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

[jj_jetmech]

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

[TS Flightlines]

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

[rvbuilder2002]

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.

[Sid Lambert]

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.

[jj_jetmech]

Originally Posted by rvbuilder2002

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 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

[David Paule]

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

[WAM120RV]

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.

[jthocker]

Originally Posted by Sid Lambert

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.

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.

[Ron RV8]

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...

[aerhed]

http://s954.photobucket.com/user/aer...tml?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.