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isoaritfirst

AlliaJ (slim) fuselage repair

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isoaritfirst

Some of you may recall I chucked my AlliaJ off the hill without switching it on a few months ago. 

Amongst other small works the fuselage was snapped clean in two and the wing joiner broke through the top of the fuselage. 

 

 

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isoaritfirst

After stripping out the servo tray and ballast tube, the two fuselage halves were joined initially with a carbon patch on the outside. 

Fusekage was sanded heavily after tacking it together with cyano. Removing a lot of the original carbon close to the break. 

To appply the carbon  first I put a layer of clear tape on the one side of it and cut the shape needed with the scissors. Poured on slightly warmed epoxy left for 5 minuted then blotted it all off on some newspaper. 

One on the fuselage I wrapped it in a poly bag and squeezed and rubbed it every half hour or so  for the next 3 hours. This seems to work a little like vac bagging. 

Then I taped it with a few pieces of balsa strategically positioned to hold the shape of the fuselage under the wing seat. 

End result was very good. Hardly noticeable and felt pretty strong. 

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isoaritfirst

But I still had no bridge across the top of the wing joiner opening. 

And also while I could gain acces through this hole i took the opportunity to put another layer of carbon across the inside of the fuselage break. 

A old inner tube cut and knotted to length in the fuselage applied the pressure. 

 

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isoaritfirst

AFB43B0C-6DFC-4C56-BE89-11914ACC0915.thumb.jpeg.11f791ea1a4d1574ee31f487c5558901.jpeg

then I had to remake the top of the fuselage. 

So far it’s looking good I’ll post some more later

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isoaritfirst

Third piece of carbon runs from fuselage sides and up and over the   Wing joiner position. Remaking the fuselage top. 

Again using a bladder and a piece of ply to hold the carbon to shape. 

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isoaritfirst

Tape on the ends of the bladder to prevent it expanding in the front area of the fuselage. Wire to pull it through the fus to get it nicely positioned. 

Took a few attempts as first bladders burst. Made this one from a mtb tube. Much thicker. 

But it wouldn’t hold the pressure for long. The ends were simply knotted. 

Eventually I poured in some Stans tyre sealant. That fixed the leaks a treat. 

1EA95878-744B-47FA-B309-608C0C8BB8CD.jpeg

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isoaritfirst

Bit of sanding now and a fourth piece of carbon over the top and sides. Then cut the joiner hole back. Should see it done before reshaping the wing seats. 

Originals were made from epoxy micro balloon mix. 

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Brett82

Very nice Mike, thanks for the tips. May come in handy in the future. 

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satinet

I've got a model that's a prime candidate for the fuse popping off above the joiner hole. Thin!

 I'll make a fuse mould before i fly it. Should do it with all mouldies really 

Guess one shouldn't crash but it l does happen.

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isoaritfirst

So far the repairs after stripping out have taken perhaps a hour for each piece of cloth, Most of that time was faffing about trying to mak ethe inner tube work.

So top tip;

- Use a MTB tube or place a cut piece of tube over the original doubling the thickness.

-Make sure any areas where the tube can over expand are taped in or blocked to stop the tube puffing out and exploding.

-Use something to pull or push the un-inflated tube into place. (this was easy with the Alliaj. The wire reached out of the tail end of the fuselage, stretching the tube to a thinner section while pulling it through the fuselage stops it dragging the cloth out of place.

- Make sure the tube doesn't leak! Knotted ends worked fine in a road bike tube but in the thicker mtb one they leaked.

- If all else fails and you have some latex glue or - Stans (brand name) Tyre sealant stick some in. worked great for me.

- Consider how the expansion will effect the shape you want. In the Alliaj I left it so that tape help the cloth roughly in place as it expanded out through the joiner holes. This gave a better fix than if I had blocked it so that it couldn't push through slightly. It shows in the pics. Simple sanding will open up the joiner hole again.

 

Rebuilding the wing seat may be a faff. I left the seat intack at each end of its line to help with the positioning etc. I guess I will simply make it bigger and sand back. Making a mould to suit may just be a little trickier than I fancy.

 

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isoaritfirst
5 hours ago, satinet said:

I've got a model that's a prime candidate for the fuse popping off above the joiner hole. Thin!

 I'll make a fuse mould before i fly it. Should do it with all mouldies really 

Guess one shouldn't crash but it l does happen.

The AlliaJ original construction is a Carbon tube, The joiner cut through and the wing seats created in a mould out of epoxy and micro ballons. A mould would make that reforming a lot easier. Thinking about it I could take a mould off my old (fatter and now electrified) AlliaJ Fus. Roots are of course the same.

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isoaritfirst

F134A596-0985-4915-9D60-CAA986A24124.thumb.jpeg.8d857cc992835d167af9c91355ac496d.jpeg

this top carbon piece was actually two pieces of carbon with the weave cut on the biase on the one. 

Put in from underside you can see how the bladder has puffed to the ply piece I taped across the top, making the top piece sit nicely in line with the older pieces. There is plenty of room to add a third layer right across the top on the outside 

4B91CFC8-2A69-435A-BFFB-7A5E6E6A49C4.thumb.jpeg.7c23bb680a360af95d3992d5d9010234.jpeg

the external carbon wrap around the lower section of the fuselage looks and feels like it was actually bagged. Done by squeezing the air and epoxy out of the cloth while it sat in place inside a polythene wrap. 

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isoaritfirst

There are of course many ways to skin a cat. 

Part of the reason for posting this repair log was to simplify the methods that can be used. 

Basically all you need is some cloth and epoxy resin, sanding stick, tape and cyano   

Vac bags etc may be nice but don’t think you can’t do these repairs without all the tools. 

Think - Soft heat and pressure 

- decent cloth of a suitable grade (same as original if possible) and a little problem solving as you go. 

All pretty simple stuff, that is best learnt on the hoof. 

Get stuck in. 

If you do get stuck then of course ask for help, but don’t get too bogged down with multitude of solutions offered. Use what you have and techniques you can handle. 

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isoaritfirst

Another hour spent last night on building the bridge over the wing joiner. 

A hard foam piece was made to match the size of the joiner and wrapped in clear tape and taped in place. 

Carbon tows run along the top edges to form smoother edges and add extra strength. 

Two pieces of carbon, first smaller piece cut on biase, then second piece cut to wrap around and finish at bottom of wing seat area. 

All poly bagged and rubbed and taped to apply pressure over night. 

Left on a warm place to cure

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isoaritfirst

Unwrapped this morning and broke out the foam joiner. 

Light sanding and it’s looking pretty good. 

Chuffed I am😊

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isoaritfirst

Always a leap in the dark.  

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isoaritfirst

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isoaritfirst

Started the wing seat. 

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isoaritfirst

image.thumb.jpg.d33867101734a87e1d54c3c1a3ca8520.jpg

first side now unwrapped and second side setting. 

Foam inserts in the joiner and electrical socket points. These had to protrude out of the carbon shell to hit side shutting. 

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isoaritfirst

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