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I was playing around with final fitting of the elevator the other night and ah man two of my hinges are about 1/8 inch off, I can push them in and get the pin through but it binds, cant have that, anybody else ever over shrink and run into this, did you make off set bushings or peel the fabric off and start over,
It is very easy to overshrink the elevator if you don't put stiffening "T" pieces on the wood ribs. The manual doesn't specifically say to do this but it is quite necessary. If you don't, the shrink process will pull in the steel tube frame and force the ribs into an "S" shape. Even with the stiffening pieces in place you must be very cautious during shrinking-keep checking with a straight edge on the steel tubes. If they start to bow in, stop shrinking. This is the only area on the whole plane where I had to watch and not shrink too much.
I don't understand this. My Model IV manual says to shrink to 300 degrees max temp. I know Polyfiber says 350, but I would think that the airframe designers knew the pitfalls. I did a quick calculation and my closest flying buddies all with Model IVs shrunk per the manual have in excess of 7000 hours with never any fabric issues. Sorry, but I continually wonder why the tendency to apply "modern" techniques to the classic designs. This thought also goes to the tendency to now use the 2.79 oz. light weight certified fabric rather than the lighter weight 1.87 oz. uncertified fabric that came with the original kits. Oh, now I remember. One buddy says the heavier certified fabric resists cat scratches better. But seriously, with the traditional Kitfox communities - e-mail and forum - if there were problems with the original design, we would most certainly be aware of them.Quote:
Originally Posted by jiott
Hmmm, is it possible a Model I is different? Thinner tubing maybe? That's what he's building.Quote:
I don't understand this. My Model IV manual says to shrink to 300 degrees max temp. I know Polyfiber says 350, but I would think that the airframe designers knew the pitfalls. I did a quick calculation and my closest flying buddies all with Model IVs shrunk per the manual have in excess of 7000 hours with never any fabric issues.
Didn't see any mention from either TJay or Jim of overtemping either - just over shrinkage Perhaps that's an assumption?
Either way mistakes get made - I don't think any of us are perfect.
TJay, if you can't get free movement - I'd recover. FWIW
I did over shrink it a bit, I took it to 275 degrees with 2.7oz fabric, but when I was studying it for a while I noticed the biggest problem was the two hinges were not welded on properly they were at a slight angle and I did not notice it during building because I did not install the plastic bushings till final assembly, that's when the binding started, so I cut the hinges off last night and re welded them where they were meant to be, I pulled a string line through all the holes and got a perfect strait line and now I have a very smooth travailing elevator and I like it, put the landing gear on this morning here is a pic,
Oh and my building technicians are quite good but I am far from perfect and learn from my mistakes, maybe I should spend less time building and more time on this forum huh.