Cracks in fuselage.

[Charles Carter]

Should I do something about the cracks in the fuselage sides in front of the leading edge of the wing and behind the trailing edge of the wing? What I have done is applied some thin CA into the cracks.

Charles Carter   

[Tim Wescott]

That depends on how big they are, whether they're just in the paint or if they extend into the wood, and whether they're there from crash damage or fatigue.

For the most part, putting CA in the cracks will probably slow down the process but not stop it.

There's probably fixes that you could do, but I'd be tempted to just build another plane, and maybe try to figure out why the cracks so you can keep it from happening on the new one.

[Dave_Trible]

Stress cracks were common fare in the old days before we used epoxy for wing/fuse joints.  Adding a doubler on the inside with epoxy may be needed to fix yours.  These days I use epoxy on the inside and cement with carbon tissue outside to help hold the fillets down.  Dope will pull up right off epoxy in this joint.  Fixing these cracks are tough once oil has gotten in.  Cya is about as good as anything because it can penetrate and encapsulate the oil better than most anything else.

Dave

[Matt Colan]

I had an issue with stress cracks a few years ago with my Trivial Pursuit. Here is the thread detailing what was going on and how I went to fix it. There's a lot of good info in this thread:

http://stunthanger.com/smf/index.php/topic,22546.0.html

[RknRusty]

My Sterling Yak-9, built last winter is doing the same thing. I think the epoxy laminated fuse is its saviour so far, but I'm afraid it's facing early retirement. I've been blaming the hairline fractures on the Fox 35 and filling them with CA. One good bonk and it might turn into a hundred piece puzzle.
Rusty

[Bill Little]

Hi Charles,

Built up fuselage or profile?  What engine?  What type of fillets did you use?

BIG Bear
RNMM/AMM

[Bill Little]

My Sterling Yak-9, built last winter is doing the same thing. I think the epoxy laminated fuse is its saviour so far, but I'm afraid it's facing early retirement. I've been blaming the hairline fractures on the Fox 35 and filling them with CA. One good bonk and it might turn into a hundred piece puzzle.
Rusty

Hi Rusty,

99.9% of the time, cracks like those are not structural on a profile like the Yak-9.  You can fly for years with them.  Filling them with CA is a good idea.  What type of fillet did you use?


BIG Bear
RNMM/AMM

[RknRusty]

Hi Rusty,

99.9% of the time, cracks like those are not structural on a profile like the Yak-9.  You can fly for years with them.  Filling them with CA is a good idea.  What type of fillet did you use?


BIG Bear
RNMM/AMM

Hi Bill, Merry Christmas.
I made the filets with a thick mix of glass microballoons and 60 minute epoxy. There ain't much holding that wing on from the bottom, so I glued an inch wide strip of basswood from under the air scoop and jammed it in between the wing and fuse at the front.
Rusty

[kenneth cook]

             A very common problem with the Yak due to the fuse just sitting on top of the wing. The only portion that wraps over the leading edge is only about 3/4" long. Just keep gluing it. I've ground out the fillet and stuffed in some milled fiberglass with heated epoxy with good results. Another option is to stake the small piece that wraps over the leading edge. From the bottom up drill a hole for a 1/8" dowel about 2" long and insert it through the fuse and through the leading edge back into the fuse. Ken

[Howard Rush]

The title "root folder" raises one's eyebrows.

[Bill Little]

Slight cracks were the norm for me when I was younger using a Fox .35 in a profile.

BIG Bear
RNMM/AMM

[Keith Miller]

Hi Charles!
Y'know that white Tutor II that I have?  Its front end has had many cracks filled just the way you describe and she's holding together really well!  It looks like crap, but you've seen how it's flown

[Sean McEntee]

Hi Bill, Merry Christmas.
I made the filets with a thick mix of glass microballoons and 60 minute epoxy. There ain't much holding that wing on from the bottom, so I glued an inch wide strip of basswood from under the air scoop and jammed it in between the wing and fuse at the front.
Rusty

Rusty thanks for sharing.  Im almost to final assembily on my T-6, and it too has almost no support under the wing.  Thanks for the info

[Carl Cisneros]

Rusty and Ken
Iwill incorporate both of your suggestions on my Yak when I start building it in abou ta month.

[RknRusty]

Rusty and Ken
I will incorporate both of your suggestions on my Yak when I start building it in about a month.

Carl, when you do get it on the table, if you start a build thread we can talk about it without hijacking the original topic. I know of several things that might be of interest to you. Actually I learned most of them from Ken. The Sterling Yak and its twin brother F-51 Mustang have some important similarities
Rusty