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Kyri

F3F repairs

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oipigface

Remember this?

EA7AB1AB-F9E0-4C6C-8EC6-BFEF8CA57281.thumb.jpeg.9db34f0309f3de48c5174f4bcd7c92b1.jpeg

 

This is what it looks like now:B5DB9578-7F83-4050-A51B-75B58AA77C41.thumb.jpeg.9e447d0c7bd946222eccbb2bcfccfb79.jpeg

I’m going to finish it off with clear lacquer before giving myself a chance to break it again. Meanwhile the wings need a bit of TLC as well.

 

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Kyri
4 hours ago, oipigface said:

Meanwhile the wings need a bit of TLC as well.

Whats up with the wings? Just cosmetic? 

I like the finishing quality of that tail after painting, after a clear coat it will look great.

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isoaritfirst

I’ve been painting my Shinto tailplane on and off for the last few days. 

PLeased with it now, but it’s taken a lot of attempts. There is a slight colour mismatch that if I painted all of the top surface would probably not be noticeable. However it has always been my intention with the tailplane  repair to add as little weight as possible  

So paint is patched in and rubbed down to next to nothing.

Imo it’s well worth trying to achieve a finish that has no more paint than is necessary, especially on anything thats behind the c.g. 

My Alliaj fus repair looks great with  a nice top coat and clear laquer but it took a fair amount of added nose weight to compensate for it. Possibly a case  of less is more  

 

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Kyri

An update on the wings. 

One wing (the one with all the wiper repairs) had a crease in it and some delamination of the wing skin. It was not apparent from the outside the extent of this damage.  Normally I would have pin pricked the area and flooded ca through the holes, it seemed a great shame to affect the appearance like that, and also it might not fix a potential spar delamination properly.  

On testing the strength, I found that the spar felt OK. The way I do this is to put the wing half against my lower chest, and with a flat hand on each outer quarter/fifth  of the wing, pull and feel for any irregularities in feel or sound. Whilst this sounds crude, it is a way of spreading force over a large area and being able to stop the application of force if anything is noticed. It is possible to apply a lot of force this way so care must be taken. 

I then tried to twist the wing, and noticed that in the area of the crease, the delamination got worse and I head some sort of creaking sound. The other wing in comparison was much stiffer torsionally. 

At this point I tried angling my phone lens through the servo hatches and then remembered my lidl inspection camera which could be just right for this task of inspecting spars and the inside.

The wing didn't look too bad from the outside. It would have been easy to ignore this based on how it looked.

 

wing skin crease.JPG

wing skin creaae2.JPG

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Kyri

There is a rib inside the wing inbetween the two servo hatches. I managed to get a good look at it, and even do the twist test with the camera inside. there was a crack in it that opened up when twisting the wing. Whilst this rib is not adding much strength if any to the wing, it enabled me to see that the delamination of the lower wing skin needed sorting. 

As for the spars, no issue, as I inched my way along them with the camera whilst doing bending and twisting tests. This was a 5 hand task so I recruited help for it!

 

wing camera.JPG

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Kyri

For the delamination repair, the skins have a foamed material which does not wet easily with ca due to the layer of glass on each side. 

I found a way to get ca in from the top skin through a tiny hole / tear which I opened up and put the needle through. I adapted the needle to the ca bottle with some silicone tubing. As the ca went in I angled the wing to ensure it got through the 6-8 inch distance before setting - which is a while as it doesn't go off straight away when it touches the foamed wing skin material.

The rib crack was repaired with a longer section of silicon tubing which I fed into the wing with the camera - I attached it to the camera about 3-4 inches in front of the lens so I could see where I was applying it. Didn't take a picture of it as I needed to concentrate!

 

wing ca needle adaptor.JPG

wing ca hole.JPG

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isoaritfirst

Move along the bench - 

After a great comp yesterday I did sustain some damage to the Jazz. Annoyed as the landing was close fine, but tussocks are sometimes filled with evil intent.

 

IMG_6585.JPG

IMG_6586.JPG

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isoaritfirst

Tip was hanging off so quickly zapped it back in place when arriving home yesterday.

Not sure how I will end up repairing this, so lets wander "wonder" into this together.

Close visual inspection shows a LE that appears to be carbon tow, and of course its broken and a small part is missing.

Current thoughts are to grind the LE open to allow access into the wing. 

I may then push some epoxy wetted out tows into the space with the intention of creating a TE spar that will run around the area of the aileron cut-out. There is no wing spar at the tip so they should be able to be pushed back far enough.

Once that is dry, stuffing the space with a few separated and dry carbon tows before drizzling with cyano, should give surface strength back as well as some structural strength.

Further tows will be added as the third stage to reform the LE, and tie it into the existing LE material. These will be over-filled and then sanded back to form the profile.

The break line will then need to be smoothed and I will decide then if it needs any level of external patch inserting. I don't expect it will, as the newly formed TE and LE spars should make this area better than original, which seems compromised to me by the aileron cut-out and lack of spar. 

Anyway that's the plan - Although I rarely stick to plans - or even make them - so lets see what comes next.

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isoaritfirst

10D51057-ADDA-4E87-9009-B1F1BFA22B52.thumb.jpeg.cac7ba46189077e56a90e1377e71ce5d.jpeg

opened up a access hole on the bottom skin, just behind LE 

tip is very thin st this point.

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isoaritfirst

Magnum sticks make great pokers after a quick run on the belt sander. 

337C52BC-8CFC-4292-8CCB-61F1C2523349.thumb.jpeg.a18a6eaeb953bbdfff76967295444cd3.jpeg

 

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isoaritfirst

All done, ready to race again. 30 minutes faffing about. 

Repair seems solid, so a small amount of cleaning up and a daub of paint should be good as new. AD39BE33-EB67-4B40-85A3-4E20F8B492B4.thumb.jpeg.f7ebb31acf0595433715c94d9df499b5.jpeg

1A607BE3-676F-4001-9178-3AD8434FC3D4.thumb.jpeg.f00addf415ef7d5854b92b580ef3fc84.jpeg

 

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Kyri

Excellent!!! Noted well for the time when this will be needed. I am even debating re-doing some bad jobs I already did.

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isoaritfirst

Tip tap now back to tip top condition. 

280F8E56-1265-4631-9A2A-FE7423777324.thumb.jpeg.909c15659477f0b16b486c60e4819503.jpeg9A5750C0-A880-4829-9124-72062AA5ADEE.thumb.jpeg.b146c8befbcfedd18abaddc0362aa1f5.jpegc

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isoaritfirst

my thoughts on the repair?!

well I like this keyhole repair technique a lot. 

It light and strong, so everything I want in a repair. 

Add to that it’s quick and easy.

 If you do try, them a few things to consider. 

Wetting our the tows with cyano ,  they don’t dry very easily and will soak up a fair amount of cyano. 

Run it in and leave it for 5 minutes, but make sure during this time that the cyano stays where it needs to. 

I propped the wing and moved it around a little in an appropriate manner to ensure it didn’t run into the wipers or hinges. 

Once you are happy with the carbon tows having had time to get “wet” and you want to start working on the wing again , hit it all with small amounts of activator. Gently at first. As lots of activator May mean lots of heat and cyano that is  crystallised rather than dried. 

 

 

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oipigface
On 07/02/2019 at 16:50, oipigface said:

Remember this?

EA7AB1AB-F9E0-4C6C-8EC6-BFEF8CA57281.thumb.jpeg.9db34f0309f3de48c5174f4bcd7c92b1.jpeg

 

This is what it looks like now:B5DB9578-7F83-4050-A51B-75B58AA77C41.thumb.jpeg.9e447d0c7bd946222eccbb2bcfccfb79.jpeg

I’m going to finish it off with clear lacquer before giving myself a chance to break it again. Meanwhile the wings need a bit of TLC as well.

 

.... and now it is all done. Wings are coming along, too. There were a couple of repairs that I didn’t have time to paint, that I’ve been giving the wet and dry treatment.

42766E4B-340C-47C5-B7C6-7ED338419EBF.thumb.jpeg.738bb4cba1682655d751a68aa7c49768.jpeg

Come to think of it, this is the first repair I’ve ever managed to finish right down to the lacquer, 600, 1000, 1200, 4000 and car polish. It looks better than it did when it was lashed up with glass reinforced tape.

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Kyri

This thread has ended up with lots of everyone's excellent techniques for repairs. Great!!

In the meantime the needle is restored, I have taped the flap wipers to protect them from damage (as I already learnt that).

I am very proud to have had the chance to get this one air worthy again. Can't wait to get it flying.  I will call it the TN124.

 

st needle 1.JPG

st needle 2.JPG

st needle 3.JPG

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oipigface

Looks as if it might once have belonged to simon_t!

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Scram
On 22/02/2019 at 16:55, isoaritfirst said:

Run it in and leave it for 5 minutes, but make sure during this time that the cyano stays where it needs to. 

I propped the wing and moved it around a little in an appropriate manner to ensure it didn’t run into the wipers or hinges.

That thin cyano is terrible stuff for getting into the wrong places and gluing what you don't want glued - like my trousers to my leg or worse, my servo wiring harness to the spar!!

Couldn't get the servo out  :frantics:

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isoaritfirst

Yep, runny is the attribute you need.

Allows it to run into all the nooks and crannies.

You do need to be careful, gauge how much your putting in and understand where it may get to if you don't hold things at appropriate angles, 

Then Kick it before you do start moving around to make sure the remains are all frozen.

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Kyri
On 03/03/2019 at 16:20, oipigface said:

Looks as if it might once have belonged to simon_t!

Indeed, and this model has quite some history:

 

st needle 4.JPG

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