Wing joiner blades

[GordonT]

I need some flat steel wing joiner strip for a motor glider that I've recently bought. As close as I can measure, the brass box into which it slides is 14mm x 2mm. I can find 15 x 2mm steel strip, but does anyone know where I might find some 14 x 2mm? Thanks!

[B Sharp]

How much do you need.
Brian.

[GordonT]

Brian - it needs to be 60cm long.

Richard - That size isn't showing on the Gliders website, but I'll give them a call later today.

I also found them listed at Leeds Model Shop, but stock level is unclear, so will give them a call today, as well.

Thanks for the help chaps - appreciated.

Gordon

[B Sharp]

Sorry Gordon, I don't have a piece (of-cut) that is as long as 60cm. The longest 14mm I have is 20cm, but I do have a 42cm length of 15mm which has been ground down to 14cm.
Brian.

[GordonT]

Thanks for looking Brian.

Gliders do have plenty of the 14mm x 2mm strip, but they aren't buying it any more as they say it's a very tight fit in the available tube. However, that's probably what was used originally, so I'll buy a length of that and see if it can be persuaded to fit.

[B Sharp]

I think you will find that Gliders 14mm strip is not the original Graupner strip, but is slightly bigger and has been run through a grinder on one edge. It can be made to fit with a little further grinding on the edge and then rubbing down with emery cloth, but it will always be a slightly stiff fit. (I used it on the joiners for my Dart)
Brian.

[GordonT]

Brian - OK, thanks for that info. I'll order a couple of lengths from Gliders and then do what I have to in order to make it fit.
The good news is that I just received an email from the seller with a photo what appears to be the original joiner - I'll collect it next week.

[LapseRate]

I have got some spare 12mm Graupner Outer brass boxing. I also have some 10mm x 1mm lengths of Carbon Fibre flat strip which fits it
beautifully. I think I can use this in place of the original metal strip (with a weight saving) for wing joiners. Does anyone have experience to say this is unwise or a no-no....????.........Paul

[Simon WS]

Sounds dangerous to me Paul!
The carbon fibre will let go without any warning and in that application and orientation is just asking to be nicked or flexed in the wrong direction giving rise to stress concentration factors.
Carbon fibre is a wonderful material but IMHO it has to be used with careful consideration of it's properties and design. Yes I know they are used in F3F gliders but they are relatively massive joiners and have been carefully designed.

Regards

Simon

[B Sharp]

I totally agree with Simon, on the carbon in this case. If you do over stress the joiner, a steel joiner will bend but you will still be able to land with excess dihedral, the carbon just lets go and you will lose the wing. I would definitely stick with the steel in this case, even if it means a bit more work.
Brian.