Am I dimpling enough? Can a perfect flat surface really be achieved?

So I'm 90% done with my empennage and expect the Fuse kit to ship 12/9.. I'm looking at my finished work and wondering if it could be better I have dimpled everything possible with a c-frame standard dies on all parts, I have a full halo and what appear to be crisp dimples, rivets sitting down nice and flush...Once riveted it looks good but some distortion surrounds all rivets... Material is stretched and a rivet smashed into it....How can there not be? I've looked at many airplanes and build site photos.. Looks like my results are consistent with what I am seeing in others work... I've experimented with SS and tank dies on sample material (SS die on some 032 and normal die on overlying 020) same results. I have a Bonanza and a Cherokee in my hanger right now and everywhere there is a rivet on these airplanes there is minor skin distortion, when viewed at the proper angle.... Just like my 7 tail...

I see people making claims that their skins are perfect like glass and if not you probably don't know how to dimple?????? Or rivet? Can this be true?

Is it possible to have zero distortion? if so how do I achieve this ?

I've seen some bad RV tails and I don't think my work falls into that category but if I'm wrong now is the time to fix it...

Input appreciated!

Thanks

I'm no expert, but I used the Hydro-Pneumatic crimper with dimple dies to make my dimples on everyplace the the head would reach. Easy, and repeatable. Going to make a fixture to attach it the the DRDT-2.
Tom

Overall skin finish quality is based on two separate process...
Part prep and riveting technique (I.E. someone with a lower riveting skill level can make perfectly prepped parts look bad - a pro riveter can't make poorly prepped parts look great).

Your description of a full halo doesn't tell the entire story because that means different things to different people.
Basically, a properly formed dimple will result in the entire footprint / contact area of the dimple die being scuffed/discolored on the skin surface.
If you only have a scuffed ring around the outer perimeter, the dies did not fully seat.
The best thing to do is learn how to read the skin for flatness using the skin reflection as described in the latest rev. of Section 5

My personal list of tools for dimpling in order of finish quality are
1. C-frame tool (particularly on larger dimples and/or thicker skins)
2. Pneumatic squeezer (only use it if I have to)
3. hand squeezer (never use it on exterior skins)

I know many people use the DRDT-2 tool. My experience is that it is not quite as good as the c-frame (particularly on thicker skins), but it may have been the particular tool I used.

If you are able to determine that your dimples are well formed using the skin reflection, then riveting technique would be evaluated.

I picked up a set of the Economy dimple dies from ACS for use on my current project. I dimpled my first skin, a horizontal stab skin, and the skin was completely bowed using the c-frame and a deadblow hammer like I have many times before. I pulled out my trusty 10 year old Avery dimple dies and redid the skin. It came out perfect as usual.

So far in my experience these are the do's & don't of dimpling...

Use a c-frame with a deal blow hammer whenever possible.
Use 2 solid blows per dimple. If you can't get a solid hit on it then multiple softer blows is fine.
Never use a framing hammer.
Never let the return spring on the c-frame allow a space between the skin and die before hitting it. I just removed the return spring.
Don't be scared to modify the outside diameter of a die to allow proper fit. It's better to buy another set than put stress on the web-to-flange radius.
Always c-frame dimple tank skins.

rvbuilder2002 said:

Overall skin finish quality is based on two separate process...
Part prep and riveting technique (I.E. someone with a lower riveting skill level can make perfectly prepped parts look bad - a pro riveter can't make poorly prepped parts look great).

Your description of a full halo doesn't tell the entire story because that means different things to different people.
Basically, a properly formed dimple will result in the entire footprint / contact area of the dimple die being scuffed/discolored on the skin surface.
If you only have a scuffed ring around the outer perimeter, the dies did not fully seat.
The best thing to do is learn how to read the skin for flatness using the skin reflection as described in the latest rev. of Section 5

My personal list of tools for dimpling in order of finish quality are
1. C-frame tool (particularly on larger dimples and/or thicker skins)
2. Pneumatic squeezer (only use it if I have to)
3. hand squeezer (never use it on exterior skins)

I know many people use the DRDT-2 tool. My experience is that it is not quite as good as the c-frame (particularly on thicker skins), but it may have been the particular tool I used.

If you are able to determine that your dimples are well formed using the skin reflection, then riveting technique would be evaluated.

Click to expand...

I have all those tools and getting a full footprint from the dimple.... Rivets look to be properly seated...gauged by overlaying a straightedge or razor blade....I am using the C frame.... First and When able, second is a large hand squeezer last the pneumatic.. The skin is perfectly flat until riveted... When riveted it will draw itself the skin to the structure this is where I believe the slight distortion occurs... Not sure this can be avoided? Without a lot of additional work to understructure?

I would be interested to see pictures of these perfect dimpled, rivet rows... Now that I'm finally building my own airplane I am certainly looking at things a bit different... Maybe over critical.... I can walk outside my hanger and look at Gulfstream's, BBJ's etc. and they certainly aren't to worried about slight distortions from the process....

Thanks for you comment's

Here's a shot of David Howe's Rocket. This plane has the best riveting I've seen thus far. In fact, the whole airplane was so interesting I plumb forgot to ask about his riveting technique - although I did get to see some of his custom frames, including one extremely stout one that used the 6,000 lb. pneumatic squeezer (the common squeezer is only half that).

There's no filling on his wings.



Dave

Back rivetting.

The best way to achieve that flat finish is to back rivet everything you can. I have the offset back rivet set for getting behind the ribs to achieve the best result I can.

Sid Lambert said:

I picked up a set of the Economy dimple dies from ACS for use on my current project. I dimpled my first skin, a horizontal stab skin, and the skin was completely bowed using the c-frame and a deadblow hammer like I have many times before. I pulled out my trusty 10 year old Avery dimple dies and redid the skin. It came out perfect as usual.

So far in my experience these are the do's & don't of dimpling...

Use a c-frame with a deal blow hammer whenever possible.
Use 2 solid blows per dimple. If you can't get a solid hit on it then multiple softer blows is fine.
Never use a framing hammer.
Never let the return spring on the c-frame allow a space between the skin and die before hitting it. I just removed the return spring.
Don't be scared to modify the outside diameter of a die to allow proper fit. It's better to buy another set than put stress on the web-to-flange radius.
Always c-frame dimple tank skins.

Click to expand...

This is great advice, along with Scott's. I always use the c-frame with 2 good blows with the dead blow hammer. I'm not sure you can get as good a dimple with a DRDT, as you can with 2 solid blows with a c frame.
Besides the c frame is a lot quicker in my opinion.

I'm no pro but there always seems to be a slight amount of distortion along the rivet lines. I used a DRDT2 and hand held squeezer both with the hydropneumatic system from Cleaveland Tools for dimpling and am pretty pleased with the results. I also used their tank dies. For riveting I back riveted where possible, used the hydropneumatic squeezer when I could and used a rubber surrounded swivel mushroom set for the rest of the flush riveting.

When I needed a helper for riveting I spent a bit of time with them driving "practice" rivets before we got into the expensive stuff. Where possible I tried to start about the middle of a rivet line, and work towards the free ends of a panel. My thoughts were trying to avoid trapping any sort of bulge in the middle...

As far as speed goes, once I got in the swing of it, I found I could dimple at a rate of about 1 per second with the DRDT2 with the hydropneumatic head.

Here's a few shots of my far from perfect (first time builder) results as a data point... A lot of credit goes to some pretty careful (though inexperienced) helpers...

http://s954.photobucket.com/user/ae...130620_143934_zpse0598488.jpg.html?sort=3&o=0
These were done using a 3/4 thick plate with a male dimple set in a hole. The female in a 6 x 3/4 handset and a 12oz ball peen. So, it's not just the size of the tool. It's also how you use it.

At first I was like "what do dirty ceiling tiles have to do with nice dimples?"

And then I saw the invisible airplane

That is really smoooooooth and flat.

Another variable is the fit of the under lying structure to the skin. Make sure all flanges are perfectly bent so their are parallel to the skin. I found on my RV-8 (early fuselage) that I needed shims in a few places between the bulkhead and the skin to avoid having a small space.

Once you are done with the fuselage riveting, you may find a few places where the skin is very slightly depressed at a rivet. I touched those up using a length of dowel and hammer - I went inside fuselage, put the end of the dowel on the formed rivet head and tapped with a hammer until my outside helper told me the skin at that rivet was perfectly flat.

Kevin Horton said:

Once you are done with the fuselage riveting, you may find a few places where the skin is very slightly depressed at a rivet. I touched those up using a length of dowel and hammer - I went inside fuselage, put the end of the dowel on the formed rivet head and tapped with a hammer until my outside helper told me the skin at that rivet was perfectly flat.

Click to expand...

Take what Kevin has said very seriously. As hard as you try to make sure all the flanges lay perfectly together, you will have some places that will show after riveting. Whether it's an inexperienced bucker/shooter or the flanges it's inevitable I think. I spent quite a few hours inside the fuse lightly tapping them back out flush before sending it to the painter, and still see some places that could have been better.

My $.02 worth.

sum'r flatter'n udders

Ron RV8 said:

I'm no pro .....
Here's a few shots of my far from perfect (first time builder) results as a data point... A lot of credit goes to some pretty careful (though inexperienced) helpers..QUOTE]

Ron, that's a beauty! ....but I thought you said yellow 'n preyple???? looks like you got grape with goldenrod!
oh well, you can sand it off & try again, right?

the riveting looks reeeeeeeeeel nice from here!

( does Mooney time count toward a hi-performance endorsement ....like an ar-vee ate?)

Click to expand...

aerhed said:

http://s954.photobucket.com/user/ae...130620_143934_zpse0598488.jpg.html?sort=3&o=0
These were done using a 3/4 thick plate with a male dimple set in a hole. The female in a 6 x 3/4 handset and a 12oz ball peen. So, it's not just the size of the tool. It's also how you use it.

Click to expand...

This picture looks like it was taken from the best advantage point... You also have process related distortion based on the circus mirror effect as seen by what is reflected in the skin. This is good quality you can see that. Nice work...

I greatly appreciate the reply's.... I have been an AP/IA for 22 years... Typically I hate hearing other technician's state that type of claim because we have all seen AP' s that should have their tool boxes taken away... That credential doesn't mean you can build or rivet.... There's plenty of RV builders that are better than most AP's.. This is my first build and I have been wanting to build an RV forever. I have sheet metal skills, but I must say I'm learning a lot. Tail is basically finished and it looks really good, I know it could be better but things I learned building that tail can not be applied it's done...

I'm going to test the dowel trick and pay more attention to the understructure,, I have also switched to the DRDT-2... The C frame may very we'll produce a crisper dimple but swinging a hammer towards my parts makes me uncomfortable...

One thing I learned early in this build is after looking at production airplanes all of my career,,,, accepting that craftsmanship as a standard is a bad idea and should not be applied to my project as acceptable....

For example I was looking at my friends S 35 Bonanza this morning and honestly Beechcraft should be embarrassed the sheet metal work is terrible especially when compared to some of the RV's that are out there.

The RV community has raised the standard it's cool to become part of this community... Just another reason not to go certified!

My fuse arrives Next week and I can apply these evolving skills and things learned from the VAF group to the next phase,,,

Build on I think is what you guys say, Thanks!