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Scram

Aresti fuselage repair

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Scram

Having made the same pilot error mistake twice, resulted in a snapped fuselage for my Aresti, just behind the wing but no other significant damage.  How to repair without having made a fuselage jig before breaking it, was the question??

I thought for a long time about this.  I’ve tried holding a fuse together waiting for epoxy to set but this does not result in a straight join !!??  The fuselage is very oval, tapered at the break and deep at the front making a vertical setting even more difficult.  I decided an internal sleeve would be needed and something to align the joint.

First I measured the fuse up and down from the break and using Excel, drew some oval figures representing the inside section, front and back of the break.  I used these to carve two blocks of wood which fit inside the fuse at top and bottom of the break.  There’s a snake for the rudder which needed replacing as the sleeve was kinked and the carbon rod broken.  I cut the sleeve back as far as possible and installed a replacement in the rear fuse, long enough to come to the servo position.

How to align the fuselage halves?  I needed a flat surface, so used an old jig frame.  I measured across the wing seats (38mm) and the tail plane seats (19mm), reckoning these should be parallel.  So I then cut a piece of wood half of 19mm thick.  I drilled a 6mm diameter hole vertically into the jig frame (using a drill stand) and mounted the front fuse half to the jig frame and with a 6mm carbon rod through the wing incidence pin holes and into the hole so ensuring the seat was flat on the board and all aligned vertically.  I used a large screw through the other incidence pin holes to pull the seat flat and to secure things. 

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Then another 6mm hole went vertically through the 9.5mm thick piece of wood and with more 6mm rod I was able to align the front half to the back half of the fuse.

I moulded 2 pieces of internal sleeve from 2 layers of 200g/m2 carbon with laminating epoxy, peel ply, tissue and polythene as the picture

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 and glued the 2 pieces into the front fuse section with ordinary epoxy – mistake! 

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When this was set I applied epoxy to the sleeve and back half, fed the snake into position, located the front and back sections on the jig frame and pushed them together.  The rods and wing joiner are sufficiently well aligned for my liking and it looks straight from the bottom too  J

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 Left it over night to harden and in the morning it all looked great,

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 I put the fus down in the sunshine and that’s when my mistake became apparent.

In the warm morning sunshine of my hobby room the unsupported rear section drooped due to the 20min epoxy softening.  Reckon I should have used some 24h Araldite or maybe thickened laminating epoxy would be less affected by the warmth.  Solved this problem by warming the joint more with a heat gun, pushing the joint together again and replacing everything on the jig frame – OUT of the sunshine.  Keeping it normal room temp seems to be OK.

So, then scarfed back the joint for external carbon/glass/carbon laminations with curved pieces to fit round the taper properly. 

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Laminating epoxy applied with the fabric layers followed by peel ply, tissue and foam all wrapped tightly with making tape.

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 Unwrapped the next day when cured to find some of the outer layer of light carbon seemed to be de-laminated a bit so I soaked it all with thin cyano before applying P38 filler.

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Rubbed this back before applying several coats of primer rubbed back between coats.  Some pin-holes remain but I will live with that.

I debated whether to try to match the yellow or just do a contrasting white finish.  I got some yellow but not sure yet how well it matches.  To be seen......

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Brett82

Very nicely done Jerry. :yes:

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Walter A

Well done and brilliant! Thank you for sharing!

V/R,

Wally

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Andy_B

I can see where my next broken fuz is going .................:)

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czorzella

Very well done, Jerry!

I hope I don't ever have to use it, but if I need, the information you've provided will be valuable.

Carlos

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Phil.Taylor

nicely done Jerry !

good "heads up" on not using soft fast epoxy where solid alignment is important

Phil.

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Scram
2 hours ago, czorzella said:

Very well done, Jerry!

I hope I don't ever have to use it, but if I need, the information you've provided will be valuable.

Carlos

Thanks for all the kind comments.  This was one reason for my posting.

Now, slowly, to fix 3 more fuselages  :frantics:

The yellow colour turned out to be a poor match so it is going to be a white cover-up as there is white on the wings  :thumbsup:

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Jef Ott

Excellent job. Brilliantly written. Thanks for sharing here.

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Scram

Thanks Jef.

Not quite the end of the saga.  I finish painted the joint in white, looks OK I think having the white areas on the wings:

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Then I had a problem with the electric.  See post in RC Equipment - now solved, I think.

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stewartg

Might look even better with a red band behind it then a yellow gap and a black band....

just a thought.

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