Pitts wing fixing

[Jimbo 0]

I have for a while been trying to figure out a quicker method of fixing the centre of the wing to the struts on my Cermark Pitts.

 

The current way of fixing is using 2 x M3 bolts with nylocks to secure the centre ply wing plate to the aluminium cabane struts, and is a little fiddly and slow to assemble in the field.

 

I've come up with an idea, that seems to work, and I'd appreciate any comments from other builders regarding the integrity of the design.

 

I attach some piccies which I think are self explanatory.

 

[Jimbo 0]

And here are the pins and clip on their own.

 

[Darren 0]

Any chance the cabane struts could spread? Side loads on the top wing?

 

How about a spring holding the struts together, pulling each side sandwich like against the ply wing plate filling?

[Jimbo 0]

Well the springs on the steel pegs do that - they hold the whole lot tight together against the retaining piano wire keeper.

 

(I hope)

[Trevor 25]

Jim,

Did this method of wing fixing work okay? I am looking for a way to fix the wings on my Ultimate and I don't fancy having to screw/unscrew a dozen little bolts every time I set it up.

 

Does anyone know a better way to do this?

[Jimbo 0]

In the end I never used it Trevor - I think it probably would have been fine, but because I used cap-head bolts, it wasn't too much trouble to to use nuts in the end.

 

The bolts would certainly have had enough shear strength (the main load from the wing). The issue was always whether the spring would hold the cabanes tightly enough together to stop lateral movement.

 

Blooming Biplanes - the F2B has 26 screws to do up!!!!

[Peter Royall 47]

Well B Taylor has one of these and some kind of engineering degree. Maybe he might lend some comment to your question. Oily.

 

As regards the 26 screws on the F2b I dont know what to do about that either. Just finished covering mine. Need to instal the Laser now, and buy a gun and some roundels, (thinking about painting them on, what you think?). Jim, what did you use to section sand your struts? Theres a lot of them!!!!!!!!!!! Any easy answer?

[Jimbo 0]

I painted mine Oily - I think its a much better finish, despite my lack of skill with a brush! Stephen will tell you that my roundels are not very round, but i think they are more lifelike than stickers. I did use vinyls for the registration lettering.

 

For the interplane struts, I did them by hand I'm afraid. Razor plane, followed by electric sander, followed by hand sander.

 

I'm fitting out the cockpit now - its coming on.

 

Mines got a Laser 100 - what about you?

[Lofty 5]

Hand painted is the way to go Even if its not done as well as a Laser could do them, hand painted just looks better