Help! A fold or mitre joint?

[entozoon]

Hello all,
I was wondering, out of curiosity more than anything, is there a structural benefit to using the A and B fold techniques rather than a mitre joint?

Obviously mitres are more difficult in a way, but with a 45 degree cutter it could be a doddle. Easier in fact, without having to pluck out the middle foam.

Just a thought.

 

[Hai-Lee]

It is done for simplicity but it does also have an added structural benefit compared to a mitre joint.

Firstly the surface area which is covered in the glue is 30% less in a mitre joint.

The FB edges are stronger when square cut as the paper on the inside provides a considerable portion of the strength of the joint. Remove the paper and the resistance to warping and impact damage will be weakened.

If you have the means try a few builds using the mitre and standard methods and the answer to your question will soon be obvious.

I have even started to use the "A" and "B" fold joints on my wing Leading edges and the strength of the wings and their impact resistance have improved out of sight!

Just my experience!

Have fun!

 

[spdcm]

Thanks for the Tip Hai-Lee on the Wing, I want to try it on my new build.

 

[DamoRC]

I have even started to use the "A" and "B" fold joints on my wing Leading edges and the strength of the wings and their impact resistance have improved out of sight!

Any pics of how you do this?

Thanks

DamoRC

 

[Hai-Lee]

Any pics of how you do this?

Thanks

DamoRC

Here is the post I did a little while ago about the way I do my LEs now. https://forum.flitetest.com/index.php?threads/do-you-have-issues-folding-up-a-fb-wing.54866/

The only change in the plans required is to extend the underwing panel by the thickness of the FB itself.

Now I just cut a channel in the LE of the underwing panel the same thickness as the FB and then bevel the foam on the underwing panel.

When folding up the wing I fold the wing upper panel LE into the channel, (with glue), and then fold and glue the wing lower panel.

The result is strong and simple to paint if required. Additionally it is simple to add an external shaped balsa or similar LE if needed. As there is no severe foam crush the fold forces are equal across the entire wing LE and so I get very uniform results even when doing 20+ of the same wing in a batch! Very suitable for the use with liquid glues and a wing shape and drying jig!

In addition as there is no tape reinforcing added I can paint freely and add reinforcing tape if required as the last step of the build.

Just what works for me!

have fun!

 

[entozoon]

That's wonderfully informative, thank you very much @Hai-Lee