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evad

smashed my typhoon help and ideas needed

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oipigface

 also can someone recommend a good release agent to use on the wing joiner ?

 

I use Alchemie R5, which is excellent. Unfortunately, I don't know any reasonable way to get it other than to buy a case or two from their premises near Coventry, and then sell the cans you can't use to your friends. Their postal charges are astronomic. If I had any to spare I would find a way to get a can to you, but I'm down to my last can, and won't be making a trip to Coventry until it's empty. Vaseline is not a bad idea, but it is messy.  www.alchemie.com

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Tilman Baumann

R5 is the ducks guts. And cheap.

Stay away from PVA unless you really know what you do.

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evad

right , if you have smashed your typhoon fuse in two pieces, it is possible to replace the elevator push rod if your stubborn enough to try anything after failing to repair the broken rod without removing it from the airframe, here is the technique that can be used ,

1, unscrew the damaged remains of said push rod , leaving the clevis attached to the bell-crank inside

2, make up a new pushrod using 4mm carbon tube with a threaded rod suck out the end

3, find something that fits in the hole in the bell-crank where the tailplane fits through to hold it still

4, lay on the living room floor with the tail section pointing up at the ceiling light holding the rudder over so the light shines through into the boom, the clevis should now be hanging down towards you  

5, insert pushrod and locate the clevis end then simply screw in the new pushrod and job done !!   

 

dave 

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evad

guys , I have gone through all your replies and come up with a idea on how I'm going to tackle this repair , please step in and stop me if I'm going the wrong way with this , its looking like it will work as the dry fit shows so far anyhow .

 

the kit of parts , angle iron , cheep plastic set squares , carbon rod and some luck

a donated piece of glass cut from a old nose cone

rolled up and inserted as a splint to help hold things straight

both parts are now pushed together and glued 

using carbon rod passed through the wing peg holes 

and the holes in the tail 

every thing levelled and taped to the angle iron to keep it straight until the glue dries

what the joint looks like when all pushed together 

 

 

once this stage is completed ,the plan is to wrap the outside of the fuselage with a couple of layers of carbon cloth and just go over the whole damaged area extending past around 30/40mm each side 

 

what do you think guys ? will this work ?

 

thanks dave 

 

 

 

 

 

 

 

..

 

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isoaritfirst

Looks like a plan.

Sand everything well to remove any gel coats. 

Tack it all in place with cyano while squared up, then take it off the board and eyeball it.

 

You should then be able to work with it in your hand while you sand it all back to a nice thin feather joint before re-wrapping with new cloth. 

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pete beadle

Hi Evad

 

What Mike is saying is VERY important - there must be NO shiny bits on the tube you're inserting into the fuselage as no adhesive adheres positively to the polished surface of the shiny fuselage skin

Also, your insert will help to spread the load either side of the break

Unfortunately those RCRCM fuselages are just too lightly built, when I broke my "Sigma" I repaired it as you are suggesting. but it just broke further down from the first fus join when I landed it just SLIGHTLY heavily

If you hold fuselages like those made by Jaro Muller in your hands you can see straight away how it should be done

Good luck

 

Pete

BARCS1702 

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oipigface

What Pete Beadle says is right, but there are things you can do to reduce the likelihood of creating a stress point in your repair. Firstly, taper out the edges of your infill, so that the internal surface is a shallow V shape. The edges should taper down to almost nothing. Next, when you are shaping the outside, try to make that V-shaped too. What Mike says about getting rid of the shine is true, but you should also aim at creating a V-shaped ring around the fuselage (not cutting into the infill, of course), that you then can fill with as many layers of carbon cloth and slow-setting (laminating) epoxy as it takes. I usually put some tows in to begin with because the V is narrow at the bottom, and cutting narrow strips of carbon cloth is hard.

You can usually do this all in one operation. Make sure that the strips of carbon cloth are wetted thoroughly as you add them, and make them as tight as you can. When it looks as if you've enough to fill the ring, put peel ply around as tightly as possible, followed by some of that woolly stuff that absorbs epoxy. Tape around as tightly as you can. Leave in hot box or airing cupboard for 3 or 4 hours. By then the epoxy won't flow any more, but the peel ply will be easier to remove than if you leave it to cure fully.

Looks like a good job so far!

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isoaritfirst

All good stuff.

In an earlier post I suggested using a technique I have used on many occasions of bandaging the repair area with a 10mm wide strip of wetted out cloth. Wind it around the repair area like you may wind insulation tape. one wrap around the ends and several over the break. 

Dead easy to do, and it will create that stress relieving repair .

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evad

thanks again guys , all your replies are fully appreciated I'm getting loads more help than I had expected so thanks again , If I get some time tomorrow evening I'll start the repair , it will most probably take me some time to complete this , I have 200g carbon mat is this going to be ok for the rap around the outside ? also finding some peel ply is next on the to do list  

 

 

dave 

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Skip

Kitchen roll/paper towel also does the trick very well. not sure which is actually cheaper, but paper roll is more easily accessible.

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Jon_F

It's worth trying to make the inner joiner tube as light and as strong as possible in order to reduce the amount of additional lead you may need to add up front to rebalance after the repair. Using peel ply as described above you can make a slightly oversized tube from carbon cloth which is very light if you can remove any excess resin ( see image below ). Peel ply also leaves a roughened texture to bond to. Slit the tube so that when you insert it into the fuselage it exerts some natural outwards pressure  or springiness. Once the inner tube has been bonded in, grind back the edges of the damage to feather out the area where you want to bond in the carbon tow and cloth as others have described above.

 

 

 

 

 

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isoaritfirst

Personally I prefer to use light glass cloth and add a few layers in the way I described. The fuselage is glass at the moment and IMO best left that way.

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Tilman Baumann

There is some wisdom to that. Glas fuselages are flexible and carbon is brittle. You can't mix that easily.

But the fact is also that this stint is a weak point by design. Choosing a hard material will make it easier to keep the connection strong. Even though you get stresses between the materials.

I doubt you would even with glass succeed in building the fix with the same bending module.

 

If you happen to have carbon, I don't think there is much harm in it.

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isoaritfirst

My own Sigma, Vector  my Typhoon  were all never subjected to fuselage breaks and are all constructed rather well. 

I did see a few others though which did have noticeably weaker fuselages particularly just behind the wing root.

 

But when it is repaired you should remember that X tail fuselages carry some level of mass on the back end and any whipping landing will often see the tail flick around breaking the fuselage. 

 

Land straight even if its a bit faster and nose in to heather etc. 

Any wing strike is very bad news for models with heavy back ends. 

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evad

the first stage is completed and I'm more than happy with the results , I sanded the paint right off the inner part and put every thing back in my jig , once I had checked every thing for level and looking straight, it was glued up and left to dry over night just , the results are better than i had expected , and it is a complete fuselage again , it does have a few pieces missing but i have stuck all the pieces i had back in place

 

a couple of shots of the repair so far

 

left side 

 

right side 

 

under side 

 

  

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Rob Thomson

Looking good.

 

I am in the process of undertaking a similar set of repairs to a big 3m moulded f3b model.

 

Stupidly launched with the elevator on the all moving tail not pegged into the bellcrank, but resting on top!!

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evad

its now setting up on the top of the radiator , I sanded the whole area down to the fibreglass and then for 20 or 30mm each side of that sanded the shine off the paint , cut two strips of the carbon cloth around 15mm wide and wrapped around the cracked area first strip left to right then the second strip from right to left so they overlapped each other , then over the top of those a piece around 80mm wide that covers the whole lot and wraps around the fuse , then wrapped the whole area in electrical tape to hold things tight , I looked into using peel ply as recommended,  but the cost was to much for the amount I had to buy for this small repair .

 

I'm hoping that I got it right that I take the tape off after a few hours before the whole thing sets up fully.

 

will post the results up once its unwrapped 

 

cheers dave 

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evad

Really? £3.50 for 1m x 1.5m - will last you many years doing small repairs like this.

http://www.easycomposites.co.uk/products/vacuum-bagging/peel-ply.aspx

with a minimum order of 5 meters and delivery of £5.50 = £23.00 add on to that 5 meters of the breather cloth stuff at £1.50 per meter that adds up to £30.50 its starting to get expensive then . 

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