TopCap Fish Dance
 

I took her up, I leveled her off, I was at half throttle and then...
THE CRAZY FISH DANCE!!!!
I've seen flutter and brother this was it but I was confused because I was just putting along. I get her landed and didn't see anything wrong and then I notice that the fuse was cracked right behind the wing. It seemed to be on the same line as the exits on the pull-pull tubes. If I handed you the plane you might not notice. I never even crashed her.
My plan is to pull the covering off in front of and behind the crack on both sides. Then cut myself some wood to expoxy over the weak area. I think before I put on the scabs I will try and CA the fuse as straight as I can. That is the only thing that I'm concerned about. It will drive me crazy if that fuse is a little ascew. I'll do my best. Any suggestions are welcomed.
BH

TopCap Fish Dance
 

Sounds good to me. a little 1/32 ply after ca'ing back together should do fine. Keep an eye on those pull pull cables, If they get a little loose it's flutter city. Try to use a straight edge against the fuse when you glue it back together

TopCap Fish Dance
 

I cut a couple 1/8 ply splints and epoxied and clamped them until dry and it is way better, I think it must have been flexing before it broke. It is a lot stiffer and I don't think it added enough weight to matter, at least I can't tell any difference.

TopCap Fish Dance
 

Yeah, your avatar (flipper), that is what my plane was doing only the other way.
Did you just make holes for the pull-pull wires to go through? I figure it won't be that big a deal. I'm going to cover it in checks so it should look cool to boot.

TopCap Fish Dance
 

you can also put a layer of carbonfiber tape over the crack (reglued) part for strenght. Keeps it light.
Please post pics once you apply the checkers to the fuse. We all need to see results. :D

Top Cap
 

Just behind the wing is a week spot. Runnig strips of CF down the sides is a big help.

TopCap Fish Dance
 

That is were mine broke and when I pulled the fuse apart the wood was very weak.

TopCap Fish Dance
 

When I build my next one I will just put some scabs on top of each side from the git go.

TopCap Fish Dance
 

Great plane, but that is the weak spot.
Mine cracked in the same place after a rough landing.
Others have the same complaint. If i get another, i'l definately add some ply right there.

TopCap Fish Dance
 

Thanks for the heads up.

I've got one in the box. heading to the bench after the next project (for someone other than me).

I'll add this change.

TopCap Fish Dance
 

hmmmm, guess i got a good one, bounced mine hard a few times
(hard enuff to straiten out the mains) and no damage to the structure. I never have had a flutter prob, but I never run over 1/2 throttle unless Im goin strait up/
John

Fish plates
 

The correct term for those reinforcing pieces placed over the cracked area is... fish plates, although I think a true fish plate is attached with bolts. Guaranteed to fix a fish dance problem. Honest.

TopCap Fish Dance
 

My prop and motor don't really allow for haulin' ***** so I don't think that was it. Could have been a bounce.

TopCap Fish Dance
 

What about adding a flat carbon fiber strip (it is refered to as a flat carbon rod, I just have a problem calling something rectangular a "rod"??) to the area which needs reinforcing??? You can get several different sizes, and they add little weight.

Or would ply be the best way to reinforce the area??? :confused:

Fuse repair
 

Tyvek envelopes are very light and almost imposible to tear. You could just glue a sheet of Tyvek on each side of the fuse over the break. I would use at least a 10" long piece, centered on the wing hing line location. You could then re-cover right over the Tyvek, since it is paper thin. You could probably use most any glue to attach the Tyvek. You can get large Tyvek envelopes at the post office for free. I think the express mail overseas envelopes are Tyvek.

TopCap Fish Dance
 

Pardon my ignorance, but which envelopes at the Post Office are "Tyvek"????? :confused: Are we talking the "manila" envelopes or what?

I live in the middle of the sticks. I'm afraid if I go into the local Post Office and ask for a "Tyvek" envelope they will probably look at me like I have "snakes crawling out of my head". Then before I can get home, the local sheriff will be at my house to take me to the "funny farm". :p

Thanks. :)

Tyvek
 

Tyvek is easy to identify. The material looks kind of like cloth with a kind of weave in it. It is very thin, light and hard to tear. I would be surprised if the post office guys didn't know what Tyvek is. Here is a web page on Tyvek:

http://www.tyvek.com/na/envelopes/english/index2.html

A guy in my club also uses it to sheet foam wings. He just glues it to the foam with aliphatic glue (elmers, tight bond, etc.) it can be painted and is fuel proof.

TopCap Fish Dance
 

rcman,

Thanks.

I know exactly which envelopes you are talking about.

TopCap Fish Dance
 

Mine was covered with solartex or colortex, same thing different name and it is real tough, tougher than tyvek IMHO and it broke under the covering. The covering kept it together but you could move it from side to side. I will put plywood on my next ones from the get go. Jeff

Tex's
 

All the various "tex" (colortex, solartex, etc.) coverings have a lot of stretch, and would therefore not be a good choice to increase structural rigidity.

TopCap Fish Dance
 

I'm going with wood and I went ahead and went with some thicker wood. I don't mind adding some weight if it keeps my fuse from cracking into again. It should be super strong and if I do it right it should look cool too. Think of them as power bulges.

TopCap Fish Dance
 

keep us updated with pics !

Fuse strength.
 

:p Hey guys , been into the FF and Profiles for many yrs, they all break behind the wing at some time or other. A real easy way to make em strong and still flexible is to just cut about 1/4 off the bottom of the fuse and glue in a carbon or glass 1/4 inch tube the whole length of the bottom and secure it between the side doublers up front . This will only add a tad of weight and still be very flxible - but add a ton of strength and keep em from breaking behind the wing and at the tail section. Also is a good strong point to attach a tail shid or wheel. Have FUN !! Rod :idea:

TopCap Fish Dance
 

Hey Billy, mine did the extact same thing, on the first flight. Thought I was going ot loose her, but she came down in one piece. Filled a syringe up with epoxy, shoved it through the balsa sheet in the broken area and filled her up. A nice piece of clear packing tape went over where the covering split, and back to the air. Holds up to some seriously stressful KE loops, and hasn't been a problem since.

TopCap Fish Dance
 

I guess my job was overkill but I'll never worry about it cracking again. I'll put a pic up on Tues.