Yet another molded fus repair - with pics

[Phil.Taylor]

Useful pictorial record of a molded fus repairhttp://kevin-newton......pairs.htmlHe's not letting us into the secret of how to smash it into pieces though Phil.

Edited November 19, 2011 by Phil.Taylor

[Yoyo]

Phil.Taylor said:

He's not letting us into the secret of how to smash it into pieces though

 I've got that bit sorted already... I'm a natural at it, in fact. I'm surprised the Fosa didn't crack at that huge wing joiner hole instead.

[van]

thx for the tip

[knewt]

Hopefully showing the 'carbon stitching' will give people a few options, I've not seen it get much coverage but it's a really good technique in certain circumstances. As to how it happened... Dave Watson sent me a video the other night. If he ever shares it wider I'd be really interested for views on the first flick!KUseful pictorial record of a molded fus repairhttp://kevin-newton......pairs.htmlHe's not letting us into the secret of how to smash it into pieces though Phil.

[Phil.Taylor]

Kev - did you use epoxy or just cyano for the carbon stitching?Phil.

[knewt]

5 min epoxy and a hair dryer works perfectly. K

[Yoyo]

Phil.Taylor said:

Kev - did you use epoxy or just cyano for the carbon stitching?Phil.

Am I right in thinking that you cut the grooves then filled them with tow and CA/epoxy then just sanded them off?

[knewt]

Epoxy. Shave off any excess with a scalpel and thin glass over the top. Lovely. K

[Tony Fu]

Ok, don't want to knock Knewty's repair techniques which is obviously adequate and serviceable but the amount of work and effort to do carbon stitching is almost the same as doing with a far stronger technique: That is to bridge with new material across the whole break. My first ever fuse repairs were with stitching but you only reinforce a small part of the damaged area and that's where each stitch line crosses the break. It doesn't even go through the whole thickness of the fuse and by the time you have flat back you have actually used very little carbon to reinforce the break. It's also not in the best orientation to use the strength of the carbon either. You always, or I did, get stress marks developing later where you stitched. You may as well just chamfer back and laminate over the top. It will give very nearly the same strength especially if you leave a bulge. Pretty repairs where you are trying to stay within the same dimensions of the original need a different technique to bridge the break with as 'near as you can or stronger material' than the original fuse laminate. That needs a good shallow chamfer either side of the break. The break needs to be opened up so that you can insert a support behind the break. This doesn't need to be a especially strong or bonded particularly well either. The strength comes from the top laminate where you bridge the break (and so bond to the exposed part of the support) and the chamfered area either side of the break. The original bond underneath becomes largely redundant. Though if you've done that well it can only contribute to the strength. So the break ends up with a laminate as thick if not thicker than the original fuse. Its stronger of course and you are less likely to have any tears after you've flown it hard and see stress marks under your beautiful paint job from carbon stitching.             

[knewt]

I glassed over the top. The stitching spreads the load across the break and the glass over the top knits it altogether. I've used both methods independently and found that using them together gives the best long tern results for me. Regards  K