, I presume you mean a gap between the pieces of metal you are riveting together. Not acceptable; here's an opportunity to practice drilling out rivets. But I'll bet that lots of folks just leave them and go on. Watch for a gap before riveting and use cleco clamps if the clecos don't keep them tight enough.

Your 3X gun should be plenty powerful--some folks use a 2X. Keep the pressure tight on the rivet.

I'm not sure what you mean by a "skirt shape". Maybe something I havne't noticed. I am concerned by what looks like a crack around the rivet in the pic.

I have a couple rivets that look like your top one. The shop head looks great but viewed from the side like that it isn't centered.

What did the PM's mention on that one?

HighSchoolBuilders said:

Thanks RVnoob, I got a few PMs, thanks! I do have one more question, I am using epoxy primer, and you can see in one of the photo, the primer cracks off when I dimple the skin....am I doing something wrong here or just this particular primer?

Thanks!

Click to expand...

The primer shouldn't crack and it certainly shouldn't flake off like that from dimpling. It's likely either a problem with the primer itself (maybe contaminated, improperly mixed, or just a poor quality product?) or a problem with how you're applying it (maybe too thick a coat, or not preparing the surface properly?).

I've been using AKZO epoxy primer and regularly dimple after a surface has been primed -- never any problems.

A common misconception that I had when I started, was that the squeezer was 'automatic'...perfect rivet every time! Not quite, it is a great tool, but you have to pay attention when using it to get good results. Concentrate on getting it straight and square. Also be sure to get the rivet in the center of the set every time (especially on the flathead 426's). If its centered on the factory head and not quite centered on the shop head, you are not squeezing on the centerline of the rivet and consequently you will bet crooked rivets.

As for the epoxy primer. I can see you are using something different than me (AKZO), but I would expect all epoxy primers should be similar in their durability...thats the beauty of using it. And from my experience, I have never had it crack and peel like that. Double check the manufacturers guidelines for application. Be sure you are mixing it properly. Mix each part seperately before mixing them together.

Best of luck, and dont stress too much, its looking good so far and you'll get the hang of these little things and be skilled enough to be giving advice to others in no time!

...also make sure you are preparing the surface adequately before applying the primer. I use these steps...

1. Clean part with soap and water
2. Alumiprep applied/scrubbed with a scotchbrite pad to scuff the surface
3. Alodine
4. Primer

maybe a little overkill, but it works great.

Just 2 more cents. Conversion coating (ie Alodine) is not required for proper adhesion of a primer. Application or non-application of alodine won't effect the primer. However, proper prep of the metal in accordance with the primer manufacuter's instructions has everything to do how well the primer adheres. If your primer didn't come with any instructions, then then steps listed by RV7Ron's should work just fine.

For what it's worth, priming for me was the last step before riveting so I never had the flaking issues you are running into.

Auburntsts said:

Just 2 more cents. Conversion coating (ie Alodine) is not required for proper adhesion of a primer. Application or non-application of alodine won't effect the primer. However, proper prep of the metal in accordance with the primer manufacuter's instructions has everything to do how well the primer adheres. If your primer didn't come with any instructions, then then steps listed by RV7Ron's should work just fine.

For what it's worth, priming for me was the last step before riveting so I never had the flaking issues you are running into.

Click to expand...

totally agree, the alodine step is kind of a 'belt and suspenders' philosophy...there is a strong argument that it is not needed.

Thanks Thanks Thanks!

Thanks! That's a lot of good info!

Scott,
I heard the same about the Tungsten, I am ordering one to try it out, I hope it's worth the money, quite expensive for a piece of metal!

Thanks for the advice on the 470 driving and squeezing technique. I've tried the squeezing method you mention, it works great!

As for the gap, that's the frustrating part. The skins are clamped tight but it's almost as if I squeeze it too hard or something, the metal opens up as I squeeze, it spread out as I squeeze it.



Calvin25,
I think I squeezed them not center enough with my pneumatic squeezer. What Scott told me just before your comment works for me, give it a shot.

There were a few advices given regarding what to do with those rivets. The easy one is, if only a few (less than 5%) are like that, leave it.

Of course, you may drill them out but the second attempt will guarantee to look even worst, because the hole will probably enlarged and the uneven hole will invites poor results. You can go for the oops rivet but they're non-structural, although they will look better than just leaving it.

Here's the correct photo of the "Skirt" shop head:

Primer

I think my primer crack might have something to do with my surface preparation.

Sometimes I have some leftover primer and don't want to waste them, I will then spray the other components, since I figure I will need to prime them anyway...but the cracking on the dimple and leads to other problem, lesson learned. Better waste those primer than time and energy.

HighSchoolBuilders said:

As for the gap, that's the frustrating part. The skins are clamped tight but it's almost as if I squeeze it too hard or something, the metal opens up as I squeeze, it spread out as I squeeze it.

Click to expand...

My theory on this is that the rib web is not long enough to allow it sit flush against the spar. No matter how hard you clamp it, it may look flush from the edge but still have a little gap at the rivet hole which then allows the rivet to expand between the sheets.

FWIW, I asked Van's about this exact picture (mine looked the same) and they said it's acceptable and often unavoidable in this particular spot.

Boris

borislav said:

My theory on this is that the rib web is not long enough to allow it sit flush against the spar. No matter how hard you clamp it, it may look flush from the edge but still have a little gap at the rivet hole which then allows the rivet to expand between the sheets.

FWIW, I asked Van's about this exact picture (mine looked the same) and they said it's acceptable and often unavoidable in this particular spot.

Boris

Click to expand...

Common enough to have a name...its called 'scalloping'. Happened to me too but not in that area, still bugs me to look at it and it should be avoided if possible..but ok to build on.

The "skirt": Wow! I haven't seen that before. Every now and then, someone comes up with something new.

My guess, and that's all it is, a guess, is that you didn't hold the bar tightly against the rivet. You need pressure on the rivet with the gun and a little less pressure with the bar. Maybe someone else actually knows.

The gap between flanges I believe comes from not holding the squeezer tightly against the rivet, so that as it starts to squeeze it is free to expand between the skins in addition to expanding the shop head end. This assumes that the skins were tight before riveting.

As someone else mentioned, drilling rivets often makes the situation worse. I've gotten to where I think twice or maybe 3 times before drilling a rivet and I have to have a good reason why I shouldn't leave it there. Next time you order from Avery, get a "micro shear flush cutter", cat #56662, $10. When you drill a rivet, use this cutter to pull the shop head off. Don't try to cut with it, just grip the shop head with it. Works great.

I love my tungsten bucking bar

It fits everywhere and is very easy to hold. Worth the money for the effort it saves. It is expensive and works hard so we gave it a special place on our tools shelf.

Which one?

I am getting one! I already have a holy spot saved for it/them... I had a look at Avery Tools, do you know which one should I get if I only have $$ for 1, maximum two if it is a must.

They have about 5-6 of them in their site:
https://www.averytools.com/p-946-tungsten-steel-bucking-bars.aspx

Thanks!

HighSchoolBuilders said:

I am getting one! I already have a holy spot saved for it/them... I had a look at Avery Tools, do you know which one should I get if I only have $$ for 1, maximum two if it is a must.

They have about 5-6 of them in their site:
https://www.averytools.com/p-946-tungsten-steel-bucking-bars.aspx

Thanks!

Click to expand...

I have the last one on the list...and couldnt live without it.

Hank, I bought mine from Flyboy Accessories

The owner is Vince, a Rocket builder. He has an online store and has built a fabulous airplane. Nice guy too.!

http://www.flyboyaccessories.com/store/


I bought the rectangular bar and it works very well. ($90)


http://www.flyboyaccessories.com/store/index.php?main_page=product_info&cPath=70&products_id=305

He took my order over the phone and the Bar was delivered in a few days. Great service.

You will be surprised how well these bars work. Because they are so dense, your work will be improved.

A few observations:

1. Don't prime your parts until all the holes and edges have been dimpled and deburred. Priming is the LAST thing you do before riveting. One coat, not multiple coats. Make sure the prime is completely dry with no runs or half dryed spots.

2.Make sure your flanges are bent to favor a tight fit before riveting. Under bending a Rib Flange slightly will make it spring tighter against the piece while riveting.

3. You're putting the primer on too thick. (at least from the photos).

4. Put some tape on the bars to keep them from scratching up the neighboring aluminum.

5. Perhaps your 3X gun is set too high? Bump it down to 45 PSI.

6. Do you have a Bucking Buddy when you start shooting rivets or do you do it all yourself?...Consider trading positions. Have them run the Rivet gun and you focus on the Bar. Switch places once in a while.

Good luck to you; I appreciate your project and look forward to your updates!

Just came home from a trip and it's full of good advice, many thanks for all the suggestions! I think my priming prep is not good enough, will try those method on my next run. The problem is, I can't get aviation primer in Hong Kong. Those are very hard to come by and I don't want to waste them, so when I have left over, I would spray them on components, thinking they need priming anyway and won't hurt with an extra layer...I guess I need to learn how to let go on those primer

I placed my order on that Tungsten BB, really looking forward to some quality bucking action!

Thanks again!
Hank