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  #341  
Old 11-03-2017, 10:36 PM
David Paule David Paule is offline
 
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Location: Boulder, CO
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Bread's good, and compared to an airplane, it's almost like instant gratification.

I made a loaf of sourdough rye a couple days ago - good stuff. Funny that you made a rye loaf too.

The bonding is not to the plans. The RV-3B is a riveted airplane, and riveted only. My mentor is out of state and I went for a visit and was struck by the quality of the rivet lines, which were superior to those on most of the non-bonded airplanes I'd seen. He gave me his gluing process and I started gluing things together prior to riveting. At first I merely used it as a holding fixture, but as I got more confidence with it, I decided to try that aft-most belly skin. That went relatively well and I bonded and riveted some flanges and stiffeners onto this skin.

They came out the way I'd hoped and with considerable trepidation, I decided to go ahead and attempt to bond this skin on.

The overall bonding process takes a fair bit of additional time but it seems to me to be worth it. The initial look of this skin was favorable so I am currently planning to bond the long tailcone side skins on too. After that there's only the cockpit area skins and I'll decide about them when I get to them.

I did not bond the wing, tail or control surface skins. But if I were starting afresh, I believe that I would, especially as the difference is so clearly discernable. Worth noting is that I don't really need this airplane and have no plans to use it as much as I should. I'm mostly interested in it as a construction project and to keep from getting bored or intellectually lazy, and for that purpose, bonding is excellent. So for me, the bonding fits well into the project.

Would I recommend this to everyone? No, of course not. If you want a flying airplane in a realistic amount of time, skip this idea. The airplanes are entirely satisfactory if they are built to the plans.

Am I trying for a Lindy? Absolutely not. In fact, I have no plans to ever again go to Oshkosh at all. In any case, the wings are not nearly show quality. All I'm trying to do is indulge myself.

In that respect it's a bit like baking sourdough bread. It takes longer for somewhat better results, but it's not necessary.

Dave
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  #342  
Old 11-04-2017, 07:43 AM
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ColoCardinal ColoCardinal is offline
 
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Location: Morrison, CO
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Truth be told, almost every one of the planes being built is for self-indulgence. It's great that you take the time to share your experience with everyone else.

I can see several advantages to the bonding process. Wondering if you've considered some of the newer adhesives developed for the automotive industry. Most of the auto manufacturers are using adhesives in areas formerly welded; they're that good. It's allowed them to combine steel and aluminum in areas that would have been impossible to do before. Even the repair shops are replacing welds with glue.

Bought an ebook on fermentation a couple weeks back. Sourdough was one of the things that I've decided to try. Did it many years ago but failed to use it enough to keep it alive. Didn't have the discipline to devote to it.

Thanks again for your posts.
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flying by: I give up on predicting!
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  #343  
Old 11-04-2017, 12:50 PM
David Paule David Paule is offline
 
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Location: Boulder, CO
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I'm trying not to reinvent things here. I'm using one of the two epoxies that are recommended by my mentor, who has tested it. The other is 3M's 2216. Another friend, in the marine industry, has also recommended G/flex for aluminum bonding.

While there are many glues, I don't know what the automotive industry uses or even what the glue companies recommend.

Dave
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  #344  
Old 11-06-2017, 07:15 AM
wilddog wilddog is offline
 
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David,
Question, if you should ever have to replace a glued and riveted skin, how hard would it be to remove with the glue holding it?
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  #345  
Old 11-06-2017, 10:55 AM
David Paule David Paule is offline
 
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Good question!

Probably quite difficult. Heat might help, I don't know. Or my glue prep might prove insufficient and the pieces might pop apart. I have no idea and repairability isn't one of my goals.

If the plane should need so much rebuilding that fuselage skins need to be replaced, I'll either hire a pro or part out the plane. But note that I'd take one of these approaches even if it wasn't bonded; I have no interest in that level of effort.

Dave
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  #346  
Old 11-06-2017, 11:56 AM
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dwrichey dwrichey is offline
 
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I truly do not wish to rain on anyone's parade, but I wonder if allowing the adhesive to cure before the parts are riveted together would prevent the parts from properly "nesting" together. I assume the force exerted by the clecoe's is not nearly as great as those exerted by driven rivets, therefore leaving a thin layer of adhesive that over time could breakdown?
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  #347  
Old 11-06-2017, 02:02 PM
David Paule David Paule is offline
 
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Folks, if you spot a potential issue with this or any other aspect of the construction, please let me know. I'm only human and I do goof sometimes.

Thanks for commenting.

The parts are dry-fitted together before gluing to verify a close-fit joint; and the edges of the joints are not sealed to allow excess epoxy thereby come out. Which it does, and needs to be removed.

Post-cure inspection of assemblies made so far does not indicate that there's a problem of this nature.

Dave

Last edited by David Paule : 11-06-2017 at 02:04 PM.
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  #348  
Old 11-16-2017, 03:04 PM
David Paule David Paule is offline
 
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Before I could rivet the long belly skin, the side skins need to go on. The bottom of the belly skin was already riveted to the various stiffeners and bulkhead flanges, so the only remaining parts were at the ends and the bulkhead shoulders, and they can wait till I do the lower longeron and bulkhead riveting for the side skins.

The tape bumps roughly in the middle are folded-over tape, giving me aen easy place to grab on to for removing the tape. I now like 3M's model 33 electrical tape. I've tried blue painter's tape, which is harder to remove, and green painter's tape, which is fine if there's a wider area to tape but is slightly harder to remove. However the green painter's tape conforms down into the dimples better.

One of the steps to this gluing is to mask off the areas adjacent to where the glue goes and then do a dry fit check to verify that the tape is in the right place. At the upper left, you can see that I needed to adjust this a bit. The tape is slightly apart from the joint so that I can form the glue squeeze-out into a fillet there.



After a couple of intense days the left side skin was ready to install. I gathered up some friends and we began. About two hours later, we took these photos.

This is Dallice Tylee to the left and Dave Dooley to the right. They're both pilots; Dallice flies a Bonanza and Dave built a Xenos motorglider and also has a Swift.



And here's me. I'm pretty happy - we didn't screw it up.



Don't know if you noticed but we were all wearing gray shirts and jeans, completely unplanned. It wasn't a uniform, this was junk clothing that we could get glue on. As it turned out, we didn't - we used up a bunch of blue gloves, though.

If you're using epoxy and need to remove some from something, ordinary cheap vinegar works fine if the glue hasn't set up. Wash in vinegar, wash in soap and water, dry, done.

The skin has the exoskeleton on. This acts something like a mold, ensuring a smooth, fair skin. As soon as the glue is thoroughly cured, that comes off. Here's the skin with the exoskeleton on.



And again with the exoskeleton removed. There's still considerable clean-up to do at this point.



The photos can also be found here, here, here, here, and here.

Dave
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  #349  
Old 12-04-2017, 11:55 AM
David Paule David Paule is offline
 
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After the gluing came the clean-up, and then the usual bunch of small things before anything major ever happens. Yesterday, though, Larry Larson came down from Estes Park, down to the valley, to help me rivet. You folks know him as Wirejock. His RV-7 is much higher build quality than my little RV-3B, so I was glad to have him over today.

We riveted the left side to the frame. We got all but the top longeron, of course, and we even managed to include the bulkhead shoulder rivets in between the lower longeron and those replacement bulkhead flanges that you saw earlier. So it was a good day.

He even brought treats. He bakes bread and brought me some really delicious sourdough he'd made. Yummy!

When we weren't talking about bread, he riveted and I bucked.



Some times the fuselage was tight and there wasn't much distance between the fuselage and the jig's side, and I had to work through the still-open right hand side. I suppose that I was doing it by feel since my eyes were wide shut here. It'll get harder when the right hand skin is on.



There aren't any photos showing me wholly inside the fuselage yet, but the various aches and sore spots assure me that I was really there.

We started with me inside the fuselage using a back-rivet set, and Larry outside using a fat back-riveting bucking bar. That went fine for a while and then I ruined several rivets in a row, and switched so that Larry used a rivet set outside while I bucked inside. These generally gave better shop heads. The factory heads outside were uniformly good, but of course the skin had been glued on so that its position was fixed. If you're gluing the skin, it doesn't matter which you use - use whatever technique works best for you. If you're not gluing, my experience yesterday doesn't apply.

If these photos ever disappear, they might be available here or here.

Dave
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  #350  
Old 12-04-2017, 12:14 PM
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wirejock wirejock is offline
 
Join Date: Oct 2005
Location: Estes Park, CO
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You're too kind and too critical of your build. It's a beautiful 3B.
I recommend everyone spend some time helping another. It is so much fun and a great way to practice perishable riveting skills. In my case it was an opportunity to give back some of what my Mentor, Dave, is so graciously given me. He even made an awesome sourdough rye for us to bring back home.
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RV-7A #73391, N511RV reserved (1,800+ hours)
HS SB, empennage, tanks, wings, fuse, working finishing kit
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I cannot be, nor will I be, held responsible if you try to do the same things I do and it does not work and/or causes you loss, injury, or even death in the process.
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