Warbird Information Exchange

Here is a brief update on the recovering of the B-24's rudders and elevators over in the High Sky Wing hangar. Below, Chris Trobridge applies tape over the rivet heads under the supervision of Lance Sommers, who is an A&P and is training other Wing members in the art of fabric work. Chris lives in Lubbock but comes down some weekends to help out with Wing chores.

While Chris works on one rudder, Bill Coombes has glued fabric onto part of the other B-24 rudder and is now using an iron to carefully shrink the fabric.

A close up of Bill and the iron with Lance advising on the proper techniques. Bill has experience at this with large R/C aircraft but says this is a bit larger scale than he is used to.

Hopefully work will continue over the next few days and we can deliver the rudders and elevators to Gary soon. Anyone who is in the Midland area and wants to help, let us know.

Randy

Gary, don't you have the part number for those figure eight rivets? Looking good!

Randy,

In my experience in building RC aircraft, the iron is only used to seal the edges of the covering and a heat gun is used to shrink it. Wouldn't it be easier in this instance too to use a heat gun?

I'll answer this one for Randy. It is crucial for the heat range to be uniform when shrinking the fabric, particularly initially. You want the fabric to slowly be shrunk, a little bit at a time, so that it lays down properly and doesn't bend or warp any of the underlying structure, among other things. The iron is the only way to do this accurately. We (or they in this case) actually got one of those fancy little laser temperature thingys and used it to calibrate the iron. They put a mark at 225, 250, & 275 degrees (I may be a touch off on those figures, as I don't have the book in front of me at the present). You shrink the fabric in stages with the iron, NOT all at once with a heat gun. Sure, it could be done, but it's going to look like crap and it'll surely have some areas that will be too loose or too tight.

I'm nowhere close to being a fabric covering expert, so I'm sure there are better ways to answer your question, but I hope that helps.

Gary

We have Poterfield hanging from the rafters of our hangar that the fuselage tubular is all tweaked because someone used a heat gun to shrink the fabric. Poor thing is destined to hang from the rafters.

Thanks for the info guys, definately makes sense. I know when shrinking the fabric on our little RC planes you can induce a warp in the wing if done improperly. I didn't think that would be the case in a larger metal structure, but it seems that the problems we experience scale up to the full size as well.

A heat gun gives you a diffrent temperature depending on how close you are to the fabric. An iron gives you a constant temperature across it's surface. The important part with the iron is to calibrate it so you know exactly what temperature you have. Too hot and she melts right through the fabric!

Another point to add to that is that you need to keep the iron moving over the large surfaces. Again, I don't have the book in front of me, but I think it's like a foot every second, or something like that.

Gary

Oh, and this has nothing to do with our current topic, but I just remembered about an e-mail I got a couple of days ago from our Tour Director. Just thought some of y'all might be interested in reading the news.......


"We're in!! AeroShell circle again at Oshkosh."



Gary

That is so awsome. I wil be there buddy!

_________________
Chris Henry
EAA Aviation Museum Manager

Gary...you just made my day this morning! My two boys and I can't wait to see her in person. Will you be coming along?

John

Unlikely. I don't personally have much desire to go to Oshkosh or Sun-N-Fun again. Nothing against those who do like to go, it's just not my thing. Too many people for my liking, not to mention that I'm a nervous wreck when that many folks are around the airplane. I just can't watch 'em all and it never fails that I catch someone doing something stupid and I end up saying something ugly to them. I'm not really a good spokesperson for the CAF in those cases.

The Air Races are more to my liking, because even though folks can get right up close to your airplanes and see you working, they can't crawl all over them and take home "souvineers" from the airplane that you work countless hours on just so they can see it.

Make sense?

So, unless I'm required to go to Oshkosh by my employer, I doubt seriously that I'll be there. Besides, there's a line a mile long from our Squadron members who want that tour stop. I don't want to take up space that they could use.

Gary

Gary - thanks for answering the technical part of the iron vs. heat gun, since I'm only reporting and not the expert. We are very fortunate that Lance has a good bit of fabric experience, so we are doing it how he and Gary want it done.

FYI, we had quite a snow storm, as Gary noted, here in Midland yesterday. As we were winding down in our Wing hangar, we all had to laugh at the sight of a snow plow clearing the ILS runway for a Southwest flight to land - in Midland - in April - amazing!

Randy

I totally understand Gary! I'm one that hates crowds myself...of course airshows are always the exception. I was just hoping I could finally meet the "legend" in person.

No need to worry though...if I see anybody doing something stupid while touring the old bird I'll be sure to lay into them for you.

John

What is this?..............




That is a bad way to start the day. It's a big pile of aluminum shavings from me drilling out some freshly installed rivets that Andy and I banged in the tail gunner's section a few weeks back. As y'all probably remember, I have been making forward progress on the tail gunner's doors, but have been running into some pretty significant hurdles along the way. The door prototype has been working surprisingly well on the tracks that I made, but horribly on the factory tracks. It looked and sounded as if the corrugated skin of the prototype was hitting the rivet heads on the side of the fuselage. I tried several different versions of spacers and such to go under the roller assemblies to try to aleviate the problem, but nothing was working.

So this morning, I took a big step backwards. I decided to remove the aft section of skin that we had just recently secured in place. You see, the factory kind of screwed me when they took the old tailgunner's position out, because they apparently screwed up the original 1/8th inch rivet holes and put these big, honkin' 3/16 inch rivets in their place. What that did was made the new rivet heads so large that they were interfering with my new doors (or so I thought). So the idea was to remove the old skin completely and replace it with a new one, along with making doublers on the inside to accept the old size 1/8th inch rivets. The first step was to get the rivets drilled out.........




Cool action shot (notice the chips flying ).......




And once the rivets were all out, the pieces were removed........






Now once the skins were removed, I tried to slide the prototype door in the track. If my theory was correct about the big rivets, then the door should've slid with no interference whatsoever..........it didn't. The door still had interference. However, as it turns out, the removal of the skins wasn't a fruitless effort after all. What it did was enable me to see what the heck was going on in the factory tracks that was causing me all of this grief and loss of sleep. After some close inspection, I noticed that when the factory reinstalled the tailgunner's door tracks (why, I don't know, since they just covered them back up....must've been a strength issue), they used pan head rivets to hold the tracks in place, rather than flush rivets. So what was happening was that my rollers were just barely striking the heads of the rivets as they went by, which was making it feel and sound as if my corrugated skin was hitting the rivets on the side.

This discovery was the breakthrough I needed! Since there is no way in heck I'd ever be able to successfully drill out the pan head rivets in those tracks and replace them with flush ones, I simply just modified my rollers to make them slightly thinner. This relatively simple modification made all the difference in the world. The prototype door slid easily now, almost like it was.......well, almost like it was on rails.

So the next step was to graduate from the prototype door and muster up the courage to actually build the first real door. It's quite a bit longer than the prototype and also has the outer skin attached to it, so I must admit that I was a bit nervous about how it would work. Well, it didn't take too long to get the first door built, although there are still two smaller sections that I've yet to fabricate for each end. But for now, the first section is working well. Not as good as the smaller prototype, as it still requires a bit more effort to slide the door back and forth, but it's still easily done with only one hand.........






There is a slight bind in the door when it transitions around the little "S" curved portion of my tracks. I can only assume (and hope) that this slight binding can be remedied by some fine tuning and lubrication later on down the road. But for now, I'm pretty happy with the results. Wow, did I just say I was pretty happy??? That hasn't happened much lately, but it's nice to have a stroke of good luck for a change. Hopefully, the luck will stick around, as I'm officially down to 5 weeks before the unveiling......with about 3 months of work to get done.

I've decided to go ahead and leave on a good note today, so I'll check in with y'all tomorrow.

Gary