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evad

smashed my typhoon help and ideas needed

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bogbrush

I decided id make a long (ish) carbon splint using some plastic tube I had lying around in the shed,I cut it down, and then cut long-ways, so it' can be fitted snugly inside the fuselage.

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bogbrush

the tube is fitted inside and when I was happy with the fit I pulled the two fuselage halves apart a little bit (2 inches) and wrapped it with tape to hold it in that shape.

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bogbrush

onse secured in the required shape, the whole tube was then removed and wrapped in tape.- the lip below the overlap was "packed out" with more tape (logways) and then the whole tube was test fitted again, then pulled out and wrapped with a release agent backed tape. (old VHS tape does the same job).

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bogbrush

Once covered in release tape, I then laid out some carbon cloth on a sheet of baking parchment, "just" wetit with epoxy, this was then wrapped around the tube, (with some overlap to double up) and left to dry.

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bogbrush

once dry: The fiddly bit: to remove the carbon tube from the former its wrapped around: pulloed out the ends of the release tape on either end of the tube, then using needle nosed pliers (leatherman), pulled the inside lipped part of the plastic tube round in a corkscrew motion to rotate it, and so make it a smaller diameter, pulling it away from the carbon fibre, (i intentially used el-cheepo white insulation tape that isnt very sticky to the plastic).

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bogbrush

then a test fit, needed only a tiny bit of fettling,

 

the next step will be to replace or repair the broken pushrods, (a trip to the shop), then epoxy in one end of the carbon tube, then when set epoxy the the other, cyano around the break, grind back around the break, and wrap with a 2 inch wide strip of carbon cloth and then a wider one, but adjusted to fit around the trailing edge and wing root profile.

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evad

looking good , i did think about making a tapered tube to go inside , but couldnt figure out how to do it , please keep the posts coming ,  looking forward to see how its done properly

 

dave  

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bogbrush

here's the holes in the carbon from manufacture. :o

 

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bogbrush

looking good , i did think about making a tapered tube to go inside , but couldnt figure out how to do it , please keep the posts coming ,  looking forward to see how its done properly

 

dave  

err, not sure id call it "properly", there's no absolute way to this stuff, but thanks, in flattered ! :D, - (was flying the unbroken fuselage whilst the resin was curing off) -  isnt this a fantastic hobby: you can be mending a model and flying one, at the same time !

 

the tube used was from a plastic borehole bailer, quite stiff, but I guess any stiff plastic thats round might do, As i did it, I thought you might even be able to do it if you double up on an old lemonade bottle.

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bogbrush

once the two halves are glassed in, the break will be fairly neat and be ready for grinding and wrapping:

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evad

its already looking like a neat repair , are you going to try and replace the pushrods without cutting into the tail ?

 

 

dave 

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bogbrush

its already looking like a neat repair , are you going to try and replace the pushrods without cutting into the tail ?

 

 

dave 

Havent quite decided on either 2 brand new pushrods or not, but probably ill just cut the broken ends off neatly with a disc cutter (dremmel), then epoxy into the hole in the existing pushrods a 6 inch length of small diamater solid carbon rod, leaving 3 inches extending out, then when cured, epoxy on a new bit of rod and spiral wrap the break with some spread tow carbon fibre.

 

I have been toying with chopping into the tail, because on this fuselage there was slop in the bellcrank (from new) much worse than the fusealge that replaced it - looking at the model nose on, you could move the tips of the elevator up and down more than I was happy with. Never seemed a problem in flight, but I did wonder if i'd get high speed flutter if i ever d/s'd it.

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bogbrush

decided to replace pushrods not mend them. less faff.

 

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bogbrush

2 new push rods: 4mm with 2mm internal diamater. 1m long. 2mm metal threaded rod grooved and epoxied into the ends then left to cure.

next: I unscrewed the broken elevator pushrod and removed it from the fuselage. Id already taken off the rudder's pushrod.

 

the tricky bit: reconnecting the new elevator pushrod:

Evad spent a while with his back on the floor of his living room trying to make pushrod meet clevis, I tried that method but had no sucess and got tired arms and a stiff neck. I decided to invert the Evad principle and let gravity do the work:

The new carbon rod was plunged into a lump of polystyrene that's sat on the floor, the threaded end of the pushrod pointing up to the sky: the broken tail section of the fusealge is then slid down over it and the threaded end can be aligned with the clevis on the bellcrank inside the fuselage by peering downwards in through the hole for the rudder pushrod. (do this outside on a bright day) I got it on the second attempt  (on the first attempt pushrod and clevis met, but i rotated the pushrod the wrong direction whilst looking down the fuselage to the floor (I should have rotated the pushrod R to L).

then attached the rudder clevis to the new rudder pushrod, slid the non- clevis end in to the fuselage from the tail end, and when the clevis met the rudder horn: I connected it.

 

Edited by clumpflier
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bogbrush

Capture3.JPG

Capture2.JPG

Capture1.JPG

Edited by clumpflier

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bogbrush

magnetising the metal thread might help with pushrod-clevis alignment too (stroke it with a strong magnet in one direction about 300 times).

Edited by clumpflier

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bogbrush

I should also mention that to keep the clevis on the bellcrank in one place, rather than flopping about, i put a very small alan key through the bellcrank hole (where the elevators pin would normally go through) and taped the alan key to the side of the fin to immobilise the bellcrank. this is not evident in the images above as the tape was on the opposite side of the fin.

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evad

nice going , you should end up with a great repair job at the end of this , I still haven't had chance to test out my repair by chucking off a hill yet .

 

 

dave  

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