From a user standpoint, it could be caused by dropping tail on the ground when exiting the airplane, having the tail hop and bounce on a rough tarmac or in and out of a hangar with big bumps and concrete cracks when moving it by hand, or hitting the tailwheel frequently on takeoff and/or landing. I also wonder if the tail was bonded with Urelane during assembly. If you're having those problems at the tail, I would also examine the welds surrounding the support tubes at the aft boom tube socket, as well as the motor-mount area thoroughly. I just can't imagine having these kinds of problems with riveted and bonded construction, while treating the airframe with care. This discussion has prompted me to examine the vertical stab and aft frame welds closely on our 3300-powered 2S while it is here in our shop, but it all looks just like it did when it rolled out 7-1/2 years ago.
--Kimberly
----- Original Message -----
From: titjab
To: Titanaircraft@yahoogroups.com
Sent: Saturday, November 28, 2009 8:54 AM
Subject: [Titanaircraft] Re: Tail cracks
Another issue found. I looked at mine today but did not find any cracks, however I did find another issue. The rivit line on the port side that attaches the vertical strake to the vertical stabilizer were becoming loose. The paint was cracking from the rivit to the aluminum lip, and also cracking paint around the rivit. There was the typical gray streaks from spinning rivits. The paint line between the two attached skins was also cracked looking like someone took a thin line marker and drew a line along the seem of the two skins. The first 5 inches of rivits from the boom tube and upward were all fine, the rest from that point to the top of the vertical strake were loose. Upon drilling out the loose rivits it was found that section was not glued, the glue was applied to adhere the two skins from the boom tube to 5" up the vertical skins. With the loose rivits removed I could push on the vertical stabilizer skin and it would seperate from the vertical strake skin. I have some glue coming and will glue and rivit this section. Not sure what the build manual says about gluing these to skins, but something to check periodically. The starboard side shows no issues and the paint is still like new.
--- In Titanaircraft@yahoogroups.com, "fleepdx" <bobcoombs@...> wrote:
>
> Hi,
> Haven't been here for a week. I see that there are a few people who have asked about the cracks. Most unfortunately I didn't get any pictures of them before doing a repair. This would have been an obvious thing to do. The description I made of their location is pretty much accurate. They were irregular, shaped like lightening bolts. The metal immediately next to them was elevated which might suggest the problem is one of compression rather than tension.
> My reasoning on the repair was to increase the amount of metal in the area, at least doubling and even tripling the strength. I've learned in the past that a repair can be stronger than the original componant and that's what I'm shooting for. Using adhesive would bond all three layers together and would presumably prevent any recurrance.
> The hangar owner where I'm at once had a Thundergull that had the rivets break in the same location. The tails of these two planes (as far as I know anyway) are identical or nearly so. He replaced the rivets with Cherrymax rivets which apparently give much greater shear strength. I intend to do this as well thinking that the increased strength of the sheet metal I now have will move the stresses elsewhere, ie. the rivets.
> The original construction had the sheet metal glued to the boom tube and I will do this as well.
> I continue to think this has happened because of my regular use of grass strips where it would seem that the lateral shaking/jarring of the tail section would be much sharper than that encountered in the air. Comments from those who also have found cracks??
> Bob
>
> > > I recently discovered 2 cracks in the vertical stabilizer on my Tornado II. Each is at the lower aft corner where the sheet metal is cut at a 120 degree angle. The cracks are about 1-2". I have repaired them with a double layer of .025 aluminum, one inside and one out, and have fixed them with epoxy. It seems this would be sturdy enough to prevent the cracks from recurring. The metal of the tail seems to be .016" or perhaps .020".
> > >
> > > My big concern is why these might have happened in the first place. I've followed this group through from the first message ever posted and don't recall anyone else mentioning this kind of problem so I'm inviting any input there might be about this.
> > >
> > > Construction of the kit was supervised and assisted by Mike and Jeromy in Richland WA so it was probably done right. About the only thing I can think of is that I operate mainly out of a slightly rough grass strip and perhaps the jarring on the ground is causing the cracks. This seems kind of unlikely but it's the only thing that comes to mind.
> > >
> > > Thanks for any input, Bob Coombs
>
[Non-text portions of this message have been removed]
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